GPRS Day 1_start.ppt

CHOIX DU TRANSPORTEUR LONGUE DISTANCEPage *
INTRODUCTION
GPRS General Packet Radio Service (1)
01.60: Requirements specification of GPRS
01.61: GPRS ciphering algorithm requirements
02.60: Service description; stage 1
03.60: Service description; stage 2
03.64: Overall description of the GPRS radio interface; Stage 2
04.60: Mobile Station (MS) - Base Station System (BSS) interface; Radio Link Control / Medium Access Control (RLC/MAC) protocol
04.64: Mobile Station (MS) - Serving GPRS Support Node (SGSN); Logical Link Control (LLC) layer specification
04.65: Mobile Station (MS) - Serving GPRS Support Node (SGSN); Subnetwork Dependent Convergence Protocol (SNDCP)
07.60: Mobile Station (MS) supporting GPRS
© Alcatel University - 8AS 90125 0143 VT ZZA Ed.01
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INTRODUCTION
GPRS General Packet Radio Service (2)
08.14: Base Station System (BSS) - Serving GPRS Support Node (SGSN) interface; Gb interface layer 1
08.16: Base Station System (BSS) - Serving GPRS Support Node (SGSN) interface; Network Service
08.18: Base Station System (BSS) - Serving GPRS Support Node (SGSN) interface; BSS GPRS Protocol (BSSGP)
09.16: Serving GPRS Support Node (SGSN) - Visitors Location Register (VLR); Gs interface network service specification
09.18: Serving GPRS Support Node (SGSN) - Visitors Location Register (VLR); Gs interface layer 3 specification
09.60: GPRS Tunnelling Protocol (GTP) across the Gn and Gp Interface
09.61: Interworking between the Public Land Mobile Network (PLMN) supporting GPRS and Packet Data Networks (PDN)
12.15: GPRS charging
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Packet segmentation/re-assembly and scheduling
Power control
SGSN (Serving GPRS Support Node), the interface to the BSS
GPRS Mobility
Encryption
Charging
GGSN (Gateway GPRS Support Node), the interface to the Packet Data Network
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LAPD
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"Ready"
"Stand-by"
"Attach" is sent when switching on the mobile, "detach" when switching it off.
"Ready" state = paging not needed. Hence the benefit of this state for burst mode transfers. As long as the mobile in the ready state is sending or receiving packets, it remains "ready". If it stops, it switches to "standby" after a time delay.
In the ready state, any movement of the mobile is tracked by the SGSN to the nearest cell.
"Standby" state = paging needed.
Routing Area = Set of cells, subset of a Location Area (LA).
To avoid paging (much more frequent than in CS) on any more than a very small number of cells. The RAs are defined at the OMC-R and the code of the parent RA is broadcast over a cell's (P)BCCH.
"Idle" state = The mobile is not able to receive PDUs. It is seen as "not reachable". Mobiles that switch to the "idle" state remain in the P_VLR for a certain time before being purged.
Remember that the subscriber can remain "attached" to the network (in the ready or standby state) without paying anything as long as no packets are being exchanged.
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52 Frame - Multiframe on pdch:
52
GPRS (Packet Switching) (1)
Block 0
Block 1
Block 2
Block 3
Block 4
Block 5
Block 6
Block 7
Block 8
In the GSM standard, a physical channel for GPRS is called “Packet Data Channel” and unfortunately identified as PDCH which may lead to a confusion with logical channels
The multiframe is organised on 52 TS of 52 consecutive frames and transmitted information is put into blocks of 4 slots:
each block may carry one GPRS logical channel different from the previous or the following one.
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52
TFI: Temporary Flow Identifier:
created when data has to be transmitted and until all data have been transmitted
BSN: Block Sequence Number
TFI 43
TFI 2
TFI 39
BSN =21
BSN =22
BSN =23
TFI = 39
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GPRS
BCCH, PCH, RACH, AGCH can be used for GPRS. In this case the specific Packet channels (PBCCH, PPCH, PRACH, PAGCH) are not used for the corresponding functions
NCH is used for group calls
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GSM circuit-switched
Full Rate (FR) / Enhanced Full rate (EFR) speech: 13 Kbit/s
Half rate (HR) speech: 5.6 Kbit/s
Data transmission: maximum 14,4 Kbit/s
GSM packet-switched (GPRS) : 4 Coding Schemes
CS-1 : 9,05 Kbit/s (per TS)
CS-1 provides the best error protection (similar to signalling and control channels in GSM circuit switched)
the indicated rate corresponds to the use of the 12 blocks in the 52 frame-multiframe
the maximum theoritical rate in GPRS corresponds to 21.4 K bit/s x 8 TS = 171.2
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Principle close to offset quadri-phase shift keying
(OQ PSK) modulation, obtained by convolution of
an MSK ramp of height /2 and width 1 bit, by a
Gaussian function: "gradual" 0-1 or 1-0 transitions of ± /2 :
PROPERTIES :
Gradual transitions avoid the need to filter signal harmonics which are very weak
Spectrum efficiency of the order of 1 bit/Hertz
(270.8 kbaud/200 kHz)
adjacent frequencies in adjacent cells.
dB
0
-10
-20
-30
-70
0
100
200
300
400
-100
-200
kHz
p/2
t
0
T
2T
-T
-2T
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IP Network
GTP
Opening
Session(s)
An exchange of data between an MS and a PDN involves the creation of 2 logical connections:
MS <> SGSN. Created with the “attach”, the same for all sessions.
SGSN <> GGSN. Created with the “activation of PDP context” = opening the session
2 main protocols in packet routing:
LLC (between SGSN and MS): Logical Link Control
GTP (between GGSN and SGSN): GPRS Tunelling Protocol
2 corresponding identities:
TLLI = Temporary Logical Link Identity. Identifies a logical link MS <> SGSN (for any mobile in the "standby" or "ready" state).
TIDi = Tunnel IDentity, identifies a logical connection ("tunnel") between GGSNi and SGSN (for each session of each MS).
The IP network could be an international network = when the MS is in a foreign PLMN (FPLMN).
HPLMN
GGSN
FPLMN
SGSN
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IP overview
Layer 4, above IP, may be: TCP: Transport Control Protocol
or UDP: User Datagram Protocol
TCP guarantees data integrity (segment numbering [symbolized by the 1] - acknowledgements and retransmission), and not UDP.
Layer 4 handles the division/reassembly of the segments into IP packets.
http: Hyper Text Transmission Protocol,
protocol for transferring web pages (html).
ftp: File Transfer Protocol.
protocol for sending e-mails.
wap: "Wireless Application Protocol”
set of new protocols, specially devised for communications between MSs and servers with mobile-dedicated content (wml pages = wireless mark-up language) = taking account of reduced display capabilities and including a micro navigator (the 4 direction arrows).
GTP: GPRS tunelling Protocol.
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GTP
SNDCP
SNDCP
BSSGP
LLC
MS
BSS
SGSN
GGSN
Um
Gn
INTERCHANGES OVER THE NETWORK
relay
RLC
LLC
Gb
GTP
IP
GTP = GPRS Tunelling Protocol
For GPRS TRAFFIC, the BSS is only used for LLC frame relay between MS and SGSN.
LLC = Logical Link Control
(provide a safe link, independent from the physical support)
LLC frames carry user packets (inside SNDCP-PDU) or SGSN-MS signalling (GMM/SM).
RLC = Radio Link Control.
(provide a safe link, but dependent from the physical support: ack, error ctrl and flow control adapted to GSM channels)
MAC = Medium Access Control.
BSSGP = BSS GPRS Protocol. (Similar to BSSMAP)
Functions:
LLC frame relay without integrity guarantee
(relay of the user data and the GMM messages: Paging and indications on Um status). Hide FR layers for LLC layer.
SGSN-BSS signalling = Gb interface objects handling .
management of cell-SGSN traffic : flow ctrl + de-block +reset, particularly management of the cell update (in the same RA): the BSSGP header always indicates the serving cell . Therefore if MS is ready and it is a new cell, then SGSN stores this new cell and send back to it (DL) all the non-acknowledged LLC_PDU.
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Header
Data
LLC
PHYSICAL
Compression of each part
LLC Encapsulation
RLC Encapsulation
Block 1
Block 2
Block 3
Block 4
Block 5
Block 6
Block 7
Block 8
Block 1
Block 2
Block 3
Block 8
GTP = GPRS Tunelling Protocol
For GPRS Traffic, the BSS is only used for LLC frame relay between MS and SGSN.
MAC = Medium Access Control.
BSSGP = BSS GPRS Protocol. (Similar to BSSMAP)
Functions:
management of cell-SGSN traffic : flow ctrl + de-block+reset, particularly management of the cell update (in the same RA): the BSSGP header always indicates the serving cell . Therefore if MS is ready and it is a new cell, then SGSN stores this new cell and send back to it (DL) all the non-acknowledged LLC_PDU.
CRC is checked by RLC/MAC layer but generated by physical layer
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GMM
BSSGP
LLC
MS
BSS
SGSN
GSN
Um
Gn
relay
RLC
LLC
Gb
IP
UDP
SM
BSSGP
RLC
IP
G
SMS
UDP
GSN
GTP
GMM = GPRS mobility Management (similar to MM in GSM circuit)
SM = Session Management (similar to CM in GSM Circuit)
GSMS = GPRS Short Message Service
For GPRS TRAFFIC, the BSS is only used for LLC frame relay between MS and SGSN.
MAC = Medium Access Control
BSSGP = BSS GPRS Protocol. (Similar to BSSAP)
Functions:
management of cell-SGSN traffic : flow ctrl + de-block+reset, particularly management of the cell update (in the same RA): the BSSGP header always indicates the serving cell . Therefore if MS is ready and it is a new cell, then SGSN stores this new cell and send back to it (DL) all the non-acknowledged LLC_PDU.
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(simple case:
(able to be paged)
4
MS
BSS
SGSN
HLR
GGSN
In order to access the GPRS service, an MS shall first makes its presence known to the network by performing a GPRS attach. This operation establishes a logical link between the MS and the SGSN and makes the MS available for:
notification of incoming GPRS data
paging via SGSN
Short Message Service (SMS) over GPRS
(Next Page:) In order to send and receive GPRS data, the MS shall activate the packet data address that it wants to use. This operation makes the MS known in the corresponding GGSN, and interworking with external data networks can commence.
Attach procedure:
(1) request (*)
(2) security procedure (if needed)
(3) HLR informed by SGSN (if new SGSN since detach or very 1st attach)
(4) location update procedure (LA in VLR’s)
(if GPRS Attach while already IMSI attached or Combined GPRS / IMSI attached)
(5) attach accept (with temporary identification if a new one is allocated)
(6) attach complete (if new temporary identification)
(*) Attach type = - GPRS attach only
- GPRS Attach while already IMSI attached
- Combined GPRS / IMSI attached
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5.4.9 Level 3 GSM procedures: PDP Context Activation in GPRS
Send Routing Info
MS
request
GGSN
request
MS
BSS
SGSN
HLR
GGSN
A GPRS subscription contains the subscription of 1 or more PDP addresses (PDP: Packet Data Protocol). Each PDP address is described by an individual PDP context in the MS, the SGSN, and the GGSN. Every PDP context exists independently in 1 or 2 PDP states. The PDP state indicates whether the PDP address is activated for data transfer or not.
The PDP context activation, modification or deactivation functions are only meaningful at the NSS level and in the MS and do not directly involve the BSS.
The PDP context activation can be initiated :
by the MS
by the GGSN
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Update PDP Context Request
(3) Security functions (if needed)
(4) Updating PDP context in GGSN
(5) Location Updating in HLR (SGSN Id)
(6) RA updating accepted by new SGSN
(7) Temporary Identification accepted by MS
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6.1 Base Station Sub-System
Continuous improvement in design with backward compatibility:
Standard version (1998)
3x2 indoor MINI cabinet
Evolution Step 2 (2000)
EDGE/GPRS/GSM new standard TRX
Multistandard BTS (2002)
UMTS TRX plug-in
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Single-antenna or low-loss version
Options
Integrated antenna
VSWR detector
Site Support Cabinet for Battery Backup Unit (up to 270 minutes
for 2 TRX) and transmission equipment (HDSL, Microwave, NTL).
EVOLIUM Micro Base Transceiver Station
Radio performance:
GSM 900 and GSM 1800 variants (E-GSM in second step)
Dualband configurations and now in B6: Dualband cell (or sector)
Two Tx power versions:
low-loss: 36.5 dBm (no internal WBC)
107 dBm Rx sensitivity at antenna connector
Integrated duplexer (standard)
Mechanical/ environmental
same entity to be used as master or slave unit
flexible extension up to 6 TRX
Wall/pole, indoor/outdoor mounting
Compact & aesthetic design:
BTS unit itself: 26 liters/ 20 kg per 2 TRX
complete installation (including COBO, cover, ...): 54 liters/ 32.5 kg per 2 TRX
Maximum. +45 °C with convect. cooling; maximum. +55 °C with optional fan
Optional Site Support Cabinet:
battery backup unit (270 mn for 2 TRX, 180 for 4 TRX, 90 for 6 TRX)
Transmission (HDSL = High rate Digital Subscriber Line NTL = Network Termination Line)
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Small configurations in 1 BSC cabinet (32 or 128 TRXs)
Medium configurations in 2 BSC cabinets (192 or 288 TRXs)
Large configurations in 3 BSC cabinets (352 up to 448 TRXs)
with release B7: 4 BSC cabinets (up to 512 TRXs)
Scalability
6 BSC configurations from 32 TRXs up to 448 TRXs
On-line extension possible to minimise
network impact
Up to 264 cells or 255 BTSs in the largest configuration
EVOLIUM Base Station Controller
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Up to 22 EVOLIUM™ BSC’s per EVOLIUM™ MFS
Up to 8 PCM lines towards each BSC
Up to 240 simultaneously active radio
channels (PDCH) per BSC
GPU hardware prepared for
CS-2 raw data rate
(future release)
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6.3 GPRS
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6.3 GPRS
SGSN P-VLR
(Alcatel 1000)
Low Level Packet Handler : NS BSSGP
O&M / Accounting
SGSN Craft terminal
O&M : Compaq WS
SGSN Server (Orange): Digital Unix Servers
Router (Green): CISCO 7200 routers
Ethernet LAN: 3COM
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6.3 GPRS
Nominal Capacity with Alcatel Traffic Model
Up to 100 000 dynamic MM contexts (MS attached)
Up to 90 000 activated PDP contexts
SGSN
Each providing up to 16 Frame Relay links at 2Mbit/s
Gn interfaces (Towards GGSN)
Each SGSN Datacom router provides up to 5 physical slots
ATM, Ethernet, Fast Ethernet, ISDN, WAN E1 interfaces, ...
Gr interfaces (Towards HLR)
Up to 8 Number 7 channels on 4 physical 2Mbit/s interfaces
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6.3 GPRS
GGSN
All functions handled by a standard router (Cisco 7200 routers) with a specific software
Up to 90000 simultaneously active PDP contexts per GGSN (7206 VXR)
Switching Capacity: 25000 packet/s (for 256 Bytes packets) 50 Mbit/s
Physical interfaces
6 physical slots to be shared between Gn and Gi
ATM, Ethernet, Fast Ethernet, ISDN, WAN E1 interfaces, ...
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6.3 GPRS
Charging Gateway
Billing System
Hot Billing System
The Charging Gateway is a Stand-Alone Product which can be integrated in any fixed Network or Mobile Network:
The Alcatel Call Detail Record Collector (CDRC) is based on ALMA 1338
already used for GSM CDR
Reliable real-time collection of :
Aggregation of partial CDR
Mediation towards CCBS / OSS :
CDR hot billing transfer (R2)
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6.4 Operation and Maintenance
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6.7 Overall Infrastructure (GPRS)
Returns several IP @ per APN in Round-Robin or fixed mode
Ensures resilience and load-sharing
DHCP Server: Dynamic Host Configuration Protocol
Used to allocate Dynamic IP addresses to MSs in the transparent mode in case the PLMN operator is also an ISP
Border Gateway
Tunnelling over Internet
Leased lines
Contains routing information used to transfer packets between home GPRS network and visited GPRS network
Provides the appropriate security, e.g. "Firewalls"
GPRS Interception Node (GIN)

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GPRS Day 1_start.ppt

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