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Evolution From GSM to UMTS




Steps on the way to 3G

HSCSD

GPRS

EDGE

UMTS



HSCSD(High Speed Circuit Switched Data)

Introduction

Next step of GSM data development

High speed access to data services

Circuit switched connection




HSCSD technology New channel coding scheme

(increase the data rate to 14.4 kbps)

Possibility of combining time slots

(variety of bit rates from 14.4 to 57.6 kbps)

Using different data rates in the uplink andthe downlink direction




Symmetrical connection(2+2)

2 time slots for the uplink

2 time slots for the downlink

Asymmetrical connection

(3+1)

1 time slots for the uplink

3 time slots for the downlink

Example: downloading a

web page




Type of connection speeds

Normal connection speed Max connection speed




Applications requiring HSCSD1. Transparent applications (fax ,video)

2. Non transparent applications (www ,email)

Examples1. Email sending and receiving

2. www browsing

3. File transfer4. Real times applications

5. Time critical wireless imaging




Disadvantage of HSCSD

Limited number of user



GPRS(General Packet Radio Service)

Introduction

Permits packet switched besides circuit switched

It is an expansion of GSM and a main step towards 3G Charging is no longer based on the transmission time

Data rate depends on the coding scheme (CS1 CS4)

with a max theoretical data rate 171.2 kbps



GPRS(General Packet Radio Service)

How to upgrade a GSM network to GPRS?

1. For the BSS software upgrade

hardware upgrade

(PCU)

2. New GPRS support nodes (SGSN – GGSN)



GSMNetwork

PSTN

BSC

GSM

BTS

GSMBTS

MSC



PSTN

BSC

GSMBTS

GSMBTS

MSC

GSM + GPRSNetwork

PCU

Other nets

GGSN

SGSN



Node B Node B

RNC

PSTN

BSC

GSMBTS

GSMBTS

PCU

Other nets

GGSN

SGSN

GSM & UMTSNetwork

GGSN

SGSNMSCu u



GPRS Coding Schemes

GPRS using samephysical RF layer asGSM speech

Data is coded intonormal bursts (456bits / 20ms)

Coding

Scheme

Coded

bits

Data

Rate(kbps)

Multiple

SlotMax.

Data

Rate

(kbps)

CS-1 456 9.05 72.4

CS-2 588 13.4 107.2

CS-3 676 15.6 124.8

CS-4 456 21.4 171.2Max. Per TS Data rate (kbps)

0

5

10

15

20

25

CS-1 CS-2 CS-3 CS-4

K B i t s p e r S e c o n d



GPRS Coding Schemes

Coding Scheme User Data Rate / TS Error correction Max throughputwith 8TS

CS-1 9.05 Kbps High 72.4 Kbps

CS-2 13.4 Kbps Medium 107.2 Kbps

CS-3 15.6 Kbps Low 124.8 Kbps

CS-4 21.4 Kbps None 171.2 Kbps

Higher data rate for increased throughput

Benefits

• Improved user perception

• Potential for new revenue streams (new applications / higher grade of service)

• Opportunity for market differentiation



Timeslot sharing

BTS

BCCH GPRS GPRS GPRSTCHTCH TCH User rate at

CS2 = 40.2 kbps

TCH

A Voice call require the GPRS TS

Site with one carrier will be able to share time slots (Voice and GPRS)



Timeslot sharing

BTS

BCCH GPRS GPRSTCH TCH TCHTCH User rate at

CS2 = 40.2 kbps

TCH

A Voice call takes the GPRS TS

User rate at

CS2 = 26.8 kbps

Site with one carrier will be able to share timeslots (Voice and GPRS)



BTS

BCCH GPRS GPRS GPRS GPRS GPRS GPRS GPRS

MAX

CS2 = 93.8 kbps

BTS

BCCH TCH TCH TCH TCH TCH TCH

CS2 = 13.4 kbps

GPRS

Dynamic allocation of channels between circuit and packet:

Channel sharing



(And more economical)

ADVANTAGES OF GPRS

1. Faster data transfer rates up to 115 kbps bydedicating all 8 time slots to GPRS

GPRSGSM

Higher data rate



ADVANTAGES OF GPRS

2. Always on connection :

Eliminates lengthy delays required to

reconnect to the network to send andreceive data

Information can be pushed to the end user

in real time Bill by the packet (data exchanged) and

type of service rather than by minute



ADVANTAGES OF GPRS

3. Robust connectivity:

First the coding scheme is

selected depending on theradio conditions

If error is detected in a framereceived in the BSS, the frame

is retransmitted until properlyreceived before passing it onthe GPRS core network



ADVANTAGES OF GPRS

4. Broad application support

Fully enable internet applications (e-mail, web

access, instant messaging and file transfer) multimedia web content

Chat, visual information, still images, movingimages and document sharing



ADVANTAGES OF GPRS

5. Security support

GPRS builds on the authentication and

security model of GSM It enables an additional authentication

using protocols like RADIUS before thesub is allowed to access to the internet or

other data networks



EDGE(Enhanced Data Rate for GSM Evolution)

Introduction Increase data rates up to 384 kbps

Introduces a new modulation

technique (8PSK) and channel coding The last step before UMTS

It is built on an existing GSM/GPRS

system




Have the same symbol rate of GMSK Each symbol is represented by 3 bits

8PSK generates same interference on adjacent

channels as GMSK. We use the same channel structure and width

and frequency plan of GPRS

The distance between symbols is shorter using8PSK than GMSK misinterpretation




Packet handling The ability of

retransmission of packets with a morerobust coding scheme

Unlike GPRS in which

retransmission of packets is made withthe same codingscheme




Impact of EDGE on existing GSM/GPRS networks

Hardware upgrade to the BSS (new transceiver ineach cell)

Software upgrade to the BS and BSC No change in the core networks New terminals

- Terminal which provides 8PSK in the uplink and

the downlink - Terminal which provides GMSK in the uplink and 8PSK in the downlink



GPRS -- COMPLEXITY

SGSN

GGSN

Gb

Gn

Gc

Gi

Gs

Gn

HLR

BSC

MSC

PSTN

BTS

BTS

Abis A

D

Abis

A

PDN

NEW

NEWNEW

NEW

NEW

NEW

NEW

NEW

NEW

NEWNEW

NEW



EDGE -- EVOLUTION

SGSN

GGSN

Gb

Gn

Gc

Gi

Gs

Gn

HLR

BSC

MSC

PSTN

BTS

BTS

Abis A

D

Abis

A

PDN

NEW

NEW




EDGE benefits Short-term benefits: Capacity and

performance Easy implementation on a GSM/GPRS

network Cost effective

Increase the capacity and the data rateof GPRS

Enabling new multimedia services

Download - Evolution From GSM Towards UMTS

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