Evolium Base Station Subsystem Introduction to Gprs/Egprs

8/14/2019 Evolium Base Station Subsystem Introduction to Gprs/Egprs

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Alcatel University 3FL10472ACAAWBZZA Ed.02 Page 1

EVOLIUM Base Station SubsystemINTRODUCTION TO GPRS/EGPRS

All rights reserved. Passing on and copying of this document,use and communication of its contents not permitted without

written authorization from Alcatel.

TRAINING MANUAL

3FL10472ACAAWBZZA2 MARCH 2006


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2Introduction to GPRS/EGPRS

All rights reserved 2004, Alcatel

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Safety WarningBoth lethal and dangerous voltages are present within the equipment. Do not wear conductive jewellerywhile working on the equipment. Always observe all safety precautions and do not work on theequipment alone.

CautionThe equipment used during this course is electrostatic sensitive. Please observe correct anti-staticprecautions.

Trade MarksAlcatel and MainStreet are trademarks of Alcatel.All other trademarks, service marks and logos (Marks) are the property of their respective holdersincluding Alcatel. Users are not permitted to use these Marks without the prior consent of Alcatel or suchthird party owning the Mark. The absence of a Mark identifier is not a representation that a particularproduct or service name is not a Mark.

CopyrightThis document contains information that is proprietary to Alcatel and may be used for training purposesonly. No other use or transmission of all or any part of this document is permitted without Alcatelswritten permission, and must include all copyright and other proprietary notices. No other use ortransmission of all or any part of its contents may be used, copied, disclosed or conveyed to any party inany manner whatsoever without prior written permission from Alcatel.

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1 What is GPRS ? 6

1.1 Definition 8

1.2 General architecture 9

1.3 MS Class 10

1.4 MS Multislot Class 11

1.5 GPRS Main Concepts 12

1.6 The benefits of GPRS 17

1.7 EGPRS 18

1.8 Quality of service profile 19

1.9 Services 20

2 GPRS Operation 23

2.1 Main Entities 25

2.2 MS Mobility Management States 30

2.3 MS Radio Resource Operating Modes 31

2.4 Basic procedures 32

2.5 Charging 45

2.6 Security 47

3 The Base Station Subsystem 52

3.1 3GPP Position 54

3.2 Alcatels Choice 55

3.3 Layered Model 56

3.4 Gb Interface 58

3.5 Radio Interface 60

4 Alcatel Solution 71

4.1 GPRS Network Overview 73

4.2 Alcatel 9135 MFS 74

4.3 Packet Switched Core Network 80

4.4 GPRS Network Management 82

4.5 Alcatel QoS offer 83

5 Annex and Glossary 88

Contents


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Self assessment of the objectives Contract number :

Course title :

Client (Company, centre) :

Language : English dates from : to :

Number of trainees : Location :

Surname, First name :

Did you meet the following objectives ?

Tick the corresponding box

Please, return this sheet to the trainer at the end of the training

Instructional objectivesYes (orGlobally

yes)

No (orglobally

no)Comments

1 To be able toidentify the benefits of GPRS

2 To be able todescribe the organization of aGPRS network,architecture, interfaces andprotocols.

3 To be able todescribe the main data

interchange mechanisms on a GPRSnetwork

4 To be able tocharacterize the solutionoffered by Alcatel

Other comments


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Instructional objectivesYes (orGlobally

yes)

No (orglobally

no)Comments

Self assessment of the objectives (continued)

Thank you for your answers to this questionnaire

Other comments


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1 What is GPRS ?Session presentation

> Objective: to be able to identify the technicaland commercial benefit of GPRS.

> Program: 1.1 Definition

1.2 General architecture

1.3 MS Class

1.4 MS Multislot Class

1.5 GPRS Main Concepts

1.6 GPRS Benefits

1.7 EGPRS 1.8 Quality of Service profile

1.9 Services


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1 What is GPRS ?1.1 Definition

> Definition (3GPP TS 22.060)

GPRS provides data transfer capabilities between a sending entity andone or more receiving entities.

These entities may be an MS or a Terminal Equipment, the latter beingattached either to a GPRS network or to an external data network.

The base station provides radio channel access for MSs to the GPRSnetwork.

w PDN (Packet Data Network)

IP networks = Internet (connectionless)


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1 What is GPRS ?1.2 General architecture

GPRSCore Network

IP

Gb

NSSA PSTN

Gi

PDNIP / PPP

RADIOACCESS

NETWORK

BSS

Packetswitching

circuitswitching

w GPRS Core Network

The GPRS Core Network is also called GSS (GPRS Sub-System). It is an IP network, and therefore contains routers

(machines handling the packet switching function.)

w Routing Function

Data transmission between GPRS Support Node (GSN), may occur across external data networks that provide their owninternal routing functions, for example X.25 [34], Frame Relay or ATM networks.

w IP interworking

The GPRS Core Network supports interworking with networks based on the Internet protocol (IP). The GPRS CoreNetwork may provide compression of the TCP/IP header when an IP datagram is used within the context of a TCPconnection.

w X.25

X.25 PDP Type have been removed from the standard since R99.


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1 What is GPRS ?1.3 MS Class

> Class A

Operates GPRS and other GSM services simultaneously.

> Class B

Monitors control channels for GSM GPRS and other GSM servicessimultaneously,

but can only operate one set of services at one time.

> Class C

Exclusively operates GPRS services.

w Classes A and B

Require dual scanning by the mobile for both GSM and GPRS service requests. Class A or B mobiles are "attached"

simultaneously to both networks.w Class B

The exchange of packets is suspended to answer to an incoming GSM call (the GPRS subscriber is considered to be inthe "busy" or on hold" state).

The PDP contexts are still active on the SGSN side until the Purge_Timer elapses.

w Class C

Exclusively operates GPRS services.


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1 What is GPRS ?1.4 MS multislot class

NAxx119 to 29like 10

000NA88218011NA77217

121NA66216131NA55215131NA44214131NA33213121544112121534111121524110121523191215141813143317131423161314221513141314 13232213

1323121224221111

TrbTraTtbSumTxRxTypeMulti-slot

class

w 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 timew Rx

Maximum number of received timeslots that the MS can use per TDMA frame. The receive TS shall be allocatedwithin window of size Rx, but they need not be contiguous. For SIMPLEX MS, no transmit TS shall occur betweenreceive TS within a TDMA frame. This does not take into account measurement window (Mx).

w Tx

Maximum number of transmitted timeslots that the MS can use per TDMA frame. The transmit TS shall beallocated within window of size Tx, but they need not be contiguous. For SIMPLEX MS, no receive TS shall occurbetween transmit TS within a TDMA frame.

w SUM

Maximum number of transmit and receive timeslot (without Mx) per TDMA frame

w Meaning of Ttb, Tra et Trb changes regarding MS types.

For SIMPLEX MS (type 1):

Ttb Minimum time (in timeslot) 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 toopen 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 toopen a measurement window

Trb same as Tra without opening a measurement window


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PDNPDNPDNPDN

PSPSPSPS

GSMGSMGSMGSM

networknetworknetworknetwork

CSCSCSCS

1 What is GPRS ?1.5 GPRS Main Concepts (1/5)

> Use of radio resources in case of circuit switching

Fixed Rate

Radio timeslot

Radio interface

Access nodeAccess nodeAccess nodeAccess node

CS PS

w Drawbacks of CS for data services

one radio channel at 9.6 kbit/s per user

fixed bit rate => waste (in the case of discontinuous service) and limitation on bit rate


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GPRSGPRSGPRSGPRS

networknetworknetworknetwork

PSPSPSPS

PDNPDNPDNPDN

PSPSPSPS


> Use of radio resources in case of packet switching

Radio timeslot

Radio interface

Variable Rate

w Benefits of Packet Switching

Variable bit rate becomes possible

One MS uses several RTSs. The maximum number of RTSs is given by the Operator (O&M parameters) and MScapabilities (MS multislot class)

One RTS is shared by several MSs. The maximum number of MSs per RTS is given by the Operator (O&Mparameters) and 3GPP specifications (limitation due to addressing availability)


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> Radio resource assigned according to requirement

Radio resource shared between users

Various radio channel coding schemes are specified to allow bit ratesfrom 9 to more than 150 kb/s per user (according also to the quality ofradio transmission and the modulation used)

High bit rates if several channels are assigned to one MS

Low bit rates if one channel is shared by several MSs.

> Optimized use of the radio resource

Use of the radio resources only when data is transferred Uplink and downlink resources reserved separately

w Radio resource sharing

The radio resources are shared by statistical multiplexing. As in GSM, no subscriber has their own permanent radio

resource.

w Bit rate

Maximum instantaneous bit rate provides 171,2 kb/s by the allocation of eight RTSs to one subscriber. The statedmaximum bit rates are different, because different coding schemes are used, which impacts the bit rate over a RTS. (seeAnnex)

w Up link (UL) and downlink (DL)

It is possible to use a different bit rates in each transmission direction, whereas in CS (Circuit Switching) mode, there is amaximum limit of 9.6 kb/s, in both directions and at all times.


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> Dynamic allocation and sharing of radio resources

User 1

User 2

User 3

User 4

User 5

1 RESOURCE SHARED BY X USERS (PDCH)

User 1

USER1 USES 3 RESOURCES (3 PDCH)

1 RESOURCE USED BY ONE USER NOT SHARED TCH

User 1

Number of resources according to the capability of the MS

w Caution: Animated slide that does not make sense if not in the slide-show mode.

w Optimized useA radio resource (set of Radio Blocks over one or several RTS) is allocated only when data is being transferred, byestablishing and releasing Temporary Block Flow (TBF), that can be presented as micro-connections, each time a datatransfer has to be sent over the radio interface.

w Radio resource sharing

One TS can be shared by several MSs, by dynamic time multiplexing under control of the BSS.


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> Variable useful transmission rate per Radio resource

Maximum security

Channel Transmission rateabout 22 k with GMSKabout 60k with 8PSK (Edge)

minimum throughput

Minimum security

Maximum throughput

When the radio transmission has a good quality the security can be reduced inorder to increase the useful transmission rate



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1 What is GPRS ?1.6 The benefits of GPRS

> GPRS benefits

BSS hardware (included OMC-R) is re-used from GSM

Smooth GPRS introduction Higher data throughput thanks to EGPRS (EDGE)

Data transfers can billed by volume instead of time

An MS can exchange data by GPRS in parallel with a conventional GSMcall (if MS Class A)

w BSS is re-used

The same Radio Access Network is re-used, and a Packet Control Unit (PCU) function is implemented in the BSS.

w Compared to the GSM BSS

same frequency bands

same TDMA frame structure

same burst structure

same frequency hopping laws

...


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1 What is GPRS ?1.7 EGPRS

> EGPRS is an enhancement of GPRS

allows higher bit rates on the radio interface

achieved by using a new modulation (8-PSK)

and new coding schemes (MCS-1 to MCS-9) in the MS and the BSS.

> The same set of services provided by GPRS is available in EGPRS.

w Shared = in other words: "the radio resources are shared by statistical multiplexing". As in GSM, no subscriber has theirown permanent radio resource.

wHigh or low bit rates = more than one time slot per MS or conversely, more than MS on the same TS (one TDMA frameoccupies 4.615 ms and is divided into 8 TS or channels).

w Maximum instantaneous bit rate provided = 171,2 kbps through the allocation of eight TSs to one subscriber. The statedmaximum bit rates are different (according to the BSS release), because different ways of encoding the data, or "codingschemes", are used, which impacts the bit rate over a TS. (cf Annex)

w Optimized use:refer to Radio resource allocation in the slides to come + radio resource management in the BSSChapter.The radio resource allocation is suitable for variable, bursty traffic (downloading Web pages).

w Up link (UL) and downlink (DL): It is possible to use a different bandwidth (bit rate) in each transmission direction, whereasin CS (circuit switching) mode, there is a maximum limit of 9,6 kbps, in both directions and at all times.

w QoS: Henceforth, QoS parameters are part of subscription data, according to the wide range of services provided to a

subscriber.


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Precedence Classrelative importance of service under congestion3 classes

Delay Classtotal delay measured between R or S point and Gi4 classes

Reliability Classacknowledgement of packets5 classes

Peak throughput Class

Mean throughput Class

the maximum data rate allowed to the user

maximum data rate during a period

Throughput class19 classes

9 classes

1 What is GPRS ?1.8 Quality of service profile

w Precedence class

According to the class, user data packet can be discarded during the transfer due to a congestion state.

3 classes are defined : any, normal, high

w Delay class

The delay class depends on the operator network because a measurement is done between the R or S interface (betweenthe Mobile Terminal and the Terminal Equipment) and the Gi interface. For each operator, delay values are different sodelay classes are a reference not a strict value.

4 classes are defined : best effort, 1, 2, 3

w Reliability class

The reliability means that user data packets are acknwoledged during the transfer. The reliability classes are definedaccording to the acknowledgement or not of the packet.

5 classes are defined

w Throughput class

The throughput class is defined by the 2 following parameters:

Mean Throughput : 9 classes are defined (from best effort to 111 Kb/s)

Peak Throughput : 19 classes are defined (from 8 Kb/s to 2048 Kb/s)


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1 What is GPRS ?1.9 Services

Always-on

Mobile OfficeMobile OfficeMobile OfficeMobile OfficeVoice (!)E-mailAgendaIntraNet/InterNetCorporate ApplicationsDatabase Access

Vertical applicationVertical applicationVertical applicationVertical applicationTraffic ManagementAutomationMobile branches

Health

Location servicesLocation servicesLocation servicesLocation servicesTraffic Conditions ItinerariesNearest Restaurant,

Cinema, Chemist,Parking;, ATM ...

FunFunFunFunGames (Hangman, Poker, )Screen SaverRing Tone

HoroscopeBiorhythm

Media

TransportationTransportationTransportationTransportationFlight/train Schedule reservation

MusicMusicMusicMusicDownloading of

music files orvideo clips

NewsNewsNewsNews(general/specific)(general/specific)(general/specific)(general/specific) International/National NewsLocal NewsSport NewsWeatherLottery ResultsFinance News

DirectoriesDirectoriesDirectoriesDirectoriesYellow/White Pages International Directories

Operator Services

M-commercePhysicalPhysicalPhysicalPhysicalon-line shoppingon-line food

Non physicalNon physicalNon physicalNon physicalon-line BankingTicketingAuctionGambling.

w Retrieval services

Provide the capability of accessing information stored in data base centers. The information is sent to the user on demand

only. An example of one such service in the Internet's World Wide Web (WWW).w Messaging services

Offer user-to-user communication between individual users via storage units with store-and-forward mailbox, and/ormessage handling (e.g., information editing, processing and conversion) functions;

w Conversational services

Provide bi-directional communication by means of real-time (no store-and-forward) end-to-end information transfer fromuser to user. An example of such a service is the Internet's Telnet application;

w Tele-action services

Characterized by low data-volume (short) transactions, for example credit card validations, lottery transactions, utility meterreadings and electronic monitoring and surveillance systems.

w Distribution services

Characterized by the unidirectional flow of information from a given point in the network to other (multiple) locations.

Examples may include news, weather and traffic reports, as well as product or service advertisements;

w Dispatching services

Characterized by the bi-directional flow of information from a given point in the network (dispatcher) and other (multiple)users. Examples include taxi and public utility fleet services;

w Conferencing services

Provide multi-directional communication by means of real-time (no store-and-forward) information transfer betweenmultiple users.


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True or False ?

GPRS is a circuit switching technology

The GSS is an IP network Data transfers are often conducted at variable bit rates

With a class B mobile, a web page can be downloaded while speaking

Billing by volume allows subscribers to be permanently on line

Several channels can be assigned to a MS

One channel is shared by several MSs

EGPRS is GPRS with better Throughput

The useful transmission rate depends on the radio quality

Time allowed :

5 minutes

1 What is GPRS ?Exercise


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Thank you for answeringthe self-assessmentof the objectives sheet

1 What is GPRS ?Evaluation

> Objective : to be able to identify thetechnical and commercial benefit of GPRS


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2 GPRS Operation


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2 GPRS OperationSession presentation

> Objective: to be able to describe the organization of aGPRS network architecture, interfaces and protocols.

> Program: 2.1 Main Entities

2.2 MS Mobility Management States

2.3 MS Radio Resource Operating Modes

2.4 Basic Procedures

2.5 Charging

2.6 Security


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2 GPRS Operation2.1 Main Entities

> Overview

CELLS

BTS BSC

BSS RADIO ACCESS NSS CALL PROCESSING

circuits

To PSTN

GPRS

N7

AUC EIR

HLR

IP

SGSN

SGSN

NTP DNS

DHCP

To IP Networks

GGSN

BG To other operatorIP Networks

PCU includedin BSS

MSCVLR

w PCU functions

LLC PDU segmentation / re-assembly into RLC/MAC PDU

PDCH scheduling (resource multiplexing) Channel access control (access requests and grants)

ARQ function (RLC block Ack / Nak, buffering and retransmission of RLC blocks)

Radio channel management (power control, congestion control, broadcast control information).

w DNS (Domain Name Server) and DHCP (Dynamic Host Convergence Protocol)

w NTP server (Network Time Protocol) for GSN synchronization. In general an NTP application does not run on adedicated server. The OMC-G can play this role.

w HLR (Home Location Register) is involved in MS attachment to the GPRS network (authentication + services subscribed

to)


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GSS


> SGSN and GGSN

IPbackbone

GGSN1

IPnetwork 1

IPnetwork 1

GGSN2

IPnetwork 1

GGSN3

IPnetwork 1

IPnetwork 1

SGSN1

SGSN2

SGSN5

SGSN3

SGSN4

w The SGSN (Serving GPRS Support Node) stores subscriber data:

Subscription information

IMSI one or more temporary identities (P-TMSI)

zero or more PDP addresses

Location information

the cell or the RA where the MS is registered

the VLR number of the associated VLR (if the Gs interface is implemented)

the GGSN address of each GGSN for which an active PDP context exists

It also manages:

the transfer and routing of user data packets from the GSS towards the BSS

the mobility (GPRS attach/detach, data retrieval from the HLR, RA / Cell update)

the authentication and encryption (Access control and security)

the sessions (PDP context activation/deactivation)

The transfer of charging data.

w The GGSN (Gateway GPRS Support Node) stores subscriber data received from the HLR and the SGSN:

Subscription information

IMSI

zero or more PDP addresses

Location information

the SGSN address of the SGSN where the MS is registered

It also manages:

the allocation and use of dynamic @IP for MS,

the tunneling and encryption of user data at Gi interface,

the transfer of user data packets,

the charging data.


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> Servers

GPRSBACKBONE

SGSN GGSN

NTP

DNS DHCPIP add256.167.123.34

Alcatel.fr

w DNS

Resolve a name into an IP address

Use in Mobility procedure

w DHCP

Provide dynamically IP addresses

Split Users into pool of IP addresses

w NTP

Provide one time reference for all the network

Have a very precise time reference

Synchronization from satellite


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MS

SGSNBSS VPLMN

BG

VISITED PLMN

GGSN


> Border gateway

INTER PLMNNETWORK

HPLMN GGSN PDNBG

HOME PLMN

w Border Gateway functions

Inter-PLMN routing and forwarding of user packets (IP router)

Security functions (firewall, access-list filtering)

w Connection of two Border Gateways

Via a private or public IP network, through the Gp interface.

w Choice of GGSN

If a subscriber wants to access an Intranet (PDN) in his home country, from the visited PLMN, the selected GGSN is theone from the home PLMN

For Internet access a GGSN in the visited country could be used.


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A


Gn

Signaling + data

Signaling

MobileGPRS

Gd

Um

GPRS network

Gb

BSS

Gc

GsGr

Gi

PDN

SGSN

SGSN GGSN

HLRMSCSMS-GMSC

> Interfaces

w Signaling protocols

MAP/TCAP/SCCP/MTP on Gr, Gd and Gc,

GTP/UDP/IP on Gn, BSSAP+/SCCP/MTP on Gs,

GMM/SM/LLC on Gb/Um.

w Gc interface

Used for network-requested PDP contexts activation (GGSN asks the HLR for SGSN routing information).

w Gs interface

Defines the Network Mode of Operation I (NMOI). It allows to perform LA + RA combined Location Update, and PS andCS paging coordination (refer to ANNEX).

w Gr interface

Exchange of subscription information at GPRS attachment phase

w Additional interfaces

Gf (to the EIR)

Gd to deliver the SMS to the mobiles via the GPRS network (SGSN option and subscriber feature)


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2 GPRS Operation2.2 MS Mobility Management States

Idle

Ready

Stand-by

> MS MM states

GPRS Detach

PDU transmission

READYtimer expiry

GPRS Attach

Location atCELL level Location at

RA level

Autonomous cell reselection NCO

Or controled by network NC 2( In paquet transfert mode )

Autonomous cell reselection

w IDLE (GPRS) State

In GPRS IDLE state, the subscriber is not attached to GPRS mobility management. The MS and SGSN contexts hold no

valid location or routeing information for the subscriber. The subscriber-related mobility management procedures are notperformed.

Data transmission to and from the mobile subscriber and the paging of the subscriber is not possible. The GPRS MS isseen as not reachable in this case.

In order to establish MM contexts in the MS and the SGSN, the MS shall perform the GPRS Attach procedure.

w STANDBY State

In STANDBY state, the subscriber is attached to GPRS mobility management. Pages for data or signalling informationtransfers may be received. It is also possible to receive pages for the CS services via the SGSN. Data reception andtransmission are not possible in this state.

The MS performs GPRS Routeing Area (RA) and GPRS cell selection and re-selection locally. The MS executes mobilitymanagement procedures to inform the SGSN when it has entered a new RA. The MS does not inform the SGSN on a

change of cell in the same RA. Therefore, the location information in the SGSN MM context contains only the GPRS RAIfor MSs in STANDBY state.

The MS may initiate activation or deactivation of PDP contexts while in STANDBY state. A PDP context shall be activatedbefore data can be transmitted or received for this PDP context.

w READY State

In READY state, the SGSN MM context corresponds to the STANDBY MM context extended by location information for thesubscriber on the cell level. The MS performs mobility management procedures to provide the network with the actualselected cell. GPRS cell selection and re-selection is done locally by the MS, or may optionally be controlled by thenetwork.

An identifier of the cell, the Cell Global Identity including RAC and LAC, is included in the BSSGP header of the datapacket from the MS; see GSM 08.18 [21].

The MS may send and receive PDP PDUs in this state. The network initiates no GPRS pages for an MS in READY state.Pages for other services may be done via the SGSN. The SGSN transfers downlink data to the BSS responsible for thesubscriber's actual GPRS cell.

The MS may activate or deactivate PDP contexts while in READY state.


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2 GPRS Operation2.3 MS Radio Resource Operating Modes

Packettransfer mode

Packetidle mode

Packetidle mode

Ready Standby

RR

MM

> Packet transfer mode

In packet transfer mode, the mobile station is allocated radio resource providing a

Temporary Block Flow (TBF) on one or more physical channels. Continuoustransfer of one or more LLC PDUs is possible. Concurrent TBFs may be establishedin opposite directions. Transfer of LLC PDUs in RLC acknowledged or RLCunacknowledged mode is provided.

> Packet idle mode

In packet idle mode no Temporary Block Flow. Upper layers can require thetransfer of a LLC PDU which, implicitly, may trigger the establishment of TBF andtransition to packet transfer mode.

> MS RR operating modes vs MS MM states

w Packet idle mode

While operating in packet idle mode, a mobile station belonging to GPRS MS class A may simultaneously enter the different

RR service modes. A mobile station belonging to either of GPRS MS class B or C leaves both packet idle mode andpacket transfer modes before entering dedicated mode, group receive mode or group transmit mode.

w Packet transfer mode

When selecting a new cell, mobile station leaves the packet transfer mode, enters the packet idle modewhere it switches to the new cell, read the system information and may then resume to packet transfer mode in the newcell.

While operating in packet transfer mode, a mobile station belonging to GPRS MS class A may simultaneously enter thedifferent RR service modes. A mobile station belonging to either of GPRS MS class B or C leaves both packet idle modeand packet transfer modes before entering dedicated mode, group receive mode or group transmit mode.


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Routers

IP network

2 GPRS Operation2.4 Basic Procedures

ipip ipip ip

http httpftp ftpsmtp smtp

1tcp1tcp

wap wap

gtp

SGSN

GGSN

> IP overview


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nK bytes MESSAGE

4K bytes PACKET 4K bytes PACKETTCP

TCPIP IP IP

TCPIP Z Ethernet 1.5k frames

Y Datagrams IP

TCPx 4k TCP packets

L4

L 3

L2



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DATASHEADER

456

HEADER

57 X 8

456

DATASHEADERIP / X25

HEADER DATASSNDCP

SNDCP

DATASHEADERLLC

RLC/PCU

AIR INTERFACE

57 57

Max 1600Bytes SGSN to MSCRC

TRE / CCU



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> Transmission plane

TCP HTTP FTP SMTP

PhysicallayerPhysicallayer PhysicallayerPhysicallayerPhysicallayerPhysicallayerPhysicallayer

L2

IP

UDP

GTP

IP

L2

MAC

L2

IP

UDPLLC

GTP

BSSGP

(FrameRelay)

(FrameRelay)

LLC

Um Gb Gn Gi

MSBSS

(with PCU) SGSN GGSN

Application

RLC

MAC

RLC

MAC

IPIP

relay

relay

BSSGP

SNDCPSNDCP

w GTP (GPRS Tunnelling Protocol) tunnels user data between GPRS Support Nodes in the backbone network. The GPRSTunnelling Protocol shall encapsulate all PDP PDUs.

w UDP (User Datagram Protocol) carries GTP PDUs for protocols that do not need a reliable data link (e.g., IP), andprovides protection against corrupted GTP PDUs.

w IP (Internet Protocol) is the backbone network protocol used for routing user data and control signalling. The backbonenetwork may initially be based on the IPv4. Ultimately, IPv6 shall be used.

w SNDCP (SubNetwork Dependent Convergence Protocol ) maps network-level characteristics onto the characteristics ofthe underlying network.

w LLC (Logical Link Control) provides a highly reliable ciphered logical link. LLC shall be independent of the underlyingradio interface protocols in order to allow introduction of alternative GPRS radio solutions with minimum changes to the

NSS.

w Relay. In the BSS, this function relays LLC PDUs between the Um and Gb interfaces. In the SGSN, this function relaysPDP PDUs between the Gb and Gn interfaces.

w BSSGP (Base Station System GPRS Protocol) conveys routing and QoS-related information between the BSS and theSGSN. BSSGP does not perform error correction.

w (NS) Network Service transports BSSGP PDUs. NS is based on the Frame Relay connection between the BSS and theSGSN, and may - multi-hop and traverse a network of Frame Relay switching nodes.

w

RLC/MAC (Radio Link Control / Medium Access Control). The Radio Link Control function provides a radio-solution-dependent reliable link. The Medium Access Control function controls the access signalling (request and grant) proceduresfor the radio channel, and the mapping of LLC frames onto the GSM physical channel.


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NSAPI

NSAPITLLITLLI

Radio layers

LLC

GMM/SM SMS

SNDCP

IP

NSAPIi

> MS high protocol layers

w SNDCP (Sub-Network Dependent Convergence Protocol)

Data compression, segmentation of large packets, recognition of PDP-PDU sessions (according to their NSAPI), inclusion

of QoS (use of SAPIs on the LLC link).

w NSAPI (Network Service Access Point Identifier)

This is used for a particular MS to distinguish different PDP contexts (= sessions)

by the PDP-type: X.25 or IP, or mainly by

the APN to be reached, or by

the required QoS.

w LLC (Logical Link Control)

Provides a safe link, encrypted and independent of the physical bearer, independent to BSS brand.

w TLLI (Temporary Logical Link Identity)

Identifies a logical link with the MS (one TLLI per MS)

w GMM/SM (GPRS Mobility Management / Session Management)

MS-SGSN signaling protocol for Gprs Mobility Management/ Session Management

w SMS (Short Message Service)


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NMC-NSS

HPLMN

HLRMS

APN accessible through FPLMN-GGSN ?

etc ...

& MSISDNIMSI

network access mode :

For each MS

GPRS | NSS | both

subscribed PDP contexts (maximum of n) :

PDP type :

[PDP address (IP@) ]

Access point name (APN) or * (= wild card)

QoS profile

IP | PPP

ntimes

> HLR GPRS data

w PDP address

Almost always empty. The network then dynamically assigns (using a DHCP server) an IP address to the subscriber when

he activates his PDP context (seen later).

w PDP contexts

Each PDP context can be considered as a BS (basic service = telephony, fax, etc). A PDP context is a dialog session withan external IP network, identified with an APN. It is not always mandatory to subscribe (in the HLR) to PDP contexts,access to some networks is free. For a user, the traffic of his different sessions will be recognized in the messages by theuse of different NSAPIs. A user can declare one of his PDP contexts as the default.

w APN (Access Point Name)

The APN represents an IP network. An APN has two parts: the APN-Network Id (example: wanadoo.fr) and the APN-operId (example: mnc...gprs)

Examples of APN: wanadoo.fr.mnc001.mcc208.gprs,

APN = * (wildcard) potentially authorizes the MS to activate any APN.

w Valid APN

Boolean, if YES, indicates that this APN can be reached through the GGSN of the visited FPLMN.


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> GPRS attachment

BSS

Authent_info_req()

Authent_info_respq)

|

Update_loc_req()

}

Insert_subs_data()

Update_loc_ack()

~

PLMN

Attach-Request(IMSI)

Attach_resp (P_TMSI)

Attach_complete ()

MS_authentication_procedure GPRS IPbackbone

GGSN

SGSN

N7

HLR

w Attach Request.

The attach_request message is placed in an LLC frame. x

The MS sends its IMSI.

w Authentication

The SGSN gets the authentication triplets from the HLR:

triplets request message y

triplets response message z

The SGSN performs the authentication procedure with the MS: {

triplets request message y

triplets response message z

w Location Update

The SGSN performs the location_update procedure with the HLR:

location_update request message |

the HLR transfers the MS_subscription data to the SGSN }

the HLR terminates the location_update procedure ~

w Attach Complete

The SGSN terminates the attach_procedure with the MS :

attach_accept message (with a new P_TMSI allocation)

attach_complete message (since a new P_TMSI has been allocated)


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GPRS - CN


LLC layer

TLLI1

GPRS IPbackbone

> GPRS attachment

After a GPRS_Attach procedure The mobile is connected to the serving SGSN

SGSN1

SGSN

2

GGSN1

GGSN

2 PDN 2

PDN 1

w Attached MS

After running the attach procedure, the MS is GPRS_attached:

a logical connection is established between the MS and the SGSN connection established between the peer LLC layers in the MS and the SGSN

this connection is identified by the TLLI (Temporary Logical Link Identity)

this logical connection remains established until the MS detaches

the MS can now access to GPRS services and is reachable for GPRS services


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> PDP context activation

GPRS Core Network

GPRSbackbone

PDN1

SGSN

DNS

GGSN

GGSN PDN2

DHCP

BSS

PLMN

TLLI1

4

2

3Create_PDP_req (PDN2)

5 Create_PDP_resp (@IP_MS)

Activate_PDP_req (PDN2)

Activate_PDP_resp(@IP_MS)}}}}

w MS IP address

In case of IP PDP_type access with no additional mobile authentication procedure, the MS IP address is provided by the

PLMN, using either the subscription data, or the backbone DHCP server. No additional user authentication is needed ontop of the GPRS authentication mechanisms (i.e. using IMSI and authentication triplets)

w PDP Context Activation

MS requests for a PDP_context activation, providing the name of target Packet Data Network (PDN2parameter).

SGSN queries the backbone Name Server (here DNS) to identify the GGSN giving access to the Data NetworkPDN2 (here GGSN2).

SGSN sends a Create_PDP message to the corresponding GGSN2, in order to setup a GTP tunnel.

GGSN2 allocates an IP address to the MS (@IP_MS), using the backbone DHCP server.

GGSN2 acknowledges the Create_PDP message to the SGSN, returning the @IP_MS allocated to the MS.

SGSN acknowledges the Activate_PDP message to the MS, with the allocated @IP_MS.


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BSS

PLMN

TLLI1

GPRS Core Network

GPRSbackbone

SGSN

DNS

GGSN

GGSN

2

3Create_PDP_req (PDN2)

6 Create_PDP_resp (@IP_MS)

Activate_PDP_req (PDN2)

Activate_PDP_resp(@IP_MS)}}}}ISP

INTRANET

DHCP

RADIUS

5

Authentication andaccounting

Address allocation

4

w MS address

IP PDP_type access with mobile authentication via a RADIUS. The address allocation server (i.e. DHCP) and/or

authentication server (i.e. RADIUS) may be located within the PLMN or in the ISP/Intranet network. Non-transparentaccess is aimed for corporate intranet access, where additional user authentication is often required.

w PDP Context Activation

The authentication data are piggybacked in the Protocol Configuration Options (PCO) field of the PDP contextactivation messages and .

, , same as for IP PDP_type in transparent access.

GGSN performs the user authentication towards a RADIUS server.

GGSN allocates an @IP to the MS using the intranet/ISP DHCP server.

, same as for a PDP context in transparent access.


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LLC layer

GPRS - CN

TLLI1

GPRS IPbackbone

SGSN

1

SGSN2

GGSN1

GGSN2

PDN 2

PDN 1TID 1 = IMSI + NSAPI 1

TID2=IMSI+NSAPI2

by the GTP layer

after PDP_context_activation procedures

w User data transfer

In order to achieve a proper transfer of User Data, two main protocols are used: GTP (between GGSN and SGSN) and

LLC (between SGSN and MS), and two types of logical connections are established: MS SGSN. Logical Link used for signaling and data transfer, created at GPRS attach (unique per MS),

identified by a TLLI value;

SGSN GGSN. Created with the activation of PDP context = when opening a session (several per MS),identified each by a TID value.

w TLLI (Temporary Logical Link Identity)

Identifies uniquely a MS attached to the GPRS core network (Standby or Ready state).

w TID (Tunnel Identity)

Identifies a logical connection ("tunnel") between GGSN and SGSN (for each session of each MS). TID= IMSI+NSAPI.


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LLC layer

GPRS - CN

TLLI1

GPRS IPbackbone

SGSN1

SGSN

2

GGSN1

GGSN

2 PDN 2

PDN 1TID 1 = IMSI + NSAPI 1

TID2=IMSI+NSAPI2

by the GTP layer

after PDP_context_activation procedures

ul/dl data_transfers


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SGSNGGSN

within the MS

MS

over the Gn interface

over the Gi

interface

@ MS@server

U-data

@sgsn@ggsn

GTPheader

UDPheader

@ MS@server

U-data

@ MS@server

U-data

@server@ MS

U-data

server

PDN

@ggsn@sgsn

GTPheader

UDPheader

@server@ MS

U-data

@server@ MS

U-data


> User data transfer

w User data transfer

Data are transferred from header translation, then encapsulation in underlined protocol data unit.

At the GGSN, the IP address of the MS is used to retrieve a PDP context and therefore a TID and the address of thecurrent SGSN.

At the SGSN, the TID is used to work out the NSAPI and the IMSI (therefore the TLLI). If the MS is ready, no need forpaging because the MS is located to the exact cell.


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2 GPRS Operation2.5 Charging

> Charging process

MS

PDNGPRSBACKBONE

GGSNSGSNBSSTLLI

CCBS

CG

Attachment

M_CDR

PDP CONTEXT ACTIVATION AND DATA TRANSFERT

S_CDRG_CDR

FTP

GTP

w CDR (Call Detail Record)

CDRs are used for subscriber charging, statistics and location purposes.

Three types of CDR are managed within the GPRS backbone: M-CDR related to the GPRS mobility of a mobile station

S-CDR related to PDP-contexts activation and data transfers as seen by the SGSN

G-CDR related to PDP-contexts activation and data transfers as seen by the GGSN

CDRs, generated by the xGSN, are then sent to the CG (Charging Gateway) :

periodically,

using reliable transfers (GTP over TCP)

The CG forwards those CDRs to external CCBS (Customer Care and Billing System)

w CDR content

Here are the main information in the CDR :

IMSI

location information (LAC + RAC + Cell)

APN

PDP-context identifier

PDP-context start time and duration

negotiated QoS

volume of data sent / received

source and destination PDP addresses,

.


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2 GPRS Operation2.5 Charging

> Charging process

INTER PLMN NETWORK

HPLMN GGSN PDN

BGCCBS

CG

S_CDRHOME PLMN

MS

SGSN

BSS

TLLI

VPLMNBG

CG CCBS

VISITED PLMN

G_CDR

w Charging data collection for inter-PLMN charging

Use of G_CDR and S-CDR as specified by GSM 12.15

Inter-operator agreement to transfer between Billing Systems


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Public Internet

2 GPRS Operation2.6 Security

1- Secured network access Authentication of MSs and confidentiality oftheir identity Possibility of encrypting user data

Possibility of verifying IMEI with an EIR (Gf)

2- Secured backbone IP networkFirewall = application-level filteringFiltering by access lists (in the GGSNs)

GPRS Network

3- Secured intranet accessAPN with mandatory subscriptionAPN with access listsAPN with tunneling on Gi (IPsec)

w Authentication and confidentiality

As in GSM, by security triplets and the use of the TLLI/P_TMSI instead of the IMSI.

w Encryption

The LLC frame is encrypted, so encryption from the MS to the SGSN and not just on Um.

w Firewall

Filtering function installed on routers (ex: GGSN). Packets are rejected by filtering at application level (for example: in http,some URLs are barred). Also makes it possible to hide the IP addresses of MSs and backbone entities from external hosts(Network Address Translation function).

w Access Lists (IP addresses lists)

A function of Cisco routers (and therefore of GGSNs). Each APN is linked to two lists of IP addresses to be checked during

the PDP context activation phase (calling address and called address in both UL and DL directions).These lists are therefore used to protect access to the operator's backbone IP, but also to filter the access to externalPDNs.

At the GGSN, some APNs can be declared "with mandatory subscription" (at the HLR) and therefore inaccessible to otherMSs.

w Tunneling

Several ways:

by IPsec (Secured IP) = IP version in which the user data is encrypted (IP datagrams payload but not their header).Or by Generic Routing Encapsulation (GRE)

by PPTP (Point-To-Point Tunneling Protocol). Refer to ANNEX for PPP Tunneling.


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Time allowed :

5 minutes

2 GPRS OperationExercise (1/3)

True or False?

The GGSN reads the header of user packets arriving from the PDN

The GPRS HLR knows the location of an MS to the nearest RA

With each web page downloaded, a new PDP context must be

activated

A CDR is generated for each packet sent or received

The SGSN can be considered as PMSC and PVLR

A TLLI is a virtual connection between a GPRS attached mobile and the

GGSN

w PMSC: Packet MSC.

w PVLR: Packet VLR.


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Time allowed :

5 minutes


True or False ?

The Charging gateway provides a single interface towards the billing centers

No need for paging to send a packet to a mobile in the "Ready" state

Attachment to the network does not involve GGSN


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Time allowed :

5 minutes


What interfaces of the GPRS NSS does a packet cross from a PDN to an MS?

Why , theoretically, is an RA smaller than an LA?


51/121




Thank you for answeringthe self-assessment

of the objectives sheet

2 GPRS OperationEvaluation

> Objective : to be able to describe theorganization of a GPRS network :

architecture, interfaces, protocols,


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3 The Base Station Subsystem


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3 The Base Station SubsystemSession presentation

> Objectives :

To be able to briefly describe the datainterchange mechanisms through the BSS

> Program :

3.1 3GPP Position

3.2 Alcatels Choice

3.3 Layered Model

3.4 Gb Interface

3.5 Radio Interface


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3 The Base Station Subsystem3.1 3GPP Position> PCU function

BSSBTS

CCU PCU

BSC SGSN

BSSBTSCCU

BSC SGSN

PCU

BSSBTS BSC SGSN

CCU PCU

w PCU functions

RLC and MAC layers: LLC frame transportation (segmentation/reassembly),

Gb interface end point, network access functions (radio resource management),

radio channel management (power control, congestion control, etc).

w CCU functions

encoding suited to radio channels,

radio measurements (receive quality, signal level, "timing advance" management).


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3 The Base Station Subsystem3.2 Alcatels Choice> PCU function

BTS

CCU

BSC SGSNMFS

Abis Ater Gb

GSL

LLC Transmission check between SGSN and MS

RLC Transmission check between PCU and MS

GCH transmission check between PCU and TRE

MFS is just the name of therack containing PCU functions

PCU

BSS

w The Multi BSS Fast packet Server (MFS):

w MFS is just the namee of the rack containing PCU functions

performs the GPRS Packet Control Unit (PCU) functions (3GPP 03.60 standard), manages the Gb interface with the GPRS & EGPRS core network,

performs the Serving Mobile Location Center (SMLC) functions,

manages the SAGI interface with the A-GPS server.


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3 The Base Station Subsystem3.3 Layered Model

BTS MFS SGSNMS

BSSGP

Gb

Physicallayer

Frame

relay

RLC

MAC

RLC

Physicallayer

Frame

relay

BSSGP

Um Abis/Ater

PCU

IP

LLC

GMMSM

relay

LLC

GMM SNDCPSM

relayPhysicallayer

Physicallayer

L2-GCHL1-GCH

L2-GCHL1-GCH

MAC

SNDCP

> User plane

w For GPRS TRAFFIC, the BSS simply relays the LLC frames between the MS and the SGSN.

w BSSGP = BSS Gprs Protocol. Functions:

to relay LLC frame over the Gb, with no guarantee of integrity (relaying user data and GMM / SM messages :session, RA_update and paging procedures). Conceals the FR layers for the LLC layer.

SGSN-MFS signaling = management of Gb interface objects (flush, paging, resume suspend, LLC-discarded andother procedures).

cell-SGSN traffic management (identified by BssgpVCs): in particular cell update management (in the same RA):the BSSGP header always indicates the current cell so if a "ready" MS moves into a new cell, then the SGSNstores this new cell and sends all the unacknowledged LLC_PDUs to it (DL).

w The concept of handover has no meaning in packet switching (GPRS). There is no "circuit" to re-establish!

w RLC = Radio Link Control. (Provides a safe link for transporting LLC-PDUs in acknowledged or unacknowledged mode,LLC-PDU segmentation into blocks and reassembly, management of TBF contexts. RLC depends on the physical bearer:data encoding, error control and flow control suited to GSM channels.

w MAC = Medium Access Control. Multiplexing of RLC frames onto PDCH (transfer of blocks over the different PDCHi).Including traffic sharing over several TSs or, conversely, the use of one TS for several users.


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BSC MFSBTSMS

3 The Base Station Subsystem3.3 Layered Model

Gb

L2-GSLL1-GSL

BSCGPBSCGP

L2-GSLL1-GSL

physicallayer

RRM

AterUm

relay

Abis

relay

physicallayer

RRM

> Signaling plane

w BSCGP protocol

administration interface of Radio Resource management :

(de)allocation of PDCH and MPDCH within a cell activation / release of PDCH

System control information:

BSC reset procedure

cell and GIC group state management

Radio signalling :

GSM / GPRS paging,

GPRS access procedure

w RMM protocol

dynamic allocation of Radio Resources to a MS :

radio blocks from one or several PDCH

for uplink or downlink data transfers


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NSE2

SGSN

NSE1NSE1

NSE2

F.RF.RNetworkNetwork

PCM

3 The Base Station Subsystem3.4 Gb Interface

PCM

PCM

BVCI=2

BVCI=1

BVCI=3

BVCI=5

BVCI=6BVCI=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

> Managed entities










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3 The Base Station Subsystem3.4 Gb Interface

GPRS Core Network sideBSS side

> Protocols

SGSNPacket Control Unit function(PCU)

BSS GPRS Protocol

(BSSGP)BSS GPRS Protocol

(BSSGP)

Network Service Control

(NSC)Network Service Control

(NSC)

BVCI=2

BVCI=1

BVCI=3

BVCI=5

BVCI=6

BVCI=4

BSC1

BSC2

Sub-Network Service

(SNS)

Physical layer

Sub-Network Service

(SNS)

Physical layer

Frame Relay

BVC

NS-VC

NSE

PVC

PCM PCM

BC










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3 The Base Station Subsystem3.5 Radio Interface 1/8

> GPRS / EGPRS throughput

Coding Scheme ModulationMaximum rate

per PDCH (kb/s)

CS2

CS1

GMSK

GMSK

13.4

9.05

CS4

CS3

GMSK

GMSK

21.4

15.6

GPRS

MCS9

MCS8

8-PSK

8-PSK

59.2

54.4

MCS7

MCS6

MCS5

MCS4

MCS3

MCS2

MCS1

8-PSK

8-PSK

8-PSK

44.8

29.6 / 27.2*

22.4

17.6

14.8 / 13.6*

11.2

8.8

GMSK

GMSK

GMSK

GMSK

* in case of padding

EGPRS


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> Coding schemes

Bad radio condition

Max security

Good radio condition

Min security

Maximum number of bits tohave security Max number of bits foruser data

POOR USER BIT RATE BETTER USER BIT RATE

CS2CS1 CS3 CS4



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> GMSK / 8-PSK modulations

GMSK

8-PSK

1 0 1 1

001 101 011 001

GMSK270 kb/s

8-PSK810 kb/s

Gross bit rateper carrier1 bit per

Symbol

3 bitS perSymbol

8 PSK has 3times more capacity than GMSK

One TS 142 symbols142 BitsONE TS

One TS 142 symbols426 BitsONE TS

w Transmission and reception data flows are the same for GPRS and EGPRS, except for EGPRS MCS-9, MCS-8 andMCS-7, where 4 normal bursts carry 2 RLC blocks (1 RLC block within 2 bursts for MCS-9 and MCS-8).

w Radio blocks are transported on the air interface (Um) over 4 consecutive normal bursts of the TDMA frame.

w The GMSK normal burst is composed of 156.25 symbols (1 bit for 1 symbol):

6 tail symbols,

26 training sequence symbols,

114 encrypted symbols,

2 stealing flags (2 symbols),

8.25 guard period (symbols).

For GMSK, the radio blocks are transported by 114 x 4 = 456 symbols.

w The 8-PSK normal burst is composed of 156.25 symbols (3 bits for 1 symbol): 6 tail symbols,

26 training sequence symbols,

116 encrypted symbols (there is stealing flags),

8.25 guard period (symbols).

For 8-PSK, the radio blocks are transported by 116 x 4 = 456 symbols.


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> Transmission Rate with 8 PSK modulation

MCS9

59,2k

MCS8

54,4k

CHANNEL

MCS7

44,8k

MCS6

29,6k

MCS5

22,4k

MCS4

17,6k

MCS3

14,8k

MCS2

11,2k

MCS1

8,8k


Maximum number of bits to have security Max number of bits for user data

Bad radio condition Good radio condition


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> Impact of EGPRS (Edge) on terrestrial transmissions in BSS


Extra capacity Extra capacity

Abis AterGMSk and Not agood transmission

CS1 about 9K

MCS9 ABOUT 59K

8PSK goodtransmission


MFS

PCUBTS

TRXBSCrelay

PDCH

BTS

TRXBSCrelay

MFS

PCU16k resource 16k resourcePDCH




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> Resources allocation according to the MCS

QUALITY OF TRANSMISSION LOT OF BITS LOST

INCREASE SECURITY DECREASE USEFUL TRANSMISSION RATE


MCS n


MFS

PCUBTSTRX BSCrelayPDCH


MCS n-1

PDCH



MFS

PCUBTS

TRXBSCrelay


Can be allocated toanother PDCH

Can be allocated toother PDCH


w When the operator decide that the TRX will run MCS n all the terrestrial resources will be allocated , but if the quality ofthe radio transmission is bad the PCU decides to increase the security on the air interface, the useful transmission rate onthe PDCH will be decreased and less capacity will be needed on the terrestrial transmission .

w The resource which is not used a that time can be allocated to another TRX if needed at BTS level

w The RLC blocks coming from different are multiplexed on the common resource for all the PDCH in the TRX which iscalled M EGCH (Multiplexed EGCH)


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networkMSstart

of TBF1end ofTBF1 TBF2 TBF3

TBF4

timefULiPacket Channel Request

Packet Resource Assignment(list of PDCHi, token=T,TFIk)

MS starts listening to all DL blocks token valueon the allocated PDCHi

SEND on block b+1 (TFIk)

in block btoken =T ?

Y

N

T T T T T T DL PDCHi

? TFIk TFIk TFIk TFIk TFIk TFIkUL PDCHi

3 The Base Station Subsystem3.5 Radio interface 7/8> UL transfer

PCU

TBF MAC

w This slide demonstrate that the radio resources (blocks) are used only when data need to be transferred (LLC-PDU) :dynamic radio resource allocation. As a matter of fact, an MS shall specify its radio resource request at initiation of eachTBF for a better optimization of radio resource & MS capabilities.

w A TBF (the blue shape) comprises one or more consecutive LLC-PDUs.

w Temporary (Block) Flow Identity = TLLI + sequential number, used by the network to recognize data from different MSs.Identifies uniquely a TBF in one direction within a cell.

The blocks are dynamically allocated upon the use of a token (Uplink State Flag) allocated to the MS at TBFestablishment. Any DL block includes a USF in the header.

The mobile "listens" to the PDCHi assigned, when block b (in DL) contains USF = T, the MS shall send onePDTCH in UL on block b+1 on the UL PDCHi.

w The theoretical maximum of 160 kbit/s is given for one MS which would have 8 PDCHs of 21.4 kbit/s each. Those MS areyet to be available on the market place.


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PS Paging

Paging Request ("packet")Packet Paging Response

Packet Resource Assignment

(list (PDCHj),TFIz)

The MS consumes the content of block b

in block b, TFI=TFIz ?

Y

N

PCU SGSN

UL TBF: refer toprevious slide

MS PDU

MS starts listening to all DL blocks TFI valueon the allocated PDCHj

Z Z Z Z ZDL PDCHj

3 The Base Station Subsystem3.5 Radio interface 8/8

> DL transfer

MS IN STANB BY

MODE

MS IN READYMODE

w In DL, each time an LLC-PDU is received, if there is no TBF in progress, it is essential to establish" one.

w To respond to the paging, the MS needs to send a "paging response" to the SGSN (GMM) encapsulated in an LLC_PDU.

This response is carried by an UL TBF.

w Upon reception of the Paging response, the SGSN can send the DL PDU (LLC frame) to the MS through the MFS.The MFS shall establish a DL TBF with the MS.

w DL TBF: each block of the DL TBF are identified by the DL TFI = TFIz

w After completion of the TBF establishment phase, the MS listen to all the DL blocks on the allocated PDCHs and keeps theblocks tagged with the TFIz.


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Time allowed :

5 minutes

3 The Base Station SubsystemExercise (1/2)

True or False?

The SGSN is linked to the BSS by an interface based on

the Frame Relay protocol

For each cell, the number of channels which can beused for GPRS traffic is operator-configurable

If a user packet is lost at the Gb interface, it can berecovered using frame relay protocol mechanisms

The LLC protocol is independent of the type of BSS

employed


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Time allowed :

5 minutes

3 The Base Station SubsystemExercise (2/2)

True or False?

In a cell, a TRX can carry eight PDCHs

One PDCH can be allocated in its entirety to a single user

If necessary, blocks on different PDCHs can be allocated to asingle user

The NSEI is the identifier used by the SGSN to indicate thedestination cell of a LLC frame to the MFS

The same quantity of PVCs is declared on the MFS and SGSNsides


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Thank you for answeringthe self-assessment

of the objectives sheet

3 The Base Station SubsystemEvaluation

> Objective : To be able to briefly describethe data interchange mechanisms throughthe BSS


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4 Alcatel Solution


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4 Alcatel SolutionSession presentation

> Objectives: to be able to characterize the solutionoffered by Alcatel

> Program: 4.1 GPRS Network Overview

4.2 Alcatel 9135 MFS

4.3 Packet Switched Core Network

4.4 GPRS Network Management

4.5 Alcatel QoS Offer


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GPRS Core Network

4 Alcatel Solution4.1 GPRS Network Overview

BSS1

BSC

BTS

BTS

BSS--

BSCBTS

BTS

A9135

MFS

BSS2BTS

BTS

BSC

A9135

MFS

GSM/GPRS common servers

HLRSMS-CMSC

GPRS IPbackbone

Radio subsystem

FrameRelay

network

BorderGateway Inter-PLMN

backbone

Internet

Intranet

SGSN

SGSN

accessrouter

SCP

CAMEL & IP basedPrepaidServices

Firewall

Charging Gateway

OMC-CN

iGGSN

w Within the radio subsystem :

Existing Alcatel BTS and BSC from GSM are reused for GPRS :

no need of hardware change to provide GPRS features

need just software upgrade

The GSM-BSS now includes a proprietary equipment :

Alcatel A9135 = MFS (Multi BSS Fast packet Server)

which deals with the GPRS PCU functions

w Within the GPRS Core Network :

both SGSN and iGGSN are Alcatel proprietary equipments

Charging Gateway and OMC-CN are Alcatel components based on HP platform

Firewalls, Border gateway and access routers are standard IT components

w The HLR, MSC, SCP and SMS-C are reused from the GSM-NSS


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Telecom Subsystem

4 Alcatel Solution4.2 Alcatel 9135 MFS

Control Subsystem

Gb ifA-ter if

BSC1

BTS

BTS

> Functional architecture

GPU1PCU

GPU2PCU

S

G

S

N

LAN x 2

OMC-RM

F

S

BSC2

BTS

BTS

GPU1PCU

GPU1PCU

w The duplex "Control subsystem" (two DS10 in active/standby mode, with 2 shared disks) :

controls the telecom subsystem (initialization, supervision, defence)

provides the management interface (OMC-R or local maintenance terminal)

w The Telecom subsystem is composed of GPU boards :

1. GPRS Processing Unit (GPU).

2. Each GPU board performs the PCU functions towards the BSC and the SGSN

16 PCM ports per GPU board

some PCM ports connected to the BSS, the other to the SGSN

w There are two different configurations regarding the support of BSC by the GPU boards :

only one GPU board supporting each BSC (in the B6.2 release)

multiple GPU boards supporting each BSC (from the B7 release)


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PCU

PCU

PCU

PCU

PCU

SGSN

PMSCPVLR

MFS

FRAME

RELAY

120 CICs

120 GICs 16K

TC SM

PVC

BEARER CHANNEL

Muxed ATer

A Interf

Gb

BSC

BSC

BSC

BSC

BSC

MSC

4 Alcatel Solution4.2 Alcatel 9135 MFS CONNECTIONS


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4 Alcatel Solution4.2 Alcatel 9135 MFS

1 BSXTU11 GPU (+1)

maxi

1 BSXTU11 GPU (+1)

maxi

1 BSXTU11 GPU (+1)

maxi

1 BSXTU11 GPU (+1)

maxi

2 DS 10Control

sub-rack

2 DS 10Control

sub-rack

2 or 4Switches3 COM 3300

+ IOLAN module

2 or 4Switches3 COM 3300

+ IOLAN module

> Rack layout

w The "Control sub-rack" part is duplex (two DS10 in active/standby modes).

w each BSXTU sub-rack contains a maximum of 12 JBGPU boards.

The GPRS traffic of one BSC can be handled by several GPUs (up to six are foreseen from the same MFS rack)

Since B7, a full MFS contains from 4 to 22 BSS (BSC), due to multi-GPU feature

4 BSS per MFS: 2* (1 BSS / 6 GPU)+(1 BSS / 5 GPU)

22 BSS per MFS: 22*(1 BSS/GPU)

w One JBGPU board (= 1 PCU) offers 480 PDCH. Two uses of JBGPUs :

1. One JBGPU for each BSC, (Ater interface), so one MFS serves a maximum of 22 BSCs.

2. With 240 PDCH per GPU, a BSC can offer up to 6*240 = 1440 PDCH

3. To be connected to the FR network (Gb interface).

w Fast ethernet Switches (100 Mb/s) made by 3COM: 2 or 4 (as needed) to build LANs to which are connected the Nectar stations (DS10)

GPU boards

printers and craft terminals (for local management, the terminal is called IMT = Installation & MaintenanceTerminal)


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4 Alcatel Solution4.2 Alcatel 9130 MFS (1/3)

ATCAshelf

ATCAshelf

w This platform is a high availability distributed platform composed of blades compliant with the Advanced TelecomComputing Architecture (ATCA) open standard

wATCA has been developed by the PCI Industrial Computers Manufacturers Group (PICMG).

w The related specifications are described in the PICMG 3.0 R1.0.


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ATCAshelf

ATCAshelf

MFS

LIU LIU

MFS

MFS

O

M

C

P

S

S

W

S

S

W

O

M

C

P

GP

GP

GP

GP

GP

GP

GP

GP

GP

GP


General Option 1 Option 2ATCA shelf content

w LIU: Line Interface Unit to collect the external PCM connections

w GP: GPRS Processing module

w OMCP: O&M Control Processing board the control stations,w SSW: Subrack SWitch


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GPGPGPGPGP

GP

GPGP

GPGP

MUX

OMCP

MUX

16 LIU X 16 E1

LIU

E1 connections

Abis

LIU

Ater

OMCP

S

S

W

S

S

W

MFS

9 PCU + 1SPARE

w LIU shelf: Multiplexes/demultiplexes and cross connects all E1 external links to/from NE multiplexed links (n E1 overEthernet) on the TP and the GP board. Equipped with two Mux boards and n LIU boards, depending on capacity.

wThe LIU shelf hosts Two MUX boards which collect the E1 links from the 16 LIU boards on 16 serial links at 36.864 Mbit/sand build packets sent towards up to 32 directions (125ms each) on a Gigabit Ethernet link.

w SSW: its an Ethernet switch which allows exchanges between all platform elements and externalIP/Ethernet equipment.

w OMCP: these control stations are used to process defense functions and platform Operation, Administration andMaintenance (OAM) generic services..

w GP: Manages the user plane packet data flow processing.

w Ethernet links on the IP ports of the SSW switch: these links connect the platform to external IP equipment (i.e. OMC-R,external alarm box).


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> iGGSN

4 Alcatel Solution4.3 Packet Switched Core Network

GPRS

signaling & userPlane Blades

GPU

Gb

Ethernet LAN (internal com.)Switching & Routing

O&M, Charging

SS7 Blades

Pilot Blades> S

Date post:	30-May-2018
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Evolium Base Station Subsystem Introduction to Gprs/Egprs

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