Gprs Qos and Parameters_alcatel

© Alcatel University - 8AS 90200 0409 VH ZZA Ed.05 Page 1.1

© Alcatel University - 8AS 90200 0409 VH ZZA Ed.051.1

INTRODUCTION

TO

GPRS QOS AND PARAMETERS DESCRIPTION

RELEASE B7



1. Principles

▼Training objective: Describe the main GPRS mechanisms and concepts of GPRS


1.3

1 PrinciplesSession Presentation

▼ Objective: Describe the main GPRSmechanisms and concepts of GPRS

▼ program:� 1.1 Service overview� 1.2 General architecture & protocol layers� 1.3 Alcatel GPRS architecture� 1.4 GPRS channels� 1.5 Main transactions� 1.6 Other concepts and definitions

▼Sub-chapters are not displayed on this slide



1 Principles

1.1 Service overview


1.5

1.1 Service overviewData transfer with GSM: circuit switching

Internet

GSM

network

Air interfaceAccess node

▼Circuit switching: �transaction is offered in connected mode�allocation of a continuous radio resource UL/DL until the completion of the transfer�One circuit = channel is allocated per user�The traffic multiplexing is achieved inside de BSS, over the Ater interface

▼HSCSD: High Speed for Circuit Switching Data�Technology that allows the multi-slot allocation to one user�Important throughput can be achieved (up to 64 Kbit/s constant) but there is no optimization of the use of the channel �(no dynamic allocation when data services are mainly carried in a bursty mode)�The billing is time based like in GSM�Is likely to lead to important congestion situation�Not offered by Alcatel


1.6

1.1 Service overviewData transfer with GPRS: packet switching

GPRS

networkInternet

Air interface

▼GPRS provides end-to-end packet-switched data transmission between MS users and fixed packet data networks▼GPRS is a GSM feature▼GPRS provides efficient utilization of the radio resources:

�Multi-slot operation�flexible sharing of radio resources between MS�resources are allocated only when data are transmitted

▼Charging is based on data volume transmitted, not on connection time


1.7

1.1 Service overviewMS classes

▼ Three MS classes are defined:

� class A:

� simultaneous GPRS and GSM traffic

� class B:

� simultaneous GPRS and GSM attach but not simultaneous traffic

� an MS can be paged for a GSM call while performing a GPRS transfer

� class C:

� either GPRS or GSM attach

▼Do not get confused with the multi-slot class of MS, or MS capacity, which characterizes the number of TS one MS can monitor in UL and DL simultaneously.▼For the detail of the MS multi-slot class, please refer to APPENDIX 1

▼The main traffic class available on the market is Class B. Class C is preferred for PDA devices when Class A is not popular in the phone industry: it introduce mobility management issues that will be reviewed in the chapter 2, “cell selection and reselection”.



1 Principles

1.2 General architecture & protocol layers


1.9

1.2 General architecture & protocol layersGeneral GPRS architecture

▼ GPRS general architecture:

BSS

GPRSIP BackboneGb

MSC / VLRA PSTN

PDN X25

PDN IPGi

Circuit switched services

Packet switched services

▼The BSS is used for both circuit-switched and GPRS services▼A GPRS core network (also called GSS, an IP backbone) offers the inter-connection between the PDN and the BSS▼The BSS has 2 clients:

�the MSC, for circuit-switched services (through the A interface)�the GPRS backbone network, for Packet switching services (through the Gb interface)

▼The A interface is unchanged


1.10

1.2 General architecture & protocol layersGPRS backbone

▼ GPRS backbone architecture:

BSS

PDN

BSS

SGSN

IP based GPRS backbone

SGSN

GGSN

PDNGGSN

PDNHLR AuC

Gb

Gn

GiGr

DNSNTP

DHCP

▼The GPRS backbone is an IP network composed of:�Serving GPRS Support Node (SGSN)

�at the same hierarchical level as the MSC�linked to several BSS�performs security and access control functions�performs GPRS Mobility Management for attached MS�performs Session Management for attached MS

�Gateway GPRS Support Node (GGSN)�linked to one or several external data networks�provides inter-working with external packet-switched networks�connected with SGSN via an IP-based GPRS backbone network

�Both GSN have IP routing functions and telecom functions.�IP servers “of the shelve”:

�Domain Name Server�Network Time Protocol Server�Dynamic Host Configuration Protocol Server


1.11

1.2 General architecture & protocol layersTransmission plane

▼ Transmission plane

MAC

GSM-RF

LLC

RLC

IP/X25

SNDCP

application

MS

MAC

GSM-RF

UmBSS

RLC

relay

BSSGP

NS

L1bis

NS

L1bis

BSSGP

Gb

LLC

SGSN

SNDCP GTP

L2

L1

IP

UDP/TCP

relay

L2

L1

IP

UDP/TCP

GTP

GGSN

IP/X25

Gn

Chapters 1 and 2 Chapter 3

▼Transmission plane:�layered protocol structure providing user information transfer and associated control procedures�GSM-RF: physical layer

�radio link measurements, cell re/selection, power control, …�MAC: Medium Access Control

�defines the procedures that enable multiple MS to share a common transmission medium which can consist of several physical channels

�RLC: Radio Link Control�defines the procedures for a selective re-transmission of unsuccessfully delivered RLC data block�defines the procedures for segmentation and re-assembly of LLC PDU

�LLC: Logical Link Control�provides a reliable logical link independent of the underlying radio interface protocols

�BSSGP: BSS Gprs Protocol�Defines the signaling procedures between the GSS and the BSS�Carries the LLC frames to be routed between MS and SGSN�Refer the the chapter 2 “Gb Interface” for further details

▼The MS attach to the network (SGSN) which allocates temporary identity (TLLI < LLC) used for signaling and user data▼When the MS is attached, it can connect to an external network (PDN) by activation of a session (PDP context)▼For multimedia purposes, several sessions can be allocated simultaneously: a session number is therefore allocated to each session (NSAPI) thanks to the SNDCP layer▼This session MS-SGSN is relayed in the GSS by a tunnel (GTP protocol) which is uniquely identified by a Tunnel ID (NSAPI+IMSI)▼To route information towards the MS, the GGSN needs an MS IP address▼LLC frames are segmented into RLC blocks to be transferred through the BSS after being conveyed by a BSSGP frame over the Gb interface (simple encapsulation with BSS routing information)


1.12

1.2 General architecture & protocol layersSignaling plane

▼ Signaling plane

MAC

GSM-RF

LLC

RLC

GMM/SM

MS

MAC

GSM-RF

UmBSS

RLC

relay

BSSGP

NS

L1bis

NS

L1bis

BSSGP

Gb

LLC

SGSN

GMM/SM GTP

L2

L1

IP

UDP

relay

L2

L1

IP

UDP

GTP

GGSN

Gn

▼Signaling plane:�provides protocols for control and support of the transmission plane functions �GMM/SM: GPRS Mobility Management/Session Management

�GPRS attach, GPRS detach, RA update, PDP context de/activation

▼It is to be stressed that the GSS signaling and the GSS traffic are carried through the BSS with the same protocols, so transparently

▼NB: this is the same protocol layer inside the BSS (i.e. GSS signaling or traffic is carried the same way through the BSS) except for GMM and SM



1 Principles

1.3 Alcatel GPRS architecture


1.14

1.3 Alcatel GPRS architecturePCU function

▼ A Packet Control Unit is defined by the GSM standard:

� handles RLC/MAC functions

� can be either in the BTS, the BSC or the SGSN

� Alcatel choice:

�PCU in a new network element called the MFS� smooth and cost effective introduction of the GPRS

BTS

BTS

BSC

BSC

MFS SGSN

Gb

Ater

▼The standard specifies that the PCU function must be implemented in one of the 3 following entities:�-BTS,�-BSC,�-after the BSC (in the SGSN for instance)

▼The implementation of the PCU functions determines the position of the Gb interface.

▼ALCATEL chose the MFS integration in order to offer a faster implementation inside the BSS as well as an easier maintenance and supervision


1.15

1.3 Alcatel GPRS architectureGSL, GCH

SGSN

Radio interface

GCH

GSL

BSC

CCU

CCU

BTS

Abis GbAter

MFS

PCURadio Res. management

Gbprot.stack

RSL

▼GCH: the multiplexing capacity of the GCH link on the Ater belongs to the granularity chosen. 1 ATer TS GPRS dedicated = 1 GCH when allocated▼Traffic TS can be used 12.5% or 25% or 50% or 75% or 100% for GPRS

▼The establishment of the GCH results from signaling exchanges between MFS and BSC over the GSL. 2 GSLs per BSC must be dedicated to the signaling between MFS and BSC to carry the BSCGP signaling procedures. These exchanges take place at allocation/de-allocation of of GPRS radio resource.

▼The use of RSL is necessary as some GPRS originated signaling must be carried over CCCH, before establishment of PDCH (PCH, AGCH).


1.16

1.3 Alcatel GPRS architectureTransmission plane

▼ Transmission plane

MAC

GSM-RF

LLC

RLC

IP/X25

SNDCP

application

MS

MAC

UmMFS

RLC

relay

BSSGP

NS

L1bis

NS

L1bis

BSSGP

Gb

LLC

SGSN

SNDCP GTP

L2

L1

IP

UDP/TCP

relay

GSM-RFrelay

Abis/Ater

L1-GCH

L2-GCH

L1-GCHL2-GCH

BTS

Air In

terfa

ce tra

ces

GC

H tra

ces

Gb

trace

s

▼For the exact purposes of the tracing, please refer to QoS part.

▼It can be said from this protocol stacks diagram that after allocation of a GCH by the BSC to the MFS, the data carried over the GCH are transparent for the BSC.

▼The use of the traces will be reviewed in the last chapter of the training: “GPRS QoS Principles”▼NB: the GCH traces are in fact RLC/MAC information that being traced over the Abis or Ater interface.

▼The most reliable view of the overall GPRS QoS is the MS one as per the protocol stack included inside the MS.

▼The RLC/MAC header is used for MS and TS multiplexing.▼RLC main functions = segmentation, assembly of LLC frames + data transfer mode (ACK, NACK)▼MAC main function = radio resource multiplexing (multi-slot for one MS, multi MS on 1 TS in UL)


1.17

1.3 Alcatel GPRS architectureSignaling plane

▼ Signaling plane with CCCH usage

GSM-RF

LLC

GMM/SM

MS

BSCGP

UmMFS

RRM

relay

BSSGP

NS

L1bis

Gb

GSM-RFrelay

Abis

L1-GSL

L2-GSL

L1-RSLL2-RSL

BTS

L1-GSL

L2-GSL

Ater

L1-RSL

L2-RSL

relay

RR BSCGP

RR/RRM

BSC

▼2 GSL at 64Kbit/s per BSS▼RSL: refer to dimensioning rules for GSM



1 Principles

1.4 GPRS channels


1.19

1.4 GPRS Channels GPRS Physical Channel, PDCH

▼ PDCH (Packet Data Channel):physical channel which carries GPRS logical channels

0 7 0 7 0 7

1 TDMA frame = 4.615 ms

0 1 2 49 50 51

The 52 multi-frame = 240 ms

B0 B1 B2 B3 B4 B5 X B6 B7 B8 B9 B10 B11 X Block

Frame0 4 8 12 13 17 21 25 26 30 34 38 39 43 47 51

PTCCH

▼PDCH:�made of 52 TS of same rank belonging to 52 consecutive TDMA frames�the 52 TS are divided into blocks of 4 consecutive TS�12 blocks are created and 4 single TS:

�TS12 and TS38 for the Timing Advance,�TS25 and TS51 are pseudo Idle TS for transmission purposes (synchronization with the occurrences of SACCH on the GSM 26 multi-frame

▼According to the PDCH design, a maximum of 8 PDCHs can be created with one TRX.▼A PDCH can be entirely allocated to a single user, which is closed to the principle of circuit in GSM.


1.20

1.4 GPRS Channels MPDCH, SPDCH

▼ PDCH:

� a RLC PDU uses a PDCH block

� master PDCH (MPDCH) vs slave PDCH (SPDCH):

�MPDCH:� PDCH which carries the PCCCH and PBCCH

logical channels� not available before B7

�SPDCH:� non master PDCH

▼MPDCH are new with the B7 release.▼Beforehand, no MPDCH were available (B6.2).▼Even so, in B6.2 both the common signaling and the dedicated signaling (BSS signaling as well as the CN paging) are carried by the CCCH of GSM.▼The use of GSM CCCH for the GPRS traffic offer can lead to QoS problem in GSM (PCH use more specifically).

▼Although, the GPRS dynamic resource allocation is still valid for MPDCH. In order words, if there is no GPRS traffic in the cell, no PDCH (including Master) can be available. Even so, MPDCH available in B7 does not mean “no use of CCCH of GSM”


1.21

1.4 GPRS Channels GPRS channels

PDCH

Master PDCH Slave PDCH

PBCCH PCCCH

PDTCH PACCH

PTCH PTCCH

Primary MPDCH

PPCH PAGCH

Secondary MPDCH

physical channel

control channel

traffic channel

signaling associated control channel

logical channel category

logical channel

B8


1.22

1.4 GPRS Channels GPRS logical channels

▼ Different GPRS logical channels mapped on PDCH, which are shared on a block basis:

� PTCH: PDTCH and PACCH

� PTCCH (Packet Timing advance Control Channel)

� PBCCH (Packet Broadcast Control Channel)

� PCCCH (Packet Common Control Channel)

▼The following slides describe the content, use and multiplexing mechanisms of those logical channels in both UL and DL


1.23

1.4 GPRS Channels PTCH: PDTCH

▼ PTCH (Packet Traffic Channel):

� used for user data and associated signaling transmission

� PDTCH (Packet Data Traffic Channel):

� uni-directional channel used for user data transmission�mapped on one PDCH� up to 8 PDTCH can be allocated to a MS on different

PDCH with the same frequency parameters

▼Issue: the network must control the multiplexing of several user on a unique UL PDCH avoiding collision occurrence. This is achieved by the RLC/MAC functions and the use of USF, RRBP, and TFI fields of the RLC/MAC header

▼The number of PDTCH allocated to one UE belongs to:�The MS capabilities (multi-slot class)�The traffic in the BSS (refer to “pdch dynamic allocation” sub-chapter)�Operator configuration of the BSS parameters

▼NB: max number of PDTCH to one MS = 8 because MS has to be allocated TS on a unique TRX, and one TRX can support 8 PDCH max


1.24

1.4 GPRS Channels PTCH: PACCH

▼ PTCH (Packet Traffic Channel):

� PACCH (Packet Associated Control Channel):

� bi-directional channel used to transmit control and acknowledgement messages

�mapped on one PDCH:� if a single PDTCH is allocated to an MS, the

PACCH is allocated on the PDCH carrying the PDTCH

� if multiple PDTCHs are allocated to an MS, the PACCH is allocated on one of the PDCH carrying the PDTCHs (Alcatel BSS)

▼Caution: PACCH blocks are used to carry BSS signaling but not the GSS signaling.▼The scheduling of PACCH blocks in UL and DL is monitored by the MFS. The most frequent use of the PACCH blocks is for “Packet Ack/Nack” messages.▼It can be used as well for CS Paging message when Master Channel are not available.▼It is necessary for the UE to update the PSI13 on a regular basis in order to achieve proper RLS and Power Control mechanisms. The PSI13 content can be sent to UE in packet transfer mode via PACCH.


1.25

1.4 GPRS Channels PTCCH

▼ PTCCH (Packet Timing advance Control Channel):

� bi-directional channel (DL: TA messages ; UL: Access Burst for TA calculation) used by the continuous timing advance mechanism

� the PTCCH of one MS is carried by the PDCH carrying the PACCH

� TAI (Timing Advance Index), used for the scheduling of the AB, is part of the radio resource allocated to a MS.

� TAI is a PDCH parameter� TAI takes 16 values

▼The Access Burst in UL and the Time Advance Messages in DL are scheduled in time manner on TS12 and TS38.▼The TAI is part of the GPRS radio resources allocated by the MFS to the UE. Each mobile need to have a TAI.

▼The TAI range value is a limitation to UE multiplexing on a same TS, as both UE in UL transfer and DL transfer send their AB in UL and receive their TA value in DL

▼16 values for TAI means that each UE sends an AB every 1.96 sec, when the content of the TA Messages is updated every 480 ms (every 4 occurrences of TAM)

IdemTAM 112N+24

idemTAM 438N+715

………………

TAM 038N+13

TAM 012N+12

TAM 038N1 4 repetitions of the 16 TA values (4 TA value updated)

TAM 012N0

TA MessageOn PTCCH TS

numberA.B. scheduled for

MF-51TAI value


1.26

1.4 GPRS Channels TBF

▼ TBF (Temporary Block Flow): unidirectional flow of data between MS and MFS for the transfer of one or more LLC PDUs (refer to GSM 04.60)

▼ Several TBF can be transmitted on one PDCH (TFI 5)

▼ One TBF can be served on several PDCH (TFI 17 & 24)

▼ TBF is identified by a TFI (Temporary Flow Identity)

PDCH 1

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11

PDCH 2

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11

PDCH 3

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11

TBF with TFI = 5 TBF with TFI = 17 TBF with TFI = 24

▼NB: in B6.2 a TBF was established for the transfer of one and only one LLC PDU. This is not the case anymore in B7

▼TFI (Temporary Flow Identity):�each TBF is assigned a TFI by the MFS�More than 32 TFIs per PDCH group can be supported, provided that the same TFI value is not allocated to different TBFs whose allocated PDCHs are overlapping.

▼Important:�In B6.2 the TFI takes 32 values but the use of TFI for UL/DL PDTCH/PACCH limits the total number of TBF in a cell to 16�In B7, it is possible to establish 32 TBF per PDCH group

▼TBF: group of blocks dynamically allocated to one MS for one transfer of RLC blocks in one direction inside one cell


1.27

▼ Downlink PDTCH and PACCH blocks multiplexing

▼ Uplink PDTCH and PACCH for an UL TBF multiplexing

1.4 GPRS Channels Multiplexing of GPRS logical channels 1/2

PDTCH

TF

I24

US

F =

5

PDTCH

TF

I17

PACCH

TF

I24

TF

I UL

PDTCH/

PACCH

+1DL PDCH N°2

UL PDCH N°2

▼Downlink PDTCH and PACCH blocks multiplexing:�the multiplexing of the different MS is performed thanks to the TFI which is present in the RLC block header�an MS decodes all the blocks of all its allocated PDCH and keeps the blocks carrying its TFI in RLC header

▼Uplink PDTCH and PACCH for an UL TBF:�at UL TBF establishment, an MS receives an USF (Uplink State Flag, 8 values, MAC header) per allocated PDCH�if the MS receives its USF on the downlink block n of PDCH i it can transmit in uplink using the block n+1 of PDCH i

▼NB: the values of USF is entirely dedicated to PDTCH and PACCH transfers. See further (MPDCH and RRBP)

▼The TFI is use in UL as well: each mobile must put its TFI in the UL header of the UL blocks during an UL TBF, as well as in the RLC header of the UL PACCH blocks of a DL TBF

▼So we can say that the de-multiplexing of the blocks is achieved by the use of TFI


1.28

1.4 GPRS Channels Multiplexing of GPRS logical channels 2/2

▼ Uplink PACCH for a DL TBF scheduling:

RR

BP

≠≠ ≠≠fal

sePDTCH

TF

I24

Packet DLAck/NAckmessage

PACCH

TF

I24

US

F =

000 PACCH

TF

IXX

US

F =

5

PDTCH

TF

I17

RRBP = +3

Ø

TF

I UL

PDTCH/

PACCH

DL PDCH N°2

UL PDCH N°2

▼RRBP: Relative Radio Block Period

▼allocation of a PACCH block for the sending of acknowledgements in UL of blocks received in DL:�the MS has no USF because it is involved in a DL TBF�use of the RRBP field transmitted in downlink (MAC header ) in association with the TFI of the DL TBF in the RLC header�at the exact occurrence of the RRBP, a special USF value is used for the UL TBF taking place on the same PDCH: USF=no emission

▼Its a semi-bolean parameter. The RRBP field of a RLC/LAC block is checked each time the by the MS whose TFI is written in the RLC header.

�When RRBP is false, no UL PACCH is scheduled.�When the RRBP field is valid, the value gives the number of blocks to wait before sending its PACCH block in UL


1.29

1.4 GPRS Channels Multiplexing of GPRS logical channels: Exercise

▼ UL PDTCH and PACCH multiplexing on SPDCH:

UL transfer? DL transfer?Downlink UplinkBlock number

TFI USF RRBP

Block n

Block n+1

Block n+2

Block n+3

Block n+4

Block n+5

Block n+6

TFI a USF j

TFI b USF k

TFI a USF j + 3

TFI b USF k

TFI b ???

TFI b USF j

TFI a USF k

false

false

false

false

false

false

PDTCH / PACCH a

PDTCH / PACCH b

PDTCH / PACCH a

PDTCH / PACCH b

PDTCH / PACCH b

PDTCH / PACCH a

PDTCH / PACCH b

RLC header MAC header

?

?

?

?

?

?

?

Block Content?


1.30

1.4 GPRS Channels MPDCH logical channels

▼ MPDCH� Logical channels dynamically multiplexed:

�PBCCH, PCCCH, PDTCH, PACCH� Identified by PCCCH group (used for paging purposes)� Primary Master Channel

�PBCCH carrier, indicated in SI13� dynamic or static allocation

� Secondary Master Channels: additional MPDCH� always dynamically allocated according to PRACH,

PPCH, PAGCH load� can be pre-empted in radio high load situation (30 sec

de-allocation procedure)�maximum: NB_MAX_SECONDARY_PCCCH

▼NB_MAX_SECONDARY_PCCCH = 15 (default value) not settable at OMC-R.▼Primary MPDCH allocation:

�PBCCH is scheduled by the MFS and SI13 is updated by BSC indicating the PBCCH�MS reads SI13 once every 30 sec(or on PSI 13 for MS in packet transfer). Once MS is aware of the establishment it reads the complete PSI cycle (read PSI1 within 10 sec for MS in Packet transfer)�During this 30 sec period of time (to be achieve for a complete MPDCH alloc):

�Paging messages are mapped on both PCH and PPCH�UL TBF establishment are answered either by AGCH or by PAGCH (whether the request is sent on RACH or on PRACH)

▼Secondary MPDCH activation:�Presence indicated on PS12. The MS must read the new PSI1 and the new PSI2.�It can take the MS 30 sec (establishment duration)�Paging reorganization procedure is triggered {PAGE MODE IE = (1,0)}. MS recalculate its Packet Paging Group

▼In Release B7.1: only one PCCCH per cell▼In Release B7.2: up to 16 PCCCH per cell


1.31

1.4 GPRS Channels MPDCH logical channels configuration

▼ MPDCH configuration

� Downlink multi-frame

� primary MPDCH: the first BS_PBCCH_BLKS of the ordered list (B0, B6, B3, B9, B1, B7, B4, B10, B2, B8, B5, B11) are reserved for PBCCH

�Secondary MPDCH: the first BS_PBCCH_BLKS of the ordered list above are reserved for PAGCH

�BS_PAG_BLKS_RES: number of blocks reserved for PAGCH, after reservation of PBCCH blocks

� remaining blocks are used for PPCH, PAGCH

▼Switching from the PPCH to the PBCCH is always possible for a MS in Packet Idle Mode, since I frames (TS12 and TS38 of the 52 multi-frame) and X frames (TS25 and TS51 of the 52 multi-frame) always precede a PBCCH block.

▼Note: in B7.2, PDTCH and PACCH are not multiplexed on MPDCH (to avoid problems of inconsistent assignments crossing)

▼ BS_PBCCH_BLKS = 4 (default value). It can be set at the OMC-R level.▼ BS_PAG_BLKS_RES = 2 (default value). It can be set at the OMC-R level.


1.32

1.4 GPRS Channels MPDCH logical channels configuration: Exercise

▼ Example of DL Primary Master Channel:

� BS_PBCCH_BLKS=2

� BS_PAG_BLKS_RES=6

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11

PBCCH blocks

PAGCH blocks

PPCH, PAGCH blocks

▼CAUTION: animated slide


1.33

1.4 GPRS Channels Multiplexing of GPRS logical channels

▼ MPDCH configuration

� Uplink multi-frame

�PRACH occur on any PDCH carrying MPDCH�PRACH blocks are statically allocated on the

BS_PRACH_BLKS_MIN first blocks of the ordered list:B0, B6, B3, B9, B1, B7, B4, B10, B2, B8, B5, B11

� blocks are marked by USF=free

▼BS_PRACH_BLKS_MIN=2 (default value). It can be set at the OMC-R level.▼There is no PRACH dynamic load control and the Packet Queuing Notification message is not handled (no UL PRACH queuing)▼The FUMO BTS will not report PRACH RXLEV to the MFS. Therefore, no collision detection is possible in a cell with FUMO.

▼USF is coded over 3 bits, so 8 values are available to traffic minus 1 (free) for PRACH blocks minus 1 (no emission) for UL Ack of DL TBF with the RRBP mechanism. So, 6 USF values are available of PDTCH traffic on one PDCH


1.34

Time allowed:

10 minutes

1.4 GPRS Channels Multiplexing of GPRS logical channels: EXERCICE

� Fill-up the blocks of a DL secondary MPDCH multi-frame having the following criteria:

– BS_PBCCH_BLKS=2– BS_PAG_BLKS_RES=6

� Fill-up the blocks of a UL PDCH multi-frame having the following criteria:

– BS_PRACH_BLKS=4


1.35

1.4 GPRS Channels Multiplexing of GPRS logical channels: EXERCICE

▼ DL multi-frame: secondary MPDCH � BS_PBCCH_BLKS=2� BS_PAG_BLKS_RES=6

▼ UL multi-frame:� BS_PRACH_BLKS=4

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11

?????

?????

?????

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11

?????

?????

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11

PAGCH, PDTCH, PACCH

PAGCH

PPCH, PAGCH

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11

PRACH

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11




1 Principles

1.5 Main transactions


1.37

1.5 Main transactions TBF establishment

▼ Distinct ways to establish a TBF, according to the current BSS signaling channels available and the packet mode of the MS:

� UL TBF establishment on CCCH:

� one phase access� two phases access

� UL TBF establishment on PCCCH:

� one phase access� two phase access

� DL TBF establishment on CCCH

� DL TBF establishment on PCCCH

� UL (respectively DL) TBF establishment during a DL (respectively UL) TBF

▼The list above encounters all possible scenarios for TBF establishment.▼The procedure chosen for the establishment belongs to:

�Whether or not the MS is in packet transfer mode (a TBF already exists)�Whether or not a Master PDCH is established in the cell�Whether or not the TBF needs to offer a specified QoS (for the case of UL TBF)�Whether or not the MS is in DRX or non-DRX mode (for the case of a DL TBF in idle mode)


1.38

P49

1.5 Main transactions UL TBF establishment on CCCH, 1-phase access

MS BTS BSC MFS

TA calculation

RACH Channel request + TAChannel request

AGCH

Immediate assignmentImmediate assignment

TFI, USF, TAI, TA, PDCH

The MS switcheson the assignedPDCH USF Scheduling

PDTCH

USF Scheduling

RLC data block (TLLI, TFI)

PACCH

Packet UL Ack/Nack

PDTCH

1: request rejected

TLLI, TFI

2: request accepted

T_USF_Scheduling_AGCH

EXPIRY

P62c

P30cContention

resolution

T_GPRS_ASSIGN_AGCH

RLC data block

▼The MS initiates the channel access procedure by sending the CHANNEL REQUEST message on the RACH block located on the time slot corresponding to its CCH group. Refer to the GSM 04.08 for the RACH bitmap of the GPRS Access.▼Scenario1: request rejected. MFS sends a Packet access reject message on the same CCCH time slot. MS enters an awaiting state preventing the MS to try a new access (during WI_PR sec). The counters P105b, P105f, P105h, P27, P66 will be incremented according to the failure case. Refer to slide 1.55

▼Scenario2: request is accepted. Allocation of 1 PDCH in UL only as the multi-slot capacity of MS is unknown.�Timer1: Internal MFS timer: T_USF_scheduling_AGCH between the Immediate assignment and the first USF�Timer2: at expiry of the T_USF_scheduling_AGCH, USFs are scheduled and a second timer set to T_GPRS_Assign_AGCH – T_USF_scheduling_AGCH is started to monitor the beginning of the UL transfer. If ever this timer expires, P28 is incremented.�At expiry of Timer2, TBF is released immediately.

▼3) contention resolution example:�two MS sends a Channel request at the same time�the MS sends its TLLI in the first RLC Data Block�the TLLI is present in the acknowledgment from the MFS�the MS with the wrong TLLI is discarded

�T_GPRS_ASSIGN_AGCH = 0.8 s (default value).�T_USF_scheduling_AGCH = 100 ms (default value) not settable at OMC-R.

2


1.39

1.5 Main transactions UL TBF establishment on CCCH, 2-phases access

MS BTS BSC MFS

TA calculationRACH Channel request + TA

Channel request

AGCH

Immediate assignment


1 block, TBF starting time, TA

MS switcheson assignedPDCHs

PACCHPacket resource request

Packet UL assignment

PACCH


Packet resource request

TFI, USF, CS, TAI, TA, PDCH(s),TLLI

PDTCHUSF Scheduling

USF Scheduling

TLLI, MS Radio Access Capability

RLC data blockPDTCH

P62c

P49

P30c

1: request rejected

2: request accepted

3: request rejected

4: request accepted

T_GPRS_ASSIGN_AGCH

T_ACK_WAIT

Contention

resolution

RLC data block

▼A 2 phase access is necessary when the MS wants either to:�use RLC unacknowledged mode�give its multi slot class�give QoS parameters (Peak_Throughput_Class, Radio_Priority)

▼Scenarii 1 & 3: refer to the previous slide

▼Scenarii 2 & 4: �Timer1: T_GPRS_assign_AGCH, controls the duration between Packet Request message and the UL radio block allocated to MS

�Timer2: USFs are scheduled and a second timer set to T_ACK_WAIT is started in order to monitor the beginning of the UL transfer. If ever this timer expires before reception of the first UL block scheduled, P28 is incremented.

�T_ACK_WAIT = 1.2 s (default value) not settable at OMC-R


1.40

1.5 Main transactions UL TBF establishment on PCCCH: 1-phase access

MS MFS

Packet Channel Request

PRACH (4 A.B.)

USF scheduling

PCCCHIndication of: TFI, PDCH(s), USF(s),

TA channel, CS, TAI, initial TA value

Packet UL Assignment

RLC/MAC blocks

TLLI and TFI

Packet UL Ack/Nack

PACCH (TLLI, TFI)

P30a

1: request rejected

2: request accepted

P62a

T_ACK_WAIT

Contention

resolution

▼Possible causes for the one phase access (one phase):-One phase-Short access (less than 8 RLC blocks)-Paging response-Cell update-MM procedures (GPRS Attach, GPRS Detach, RA update)-Single block without TBF establishment

-NB: in the one phase access PCCCH, the multislot class of the MS in indicated

-Scenario1: refer to failure cases previously referred to in slide 1.55

-Scenario2: -Timer1: as soon as the”Packet UL Assignment” is sent, a timer with the value T_ACK_WAIT is started in orderto monitor the beginning of the UL transfer.-The timer is stopped at correct reception of the RLC block carrying TFI and TLLI.-If ever the timer expires then a P28 is incremented and the radio resources are frozen during T3180 on MFS side (TAI, TFI, USFs)


1.41

1.5 Main transactions UL TBF establishment on PCCCH: 2-Phase access

MS MFS

Packet Channel Request

PRACHEstablishment cause: two phases

Packet Resource Request

PAGCH (PDCH, starting time, TA value)Definition of one UL radio blockPacket UL Assignment

Packet UL AssignmentTLLI sent to the MS for contention resolution

USF scheduling

PACCH, TLLITLLI sent by the MS for contention resolution

and QoS requested

PAGCH (TFI, PDCH(s), USF, CS, TA, TAI, TLLI)

RLC/MAC blocksP30a

P62a

1: request rejected

2: request accepted

Contention

resolution

T_ACK_WAIT

T_UL_Assign_PCCCH

▼Scenario1: refer to previous slides for reject cases

▼Scenario2: �Timer1: the duration between the reception of the « Channel request » message and the uplink radio block allocated to MS is defined by the timer T_UL_ASSIGN_PCCCH

�Timer2: USFs are scheduled, as soon as the “Packet UL Assignment” message is sent and a timer with the value T_ACK_WAIT is activated in order to monitor the beginning of the UL transfer. When the first RLC data block is received, T_ACK_WAIT is stopped.

�T_Ul_Assign_PCCCH = 0.4 s (default value) is settable at OMC-R.


1.42

1.5 Main transactions UL TBF establishment during a DL TBF

MS BTS BSC MFS

RLC data block

PDTCHP30b

T_ACK_WAIT

2: request accepted

DL transfer

RLC data block, pollingRLC data block

PDTCH

Packet DL Ack/NackPACCH

Packet DL Ack/Nack with Channel request


PACCH

Packet UL AssignmentTFIUL, USF, TAI, PDCH(s)

P62b

1: request rejectedT3168

PDTCHUSF Scheduling

USF Scheduling

RLC data block

▼Scenario 1: Packet Access Reject in case of failure (P105d, P105f, P105h, P66, P27)

▼Scenario 2:�Timer1 = T_ACK_WAIT

�T3168: PSI1 / PSI13

▼It is obvious that this establishment procedure is much faster and secure than the TBF establishment with PCCCH or CCCH. Even so, it is of the best interest put the MS in this situation as often as possible.When the TBF establishment time is long compared to the TBF transfer time, the global throughput on the service is impacted.▼Alcatel offers features to delay the release of DL TBFs


1.43

1.5 Main transactions DL TBF establishment on CCCH

MS BTS BSC MFS

LLC PDUResourceallocation


1 PDCH, TFI, TAIImmediate assignment

PCH/AGCH (DRX/Non-DRX)

Packet DL assignment, polling

TFI, TAI, RRBP, PDCH(s)PACCH

Packet DL assignment

PACCH (4 A.B.)

Packet control AckPacket control AckTA calculation

Timing Advance / Power control

PACCHTA / PC

PDTCH

RLC data block

PDCH(s)allocated

P91cP91f

P90cP90f

T3190

T_GPRS_ASSIGN_AGCH

T_GPRS_ASSIGN_PCH

EXPIRY

T_GPRS_ASSIGN_AGCHT_GPRS_ASSIGN_PCH

restart

▼Packet Control Ack format = 4 access bursts

▼Timer1: T_GPRS_Assign_PCH if MS is in DRX mode, T_GPRS_Assign_AGCH if MS is in Non-DRX mode

▼The first Assignment message is sent on the CCCH (PCH if MS in DRX mode or first occurrence between AGCH and PCH if MS is in Non-DRX mode).▼The timer Timer1 is started in the MFS▼Upon reception of the Immediate Assignment message, MS starts T3190 (default value of 5s)▼After expiry of Timer1, MFS sends the a “Packet Downlink Assignment” message on the PACCH onto which the MS is supposed to have switched. ▼This procedure is repeated Max_GPRS_Assign_PCH times (Timer1 reset each time) before considering the establishment phase aborted. Then the whole DL TBF establishment procedure is restarted up to Max_DL_retrans times (3 by default not settable at OMC-R).

▼P9?c: MS in IDLE DRX mode and No MPDCH established in the cell▼P9?f: MS in Non-DRX mode and No MPDCH established on the cell

▼T3190: if this timer expires, MS returns into Packet Idle Mode.▼Packet Idle Mode:no TBF, the MS monitors the relevant Paging sub-channel (PCCCH/CCCH).▼Packet Transfer Mode: the MS is allocated radio resources providing a TBF for physical point to point connection on one or more packet data physical channels for the unidirectional transfer of one or more LLC PDUs.

▼T_GPRS_Assign_PCH = 1.4 s (default value)▼Max_GPRS_Assign_PCH_retrans = 3 (default value)▼Max_GPRS_Assign_AGCH_retrans = 3 (default value)▼T_ACK_WAIT = 1.2 s (default value) not settable at OMC-R▼ T_ACK_WAIT_DRX_PCCCH = 2.5 s (default value) not settable at OMC-R


1.44

1.5 Main transactions DL TBF establishment on PCCCH

MS MFS

Packet DL Assignment (polling)

PPCH (RRBP, PDCH(s), TFI, TAI)

PPCH/PAGCH – Non DRX modeDRX mode / Non DRX mode

Description of the allocated PDCH(s)

Packet PC/TA

PACCH

Packet Control Ack

DL RLC/MAC blocks

PACCH

P91a, P91d

P90a, P90d

T_ACK_WAITT_ACK_WAIT_DRX_PCCCH

T3190

▼Use of the PPCH Blocks:�P9?a: DRX mode = Packet DL Assignment message carried by PPCH blocks corresponding to the MS paging group�P9?d: Non DRX mode = use of the first available occurrence of the PPCH/PAGCH block

▼Timer1: T_Ack_Wait_DRX_PCCCH when MS in DRX mode, T_ACK_WAIT otherwise.

▼The MS acknowledges the “Packet DL Assignment” message on the same PCCCH slot.▼If Timer1 expires before the acknowledgement from MS, the procedure is restarted completely up to Max_Retrans_DL times.


1.45

1.5 Main transactions DL TBF establishment during an UL TBF

MS BTS BSC MFS

UL transfer

Packet DL assignment, pollingPacket DL assignment

PACCH

Packet control AckPACCH (4 A.Bs)

TFIDL, TAI, RRBP, PDCH(s)

Packet control Ack

PACCH

TA / PCTA / PC

PDTCH

RLC data block

P91bP91e

P90bP90e

T3190

T_ACK_WAIT

▼P9?b: MS in transfer UL▼P9?e: T3192 is still running, fast DL re-establishment case

▼Timer1: T_ACK_WAIT. If Timer1 expires before MS acknowledgment, MFS retries the complete procedure Max_Retrans_DL times.

▼If T3190 expires, MS aborts the DL TBF establishment procedure.


1.46

1.5 Main transactions Delayed DL TBF release 1/2

▼ Artificial extended DL TBF duration aiming at coping with jerky DL traffic from CN

▼ EN_DELAYED_DL_TBF_REL = Enable▼ Procedure:

� the last DL RLC blocks is marked with FBI=0� the TBF state goes from Active to Delayed� periodical Dummy DL RLC blocks in polling (S/P=1) sent by

MFS to trigger acknowledgement from MS (FAI=0)� when a new DL LLC PDU arrives at the MFS, the useful

RLC Block transfer is resumed� The TBF state goes from Delayed to Active

▼ MS does not take into account Dummy LLC PDU during the delayed release phase

▼Jerky LLC PDU delivery at MFS due to buffer capacities of servers, SGSN and MFS. A TCP segment can generate up to 3 LLC PDU. Also called “Bursty traffic”. HTTP and WAP services are likely to benefit from this feature

▼FBI: Final Block Indicator (RLC header)▼FAI: Final Acknowledgement indicator▼S/P: triggers polling (packet Ack/Nack message) when set to 1

▼Periodical sending of DL RLC Blocks = polling period calculation: MFS takes into consideration T3190 (guarding timer between 2 valid data received from Network) in addition to the requirement of receiving at least one block every 360 ms (78 TDMA frames). (T3190n = 5s by default not settable at OMC-R).▼The UL Delayed TBF release (scheduling of additional USF) is only possible for rel4 MS (not available on the market place today)


1.47

1.5 Main transactions Delayed DL TBF release 2/2

▼ End of delayed released period� MFS sends a Dummy UI command marked with FBI=1, S/P=1� Acknowledge mode:

�MS sends the last Packet DL Ack/Nack message (FAI=1)� Non-Acknowledge mode:

�MS sends the last Packet Control Ack message� T3192n and T3192 are triggered (Fast DL re-establishment)

▼ RRM periods on MFS side:� T_DELAYED_DL_TBF_POL_INIT, then

T_DELAYED_DL_POL: period between 2 DL Dummy UI sent to MS

� T_DELAYED_DL_TBF_REL: overall duration of Delayed TBF release period

▼T_DELAYED_DL_TBF_REL = T_DELAYED_DL_TBF_REL_RADIO + T_NETWORK_RESPONSE_TIME (the later being tunable at OMC-R)

▼Upon each expiry of t_DELAYED_DL_TBF_POL (the timer reaches T_DELAYED_DL_TBF_POL_INIT or T_DELAYED_DL_TBF_POL), a new Dummy UI command is inserted and t_DELAYED_DL_TBF_POL is restarted.

▼T_DELAYED_DL_TBF_POL_INIT = 100 ms▼T_DELAYED_DL_TBF_POL = 200 ms▼T_DELAYED_DL_TBF_REL_RADIO = 1200 ms▼ all these timers values are default ones and are not settable at OMC-R

▼T_NETWORK_RESPONSE_TIME corresponds to the time difference between a command sent to the SGSN and the response received at the MFS. Default value is 700ms but is settable at OMC-R and can be tuned according to Gb traces.


1.48

Time allowed:

10 minutes

1.5 Main transactions Ddelayed TBF release: Exercise 1/2

� DL TBF routine in acknowledge mode

� Fill-up the blanks in the diagram of a DL TBF displayed on the following slide:

– name of the timers “T_?????”

– states of the DL TBF? ACTIVE, DELAYED, RELEASED


1.49

1.5 Main transactions Delayed TBF release: Exercise 2/2


1.50

1.5 Main transactions Fast DL TBF re-establishment 1/2

▼ After DL TBF release (with or without delayed release phase), the following timers are considered

▼ MS side

� T3192 started after sending of final Packet DL Ack/Nack message (FAI=1)

� during T3192 the MS listens to the PDCH carrying the PACCH blocks of its last DL TBF

▼T3192: same parameter as in B6.2 release. Default value in B6.2 = 500 ms

▼T3192n takes into account the trip time needed for “Packet DL Ack/Nack” message from MS to MFS (½T_Round_Trip_Delay + ½T_Fast_DL_Margin) AND trip time needed for “Packet DL Immediate Assignment ” message from MFS to MS (½T_Round_Trip_Delay + ½T_Fast_DL_Margin)

▼T_Round_Trip_Delay (MFS-MS) = 160 ms (default value settable at OMC-R)

▼Fast_DL_Margin = 50 ms

▼Note: during T3192n seconds, the Timing Advance is monitored. Even so, if TAI occurs, MS must send its Access Burst for the Timing Advance calculation by BTS. MS must listen to the TA Messages in DL.


1.51

1.5 Main transactions Fast DL TBF re-establishment 2/2

▼ MFS side

� T3192n started after reception of final Packet DL Ack/Nack message

� wait for reuse of MS radio resources (PDCHs, TAI, TFI)

� If a DL LLC PDU is received by the MFS, a fast DL TBF re-establishment is triggered on the PACCH

� T3192n = T3192 – (T_Round_Trip_Delay + T_Fast_DL_Margin)

▼ During T3192n, UL TBF establishment is not possible

▼This feature is inherited from B6.2 were the shortage of radio resource is more likely to occur: one PDCH group per cell.▼Moreover, it was the unique mechanism available for coping with discontinuous stream of data before Delayed DL TBF release was implemented.▼During the on-going of T3192n, no UL TBF establishment procedure can be proceeded. This is a limitation to fast switching from DL TBF to UL TBF during the MS-GSS signaling procedure (location update for example). In order to avoid a too long duration of these procedure, the MFS anticipates the UL TBF establishment by starting the procedure before the end of the DL TBF release.

▼The timer T3193 used on the MFS side in B6.2 is not used any more.


1.52

1.5 Main transactions Non-DRX mode after packet data transfer 1/2

▼ Feature introduced with the MFS 42W software version

▼ Discontinuous Reception (DRX-mode):

� used in GSM to increase the battery autonomy on MS as in GSM CS: MS listen only to its Paging Group

� Downlink TBF establishment through PCH long as compared with the TBF duration

� MFS establishes DL TBF on the first available PCH message of MS Paging group

▼ Non-DRX:

� continuous monitoring of AGCH messages by MS

� MFS establishes DL TBF on first available AGCH block or the first PPCH occurrence

▼This feature outlines one of the major differences between GPRS service (non connected mode) and GSM service (connected mode). DRX mode is highly recommended in GSM to save the cell battery when it can be a handicap in GPRS (where the paging is likely to occur more frequently)

▼Some tests were carried to determine to benefits of the use of Non-DRX period for a faster DL TBF establishment time.


1.53

1.5 Main transactions Non-DRX mode after packet data transfer 2/2

▼ Non-DRX mode:

� Non-DRX period

�Min (NON_DRX_Timer ; DRX_Timer_MAX)�Non-DRX period computed by MFS and send in “Packet

DL Immediate Assignment” message

� DRX mode of MS evaluated each time MFS received DL LLC PDU from SGSN

� MFS keeps MS context until expiry of:

�DRX_Timer_MAX if NON_DRX_Timer unknown for MS �Non-DRX period otherwise (provided within the DL LLC

PDU)

▼NON_DRX_Timer is unknown for the MFS when after the release of an uplink TBF when no DL concurrent TBF was Established, or after the release of a downlink TBF when the DL LLC PDUs do not convey the DRX parameters.

▼In DRX mode, the MFS establishes the DL TBF on PCH or PPCH channel, by sending respectively a Channel Assignment Downlink message on the BSSGP interface with the IMSI or by sending a PDCH-DL-ASSIGNMENT PDU on the PMU-PTU interface.

▼When the MFS assesses that the MS my return to the DRX mode during the transmission of the assignment message, the message is sent o the PCH or the PPCH channel. The MFS must then take into account the 95% AGCH or PPCH queuing time (about 400ms) in addition to the round trip time delay measured at RRM level (about 160ms).▼Assuming a Non-DRX period of 2 seconds, this means that the downlink LLC PDU must be received within 1,4 seconds to speed up the establishment of the DL TBF

▼DRX_Timer_Max = 2s by default and is settable at OMC-R


1.54

1.5 Main transactions DL TBF release routine

▼ DRX_Timer_MAX:

� limited to 4 seconds

� Broadcast on SI 13

Fast DL TBF establishmentduring T3192n

Fast DL TBF establishmentvia AGCH, Non-DRX mode

DL TBF establishmentvia PCH

DL TBF

Delayed DL TBF Release

▼The tables below indicate examples of the expected DL TBF establishment duration with or without the feature.


1.55

1.5 Main transactions TBF establishment, QoS indicators 1/7

▼ DL and UL TBF establishment: introduction

TBF establishmentNumber of requestsNumber of successes

Success rate

Failure causes

time

TBF end

Congestion

Radio

BSS

Gb

Distribution of number of TS requested/obtained

Radio

Ater

GPU

Different cases:•DL/UL: idle & transfer mode•DL/UL: MPDCH or not•DL: DRX & non-DRX•DL: T3192 running

Allocation rate

▼ The number of TBF establishment requests gives an idea of the GPRS traffic. It is therefore a KPI.▼ Nb of Allocation successes = Nb of Requests - Nb of Congestions▼ A radio pb can be specific to GPRS (no radio pb for GSM): it can be due to the MS behavior (bad handling of Polling

from the BSS).▼ Some tests on Ping have shown that RTT is varying from one MS to another. Some MSs are considered to be slow,

others to be fast.


1.56


▼ DL and UL TBF establishment: indicators = f(counters)

Transfer phase Fast DL TBF re-establishment T3192 Non-DRX mode DRX mode

time

DL TBF establishment requests DL TBF establishment successes

Transfer mode P91b Transfer mode P90b

While T3192 running P91e While T3192 running P90e

Idle mode + non-DRX mode + MPDCH P91d Idle mode + non-DRX mode + MPDCH P90d

Idle mode + non-DRX mode + no MPDCH P91f Idle mode + non-DRX mode + no MPDCH P90f

Idle mode + DRX mode + MPDCH P91a Idle mode + DRX mode + MPDCH P90a

Idle mode + DRX mode + no MPDCH P91c Idle mode + DRX mode + no MPDCH P90c

UL TBF establishment requests UL TBF establishment successes

Idle mode + MPDCH P62a Idle mode + MPDCH P30a

Idle mode + no MPDCH P62c Idle mode + no MPDCH P30c

Transfer mode P62b Transfer mode P30b


1.57



% TBF establishment failures

Downlink Uplink

Congestion rate (radio-Ater-

GPU)

(P14 + P105g + P105c + P105e) / (P91a +P91b+ P91c +

P91d + P91e + P91f)

Congestion (radio-Ater-GPU)

rate

(P27 + P105h + P105d + P105f) / (P62a + P62b + P62c)

Radio congestion rate P14 / (P91a + P91b + P91c + P91d + P91e + P91f) Radio congestion rate P27 / (P62a + P62b + P62c)

% of time during which

PDCH allocation for DL TBF

is not possible due to

congestion

(P13 / 10) / GP % of time during which

PDCH allocation for UL TBF

is not possible due to

congestion

(P26 / 10) / GP

ATer congestion rate P105g / (P91a + P91b + P91c + P91d + P91e + P91f) ATer congestion rate P105h / (P62a + P62b + P62c)

DSP congestion rate P105c / (P91a + P91b + P91c + P91d + P91e + P91f) DSP congestion rate P105d / (P62a + P62b + P62c)

CPU congestion rate P105e / (P91a + P91b + P91c + P91d + P91e + P91f) CPU congestion rate P105f / (P62a + P62b + P62c)

Radio problem rate P15 / (P91a + P91b + P91c + P91d + P91e + P91f) Radio problem rate P28 / (P62a + P62b + P62c)

Gb problem rate P65 / (P91a + P91b + P91c + P91d + P91e + P91f) Gb problem rate P66 / (P62a + P62b + P62c)

BSS problem rate (P91a + P91b + P91c + P91d + P91e + P91f - P14 - P15

- P90a - P90b - P90c- P90d - P90e - P90f - P65 - P105e

- P105c - P105g) / (P91a + P91b + P91c + P91d + P91e

+ P91f)

BSS problem rate ((P62a + P62b + P62c - P27 - P28 - P30a - P30b - P30c

- P66 - P105h - P105f - P105d) / (P62a + P62b + P62c)

▼ A CPU load state is managed per GPU. When the CPU load state reaches the maximum (crosses a Critical threshold) then no new TBF can be established on CCCH or PCCCH on this GPU.

▼ Radio congestion is often low. When high, it is often linked to a GPU reset or to a problem at BBS level. � Therefore Indicators based on distribution of nb of TSs allocated/requested give a better idea of the “congestion”

situation.▼ On DL TBF establishment failure: a RADIO STATUS message is sent to the SGSN.


1.58



TS distribution

DL TBF establishment UL TBF establishment

Number of TBF establishments requesting 1 slot

which are satisfied at once by the initial

allocation

P160 Number of TBF establishments requesting 1 slot

which are satisfied at once by the initial

allocation

P161

Number of TBF establishments requesting 2 or 3

slots which are satisfied at once by the initial

allocation

P162 Number of TBF establishments requesting 2 or 3


allocation allocation

P163



allocation



allocation

P165


slots which are partially satisfied by the initial

allocation



allocation

P167



allocation



allocation

P169

TBF establishments requesting 2 or 3 slots partial

success rate

P166 /

(P162 + P166)


success rate

P167 /

(P163 + P167)


success rate

P168 /

(P164 + 168)


success rate

P169 /

(P165 + P169)

▼ MS on the market: 4 TS DL max, 2 TS UL max (MS class 9 & 10).


1.59


Downlink TBF establishment per MS type

0%

20%

40%

60%

80%

100%

14 /08 /20

03

16 /08 /20

03

18 /08 /20

03

20 /08 /20

03

22 /08 /20

03

24 /08 /20

03

26 /08 /20

03

28 /08 /20

03

30 /08 /20

03

01 /09 /20

03

03 /09 /20

03

05 /09 /20

03

07 /09 /20

03

09 /09 /20

03

11 /09 /20

03

13 /09 /20

03

91

92

93

94

95

96

97

98

99

4-5 partially

2-3 partially

4 or 5 TS

2 or 3 TS

1 TS

% Tot

Uplink TBF establishment per MS type

0%

20%

40%

60%

80%

100%

14 /08 /20

03

16 /08 /20

03

18 /08 /20

03

20 /08 /20

03

22 /08 /20

03

24 /08 /20

03

26 /08 /20

03

28 /08 /20

03

30 /08 /20

03

01 /09 /20

03

03 /09 /20

03

05 /09 /20

03

07 /09 /20

03

09 /09 /20

03

11 /09 /20

03

13 /09 /20

03

96.5

97

97.5

98

98.5

99

99.54-5 partially

2-3 partially

4 or 5 TS

2 or 3 TS

1 TS

▼ The typical values of the DL TBF partial establishment success rate are:� Without congestion (GSM+GPRS): less than 10% of the total of establishment successes.� With some congestion: between 10 and 20%� With a high level of congestion: more than 20%.

▼ These values depend on the penetration rate of the MS with 4 TS on the downlink (class 8,10) => Correlation needed with the TBF establishment partial success rate per Nb of TSs requested (see previous page).

➨ Use of indicators of partial success rate according to TS distribution to assess GPRS Radio Congestion.▼ Congestion will be reduced by reducing the GPRS signaling load (e.g., Nb of RA update decreased when Suspend/Resume

is successful).


1.60



KPI

KPI

TBF establishment requests and successes

Downlink Uplink

Total number of TBF

establishment

requests

P91a+P91b+P91c+P91d+P91e

+P91fTotal number of

TBF

establishment

requests

P62a+P62b+P62c

Total number of TBF

establishment

successes

P90a+P90b+P90c+P90d+P90e

+P90f

Total number of

TBF establishment

successes

P30a+P30b+P30c

TBF establishment

success rate

(P90a+P90b+P90c+P90d+P90

e+P90f) /

(P91a+P91b+P91c+P91d+P91

e+P91f)

TBF

establishment

success rate

(P30a+P30b+P30c) /

(P62a+P62b+P62c)

TBF establishmentallocation rate

( (P91a + P91b + P91c + P91d+ P91e + P91f) - (P105c +

P105e + P14 + P105g)) /

(P91a + P91b + P91c + P91d

+ P91e + P91f)

TBF establishmentallocation rate

((P62a + P62b + P62c) -(P105f + P27 +P105h +

P105d)) / (P62a + P62b

+ P62c)


1.61


▼ Thresholds:

� Significant traffic is reached for 2000 DL TBF requests/cell/day (less when Delayed downlink TBF release is activated)

� UL/DL TBF establishment success rate is seen as good above 95% (except if CS2 is used at beginning of DL TBF)

Downlink TBF Establishment

0

2000

4000

6000

8000

10000

12000

14000

16000

14 /08 /20

03

16 /08 /20

03

18 /08 /20

03

20 /08 /20

03

22 /08 /20

03

24 /08 /20

03

26 /08 /20

03

28 /08 /20

03

30 /08 /20

03

01 /09 /20

03

03 /09 /20

03

05 /09 /20

03

07 /09 /20

03

09 /09 /20

03

11 /09 /20

03

13 /09 /20

03

90

92

94

96

98

100

102 BSS fail

Gb fail

Radio fail

Congestion

Request

% Allocated

% Success

▼ Typical values of DL establishment success rate when CS2 is used at the beginning of DL TBF: 94%, 96%.▼ TBF establishment indicators should be provided on a per DL and UL basis because the procedures are very different and

QoS has to be assessed and interpreted differently.▼ The UL TBF establishment can be degraded because of ghost Random Access messages.▼ The amount of bytes transferred at RLC or LLC level should be considered as a significant traffic indicator (more Web

browsing usage than WAP).▼ The nb of DL TBF establishment requests can should be considered as a GPRS activity indicator.


1.62

1.5 Main transactions Mobility Management: definitions

▼ For GPRS, as paging is more frequent than in GSM, RA were defined which can be smaller than LA

▼ A RA is a subset of one and only one LA

▼ The MS location in Standby state is known in the SGSN at the RA level

▼ The MS is paged in its RA when MT traffic arrives at the SGSN

▼ one RA is served by only one SGSN

▼2 types of PCH/PPCH use must be kept distinct for PS procedures:�DL transfer establishment for MS in Ready State: mapping of the DL Immediate Assignment message�DL transfer establishment for MS in Standby State (PS Paging Procedure): mapping of the Packet Paging Request message

▼The first type will obviously be used quite often but does not affect the dimensioning of the RA (the message is sent in one cell only). The second type of paging is sent over the RA and will occur more often that CS Paging as the transfer mode of most external servers is bursty, so the rate of arrival of the PDU inside the SGSN is irregular. This is the reason why RA must be dimensioned smaller that LA if we want to achieve a battery use relative to GPRS Paging procedures equivalent to the GSM one.

▼For Mobility Management constraints in the CN, it is not recommended to split one RA over 2 LA (the routing information for a Paging Message CN originated being the BSC, a given BSC must belong to a unique LA as well as a unique RA).


1.63

1.5 Main transactions Mobility Management: UE states

"Idle"Attachment to

networkDetachment

Out of Time

Packet Tx or Rx

Detac

hmen

t or O

ut of

Tim

e

"Ready""Stand-by"

Packet Idle Mode

Packet Transfer

Mode

▼Idle: the MS is not attached to the network: paging is not possible▼Standby:

�the MS is attached to the network: paging is possible�the MS location is known in CN with the RA accuracy

▼Ready:�the MS location is known with the cell accuracy�timer T_READY keeps the MS in the Ready state just after data transfer

▼The timers regulating the transition between states are SGSN timers, not tunable in the BSS.▼Caution: Idle mode in GPRS and Idle mode is GSM are two different states.

�A GSM MS in Idle mode is attached to a MSC and can be paged�A GPRS MS in Idle mode is NOT attached to a SGSN, so cannot be paged but can monitor the GPRS information broadcast in the SI13 of the BCCH

▼ Standby is the closest GPRS UE state to Idle GSM.▼The UE state in the SGSN must be considered apart from the packet transfer mode in the BSS:

�A MS in Standby can be in packet transfer mode�A MS in Ready can be in packet idle mode

▼The detach procedure is usually triggered by the MS. Three other types of detach are triggered by the CN:�HLR Detach�SGSN Detach upon SGSN overload�SGSN Detach upon timer


1.64

11.5 Main transactions Mobility Management: MS location management

MS enters in a new cell

New cell inside the current RAMS in Ready state

Cell update

New cell belongs to a new RA

RA update

New cell belongs to a new LA

RA/LA updateOnly in NMO I

▼When the MS is in Ready State, it performs a “Cell Update”.�MS sends any LLC frame in the new cell with its TLLI in the header�The Cell and RAC information is added by the BSSGP at the programming of the BSSGP frame

▼RA Update:�The MS sends a RA Update Request message containing (identity of the MS, old RAI, Update Type). The update type is either enter a new RA or periodical RA update.�The BSS adds the cell global Identity when transferring the message into a BSSGP frame towards the SGSN.


1.65

1.5 Main transactions Session management: Attach procedure

▼ Aim: to access to GPRS services, an MS must first make its presence known to the network by performing a “GPRS attach” procedure with the SGSN

▼ Results:

� a logical link between the MS and the SGSN is created

� the MS is in Standby state and can activate a PDP context

� the MS location is known (RA accuracy)

� the MS is available for paging via the SGSN

▼ Combined GPRS and IMSI attach is possible for class A/B MS

▼Refer to APPENDIX - Gb Traces for the details of the « Attachment » procedure.

▼Each signaling procedure taking place between the MS and the GSS involves UL and DL TBF. Each GMM/SM message triggers the establishment of a TBF. The complete attachment procedure in GPRS involves 7 TBFs (4 UL and 3 DL).

▼These TBFs are usually short (a few RLC blocks), thus the optimization of the TBF establishment time is very important, as well as the TBF establishment success rate.


1.66

1.5 Main transactions Session Management: PDP context activation

▼ Aim:

� in order to send and receive GPRS data, the MS must activate the PDP address it wants to use

▼ Results:

� the MS is known in the corresponding GGSN (the GGSN knows the SGSN where the MS is located) and data transmission with external data network can begin

▼ Refer to Appendix for field examples

▼The PDP context activation procedure is fairly close the the call establishment of the GSM including the CCCH and the SDCCH phases (between the Channel Request message of the MS on RACH to the Alert message)

▼It is important to control the overall PDP context activation duration for a good overview of the GPRS QoS as it involves MS, MFS, SGSN, GGSN. The duration is longer that the GSM call establishment.


1.67

Time allowed:

2 minutes

1.5 Main transactions Exercise: Paging for DL data transfer 1/2

� Find the name of the procedure 1 displayed on the following diagram

� Find the name of the procedure2 likely to take place after procedure1 is completed


1.68

1.5 Main transactions Exercise: Paging for DL data transfer 2/2

MS BTS BSC MFS SGSN

PDP PDU

MS inStandby

PS Paging

PCH

Packet paging request

RACH

channel requestcause =?

AGCH or PCH


MS Ready

DL UNITDATA PDU

USF Scheduling

PDTCH

PDTCH

Sending of a LLC PDU

Procedure1?

Procedure2?

P53a


1.69

1.5 Main transactions CCCH, QoS indicators 1/3

▼ GPRS service and CCCH load: introduction

CCCH load RACH

PCH: PS paging, CS paging, Immediate assignment

AGCH


1.70


▼ GPRS service and CCCH load: indicators = f(counters)

CCCH load

Paging usage rate due to GPRS P53a / MC8A

PCH use due to GPRS Immediat Assignment P53c

Ratio PS/CS paging through SGSN P53a / (P53a+P53b)

RACH usage rate due to GPRS P62c / MC8C

AGCH usage rate due to GPRS P49 / (P49 + MC8B + MC8D)

▼ P53a = Number of (BSCGP) PAGING REQUEST for PS paging sent to the MS (through the BSC which manages the PCH resource). (used for instance for a MT picture transfer MMS service)

▼ P53b = Number of (BSCGP) PAGING REQUEST for CS paging sent to the MS (through the BSC which manages the PCH resource) -> Need of Gs interface.

▼ P53c =Number of (BSCGP) IMMEDIATE ASSIGNMENT sent to the MS (through the BSC which manages the PCH resource) for a DL TBF establisment when the MS is in DRX mode.

▼ GSM Paging Command (one per Mobile) or GPRS (BSCGP) PAGING REQUEST are merged into PAGING REQUEST on radio layer.


1.71


GPRS/GSM AGCH breakdown

0

50000

100000

150000

200000

250000

300000

350000

400000

450000

14 /08 /20

03

16 /08 /20

03

18 /08 /20

03

20 /08 /20

03

22 /08 /20

03

24 /08 /20

03

26 /08 /20

03

28 /08 /20

03

30 /08 /20

03

01 /09 /20

03

03 /09 /20

03

05 /09 /20

03

07 /09 /20

03

09 /09 /20

03

11 /09 /20

03

13 /09 /20

03

0

0.51

1.52

2.53

3.54

4.5

PS AGCH

Tot AGCH

% PS AGCH

GPRS/GSM RACH breakdown

0

50000

100000

150000

200000

250000

300000

350000

400000

450000

14 /08 /20

03

16 /08 /20

03

18 /08 /20

03

20 /08 /20

03

22 /08 /20

03

24 /08 /20

03

26 /08 /20

03

28 /08 /20

03

30 /08 /20

03

01 /09 /20

03

03 /09 /20

03

05 /09 /20

03

07 /09 /20

03

09 /09 /20

03

11 /09 /20

03

13 /09 /20

03

0

0.51

1.52

2.53

3.54

Tot RACH

% PS RACH

GPRS/GSM PCH breakdown

0

2000000

4000000

6000000

8000000

10000000

12000000

14000000

16000000

18000000

20000000

14 /08 /20

03

16 /08 /20

03

18 /08 /20

03

20 /08 /20

03

22 /08 /20

03

24 /08 /20

03

26 /08 /20

03

28 /08 /20

03

30 /08 /20

03

01 /09 /20

03

03 /09 /20

03

05 /09 /20

03

07 /09 /20

03

09 /09 /20

03

11 /09 /20

03

13 /09 /20

03

0

0.10.20.30.40.50.60.70.80.91

CS PAging

PS Imm. As

PS PAging

%io PS Pag

CS AGCH



1 Principles

1.6 Other concepts and definitions


1.73

1.6 Other concepts and definitions System information broadcasting on BCCH 1/2

▼ The BCCH indicates if GPRS is supported in the cell:

� SI 3: RA_COLOUR field present if GPRS supported

▼ If GPRS is supported:

� SI13 is broadcast on the BCCH

� SI13 broadcast instead of retransmission of SI 1

▼ SI 4 content:

� SI13_PBCCH_LOCATION: gives SI 13 schedule or PBCCH location

▼Note: do not get confused between RA_COLOUR and RA Code. The former is used as a flag which has two uses for the MS entering a new cell:

�To know if the GPRS service is supported in the cell (RA_COLOR has a value different from -1)�To trigger a RA update when the value of the RA_COLOR changes. It is easy to monitor because it is broadcasted often.

▼The Routing Area Code is necessary for the RA update procedure (message content).

▼The SI13 takes the place of a few SI1 occurrences.


1.74

1.6 Other concepts and definitions System information broadcasting on BCCH 2/2

▼ SI 13 content (non-exhaustive list):� RA: routing area code� NMO: network mode of operation� PAN_DEC, PAN_INC, PAN_MAX: radio link supervision� ALPHA: uplink power control� T_AVG_T, T_AVG_W: MS calculation of average levels� PC_MEAS_CHAN: level measurements on BCCH /

PDCH� NETWORK_CONTROL_ORDER: set to NC0 = MS

controlled cell reselection , no measurement reporting� GPRS MA: for hopping PDCH group� Access Burst Type

▼MS has to get SI13 information on a regular basis:�each time the SI13 content is updated (PSI field = SI13_CHANGE_MARK set to 1)�every 30 seconds max (even if TBF has to be interrupted)

▼Through 2 different ways: SI13 on the BCCH or PSI13 in a PACCH block▼MS has always the time to switch on PSI13 in NMOIII and/or NMOI with Master PDCH because PBCCH blocks are always after a I or X TS within the 52 multi-frame.

▼Access Burst Type: it defines the access burst (8 bits or 11 bits) to be used on the PRACH, PTCCH, and the “Packet Control Ack” on PACCH


1.75

1.6 Other concepts and definitions System information broadcasting on PBCCH 1/3

▼ If a primary MPDCH is available, a GPRS MS monitors the PBCCH

▼ PSI blocks available: PSI1, PSI2, PSI3, PSI3bis, PSI8, PSI13

▼ PSI1, PSI2 and PSI13 (=SI13 on BCCH) can be sent in a PACCH block for MS in packet transfer mode

▼ PSI1 content:

� Cell and BSS parameters

� PRACH access control parameters

� PCCCH organization parameters

� Power Control parameters

� CN features (MSC Release, SGSN Release)

▼Cell Parameters = NMO, MS Timers, DRX info, RLS parameters, …▼PRACH access control parameters = access burst type, access control class, …▼PCCCH organization parameters = BS_PBCCH_BKLS, BS_PAGCH_BLKS_RES, BS_PRACH_BLKS▼Power control parameters =

▼The GPRS cell adjacencies are the same for MS in Packet Idle mode and MS in Packet Transfer Mode▼The GPRS cell adjacencies are set equal to CS cell adjacencies


1.76


▼ PSI2 content:

� Cell identification (PLMN Id, LAC, RAC, Cell Id)

� Non GPRS O&M parameters (BS_PA_MFRMS, BS_AG_BLKS_RES)

� PCCCH information (TS and frequencies)

� Cell allocation information (HSN, BCCH band, frequency channels)

▼ PSI3 /PSI3bis content:

� BCCH allocation in neighbor cells

� Serving cell parameters (CELL_BAR_ACCESS_2, GPRS_RXLEV_ACCESS_MIN…)

� General reselection parameters serving and neighbor cell

� Neighbor cell parameters

� LSA of serving and neighbor cells (if En_SOLSA=True): PSI3 only

▼PSI3, PSI3bis:�One PSI3 instance must be sent and , as a minimum, one PSI3bis instance must be sent as well�There can be up to 16 PSI3bis instance� Reselection parameters: C31_HYST, C32_HYST, GPRS_CELL_RESELECT_HYST� Neighbor cell parameters: BSIC, BCCH frequency, SI13 PBCCH location�Up to 32 neighbor cells can be defined. The field Same_RA_As_Serving_Cell provides complementary information for reselection process.


1.77


▼ PSI8 content:

� Optionally sent on PBCCH

� Cell broadcast information

�CBCH channel description (TS number)� Frequency parameters for hopping CBCH� Frequency parameter for non-hopping CBCH (TSC,

ARFCN)

▼TSC:Training Sequence Code used for CBCH is the BCC value▼MAIO: Mobile Access Index Offset▼HSN: Hoping Sequence Number (law for frequency hoping)▼MA_bitmap: MA_Bitmap is related to BCCH band location▼MA_length: length of the MA_bitmap, giving the number of frequency to hope on


1.78

1.6 Other concepts and definitions System information broadcasting on PACCH

▼ PSI broadcast on PACCHs is controlled at MAC layer by the O&M parameters T_PSI_PACCH

▼ PSI13 content:

� GPRS cell access information (RAC, NCO, Access_Burst_Type ,…)

� Radio Link Supervision parameters, Power control information

� MS timers for TBF establishment (T3168, T3182,…)

▼The GPRS cell information as well as the Radio Link Supervision and Power Control information are similar as the one included in the SI13 on BCCH

▼T3168, T3164, T3182, T3190, T3180: refer to there use for TBF establishment and Radio Link Control (causes of TBF releases on the MS side). We can note that the MS timer name use even numbers when the BSS ones use odd numbers.

▼T_PSI_PACCH = 14 s by default but settable at OMC-R


1.79

1.6 Other concepts and definitions Interactions between SGSN and MSC/VLR

▼ The Gs interface between the MSC and the SGSN is needed

▼ Following actions are possible:

� IMSI attach/detach via SGSN

� LA update via SGSN

� CS paging via SGSN

▼The Gs interface carries signaling between the P-VLR (SGSN) and the VLR (MSC). Whether Gs is provided or not does NOT belong to the BSS release as it is a CN feature.▼The presence of the Gs interface is given by the NMO information inside the SI13 and the CN feature in the PSI1.▼The Gs interface carries only MAP signaling between the P-VLR and the VLR of the MSC.


1.80

1.6 Other concepts and definitions Network mode of operation

Mode CS paging channel PS paging channel Remarks

PCH/PPCH PPCH Gs interface

PCH PCH Gs interface

PACCH NA Gs interface

PCH PCH no Gs interface

PCH NA no Gs interface

PCH PPCH no Gs interface

I

II

III

w MPDCH

wo MPDCH

Packet idlemode

Packettransfermode

▼Available in B6.2 already:�NMOII, is the NMO used is B6.2 = no MPDCH and no Gs�NMOI, no MPDCH but Gs interface offered

▼New with the B7, all the possible combination with the MPDCH:�NMOIII�NMOI with MPDCH

▼According to the NMO offered and the packet mode of the MS (packet transfer mode or packet idle mode), the routing of the PS paging and the CS paging changes.


1.81

1.6 Other concepts and definitions CS/PS Paging during a packet transfer/call (1/3)

▼ CS paging during packet transfer (class B MS):

� according to the GSM standard, a class B MS can or can not (implementation dependent) listen to the PCH channel during a packet transfer

� if the MS listens to the PCH channel:

� some RLC blocks are lost� the MS receives all the CS paging messages� the MS can start a CS call� at the end of the call the MS triggers a RA updating

procedure�Refer to Suspend/Resume for Class B MS

▼The ClassA and ClassC GPRS mobiles do not face these problems. The former is able to handle simultaneously CS and PS traffic (no traffic disruption), when the later is not reachable in one domain while it is attached to the other domain.

▼The ClassB situation is the most complex one and must be consider as ClassB GPRS mobile are the most popular for the manufacturers. It must be remembered that the most important service in the GSM network GPRS activated is the speech. Therefore, MS must be given the opportunity to listen to any CS paging. It is then up to the operator and MS to decide whether or not the CS call must be answered.


1.82


▼ Suspend Resume for Class B MS:

1. Suspend (TLLI, RAI)

MS

2 Suspend

6 Resume (TLLI, RAI, SRN)

BSC

5 Suspend Ack

8 Resume Ack

MFS

3 Suspend (TLLI, RAI, suspend cause)

7 Resume

11 Routing Area Update Request

10 Channel Release

9 Resume Ack

SGSN

4 Suspend Ack (TLLI, RAI, SRN)

End of on-going TBF

DL LLC PDU are discarded

Normally, no more paging

messages sent by the SGSNEnd of the GSM call

The MS leaves the GSM dedicated mode

MS listen to “Channel Release” message content

MS enters in GSM

dedicated mode(on-going GPRS transfer

or not) P98c,P98d

▼Suspend Reference Number (SRN)

▼Alcatel BSS does not support the suspend/resume procedure in case of inter-BSC reselection.

▼In this case, MS must resume the GPRS service by sending a Routing Area Update Request message to the SGSN.▼Several timers are used to monitor the suspend/resume procedure between BSS and CS:

�-T3: control of the “Suspend Ack/Nack” messages on MFS side�-T4: control of the “Resume Ack/Nack” messages on MFS side�-T_GPRS_Resume: guarding timer for “Resume” procedure on BSC side

▼11) The MS resumes GPRS services by sending a Routing Area Update Request message in the following case:�- reception of a Channel Release with GPRS Resumption = NOK�- reception of a Channel Release without GPRS Resumption IE-- T3240 expiry

-P98c: NB_SUSPEND_REQ_FOR_DL_TBF-P98d: NB_SUSPEND_REQ_FOR_UL_TBF


1.83


▼ CS paging during packet transfer (class B MS):

� if the MS does not listen to the PCH channel:

�CS paging messages are lost if the duration of the packet transfer is higher than the duration of the repetition of CS paging messages

� if Gs interface is available:

�CS paging messages are sent through the PACCH channel

▼ PS paging during a GSM call (class B MS):

� the MS does not receive PS paging messages

▼If CS paging repetitions as viewed as a GSM QoS problem, the situation must be avoided.

▼A missed PS Paging during a CS call is less of a problem as the traffic is GPRS is under influence of the GSS capacity to store the PDU originated from external Packet Data Network. When the delay of transfer is not a requirement for the service, there is no direct impact of a missed MS Paging.▼



2. Radio Algorithms

▼Training objective: Describe the algorithms, parameters and indicators used on the radio interface


1.85

2 Radio Algorithms Session Presentation

▼ Objective: Describe the algorithms,parameters and indicators used onthe radio interface

▼ program:� 2.1 Allocation and de-allocation of radio resources� 2.2 TBF radio resource re-allocation� 2.3 Cell selection and reselection� 2.4 Up-link power control� 2.5 Coding scheme adaptation� 2.6 Radio link supervision




2 Radio Algorithms

2.1 Allocation and de-allocation of radio resources


1.87

2.1 Allocation/de-allocation of radio resources Traffic evaluation

▼ GPRS resource activation is a dynamic process applied on all PDCHs in the cell (several PDCH group in B7, one PDCH group in B6)

▼ Computation of Maximum and Minimum number of PDCHs available per cell based on Cell Load Evaluation

� Performed inside the BSC

� Long term evaluation: 1-2 minutes

� Other uses

� handover preparation in GSM

▼Maximum number of PDCH Groups per cell = 16, thanks to another B7 feature: “cell split over 2 BTS”

▼GSM handover causes using Traffic_Load information (directly or through the computation of ∆_HO_Margin)�HO12 (power budget)�HO23 (traffic HO)�HO21 (higher level in preferred band)�HO24 (general capture HO)


1.88

2.1 Allocation/de-allocation of radio resources Diagram

Cell_load_evaluation

Traffic_load_GPRS

evaluation

Update of Max

Number of PDCHs Available

AV_TRAFFIC_LOAD or AV_TRAFFIC_LOAD_GPRS

Load_state change?

Yes

No

« LOAD INDICATION » MESSAGE BSC ⇒⇒⇒⇒ MFS

▼At the reception of a “Channel Request” message from a MS for an UL TBF establishment with CCCH, a “Packet Channel Request” message from a MS for UL TBF establishment with PCCCH, of a LLC PDU from the SGSN, the MFS needs to execute the GPRS radio resource allocation for the MS in order to get:

�Specific GPRS radio resources (TFI, TAI, USFs)�TS or PDCH that must be asked to the BSC with BSCGP signaling procedure.

▼Upon reception of such a request, the BSC indicates the traffic capacity in GPRS to the MFS by forwarding “traffic load” indications that contains the Load_state of the BSC.▼Those message must be sent each time the load_state changed in the BSC after the previous request from the MFS.

▼Thanks to this “traffic Load” indication, the MFS is able to compute a value of the maximum number of PDCH available at the very moment of the TBF request.

BSC MFS

Allocation Request

De-allocation Request

Load Indication


1.89

2.1 Allocation/de-allocation of radio resources Cell Load Evaluation EN_DYN_PDCH_ADAPTATION=Disable

▼ Calculation of averages:

� OUPUT = non sliding average AV_TRAFFIC_LOAD representing the global load (circuit + packet) of the cell

� A_TRAFFIC_LOAD samples:

� 100 * (1 - Nb free TCH / Nb tot TCH)� Nb tot TCH: total number of TS in the cell for TCH and PDCH� Nb free TCH: number of free TS not used by a TCH or a

PDCH� 1 sample every TCH_INFO_PERIOD seconds

Time

Load

samples

TCH_INFO_PERIOD

A_Traffic_Load

Av_Traffic_Load (1)

A_Traffic_Load

Av_Traffic_Load (n)

N_Traffic_Load

▼The averaging window is the GSM one. Even so, the BSC runs a unique averaging mechanism for both GPRS and GSM traffic load purposes.

▼It is to be outlined that the computation mode of the AV_TRAFFIC_LOAD in B6.2 (for the evaluation of both Traffic load indication in GPRS and GSM) is similar the AV_TRAFFIC_LOAD_GPRS in B7, when EN_DYN_PDCH_ADAPTATION = disable.


1.90


▼ OUTPUT = Traffic_load_gprs which can take 3 values: low, high and indefinite

▼ Thresholds: HIGH_TRAFFIC_LOAD_GPRSLOW_TRAFFIC_LOAD_GPRS

▼ if Traffic_load_gprs = indefinite and :� the last N_TRAFFIC_LOAD averages AV_TRAFFIC_LOAD

(including the new one) verify AV_TRAFFIC_LOAD > HIGH_TRAFFIC_LOAD_GPRS then Traffic_load_gprs = high

� the last N_TRAFFIC_LOAD averages AV_TRAFFIC_LOAD (including the new one) verify AV_TRAFFIC_LOAD < LOW_TRAFFIC_LOAD_GPRS then Traffic_load_gprs = low

▼Note: you will note that IND_TRAFFIC_LOAD threshold (optional in GSM) is not used in GPRS.The change of load state from High (or Low) to indefinite is not required to be as fast as in GSM for the following reasons:

�The duration of a TBF being shorter than the duration of a CS call�The GPRS resource available are computed after considering the GSM traffic (the decision process including security procedures with the use of thresholds)


1.91


▼ if Traffic_load_gprs = low and the new average AV_TRAFFIC_LOAD verifies :

� AV_TRAFFIC_LOAD > HIGH_TRAFFIC_LOAD_GPRS

then Traffic_load_gprs = indefinite

▼ if Traffic_load_gprs = high and the new average AV_TRAFFIC_LOAD verifies :

� AV_TRAFFIC_LOAD < LOW_TRAFFIC_LOAD_GPRS

then Traffic_load_gprs = indefinite

▼Decision process similar to GSM one.


1.92

2.1 Allocation/de-allocation of radio resources Load Indication EN_DYN_PDCH_ADAPTATION=Disable

▼ When Traffic_load_gprs(n) ≠ Traffic_load_gprs(n-1)

� “Load Indication” sent to MFS (load state ;ø)

� if Traffic_load_GPRS = indefinite or low ⇒ Normal� if Traffic_load_GPRS = high ⇒ High

▼ Max number of PDCH available for GPRS traffic:

� MAX_PDCH if Load State = Normal

� MAX_PDCH_HIGH_LOAD if Load State = High

▼Message content refers to the BSCGP message « load indication ».


1.93

Time allowed:

10 minutes

2.1 Allocation/de-allocation of radio resources Exercise1 1/2

� Example with EN_DYN_PDCH_ADAPTATION = Disable

� Inputs:

– 4 TRX, total Nb of TS+PDCH=30

– MAX_PDCH=16– MAX_PDCH_HIGH_LOAD=2

– HIGH_TRAFFIC_LOAD_GPRS=80%

� for each of the following cases determine the maximum number of PDCH available for GPRS trafficCase (A): Nb_PDCH=8

AV_Traffic_Load_GPRS=70%

Case (B): Nb_PDCH=8AV_Traffic_Load_GPRS=90%

▼

SOLUTION:

Case (A):

Max number = MAX_PDCH = 16

Case (B):

Max number = MAX_PDCH_HIGH_LOAD = 2


1.94


▼ Case (A):

▼ Case (B):

HIGH

INDEFINITE

LOW

Max number of PDCH New

Traffic_load_GPRSPrevious Traffic_load_GPRS

INDEFINITE and the 2 last

AV_TRAFFIC_LOAD <

HIGH_TRAFFIC_LOAD_GPRS

HIGH


AV_TRAFFIC_LOAD >


LOW




1.95

2.1 Allocation/de-allocation of radio resources Cell Load Evaluation EN_DYN_PDCH_ADAPTATION=Enable

▼ Calculation of averages:

� non sliding average AV_Traffic_Load_GPRS representing the global load (circuit + packet) of the cell

� LOAD_EV_PERIOD_GPRS samples:

� 100 * (1 - Nb free TCH / Nb tot TCH)� Nb tot TCH: total number of TS in the cell for TCH and PDCH� Nb free TCH: number of free TS not used by a TCH or a

PDCH (TS disabled not computed)� 1 sample every TCH_INFO_PERIOD seconds

Time

Load

samples

TCH_INFO_PERIOD

LOAD_EV_Period_GPRS LOAD_EV_Period_GPRS

Av_Traffic_Load_GPRS(1)

▼Feature activation:�EN_DYN_PDCH_ADAPTATION=Enable�otherwise, B6.2 process is applied

▼It is to be noticed that the traffic evaluation in the BSC counts all the TS used i.e �The TS used for GSM traffic, the TCHs�The TS used for GPRS traffic, the GCHs


1.96

2.1 Allocation/de-allocation of radio resources Load Indication EN_DYN_PDCH_ADAPTATION=Enable

▼ Based on the calculation of the maximum number of PDCH to be allocated: MAX_PDCH_DYN (BSC)

▼ One threshold: HIGH_TRAFFIC_LOAD_GPRS

▼ Inputs: Nb_PDCH (nb of PDCH allocated) and AV_Traffic_Load_GPRS

▼ MAX_PDCH_DYN(BSC) =

MIN of {MAX_PDCH ;

max [ MAX_PDCH_HIGH_LOAD ;

nb_PDCH – (AV_Traffic_Load_GPRS –HIGH_TRAFFIC_LOAD_GPRS) x (nb_TS/100)] }

▼ When MAX_PDCH_DYN(n) ≠ MAX_PDCH_DYN(n-1)

� “Load Indication” sent to MFS: (load state ; MAX_PDCH_DYN(BSC))

� if MAX_PDCH_DYN = MAX_PDCH ⇒ Normal� if MAX_PDCH_DYN < MAX_PDCH ⇒ High

▼When EN_DYN_PDCH_ADAPTATION=Enable:�MAX_PDCH_DYN is re-computed every Load_EV_Period_GPRS x Tch_Info_Period seconds

▼In the above formula we have:�MAX_PDCH: in B7, takes the place the B6 parameters MAX_PDCH_GROUP and stands for the maximum number of PDCH that can be allocated in a cell according to the number of PDCH groups defined�MAX_PDCH_HIGH_LOAD: MAX number available in high load situation. Its meaning changes with the activation of the feature “smooth PDCH traffic adaptation to cell load variation”�Nb_PDCH: current number of PDCH allocated in the cell.�HIGH_TRAFFIC_LOAD_GPRS: threshold which determines that the amount of GPRS resource in use has become too high for the global traffic load of the cell. It is used for the computation of the maximum number of PDCH available for GPRS traffic.�Nb_TS: total number of TS (TCH and PDCH) available for traffic in the cell.


1.97

2.1 Allocation/de-allocation of radio resources Load Indication EN_DYN_PDCH_ADAPTATION=Enable

▼ Smooth PDCH allocation practice▼


1.98

Time allowed:

10 minutes

2.1 Allocation/de-allocation of radio resources Exercise2

� Example with EN_DYN_PDCH_ADAPTATION = Enable

� Inputs:








1.99

Time allowed:

15 minutes


� Throughput comparison when EN_DYN_PDCH_ADAPTATION = Enable and when EN_DYN_PDCH_ADAPTATION = Disable

� Inputs:

– MS1, MS2: class 4;

– Cell 2 TRXs ;CS+PS TS 14

– CS2 throughput (Kbit/s) 12.8

– MAX_PDCH 8

– MAX_PDCH_HIGH_LOAD 2

– HIGH_TRAFFIC_LOAD_GPRS (%) 70

– LOW_TRAFFIC_LOAD_GPRS (%) 20

– MIN_PDCH 0

� Fill up table next page

▼


1.100


DL transfer;CS2 MS2>

DL transfer;CS2 MS1 >

+1CS +3CS +1CS -1CS -2CS -1CS -1CS

CS TS allocated 0 0 1 1 4 4 5 5 4 4 2 2 1 1 0 0PS TS allocated

AV_TRAFFIC_LOAD_GPRS (%)

Max Nb of PS TS available (Dynamic PDCH adaptation=Disable)

max throughput per MS on air interface

CS TS allocated 0 0 1 1 4 4 5 5 4 4 2 2 1 1 0 0PS TS allocated

AV_TRAFFIC_LOAD_GPRS (%)

Max Nb of PS TS available (Dynamic PDCH adaptation=Enable)

max throughput per MS on air interface

▼


1.101

2.1 Allocation/de-allocation of radio resources Number of PDCH available for MFS

▼ Radio resources are dynamically allocated/de-allocated▼ Number of PDCH belongs to EN_DYN_PDCH_ADAPTATION

value and Load_state

▼ According to the formula seen before, we can assume that MAX_PDCH_HIGH_LOAD ≤ MAX_PDCH_DYN ≤ MAX_PDCH

Load Disable Enable

NORMAL MIN_PDCH ≤ Nb_PDCH ≤ MAX_PDCH MIN_PDCH ≤ Nb_PDCH ≤ MAX_PDCH

HIGH MIN_PDCH ≤ Nb_PDCH ≤ MAX_PDCH_HIGH_LOAD

If Nb_PDCH>MAX_PDCH_HIGH_LOAD

then PDCH pre-emption mechanisms

MIN_PDCH ≤ Nb_PDCH ≤ MAX_PDCH_DYN

If Nb_PDCH>MAX_PDCH_DYN

then PDCH pre-emption mechanisms

▼AJOUTER LA FORMULE


1.102

▼ PDCH group:

� pool of resources for GPRS on one TRX

� contains TS belonging to the same TRX and having the same radio configuration (same frequency or same FHS)

▼ B6.2 release: 1 PDCH group per cell because 1 TRX GPRS activated / cell

▼ B7: support of multiple PDCH groups per cell

� up to 16 PDCH groups per cell

� the operator can affect to each TRX a GPRS_PREF_MARKvalue

2.1 Allocation/de-allocation of radio resources PDCH group 1/2

▼In B7, any TRX should possibly support one PDCH group except for one case:▼Concentric cell or multi-band cell design, a PDCH group can NOT belong to the inner zone.

▼PDCH Group can be supported by both hopping or non-hopping TRX.

▼Only one MA (Mobile Allocation) is supported in a cell

▼GPRS_PREF_MARK gives the preference level of one PDCH group for TBFs and/or MPDCH allocation


1.103

▼ PDCH group priority computation by MFS

▼ It takes place when a choice has to be made between several PDCH groups

▼ It takes under consideration the following parameters:

PRIORITY

PDCH_Groupstate

ATeravailability

GPRS_PREF_MARK

OMC-R

BSC

2.1 Allocation/de-allocation of radio resources PDCH group 2/2

▼The PDCH group priority has to be taken into account:�for radio resource pre-allocation�when allocating radio resources for a TBF�when an Allocation Request is sent to the BSC (which includes an ordered list of candidate PDCH groups)�in the pre-emption process (BSC load indication) in the MFS

▼The highest priority will be given to PDCH groups�not carried by dual-rate TRX�carried by TRX with the lowest TRX id�which are not in transmission congestion state


1.104

2.1 Allocation/de-allocation of radio resources PDCH de-allocation 1/3

▼ Two cases for the de-allocation of a PDCH:

� high load indication sent by the BSC to the MFS:

� global (circuit + packet) load elevated in the cell�MFS triggers pre-emption mechanisms

� GPRS low load :

�SPDCH is in empty state (no traffic in both UL and DL)�MPDCH is in empty state

▼This rules applies as well on counters generated by the MFS about dynamically PDCH allocation. In other words, the static resource must not be left aside when the computation of total GPRS radio resources is involved.▼The PDCH release mechanisms consider the most significant release criterion:▼Please remember that allocation and de-allocation mechanisms are considered for PDCH dynamically allocated and do not apply to PDCH constantly dedicated to GPRS traffic.

�When there is no GPRS traffic, the next emergency is likely to be a resume of the GPRS traffic�When there is a high traffic load, the next emergency is likely to be additional GSM incoming calls


1.105


▼ GPRS low load on SPDCH:

� the MFS de-allocates inactive PDCH as long as: Nb_PDCH > MIN_PDCH

� inactive PDCH are de-allocated after a delay

� T_PDCH_INACTIVITY for any PDCH,� T_PDCH_INACTIVITY_LAST for the last PDCH

dynamically allocated

▼Those mechanisms aim at stabilizing the pool of TS reserve for GPRS (especially for the MPDCH which establishment must be very fast)

▼T_PDCH_INACTIVITY = 10 s by default but settable at OMC-R▼T PDCH_INACTIVITY_LAST = 20 s by default but settable at OMC-R


1.106


▼ GPRS low load on MPDCH:

� Secondary MPDCH:

� T_MPDCH_S_MIN_ACTIV activated on each secondary inactive MPDCH

�Release triggered only when T_MPDCH_S_MIN_ACTIVhas expired (except fast pre-emption mechanism)

�De-allocation of the MPDCH with the highest index within the first PDCH group in the ordered list GPRS low load on MPDCH.

� Primary MPDCH

� If MIN_MPDCH=0�When there is no GPRS traffic for

T_MPDCH_P_MIN_ACTIV seconds

▼T_MPDCH_P_MIN_ACTIV = 5mn (default value)▼T_MPDCH_S_MIN_ACTIV = 5mn (default value)▼These two timers are not settable at OMC-R.

▼NB: when no MPDCH is established in the cell, BS_PAG_BLKS_RES is no longer useful. Refer to the use of BS_AG_BLKS_RES in GMS and GPRS for the B6.2 release.


1.107

2.1 Allocation/de-allocation of radio resources PDCH de-allocation: pre-emption mechanism 1/3

▼ In High load situation, 2 pre-emption mechanisms are used by MFS:

� MFS marks allocated PDCH above MAX_PDCH_DYN (or MAX_PDCH_HIGH_LOAD)

� Timer T_PDCH_PREEMPTION is started

�MFS triggers PDCH soft pre-emption

� At expiry of T_PDCH_PREEMPTION:

�MFS triggers PDCH fast pre-emption

▼Soft preemption was already provided in B6.2.▼The fast preemption is made possible only in B7 thanks to the TBF resource re-allocation mechanisms which did NOT exist in B6.2▼The only way to avoid a situation where the fast pre-emption would be necessary in B6.2 is the configuration of the MAX_PDCH_HIGH_LOAD and MAX_PDCH_GROUP according to GSM traffic information and GPRS traffic forecasts.

▼T_PDCH_PREEMPTION = 20 s (default but settable at OMC-R)


1.108


▼ Soft pre-emption:� MFS marks first SPDCH� Then the secondary MPDCH (when the number of SPDCH

marked is lower than the number of PDCH to be de-allocated)

� Finally the primary MPDCH (if MIN_MPDCH=0)� To mark SPDCH and secondary MPDCH, MFS classifies de

PDCH groups according to:�PDCH groups with the lowest GPRS_PREF_MARK

value have the highest pre-emption priority� then PDCH groups carried by Dual Rate TRX� the PDCH groups carried by TRX with the highest

TRXid� inside the PDCH group, SPDCH and secondary

MPDCH with the highest index are marked first

▼Soft pre-emption: MFS waits for all the TBFs to end on the PDCH before de-allocating the TS.▼To shorten the soft pre-emption duration, the operator must minimize the TBF multiplexing per PDCH, i.e configure properly the MAX_XX_TBF_SPDCH▼The highest the value is, the longer the soft pre-emption can take.


1.109


▼ Fast pre-emption:

� At expiry of T_PDCH_PREEMPTION, the MFS de-allocates TS before TBF ending, having the following impacts:

� TBF whose PACCH is impacted (the corresponding PDCH is marked) are released.� MFS sends a “Packet TBF release” message with

polling (i.e acknowledgement is requested)

� TBF whose PACCH is not impacted are not released but have a throughput reduction.� MFS sends a “Packet PDCH release” message

indicating the pre-empted PDCHs

▼The TBFs whose throughput is reduced match the requirement for TBF re-allocation process (see the trigger condition in subchapter 2.2 “TBF resource re-allocation”)▼The PACCHs blocks are the most important blocks to monitor. Many GPRS features ensure that PACCH blocks are always monitored by MS:

�The PTCCH is carried by the same PDCH than the PACCH,�The RXLEV measurements for the power control and CS adaptation are made on the PDCH that carries the PACCH blocks,�Some RLS mechanisms are based on whether or not the MS is able to send or listen to PACCH blocks.


1.110

2.1 Allocation/de-allocation of radio resources Thresholds and parameters 1/5

▼ MAX_PDCH_HIGH_LOAD:

�maximum number of PDCH per cell that can be allocated for GPRS when � the BSC has indicated a high load situation for the

cell� EN_DYN_PDCH_ADAPTATION = Disable

�min: 0, max: 5, def: 1

▼MAX_PDCH_HIGH_LOAD is a key factor when one wants to insure a minimum GPRS service in a zone likely to be congested because of GSM traffic load.▼In B6.2 the range value for this parameters is 0 to 8. The range was wider because the GPRS could be activated on a unique TRX per cell. In B7, the GPRS traffic can be activated on up to 16 TRX per cell, so 16 PDCH GROUPS.▼It is obvious to say that 8 x 1 < 5 x 16


1.111


▼ Cell parameters:

� MIN_PDCH: minimum number of PDCH that can be permanently allocated in the cellfrom 0 to 127, default = 0

� MIN_MPDCH: minimum number of Master PDCH that can be permanently allocated in the cell0 or 1

� MAX_PDCH: maximum number of PDCH that can be allocated in the cellfrom 0 to 127

▼MAX_PDCH in B7 takes the place of the MAX_PDCH_GROUP in B6.2. The MAX_PDCH is in fact the equivalent of a “MAX_PDCH_GROUP x Nb of PDCH_GROUP in the cell”▼MIN_PDCH must be taken into account when computing the total number of PDCH used when it is not included in the trigger conditions of counters like “maximum number of PDCH dynamically allocated”, etc…

▼MAX_PDCH_DYN must never exceed MAX_PDCH value (refer to calculation slide 81)

▼MIN_MPDCH can be set to 1 only if MIN_PDCH≠0


1.112


▼ 1/ Cell with 2 TRX,14 TS available for traffic (1 CBCH,1 SDCCH)MAX_PDCH=8, MAX_PDCH_HIGH_LOAD =2HIGH_T_L_GPRS = 50%, LOW_T_L_GPRS = 20%

� Considering no CS traffic, what happens if you increase the GPRS traffic?

2/ cell with 2 TRX,

14 TS available for traffic (1 CBCH,1 SDCCH)

MAX_PDCH=8, MAX_PDCH_HIGH_LOAD =2

HIGH_T_L_GPRS = 80%, LOW_T_L_GPRS = 60%

Considering the graph below, what happens

when the CS traffic is increasing?Time allowed:

5 minutes

© Alcatel University -8AS 90200 0409 VH ZZA Ed.05Page 1.113

1.113


100 93 21 14 7 0 0

NB TS GSM

57

50

43

36

29

21

14

7

0

100 93 79 71 64 MAX_PDCH_GROUP

100 93 71 64 57 7

100 93 64 57 50 6

100 93 57 50 43 5

100 93 50 43 36 4

100 93 43 36 29 3

100 93 36 29 21 MAX_PDCH_H_L

100 93

86 79 71

86

86 79

64 57 50

86

86 79

86 79 71

79 71 64

71 64 57

43 36 29

86

86 79

86 79 71

79 71 64

71 64 57

64 57 50

57 50 43

50 43 36 29 21 14 1

14 13 12 11 10 9 8 7 6 5 4 3 2 1 NB TS GPRS

ZONE A

ZONE B

ZONE C

▼SOLUTION:�ZONE A: de-allocation of PDCH down to MAX_PDCH_HIGH_LOAD. The cell load is then inferior to LOW_TRAFFIC_LOAD_GPRS. New PDCH allocation available to a maximum number of MAX_PDCH_GROUP = PING-PONG

�ZONE B: de-allocation of PDCH down to MAX_PDCH_HIGH_LOAD. The cell load is still superior to LOW_TRAFFIC_LOAD_GPRS. No further GPRS allocation possible (unless the CS traffic drops)

�ZONE C: No de-allocation possible because the total number of PDCH is still inferior or equal to MIN_PDCH_HIGH_LOAD


1.114


▼ Recommended Rule 1:

� HIGH_TRAFFIC_LOAD_GPRS > 100 * (MAX_PDCH/ Nb tot TCH)

� The high load threshold in the BSC has to be higher than the GPRS maximum traffic

▼ Recommended Rule 2:

� HIGH_TRAFFIC_LOAD_GPRS -LOW_TRAFFIC_LOAD_GPRS > 100 * [(MAX_PDCH -MAX_PDCH_HIGH_LOAD) / Nb tot TCH]

� to avoid a oscillating phenomenon (“ping-pong” situation) which can occur if the MFS pre-emption process triggers a return to the BSC “normal load” situation

▼Recommended Rule 1:�i.e some CS traffic is needed to be in « high load » situation in order to avoid reaching this state only with GPRS traffic�This rule has a little number of exceptions only (specific TRX configuration). Its purpose is “the BSC must never be in high load situation in one cell where GPRS traffic only is offered”

▼Recommended Rule 2:�if this rule is not verified there is not always a ping-pong situation depending on the possible traffic states�If the condition above is not fulfilled, after de-allocation process to MAX_PDCH_HIGH_LOAD PDCHs because of a high_load situation, the TCH+PDCH load drops under the LOW_TRAFFIC_LOAD threshold. After LOAD_EV_PERIOD_GPRS seconds, the load will switch back into Normal Load and the PDCH allocation will therefore be possible.


1.115

2.1 Allocation/de-allocation of radio resources TBF resource allocation 1/11

▼ Number of TBF per PDCH, parameters:

N_TBF_PER_SPDCH

MAX_XX_TBF_SPDCH

PDCHbusy

PDCH fullNo additional TBF canbe established on the PDCH

PDCHactive

PDCHinactive

▼MAX_XX_TBF_PDCH stands for:�MAX_UL_TBF_PDCH�MAX_DL_TBF_PDCH

▼PDCH inactive: PDCH pre-allocated or allocated but not carrying any TBF


1.116


▼ Number of TBF per PDCH, parameters:

� MAX_UL_TBF_SPDCH:

� maximum number of UL TBF per slave PDCH� min: 1, max: 6, def: 5

� MAX_DL_TBF_SPDCH:

� maximum number of DL TBF per slave PDCH� min: 1, max: 10, def: 5

� N_TBF_PER_SPDCH:

� threshold used to determine when a PDCH is busy� if the number of TBF supported by the PDCH in one direction is

above this threshold then the MFS serves new TBF preferably using other PDCH and possibly requesting additional resources to the BSC

� min: 0, max: 5, def: 2

▼The multiplexing capacity in UL and DL belongs to the GPRS radio resource availability. The UL multiplexing capacity is USF limited when the DL multiplexing capacity should be TAI limited.

▼In fact the overall UL/DL multiplexing capacity on a unique PDCH is TAI limited, as UE with UL TBF as well as UE with DL TBF must monitor their timing advance by sending Access Bursts in UL.

▼16 values are available for the TAI, so 16 UE in UL+DL can be multiplexed on a unique PDCH.

▼The number of USF available for traffic in B7 is 6 (8 possible values – 1 for no emission – 1 for master)


1.117


▼ Number of PDCH per TBF, parameters:

� MAX_PDCH_PER_TBF:

�maximum number of PDCH allocated to a TBF�min: 1, max: 5, def: 5

▼This parameter gives the capacity to the operator to limit the MS resource request to a maximum tolerable value for a cell. This feature enable to cope with TRX shortage in some cells especially when the MS QoS demand requires a great number of TS in order to achieve a sufficient throughput.

▼Why a max value of 5?�In order to be able to offer service at 30 Kbit/s in good radio conditions (CS2 is used) with a decent number of user multiplexed (2 TBF per PDCH).


1.118


Determination of the number of

requested PDCH

Concurrent TBF

already established ?

Candidate allocations evaluation

and sorting

PDCH group priority

calculation

NOK :

UL : reject

DL : queueing

No

More PDCH needed ?

No

Scoring function

Yes Scoring function and candidate

allocation reservation

Request of additional PDCH or

transmission resources

YesTest of concurrent constraints

NOK :

UL : reject

DL : queueingOK

▼For the PDCH Group priority classification in MFS, refer to previous slide.

▼NB: it must be noted that in B7, the MFS TS allocation is proceeded from the lowest TS number to the highest when the TS allocation in the BSC for CS traffic is made oppositely.

MFS allocation

proceeding

BSC allocation

proceeding

TS0 TS1 TS6 TS7


1.119


▼ Step 1: MFS determines the required number of TS in the direction of the request and in the concurrent direction:� n_MS_req = min (n_MS_cap, MAX_PDCH_PER_TBF)� main direction of the application (Bias transfer determination

function)� If multi-slot class of the MS is unknown, then a default multi-

slot class is assumed:�UL = use of the parameter

GPRS_MULTISOLT_CLASS_DEF_VALUE� the multi-slot class 1+1 is assumed in case of DL TBF

established

Determination of then number of

Requested PDCH

▼Cases where the Multi-slot class of the MS can happen to be unknown:�UL TBF establishment one phase access which leads to a single PDCH allocation�This default allocation will be further adapted with the TBF re-allocation mechanisms (refer to sub-chapter 2.2 “TBF resource re-allocation”

�No QoS indication in the BSSGP header of the DL PDU coming from the SGSN, a first DL TBF allocation is made with the multi-slot class 1+1

▼Bias transfer determination:�Feature that aims at determining the main direction of a service based on the volume of the data transmitted for one MS in both directions. If the transfer is DL biased, the next DL TBF establishment has a higher priority than the next UL TBF establishment. The radio resources must then be offered accordingly


1.120


▼ Step 2: the MFS analyses the constraints due to a possible concurrent TBF in the opposite direction: some TS can be unusable

� In case of concurrent constraints, the scoring function is used if several allocations over several PDCH Groups are candidates

� Scoring function will prefer to allocate on the TSs carrying thelowest number of TBFs established in

� the direction of the request� the concurrent direction (considered on all the PDCHs of the

allocation)

Concurrent TBF

Already established?

Yes

No

Analysis of constraints

on concurrent TBFs

OKNOK = reject in UL

queue in DL

▼Concurrent TBF issue:� the acknowledgment messages with the BSS carried by PACCH are always in the opposite direction of a transfer (TBF), so the MFS must make sure that the acknowledgment blocks won’t damage the QoS of the TBF served in the opposite direction�the acknowledgement mechanisms with distant servers often imply establishment of another TBF in the opposite direction for the same MS. For a easier TS management by the MS,

▼Refer to slide 120 for the scoring function procedure


1.121


▼ Step 2a: MFS sorts the list of all the PDCH group of the cell according to their GPRS_PREF_MARK

� MFS tries to satisfy the TBF demand using a PDCH group with the highest GPRS_PREF_MARK

� A PDCH group with a GPRS_PREF_MARK=0 can NOT be used for resource allocation

PDCH Group

Priority calculation

▼The GPRS_PREF_MARK mechanism for GPRS radio resource allocation is new with the B7,as in B6.2 only one TRX could be GPRS activated.


1.122


▼ Step3: This step implies several allocation mode capabilities, which belongs to:

� the number of PDCH already allocated

� the number of PDCH that could potentially be allocated to MFS

� the state of the PDCH encountered (active, busy, full)

Candidate allocations evaluation

Sorting process

NOK = reject in ULqueue in DL

▼The details of this sorting process are displayed in the next slide.


1.123


▼ If all the candidate allocations with highest priority require additional PDCH or transmission resources a request is sent to the BSC.

� Before requesting more PDCH, the preferred candidate allocation is reserved by the MFS

� If new PDCH are allocated, then the scoring function will be used to select the best candidate allocation on the PDCH group where more PDCHs were allocated

� If no new PDCH was allocated, then the scoring function is used to select the best candidate allocation among all PDCH groups

More PDCH needed?Scoring function and candidate

allocation reservation

Request of additional PDCH ortransmission resources

Scoring function

Yes

No


1.124


▼ the best candidate evaluation can be described as follows:A/ candidate allocations with the highest number of non-busy

PDCH in the biased direction of the application are preferredB/ candidate allocations with the highest number of non-full

PDCH in the biased direction of application are preferred C/ candidate allocations with the highest number of non-busy

PDCH in the opposite direction to the biased one are preferred

D/ candidate allocations with the highest number of non-full PDCH in the opposite direction to the biased one are preferred

E/ candidate allocations on the PDCH group with the highest priority are preferred

▼The best candidate evaluation aims at optimizing the temporary use of GPRS radio resources for a UE which means that:

�On the UE standpoint, the TBF is a single transfer in one direction among the numerous TBF UL/DL that are necessary for the entire duration of a service. The candidate evaluation uses the BIAS information to have to most reliable view of the service for the average radio resource demand in the main direction, which must always been optimized.

�On the MFS standpoint, considering that UEs switch regularly from UL to DL TBF, it is important to make sure that when the UE will establish a TBL in the opposite direction, it can be allocated common radio resources (same PDCH, use of the same TAI, use of the same PDCH for the PACCH blocks, allocation on the same TRX…) to make the UE work easier. This is why the concurrent direction is systematically checked

▼Finally, to respect the operator preference to serve the GPRS traffic on specific TRX, the GPRS_PREF_MARK is checked


1.125


▼ Scoring function description:F0

If the MS has already 1 or 2 TBFs established, preference is given to the

candidate TS allocations which do not require reallocating the on-going TBF(s)

F1 PDCHs are preferably chosen on a PDCH group which is not in transmission

congestion rate Only one PDCH group in B6.2

F2 PDCHs are preferably chosen on a NON Dual Rate PDCH group Only one PDCH group in B6.2

F3

If number of allocated PDCHs in the cell > MIN_PDCH and there is at least one

non-busy PDCH already established in both directions, combinations which do

not include the PDCH which has the highest index of the allocated PDCH,

neither in the direction of the request nor in the opposite direction, are preferred.

F4 Allocations with the lowest number of established TBFs in the biased direction

(to offer the best throughput) are preferred.

In B7.2, the load in the concurrent direction

is considered for all the PDCH of the

concurrent allocation

In B6.2, only the PDCH in common to both

directions are considered

F5

Allocations with the lowest number of established TBFs in the opposite

direction to the bias one (to offer the best throughput in the opposite direction

too) are preferred

F6 Allocations on the lowest TRX Id are preferred Only one PDCH group in B6.2

F7 The allocation having the PDCH with the lowest index is finally chosen

In B6.2, the allocation is preferably done in

the centre of the PDCH group

In B7.2, the allocation is preferably done on

the left most PDCH

▼In the scoring function, a list of candidate allocations is established. The final allocation within those candidates

▼The purpose of the criterion F3 is to release as soon as possible the PDCH with the highest index. ▼F4 and F5 are counted as the sum of the number of established TBFs for each PDCH of the candidate allocation in the considered direction (biased or opposite to the biased).


1.126

Time allowed:

15 minutes


� Scenario 1: Allocation on non BCCH TRX– UL TBFs 1 to 11 are established

one after the other– It is assumed that a concurrent DL

TBF is established after the UL, and before the next UL

– All transfers are deemed DL biased� Objective: Fill up the initial TBF

allocation TS mapping UL/DL


1.127

Time allowed:

15 minutes


� Inputs:– Non-BCCH TRX, 1 unique PDCH group– MIN_MPDCH = 1 (PDCHs 1 to 7 are

available for GPRS traffic)– N_TBF_PER_PDCH = 1– MAX_XX_TBF_PER_PDCH = 5– MS GPRS multi-slot class is given below:

(3+1)C simplex configuration

▼In the picture above, the underlined Time-slot represents the TS where the PACCH is located.


1.128


DL

UL

Master 1

1 1 1Master

2

2 2 2

34 5

6

4 4 4 3

3

3

7

8 9

5 55

6

6

68

8

8

9

9

9

7

7

710

10

11

11

10 11



1.129

2.1 Allocation/de-allocation of radio resources Sessions/Transferts, QoS indicators 1/5

▼ Transfer

� Bi-directional exchange of RLC data blocks between the MS and the BSS

� The bias of a transfer is the main direction of the transfer in terms of throughput

▼ Session

� Uninterrupted sequence of data transfers between the MS and the BSS

� begin: a UL or DL TBF is established for an MS in PIM� on-going: at least one TBF is established� end: the last on-going UL or DL TBF is released

▼ A session never ends when a DL TBF is released but at the expiry of T3192 timer in case there is no UL TBF on-going in the meantime.

▼ The Alcatel BSS regularly determines the bias of the on-going transfer at MS if the Bias Determination feature is enabled. � The number of octets transferred in both directions is counted and averaged for that purpose.

▼ If disabled the bias remains the one chosen at the establishment of the TBF.� By default a transfer is deemed downlink biased (at first establishment), except in case the MS context is created upon receipt of

an UL two phase access, in which case the bias is set to uplink.


1.130


▼ Sessions and transfers: introduction

Session

Transfer

Number of sessions

Average duration

cumulated time MS engaged in DL/UL biased transfers

% of time DL/UL TBF are granted the max nb of PDCH they supportand the corresponding MS are engaged in DL/UL biased transfers

Average number of DL/UL TBF per session


1.131


▼ Sessions and transfers: indicators = f(counters)

GPRS sessions

Number of GPRS sessions P413

Average duration of a session ((P419 + P420) / 10) / P413

Downlink Uplink

Average number of

DL TBF established

per session

(P90a +P90b + P90c +

P90d + P90e + P90f) /

P413

Average number of

UL TBF established

per session

(P30a + P30b +P30c) /

P413


1.132


▼ Sessions and transfers: indicators = f(counters)

Bias of the ongoing transfers

Downlink Uplink

Cumulative time MS

are engaged in DL

biased transfers

P419 / 10 Cumulative time MS

are engaged in UL

biased transfers

P420 / 10

Donwlink biaised ratio P419 / (P419 + P420) Uplink biaised ratio P420 / (P419 + P420)

Cumulative time MS

are served by DL TBF

and engaged in DL

biased transfers

P411/10 Cumulative time MS

are served by UL TBF

and engaged in UL

biased transfers

P412/10

Cumulative time DL

TBF are granted the

maximum number of

PDCH they support and

the corresponding MS

are engaged in DL

biased transfers

P409/10 Cumulative time UL

TBF are granted the

maximum number of

PDCH they support and

the corresponding MS

are engaged in UL

biased transfers

P410/10

% of time DL TBF are

granted the maximum

number of PDCH they

support and the

corresponding MS are

engaged in DL biased

transfers

P409 / P411 % of time UL TBF are

granted the maximum

number of PDCH they

support and the

corresponding MS are

engaged in UL biased

transfers

P410 / P412

▼ Determination of the Bias:� Uplink : when a first UL TBF is established using the 2-phase access on a CCCH or PCCCH� Downlink : in any other case


1.133


DL session

0

50000

100000

150000

200000

250000

14 /08 /20

03

16 /08 /20

03

18 /08 /20

03

20 /08 /20

03

22 /08 /20

03

24 /08 /20

03

26 /08 /20

03

28 /08 /20

03

30 /08 /20

03

01 /09 /20

03

03 /09 /20

03

05 /09 /20

03

07 /09 /20

03

09 /09 /20

03

11 /09 /20

03

13 /09 /20

03

86

88

90

92

94

96

98

100

102

Time Opt alloc

DL Time bias

Time bias

%Time OptAlloc

UL session

0

1000

2000

3000

4000

5000

6000

14 /08 /20

03

16 /08 /20

03

18 /08 /20

03

20 /08 /20

03

22 /08 /20

03

24 /08 /20

03

26 /08 /20

03

28 /08 /20

03

30 /08 /20

03

01 /09 /20

03

03 /09 /20

03

05 /09 /20

03

07 /09 /20

03

09 /09 /20

03

11 /09 /20

03

13 /09 /20

03

0

20

40

60

80

100

120

Time Opt alloc

UL Time bias

Time bias

%Time OptAlloc

▼ Typical values of DL TBF optimal allocation time rate (without resource re-allocation):� Without congestion (GSM+GPRS): 93%, 94%, 95%, 96%� With congestion: 79.5%

▼ UL TBF optimal allocation time rate can be biased, due to the restriction on P29.▼ However, on small area, it can give the following typical values:

� Without congestion (GSM+GPRS): 68.5%, 76%, 92%, 98%� With congestion: 98%

➨ These typical values are highly depend on the penetration rate of class 9 or class 10 mobiles (mobiles able to use 2 TS on UL path).


1.134

2.1 Allocation/de-allocation of radio resources PDCH resources, QoS indicators 1/4

▼ GPRS radio resources = PDCH: introduction

PDCH usage

Smooth PDCH adaptation to cell load variationEN_DYN_PDCH_ADAPTATION = enable

Average, max, min number of established PDCH

cumulated establishment time

PDCH dynamic establishment success rate

% time during which the cell is in high load situation

MAX_PDCH_DYN variable follow-up

Soft pre-emption

▼ A PDCH is established when it is allocated on a radio point of view and for which an Ater (GCH) resource has been allocated

▼ Pre-allocated PDCH (MIN_PDCH) are not established if not used for TBF (no GCH allocated)


1.135


▼ GPRS radio resources = PDCH: indicators = f(counters)

Soft pre-emption

Number of PDCH released after having been

marked by the soft pre-emption procedure

P417

Number of times the soft pre-emption procedure

is called

P418

Average number of UL+DL TBF candidates to a

T1 reallocation per PDCH released after having

been marked

(P403a + P404a) / P417

PDCH usage

Average number of established PDCH in the cell P149 / 10

Maximum number of established PDCH in the cell P150

Minimum number of established PDCH in the cell P427

Cumulated time during which the PDCH are established for the cell P38 / 10

PDCH dynamic establishment success rate P19 / P54

% of time during which the cell is in high load situation (P1 / 10) / GP

▼ The cell is in high load situation if MAX_PDCH_DYN is equal to MAX_PDCH - Number of MPDCH


1.136


▼ GPRS radio resources = PDCH: indicators = f(counters)

MIN_PDCH

MAX_PDCH_HIGH_LOAD

MAX_PDCH_DYN

MAX_PDCH

number of timeslots in the cell

MAX_PDCH_DYN variable follow-up

MAX_PDCH_DYN value integrated over time P414 / 10

Average value of MAX_PDCH_DYN (P414 / 10) / GP

Maximum value of MAX_PDCH_DYN P415

Minimum value of MAX_PDCH_DYN P416

MAX_PDCH_DYN maximum range P415 - P416

MAX_PDCH_DYN reduction rate (PERIOD*(MAX_PDCH - P414/10)) /

(PERIOD*MAX_PDCH)


1.137


PDCH dynamic allocation load report

0

1

2

3

4

5

6

7

8

9

14 /08 /20

03

16 /08 /20

03

18 /08 /20

03

20 /08 /20

03

22 /08 /20

03

24 /08 /20

03

26 /08 /20

03

28 /08 /20

03

30 /08 /20

03

01 /09 /20

03

03 /09 /20

03

05 /09 /20

03

07 /09 /20

03

09 /09 /20

03

11 /09 /20

03

13 /09 /20

03

0

0.10.20.30.40.50.60.70.80.91

Alloc max

% BSC Highload

Dyn dealloc procedure

0

1

2

3

4

5

6

14 /08 /20

03

16 /08 /20

03

18 /08 /20

03

20 /08 /20

03

22 /08 /20

03

24 /08 /20

03

26 /08 /20

03

28 /08 /20

03

30 /08 /20

03

01 /09 /20

03

03 /09 /20

03

05 /09 /20

03

07 /09 /20

03

09 /09 /20

03

11 /09 /20

03

13 /09 /20

03

0

5

10

15

20

25

30

35

T1 Success

RR Softpreempt% Reduction

▼ Typical reference values of BSC high load time rate is:� Without congestion (GSM+GPRS): 0.4%, 0.6%� With some congestion: 5.5%, 4.6%� With high level of congestion: 26%


1.138

2.1 Allocation/de-allocation of radio resources MPDCH resources, QoS indicators 1/3

▼ GPRS radio resources = MPDCH: introduction

MPDCH usage

MPDCH signaling traffic

Average, max number of established MPDCH (prim + sec)

cumulated establishment time (primary)

MPDCH establishment requests (primary)MPDCH alloc and de-alloc requests (secondary)

Time during which a MPDCH cannot be established(prim + sec)

PPCH

PRACH

PACCH

PAGCH


1.139


▼ GPRS radio resources = MPDCH: indicators = f(counters)

MPDCH allocation

Average number of established MPDCH (primary and secondary) P93 / 10

Maximum number of established MPDCH (primary and secondary) P94

Cumulative time during which primary MPDCH is established P37 / 10

Primary MPDCH time occupancy ((P37 / 10)* 60) / GP

Number of primary MPDCH establishment requests P51a

Number of secondary MPDCH dynamic allocation and deallocation requests P51b

Time during which a primary MPDCH cannot be established P395a / 10

% of time during which a primary MPDCH cannot be established (P395a / 10) / GP

Time during which a secondary MPDCH cannot be established P395b / 10

% of time during which a secondary MPDCH cannot be established (P395b / 10) / GP


1.140


▼ GPRS radio resources = MPDCH: indicators = f(counters)

MPDCH signalling traffic

Dedicated PPCH signalling load on all the existing MPDCH P61

Number of PACKET PAGING REQUEST for PS paging sent

to the MS on PPCH

P61a

Number of PACKET PAGING REQUEST for CS paging sent

to the MS on PPCH

P61b

Number of Packet DL assignment messages on PPCH P61 - 0.5*P61a - 0.5*P61b

Occupancy rate of PS paging messages on PPCH load 0.5 * P61a / P61

Occupancy rate of Packet DL assignment messages on PPCH (P61 - 0.5*P61a - 0.5*P61b) / P61

PRACH signalling load on all the existing MPDCH P399

Dedicated PAGCH signalling load on all the existing MPDCH P400

UL PACCH signalling load on all the existing MPDCH P401

▼ Factor of 0.5 comes from the fact that a PACKET PAGING REQUEST can contain 2 paging messages (like in GSM between Paging Commands and Paging Requests)



2 Radio Algorithms

2.2 TBF radio resource re-allocation


1.142

2.2 TBF radio resource re-allocation Principle 1/3

▼ Radio resource re-allocation procedure aimed at

� reducing the impact of the fast PDCH pre-emption, which can

� lead to a TBF drop� lead to a throughput diminution� impact the GPRS QoS

� improving a sub-optimal TBF initial allocation

▼ Feature enabled by the parameter EN_RES_REALLOCATION

▼ T_PDCH_PREEMPTION timer must be set to a value ≠ 0

▼ Two types of trigger conditions

� Immediate resource re-allocation attempt

� Subsequent resource re-allocation attempt

▼When T_PDCH_PREEMPTION=0 (immediate fast preemption), there is no time to perform a re-allocation process.▼The TBF radio resource re-allocation is new in B7 and was not available in B6.2▼It aims at optimizing as fast as often as possible the radio resources allocated for a TBF according to the MS request. In B6.2, when the requested radio resources (mainly the number of PDCH) is not available, a smaller number of PDCH is allocated for the entire duration of the TBF. The MS request is reassessed at the next TBF establishment request

▼In B7, if the number of radio resource allocated at the beginning of the TBF does not match the MS request, it will be reassessed during the TBF. This is a great benefit of the B7 especially for long TBFs


1.143


▼ Immediate re-allocation cases:� soft PDCH pre-emption process affecting the PACCH of the TBF

(trigger T1)� TBF establishment whereas concurrence constraints do not allow

an optimal initial allocation (trigger T2)� expiry of timer T_CANDIDATE_TBF_REALLOC (trigger T3)

▼ Subsequent re-allocation cases:� number of PDCHs allocated for a TBF is lower than could be

supported by the MS multi-slot class, when the latter is known at establishment time (event E1)

� fast PDCH pre-emption process reducing the throughput granted to a TBF (event E2)

� the BSS gets MS multi-slot class after initial allocation; at least one on-going TBF has a sub-optimal PDCH allocation (event E3)

▼To be candidate to subsequent resource re-allocation, the following conditions have to be met:�the TBF established in the biased direction (see next slide) is marked with “subsequent allocation”�more than N_CANDIDATE_FOR_REALLOC octets have been transferred for the TBF in the biased direction�T3192 is not running (specific to UL TBF re-allocation when T3192 is running for the DL TBF)

▼The subsequent re-allocation is done whether or not the TBF corresponds to the bias transfer direction of the MS.


1.144


▼ On going transfer bias determination:

� aim at determining the main direction for a MS involved in UL and DL transfers

� in order to reallocate radio resource for the main direction

▼ Default value:

� the transfer is deemed DL biased

� at first establishment for an UL TBF 2-phase access

� the transfer is deemed UL biased

� in any other case

▼ Determination on number of bytes transferred in both directions and averaged

� Activation with N_BIAS_DETERMINATION ≠ 0 kbyte

▼General purpose of the bias determination:�GPRS MS are often involved in consecutive UL/DL transfers for a unique service.� The Bias determination must identify the direction of the main flow of data (based on the quantity of data exchanged at a specific moment) in order to prioritize

�The initial allocation on considering the biased direction (refer to sub-chapter 2.1 “TBF resource allocation”)� the re-allocation process on the main direction (likely to carry the useful data)

▼Before being able to determine the biased direction on “quantity of data exchanged”, the MFS refers to the QoS information contained the the transfer request:

�DL TBF:MFS checks the BSSG header�UL TBF: UE must do a 2 phase UL TBF establishment or UL TBF establishment with PRACH

▼ N_BIAS_DETERMINATION = 1 kbyte (default value). It cannot be set at the OMC-R level.


1.145

Time allowed:

5 minutes

2.2 TBF radio resource re-allocation Exercise 1/3

� Scenario 2: Re-allocation case– Based on the previous exercise– EN_RES_re-allocation = 4

(resource re-allocation is enabled only for T3)

– TBFs 10 and 11 in DL are marked sub-optimal

– All transfers are deemed DL biased– The TBFs 1, 2, 3, 6, 7 and 9 are

released in both UL and DL� Perform resource re-allocation after

T_CANDIDATE_TBF_REALLOC expiry, assuming MS 10 has higher priority for re-allocation than MS 11

▼ Priority between MS candidate for re-allocation due to trigger T3:� first: list of MS which are UL biased� second: list of MS which are DL biased

�the candidate MSs are processed according to a FIFO order: the first request posted in the list is the first processed by RRM PRH�in case it is not possible to reallocate resources to a candidate MS, the MS is put back at the end of the list.

▼ Sorting and Scoring algorithms apply also for PDCH re-allocation procedures


1.146

▼ The TBF allocation becomes:


DL

UL

Master 8

8 4 4Master 4 5 11

4 5

8 5 5

11

8

10

10

10 11


1.147


▼ Objective: Fill up the new TBF allocation after re-allocation

DL

UL

Master 8

8 4 4Master 4 5

4 5

8 5 5

8

11

10

10

11

10

10

1111


1.148

2.2 TBF radio resource re-allocationQoS indicators 1/6

▼ TBF resource re-allocation for each trigger

time

Preparation of the resource re-allocation

Failures cause: no PDCH can be found

Execution of theresource re-allocation

Failures causes

Nb of TBF candidate resource re-allocation

Drop cause

Radio problems

Preparation efficiency rate

External requests

BSS problems Drop cause

Execution efficiency rate

Nb of TBF resource re-allocation successes

Ratio of triggers

Success rate

▼ External requests: FLUSH_LL received from the SGSN, Suspended from the MS.▼ Split between Preparation and Execution phases is driven by the fact that the problems to be interpreted during re-allocation

are relating to the Trigger type.▼ A TBF Re-allocation is analogue to an Intra cell HO in GPRS.


1.149


▼ DL and UL TBF progress: indicators = f(counters)

TBF resources re-allocation : trigger T1

Downlink Uplink

Nb of TBF candidate for resource realloc P403a Nb of TBF candidate for resource realloc P404a

Resource realloc ratio due to trigger T1 P403a / (P403a + P403b +

P403c)

Resource realloc ratio due to trigger T1 P404a / (P404a + P404b +

P404c)

Nb of resource realloc successes P405a Nb of resource realloc successes P406a

Resource realloc success rate P405a / P403a Resource realloc success rate P406a / P404a

Nb of resource realloc exec fail due to

radio problems

P407a Nb of resource realloc exec fail due to

radio problems

P408a

Resource realloc exec fail rate due to radio

problems

P407a / P403a Resource realloc exec fail rate due to radio

problems

P408a / P404a

Nb of resource realloc preparation failures

because no PDCH could be found

P423a Nb of resource realloc preparation failures


P424a

Resource realloc preparation fail rate due

to lack of radio resources

P423a / P403a Resource realloc preparation fail rate due


P424a / P404a

Resource realloc prep efficiency rate (P403a - P423a) / P403a Resource realloc prep efficiency rate (P404a - P424a) / P404a

Nb of resource realloc failures due external

request (suspension request or Flush

message) during exec of the realloc

procedure

P425a Nb of resource realloc failures due external



procedure

P426a

Nb of resource realloc failures due to BSS

pb during exec of the realloc procedure

P403a - P423a - P425a -

P407a - P405a



P404a - P424a - P426a -

P408a - P406a

Exec fail rate due to BSS pb (P403a - P423a - P425a -

P407a - P405a) / P403a

Exec fail rate due to BSS pb (P404a - P424a - P426a -

P408a - P406a) / P404a

Resource realloc exec efficiency rate P405a / (P403a - P423a) Resource realloc exec efficiency rate P406a / (P404a - P424a)


1.150




Downlink Uplink

Nb of TBF candidate for resource realloc P403b Nb of TBF candidate for resource realloc P404b

Resource realloc ratio due to trigger T1 P403b/ (P403a + P403b +

P403c)

Resource realloc ratio due to trigger T1 P404b / (P404a + P404b +

P404c)

Nb of resource realloc successes P405b Nb of resource realloc successes P406b

Resource realloc success rate P405b / P403b Resource realloc success rate P406b / P404b


radio problems

P407b Nb of resource realloc exec fail due to

radio problems

P408b


problems

P407b / P403b Resource realloc exec fail rate due to radio

problems

P408b / P404b



P423b Nb of resource realloc preparation failures


P424b



P423b / P403b Resource realloc preparation fail rate due


P424b / P404b

Resource realloc prep efficiency rate (P403b - P423b) / P403b Resource realloc prep efficiency rate (P404b - P424b) / P404b




procedure

P425b Nb of resource realloc failures due external



procedure

P426b



P403b - P423b - P425b -

P407b - P405b



P404b - P424b - P426b -

P408b - P406b

Exec fail rate due to BSS pb (P403b - P423b - P425b -

P407b - P405b) / P403b

Exec fail rate due to BSS pb (P404b - P424b - P426b -

P408b - P406b) / P404b

Resource realloc exec efficiency rate P405b / (P403b - P423b) Resource realloc exec efficiency rate P406b / (P404b - P424b)


1.151




Downlink Uplink

Nb of TBF candidate for resource realloc P403c Nb of TBF candidate for resource realloc P404c

Resource realloc ratio due to trigger T1 P403c / (P403a + P403b +

P403c)

Resource realloc ratio due to trigger T1 P404c / (P404a + P404b +

P404c)

Nb of resource realloc successes P405c Nb of resource realloc successes P406c

Resource realloc success rate P405c / P403c Resource realloc success rate P406c / P404c


radio problems

P407c Nb of resource realloc exec fail due to

radio problems

P408c


problems

P407c / P403c Resource realloc exec fail rate due to radio

problems

P408c / P404c



P423c Nb of resource realloc preparation failures


P424c



P423c / P403c Resource realloc preparation fail rate due


P424c / P404c

Resource realloc prep efficiency rate (P403c - P423c) / P403c Resource realloc prep efficiency rate (P404c - P424c) / P404c




procedure

P425c Nb of resource realloc failures due external



procedure

P426c



P403c - P423c - P425c -

P407c - P405c



P404c - P424c - P426c -

P408c - P406c

Exec fail rate due to BSS pb (P403c - P423c - P425c -

P407c - P405c) / P403c

Exec fail rate due to BSS pb (P404c - P424c - P426c -

P408c - P406c) / P404c

Resource realloc exec efficiency rate P405c / (P403c - P423c) Resource realloc exec efficiency rate P406c / (P404c - P424c)


1.152


▼ Distribution of triggers and total success rate:

DL ressource realloc

0

20000

40000

60000

80000

100000

120000

140000

160000

180000

01/09/2003 02/09/2003 03/09/2003 04/09/2003 05/09/2003 06/09/2003 07/09/2003

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

T3 Request

T2 Request

T1 Request

% Success


1.153


DL ressource realloc T1

0

5

10

15

20

25

01/09/2003 02/09/2003 03/09/2003 04/09/2003 05/09/2003 06/09/2003 07/09/2003

80

82

84

86

88

90

92

94

96

98

100

102

External stop

Fail radio

Fail BSS

Prep fail

Success

% Success


0

10000

20000

30000

40000

50000

60000

70000

01/09/2003 02/09/2003 03/09/2003 04/09/2003 05/09/2003 06/09/2003 07/09/2003

0

0.2

0.4

0.6

0.8

1

1.2

1.4

External stop

Radio fail

BSS fail

Prep fail

Success

% Success


0

10000

20000

30000

40000

50000

60000

70000

80000

90000

100000

01/09/2003 02/09/2003 03/09/2003 04/09/2003 05/09/2003 06/09/2003 07/09/20030

1

2

3

4

5

6

7

8

External stop

Radio fail

BSS fail

Prep fail

Success

% Success



2 Radio Algorithms

2.3 Cell selection and reselection


1.155

2.3 Cell selection and reselection Principles

▼ Procedures defined in the 05.08 GSM recommendation

▼ Cell selection:

� made using the C1 criterion as for GSM

▼ Cell reselection:

� made using the C1 and C2 criteria as for GSM if MPDCH not available in the serving cell

� otherwise a specific C1 criterion as well as C31 & C32 criteria are computed during the reselection procedure

▼ All the parameters above for serving cell and neighbor cells arebroadcasted on PSI3 & PSI3bis of the serving cell.

▼ C31 & C32 allow a specific GPRS reselection process even if the GPRS neighboring cells list is identical to the GSM one

▼In GSM▼C1 = A - Max (0,B) with ▼ A = RLA_C - RXLEV_ACCESS_MIN ▼ B = MS_TXPWR_MAX_CCH - MS_TXPWR_MAX + POWER_OFFSET(1800)▼C2 = C1 + CELL_RESELECT_OFFSET - TEMPORARY_OFFSET(T) when Penalty_time<31▼C2 = C1 - CELL_RESELECT_OFFSET when Penalty_Time=31

▼In GPRS ready and standby state, cell reselection is performed by MS except for a class A MS while in dedicated mode of a circuit switched connection, in which case the cell is determine by the network according to the handover procedures.

▼For a MS class B which can combine GSM and GPRS states, C1 criteria is used when the MS is simultaneously attached to both network and MS is in Packet Idle Mode (refer to GSM 05.08)


1.156

2.3 Cell selection and reselection Selection criteria computation

▼ Selection:

� C1 = (RLA_P – GPRS_RXLEV_ACCESS_MIN) – max (0, GPRS_MS_TXPWR_MAX_CCCH – P)

�RLA_P: average DL level received�P: power class of the MS

▼C1 is the same as in GSM except that�A = RLA_P – GPRS_RXLEV_ACCESS_MIN: “listening capacity of MS in the cell”�B = GPRS_MS_TXPWR_MAX_CCH – P: “talking capacity of MS in the cell”�C1 must be positive and as high as possible

▼C32:�If the parameter C32_QUAL is equal to 1, positive GPRS_RESELECT_OFFSET values must only be applied to the neighbouring cell �If GPRS_RESELECT_OFFSET (neighbor) >0, the cell has a bonus to reselection �If GPRS_RESELECT_OFFSET (neighbor) <0, the cell has a handicap for reselection

▼In packet idle mode MS must make one measurement for each BCCH carrier monitored every 4 seconds, as well as more than one sample per second for each BCCH carrier.▼A list of 6 strongest cell must be kept an updated at a rate of at least one update per running average period.▼In Packet transfer mode, the MS must monitor a list of 6 strongest non-serving cell BCCH carrier. It must attempt to check the BSIC for each of these 6 strongest cell at least once every 10 seconds.


1.157

2.3 Cell selection and reselection Reselection criteria computation 1/2

▼ Re selection

� Serving cell:

� C31(serving) = RLA_P(serving) – HCS_THR(serving)� C32(serving) = C1(serving)

� Neighbor cell:

� If C31_HYST=Yes,� C31(neighbor)=RLA_P(neighbor) – HCS_THR(neighbor)

– TO(neighbor)x L(neighbor) -GPRS_CELL_RESELECT_HYSTERESIS

� else� C31(neighbor) =RLA_P(neighbor) –

HCS_THR(neighbor) – TO(neighbor)x L(neighbor)� C32 (neighbor) = C1 (neighbor) +

GPRS_RESELECT_OFFSET(neighbor) – TO(neighbor)x (1-L(neighbor))

▼C1 is the same as in GSM except that�A = RLA_P – GPRS_RXLEV_ACCESS_MIN: “listening capacity of MS in the cell”�B = GPRS_MS_TXPWR_MAX_CCH – P: “talking capacity of MS in the cell”�C1 must be positive and as high as possible

▼C32:�if C32_QUAL=1 , positive GPRS_RESELECT_OFFSET value must only be applied to the neighbor cell with the highest RLA_P value of those cells for which C32 is compared above.�If GPRS_RESELECT_OFFSET (neighbor) >0, the cell has a bonus to reselection �If GPRS_RESELECT_OFFSET (neighbor) <0, the cell has a handicap for reselection

▼In packet idle mode MS must make one measurement for each BCCH carrier monitored every 4 seconds, as well as more than one sample per second for each BCCH carrier.▼A list of 6 strongest cell must be kept an updated at a rate of at least one update per running average period.▼In Packet transfer mode, the MS must monitor a list of 6 strongest non-serving cell BCCH carrier. It must attempt to check the BSIC for each of these 6 strongest cell at least once every 10 seconds.


1.158

2.3 Cell selection and reselection Reselection criteria computation 2/2

▼ TO(neighbor) = GPRS_TEMPORARY_OFFSET(neighbor) x H(GPRS_PENALTY_TIME(neighbor) – T(neighbor) )

▼ L(neighbor):� Its value belongs to the relative GPRS_PRIORITY_CLASS

of the GPRS cell

� L=0 if GPRS_PRIORITY_CLASS(neighbor) = GPRS_PRIORITY_CLASS(serving)

� L=1 if GPRS_PRIORITY_CLASS(neighbor) ≠GPRS_PRIORITY_CLASS(serving)

GPRS_PENALTY_TIME

GPRS_TEMPORARY_OFFSET

Time

dB

▼Note: do not get confused with TO (T) the Temporary Offset function and the GPRS_TEMPORARY_OFFSET parameter

▼The L factor is used to cancel the Temporary handicap given to the cell the MS is coming from when the cell has a different priority class.


1.159

2.3 Cell selection and reselection Reselection execution 1/2

▼ MS re-selects a neighboring cell if

� C1(serving) <0

and/or

� neighboring cell have better radio conditions (see next slide)

▼ Cell choice: the best cell is the cell with the highest C32 among

� Those cells that have the highest GPRS_PRIORITY_CLASS

� among those cells that have the highest LSA priority

� among those cells fulfill the criterion C31≥0,

OR

� all the neighbor cells (if C31<0 for all cells)

▼C1<0: both the talking and the speaking capacities of MS are not sufficient

▼GPRS_PRIORITY_CLASS: ▼As far as the reselection procedure is made in NC0 (the MS reselects itself in a new best cell without reporting it to the BSS), it is intended to control the reselection process through the set of GPRS cells available by 2 means:

�The list of GPRS neighbor cell that the MS must monitor to select a set of 6 best cells�The tuning of GPRS_PRIORITY_CLASS for multi-layered networks where Macro cells must treated in a distinct way form the micro cells. The GPRS priority must be high in cell where GPRS traffic is expected to be supported (i.e. according to operator configuration, and radio resource planning)


1.160

2.3 Cell selection and reselection Reselection execution 2/2

▼ neighboring cell has better radio conditions when

� In Ready State when neighboring cell ∈∈∈∈ {same RA}�C32(neighbor)>C32(serving)+GPRS_CELL_RESELEC

T_HYSTERESIS

� In Standby State or Ready state when neighboring cell ∈∈∈∈{NEW RA},

�C32(neighbor)>C32(serving)+RA_RESELECT_HYSTERESIS

▼When evaluating the best cell, the following hysteresis values must be subtracted from the C32 value for the neighboring cells:

�in standby state, if the new cell belongs to the same RA: 0�in ready state, if the new cell belongs to the same RA: GPRS_CELL_RESELECT_HYST. �in standby or ready state, if the new cell belongs to a different RA:RA_RESELECT_HYSTERESIS�in case of a reselection occurred within the past 15 seconds: 5 dB


1.161

Time allowed:

5 minutes

2.3 Cell selection and reselection Exercise1

▼ Master Channel is used

� MS (2W, class B) ; C1(serving) is just becoming negative

�Objective: Find the cell re-selected by the MS

cell C31 C32 GPRS_PRIORITY_CLASS

A 3 10 2

B -6 12 1

C 4 13 1

D -1 14 1

E 2 16 2

F 10 12 1

▼ Serving cell is not mentioned in this table▼ Condition for reselection is supposed to be C1(serving) < 0 (emergency case)


1.162

2.3 Cell selection and reselection Reselection during an UL TBF

▼ UL TBF:

� MFS: after cell reselection the MFS receives no more data in the UL blocks allocated to the MS ⇒ TBF release

� MS: in the new cell, after SI messages acquisition, a new UL TBF is established to resume the UL transfer

� SGSN: the SGSN is informed of the cell change when receiving a LLC unit from the MS in the new cell. Then the SGSN notifies the BSS about the cell change (FLUSH PDU)

▼After a TBF release, it is up to the originator the reinitiate the transfer: MS in UL, SGSN in DL.


1.163

2.3 Cell selection and reselection Reselection during a DL TBF

▼ DL TBF:

� MFS: after cell reselection the MFS receives no more acknowledgements from the MS => abnormal TBF release

� MS: in the new cell, after SI messages acquisition, an UL TBF is established to send a cell update to the SGSN (MS in Ready state)

� SGSN: when SGSN is informed of cell change it sends a message to the MFS to discard LLC units stored for the MS in the old cell (FLUSH PDU)

� The SGSN resumes the DL transfer by sending a DL LLC unit => DL TBF establishment in the new cell

▼After a TBF release, it is up to the originator the reinitiate the transfer: MS in UL, SGSN in DL.


1.164

2.3 Cell selection and reselection Reselection during a DL transfer: example

Cell update (new BVCI)SGSN aware of cell reselection

MFS « aware » of radio problem

MFS aware of cell reselection

▼MFS: after cell reselection the MFS receives no more acknowledgements from the MS ⇒ TBF release▼MS: in the new cell, after SI messages acquisition, an UL TBF is established to send a cell update to the SGSN (MS in Ready state)▼SGSN: when SGSN is informed of cell change it sends a message to the MFS to discard LLC units stored for the MS in the old cell. The SGSN resumes the DL transfer by sending a DL LLC unit ⇒ DL TBF estab in the new cell

▼MFS is always aware of a successful cell change afterwards, upon reception of the flush LL message from SGSN.▼If the cell change is unsuccessful, the TBF release is counted as abnormal.

▼DL_UDT = DL user data▼RAD_STATUS = radio status message sent by MFS to SGSN (BSSGP signaling)▼FLUSH_LL = BSSGP message sent by SGSN to MFS to notify a successful change of cell by MS

▼Refer to Chapter 3 “Gb Interface”.


1.165

Time allowed:

10 minutes

2.3 Cell selection and reselection Exercise2 1/4

▼ Scenario 1: Master Channel is NOT used

� Network configuration is explained hereafter

� MS (2W, class B) is selecting a first cell and immediately starts a transfer

�Objective: Find cells selected by the MS

CI=6169GSM900

CI=1823

GSM900

CI=1964 GSM900

CI=6270

GSM900

CI=6271GSM900 Cell 3 (8557, 1823)

Cell 2 (8564,6169)

Cell 1 (8564, 1964)


1.166


▼ Parameters settings

� For all cells:

� RX_LEV_ACCESS_MIN = -103 dBm

�MS_TXPWR_MAX_CCH_= 33 dBm

� PENALTY_TIME = 0 (20s)

� TEMPORARY_OFFSET = 0 dB

�CELL_RESELECT_OFFSET = 0 dB

� CELL_RESELECT_HYSTERESIS

�Cell 1: 4 dB

�Cell 2: 6 dB

�Cell 3: 6 dB CI=6169GSM900

CI=1823

GSM900

CI=1964 GSM900

CI=6270

GSM900

CI=6271GSM900 Cell 3 (8557, 1823)

Cell 2 (8564,6169)

Cell 1 (8564, 1964)


1.167


▼ Find the cell selected by MS

CI=6169GSM900

CI=1823

GSM900

CI=1964 GSM900

CI=6270

GSM900

CI=6271GSM900 Cell 3 (8557, 1823)

Cell 2 (8564,6169)

Cell 1 (8564, 1964)

5

4

3

2

1

Measurements

-77-85-89

-82-87-88

-87-90-88

-100-90-84

-104-96-80

RxLev (3)RxLev (2)RxLev (1)


1.168

Time allowed:

20 minutes


▼ Scenario 2: Master Channel is used

� Multilayer network is considered: umbrella layers + microcells

� 1. Find parameter settings allowing “GSM like” behaviour: capture towards microcellfor slow mobiles

� 2. If GPRS traffic is to be handled by macrocells, find parameter settings avoiding selection of micro


1.169

▼ Cell reselection: only NC0 in B7

2.3 Cell selection and reselectionQoS indicators

Number of successful cell re-selection P397

Number of DL TF release due to Cell reselection P396a

Number of UL TF release due to Cell reselection P396b

NC0 re-selection

NC2 re-selection

▼ Network Control Order:� NC0: normal MS control; the MS must perform autonomous cell reselection� NC1: MS control with measurement reports; the MS must send measurement reports to the network and perform

autonomous reselection� NC2: Network control; the MS must send measurement reports to the network; MS must not perform autonomous cell

reselection� The counters for reselection in NC1 and NC2 are not implemented yet

▼ New in B7: P396a, P396b, P397.▼ P397 counts the number of successful reselections in READY STATE (idle or transfer mode). It counts the number of FLUSH

messages received from the SGSN. It is incremented whenever the MS is in PTM mode or not.▼ P396a (resp. P396b) counts the number of DL (resp. UL) TBF release due to a cell reselection.

� Both of them are incremented if the FLUSH_LL message arrives from SGSN before the abnormal TBF Release has been detected by the MFS. If not they are not incremented.

▼ Therefore it is not possible to compute the real number of abnormal TBF release due to a radio problem.



2 Radio Algorithms

2.4 Up-link power control


1.171

2.4 Up-link power control Measurements

▼ The MS makes level measurements defined by the 05.08 GSM recommendation:

� in packet idle mode:

�BCCH of the serving cell (paging blocks monitored by the MS);

� if MPDCH established, measurement on PCCCH = received signal on each paging block monitored, according to its DRX mode and paging group

� in packet transfer mode:

� behavior defined by the parameter PC_MEAS_CHANbroadcast on the PBCCH (PSI1)� PBCCH of the serving cell (or BCCH if no MPDCH)� on all the blocks of the PDCH carrying the PACCH

▼MS use DL level measurements to determine the power: open loop PC


1.172

2.4 Up-link power control Averaging

▼ Cn = a * (SSn + Pb) + (1-a) * Cn-1

� a is the forgetting factor:� packet idle mode: 1 / min(n, max(5, T_AVG_W / TDRX))

� TDRX = BS_PA_MFRMS (number of 51 multi-frame between 2 paging)

� packet transfer mode: 1/ (6 * T_AVG_T) (BCCH)or 1/ (12 * T_AVG_T) (PDCH)

� SSn is the measurement at iteration n:� average level of block n in packet idle mode and packet

transfer mode (PDCH)� level of the sample in packet transfer mode (BCCH)

� Pb is a correcting factor relating the power reduction value applied by the BTS on PCCCH and/or PDCH, to be compared with the output power used on the BCCH

▼Use of a recursive filtering to obtain an average level

▼Average levels calculated in packet idle mode used in packet transfer mode and vice versa: a proper average level is available at the beginning of the transfer

▼The respective values of the T_AVG_T and T_AVG_W averaging windows is broadcasted on PSI1.


1.173

2.4 Up-link power control MS power

▼ MS power for access on RACH: GPRS_MS_TXPWR_MAX_CCH

▼ MS use the same power during a radio block (4 bursts)

▼ MS power = min(Γ0 - Γch - α * (C + 48), GPRS_MS_TXPWR_MAX_CCH)

� Γ0 = 39 dBm in GSM 900, 36 dBm in GSM 1800

� α and Γch are sent to the MS (α: SI 13, α and Γch: Packet UL and DL assignment) and are tuned in order to obtain a given behavior

� C is the average DL level calculated by the MS

▼MS power access on RACH can be MS_TXPWR_MAX_CCH. In fact, MS will use the first of the 2 values listened on the cell broadcast information.▼The 05.08 GSM recommendation suggests to:

�use α = 1� tune Γch in order to reach a given UL level (LEVUL) at the BTS side: Γch = Γ0 - 48 - LEVUL - PBTS (PBTS: BTS power)�explanation:

�Pm = Γ0 - Γch - α * (C + 48)�Pm = LEVUL - LEVDL + PBTS

�When you fix α=1, you will get a specific value for Γch, which is not usable for any value of α.�Proceed by dichotomy to find the proper value of Γch

▼Another possibility:�if path balance: PBTS - Pm = Sm - SBTS (S: sensitivity)�therefore: LEVDL - LEVUL = Sm - SBTS

�and Pm = Γ0 - Γch - α * (LEVUL + Sm - SBTS + 48)�example with G3 BTS: Pm = Γ0 - Γch - α * (LEVUL + 57)�possibility of tuning:

�power reduction when the UL level is higher than U_RXLEV_UL_P�MS power not lower than 13/4 dBm in GSM 900/1800



2 Radio Algorithms

2.5 Coding scheme adaptation


1.175

2.5 Coding scheme adaptation Principle 1/2

▼ Two coding schemes are available in B7:� CS1 (20 useful bytes in the RLC block): always used for

signaling and can be used for traffic� CS2 (30 useful bytes in the RLC block): used for traffic

▼ MFS decides the change of coding scheme▼ The decision process relies on distinct thresholds according to:

� hopping or non-hopping TRX� Acknowledge or non-acknowledge mode� UL or DL TBF

▼ CS adaptation is enabled by the mean of 2 parameters:� EN_CS_ADAPTATION_ACK� EN_CS_ADAPTATION_NACK

▼CS3 and CS4 should come in further releases and should offer:�CS3: 36 useful bits per RLC block�CS4: 50 useful bits per RLC block

▼Before being able to offer those CS, we must change the transmission capacity on the Abis interface (limited to 16 Kbit/s so far

▼In B7, it is expected to offer services in NACL mode. Also, the flag AN_CS_ADAPTATION in B6.2 is split into two flag, one for services offered in ACK mode and another one for services in NACK mode.


1.176

2.5 Coding scheme adaptation Principle 2/2

▼ The CS is adapted according to QUALITY reporting (based on the BLER):

� for DL TBF:

�MS makes quality measurements on all the blocks it is sent

�MS reports quality measurements in the “Packet DL Ack/Nack” messages

� then, the MFS computes long term and short term averages

� for UL TBF:

�BTS makes quality measurements on all TS for each block sent by MS

� then MFS computes long term and short term averages on all TS

▼The CS adaptation algorithm is fairly different from what we had in B6.2 release:�the received level is no more taken into account�for DL TBF, the quality reported by MS is averaged in the MFS

▼The scheduling of Packet UL Ack/Nack messages is in correlation with the two radio parameters:�DL_ACK_PERIOD: number of blocks between 2 messages for a DL TBF in acknowledge mode�DL_NACK_PERIOD: number of blocks between 2 messages for a DL TBF in non-acknowledge mode

▼For UL TBF, BTS computes measurements over:�UL_ACK_PERIOC RLC blocks in Acknowledge mode�UL_NACK_PERIOD RLC blocks in Non-acknowledge mode


1.177

2.5 Coding scheme adaptation Measurements averaging in MFS

▼ DL / UL TBF = 2 averages are computed:� Short term average AV_RXQUAL_STAV_RXQUAL_STn+1 = (1 - 1 / zn+1) * AV_RXQUAL_STn + (1 /

zn+1) * RXQUALn,

with zn+1 = αST∆tn * zn + 1,

and αST = (1 - β)(1 / CS_AVG_PERIOD_ST)

� Long term average AV_RXQUAL_LTAV_RXQUAL_LTn+1 = (1 - 1 / yn+1) * AV_RXQUAL_LTn + (1 /

yn+1) * RXQUALn,

with yn+1 = αLT∆tn * yn + 1,

and αLT = (1 - β)(1 / CS_AVG_PERIOD_LT)

▼In the formula above:�RXQUALn is the RXQUAL value reported by the MS in the nth PACKET DL ACK/NACK message

�∆tn is the time difference in seconds between the (n-1)th and the nth PACKET DL ACK/NACK messages, therefore depending on DL_ACK_PERIOD parameter value, on the nb of PDCH used by the MS and on the traffic ofthe other MS multiplexed on these PDCH.

�AV_RXQUAL_STn (respectively AV_RXQUAL_LTn) is the value of AV_RXQUAL_ST (respectively AV_RXQUAL_LT) after the nth PACKET DL ACK/NACK message

�β is hard coded end equal to 0.9

▼Remark: the initial value of yn and zn is 0

▼ 1/CS_AVG_PERIOD_LT and 1/CS_AVG_PERIOD_ST correpond to forgetting factors: number of seconds in the past above which Quality measurements and considered as too old to be taken into account in the average

▼ Default valiues are: CS_AVG_PERIOD_ST = 0.1 sCS_AVG_PERIOD_LT = 1 sboth of them are not settable at OMC-R


1.178

2.5 Coding scheme adaptation Decision process in MFS

▼ CS1 to CS2:� in DL: AV_RXQUAL_LT < CS_QUAL_DL_1_2_X_Y

� in UL: AV_RXQUAL_LT < CS_QUAL_UL_1_2_X_Y

▼ CS2 to CS1:� in DL: AV_RXQUAL_LT > CS_QUAL_DL_1_2_X_Y +

CS_HST_DL_LT or AV_RXQUAL_ST > CS_QUAL_DL_1_2_X_Y + CS_HST_DL_ST

� in UL: AV_RXQUAL_LT > CS_QUAL_UL_1_2_X_Y + CS_HST_UL_LT or AV_RXQUAL_ST > CS_QUAL_UL_1_2_X_Y + CS_HST_UL_ST

▼ At the beginning of a TBF, the MFS needs wait TBF_CS_PERIOD RLC blocks before the first change of CS

▼AV_RXQUAL_ST is a short term average whereas AV_RXQUAL_LT is a long term average. The short term average is used to react quickly in case of fast degradation of the radio conditions▼X = FH or NFH: two thresholds are available for hopping and non-hopping TRX▼Y = ACK or NACK: two thresholds are available for RLC acknowledged and unacknowledged modes▼At the OMC-R: CS_QUAL_DL_1_2 and CS_QUAL_UL_2_1 are both used for ACK or NACK transfer mode as well as for Hopping and Non-Hopping TRX

▼TBF_CS_PERIOD = 20 RLC blocks by default and is not settable at OMC-R


1.179

2.5 Coding scheme adaptation Execution

▼ UL TBF:

� the CS to be used is indicated to the MS during the establishment phase

� if a CS adaptation is decided by the MFS during the transfer phase a PACKET UL ACK/NACK message is sent immediately to the MS

▼ DL TBF:

� if a CS adaptation is decided by the MFS during the transfer phase, the MFS modifies the CS


1.180

2.5 Coding scheme adaptation Defense procedure

▼ In a DL TBF:

If the number of PACKET DL ACK/NACK messages consecutively lost from the MS on the radio interface goes over TBF_CS_DL, the coding scheme is changed to CS1

▼ In UL TBF:

If the number of radio blocks consecutively not decoded goes over the threshold Nb_allocated_TS x TBF_CS_UL, the coding scheme is changed to CS1

▼ In both cases, the CS must not be changed again before TBF_CS_PERIOD RLC blocks are transmitted

▼In B6.2 two parameters were used for the monitoring of the change of CS:�TBF_CS_PERIOD1: number of RLC blocks to be transmitted before changing the TBF for the first time

�Default value = 20 RLC blocks�TBF_CS_PERIOD2: number of RLC block to be transmitted between 2 changes of CS

�Default value = 10 RLC blocks

▼Moreover, the CS adaptation algorithms do not include RX_Lev conditions anymore. The decision process is entirely based on RX_QUAL. This is the reason why 2 loops are inludes = the Short Term loop (for emergency situation) and the Long Term loop for normal adaptation of the CS.

▼TBF_CS_DL = 6 by default and is settable at OMC-R▼TBF_CS_UL = 32 by default and is settable at OMC-R


1.181

2.5 Coding scheme adaptation Initial coding scheme

▼ The initial CS at TBF establishment is given by the parameters:

� TBF_DL_INIT_CS for a DL TBF & TBF_UL_INIT_CS for a UL TBF

�Cell parameter�CS1 or CS2�Default value = CS1

� T_DL_GPRS_MeasReport: time period to request for a “Packet Downlink Ack/Nack” with measurements

�Cell parameter�Values: from 60 to 3000ms


1.182

Time allowed:

10 minutes

2.5 Coding scheme adaptation Exercise 1/2

▼ CS adaptation / DL measurements

� Network parameters:

� TBF_DL_INIT_CS = CS1�CS_QUAL_DL_1_2_X_Y = 2�CS_HST_DL_LT = 2�CS_HST_DL_ST = 4

� Objective: Find CS used in DL


1.183

2.5 Coding scheme adaptation Exercise 2/2

▼ Find which CS is used at each measurement

Measurement 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

RXQUAL_DL 0 0 2 3 4 5 5 5 6 0 0 0 0 6 7 7

AV_RXQUAL_DL_LT 0,0 0,0 1,1 1,9 2,6 3,3 3,8 4,1 4,5 3,5 2,7 2,1 1,7 2,6 3,5 4,2

AV_RXQUAL_DL_ST 0,0 0,0 1,7 2,7 3,8 4,8 5,0 5,0 5,8 1,2 0,2 0,0 0,0 4,8 6,6 6,9

CS ?

0

1

2

3

4

5

6

7

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

RXQUAL_DL AV_RXQUAL_DL_LT AV_RXQUAL_DL_ST

Short term average is calculated with AlphaST = 0.2Short term average is calculated with AlphaLT = 0.8


1.184

2.5 Coding scheme adaptationQoS indicators 1/6

PDTCHRLC blocks

PACCHRLC blocks

Number useful, re-transmitted, lost blocks (CS1 & CS2)

Retransmission rate, lost rate

Throughput per cell, per PDCH

PDTCH occupancy

CS1 & CS2 distribution

PACCH occupancy

Coding Scheme transitions

CS1->CS2

CS2 -> CS1

LT

ST

▼ DL and UL TBF: RLC statistics: introduction


1.185

2.5 Coding scheme adaptation QoS indicators 2/6

KPI

KPI

RLC statistics

Downlink Uplink

Number of useful

PDTCH RLC blocks in

CS1 and CS2

CS1 : P55a

CS2 : P55b

Number of useful

PDTCH RLC blocks in

CS1 and CS2

CS1 : P57a

CS2 : P57b

Number of

retransmitted PDTCH

RLC blocks in CS1 and

CS2

Acknowledged mode

CS1 : P20a

CS2 : P20b

Number of

retransmitted PDTCH


CS2

Acknowledged mode

CS1 : P21a

CS2 : P21b

Number of lost PDTCH


CS2

Unacknowledged mode

CS1 : P72a

CS2 : P72b

Number of lost PDTCH


CS2

Unacknowledged mode

CS1 : P73a

CS2 : P73b

PDTCH RLC block

retransmission rate(P20a + P20b) /

(P55a + P55b + P20a

+ P20b + P72a +

P72b)

PDTCH RLC block

retransmission rate(P21a + P21b) /

(P57a + P57b + P21a

+ P21b + P73a +

P73b)PDTCH RLC block lost

rate(P72a + P72b) /

(P55a + P55b + P20a

+ P20b + P72a +

P72b)

PDTCH RLC block lost

rate(P73a + P73b) /

(P57a + P57b + P21a

+ P21b + P73a +

P73b)

PDTCH RLC block

CS2 / (CS1 + CS2)

ratio

(P20b + P55b + P72b) /

(P20a + P55a + P72a +

P20b + P55b + P72b)

PDTCH RLC block

CS2 / (CS1 + CS2)

ratio

(P21b + P57b + P73b) /

(P21a + P57a + P73a +

P21b + P57b + P73b)

▼ DL and UL TBF: RLC statistics: indicators = f(counters)

▼ P72a, P72b, P73a, P73b were not usable in B6.2 (part of the restriction list) for the following reasons:� No services in NAck RLC mode of transmission were available� The default RLC transmission mode in Ack when must be specified when UE or SGSN wants to use the NAck by the

means of� 2 phase UL TBF Establishment (not available in B6.2)� BSSGP header containing QoS information (available)

▼ Both the retransmission rate and the lost rate demonstrate the radio quality of services offered either in ACK mode of transmission or NACK mode of transmission.

▼ The retransmission rate is constantly monitored by the MFS for Radio Link Supervision purposes, but per TBF. The view of the retransmission rate per PDCH offers a closest approach to the overall radio quality of a serving area (the cell).

▼ Retransmission rate and lost rate are expected to stay low (even if no specific value can be recommended so far).▼ The retransmission rate and the lost rate can be computed per CS as well. If the Coding Scheme Adaptation mechanisms work

properly, the two rate have to be low in CS2, anyway, always lower than in CS1 (which the Coding Scheme offered in the worst radio conditions)

▼ It is expected to get from CSx RLC block ratios additional information about the overall radio quality in the cell. As Coding Scheme Adaptation algorithms aim at making the user being transferred blocks in CS2 as often as possible in good radio condition, it can be said that were are looking for a high proportion of CS2 blocks but not at any price.


1.186


RLC statistics

Maximum number of

useful PDTCH RLC

blocks in CS1 and CS2

CS1 : P56a

CS2 : P56b

Maximum number of

useful PDTCH RLC

blocks in CS1 and CS2

CS1 : P58a

CS2 : P58b

CS1 peak useful

throughput in kbit/s at

RLC level

(P56a * N1) / (gp *

1000)

CS1 peak useful


RLC level

(P58a * N1) / (gp *

1000)

CS2 peak useful


RLC level

(P56b * N2) / (gp *

1000)

CS2 peak useful


RLC level

(P58b * N2) / (gp *

1000)

Average useful


RLC level per PDCH

(P55a*N1 + P55b*N2)

/ ((P38/10) * 1000)

Average useful


RLC level per PDCH

(P57a * N1 + P57b *

N2) / ((P38/10) * 1000)

Average useful


RLC level per cell

((P55a * N1 + P55b *

N2) * (P149/10)) /

((P38/10) * 1000)

Average useful


RLC level per cell

((P57a * N1 + P57b *

N2) * (P149/10)) /

((P38/10) * 1000)

PACCH occupancy P59 / (12 *

((P38/10)*(1/0.240))

PACCH occupancy P60 / (12 *

((P38/10)*(1/0.240))

PDTCH occupancy (P20a + P20b + P55a +

P55b + P72a + P72b +

P421) / (12*(P38/10)*

(1/0.240))

PDTCH occupancy (P21a + P21b + P57a +

P57b + P73a + P73b) /

(12*(P38/10)*(1/0.240)

)

Average

TX_EFFICIENCY

P336 Average

TX_EFFICIENCY

P335


▼ The TBF throughput is the closest approach to the end-user throughput. It has to be close to the average throughputs expected to be provided to the users with the GPRS service.

� N1 = nb of bits per RLC blocks in CS1 = 8 x 20 = 160� N2 = nb of bits per RLC blocks in CS2 = 8 x 30 = 240

� P16/10 = cumulated overall DL TBF connection time (active + delayed)� P16a/10 is the cumulated active DL TBF connection time� P29/10 = cumulated overall UL TBF connection time � The value are provided in seconds with one significant digit after the comma (the reason why the counter are then

divided by 10).

▼ The PDCH throughput is the closest approach to the BSS use of the resource allocated by the BSC. It gives a reliable information about the GPRS traffic in a cell. It is not expected to reach a specific value as PDCHs carry useful data+retransmitted+signaling blocks.

� P38/10 = cumulated time during which PDCH are established in the cell (always the same number in UL and DL of course)

� This counter counts the “pre-allocated” PDCH, i.e. we don’t need to add up the minimum number of PDCH & MPDCH constantly allocated to GPRS

� The value are provided in seconds with one significant digit after the comma (the reason why the counter are then divided by 10)


1.187


Coding scheme adaptation

Downlink Uplink

Coding Scheme

adaptation from CS1 to

CS2 (long term)

P355a Coding Scheme


CS2 (long term)

P356a

Coding Scheme


CS1 (short term)

P353a Coding Scheme


CS1 (short term)

P354a

Coding Scheme


CS1 (long term)

P357a Coding Scheme


CS1 (long term)

P358a

Ratio of coding scheme


CS1 over all coding

scheme adpatations

(P353a + P357a) /

(P353a + P357a +

P355a)

Ratio of coding scheme


CS1 over all coding

scheme adpatations

(P354a + P358a) /

(P354a + P358a +

P356a)

Ratio of short term

coding scheme


CS1 over all coding

scheme adpatations

from CS2 to CS1

P353a / (P353a +

P357a)

Ratio of short term

coding scheme


CS1 over all coding

scheme adpatations

from CS2 to CS1

P354a / (P354a +

P358a)

P354a and P358a are in restriction (FR A25/135889)



1.188


Downlink Traffic Load

0

50000

100000

150000

200000

250000

300000

350000

400000

14 /08 /20

03

16 /08 /20

03

18 /08 /20

03

20 /08 /20

03

22 /08 /20

03

24 /08 /20

03

26 /08 /20

03

28 /08 /20

03

30 /08 /20

03

01 /09 /20

03

03 /09 /20

03

05 /09 /20

03

07 /09 /20

03

09 /09 /20

03

11 /09 /20

03

13 /09 /20

03

0

10

20

30

40

50

60

70

Blocks CS2

Blocks CS1

%io CS2

RLC Efficiency on downlink

0

50000

100000

150000

200000

250000

300000

350000

400000

14 /08 /20

03

16 /08 /20

03

18 /08 /20

03

20 /08 /20

03

22 /08 /20

03

24 /08 /20

03

26 /08 /20

03

28 /08 /20

03

30 /08 /20

03

01 /09 /20

03

03 /09 /20

03

05 /09 /20

03

07 /09 /20

03

09 /09 /20

03

11 /09 /20

03

13 /09 /20

03

0

0.5

1

1.5

2

2.5

CS2 useful

CS1 useful

% CS2retrans% CS1retrans

▼ Typical values of CS2/(CS1+CS2) ratio on DL path are:� When CS2 is not at beginning of TBF:

40%, 45%, 47%� When CS2 is at beginning of TBF:

97%, 98%to be correlated to the Average useful RLC throughput per TBF on page 196

▼ Typical values of global retransmission rate on DL path are:� When CS2 is not at beginning of TBF:

0.7%, 0.8%, 0.9% � When CS2 is at beginning of TBF:

1.1%, 1.2%

▼ Optimise CS adaptation to optimise user data throughput (best useful RLC throughput and while avoiding TBF drop).

▼ All blocks are considered in graph 1 whereas only useful blocks are considered in graph 2.

▼ Questions?� Q1: What does high proportion of blocks in CS1mean?

� Q2: What does high proportion of blocks in CS2 mean?


1.189


Uplink Traffic Load

0

50000

100000

150000

200000

250000

14 /08 /20

03

16 /08 /20

03

18 /08 /20

03

20 /08 /20

03

22 /08 /20

03

24 /08 /20

03

26 /08 /20

03

28 /08 /20

03

30 /08 /20

03

01 /09 /20

03

03 /09 /20

03

05 /09 /20

03

07 /09 /20

03

09 /09 /20

03

11 /09 /20

03

13 /09 /20

03

0

5

10

15

20

25

30

35

40

45

Blocks CS2

Blocks CS1

%io CS2

RLC Efficiency on uplink

0

50000

100000

150000

200000

250000

14 /08 /20

03

16 /08 /20

03

18 /08 /20

03

20 /08 /20

03

22 /08 /20

03

24 /08 /20

03

26 /08 /20

03

28 /08 /20

03

30 /08 /20

03

01 /09 /20

03

03 /09 /20

03

05 /09 /20

03

07 /09 /20

03

09 /09 /20

03

11 /09 /20

03

13 /09 /20

03

0

0.5

1

1.5

2

2.5

CS2 useful

CS1 useful

% CS2retrans% CS1retrans

▼ Typical values of CS2/(CS1+CS2) ratio on UL path are:� When CS2 is not at beginning of TBF:

6%, 12%, 16%� When CS2 is at beginning of TBF:

48%, 77% (less high than for DL since for UL TBF CS1 is always used during the TLLI Contention Resolution)▼ Typical values of global retransmission rate on UL path are:

� When CS2 is not at beginning of TBF: 0.1%, 0.2%, 0.4%,

� When CS2 is at beginning of TBF: 0.2%, 0.6%



2 Radio Algorithms

2.6 Radio link supervision


1.191

2.6 Radio link supervision Principle

▼ During an UL or DL packet transmission, the corresponding TBF can be released due to an abnormal situation:

� no acknowledgement or data received

� transmission is stalled

� too low transmission efficiency

▼ The abnormal release is always followed by the re-establishment of the TBF in case of uplink transfer (initiative of the MS)

▼ In case of downlink transfer, most of the SGSN do not take the initiative to re-establish the TBF

▼The RLS mechanisms processes in the MFS are based on the following assumption:▼« in a specific transfer situation, the MFS is expecting the MS to behave in a specific way »

� In UL TBF, the MFS schedules USF for UL blocks and expects the MS to understand the MFS’sacknowledgements� In DL TBF, the MFS sends blocks to the MS and expects them to be acknowledged when scheduled by the MFS (use of RRBP)

▼Most of the RLS mechanisms prevailed from B6.2


1.192

2.6 Radio link supervision DL TBF 1/2

DL ACK/NACK PERIOD blocks

RRBP≠≠≠≠ false

Ø N3105 = N3105+1

PDTCH PDTCH

PACCH

Scheduling of “Packet DL Ack/Nack”PACCH block

N3105>N3105_LIMIT

PDTCH

Stop sending DLPDTCH blocks

▼ The MFS counts the number of consecutive PACKET DL ACK/NACK not received due to loss on the radio interface:� if the counter is above the threshold TBF_CS_DL_2_1 and CS2 is used, the MFS switches to CS1

� if the counter is above the threshold N3105_LIMIT the DL TBF is abnormally released:� the MFS stops sending packets to the MS and sends a message to the SGSN (Radio Status)� it is up to the SGSN to re-establish the DL TBF� the MS releases the TBF on its side

▼ N3105_LIMIT = 6 by default and is not settable at OMC-R

▼ Other Abnormal DL TBF release: DL window stalled� In GPRS acknowledged mode NstagnatingWindowDL counter must be incremented when the same oldest RLC data

block in the transmit window is not acknowledged by the last received bitmap. � If N_StagnatingWindowDL exceeds its limit, then the network must terminate the TBF

� NstagnatingWindowDL_LIMIT = 8 by default and is not settable at OMC-R


1.193

2.6 Radio link supervision DL TBF 2/2

DL ACK/NACK PERIOD blocks

RRBP≠≠≠≠ false

PDTCH PDTCH

PACCH

Packet DL Ack/Nack

Scheduling of “Packet DL Ack/Nack”PACCH block

PDTCH

Stop sending DLPDTCH blocks

N_StagnatingWindowDL =N_StagnatingWindowDL

+1

N_StagnatingWindowDL > NstagnatingWindowDL_LIMIT

Same oldest RLC block Nack in the RBB

▼ Other Abnormal DL TBF release: DL window stalled� In GPRS acknowledged mode NstagnatingWindowDL counter must be incremented when the same oldest RLC data

block in the transmit window is not acknowledged by the last received bitmap. � If N_StagnatingWindowDL exceeds its limit, then the network must terminate the TBF� NstagnatingWindowDL_LIMIT = 8 by default and is not settable at OMC-R


1.194

2.6 Radio link supervision UL TBF - Abnormal release with random access 1/2

N3101 = N3101+NØPDTCH

N3101>N3101_LIMIT

PACCH

Stop sending “Packet ULACK/NACK” PACCH blocks

ØPDTCH

N consecutive

USF

USF

Packet Random Access

▼N3101_LIMIT = 48 by default and is not settable at OMC-R

▼the MFS manages several counters:�N3101: number of RLC PDU consecutively lost since the last reception of an UL RLC PDU:

�N3101 is incremented each time an UL radio block is allocated to the MS and no data is received�if N3101 is above N3101_LIMIT the UL TBF is abnormally released: the MFS stops sending PACKET UL ACK/NACK to the MS

�the MS waits for PACKET UL ACK/NACK and then releases the TBF on its side�then the MS sends a random access to re-establish the UL TBF


1.195

2.6 Radio link supervision UL TBF - Abnormal release with random access 2/2

SI=1

PDTCHN_StagnatingWindowUL =

N_StagnatingWindowUL+1

PACCH


SI=1

PDTCH

USF

USF

Packet Random Access

PACCH

N_StagnatingWindowUL > NstagnatingWindowUL_LIMIT

The previous mechanism has been replaced in B7 by the following one▼Other Abnormal UL TBF release: UL window stalled

� SI=1 in an UL RLC DATA BLOCK indicates that the MS transmit window is stalled.� Upon detecting the stall condition, the network sends a Packet Uplink Ack/Nack message and after a round trip delay has elapsed it increments N_ULStagnatingWindow.� If N_StagnatingWindowUL exceeds its limit, then the network must terminate the TBF� NstagnatingWindowUL_LIMIT = 8 by default and is not settable at OMC-R


1.196

2.6 Radio link supervision UL TBF - Abnormal release with cell reselection 1/2

reselection

N3102

PAN_MAX

0

UL TBFAbnormalrelease

RandomAccess

PAN_DEC

PAN_INC

Packet UL Ack/Nackreceived OK

▼Abnormal release with cell reselection:

�procedure linked to the counter N3102 internal to the MS and initialized to PAN_MAX after each reselection:�each time the MS performs an abnormal release with random access it decreases N3102 by PAN_DEC�each time the MS receives a PACKET UL ACK/NACK it increases N3102 by PAN_INC�if N3102 reaches 0 the MS performs an abnormal releases with cell-reselection

�the MS triggers a cell reselection procedure but nothing allows it to change its serving cell (need of Master PDCH to be able to re-select a new cell)�after the cell reselection the MS sends a random access to re-establish the UL TBF


1.197

2.6 Radio link supervision UL TBF - Abnormal release with cell reselection 2/2

▼ If Master PDCH is available in the serving cell AND▼ If RANDOM_ACC_RETRY = Allowed

� Then the following reselection algorithm is applied:� The MS re-selects the cell with the highest RLA among

the 6 best levels� In this cell, if the MS can not decode the PBCCH data

block, it re-selects the next highest Received Level Average

� If the cells with the 6 strongest RLA have been tried but cannot be used, the MS performs a normal reselection (see 2.3 Cell Selection and reselection)

� Else the normal reselection algorithm is applied (see 2.3)▼ After T_RESEL, the MS is allowed to re-select the serving cell

▼ RLA = Received Level Average.

▼ T_RESEL = 5s (default value).

▼ Extract of the 05.08 GSM standard:▼ In the event of an abnormal release with cell reselection (see 3GPP TS 04.60) when PBCCH exists, an abnormal cell reselection

based on BA(GPRS) must be attempted. The MS must perform the following algorithm to determine which cell to be used for this cell reselection attempt.

▼ If access to another cell is not allowed, i.e. RANDOM_ACCESS_RETRY bit is not set on the serving cell:� i) The abnormal cell reselection attempt must be abandoned, and the algorithm of subclause 10.1.3 must be performed.

▼ If access to another cell is allowed, i.e. RANDOM_ACCESS_RETRY bit is set on the serving cell:� i) The received level measurement samples taken on the carriers indicated in the BA (GPRS) received on the serving cell

in the last 5 seconds must be averaged, and the carrier with the highest received level average (RLA) with permitted BSIC, i.e. the same as broadcast together with BA (GPRS), (see subclause 10.1.1), must be taken.

� ii) On this carrier the MS must attempt to decode the PBCCH data block containing the parameters affecting cell selection.� iii) If the cell is suitable (see 3GPP TS 03.22), abnormal cell reselection must be attempted on this cell.� iv) If the MS is unable to decode the PBCCH data block or if the conditions in iii) are not met, the carrier with the next

highest received level average (RLA) with permitted BSIC must be taken, and the MS must repeat steps ii) and iii) above.� v) If the cells with the 6 strongest received level average (RLA) values with permitted BSICs have been tried but cannot be

used, the abnormal cell reselection attempt must be abandoned, and the algorithm of subclause 10.1.3 must be performed.

▼ The MS is under no circumstances allowed to access a cell to attempt abnormal cell reselection later than 20 seconds after the detection within the MS of the abnormal release causing the abnormal cell reselection attempt. In the case where the 20 seconds elapses without a successful abnormal cell reselection the attempt must be abandoned, and the algorithm of subclause 10.1.3 must be performed.

▼ In the event of an abnormal release with cell reselection (see 3GPP TS 04.60) when only BCCH exists, the MS must only perform the algorithm of subclause 10.1.3.


1.198

2.6 Radio link supervision UL TBF in ending phase

N3103 = N3103+1ØPACCH

N3103>N3103_LIMIT

PACCH


FinalBlock

PDTCH

USF

USF

PACCH

FinalAck

Scheduling of “Packet Control Ack”

▼The MFS can also trigger an abnormal release at the end of an UL TBF:�the MFS counts the number of PACKET CONTROL ACK not received in response to the PACKET UL ACK/NACK which indicates the end of the TBF�if the counter is above N3103_LIMIT, the UL TBF is abnormally released: the MFS stops sending PACKET UL ACK/NACK to the MS

▼N3103_LIMIT = 1 by default and is not settable at OMC-R


1.199

2.6 Radio link supervision UL and DL TBF

▼ A TX_Efficiency is computed every TX_EFFICIENCY_PERIODtransmitted RLC data blocks and compared to following thresholds:� TX_EFFICIENCY_ACK_THR in Acknowledge mode� TX_EFFICIENCY_NACK_THR in Non-Acknowledge mode

▼ If the TX_Efficiency is below these thresholds the TBF must be released

▼ It is done as an abnormal release by the MFS:� the MFS stops sending DL RLC PDU in case of a DL TBF� the MFS stops sending PACKET UL ACK/NACK in case of

an UL TBF

▼.Radio Link Supervision based on TX_Efficiency monitoring�Instead of considering the retransmission rate like in B6, it was proposed in B7 to use the transmission efficiency, i.e. the ratio of the average net bit rate over the gross bit rate. �This transmission efficiency can be computed approximately as:

where

NB_SENT is the number of transmitted RLC data blocks,

NB_RECEIVED is the number of correctly received RLC data blocks (i.e. blocks such that a positive acknowledgment is reported),

ρi is equal to the number of information bits in the i-th correctly received RLC data block divided by the number of bits per RLC data block with GMSK modulation (456 in GPRS). This ratio only depends on the coding scheme used for the i-th correctly received RLC data block and is between 0 and 1 in GPRS.

ni is the number of RLC data blocks in the i-th radio block. Therefore, this number is always equal to 1 for GPRS,

�ρi = 0.40 for CS1 and 0.59 for CS2

� TX_EFFICIENCY is computed during a fixed window of TX_EFFICIENCY_PERIOD data blocks and then compared to threshold (TX_EFFICIENCY_ACK_THR if Ack mode and TX_EFFICIENCY_NACK_THR if Nack).Then if TX_EFFICIENCY < Tx_efficiency_threshold then the TBF is release (abnormaly).

� TX_EFFICIENCY_ACK_THR = 10%, TX_EFFICIENCY_NACK_THR = 15%, TX_EFFICIENCY_PERIOD = 50all settable at OMC-R

∑

∑

=

==SENTNB

i i

RECEIVEDNB

i i

n

nEFFICIENCYTX

_

1

_

1

i

1100_

ρ


1.200

2.6 Radio link supervision Exercise

▼ List in DL and UL the different cases of abnormal release

Time allowed:

10 minutes


1.201

2.6 Radio link supervision TBF release, QoS indicators 1/5

TBF establishment

time

TBF end Normal release rate

Acceptable release rate

Drop causes

PDCH fast pre-emption

Suspend procedure

Flush messageRadio

Radio fail during resource realloc exec

BSS

Gb

Other problems: blocking situation + N_stagnating window

▼ DL and UL TBF release: introduction


1.202


TBF releases and drops

Downlink Uplink

Normal release rate P9 / (P90a + P90b + P90c +

P90d + P90e + P90f)

Normal release rate P22 / (P30a + P30b + P30c)

Acceptable release rate (P146 + P98a + P396a) /

(P90a + P90b + P90c + P90d

+ P90e + P90f)

Acceptable release rate (P147 + P98b +P396b) / (P30a

+ P30b + P30c)

Drop rate (P90a + P90b + P90c + P90d

+ P90e + P90f - P9 - P146 -

P98a - P396a) / (P90a + P90b

+ P90c + P90d + P90e + P90f)

Drop rate (P30a + P30b + P30c - P22 -

P147 - P98b - P396b) / (P30a

+ P30b + P30c)

Release rate due to PDCH

fast pre-emptionP146 / (P90a + P90b + P90c

+P90d + P90e)

Release rate due to PDCH

fast pre-emptionP147 / (P30a + P30b + P30c)

Release rate due to

suspend procedureP98a / (P90a + P90b + P90c +

P90d + P90e + P90f)

Release rate due to

suspend procedureP98b / (P30a + P30b + P30c)

Release rate due to Flush

messageP396a / (P90a + P90b + P90c

+ P90d + P90e + P90f)

Release rate due to Flush

messageP396b / (P30a + P30b + P30c)

KPI

KPI

KPI

Release rate due to Flush message (P396a/b) does not allow to count

TBF releases due to reselection during transfer

▼ DL and UL TBF release: indicators = f(counters)

▼ Other counter related to reselection procedure:� P397: Number of successful reselections in READY STATE (idle or transfer mode). It counts the number of FLUSH

message from SGSN.� This counter can not be used to count the real number of TBF drop radio since it is incremented whether the MS is in

packet transfer mode or not. ▼ Most of the time the FLUSH_LL message arrives from SGSN after the abnormal TBF Release has been detected by the

MFS.


1.203


TBF drop causes

DL TBF UL TBF

Radio problem P302b / (P90a + P90b + P90c +

P90d + P90e + P90f)

Radio problem P302c / (P30a + P30b + P30c)

Radio failure during

radio resource realloc

execution

(P407a + P407b + P407c) / (P90a

+ P90b + P90c + P90d + P90e +

P90f)

Radio failure during

radio resource realloc

execution

(P408a + P408b + P408c) / (P30a

+ P30b + P30c)

Gb problem P11 / (P90a + P90b + P90c +

P90d + P90e + P90f )

Gb problem P24 / ( P30a + P30b + P30c)

N_StagnatingWindow P385a / (P90a + P90b + P90c +

P90d + P90e + P90f)

N_StagnatingWindow P385b / (P30a + P30b + P30c)

Blocking situation P303a / (P90a + P90b + P90c +

P90d + P90e + P90f)

Blocking situation P303b / (P30a + P30b + P30c)

BSS problem (P90a + P90b + P90c + P90d +

P90e + P90f - P146 - P98a -

P396a - P9 - P302b - P11 - P385a

- P303a - P407a - P407b - P407c

) / (P90a + P90b + P90c + P90d +

P90e + P90f)

BSS problem (P30a + P30b + P30c - P22 -

P147 - P98b - P396b - P24 -

P385b - P303b - P408a - P408b -

P408c - P302c) / ( P30a + P30b +

P30c)

UL TBF drop due to BSS problem is in restriction (FR

A45/130281)

▼ DL and UL TBF release: indicators = f(counters)

▼ On a DL TBF:� Radio problem: N3105 exceeds the limit (6) or too low TX efficiency (<10%).� Blocking situation: no reception of the PDAN with Final indicator = 1 at the end of the Downlink TBF during

T_TBF_BCK_REL = 3 seconds (MS error) OR the transmission window of the MFS is stalled during T_TBF_BCK_REL = 3 seconds (radio problem).

� Stagnating window: the RLC counter N_StagnatingWindowDL is incremented when the Same oldest RLC data block in the transmittion window is not acknowledged by the received bitmap of the last Packet Downlink Ack/Nack message. The DL TBF is released because the RLC counter N_Stagnating WindowDL exceeds the system parameter N_STAGNATING_ WINDOW_DL_LIMIT =8 (MS error).

▼ On a UL TBF:� radio problem: N3101 or N3103 exceeds the limits (48 and 1) or too low TX efficiency (<10%).� Blocking situation: Reception of N_UL_Dummy_Limit = 15 dummy UL RLC blocks (MS error or radio problem) OR no

reception of the Packet Control Ack at the end of the Uplink TBF during T_TBF_BCK_REL = 3 seconds (MS error).� Stagnating window: the RLC counter N_StagnatingWindowUL is incremented provided that the receive window is

stalled whenever a UL RLC data block whose BSN is different from the receive window state variable V(Q) and is received a round trip delay after the previous sending of a Packet Uplink Ack/Nack message.The UL TBF is released because the RLC counter N_StagnatingWindowUL exceeds the system parameter N_STAGNATING_WINDOW_UL_LIMIT = 8 (MS error or radio problem).


1.204


Downlink Data Transfer

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Uplink Data Transfer

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▼ The cause of drop during DL data transfer is mainly radio problems▼ The cause of drop during UL data transfer is radio problems + blocking problems (MS error suspected because seen on every

network).


1.205


▼ Thresholds:

� When Delayed DL TBF release is not activated and CS2 is not used at the beginning of TBF:

UL/DL TBF normal release rate is seen as good above 98%

� When Delayed DL TBF release is activated or CS2 is used at beginning of TBF (without optimisation of the coding scheme adaptation):

Threshold of DL TBF normal release rate should be lower.

▼ The QoS threshold values assume that the MS mobility (reselection) is negligible.▼ The typical values for a DL TBF normal release rate:

� When a Delayed DL TBF release is activated: 95%� When a Delayed DL TBF release is activated and CS2 is activated at the beginning of the TBF: 90%

� The longer the TBF duration the higher the probability to drop.� There is a high probability to be in CS2 during the Delayed phase.

▼ The typical values for UL TBF normal release rate:� When CS2 is activated at the beginning of the TBF: 98.3%, 98.9%

� A UL TBF is often short.� The Coding Scheme is always CS1 during the MS contention resolution (based on TLLI) for security.

▼ RLS procedures are active during the delayed phase.


1.206

2.6 Radio link supervision TBF progress, QoS indicators 1/5

▼ DL and UL TBF progress: introduction

TBF establishmentTBF statistics: duration, number, throughput

time

TBF releaseDL TBF: delayed DL TBF release


1.207



TBF statistics

Downlink Uplink

Average TBF duration (P16 / 10) / (P90a + P90b + P90c

+ P90d + P90e + P90f)

Average TBF duration (P29/ 10) / (P30a + P30b + P30c)

Maximum number of TBF

simultaneously established

p35 Maximum number of TBF


p39

Average number of TBF


p36 / 10 Average number of TBF


p40 / 10

Average useful throughput

in kbit/s at RLC level per

TBF

(P55a * N1 + P55b * N2) /

((P16a/10) * 1000)

Average useful throughput

in kbit/s at RLC level per

TBF

(P57a * N1 + P57b * N2) /

((P29/10) * 1000)

Average UL TBF duration (p29) is in restriction (FR A45/133292)

▼ The max nb of TBFs simultaneously established is meaningful per hour or per day.▼ The average nb of TBFs simultaneously established is less reliable due to the difference between the gauge polling period

and the average TBF duration.


1.208


Detailed throughputs on Downlink

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kbit/s perPDCHkbit/s per cell

Detailed throughputs on uplink

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kbit/s per TBF

kbit/s perPDCHkbit/s per cell

▼ DL throughput per TBF under-estimated due to the precision of the cumulated TBF duration (0.1 second), which is higher than the duration of one RLC block (4*240/52 = 18.5 ms). This error margin increases with the area of consolidation and the type of traffic (user/signaling. This indicator should be better interpreted at the cell Busy Hour rather than the averaged value per day in order to avoid the influence of signaling.

▼ UL throughput per TBF biased due to the restriction on P29 (it stays sometimes blocked on a few cells). It cannot be used to follow GPRS QoS on large area.

▼ However, these indicators are interesting to see the evolution of TBF throughput on any area (only for DL) and on small area (for UL).

▼ These indicators are more reliable when the Average TBF duration is high because the error margin has less impact.


1.209



Delayed DL TBF release

Cumulated time of active DL TBF connections P16a / 10

Percentage of time during which the DL TBF

connections are in the “active” state

P16a / P16

Number of DL TBF transfer resumptions in

delayed release state

P422

Rate of DL TBF transfer resumptions per

established DL TBF

P422 / (P90a + P90b + P90c + P90d + P90e + P90f +

P422)

Number of DL RLC blocks containing only

dummy LLC UI Command PDU on PDTCH

P421

Number of DL RLC blocks sent on PDTCH P20a + P20b + P72a + P72b + P55a + P55b + P421

Rate of RLC blocks containing only dummy

LLC UI commands on DL PDTCH

P421 / (P20a + P20b + P72a + P72b + P55a + P55b +

P421)

Load rate induced by DL RLC blocks

containing dummy LLC PDU

P421 / (12 * (P38/10) * (1/0.240))


1.210


DL TBF state

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0

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80 Delay->ActiveSuccess

% Efficiency

% Active

▼ On RNO graphs:

� % Efficiency = Rate of DL TBF resumptions per DL TBF establishments

� % Active = Percentage of time during which the DL TBF connections are in the active state

▼ Typical values of Efficiency rate and Active rate:� Efficiency rate = 40%, 60%� Active rate = 15%, 20%



3. Gb Interface

▼Training objectives: Describe the algorithms, parameters and indicators used on the Gb interface


1.212

3 Gb InterfaceSession Presentation

▼ Objective: Describe the algorithms,parameters and indicators used onthe Gb interface

▼ program:� 3.1 Protocols on Gb interface� 3.2 Down-link flow control on Gb interface � 3.3 QoS indicators




3 Gb Interface

3.1 Protocols on Gb interface


1.214

3.1 Protocols on Gb interfaceLayer 1

▼ Bearer Channels

L1

NS (SNS)

NS (NSC)

BSSGP

MFS

L1

NS (SNS)

NS (NSC)

BSSGP

SGSN

Gb interface

PCM BC i

BC j

PCM

BC y

BC x

▼The Gb physical interface consists of one or more 64 Kbit/s channels on one or more physical lines at 2048 Kbit/s▼Both individual 64 Kbit/s and n*64 Kbit/s channels are supported by the MFS▼A Bearer Channel (BC) is a n*64 Kbit/s channel (1 ≤ n ≤ 31)

▼NB: among the 16 PCM links offered per PCU, 8 only are dedicated to the Gb interface, 4 for the upload and 4 for the download. The maximum transfer capacity point to point aver the Gb interface in one direction is then 31*64Kbit/s*4 = 8192Kbit/s.


1.215

3.1 Protocols on Gb interfaceLayer 2, Network Service 1/3

▼ The Sub-Network Service (SNS) sub-layer is dependent on the transmission network and manages Permanent Virtual Channels (PVCs)

L1

NS (SNS)

NS (NSC)

BSSGP

MFS

L1

NS (SNS)

NS (NSC)

BSSGP

SGSN

Frame Relay NetworkPVCaDLCIx

PVCmDLCIαααα

PVCbDLCIy

PVCnDLCIββββ

Gb interface

▼Concept of PVC:�A PVC is a synchronous access line, semi-permanent connection�the PVC allows the multiplexing on a BC�it is not an end to end link between the MFS and the SGSN�at MFS side a PVC is identified by its Data Link Connection Identifier (DLCI) which is independent of the one defined at SGSN side. DLCI 0 is used for signaling�there is one PVC per BC

▼SNS layer, layer 2.1 in the OSI model, offers the Frame Relay technology. The NSC layer, layer 2.2 in the OSI model, offers the point to point data transfer in both directions.

▼The PVC standards are not specific to GPRS. Please refer to the « Frame Relay Forum » organization, the CCITT and ANSI (T1S1.1 workshop) specifications.


1.216


▼ The Network Service Control (NSC) sub-layer is independent from the transmission network and manages NS Virtual Connections (NS-VCs)

L1

NS (SNS)

NS (NSC)

BSSGP

MFS

L1

NS (SNS)

NS (NSC)

BSSGP

SGSNNSVC

NSVCi=11

NSVCNSVCi=12

Gb interface

▼Concept of NS-VC:�a NS-VC is an end to end logical link between the MFS and the SGSN�each NS-VC is identified by its NSVCI which has an end to end significance on the Gb interface�there is a one to one relation between one NS-VC and one PVC�Sub-network service function: ordered data transfer

▼The main functions of the NSC layer (2.2 layer) are: sequencing of the data transmission, flow control, lost frame management.


1.217


▼ Concept of NSE:

� A Network Service Entity (NSE) groups several NS-VCs (at least 2 NS-VCs per NSE) = the NSE corresponds to the resources of one GPU

� The concept of NSE is useful for the load sharing between the different NS-VCs: the NS-VCs of the NSE are shared by the BVC associated to the NSE

� The NSE is identified by an NSEI which has an end-to-end significance over the Gb interface

NSVCNSVCi=11

NSVCNSVCi=12L1

NS (SNS)

NS (NSC)

BSSGP

PCU

NSENSEi = 1

▼Note: for MM purposes, SGSN needs a 1:1 correspondence NSEI ⇔ RA

2 Mbit/s 2 Mbit/s

BC BC BC

Physical layer

PVC PVC PVCSNS sub-layer

NS-VC NS-VC NS-VC

NSE

NSC sub-layer

BVC BVC BVC sigBSSGP layer

Cell Cell

BSS


1.218

SNS

NSC

BSSGP

SGSN

3.1 Protocols on Gb interfaceLayer 3, BSSGP

▼ BSSGP Virtual Connection (BVC): end to end link between the MFS and the SGSN

L1

SNS

NSC

BSSGP

MFS

L1

Gb interface

NSVC

BVCi=1

BVCi=2

BVCi=n BVCi=1

BVCi=2

BVCi=n

▼Two types of BVC:�point to point BVC dedicated to the PS traffic of one cell (BVCi ≠ 0)�signaling BVC (BVCi=0)which is the signaling circuit of all the point to point BVCs of one NSE (GPU)

▼ For NM reason, the duplet BVCi/NSEi must be unique within a SGSN

▼ To activate a new cell in a SGSN, it is only needed to add a new BVCi in a NSEi. No update of the NSEiinformation is necessary.


1.219

NSE2

SGSN

NSE1NSE1

NSE2

F.RF.RNetworkNetwork

PCM

3.1 Protocols on Gb interfaceProtocol Model and Manageable Entities 1/2

PCM

PCM

BVCI=2

BVCI=1

BVCI=3

BVCI=5

BVCI=6

BVCI=4

BSC1

BSC2

GPRS Core Network sideBSS side

BC PCMBCPVC

BC BCPVC

NSVC1

NSVC2

PCM

PCM

PCM

BC PCMBCPVC

BC BCPVC

NSVC3

NSVC4

BVCI=2BVCI=2

BVCI=1BVCI=1

BVCI=3BVCI=3

BVCI=5BVCI=5

BVCI=4BVCI=4

BVCI=6BVCI=6

▼ In B8 apply the followig dimensioning rules:

Gb interface

Max. number of Gb interface physical linksper GPU

nGb nGb + nAter(mux) ≤ 16 where nAter(mux)

Max. number of Frame Relay bearerchannels per physical link

31

Max. number of Frame Relay bearerchannels per GPU board

124

Max. number of BVCs per GPU board 265 Lim it due to the number of cells per BSS(264) + one signalling BVC (1)

Number of signalling BVCs per GPU 1 1 NSE is defined per GPU

Ater interface

Maximum number of 64 kbit/s signallingchannels (GSL) per GPU

4

Number of Ater(mux) PCM links betweenone GPU and one BSC

nAter(mu

x)

nGb + nAtermux ≤ 16

Atermux sharing granularity for PS traffic g g can be set to:100 % AterMux, or75 % AterMux, or25 % AterMux, or12.5 % Atermux for GPRS traffic

Max. number of BSSs per MFS 22

Max. number of GPUs per MFS 30

Max. number of BSS per GPU board 1

Max. number of cells per MFS 2000

Max. number of TBFs per GPU 960

Maximum number of GPU boards per BSS 6


1.220

3.1 Protocols on Gb interfaceProtocol Model and Manageable Entities 2/2

SGSNPacket Control Unit function(PCU)

BSS GPRS Protocol(BSSGP)

BSS GPRS Protocol(BSSGP)

Network Service Control(NSC)

Network Service Control(NSC)

BVCI=2BVCI=2

BVCI=1BVCI=1

BVCI=3BVCI=3

BVCI=5BVCI=5

BVCI=6BVCI=6

BVCI=4BVCI=4

BSC1

BSC2

GPRS Core Network sideBSS side

Sub-Network Service(SNS)

Physical layer

Sub-Network Service(SNS)

Physical layer

Frame Relay

BVC

NS-VCNSE

PVCBC


1.221

3.1 Protocols on Gb interfaceBSSGP Frame

▼ One BSSGP PDU includes one and only one LLC PDU

GPRS Traffic or signalingTLLIBVCI

LLC frame

BSSGP frame

LLC header

BSSGP header

LLC payload

▼ In case of traffic data the LLC PDU contains a SNDCP PDU▼ In case of signaling the LLC PDU contains a GMM or SM message



3 Gb Interface

3.2 Down-link flow control on Gb interface


1.223

3.2 Down-link flow control on Gb interface Principle

▼ Only DL flow control is performed between the BSS and the SGSN

▼ principle of the DL flow control mechanism:

� the BSS sends to the SGSN the flow control parameters in the FLOW-CONTROL-MS/BVC messages

� the flow control parameters allow the SGSN to locally control its transmission towards the BSS

PayloadTLLIBVCI

LLC frame

BSSGP frame

Used to perform MS flow controlUsed to perform BVC flow control

▼ Caution: LLC frames are encapsulated 1:1 into BSSGP frames. This is the reason why we can say that there is a LLC frame flow control mechanism at BSSGP level.


1.224

3.2 Down-link flow control on Gb interface Flow control performed at SGSN side (1/2)

▼ the SGSN must perform flow control on each BVC and on each MS

▼ the flow control is performed on each LLC PDU first by the MS flow control mechanism and then by the BVC flow control mechanism:

� if a LLC PDU is passed by the MS flow control then the SGSN applies the BVC flow control to the LLC PDU

� if a LLC PDU is passed by both flow control mechanisms, the entire LLC PDU is delivered to the BSS

MS flow control MS flow control MS flow control

BVC flow control

BSS


1.225

3.2 Down-link flow control on Gb interface Flow control performed at SGSN side (2/2)

▼ leaky bucket algorithm:

� a LLC PDU is passed as long as the bucket counter (B) plus the length of the LLC PDU does not exceed the bucket size (Bmax)

� when the LLC PDU is passed its length is added to B

� any LLC PDU not passed is delayed until B plus the LLC PDU length is less than Bmax

� the algorithm takes into account the leak rate of the bucket (R)

▼ Leaky bucket principle

bucket size (B)

Max bucket size (Bmax)

leaking rate (R)

new LLC PDU?


1.226

3.2 Down-link flow control on Gb interfaceFlow control performed at BSS side (1/3)

▼ the BSS controls the DL transmission of the SGSN by sending the parameters Bmax and R in the flow control PDU:� after the sending of a FLOW_CONTROL_BVC PDU the

BSS cannot send a new FLOW_CONTROL_BVC PDU before T_Flow_Ctrl_Cell sec� T_Flow_Ctrl_Cell is a BSS parameter�Default value = 0�By default BVC flow control is disabled

� after the sending of a FLOW_CONTROL_MS PDU the BSS cannot send a new FLOW_CONTROL_MS PDU before T_Flow_Ctrl_MS sec� T_Flow_Ctrl_MS is a BSS parameter�Default value = 10sec

▼ NB: the cell flow control is performed more frequently than the MS flow control because

� The radio resource availability for a TBF is always shorter than the guarding time of a PDCH, therefore the MS individual traffic is less of an influence on the leaking rate� The radio resource available for one MS can change from one TBF to another� The combine traffic of all the GPRS MS in the cell exchanging data with the SGSN has to be mapped onto a BVC, which can become the blocking factor as the BVC is mapped on a NSVC, which is mapped on a PVC, carried by a BC which has a fixed maximum capacity


1.227

3.2 Down-link flow control on Gb interfaceFlow control performed at BSS side (2/3)

▼ FLOW_CONTROL_BVC PDU:

� BVC_Bucket_Size: maximum size of the cell buffer in the MFS

� BVC_Bucket_Leak_Rate: measured throughput in the cell from RRM to RLC

� Bmax_default_MS: default value of the maximum size of the MS buffer in the MFS

� R_default_MS: default value of the measured throughput for the MS from RRM to RLC

▼ Formulas:� BVC_Bucket_Size = Flow_Dim_safety_BVC * (Nb_pdch_cell + 1) * Max_Rate_PDCH * T_Flow_Ctrl_cell� BVC_Bucket_Leak_Rate = Data_cell / T_Flow_Ctrl_cell� Bmax_default_MS = Flow_Dim_safety_MS * Max_Rate_PDCH * T_Flow_Ctrl_MS� R_default_MS = Max_Rate_PDCH


1.228

3.2 Down-link flow control on Gb interface Flow control performed at BSS side (3/3)

▼ FLOW_CONTROL_MS PDU:

� MS_Bucket_Size: maximum size of the MS buffer in the MFS

� MS_Bucket_Leak_Rate: measured throughput for the MS from RRM to RLC

▼ Formula:� MS_Bucket_Size = Flow_Dim_safety_MS * Σi=1,n (Max_Rate_PDCH i / Nb_TBF i) * T_Flow_Ctrl_MS� MS_Bucket_Leak_Rate = Data_MS / T_Flow_Ctrl_MS

▼ Explanation:� Max_Rate_PDCH i is the maximum rate the MS can reach on PDCH i,� Nb_TBF i is the number of DL TBF on PDCH i,� Max_Rate_PDCH i / Nb_TBF i represents the maximum rate the MS can reach on PDCH i taking into account the sharing with other TBF,

▼ Data_MS is the number of bits transmitted from RRM to RLC by the MS since the previous FLOW_CONTROL_MS message related to the MS



3 Gb Interface

3.3 QoS indicators


1.230

3.3 QoS indicators Gb interface, BVC resource 1/3

▼ BVC indicators: introduction

BVC Number of DL LLC bytes

Number of UL LLC bytes

Received from SGSN

Discarded due to congestion

Discarded due to Suspend procedure

Received from MS

Rerouted

Not rerouted

Well received from SGSN


1.231


▼ BVC: indicators = f(counters)

BVC (cell)

Downlink Uplink

Number of DL LLC

bytes received from

SGSN

P43 Number of UL LLC

bytes received from

MS

P44

Number of DL LLC

bytes discarded due to

congestion

P10

Average DL useful

throughput in kbit/s

((P43 - P10) * 8) / (GP

* 1000)

DL LLC congestion

rate

P10 / P43

Number of DL LLC

bytes discarded due to

suspend procedure

P99

% of DL LLC bytes

discarded due to

suspend procedure

P99 / P43

Downlink LLC bytes

well rerouted

P95

DL LLC bytes not

rerouted

P96

DL LLC bytes well

received

P43 - P10 - P96

DL LLC bytes well

received rate

(P43 - P10 - P96) /

P43

▼ LLC bytes discarded: relating to PDU LifeTime expiry or GPU buffer congestion (canbe linked to degraded DL Flow Control algorithm).

▼ P99: The introduction of the Suspend-Resume mechanism between the MFS and the SGSN can generate GPRS QoSproblems. If the suspend time exceeds the tolerable threshold for the distant server the MS is connected to, it can generate disconnection from the server. Even though, the disconnection does not mean that the PDP context is deactivate. It belongs to IP GSS feature (capacity to generate dummy IP blocks to keep the Gi link alive).

▼ P96 is likely to be sensitive to a lot of reselection problem a MS has to face in the GPRS network (no GPRS resources available in the selected cell, reselection of a MS in a new cell belonging to a new MFS or a new SGSN, etc…).


1.232


Details of downlink LLC traffic

0

1000000

2000000

3000000

4000000

5000000

6000000

7000000

8000000

9000000

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03

98.498.698.899

99.299.499.699.8100

100.2 Blocked bytes

DiscardedbytesNot rerouted

ReroutedbytesReceivedbytes%Well receiv

Details of uplink LLC traffic

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

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03

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03

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03

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03

UL sent bytes


1.233

3.3 QoS indicators Ater interface, GCH resource

▼ GCH indicators: introduction

▼ GCH: indicators = f(counters)

GCH Average/Maximum number of busy GCH

GCH

Average number of busy GCH P100 / 10

Maximum number of busy GCH P102 / 10

Atermux congestion duration due to a lack

of GCH_16 transmission resources on the

Atermux interface

P383a

% of time the GPU is in Ater congestion state P383a / GP

Cumulated/% of time in AterMux congestion situation

▼ New in B7: P100, P102, P383a are provided per GPU.


1.234

▼ GPRS radio resources: GPU

GPU counters Overall traffic

Processing limitation, GCH interface

3.3 QoS indicators GPU resource


1.235

3.3 QoS indicators GPU resource, GPU usage

GPU traffic

Number of LLC PDU transferred (UL+ DL) P104

Number of UL+DL TBF establishment requests

per GPU

P107

Number of UL+DL TBF establishment successes

per GPU

P106

(UL+DL) TBF success rate per GPU (P106 / P107) * 100

Number of PS PAGING request per GPU P391a

Number of CS PAGING request per GPU P391b

▼ GPRS radio resources: GPU usage

▼ New counters in B7: P104, P107, P106, P391a, P391b are provided per GPU.


1.236

3.3 QoS indicators GPU resource, GPU load

GPU load

DSP congestion duration (in seconds). P384 / 10

Percentage of time during which the DSP is in

congestion

P384 / 10 / GP

Cumulative time during which the GPU stays in

the PMU CPU critical load state due to PMU

CPU power limitations

P402a / 10


the PMU CPU critical or severe load state due to

PMU CPU power limitations

P402b / 10


the PMU CPU high or critical or severe load state

due to PMU CPU power limitations

P402c / 10

Percentage of time during which the GPU stays

in the PMU CPU overload state due to PMU

CPU power limitations.

P402c / 10 / GP

Average PMU CPU power budget of the GPU P76a / 10

Maximum PMU CPU power budget of the GPU P77a / 10

▼ GPRS radio resources: GPU load

▼ New counters in B7: P384, P402a, P402b, P402c, P76a, P77a are provided per GPU.



4. Quality of Service

▼Training objectives: ▼ - Describe the GPRS QoS profiles, ▼ - Describe the OMC-R indicators used for the QoS evaluation of a GPRS network▼ - Describe the way to follow the QoS of a GPRS network


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4 Quality of ServiceSession Presentation

▼ Objective:- Describe the role of the BSS in the GPRS QoS monitoring - Describe some Key Performance Indicators for the GPRS QoS evaluation of the Alcatel BSS

▼ program:

� 4.1 QoS theory

� 4.2 QoS follow-up: principles and tools

� 4.3 Main QoS indicators and reference values

▼ Sub-chapters are not displayed on this slide




4.1 QoS theory


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4.1 QoS theory GPRS QoS requirements 1/2

▼ Different applications require different QoS:

� video: fixed transmission delay, high bandwidth

� Web browsing, email notification: delay sensitive, variable throughput allowed

� file transfer (FTP): variable delay allowed, good total throughput

� E-Mail delivery: not very sensitive to delay and throughput parameters

� ...

▼Data applications have very different traffic characteristics (amount of data, duration between LLC PDU) leading to different ways of triggering of the radio layers algorithms. This has a direct impact on the follow-up of some OMC-R QoS indicators: number of DL/UL TBF establishment requests, DL/UL TBF duration, coding scheme distribution


1.241

4.1 QoS theory GPRS QoS requirements 2/2

▼ Data applications use TCP/IP protocol layers which have a great impact on the end-user QoS

(*)

First IP router Last IP router

GTP

relay

SNDCPP

BSSGPRLC BSSGP

relay

relay

SNDCPP

PPP

FTP

TCP

IP

PPP

LLC

RLC

MAC

RF

MAC

RF

NS

L1

NS

L1

LLC UDP

IP-Gn

L2

L1’

UDP

IP-Gn

L2

L1’

IP

relay

IP

GTP

IP

relay

IP

relay

IP

UmRGb

Gn GiTE (PC,PDA …)

MSBSS

SGSNGGSN

Possible repartition on the end to end path of the TCP flight size

TCP data segment

TCP acknowledgement

(*) this graphical representation is used toexpress the fact that many data segments arecurrently waiting to be transmitted on therepresented link and are stored in buffers of thedevice handling the link . It doesn’t mean thatsimultaneous segments are being transmitted.

FTP above TCP/IP layers


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4.1 QoS theory Different levels of QoS

GGSN

GPRS GPRS

BackboneBackbone

PacketPacket

DataData

NetworkNetwork

GbGbGbGb

SGSN

A935A935A935A935MFSMFSMFSMFS

BSCBSCBSCBSC

AterAterAterAter

BTS

AbisAbisAbisAbis

BSS

GPRS QoS

GnGnGnGn GiGiGiGiUmUmUmUmRRRR

Radio QoS

User QoS

TETE

▼3 types of QoS in involves in the overall analysis of the QoS of the GPRS service:�the radio QoS

�it must be considered from the R interface to the Gb interfaceit mainly belongs to the radio environment as well as the well as the proper functioning of the PCU implemented inside the BSS�defined in terms of throughput, service precedence, RLC reliability mode, transfer delay

�The GPRS QoS�It must be considered from the R interface (MS access the GPRS) to the Gi interface (exit of the GPRS Network)�It includes the Radio QoS and the GSS QoS�defined in terms of service precedence, transfer delay, mean and peak throughputs and reliability

�The end-user QoS�This is the QoS as the user feels it.�It includes the GPRS QoS as well as the QoS of the external networks and their connection to the GPRS GSS�Should it not belongs to the operator, it should still be monitored as it can generate customer complains


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4.1 QoS theory GPRS QoS profile 1/2

▼ ETSI R’97 principles:

� GPRS QoS is negotiated between the MS and the SGSN, at PDP context activation

� the BSS is not involved in QoS negotiation

� no absolute QoS can be guaranteed by the BSS

� SGSN and GGSN play the main role in QoS management


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4.1 QoS theory GPRS QoS profile 2/2

▼ 5 GPRS QoS attributes in the R’97 standard:

� Precedence Class: relative importance of service under congestion; 3 values are defined

� Delay Class: total delay measured between R or S point and Gi; 4 values are defined

� Reliability Class: mainly linked to Ack / Not Ack modes at RLC and LLC levels and within the backbone network; 5 values are defined

� Peak Throughput Class: measured at Gi and R reference points;9 values, ranging from 8 Kbit/s up to 2048 Kbit/s

� Mean Throughput Class: measured at the Gi and R reference points; 19 values, ranging from Best Effort up to 111 Kbit/s

▼Precedence classes: high, normal, low

▼Delay classes: �class 1 (average delay<0.5 sec, 95% delay<1.5 sec)�class 2 (average delay<5 sec, 95% delay<25 sec)�class 3 (average delay<50 sec, 95% delay<250 sec)�class4: not specified = “best effort

▼The Mean Throughput class range is smaller than the Peak Throughput class one because �The later is considered per interface (the purpose being to maximize the use of the transmission capacity over each interface according to its physical characteristics)�The former is considered end to end and must take into account the weaker interface characteristics, the air interface one

▼Reliability: Five classes are defined according to the tolerable BER (from 1 = lowest BER required to 5 = highest tolerated BER and no acknowledgement or error checking).


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4.1 QoS theory Radio QoS profile

GGSN

GPRS GPRS

BackboneBackbone

PacketPacket

DataData

NetworkNetwork

GbGbGbGb

SGSN

A935A935A935A935MFSMFSMFSMFS

BSCBSCBSCBSC

AterAterAterAter

BTS

AbisAbisAbisAbis

BSS

GPRS QoS

GnGnGnGn GiGiGiGiUmUmUmUmRRRR

Radio QoS

User QoS

TETE

▼Throughput: not managed by Alcatel BSS in B7. The allocation strategy consists in trying to allocate to the MS as many PDCHs as supported by its multislot class if such information is known. The operator can limit the maximum number of PDCHs allocated to a TBF through O&M configuration

�useful throughput expected on the radio interface�specified on:

�DL path: in DL BSSGP PDU header�UL path: peak throughput class in “Packet resource request” (2 phases access)

▼Service precedence: not managed by Alcatel BSS in B7�defines the priority for maintaining service under congested situation�specified on:

�DL path: in DL BSSGP PDU header�UL path: radio priority in “Packet resource request” (2 phases access)

▼RLC reliability mode: managed by the BSS.�RLC Ack or RLC NAck�specified on:

�DL path: in DL BSSGP PDU header�UL path: in “Packet resource request” (2 phases access)�Default mode: Ack

▼Transfer delay: Best effort is supported. PDU Lifetime is taken into account for DL LLC PDU. As many TS as requested according to the MS Multislot Class are allocated if possible.

�a requirement is provided for DL LLC PDU via the PDU lifetime�PDU lifetime is expected to be configured by SGSN according to GPRS transfer delay class of associated PDP context




4.2 QoS follow-up: principles and tools


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4.2 QoS follow-up: principles and toolsGSM and GPRS QoS dependencies 1/2

GSM QoS

Impact of GPRS on GSM

GPRS QoS


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4.2 QoS follow-up: principles and toolsGSM and GPRS QoS dependencies 2/2

▼ GPRS QOS is not an isolated topic:

� It is necessary to use GSM indicators in order to complete the analysis of GPRS QoS

� It is necessary to use GSM counters in order to complete the analyze of the impact of GPRS traffic on GSM QoS

▼ The BSS QoS does not allow to have a complete understanding of the end to end QoS seen by the user

� Indeed, upper protocol layers (TCP for example) have a great impact on the global QoS

� The GSS also has a great impact on the global QoS

▼Use of GSM indicators :�Example:

�high number of TBF establishment failures due to radio problems ⇒ check with GSM counters if there are interferences (quality HO, better cell HO)�high number of TBF establishment failures due to radio congestion ⇒ check with GSM traffic information (traffic load info: Traffic HO, half rate, SD congestion, TCH congestion…)

▼Use of GSM counters:�Check:

�CCCH load due to GSM and GPRS (PCH, AGCH, RACH)�TCH congestion & TCH Erlang evolution for CS according to GPRS radio resource parameter (MIN_PDCH, MIN_MPDCH, evolution of MAX_PDCH_DYN …)�call establishment success rates after CS paging on PCCCH

▼GSS view :�Example of a DL FTP transfer:

�during a DL FTP transfer, a lot of UL TBF are established for the acknowledgements of DL IP packets�⇒ if the acknowledgements are not received, the transfer can be aborted�if the GSS does not send data regularly to the BSS, a DL FTP Flow is quickly interrupted ⇒ a new DL TBF must be established (possibly using the CCCH) = Radio resource can change + server reboots


1.249

4.2 QoS follow-up: principles and tools QoS breakdown

Radio interface

Gb interface

Ater interface

TBF establishment

TBF release

Throughput information

BSSGP mechanismsTCP/IP stats and follow-up

MM informationCongestion situation

Allocation de-allocation

RLS mechanism

CS Adaptation


1.250

4.2 QoS follow-up: principles and tools Principles

▼ Define a set of default parameters

� Allow GPRS traffic on all the TRXs of the cell

� GPRS_PREF_MARK ≠ 0

� Define a strategy to share the GSM/GPRS resources

� MIN_PDCH, MAX_PDCH, MAX_PDCH_HIGH_LOAD

▼ Check parameters setting consistency

� Compare default values with OMC-R values

▼ Monitor the main QoS indicators (see after)

▼ Check the end-user QoS

� GPRS performance tests (Ping, FTP transfer, WAP and WEB pages download)

▼ Monitor GPRS Attach, RA Update, PDP Context Activation

� SGSN indicators, Gb traces


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4.2 QoS follow-up: principles and tools Tools 1/2

▼ GPRS performance tests

� Use of a local server on Gi interface (just after GGSN) mandatory

� Use of a too old or a too new mobile can be risky

�Reference mobiles are Sagem (OT96, PW959, OT190), Motorola (T260, T280), Siemens (S45)

� Use of a PC preferably with Windows 2000

� Use of the Agilent software E6474A Nitro

� to pick up the transferred frames � to calculate the throughput at RLC layer

� Use of database to register performance results

▼GPRS performance tests must be performed in very good conditions on the field:�good received level, no quality problem (close to BTS site)

�This can be checked with GSM traces at mobile side�dedicated and fixed time slots to GPRS (MIN_PDCH = 4)

�It must be verified at MFS terminal that these fixed time slots are always consecutive and placed on the best TRX for GPRS

�preferably, only the test mobile on these time slots (N_TBF_PER_SPDCH = 1 and MAX_PDCH = 6 or more)�It can be checked at MFS terminal that the test mobile is alone on the fixed GPRS time slots during the test.

�no cell reselection during the test (to be checked through GSM mobile traces in idle mode)�In dual band networks, it is quite important to verify where the test mobile camps in packet idle and packet transfer mode.


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4.2 QoS follow-up: principles and tools Tools 2/2

▼ Gb Traces

� Use of a protocol analyser to capture the Gb messages

� Tektronix K1205 (with relevant protocol stacks)�Kompass (allows indicators computation)

▼ Main indicators

� Use of RNO

�GSM/GPRS counters and indicators�Specific GPRS QoS reports

▼Post-processing of Gb traces :�equivalent to GSM A traces�useful in order to analyze GMM/MM procedures:

�RA updating, GPRS attach/detach, PDP context activation/de-activation, DL flow control�Follow-up of BSSGP messages:

�Radio status, status, LLS discarding, reselection occurrence, flow control mechanisms




4.3 Main QoS indicators and reference values


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4.3 Main QoS indicators and reference values Introduction

▼ GPRS counters are computed in the MFS and periodically reported to the OMC-R (Granularity Period, 1 hour)

▼ There are Timers and two types of counters:� COUNTER:

� associated to an event� incremented by 1 when the later occurs� reset at the end of the Granularity Period

� TIDE-MARK (computed over a gauge period):� incremented or decremented�Min, Max values during the reporting period�Reset at the end of the Granularity Period

� AVERAGED GAUGE� TIMER


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4.3 Main QoS indicators and reference values QoS indicators breakdown

Similarities with GSM: Connection successConnection drop

Congestion

Specific GPRS QoS:Throughput

Transmission aspectsGPRS signaling

Impact on GSM QoSResources sharing

-Useful Throughput

-Average and Peak Throughput

-PACCH/PDTCH occupancy

-CS1/CS2

Traffic Load monitoringPCH and AGCH use

Paging success for class B

TBF establishment phaseTBF release causes

Radio/Gb congestion


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4.3 Main QoS indicators and reference values MFS Indicators

< 1%< 2%PDTCH RLC block retransmission rate

> 5%≥ 40%PDTCH RLC block CS2 / (CS1+CS2)

ratio

1 phase access: < 450ms

2 phase access: < 1050ms

<

1200msAverage TBF establishment duration

Average useful throughput per TBF

(Kbit/s)

> 95%> 95%TBF acceptable release rate

> 95%> 95%TBF normal release rate

Number of TBF establishment requests

> 85%> 95%TBF establishment success rate

ULDL

Reference Values

▼The low value of the UL TBF establishment success rate can be due to:� Phantom RACH.� Wrong value of TX_INTEGER (ALCATEL recommendation = 50).

▼The average TBF establishment duration values are given for the B6 release.

▼TBF acceptable release rate:� TBF acceptable release number = TBF normal release number + TBF abnormal release number due to Fast Pre-emption, reselection or Suspend.�TBF acceptable release rate is always equal or greater than the TBF normal release rate.

▼PDTCH RLC block CS2 / (CS1+CS2) ratio is very sensitive to:� GPRS traffic type (FTP transfer, WAP browsing, etc.).� Parameters setting (TBF_DL_INIT_CS, TBF_UL_INIT_CS).

▼GPRS traffic is considered as significant in a cell when the Number of DL TBF establishment requests is > 2000 / day.▼Typical values of DL TBF partial establishment success rate are:

�Without congestion (GSM+GPRS): less than 10% of the total of establishment successes.�With some congestion: between 10 and 20%�With high level of congestion: more than 20%

▼ But these values depend on the penetration rate of MS with 4 TS on the downlink (class 8,10). Computed from counters

�P160 = Nb of 1 slot DL TBF establishment success (1 slot requested and provided)�P162 = Nb of 2 or 3 slots DL TBF establishment success (all slots requested were provided)�P164 = Nb of 4 or 5 slots DL TBF establishment success (all slots requested were provided)�P166 = Nb of 2 or 3 slots DL TBF establishment partial success (less slots provided than requested )�P168 = Nb of 4 or 5 slots DL TBF establishment partial success (less slots provided than requested )


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4.3 Main QoS indicators and reference values Radio & Gb Interface Indicators

> 95%RA Update success rate

> 95%PDP Context Activation success rate

> 95%GPRS Attach success rate

Reference Values (Radio & Gb)

> 5%≥ 40%PDTCH RLC block CS2 / (CS1 + CS2)

ratio

< 1%< 2%PDTCH RLC block retransmission rate

ULDL

Reference Values (Radio)

▼In case of bad GPRS Attach success rate: investigation can be performed using the average GPRS Attach duration.

▼In case of bad PDP Context Activation success rate: investigation can be performed using the average PDP Context Activation duration.

▼PDTCH RLC block CS2 / (CS1+CS2) ratio is very sensitive to:� GPRS traffic type (FTP transfer, WAP browsing, etc.).� Parameters setting (TBF_DL_INIT_CS, TBF_UL_INIT_CS).


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4.3 Main QoS indicators and reference values End-user Indicators

��Cutoff rate during loading

��Number of FTP transfer

attempts

��DL: 5.4 Kbytes/s

UL: 1.3 Kbytes/sAverage throughput

5s��Average loading time

��Average connection time

��Number of connection

attempts

��Connection setup failure rate

��Average time

��Success rate

WAPHTTPFTPPing

▼FTP test results in European network:�Performed with Siemens S45 and Samsung Q100 and a local server �Motorola core network�PC with Windows 98 (MTU = 1500 bytes, TCP window size = 16384 bytes) and with Windows 2000 (default TCP parameter values)

▼the throughput reference values are given for a 3+1 MS.

▼ In case of problem to ping the external server: investigation can be performed using the average Ping Gb time to distinguish if the misbehavior is due to GPRS core network or external PDN.



5 Case studies


1.260

5 Case studiesSession Presentation

▼ Objective: Describe some algorithms or parameters having an impact on the end-user GPRS QoS, from real tests

▼ program:

� 5.1 PDU lifetime and TCP performance

� 5.2 TCP window size and FTP performance

� 5.3 DL TBF Release and end-user performance



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5.1 PDU lifetime and TCP performanceBad FTP performance

Time

FTP Throughput

Congestion Window increase CW decrease

CW increase CW decrease

▼ What is observed


1.262

5.1 PDU lifetime and TCP performanceImpact of TCP congestion algorithm on DL LLC data flow

TCPserver

SGSN GGSN

TCPserver

SGSN GGSN

MFS

MFS

PDU Life Time

TCP/IP frames

TCP/IP frames

LLC frames

LLC frames

TCP Window = 16KB

TCP Window = 64KB

▼We observe a break within each FTP transfer

▼We observe within the Gb traces several "LLC Discarded" messages , just before TCP starts retransmissions . Those "LLC discarded" messages show that several kilobytes of data are discarded by the BSS.

▼This LLC frame discarding is caused by a "PDU lifetime" timer expiry: indeed this parameter is set by the SGSN to ** 8 seconds **

▼Clearly this value is not enough as the RTT (TCP round trip time) with a TCP window of 64 K is roughly 12.3 seconds

▼As most of the RTT is composed of queuing in the BSS buffers , this inevitably causes PDU lifetime expiry

▼This is a normal behaviour as at the beginning of a transfer the FTP server increases continuously its congestion window. The BSS has to send more and more data with the same radio bandwidth.


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▼ Solution

� Increase PDU Life Time (SGSN parameter)

5.1 PDU lifetime and TCP performanceSolution

MFS

FTPserver

SGSN GGSN

PDU Life Time

TCP/IP framesLLC frames

TCP Window = 64Ko


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5.2 TCP window size and FTP performance Definitions

▼ TCP/IP packet:

� MSS: The maximum number of user data bytes that can be included in the packet without fragmentation.

� MTU: The maximum number of bytes that can be sent in a single packet.

� TCP window size : period used for acknowledgment. Its value is a multiple of the MSS (x4, 8, 16, 32). The maximum value is 65.535 (64Kbytes).

MSS

MTU

TCP/IP Header

40 bytes

▼ MSS: Maximum Segment Size.

▼ MTU:Maximum Transmission Unit

▼ Too large an MTU size can mean retransmissions if the packet encounters a router that can't handle that large a packet. Too small an MTU size means relatively more header overhead and more acknowledgements that have to be sent and handled.


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5.2 TCP window size and FTP performance Impact of MSS on FTP throughput

▼ Maximum throughput obtained with MTU = 1500bytes and TCP window size = 8 (x1460bytes).

▼The throughput has been calculated at the application layer.

▼N* is the number which permits to reach by multiplying the MSS a Window Size close to the maximal allowable value of 65.535 Bytes.

▼ The downloaded file has a size of 1 Mbytes.

▼ The table below illustrates the results:

▼ 1500 Bytes is the best MTU size because it permits to reach the maximum throughput value. But it is important to note that even MTU size is set to 500 Bytes the throughput can reach a high value close to the maximum.

▼The asymptote characterizing the graph can be explained by the fact that GPRS network limits the throughput. Even if the client can receive many TCP packets without acknowledging them, the file downloading can not be faster.▼The recommended value of MTU size should be 1500 Bytes. This value is the best because the TCP window size, which permits to reach the maximum throughput, is the smallest. In fact with a small TCP window size retransmission can be avoided.

MSS Multiplying

Integer

MTU of 500 Bytes MTU of 576 Bytes MTU of1000 Bytes MTU of 1500 Bytes

4 1.391 1.628 2.95 2.91

8 2.681 2.952 4.016 4.111

16 3.812 3.877 4.045 4.113

32 3.813 3.878 4.043 4.125

N* 3.808 3.88 4.051 4.092


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▼ End-user QoS is improved

▼ But consider the impact on BSS GPRS QoS indicators

� Decrease of the DL TBF establishment requests

� Increase of the average duration of a DL TBF

� Increase of the DL TBF abnormal release rate

5.3 DL TBF Release and end-user performanceImpact on end-user QoS

45%5.6 sec10.1 secAvg WAP service access time

8%10.8 Kbit/s/TS10.0 Kbit/s/TSDL Avg FTP throughput

33%2.33 sec3.48 secPing Avg time

GainDELAY_DL_TBF_REL =

Enabled

DELAY_DL_TBF_REL =

Disabled


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6.27 sec5.11 secAverage duration of a DL TBF in active state

29.26 sec5.11 secAverage duration of a DL TBF (active plus inactive

states)

1702912997Number of DL TBF establishment successes

1546612636Number of DL TBF normal releases

9.18%2.78%DL TBF abnormal release rate

21.41%99.99%DL TBF activity ratio (p16a/p16)

1.97%2.78%ratio of abnormal releases during the active state of

the DL TBF

10669466379Cumulated time of active DL TBF connections (p16a)

49821566386Cumulated overall time of DL TBF connections (p16)

DELAY_DL_TBF_REL

= Enabled

DELAY_DL_TBF_REL

= Disabled

5.3 DL TBF Release and end-user performanceImpact on BSS GPRS QoS indicators

▼ Increase of the DL TBF abnormal release rate is a normal behavior

▼ In this case, in average, a DL TBF is active about 21% of the overall duration of a DL TBF.

▼ It is interesting to compute the ratio of abnormal releases during the active state of the TBF because it represents the real subscriber impact.



6 Appendix


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6 Appendix

▼ Content:� 6.1 MS multislot class� 6.2 MPDCH location� 6.3 Power control Graph� 6.4 QOS indicators logical diagram� 6.5 OMCR-B7 screen display� 6.6 Allocation/de-allocation of radio resources � 6.7 Immediate re-allocation� 6.8 Immediate re-allocation (execution protocol)� 6.9 Review of PDCH resource management in MFS� 6.10 Training exercises solutions



1.270

6 Appendix6.1 MS multislot class

▼MS type�Type 1 are simplex MS, i.e. without duplexer: they are not able to transmit and receive at the same time�Type 2 are duplex MS, i.e. with duplexer: they are able to transmit and receive at the same time

▼Rx �Maximum number of received time slots that the MS can use per TDMA frame. The receive TS must be allocated within window of size Rx, but they need not be contiguous. For SIMPLEX MS, no transmit TS must occur between receive TS within a TDMA frame. This does not take into account measurement window (Mx).

▼Tx �Maximum number of transmitted time slots that the MS can use per TDMA frame. The transmit TS must be allocated within window of size Tx, but they need not be contiguous. For SIMPLEX MS, no receive TS must occur between transmit TS within a TDMA frame.

▼SUM �Maximum number of transmit and receive time slot (without Mx) per TDMA frame

▼Meaning of Ttb, Tra et Trb changes regarding MS types.�For SIMPLEX MS (type 1):

�Ttb Minimum time (in time slot) necessary between Rx and Tx windows�Tra Minimum time between the last Tx window and the first Rx window of next TDMA in order to be able to open a measurement window�Trb same as Tra without opening a measurement window

�For DUPLEX MS (type 2):�Ttb Minimum time necessary between 2 Tx windows belonging to different frames�Tra Minimum time necessary between 2 Rx windows belonging to different frames in order to be able to open a measurement window�Trb same as Tra without opening a measurement window


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6 Appendix6.2 MPDCH location

▼ MPDCH location

� PBCCH established on PDCH group available with the highest GPRS_PREF_MARK

� TS location of Primary and Secondary MPDCH:

� IF Primary_MPDCH on TS0-TS3 THEN Secondary_MPDCH on any TS

� IF Primary_MPDCH on TS4-TS7 THEN Secondary_MPDCH on TSn with n>k-4 according to GPRS_PREF_MARK

� MS receives PPCH only on one MPDCH, identified by the PCCCH Group. There are BS_PCC_CHANS MPDCH groups

▼MPDCH allocation constraint for concentric cell design: always in the outer zone▼TS location for Primary and Secondary MPDCH:

P rim ary M PDCH

Locatio n

P o ssib le S econdary M PDCH

Loca tion

T S0 -T S3 T S0 , T S1 , T S2 , T S3 , T S4 , T S5 , T S6 , T S7

T S4 T S1 , T S2 , T S3 , T S4 , T S5 , T S6 , T S7

T S5 T S2 , T S3 , T S4 , T S5 , T S6 , T S7

T S6 T S3 , T S4 , T S5 , T S6 , T S7

T S7 T S4 , T S5 , T S6 , T S7


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6 Appendix6.3 Power control Graph


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6 Appendix6.3 Power control Graph


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6 Appendix6.4 QOS indicators logical diagram

▼ UL TBF establishment / traffic


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6 Appendix6.5 OMCR-B7 screen display ( BSS)


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6 Appendix6.5 OMCR-B7 screen display ( BSS)


1.277

6 Appendix6.5 OMCR-B7 screen display ( CELL)


1.278



1.279



1.280



1.281



1.282



1.283



1.284



1.285



1.286

6 Appendix6.6 Allocation/de-allocation of radio resources

▼ Best candidate allocation sorting details:Is there ONE or MORE candidate allocation with:

Nb consec active Non-busy PDCH ≥≥≥≥ n_MS_req?

Is there ONE or MORE candidate allocation with Nb_TS*<MAX_PDCH_HIGH_LOAD? (high load)

or Nb_TS*<MAX_PDCH_DYN? (high load)or Nb_TS*<MAX_PDCH? (normal load)

Is there ONE or MORE candidate allocation with:

Nb consecutive active Non full PDCH ≥≥≥≥ n_MS_req?

No AllocationInitial TBF allocation

MFS SCORING function

YES

YES

YES

NO

NO

NO

Does new candidate allocation

BETTER THAN

current best candidate allocation?

NO

YES

UL request rejected

DL request queued

▼Notes:�MS can only be allocated consecutive PDCHs�Nb_TS*: total number of PDCH allocated to MFS

▼The calculation of the most appropriate number of PDCHs to be allocated is always computed for BOTH directions simultaneously.▼If the number of PDCH currently available is lower than the requested number, this procedure must determine whether or not it is possible to request more TS from the BSC in order to have a new possible candidate allocation.

▼When the allocation can not be served in UL, the TBF allocation is always rejected when it is queued in GSM… this is due to the fact that the mean holding time in GSM is much longer than the average duration of a TBF.▼In UL TBF reject case, the MFS sends a “Immediate assignment reject” message (refer to the TBF establishment failure case in sub-chapter 1.5 “Main transactions”) and the MS must wait for WI_PR seconds before sending a new UL TBF establishment request message.


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6 Appendix6.7 Immediate re-allocation

▼ Trigger T1 :

� soft pre-emption affects the PACCH of a TBF: re-allocation attempt to keep the TBF alive

� the process must start before T_PDCH_PREEMPTION timer expires (even if the re-allocation process spills over)

� only PDCHs that are not marked for soft preemption

� MFS tries to reallocate radio resource offering the same throughput (if possible)

� otherwise, the TBF reallocated will be marked with ‘sub-optimal allocation’ (see trigger T2)

� if the re-allocation process fails, the TBF is dropped

�MFS send a “Packet TBF release” message in polling

▼The MFS keeps 2 list for the T1 trigger:1.list of MSs with uplink bias which are candidates for resource re-allocation,2.list of MSs with downlink bias which are candidates for resource re-allocation,

▼which are served successively.

▼In case of NSE congestion, the MFS triggers a fast preemption on one PDCH in each cell without trying to reallocate radio resources


1.288


▼ Trigger T2 : split into several sub-cases

� T2a: on-going TBF has an optimal allocation

� new TBF allocation in the concurrent direction tagged as the biased direction

� the preferred best candidate allocation for this new TBF implies re-allocation of the on-going TBF

� T2b: on-going TBF does not have an optimal allocation

� new TBF allocation in the concurrent direction

� the preferred best candidate allocation for the new TBF allows a strictly better allocation for the on-going TBF

� T2c: on-going TBF

� new TBF allocation whose only candidate allocation implies on-going TBF re-allocation

� T2d: special case of DL and UL simultaneous TBF re-allocation

▼These re-allocation cases are likely to happen when a UE established a connection with an external server. For the case of email service for instance the downloading and reading of the emails generate DL biased transfers then the reply phase generates UL biased transfers.

▼T2a, T2b, T2c, T2d are trigger conditions that can generate the MFS to request PDCH the BSC. In order to avoid too frequent requests, timers and counters are used (refer to the next slide)

▼T2c case:�the existing TBF can be reallocated with either the same or even a lower number of non full or non busy PDCHs


1.289


▼ Trigger T2 :

� In order to control the number of repetitions of PDCH requests for a same MS in the Trigger T2 cases, a timer was created in MFS:

� t_RADIO_ALLOC_REPETITION initiated at TBF radio resource allocation which must reach T_RADIO_ALLOC_REPETITION second before sending the next request

� when the former timer is on-going, the TBFs is deemed as a ‘sub-optimal’ allocation case

� the ‘sub-optimal’ allocation case is carried on during T_CANDIDATE_TBF_REALLOC seconds


1.290


▼ Trigger E1:� aimed at offering more PDCH despite a temporary PDCH

shortage� shortage due to radio, transmission, UL, or DSP congestion

▼ Trigger E2:� one or more PDCHs is fast preempted but PACCH is not

impacted� throughput is reduced

▼ Trigger E3:� MS multi-slot class acquisition after TBF establishment:

� at completion of the contention resolution on the network side after 1 phase access UL TBF establishment on CCCH (once the MSid is known)

� first reception of MS multi-slot class by BSS in a “Packet Resource Request” or a DL LLC PDU

▼The subsequent re-allocation cases involve MS whose TBF radio resources were impacted by a temporary problem originated by the BSS which can be further corrected.

▼Important : the MFS must maintain for each TBF the information whether it has an optimal radio resource allocation or not.

▼A TBF is deemed as having a sub-optimal allocation if it is granted less PDCHs than the MSs multi-slot class can support in this direction.


1.291


▼ Trigger T3 :

� Aimed at periodically attempting to reallocate the MSs that are candidate to resource re-allocation

� the MFS attempts to reallocate N_MAX_T3_REALLOC candidate MS for each of the following lists:

� MSs with uplink biased transfer which are candidates for resource re-allocation due to trigger T3

� MSs with downlink biased transfer which are candidates for resource re-allocation due to trigger T3

� the candidate time slot allocation must fulfill the following conditions:

� ∃∃∃∃ strictly more PDCHs in the candidate than in the existing in the direction if the bias, AND

� ∃∃∃∃ at least the same number of non-busy PDCHs as in the existing PDCH in the direction of the bias

� refer to SCORING function previously described

▼In this case, it should be possible to request new PDCHs from the BSC

▼N_MAX_T3_REALLOC must encounter successful as well as unsuccessful re-allocations.


1.292

6 Appendix6.8 Immediate re-allocation (execution protocol)

▼ Case1: intra-TRX re-allocation of DL and UL TBFs

� Because re-allocation is on the same TRX:� Frequency parameters are not modified� CS must remain the same� Link adaptation and radio link supervision parameters are

unchanged during the procedure� The following resources can be modified:

TA parameters can change (TA slot and TAI), USFs allocated to the UL TBF, UL and/or DL TFI

MS BSS

Packet time slot reconfigure (PACCH old, polling)

Packet Control Ack

MS switches to the new resources (max. 40 ms)

Packet time slot reconfigure (PACCH old and new)

▼The supervision and link adaptation procedures are stopped during the re-allocation execution▼After sending the assignment request message to the mobile station, the BSS waits for a delay equal to 40 ms plus the actual RRBP delay starting to schedule downlink RLC data blocks and/or USFs on the new resources.▼Upon reception of the Packet time slot reconfigure message, the MS remains on the old resources until it sends the Packet Control Ack (60 to 120 ms including scheduling), then switches onto the new resources.

▼TO avoid complex handling of TBF Normal Release during the re-allocation process, the MFS is not allowed to send the final Packet UL Ack/Nack message or the last DL RLC data block until the re-allocation is successfully completed.


1.293


▼ Cases 2 & 3 : intra-TRX re-allocation of an on-going UL or DL TBF� DL TBF:

� same procedure as previously seen with the sending of a “Packet DL Assignment” message in polling

� no scheduling of USFs

� UL TBF:� same procedure with the sending of a “Packet UL

Assignment” message in polling� no scheduling of DL RLC data blocks� assignment message is sent on the former PACCH/DL

of the uplink TBF if there is no downlink TBF established


1.294


▼ Cases 4 & 5 : intra-TRX re-allocation of UL (DL) TBF upon DL (UL) TBF establishment

� UL TBF = same procedure as case 1, with the following singularities

� there is no old resource for the downlink TBF� the assignment message is sent on the previous

PACCH DL of the UL TBF� a set of PDCHs, a TAI and TFI values are newly

allocated to the downlink TBF

� DL TBF = similar

� there is no old resource for the uplink TBF� a set of PDCHs with their corresponding USFs, a TAI

and TFI values are newly allocated to the uplink TBF

▼This scenario takes place when the MFS needs to reallocate the radio resources of an existing uplink TBF (downlink TBF) to establish a downlink TBF (uplink TBF) upon trigger T2

▼As soon as the intra-TRX re-allocation is possible, it is always preferred to the inter-TRX allocation as in the former some of the new radio resource can be common to the old radio resource:

� the same frequency (or frequencies if TRX used the frequency hopping)� some PDCHs can be the same

▼It must be stressed that a new TFI is allocated which can remind of a New TBF allocation. The MFS will not increment the same counters though.


1.295


▼ Cases 6 : inter-TRX radio resource re-allocation to on-going uplink / downlink TBF

� the same scenarii as the formers apply with the following singularities:

� new frequency parameters are likely to be used on the new radio resources

� the radio link control parameters must be reset� the CS used in UL / DL must be respectively set to its

initial value

� this re-allocation case is only possible if the 2 TRX are mapped on the same DSP (2 TRX of a same cell and same BTS)


1.296

Time allowed:

15 minutes

6 Appendix6.9 Review of PDCH resource management in MFS

� Smooth PDCH allocation practice: for each step of the diagram, determinate if the MFS is in allocation or de-allocation situation?

� INPUTS (step (0)):

– Smooth PDCH adaptation enabled;

– total number of available TS=30;

– MAX_PDCH = 16;

– MAX_PDCH_HIGH_LOAD = 2;

– High_Traffic_Load_GPRS = 80%(i.e. 24 time slots);

– MAX_PDCH_DYN=MAX_PDCH=16

© Alcatel University -8AS 90200 0409 VH ZZA Ed.05Page 1.297

1.297

6 Appendix6.9 Review of PDCH resource management in MFS

▼Smooth PDCH allocation practice▼(0) Smooth PDCH adaptation enabled; total number o f available time slots = 30; MAX_PDCH = 16; MAX_PDC H_HIGH_LOAD = 2; High_Traffic_Load_GPRS = 80% (i.e. 24 time slots); MAX_PDCH_DYN = MAX_PDCH = 16

(1)Av_Traffic_Load_GPRS = 50% (i.e. 15 time slots); C_PDCH = 8; no Load Indication because MAX_PDCH PDCHs can still be supported(2)Av_Traffic_Load = 70% (i.e. 21 time slots); C_PDCH = 8; MAX_PDCH_DYN(BSC) = 11; BSC sends Load Indication(High load; 11) to the MFS; MFS sets MAX_PDCH_DYN to 11(3)Av_Traffic_Load = 90% (i.e. 27 time slots); C_PDCH = 8; MAX_PDCH_DYN(BSC) = 5; BSC sends Load Indication(High load; 5) to the MFS; MFS sets MAX_PDCH_DYN to 5. MFS initiates the pre-emption of 3 PDCHs(4)3 PDCHs pre-empted; C_PDCH = 5 = MAX_PDCH_DYN; AV_Traffic_Load_GPRS = 80%; MAX_PDCH_DYN(BSC) = 5; no Load Indication(5)Av_Traffic_Load = 70% (i.e. 21 time slots); C_PDCH = 5; MAX_PDCH_DYN(BSC) = 8; BSC sends Load Indication(High load; 8) to the MFS; MFS sets MAX_PDCH_DYN to 8(6)Av_Traffic_Load_GPRS = 60% (i.e. 18 time slots); C_PDCH = 7; MAX_PDCH_DYN(BSC) = 13; BSC sends Load Indication(High load; 13) to the MFS; MFS sets MAX_PDCH_DYN to 13(7)Av_Traffic_Load_GPRS = 70% (i.e. 21 time slots); C_PDCH = 13; MAX_PDCH_DYN(BSC) = 16 = MAX_PDCH; BSC sends Load Indication(Normal load; 16) to the MFS; MFS sets MAX_PDCH_DYN to 16


1.298

6 Appendix6.10 Training exercises solutions

▼ UL PDTCH and PACCH multiplexing on SPDCH:

UL transfer? DL transfer?Downlink UplinkBlock number

TFI USF RRBP

Block n

Block n+1

Block n+2

Block n+3

Block n+4

Block n+5

Block n+6

TFI a USF j

TFI b USF k

TFI a USF j + 3

TFI b USF k

TFI b 000

TFI b USF j

TFI a USF k

false

false

false

false

false

false

PDTCH / PACCH a

PDTCH / PACCH b

PDTCH / PACCH a

PDTCH / PACCH b

PDTCH / PACCH b

PDTCH / PACCH a

PDTCH / PACCH b

RLC header MAC header Block Content?

?

PDTCH / PACCHj

PDTCH / PACCHk

PDTCH / PACCHj

PDTCH / PACCHk

PDTCH / PACCHj

PACCHa

PDTCH / PACCHk

▼USF = No emission = 000


1.299

▼ DL multi-frame: secondary MPDCH � BS_PBCCH_BLKS=2� BS_PAG_BLKS_RES=6

▼ UL multi-frame:� BS_PRACH_BLKS=4

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11

?????

?????

?????

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11

?????

?????

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11

PAGCH, PDTCH, PACCH

PAGCH

PPCH, PAGCH

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11

PRACH




1.300


T_3

192n


1.301


MS BTS BSC MFS SGSN

PDP PDU

MS inStandby

PS Paging

PCH

Packet paging request

RACH

Packet channel requestcause = paging response

AGCH or PCH


MS Ready

DL UNITDATA PDU

USF Scheduling

PDTCH

PDTCH

Sending of a LLC PDU

UL TBF establishment

DL TBF establishment

P53a


1.302


▼ Case (A):

▼ Case (B):

2HIGHHIGH

16INDEFINITEINDEFINITE

16LOWLOW



16INDEFINITE


AV_TRAFFIC_LOAD <


2HIGHHIGH

2HIGH


AV_TRAFFIC_LOAD >


16INDEFINTELOW




1.303

Time allowed:

10 minutes


� Example with EN_DYN_PDCH_ADAPTATION = Enable

� Inputs:







SOLUTION:

Case (A):

MAX_PDCH_DYN=11

Case (B):

MAX_PDCH_DYN=5

AV_Traffic_load > HIGH_TRAFFIC_LOAD

de-allocation from Nb_PDCH=8 to MAX_PDCH_DYN=5


1.304


DL transfer;CS2 MS2>

DL transfer;CS2 MS1 >

+1CS +3CS +1CS -1CS -2CS -1CS -1CS

CS TS allocated 0 0 1 1 4 4 5 5 4 4 2 2 1 1 0 0

PS TS allocated 3 3 3 3 6 2 2 2 2 2 2 2 2 2 2 6

AV _TRAFFIC_L OAD_GPR S (%) 21,4 21,4 28,6 28,6 71,4 42,9 50 50 42,9 42,9 28,6 28,6 21,4 21,4 14,3 42,9

Max Nb of PS TS available (Dynamic PDCH adaptation=Disable) 8 8 8 8 2 2 2 2 2 2 2 2 2 2 8 8

max throughput per MS on air interface 38,4 38,4 12,8 12,8 12,8 12,8 12,8 38,4

CS TS allocated 0 0 1 1 4 4 5 5 4 4 2 2 1 1 0 0

PS TS allocated 3 3 3 3 6 5 5 4 4 5 5 6 6 6 6 6

AV _TRAFFIC_L OAD_GPR S (%) 21,4 21,4 28,6 28,6 71,4 64,3 71,4 64,3 57,1 64,3 50 57,1 50 50 42,9 42,9

Max Nb of PS TS available (Dynamic PDCH adaptation=Enable) 8 8 8 8 5 5 4 4 5 5 7 7 8 8 8 8max throughput per MS on air interface 38,4 38,4 32 25,6 32 38,4 38,4 38,4


1.305


DL

UL

Master 1

1 1 1Master

2

2 2 2

34 5

6

4 4 4 3

3

3

7

8 9

5 55

6

6

68

8

8

9

9

9

7

7

710

10

11

11

10 11

▼PDCH 0 will be reserved form Master PDCH (as no PDTCH can be multiplexed on MPDCH in B7.2)▼DL bias is assumed in all the exercise, UL TBF is established and the DL immediately after▼Multislot class of the MS is known, so MFS will try to allocate PDCH to maximize DL (bias) and then UL (concurrent) throughputs

▼TBF 1: All choices (from (1,2,3) to (5,6,7)) are equivalent for DL TBF position in term of busy / full PDCH and throughput, so the more left index is chosen (last step of scoring function): DL=1,2,3 and UL=2▼Then Master PDCH is dynamically allocated on PDCH0▼TBF 2: positions (4,5,6) and (5,6,7) are equivalent in term of non-busy/non-full PDCH in the direction of the bias and the opposite. More left is chosen, so DL=4,5,6 and UL=5▼TBF 3: only (5,6,7) offers 1 non-busy PDCH in the direction of the biased, so DL=5,6,7 and UL = 6▼TBF 4: all PDCH are busy in DL, none is full. In UL 3 and 4 are empty and thus preferred (1 or 7 are not to be considered at this step as they lead to DL=(1,2) or (6,7) where only 2 PDCH are assigned when 3 are possible) (this leads to possible DL=2,3,4 or 3,4,5 . Scoring function is used to choose the allocation: choice is done to preserve the best throughput in DL and then UL: (2,3,4) is used by less TBF in DL, so best throughput.▼TBF 5: all PDCH busy in DL. In UL, PDCH 4 is empty and thus preferred (1 & 7 are not good candidates due to previous explanation). So DL=(3,4,5) and UL=4▼TBF 6: all PDCH are busy in DL and all UL PDCH leading to 3 PDCH DL allocation are also busy. Best throughput is reached in DL with (1,2,3) or (5,6,7). Both cases lead to same UL throughput. So more left is chosen: DL=1,2,3 and UL = 2▼TBF 7: (5,6,7) offers the best throughput in DL. So DL=5,6,7 and UL = 6▼TBF 8: Best DL throughput is delivered by (1,2,3) or (5,6,7). Similar throughput in UL. More left is chosen. DL= 1,2,3 and UL=2▼TBF 9: (5,6,7) offers the best throughput in DL. So DL=5,6,7 and UL = 6▼TBF 10: PDCH 3 and 5 are full. By the way, it is no more possible to allocate 3 consecutive PDCH in DL. (1,2) and (6,7) offer 2 non-full PDCH. More left is chosen. So DL=(1,2) and UL = 1 (1 is empty in UL)▼TBF 11: only (6,7) offers 2 non-full PDCH in DL so DL=6,7 and UL = 7 (empty in UL)


1.306


▼ Objective: Fill up the new TBF allocation after re-allocation

DL

UL

Master 8

8 4 4Master 4 5

4 5

8 5 5

8

11

10

10

11

10

10

1111

▼ TBF DL 10 will be granted TS5, 6, 7 since criterion F3 does not apply (no non-busy time slot in the DL direction) and then, the criterion F4 will select that combination (lowest load in the DL direction).

▼ TBF DL 11 will be granted TS4, 5, 6 thanks to criterion C (only allocation offering one non-busy time slot in the UL direction).


1.307

Time allowed:

5 minutes


▼ Master Channel is used

� MS (2W, class B) ; C1(serving) is just becoming negative

�Objective: Find cell selected by the MS

cell C31 C32 GPRS_PRIORITY_CLASS

A 3 10 2 2/ low prio

B -6 12 1 1/ C31<0

C 4 13 1 best C32

D -1 14 1 1/ C31<0

E 2 16 2 2/ low prio

F 10 12 1


1.308


▼ Find the cell selected by MS

CI=6169GSM900

CI=1823

GSM900

CI=1964 GSM900

CI=6270

GSM900

CI=6271GSM900 Cell 3 (8557, 1823)

Cell 2 (8564,6169)

Cell 1 (8564, 1964)

5

4

3

2

1

Measurements

-77-85-89

-82-87-88

-87-90-88

-100-90-84

-104-96-80

RxLev (3)RxLev (2)RxLev (1)

▼Cell 1 is first selected as it has the best C1.▼Note: Cell 3 cannot be selected as C1 < 0

▼At step 4, cell 2 cannot be reselected (as it would be in GSM idle mode) as CRH is to be taken into account in GPRS transfer mode…

▼At step 5, RA/ LA update is triggered


1.309

Time allowed:

20 minutes


▼ Scenario 2: Master Channel is used

� Multilayer network is considered: umbrella layers + microcells

� 1. Find parameter settings allowing “GSM like” behaviour: capture towards microcellfor slow mobiles

� 2. If GPRS traffic is to be handled by macrocells, find parameter settings avoiding selection of micro

▼1. In the first case, we want a “GSM like” behaviour, i.e. capture towards microcell for slow mobiles�use C31 & C32 specific algorithms as Master channel is available

▼The idea is the following: if the MS is slow, make sure that C31 of micros is > 0 and C31 (macros) is < 0.With high GPRS_PRIORITY_CLASS, and low priority class to macros, the MS will reselect the best C32 amongst the C31 > 0, that means amongst the microsIf there is no cell with C31 > 0, best C32 is selected▼MS is camping on macro

�C31 (serving macro) = RLA_P(serving macro) - HCS_THR (serving macro)�C31 (neigh micro) = RLA_P(neigh micro) - HCS_THR (neigh micro) - TO(L)�C31 (neigh macro) = RLA_P(neigh macro) - HCS_THR (neigh macro)

▼TO(L) is in C31 equation of micro as GPRS_PRIORITY_CLASS are different. This enables to reselect only slow MS, by tuning GPRS_PENALTY_TIME (40s) and GPRS_RESELECT_OFFSET (40 dB)▼define HCS_THR (micro) = -85 dBm (not too low to avoid reselecting bad cells, and to say: micro is good when its level is > -85 dBm)▼define HCS_THR (macro) = -60 dBm (macro is good when its level is > -60 dBm)▼For example: RLA_P (micro) = RLA_P (macro) = -80 dBm

�C31 (serving macro) = -80 +60 = -20�C31 (neigh micro) = -80 + 85 - 40 = -35 before GPRS_PENALTY_TIME_EXPIRY and = +5 after

▼even if there are several macros with C31 > 0, MS will reselect microcell, since GPRS_PRIORITY_CLASS is higher▼GPRS_RESELECT_OFFSET has to be boosted on microcell to favour C32 of micro compared to macro one to avoid blocking reselection

�C32 (serving macro) = C1(serving macro)�C32 (neigh micro) = C1(neigh micro) + GRO

▼When level of micro is low (C1 < 0, to be tuned with GPRS_RXLEV_ACCESS_MIN), reselection will be triggered to cell with best C32 (another micro or macro)

▼2. To favour macro: tune HCS_THR (lower on macros, ex: -97 dBm and high value on micros: -48 dBm) and GPRS_PRIORITY_CLASS


1.310

Time allowed:

10 minutes


▼ CS adaptation / DL measurements

� Network parameters:

� TBF_DL_INIT_CS = CS1�CS_QUAL_DL_1_2_X_Y = 2�CS_HST_DL_LT = 2�CS_HST_DL_ST = 4

� Objective: Find CS used in DL


1.311


▼ Find which CS is used at each measurement

Measurement 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

RXQUAL_DL 0 0 2 3 4 5 5 5 6 0 0 0 0 6 7 7

AV_RXQUAL_DL_LT 0,0 0,0 1,1 1,9 2,6 3,3 3,8 4,1 4,5 3,5 2,7 2,1 1,7 2,6 3,5 4,2

AV_RXQUAL_DL_ST 0,0 0,0 1,7 2,7 3,8 4,8 5,0 5,0 5,8 1,2 0,2 0,0 0,0 4,8 6,6 6,9

CS ? CS1 CS2 CS2 CS2 CS2 CS2 CS2 CS1 CS1 CS1 CS1 CS1 CS2 CS2 CS1 CS1

if enough packets LT pb ST pb

▼Short term average is calculated with AlphaST = 0.2▼Short term average is calculated with AlphaLT = 0.8


1.312


▼ List in DL and UL the different cases of abnormal release

� DL

�No acknowledge received� Too low TX_efficiency

� UL

�No data received�UL window stalled� Too low TX_efficiency� Final acknowledge not

receivedTime allowed:

10 minutes

Abnormal releases

followed by UL TBF re-

establishment



7. GLOSSARY


1.314

Glossary of abbreviations used A to L

▼ APN: Access Point Name

▼ BG: Border Gateway

▼ BSC: Base Station Controler

▼ BSS: Base Station Subsystem

▼ BSCGP: BSC-Gprs Protocol

▼ BSSGP: BSS-Gprs Protocol

▼ BVCI: Bssgp Virtual Connection Identifier

▼ CDR: Call Detail Record

▼ CG: Charging Gateway

▼ CS: Circuit Switching

▼ DHCP: Dynamic Host Configuration Protocol

▼ DL: Down Link

▼ DLCI= Data Link Connection Identifier

▼ DNS: Domain Name System

▼ FR: Frame Relay

▼ GPRS: General Packet Radio Service

▼ GGSN: Gateway GSN

▼ GMM: Gprs Mobility Management

▼ GR: Gprs Register interface

▼ GSL: Gprs Signaling Link

▼ GSM: Global System for Mobile communication

▼ GSN: Gprs Support Node

▼ GSS: Gprs Sub-System

▼ GTP: Gprs Tunneling Protocol

▼ HLR: Home Location Register

▼ IMSI: International Mobile Subscriber Identity

▼ IP: Internet Protocol

▼ ISDN: Integrated Service Digital Network

▼ LLC: Logical Link Control


1.315

Glossary of abbreviations used M to R

▼ MAC: Medium Access Control

▼ MFS: Multi-Bsc Fast packet Server

▼ MS: Mobile Station

▼ MSC: Mobile Switching Center

▼ MT: Mobile Terminal

▼ NE: Network Element

▼ NRPA: Network Requested PDP Context Activation

▼ NSAPI: Network Service Access Point Identifier

▼ NSC: Network Service Control layer

▼ NSEI: Network Service Entity Identifier

▼ NSS: Network Sub-System

▼ NS-VC: Network Service- Virtual Circuit

▼ NTP: Network Time Protocol

▼ OMC: Operation & Maintenance Center

▼ OS: Operation System

▼ PAGCH: Packet- Access Grant Channel

▼ PCCCH: Packet- Common Control CHannel

▼ PCO: Protocol Configuration Options

▼ PCU: Packet Control Unit

▼ PDCH: Packet Data CHannel

▼ PDN: Packet Data Network

▼ PDP: Packet Data Protocol (IP or X25)

▼ PDU: Protocol Data Unit

▼ PPCH: Packet- Paging CHannel

▼ PRACH: Packet- Random Access CHannel

▼ PS: Packet Switching

▼ P-TMSI: Packet- Temporary Mobile Subscriber Identity

▼ PVC: Permanent Virtual Circuit

▼ P-VLR: Packet- Visitors Location Register

▼ QoS: Quality of Service

▼ RA: Routing Area

▼ RLC: Radio Link Control


1.316

Glossary of abbreviations used R to Z

▼ RRM: Radio Resource Management

▼ SGSN: Serving GSN

▼ SM: Session Management | Short Message

▼ SMS: Short Message Service

▼ SMS-C: SMS-Center

▼ SNDCP: Sub Network-Dependent Convergence Protocol

▼ SNMP: Simple Network Management Protocol

▼ SNS: Sub-Network Service layer

▼ TBF: Temporary Block Flow

▼ TC: Trans Coder

▼ TCH: Traffic CHannel

▼ TCP: Transmission Control Protocol

▼ TDMA: Time-Division Multiplexing Access

▼ TFI: Temporary block Flow Identifier

▼ TID: Tunnel IDentity

▼ TLLI: Temporary Logical Link Identity

▼ TS: Time Slot

▼ UDP: User Datagram protocol

▼ UL: Up Link

▼ UMTS: Universal Mobile Transmission System

▼ WAN: Wide Area Network

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