01 rn20021en20gla0 (e)gprs functionality

8/13/2019 01 Rn20021en20gla0 (e)Gprs Functionality

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(E)GPRS Functionality

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1 © Nokia Siemens Networks RN20021EN20GLA0

EGPRS EXPLAIN





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Module objectives

After completing th is learning element, the participant wi ll be able to:

Theory:

• Describe the (E)GPRS network architecture

• Explain the function of the used protocols Network Protocols

• List the used Physical and Logical Channel




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SW and HW Releases

This material describes the Nokia Siemens Network BSS (E)GPRS System with the

following Software and Hardware releases:

The compatibility of the NE releases for RG20 (BSS) and RG25 (BSS) is as follows:

RG20 (BSS) consists of the releases:

• BSC S15;

• MetroSite CXM8.0; UltraSite CX8.0; Flexi EDGE EX4.0 and BTSplus BRG2.

RG20 (BSS) is supported by the following NE releases:

• NetAct OSS5.2 MP1; MSC M15 and SGSN SG8.

RG25 (BSS) consists of the releases:

• BSC S15 EPx.0;

• MetroSite CXM8.1; UltraSite CX8.1; Flexi EDGE EX4.1; Flexi EX4.1 and BTSplus

BRG2.1.

RG25 (BSS) is supported by the following NE releases:

• NetAct OSS5.3 CD Set 1; MSC M15 and SGSN SG8.

The BSCi / BSC2i and TCSM2 and Talk Family BTS systems are compatible (supported)

by the RG25 (BSS) Release. The new RG25 (BSS) features are not supported by the

Transcoder TCSM2 and Talk Family BTSs.




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Functionality - Content

Introduction

• Network Architecture and Interfaces• Network Protocols

• Multiframe and Header Structure

• Air Interface Mapping – Physical and Logical Channel




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GSM & (E)GPRS Network Architecture

BTSMS

BSC+PCU

HLR

AuC

EIR

PSTN

Base Station Subsystem

Network Switching Subsystem

Air A-bis A-ter

BTS

MSC/VLR

TC

A

SGSN

Gb

GGSNInternet

Gr

Gn

Gs

AuC – Authentication Centre

BSC – Base Station Controller

BTS – Base Transceiver Station

EIR – Equipment Identity Register

GGSN – Gateway GPRS Support Node

HLR – Home Location Register

MS – Mobile Station

MSC – Mobile Switching Center

PCU – Packet Control Unit

SGSN – Serving GPRS Support Node

TC – Transcoder

VLR – Visitor Location Register

GPRSBackbone

LIG

Border Gateway

Billing

Inter-PLMNnetwork

ChargingGateway




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(E)GPRS Network Elements and Primary Functions

SGSN

• Mobility Management

• Session Management

• MS Authentication• Ciphering

• Interaction with

VLR/HLR

• Charging and statistics

• GTP tunnelling to other

GSNs

GGSN

• GTP tunnelling to

other GSNs

• Secure interfaces

to external

networks

• Charging &

statistics

• IP address

management

Charging Gateway

• CDR consolidation

• Forwarding CDR

information to

billing center

Border Gateway

- Interconnects different

GPRS operator‘s

Backbones

- Enables GPRS roaming

Domain Name Server

• Translates IP host names to IP

addresses

• Makes IP network configuration

easier

• In GPRS backbone SGSN uses

DNS to get GGSN and SGSN IP

addresses

• Two DNS servers in the backbone to

provide redundancy

Legal Interception Gateway

• Enables authorities to intercept

subscriber data and signaling

• Chasing criminal activity

• Operator personnel has very limitedaccess to LI functionality

• LI is required when launching the

GPRS service




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GSM and (E)GPRS Interfaces

Signaling and Data Transfer Interface

Gd, GC and Gs are optiona!l

Gf

D

Gi

Gn

Gb

Gc

CE

Gp

Gs

MSC/VLR

TE MT BSS TEPDN

R Um

Gr A

HLR

Other PLMN

SGSN

GGSN

Gd

SM-SCSMS-GMSC

SMS-IWMSC

GGSN

EIR

SGSN

Gn

Signaling Interface

Gs and Gc are optional, Gc is normally not implemented.

SMS over GPRS is option as well




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(E)GPRS Protocol Architecture

L1

L2

IP

UDP

USER

PAYLOAD

GTP

GGSN

L1

L2

IP

(E)GPRS Bearer

GGSN

Relay

IP

GPRS IP Backbone

L1

L2

IP

GTP

NW Services

L1bis

BSSGP

SNDCP

LLC UDP

SGSN

Relay

Gn

Internet

TCP/UDP

L1

L2

IP

APP

Gi

TCP/UDP

LLC

SNDCP

IP

APP

RLC

MAC

GSM RF

MS

RLC

MAC

GSM RF

NW Services

BSSGP

L1bis

BSS

Um Gb

FIXED HOST

Relay

(E)GPRS defines a protocol architecture which

allows to transfer IP version 4 or 6 packets from

application servers (Host) to Mobile Stations.




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SNDCP (Subnetwork Dependent ConvergenceProtocol) Layer

The SNDCP layer works between MS and SGSN.

Main functions:

- Multiplexer/demultiplexer for different datastreams onto one LLC layer

- Option to (de-)compress protocol control information (e.g. TCP/IP header)

- Option to (de-)compress data (whole IP packet)

- Segmentation/de-segmentation of data to/from LLC layer

- Buffering of data fragments in case of LLC acknowledged transfer mode

LLC

SNDCP

IP

TCP/UDP

APP

RLC

MAC

GSM RF




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Logical Link Control (LLC) Layer

LLC

SNDCP

IP

TCP/UDP

APP

RLC

MAC

GSM RF

The LLC layer works between MS and SGSN:

Main functions:

• Provision of acknowledged or unacknowledged transfer mode between

SGSN and MS

• Independent of underlying radio interface protocols

• transfer of signalling (GMM, SM or SMS) and SNDCP packets (user data).

• Ciphering/deciphering of signalling and user data

Control Address FCSInformation

1 1-3 1-1520 3 Octets

LLC Frame




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Radio Link Control (RLC)/ Medium Access Control(MAC) Layers

RLC

- Provides Acknowledged or Unacknowledged data transfer on airinterface

- Segmentation/de-segmentation of data from/to LLC layer

MAC

- Control of MS access to common air-interface medium

- Flagging of PDTCH/PACCH occupancy

RLC/MAC Protocols works between the MS and PCU.

LLC

SNDCP

IP

TCP/UDP

APP

RLC

MAC

GSM RF




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GSM RF Layer

The RF layer works between the MS and BTS

and can be splitt into

- Physical Link sublayer (see above)

- Physical RF sublayer (Modulation)

LLC

SNDCP

IP

TCP/UDP

APP

RLC

MAC

GSM RF

Functions of the Physical Link sublayer:

- Framing: Placement of data into bursts, frames, radio blocks, etc.

-Data (de)coding for maximising the data throughpu

- Coding Scheme CS1 to 4 for GPRS

- Modulation and Coding Scheme MCS 1 to 9 for EGPRS

- Detection and correction of errors

- Procedures for detecting congestion on the air interface

- Procedures for synchronising MS and network

- Procedures for monitoring and evaluation the radio link quality

- Procedures for cell (re-)selection

- Transmitter power control (implemented only in UL)

Phy. Link

Phy. RF

tailbits

3

encrypted bits57

SB1

trainingsequence

26

SB1

encrypted bits57

tailbits

3

guardperiod

8,25 bits

Normal burst




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(E)GPRS Protocol ArchitectureMapping to RF layer

SNDCP PDU (SN-PDU)

LLC-PDU

RLC Block

MAC Block

Network PDU (NPDU) e.g. IP-packet

LLC-PDU

RLC Block

Burst Burst Burst Burst

channel coding

LLC

SNDCP

IP

RLC

MAC

GSM RF




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Bursts on the Air Interface –Mapping RLC blocks

1 TDMA frame = 4.615 ms

= BURST PERIOD

RLC/MAC Blocks

TDMA Bursts

RLC Blocks

4 x TDMA Frames = 4 Bursts = 1 Radio block

0 7 0 7 0 70 7

12 x RLC/MAC Blocks = 1 x 52 PDCH MultiFrame = 240 ms

12 Radio Blocks / 0.240 s = 50 RLC/MAC Blocks / s

0 1 2 3 4 5 6 7 8 9 1

0

1

1

1

2

1

3

1

4

1

5

1

6

1

7

1

8

1

9

2

0

2

1

2

2

2

3

2

4

2

5

2

6

2

7

2

8

2

9

3

0

3

1

3

2

3

3

3

4

3

5

3

6

3

7

3

8

3

9

4

0

4

1

4

2

4

3

4

4

4

5

4

6

4

7

4

8

4

9

5

0

5

1

B0(0..3) B1(4..7) B2 (8..11)

P

TCCH

B3(13..16) B4(17..20) B5(21..24)

I

DLE

B6(26..29) B7(30..33) B8(34..37)

P

TCCH

B9(39..42) B10(43..46) B11(47..50)

I

DLE




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GSM and (E)GPRS Multiframe

TS 6

GSM Signalling

GSM Traffic

(E)GPRS traffic

TDMA frameTS 0 TS 1 TS 2 TS 3 TS 4 TS 5 TS 7

Radio Block 0

Radio block 1

Radio Block 2

Radio Block 3

Radio Block 4

Radio Block 5

Radio Block 6

Radio Block 7

Radio Block 8

Radio Block 9

Radio Block 10

Radio Block 11

FCCHSCH

FCCHSCH

FCCHSCH

FCCHSCH

FCCHSCH

IDLE

PCH+

AGCH

PCH+

AGCH

BCCH

PCH+

AGCH

PCH+

AGCH

PCH+

AGCH

PTCCH

PTCCH

IDLE

IDLE

0123456789

101112131415161718192021222324252627282930313233343536373839

404142434445464748495051

SACCH

IDLE

TCH

TCH

TCH

TCH

TCH

TCH51 TDMA

Multiframe

26 TDMA

Multiframe

52 TDMA

Multiframe




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(E)GPRS Logical Channels

GPRS introduces several new logical channels to the GSM air interface. There are

no dedicated signalling channels as in GSM. The PDCH are used for data and

signalling.Packet data traffic channel (PDTCH) is reserved for GPRS packet data transfer. A

PDTCH corresponds to the resource allocated to a single MS on one physical

channel for user data transmission. In multislot operation, one MS may use multiple

PDTCHs in parallel for individual packet transfer. PDTCH are uni-directional as

opposed to TCH in GSM.

Packet associated control channel (PACCH) (bi-directional) is a signalling

channel dedicated for a certain MS. The signalling information could include

acknowledgements, power control, resource assignments, or reassignment

messages

Packet timing advance control channel (PTCCH) is used in uplink direction for

the transmission of random access bursts to estimate the timing advance for one

mobile. In the downlink direction one PTCCH is used to transmit timing advance

information to several MSs. PTCCH information is transmitted in positions 12 and 38

of the 52-multiframe structure.

For initiating the data transfer existing GSM Common Channels are used. PBCCH

(Packet Broadcast Control Channel) and associated GPRS common channels are

not supported.


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(E)GPRS Logical Channels

GPRS Air Interface Logical Channels

CCCHCommon Control Channels

DCHDedicated Channels

PCHPaging CH

AGCH Access Grant CH

RACHRandom Access CH

Existing GSM Signaling Channels(Shared with GPRS Signaling)

PACCHPacket Associated

Control CHPDTCH

Packet Data TCH

GPRS Signaling and

Data Channels

PTCCH UL/DLPacket Timing

Advance Control CH

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