GPRS Understanding

8/9/2019 GPRS Understanding

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GPRS/ EDGE

© 2005 H. H’mimy Lecture 7, Slide 1SMU EE 8315 Advanced Topics in Wireless Communications - Spring’05

Southern Methodist University

EETS 8315 / TC752-N

Advanced Topics in Wireless Communications

Spring 2005

http://engr.smu.edu/eets/8315

Lecture 6: GPRS/ EDGE

Instructor: Dr. Hossam H’mimy, Ericsson Inc.

[email protected](972) 583-0155

GPRS/ EDGE

© 2005 H. H’mim Lecture 7 Slide 2SMU EE 8315 Advanced To ics in Wireless Communications - S rin ’05

Announcement


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GPRS/ EDGE


Course Outline…

• Lecture 1

• Lecture 2

• Lecture 3

• Lecture 4• Lecture 5

• Lecture 6

• Lecture 7

• Lecture 8

• Lecture 9

• Lecture 10

1/24

1/31

2/1

2/72/21

2/28

3/7

3/14

3/21

3/28

Introduction & overview

IMT2000

Traffic & simulation

Mobile IP, CDPDCSD, SMS, MMS

GPRS EDGE :RN/CN, (Abstract Due)

UMTS

Exam

UMTS (WCDMA) RN & CN

WCDMA Design

GPRS/ EDGE


Outline

• Introduction

• GPRS Reference Model

• GPRS Core Network

• Protocol stack• Air Interface ( logical/physical channels)

• Network operating Modes and paging

• Terminal Classes

• UL/DL data transfer

• Mobility Management

• EDGE air interface


3/52

GPRS/ EDGE


GPRS Reference Model

Gb

FR over T1

SGSN

GGSN

SMSC

GGSNBSC

EIR

HLR

SGSN

MSC/VLR

RBSMS

SS7 over T1

Gc

Gd

Gs Gr

Gp

Gn

Gn

IP over ATM/

Ethernet /FR

Gi PDN

TE

GPRS/ EDGE


GPRS Interfaces

Interface Between Entities Technology Physical

Gb SGSN and BSC FR T1

Gd SGSN and SMS SS7 T1

Gi GGSN and PDN IP fiber

Gn/Gp GSNs within/inter- PLMN IP Ethernet,T1, fiber

Gr /Gc SGSN/GGSN and HLR SS7 T1

Gs SGSN and MSC/VLR SS7 T1


4/52

GPRS/ EDGE


GSM and GPRS Net

IP

A

HLR

AUC

SOG

MAP

Gs

Gd

SGSN

GGSN

BGW

GPRS

Backbone

Gn

Gb

Gi

Gr

Gn

BTS

BSC

A’

MSC/

VLR

SMS-GMSC/ SMS-IWMSC

GPRS/ EDGE


GPRS Gore Network

• New Packet Switched Core network

• Nodes

– SGSN – GGSN

• IP mobility via …..


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GPRS/ EDGE


GSN: GPRS Support Nodes

• SGSN

– (Server and Router)

– Routing built in routers (dynamic and static)

– Security (unlike GSM , ciphering is terminated at SGSN

– Auth. Has VLR functionality, register attached users

– Mobility management: routing area update, HO sessions

between BSCs, make sure packets are tunneled to correct

GGSN

– Charging: Call detail records CDR), based on IP payload and

session duration.

– SMS: supports interface to SMS-GMSC & SMS-IWMSC

– Session management: negotiate QoS parameters with MS

GPRS/ EDGE


GSN: GPRS Support Nodes..

• GGSN

– Gateway

– Has SGSN capabilities

– Mobility management : make sure that packets are tunneledto correct SGSN

– Firewall

– Border gateway (external nets) has radius client for external

authentication.


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7/52

GPRS/ EDGE


Protocols

• SNDCP Subnet dependent convergence

protocol:

– Network layer protocol

– MUX network layer users’ data into one logical message, – encryption,

– Data compression V.42bis algorithm

– TCP/IP header compression is supported.

– segmentation of Network PDU into LLC frames,

– interface between network layer and LLC

– It supports IP, X.25 network layer protocols

– Services PTP, PTM-M, PTM-G.

GPRS/ EDGE


Protocols

• GTP : GPRS tunneling protocol – Data Link Control protocol on logical link level

– In GSNs on the Gn interface.

– Transported on TCP/UDP

• BSSGP: BSS GPRS protocol, – Data Link Control protocol on Radio link level

– In SGSN on Gb interface

– message format

– procedures for transfer of paging and data ,

– link management


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GPRS/ EDGE


Protocols

• LLC: Logical Link Control:

– higher sublayer of data link control

– reliable logical link between MS and SGSN

– LLC frames are variable with temporary ID max 1600Bytes – TX ACK/NAK frames,

– Error detection and ARQ of Frames

– Logical link is valid within one SGSN

• RLC Radio Link Control

– Medium sublayer of data link control

– Detect corrupt radio blocks and request selective ARQ

GPRS/ EDGE


Protocols

• MAC: Medium Access Control

– Lower sublayer of Data link control

– Physical channel allocation

– Channel sharing using modified Slotted Aloha with

reservation ( is MAC for UL or DL or both???)

• Phy. Physical layer

– CRC, Channel coding, interleaving

– Modulation...

• L2 on SGSN/GSN can be ethernet, ATM or ISDN


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GPRS/ EDGE


PCU

• Packet Control Unit

– Mediator between MS (BSS) and SGSN

– PDCHs are allocated to PCU

– Assign channels to different MS

– Responsible for RLC and MAC, BSSGP

– Terminates the Gb interface

GPRS/ EDGE


GPRS Protocols

User dataPH

FH FCSInfo

segment segment

segment segment

FH BCSdata

Physical

RLC/MAC

LLC

SNDCP

Application/ Net

Burst

20 m sec

Burst Burst Burst114bits

Encoding and puncture456bits

RLC dataPC BCSRLC Header TUSF

MAC Header

Payload

228 Bits


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GPRS/ EDGE


GPRS Protocols

User dataPH

segment segment

InfoFH FSC

segment segment

dataFH BCS

Encoding and puncture

Burst

20 m sec

Burst Burst Burst

Physical

RLC/MAC

LLC

SNDCP

Application/Net• Packet flow

– SNDCP: subnet

dependent convergence

protocol

– PH: Packet header

– FH: Frame header

– FCS: frame check

sequence

– BCS: Block Check

sequence114bits

456bits

GPRS/ EDGE


GPRS ….

• Air interface

– 12 Radio blocks on a 52 multiframe over 240msec

– Radio block is 20msec, 4 Frames

– Number of Radio Blocks is 50 Blocks /sec

– Frame length is 4.6 msec


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GPRS/ EDGE


Radio Access (Air Interface) GSM

• 26 Multi-frame structure for TCH/FR

=3 Radio blocks x 4 frames + 1 Idle frame + 1 SACCH frame

3 157 1 35726 8.25

T Coded Data S T.Seq. S Coded Data T GP

Burst

Frame

Radio Block

SACCH

Idle

576.92 µ sec

TS0 TS7

B0 B0B5 B5

26 Multi-frame TCH/FR

GPRS/ EDGE


Radio Access (Air Interface)

• 52 Multi-frame structure for PDCH

=12 Radio blocks x 4 frames + 2 Idle frames + 2 PTCCH frames

3 157 1 35726 8.25

T Coded Data S T.Seq. S Coded Data T GP

Burst

Frame

Radio Block

PTCCH

Idle

576.92 µ sec

B0 B12

TS0 TS7


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GPRS/ EDGE



Scheme Code rate USF Pre-coded

USF

Radio

Block

excl. USF

and BCS

BCS Tail Coded

bits

Punctured

bits

Data rate

kb/s

CS-1 1/2 3 3 181 40 4 456 0 9.05

CS-2 ≈2/3 3 6 268 16 4 588 132 13.4

CS-3 ≈3/4 3 6 312 16 4 676 220 15.6

CS-4 1 3 12 428 16 - 456 - 21.4

Add

BCS

Add

USF

Add

TCoding

1/2Puncture

8kbps

12 kbps

14.4kbps20kbps

GPRS/ EDGE


Puncturing

Conv.Coding

1 0 0 1 101 101 011 001

Output 1 P1= 01 01 11 01

Output 2 P2= 10 10 01 00

Puncture 1

Puncture 2


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GPRS/ EDGE


CS-1 symbol = 1 bits

USF

3bits

MAC H

(5bits)

FBI+ data(20 octets=160bit) + spare (0)

(160 bits)

Pre-code3

181 bits TB4

6 42P1

408

Total bits= 456= 456 symbol I.e. 114 symbols per PDCH

FBI: final bit indicator. It is in the RLC header.

Coding 1/2

BCS40

RLC H

(16 bits)

GPRS/ EDGE


CS-2 symbol = 1 bits

USF

3bits

MAC H

(5bits)

FBI+ data(30 octets=240bit) + spare (7)

(247 bits)

Pre-code

6 268 bits

TB

4

12 42P1

402

Total bits= 456= 456 symbol I.e. 114 symbols per PDCH

Coding 1/2

BCS

16

RLC H

(16 bits)


14/52


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GPRS/ EDGE


Radio Access (Air Interface) GSM

• GSM logical channel – CCCH common control

– RACH UL Random Access (requests)

– PCH DL Paging

– AGCH DL Access grant ( info on dedic and time adv. – DCCH Dedicated Control

– SACCH (DL system info, time adv., UL MAHO)

– FACCH Info as SDCCH HO

– SDCCH stand alone signaling

– BCH Broadcast

– BCCH DL system parameters

– FCCH DL freq. correction

– SCH DL synch – TCH Traffic

GPRS/ EDGE


Radio Access (Air Interface) GPRS

• Packet data logical channel

– PCCCH common control

– PRACH UL Random Access (requests)

– PPCH DL Paging

– PAGCH DL Access grant ( prior to Pkt Tx)

– PNCH DL Notify (PTM-M group of MS) Ph.2.

– PDCCH Dedicated Control

– PACCH Associated (ACK, CS page, PC,.)

– PTCCH/U Time advance

– PTCCH/D Time advance

– PBCCH DL Broadcast ( may use BCCH) – PDTCH Traffic


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GPRS/ EDGE


Radio Access (Air Interface) GPRS

• Mapping Logical Packet data channels into

Physical channel PDCH

– PCCCH mapped on 52 multi-frame

– PRACH UL 1 or more PDCH – PPCH DL 1 or more PDCH

– PAGCH DL 1 or more PDCH

– PNCH DL 1 or more blocks on PCCCH

– PDCCH

– PACCH Dyn. allocated block basis

– PTCCH/U-D 2 defined frames

– PBCCH DL 1 or more PDCH

– PDTCH 1 PDCH. Up to 8 MS per PDCH

GPRS/ EDGE


PDCH Allocation

• PDCH is a time slot (physical)

• Dedicated PDCH

– Allocated/ released by the operator

– up to 8 PDCH can be allocated per cell

• On-demand PDCH

– Temporary Dynamically allocated/ released

– no limit on number of PDCHs

– Load supervision function handles the high load in the cell

– SGSN allocated the PDCHs to the PCU.

• The PCU assign the PDCH to the MS


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GPRS/ EDGE


PDCH Allocation

• PDCH are allocated for GPRS in sets (PSET)

– Max 4 PDCH per PSET

– must be consecutive

– same carrier (RF) ( Hop on the same FH group of RF)

– PDCHs in the same PSET can be dedicated and on-demand

– MS can be assigned PDCH from same PSET

GPRS/ EDGE


PDCH Allocation ...

• GPRS Idle List ( in the BSS)

– It is a list of available recourses (PDCHs) to be used for PS

– Dedicated : Idle list can not be used by GSM

– On-Demand: Idle list can be shared by GSM

GSM

Idle List

On-Demand

GPRS

Idle List

Dedicated

GPRSIdle List


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GPRS/ EDGE


PDCH Allocation ...

• CS calls (GSM)

– check available channels in GSM Idle list

GSM

Idle List

On-Demand

GPRS

Idle List

Check GSM

Idle List

Any

TCH

Check

on-demandIdle List

Any

PDCH

no active

TBF

Assign

TCHChange

to TCH

Pre-empty

PDCH E n d c a l l g o t o I d l e l i s t

GSM

GPRSN

NY

Y

GPRS/ EDGE


PDCH Allocation ...

• PS calls (GPRS)

Check GSM

Idle List

Any

TCH

Check GPRS

Allocated List

PDCH

low load

Convert to PDCH

Assign

PDCH

Check

GPRSIdle list

E n d c a l l g o t o I d l e l i s t

GSM

GPRS

N

N

Y

GPRS

Dedicated

PDCH

Y

N

on-demand

Any

PDCH. Dedicated

first

Y

N

Timer

Block


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GPRS/ EDGE


GPRS Modes

On demand Dedicated

- Voice and data - Data only

- Priority for voice - No voice

- Same coverage as

GSM

- Guaranteed Throughput

- Mainly coverage - Capacity

GPRS/ EDGE


Master slave

• MPDCH

– 2 options ( with MPDCH) and (No MPDCH =on demand)

– Decided by operator: MPDCH can be added and removed on air

• No MPDCH

– Uses only BCCH, PCH, RACH, AGCH

– MS specifies the service PS or CS

• With MPDCH

– MS listen to BCCH first to get info on the PBCCH, PPCH

– uses PBCCH, PPCH, PACH – for Access CS uses ACH , PS uses PACH


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GPRS/ EDGE


Network Operation modes

• 3 Network operation modes

– Based on the Gs interface

Mode

I

II

III

CS

PPCH

PCH

PDTCH

PCH

PCH

PCH

GPRS

PPCH

PCH

-

PCH

PPCHPCH

Coordination

Yes

No

No

GPRS/ EDGE


Network Operation modes ...

BSC

MSC/

VLR

SGSN

BSC

MSC/

VLR

SGSN

•combined LA and RA update

•combined paging

•longer sleep periods for MS

•smaller paging load

•MS is only paged within RA

•separate LA and RA update

•MS needs to listen to two types

of paging channels

•MS is paged in Location Area

I

II

&

III


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GPRS/ EDGE


Paging

• For Network operation Mode I , MS class A,B

– CS pages are sent from MSC to SGSN instead of directly to BSC

– SGSN knows where the MS on

– cell level when MS is on READY state. – RA level otherwise

– SGSN sends the page to PCUs with cell or RA info

– PCU sends the page on

– PPCH or PCH

– PACCH if the MS is in packet transfer mode

• For Network operation Mode III, MS class A,B,C

– CS pages are sent from MSC to BSC to MS on PCH

– PS pages are sent from SGSN to PCU to MS on PPCH or PCH

GPRS/ EDGE


Packet transfer between MS and BSS

• There is a physical connection established between the RLC of

MS and BSS only during Packet transfer called TBF.

• There is one TBF for UL and one TBF for DL

• Released if there is no RLC blocks for transmission.

• MS will get an ID for the TBF (TFI) for each direction from the

PCU during attach procedure

• Packet transfer can be ACKed or unACKed

• Which protocol is responsible for the TBF??


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GPRS/ EDGE


TBF

• TBF is Logical connection between MS and PCU in the

BSS

• It is carried over physical PDCH ( changes)+ DS0 on A’

• It is defined by the TFI• TFI changes if the MS changes BSC.

PHY

SNDCP

LLC

RLC

MAC

L1bisPHY

BSSGP

FR

IP

TCP

UDP

Appl.

MS BSS

RLC

MAC

LLC relay

Gb

TBF

GPRS/ EDGE


BSS to SGSN

• SGSN is connected to each cell ( BTS) in the

BSS via a virtual connection.

• The virtual connection is BSSGP VC (BVC)

and it has Id called BVCI

• LCC frames is transferred between SGSN andBSS (PCU) over the BVC

• BVC (s) are carried over the physical FR PVCs

over DS0 on Gb.GTP

PHY

RLC

MAC

L1bis L1bis

LLC

IP

BSSGP

FR

L1

SNDCP

BSS SGSN

L2BSSGP

FR

TCP/

UDP

IP relay

LLC relay

Gb

SGSN

BSC

BTS

BTS

BTS

BVC


23/52

GPRS/ EDGE


MS and SGSN connection

• The MS is attached to net by sending the IMSI and the

NSAPI ( net sever Access Point ID) to the SGSN.

• SGSN authorize and authenticate the MS and Assign it

TLLI ( Temp LL ID)

• The LLC Link is established and stays alive as long as

the MS is connected to the SGSN.

PHY

SNDCP

LLC

RLC

MAC

L1bisPHY

BSSGP

FR

IP

TCPUDP

Appl.

MS BSS

RLC

MAC

LLC relay

TBF

GTP

L1bis

LLC

IP

L1

SNDCP

SGSN

L2BSSGP

FR

TCP/

UDP

Gb

BVC

LLC

PVC

SAPI

GPRS/ EDGE


MS and SGSN connection ...

• TLLI

– Identify the MS on the LLC

• SAPI

– Identify the service access ( IP services) on LLC

• DLCI ( generated from TLLI & SAPI)

– Identify the LCC connection between MS and SGSN

• NSAPI : Identify the Access provider on SNDCP

PHY

SNDCP

LLC

RLC

MAC

L1bisPHY

BSSGP

FR

IP

TCPUDP

Appl.

MS BSS

RLC

MAC

LLC relay

TBF

GTP

L1bis

LLC

IP

L1

SNDCP

SGSN

L2BSSGP

FR

TCP/

UDP

Gb

BVC

LLC

PVC

SAPI


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GPRS/ EDGE


SGSN to GGSN connection

• GTP

– establishing tunnels on PDP activation. Each tunnel has ID (TID) made

of IMSI and NSAPI. I.e. unique tunnel between MS and ISP

GTP

L1bis

LLC

IP

L1 L1

L2

SNDCP

IP

SGSN GGSN

L2BSSGP

FR

IP

GTP

TCP/

UDP

TCP/

UDP

IP relay

Gn

IMSI123

TLLI55

Cell12

NSAPI1

GGSN4.3.2.1

PDPa.b.c

PDPa.b.c

IMSI123

NSAPI1

SGSN4.5.6.1

• MS has IP address “a.b.c”

• MS ID “IMSI”

• LLC frames on LLC with

“TLLI”

• Connected to “NSAPI”

• IP Packets encapsulated in

GTP and sent to GGSN“4.3.2.1”

• Received packets

from “4.5.6.1” is

decapsulated given

the inner IP “a.b.c”

that belongs to MS

IMSI

GPRS/ EDGE


Packet transfer

IMSI

123

TLLI

55

Cell

12

NSAPI

1

GGSN

4.3.2.1

PDP

a.b.c

PDPa.b.c

IMSI123

NSAPI1

SGSN4.5.6.1

SGSN

BSC

BTSBVC

MS

Src. A.b.c

dest. d.e.f PHY

SNDCP

LLC

RLCMAC

L1bisPHY

BSSGPFR

IP

TCP

UDP

Appl.

MS BSS

RLCMAC

LLC relay

TBF

GTP

L1bis

LLCIP

L1

SNDCP

SGSN

L2BSSGP

FR

TCP/

UDP

Gb

BVC

LLC

PVC

SAPI

d.e.f

GGSN

LLC c o n n e c t i o n “ T LLI ”

TBF

P V C . D S 0

A ’ D S 0

P D C H

G T P

I P P a c k e t

T LLI + N S A P I

I P p a c k e t

G I D

T C P / I P

H

4.5.6.1

4.3.2.1

Src. A.b.c

dest. d.e.f

IP


25/52

GPRS/ EDGE


MAC

• Allows MS to share same PDCH on the UL ( up to 8)

• on every DL MAC header there are 3 bits USF (UL

state Flag). It identifies which MS to transmit

• Immediately after the Attach, The MS is given the

TFI

• At TBF the MS is given the list of PDCH ( PSETS) and

an ID for the USF

• MS will always listen to the PDCHs.• MS will transmit on the PDCH that contains its USF

ID.

GPRS/ EDGE


Packet Scheduling on UL

• PCU does scheduling

– reserve PDCH and assign USF to it for the MS

– In next DL RLC block. PCU puts this USF in MAC header

– All MSs on this PDCH (s) listen to the MAC header USF for all

DL RLC Blocks.

– The MS whose USF ID matches the USF starts to transmit.


26/52

GPRS/ EDGE


Packet Scheduling on UL

• Some MS share same PDCH on the UL

A1

A2 A3

B1B2

B3

C1C2

C3

S1

S1

S1

S2

S2S2

S3

S3

S3

S2

DL

USF =

ULB1S1 S1 S3

B2 A1 C1 A2S2 S3 S3 S2

C2 C3 B3 A3S1

GPRS/ EDGE


GPRS Send and receive Packets

• Before Packet transfer, the GPRS must be

attached and ready.

– Attach procedure

– Activation of PDP context

– Packet data Transfer


27/52

GPRS/ EDGE


GPRS Attach Procedure

• Attach procedure

– Initiated by MS ( on ready state)

– MS (IMSI) , class, ciphering key are delivered to net.

– User info updated in SGSN – Location info sent to the new MSC/VLR

– MS is given a TLLI

– PCU gives the MS TFI

• After the attach procedure,the MS is ready for

– SMS transfer

– activate PDP context

– receive PTM-M

GPRS/ EDGE


GPRS attach

BTS BSC

SGSNGGSN

HLRMSC/VLR

IP

Back bone

MS request attache

Authentication

use info into SGSN and MSC

attach procedure completed


28/52

GPRS/ EDGE


PDP

• PDP (packet data protocol) is activated for each

session.

– MS requests the network to activate PDP context with requested

QoS. – Network can request activation of PDP.

– PDP can be activated for fixed and dynamic IP address

– MS can have more than one PDP activated

– PTP and PTM transfer requires activated PDP

– Routing is enabled between SGSN and GGSN

GPRS/ EDGE


GPRS PDP

BTS BSC

SGSNGGSN

HLR

IP

Back bone

MS request PDP

SGSN validates the request

DNS in SGSN gives GGSN’s IP

Logical connection created

GGSN assign Dynamic IP to MSConnect to external net

DNS


29/52

GPRS/ EDGE


GPRS Mobility Management

Idle

Standby

Ready

• Ready for data transfer but not

active

• MM context active ( RA update)

• Receive

– paging for PTP, PTM-G, and CS

– PTM-M data

• Data reception without paging Ready Timer outabnormal RLC

forced to STANDBY

LLC PDU

received

• PLMN selection

• Cell selection

• Re-selection

• Receive PTM-M data

GPRS AttachGPRS

detachSTANDBY Timer out

or cancel location

GPRS/ EDGE


C/I [dB]

B l o c k E r r o

r R a t e

0

10

20

0 5 10 15 20 25 30

CS-1

CS-2

CS-3

CS-4

C/I [dB]

T h r o u g h p u t

p e r c h a n n e l

T[C/I] = ( 1-BLER[C/I] )×Traw

Link/ System Level Simulations


30/52

GPRS/ EDGE


GPRS Simulations

• Performance

ResultsC/I=9dB

CS1--> 40kbps

CS2--> 50kbps

C/I=15dB

CS2-->65kbps

System Throughput Downlink: 8 PDCH

0

20

40

60

80

100

0 5 10 15 20 25 30 35

C/I (dB)

m e a n ( k b i t / s ) CS1 MSC2

CS1 MSC4

CS2 MSC2

CS2 MSC4

CS3 MSC2

CS3 MSC4

CS4 MSC2

CS4 MSC4

GPRS/ EDGE


GPRS Simulations

Performance

• System capacity

• C/I

– mean=15dB – var=3dB

System Throughput downlink: CS 2

0

10

20

30

40

50

60

70

A B C D E F

# User

m e a n ( k b i t / s )

CS 2 - 8 PDCHs

CS 2 - 4 PDCHs

CS 2 - 2 PDCHs

CS 2 - 1 PDCHs

1 3 5 7 9 11 1PDCH2 6 10 14 18 22 2PDCH4 10 16 22 28 34 4PDCH10 20 30 40 50 60 8PDCH


31/52

GPRS/ EDGE


GPRS Simulations

Performance

• User Throughput

C/I

– mean=15dB

– var=3dB

• 4TS DL

WWW Object Throughput downlink: 4 PDCHs

0

5

10

15

20

25

4 10 16 22 28 34

# User

m e a n ( k b i t / s )

CS 1 - MSC 4

CS 2 - MSC 4

CS 1 - MSC 2

CS 2 - MSC 2

GPRS/ EDGE


Reference

• Jian Cai et al, “General Packet Radio Services in GSM,” IEEE

communication Mag. Oct. 1997. Handout # 18

• Ericsson Review “ GPRS”

http://www.ericsson.com/about/publications/review/1999_02/fil

es/1999024.pdf

• http://www.gprsworld.com


32/52

GPRS/ EDGE


Enhanced Data rates for Global Evolution (EDGE)

• EDGE is essentially a TDMA technology with

higher level modulation and coding and

combined timeslots & carriers to meet ITU’s IMT-

2000 requirements for TDMA( IS136) and GSMsystems

• Introduces concept of “Link Adaptation” in

wireless for maximum throughput in variable

radio conditions

• EDGE is a convergence of TDMA( IS 136) and

GSM!

GPRS/ EDGE


Enhanced Data rates for Global Evolution (EDGE)

• EDGE is designed for easy and stepped migration

towards 3G for both TDMA(IS 136) and GSM

• EDGE = EGPRS +ECSD

• Today(2002): some TDMA (IS136) operators have

started to deploy Overlay GSM/GPRS Network ….

Radio Net

GPRS

EDGE (EGPRS)

Core NetGPRS


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GPRS/ EDGE


EDGE

• Release 99

– finished

– ECSD + EGPRS

– Basic functionality (Link Quality, MCS, .. GPRS stack)

• release 00/01 ( R4 &5))

– RT EGPRS

– New protocol Stack

– GERAN

– Enhance system performance (close to UMTS)

– HR on 8PSK,

– wideband vocoder

GPRS/ EDGE


The EDGE Radio Interface

• Carrier Spacing = 200 kHz

• Frame Length = 4.6 ms split into 8 time slots

• Modulation Formats:

– 8-PSK, data channels

– GMSK, robust fall back, control channels

• Interleaving over 4 Frames

• Link Quality Control:

– Optimize Throughput w.r.t. the Radio Quality

– Combination of Link Adaptation and Incremental

Redundancy... – Data rate per Time Slot 8.8 - 59.2 kbps


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GPRS/ EDGE


Radio Access (Air Interface) Classic

• Packet data logical channel

– PCCCH common control

– PRACH UL Random Access (requests)

– PPCH DL Paging – PAGCH DL Access grant ( prior to Pkt Tx)

– PNCH DL Notify (PTM-M group of MS) Ph.2.

– PDCCH Dedicated Control

– PACCH Associated (ACK, CS page, PC,.)

– PTCCH/U Time advance

– PTCCH/D Time advance

– PBCCH DL Broadcast ( may use BCCH)

– PDTCH Traffic

GPRS/ EDGE



• Mapping logical channels to physical channel

– 3 different configurations

– config. (1) for first TS on the first RF carrier

– Config (2 ) for second TS of first carrier of can be on another carrier…

– Config (3), for all the rest of TSs

• In GSM can you have Config. ( 1 or 2) why?...

P

B C C H

P

C C C H

P

D T C H

P

D C C H

P

C C C H

P

D T C H

P

D C C H

P

D T C H

P

D C C H

1 23


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GPRS/ EDGE


MCS-9 symbol = 3 bits

USF

3bits

RLC/MAC Header +HCS

(45 bits)

FBI+data(74 octets=592bit)

+BCS +TB(612 bits)

coding36 Coding 1/3(135) Coding 1/31836

36 124P1

612

SB

8

Total bits= 1392= 464 symbol


+BCS +TB(612 bits)

Coding 1/31836

P1

612

36 124P2

612

SB

8

P2

612

36 124P2

612

SB

8

P2

612

GPRS/ EDGE



USF

3bits

RLC/MAC Header +HCS

(45 bits)


+BCS +TB(564 bits)

coding

36

Coding 1/3

(135)

Coding 1/3

1692

36 124P1

612

SB

8



+BCS +TB(564 bits)

Coding 1/3

1692

P1

612

36 124P2

612

SB

8

P2

612

36 124 P2612

SB8

P2612


36/52

GPRS/ EDGE



USF

3bits

RLC/MAC Header +HCS

(45 bits)


+BCS +TB(468 bits)


36 124P1

612

SB

8



+BCS +TB(468 bits)

Coding 1/31404

P1

612

36 124P2

612

SB

8

P2

612

36 124P2

612

SB

8

P2

612

GPRS/ EDGE



USF

3bits

RLC/MAC Header +HCS

(33 bits)

FBI+ data(74 octets=592bit)+BCS +TB

(612 bits)

coding

36

Coding 1/3

(99 bits)+ 1 padding

Coding 1/3

1836

36 100P1

1248

SB

8

P2

124836 100

SB

8



37/52

GPRS/ EDGE



USF

3bits

RLC/MAC Header +HCS

(33 bits)


(468 bits)

coding36

Coding 1/3(99 bits)+ 1 padding

Coding 1/31404

36 100P1

1248

SB

8

P2

124836 100

SB

8


GPRS/ EDGE



USF

3bits

RLC/MAC Header +HCS

(36 bits)


+BCS +TB(372 bits)

coding

12

Coding 1/3

(108)

Coding 1/3

1116

12 68P1

372

SB

8


12 68P2

372

SB

8

12 68 P2372

SB8


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GPRS/ EDGE



USF

3bits

RLC/MAC Header +HCS

(36 bits)


+BCS +TB(316 bits)


12 68P1

372

SB

8


12 68P2

372

SB

8

12 68P2

372

SB

8

GPRS/ EDGE



USF

3bits

RLC/MAC Header +HCS

(36 bits)


(244 bits)

coding

12

Coding 1/3

108

Coding 1/3

672

12 68P1

372

SB

8

P2

37212 68

SB

8



39/52

GPRS/ EDGE



USF

3bits

RLC/MAC Header +HCS

(36 bits)


(196 bits)

coding12

Coding 1/3108

Coding 1/3588

12 68P1

372

SB

8

P2

37212 68

SB

8


GPRS/ EDGE


GPRS vs GMSK MCSs of EGPRS

MCS Code rate Bit rate/TS

MCS-1 0.53 8.8

MCS-2 0.66 11.2

MCS-3 0.8 14.8

MCS-4 1 17.6

CS Code rate Bit rate

CS1 1/2 9.05

CS2 2/3 13.4

CS3 3/4 15.6

CS4 1 21.4

EGPRS GPRS

B

o t t o m o f M A C

,

n

o U S F , B C S o r T B

Bit rate

8

12

14.4

20

B

o t t o m o f L L C

B

o t t o m o f L L C

Is GPRS a subset of EGPRS??What throughput you are really measuring?

GSM 3.64 GSM 4.6


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GPRS/ EDGE


Link Quality Control

• Why

– path loss, Shadowing and rayligh fading Carrier change

– Bursty packet data lead to bursty interference

– Increase packet throughput

– Link quality control

– Link quality C/I , BER, FER, BLER,..

• Type II Hybrid ARQ ( ARQ with adaptive

Modulation/coding)

GPRS/ EDGE


Link Quality Control

• LA Link Adaptation

– select the MCS that gives a maximum throughput for

certain C/I

• IR (Incremental Redundancy)

– Packet is sent with a certain puncture scheme

– If a packet is received in error, the transmitter will

retransmit the packet with another puncture scheme

– at the end all the packets will be combined ( better

performance)


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GPRS/ EDGE


IR

• RLC block size

MCS-9

Family A MCS-6

MCS-3

MCS-7

Family B MCS-5

MCS-2

MCS-4

Family C MCS-1

22 byte 22 byte

22 byte

28 byte 28 byte 28 byte 28 byte

28 byte 28 byte

28 byte


37 byte 37 byte

37 byte

F i n

d t

h e

R L C

b l o

c k s

i z e

f o r M

C S

8 ?

GPRS/ EDGE


IR

• RLC block size

MCS-9

Family A MCS-6

MCS-3

example

• MCS-9 carries 2 RLC blocks @ 74 byte each

• Retransmission using MCS-6

• for further retransmission, 74byte block will be

segmented into 2 x 37 blocks MCS-3.


37 byte 37 byte

37 byte


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GPRS/ EDGE


Modulation and Coding Schemes for EDGE

MCS Modulation Code rate Bit rate/TS

MCS-1 0.53 8.8

MCS-2 GMSK 0.66 11.2

MCS-3 0.8 14.8

MCS-4 1 17.6

MCS-5 0.37 22.4

MCS-68-PSK

0.49 29.6

MCS-7 0.76 44.8

MCS-8 0.92 54.5

MCS-9 1 59.2

Family H Code rateRLC/20m

C 1/2 1

B 1/2 1

A 1/2 1

C 1/2 1

B 1/3 1

A 1/3 1

B 0.35 2

A 0.35 2

A 0.35 2

GPRS/ EDGE


Link Adaption: LA

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40 45C/I

k b i t / s

MCS-1MCS-2MCS-3MCS-4

MCS-5

MCS-6

MCS-7

MCS8

MCS-9


43/52


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GPRS/ EDGE


GERAN

• GSM EDGE Radio Access Network

for easy transition between 2G and full 3G (UMTS) and align

with the UMTS SERVICES

• Motivation

– All IP Network

– Low cost of operation

– One platform

– support of new services

– Support for different access networks

GPRS/ EDGE


Requirements GERAN

• Spectrum efficient support for VoIP, (end-to-end

IP-based voice service), Quality TDMA

• Integration of all services over IP infrastructure

• Alignment with UMTS/UTRAN service classes and

QoS

• Common GPRS and GSM Core Network for EDGE

and UTRAN

• Support of EDGE/GPRS R97 and R99 terminals

• Software upgrade to EDGE R99 base stations


45/52

GPRS/ EDGE


EDGE R4,5 features

• Channel coding

– Turbo code

• Interleaving (variable length)

• Voice over 8PSK AMR half rate R5

• Wideband codec AMR R5

• all IP (RT application)

• PDCP

• enhanced cell reselection R4

GPRS/ EDGE


GERAN

3G SGSN

Iu-ps'

R

TE MT

Um

BSS

GERAN

Core Network

3G MSC

MGW

SGSN server

SGSN

MSC server

Iu-cs'

Gb

MSC

A

MGW

GERAN connects to PS CN through:

Iu-ps for R4, R5 terminals

New protocols

Gb for R97 and R99 terminalsLLC and SNDCP protocols

GERAN connects to CS CN through:Iu-cs or A


46/52

GPRS/ EDGE


GERAN Interfaces

• A

– GSM CS interface

• Iu-CS – WCDMA CS interface could be considered for GERAN

• Gb

– GPRS interface not suitable for RT transmission

– LLC+RLC both ARQ protocols

– IP instead of FR

• Iu-PS – UTRAN PS, IP, QoS, AAL2/ATM , possibly IP over SDH

GPRS/ EDGE


Functional split between CN and GERAN

• HO support for RT IP services in RAN (new in R4)

• Ciphering

– R4 GERAN, – R99 SGSN

• Header compression

– R4 GERAN

– R99 SGSN

• Radio resource handling in RAN (R99, R4)

• Support Iu bearer (R5)


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GPRS/ EDGE


Iu-PS and Gb

Function

ciphering

compression

IP header & payload

Termination of

LLC and SNDCP

Buffer management

flow controlRR handeling

Iu-PS

RAN

RAN

RAN

RAN

NoRAN

Gb

CN

CN

CN

CN

YesCN+RAN

GPRS/ EDGE


Protocol Stack R4,..

• PDCP (Packet data convergence protocol UTRA)

– TCP/IP, UDP/IP with H compression

– Buffering and numbering PDCP SDUs

– Transfer of user data

– Multiplexing

L1

MAC

RLC

PDCP

L1

MAC

RLC

PDCP

MS CN


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GPRS/ EDGE


Protocol Stack R99

• LLC

– ACK and none-ACK modes

– Error detection

– ciphering

• SNDCP

– Transfer of user data

– Multiplexing

– Buffering and ARQ

– Segmentation and assembly

– H and payload compression (optional) TCP

– management of delivery sequence

L1

MAC

RLC

LLC

L1

MAC

RLC

LLC

MS CN

SNDCP SNDCP

GPRS/ EDGE


Compare SNDCP and PDCP

• Overhead

– PDCP 1 Byte

– SNDCP

– ACK LLC+ Segment = 3+1= 4

– none-ACK LLC+Segment=4+3=7

– LLC

– ACK LLC =7

– none_ACK LLC=6

• example: VoIP, none_ACK LLC without segmentation

PDCP 1 byte SNDCP/LLC = 4+6=10 bytes


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GPRS/ EDGE


Protocol Layering and Segmentation

Appli catio n PDU PayloadHeader

PayloadHeader TCP PDU

PayloadHeader PayloadHeader

PayloadHeader

IP PDU

PayloadHeader PayloadHeader PayloadHeader SNDCP PDU

PayloadHeader PayloadHeader LLC PDU

PayloadH PayloadH PayloadH PayloadH PayloadHMAC/RLC PDU

Protocol Header size(octets)

Resulting PDU size(octets)

TCP 20 556

IP 20 576SNDCP 4 580

LLC 7 587

Total 51 587

Maximum TCP segment size: 536 ⇒

GPRS/ EDGE


TCP Transactions (simplified)

Data WWW / Bulkobject

ACK

Data

WWW / Bulkobject

WWW / BulkClient

TCP Client TCP Server WWW / Bulk

Server

ACK

ACK

Data

Data

Data

Data

Data

WWW / Bulkobject

Data

ACK

Data

Data

ACK

last Data

ACK

WWW / Bulkobject

delayed ACK(max. 200ms)


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GPRS/ EDGE


RLC Downlink Transactions

T i m e

Data

Data

Data

Packet Downlink Ack/

Nack

Packet Downlink Ack/Nack Final

RLC-MS RLC-BSSTCP (Client) TCP (Server)

Packet Control

Acknowledgement

TCPSegment

TCP Segment

downlink TBFestablishment

(60ms)

Data

Packet Downlink

Assignment

GPRS/ EDGE


Downlink TBF Establishment

• Multi-Slot capability: 4TSsunused (=overhead) RLC Radio Blocks

PDATime

20ms 20ms(idle block)

20ms(uplink PacketControl ACK)

data

data

data

data

data

data

data

data

data

idle

idle

padding

data transmission

transmission delay

TS4

TS3

TS2

TS1


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GPRS/ EDGE


RLC Uplink Transactions

T i m e

Packet Channel

Request

Packet Uplink

Assginment

Data

Packet Uplink Ack/

Nack

RLC-MS RLC-BSSTCP (Client) TCP (Server)

TCP ACK

Data

Data

Packet Control

Acknowledgement Final

Packet Uplink Ack/

Nack

TCP ACK

pendingretransmission

GPRS/ EDGE


Over Head calculation

• Example :GPRS

– one TCP = 536 B

– TCP+OH=536+51=587B

– # of RLC= (TCP+OH)/RLC-size

– total_data=(#of RLC+TBF)*RLC_size

– OH=(total_data -TCP_size) /total_data

TBF signaling overhead:

CS

CS1

CS2

CS3CS4

RLC (B)

20

30

3650

#of RLC

30

..

..12

TBF

22

22

Protocol

TCP

IP

SNDCPLLC

total

Header

20

20

47

51

Total Data

640..

..700

OH

16.2%..

..23.5%


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GPRS/ EDGE


Header + Padding Overhead EDGE R99

ModulationandCodingScheme

Applica-tion PDUsize(octets)

RLC PDUpayloadsize(octets)

Number of RLC PDUs(octets)

TotalData(octets)

Over-head

%

MCS 1501000

22551

1101122

54.510.9

MCS 5 501000

56 22

1121120

55.410.7

MCS 9501000

14818

1481184

66.215.5

• Overhead Calculation

Example 1:

– MCS-1, Bulk PDU 50B

⇒ 50bytes

⇒

101 bytes including headers(51 bytes per TCP segment)

⇒ 5 RLC PDUs=110 bytes

including padding

• Example 2:

– MCS-9, Bulk PDU 1kB

⇒ 1000/536 =1 complete TCP segment + 464 bytes

1000+2*51 =1102 bytes including headers

⇒ 1102/148 =8 RLC PDUs=1184 bytes including padding

– OH= (1184-1000)/1184=15.5%

GPRS Understanding

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