GPRS Ingo Wendler (sunrise)

© Sunrise 12.04.23

GSM Data evolution

EDGE

GSM HSCSD services upto 38.4 kbit/s (later up to 64 kbit/s)

PDS services low bit rates

GSM GPRS services upto 160 kbit/s

UMTS

GSM CS data services upto 9.6 kbit/s

91/92 98 99/00 02

Functionality

© Sunrise 12.04.23

GPRS evolution towards 3rd Generation

HSCSD “High Speed Circuit Switched Data”1st step in GSM Phase 2+ that clearly increase achievable data Rates in the GSM System 14.4kbps Channel Coding =115.2kbps for 8 Tsl Maximum data rate is limited to 64kbps due to CN a A-Interface limitationPrecondition:Modify GSM Network to support HSCSD in BSC & MSCHandsets has to support Multislot Capabilities Today HSCSD (Data Cards)Handsets support 4 Tsl in Downlink and up to 2 Tsl in Uplink Direction

© Sunrise 12.04.23


Depending on the Cell Configuration amount of Users is restricted Multiple User cannot share a Tsl at the Air InterfaceDepending on the Bearer Nature “Circuit Switched” a Tsl is dedicated to a SubscriberAmount of Subscriber per Tsl is limited to 1Circuit Switched Data has a long access time Call Charging is based on connection time

© Sunrise 12.04.23


GPRS “General packet Radio System”

Connections do not reserve resources permanently, which is Highly efficient for applications with a bursty natureShort access time to the NetworkCharging model can be based on transmitted volume GPRS brings packet switched bearer services to the existing GSM SystemUser can Access Public Data Network directly using their Standard protocol addresses (IP, X.25)GPRS Mobile can use between 1-8 channels over the air interface depending on the MS capabilities

© Sunrise 12.04.23


Resource allocation is dynamic and dependent on demand and Resource Availability Packets can be sent on idle time between speech call depending MS class typesPossible traffic types point to point point to multipoint (postponed to Release 4&5) SMS capability Anonymous access (planned)Maximum Theoretical throughput per MS using 8 Tsl without Error Correction is 160kbps

© Sunrise 12.04.23

GPRS Logical Architecture

Gf

Gi

Gn

Gb

GcD

CE

Gp

Gs

Signaling and Data Transfer Interface

Signaling Interface

MSC/VLR

TE MT BSS TEPDN

R Um

GrA

HLR

Other PLMN

SGSN

GGSN

Gd

SM-SCSMS-GMSC

SMS-IWMSC

GGSN

EIR

© Sunrise 12.04.23

GPRS Logical Architecture

BSC

GMSCMSC/VLR

SGSN

PTM-SC

EIR

HLR

AUC

GGSNIP-Backbone Network

ExternalIP Network

External X.25 Network

Gs

Gf

Gr

Traffic & Signaling

Signaling

BTS - Base Transceiver StationBSC - Base Station ControllerMSC - Mobile Switching CentreHLR - Home Location RegisterSGSN - Serving GPRS Support NodeGGSN - Gateway GPRS Support NodePTM-SC - Point-to-Multipoint Service Centre

Notebook & GPRS mobile

BTS

Gb

ExternalIP Network

Um

ISDN/PSTN

Gn

Gi

© Sunrise 12.04.23

GPRS Network Node Functionality

• SGSN and GGSN are IP based packet switching nodes

• SGSN supports basic mobility management, session management, subscription checking, charging

• GGSN supports session management, charging and provides interconnect points to ISPs (Internet Service Provider)

• BSC (PCU) supports the Radio Link- and MediumAccess Control protocol (RLC/MAC)

• BTS supports new channel coding and interleaving

• HLR supports subscriber data management

© Sunrise 12.04.23

GPRS Mobiles

• Class A: Simultaneous usage of Circuit- and Packet switched services (2 TRX=Dual Transfer Mode DTM is precondition).

• Class B: Automatic choice of service, Circuit- or Packet switched, but only one at a time (1 TRX). Suspension/resumption of GPRS services at setup/release of CS connection.

• Class C: Manually selected use of either Circuit- or Packet switched service. Special case is a packet only MS (1TRX).

• Class A: Simultaneous usage of Circuit- and Packet switched services (2 TRX=Dual Transfer Mode DTM is precondition).

• Class B: Automatic choice of service, Circuit- or Packet switched, but only one at a time (1 TRX). Suspension/resumption of GPRS services at setup/release of CS connection.

• Class C: Manually selected use of either Circuit- or Packet switched service. Special case is a packet only MS (1TRX).

© Sunrise 12.04.23

GPRS Mobile Station “Multislot Classes”

Class Download Upload Max.slots1 1 1 2

2 2 1 33 2 2 34 3 1 45 2 2 46 3 2 47 3 3 58 4 1 59 3 2 510 4 2 511 4 3 512 4 4 513 3 3 unlimited14 4 4 unlimited15 5 5 unlimited16 6 6 unlimited17 7 7 unlimited18 8 8 unlimited19 6 2 unlimited20 6 3 unlimited21 6 4 unlimited22 6 4 unlimited23 6 6 unlimited24 8 2 unlimited25 8 3 unlimited26 8 4 unlimited27 8 4 unlimited28 8 6 unlimited29 8 8 unlimited

© Sunrise 12.04.23

GPRS Transmission Plan

GSM RF

MAC

RLC

LLC

SNDCP

IP / X.25 IP / X.25

GTP

L1

L2

Application

GSM RF

FrameRelay

MAC

RLC BSSGP

L1bis

BSSGPFrameRelay

LLC

SNDCP GTP

L1bis L1

L2

IP

MS BSS (PCU) SGSN GGSNUm GnGb Gi

IP

UDP/TCP

UDP/TCP

© Sunrise 12.04.23

GPRS Routing <->Transmission Plane

© Sunrise 12.04.23

GPRS Handset IP Address Assignment

Mobile User connects to specified APNAPN is configured in the GGSNKinds of Handset IP address assignment

GGSN pool per APN Subscriber IP Address assignmentexternal DHCP ServerIntranet DHCP ServerFixed IP Address Assignment in the HLR per Subscriber and APN (not or!!)

© Sunrise 12.04.23

GPRS Routing and Address Plan

IPv4 ‣used In GPRS Backbone (public & private)

‣used for Handsets (public & private)

IPv6 ‣Backbone can support with Release 99

implementation

‣current used GPRS capable Handsets

does not support IPv6

‣1st steps visible for UMTS Handsets only

© Sunrise 12.04.23


Further necessary Routing Instrument for GPRS

TLLI=Temporary Logical Link ID

Routing AreaLocation Area

© Sunrise 12.04.23


BVCI /LA/RA

Handset IP

GTP Address

Tunnel ID =IMSI

Handset IP

TLLI

Gb Interface Gn InterfaceSGSN<->BSC SGSN<->GGSN

© Sunrise 12.04.23

Avoid Collision at the Air Interface

Data Transmission divided in to Up- and Downlink Data Traffic

USF0 USF1 USF2 USF3 USF4 USF5 USF06USF7Free

Uplink

TFI0 TFI1 TFI2 TFI3 TFI4 TFI5 TFI6 TFI7 TFI8

Uplink

Downlink

© Sunrise 12.04.23

GPRS Multiplexing at RLC/MAC Layer

SDCCH&SACCH CS CS CSCS CS PSBCCH

CCCH

USF0

USF1

USF2

USF3

USF4

USF5

USF6

USF7

TFI0

TFI1

TFI2

TFI3

TFI4

TFI5

TFI6

TFI7TFI8

Uplink

© Sunrise 12.04.23

GPRS Coding Schemes based on RLC/MAC

Coding Rate Info (bits)

CRC (bits)

Abis unchanged

Data rate (kbps)

R=1/2 (SDCCH)

184 40 yes 9.05

R=2/3 272 16 yes 13.4

R=3/4 320 16 no 15.6

R=1 440 16 no 21.4

Coding Rate Info (bits)

CRC (bits)

Abis unchanged

Data rate (kbps)

R=1/2 (SDCCH)

184 40 yes 9.05

R=2/3 272 16 yes 13.4

R=3/4 320 16 no 15.6

R=1 440 16 no 21.4

© Sunrise 12.04.23

GPRS Quality of Service Profile

1) Delay for packets of 128 octets; • Delay class 1 (mean 0.5 sec, 95% < 1.5 sec)

• Delay class 2 (mean 5 sec, 95% < 25 sec)

• Delay class 3 (mean 50 sec, 95% < 250 sec)

• Delay class 4 (unpredicted)

2) Reliability

• Reliable data transfer (retransmission, delay)

• Unreliable data transfer (no retrans., small delay)

• Unreliable data transfer, erroneous data discarded (no retrans., small delay, data loss)

© Sunrise 12.04.23

GPRS Quality of Service Profile

3) Priority

Priority class 1 (highest priority)

• Priority class 2• Priority class 3• Priority class 4 (lowest priority)•

4) Mean and 5) Peak throughput

© Sunrise 12.04.23

GPRS Roaming using IPSEC Tunnel via Internet

Operator A Operator B

Internet IPsec Tunnel via the Internet

© Sunrise 12.04.23

GPRS Roaming using GRX

BTS MS

Operator A. GPRS Backbone as HOME OPERATOR

SGSN

GGSN

BSC

Border GW

BTS

MS

Operator B. GPRS Backbone as VISITED OPERATOR

SGSN GGSN

BSC

Border GW

Inter PLMN Backbone Service network

Public Internet

DNS DNS

Charcing GW Charging GW

Public Internet

Public Internet Public Internet

Root DNS Info Base

© Sunrise 12.04.23

further Steps

Packet Handling (PBCCH/PCCCH)QoS Negotiation (Air <->GGSN)Increasing USF GranularityIPv6Network Mode Changes to decrease MS signallingMS with higher Multislot CapabilitiesExtended MAC Modes

Technology EDGE GPRS with 8PSK modulationUMTS

GPRS Ingo Wendler (sunrise)

Technology

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