Gprs 1

Prepared by:Agilent Technologies600 Atlantis RoadMelbourne, FL 32904 USAPhone: (321) 952-8300Fax: (321) 725-5062www.agilent.com

Copyright2001 by Agilent TechnologiesAll rights reserved. No part of this book shall bereproduced, stored in a retrieval system, or transmittedby any means, electronic, mechanical, photocopying,recording, or otherwise, without written permissionfrom Agilent Technologies

RF EngineeringContinuing Education & Training

Introduction to GPRS

Page 2 Agilent RestrictedGPRS Slides (Rev A).ppt

Class Agenda

• Overview of GSM

• What is GPRS?

• Network Architecture

• Protocol Stack

• Air Interface

• Mobility Management

• Quality of Service

• Optimization and RF Planning

• Traffic Planning

• HSCSD, EDGE and 3G Growth Path

• Conclusions


Class Agenda

• Overview of GSM– Network Architecture

– Air Interface

– Additional Features

• What is GPRS?


• Protocol Stack

• Air Interface





Overview of GSM


F1

F2

F3

F4

F1

F2

F3

F4

F2

F1

F2

N=4 Frequency Reuse Concept

• Second Generation Technology

• Groupe Speciale Mobile

• Developed by ETSI

• International wireless standard

• Based on the cellular concept

• Frequency reuse implementation

• Over 480 million subscribers

• GSM900, DCS1800, PCS1900, R-GSM

100 200 300 400 5000

GSM

IS-95

IS-136

PDC (Japan)

Analog

Millions of subscribers (Feb 2001)source: EMC



Overview of GSM

• All GSM documents are standardized by ETSI

• Standards are grouped into 12 series

• Allows for easy integration of network elements from different equipment vendors

• Significantly reduces the cost of the overall network deployment



Overview of GSM - Network Architecture• GSM network can be divided into three main subsystems:

– Base Station Subsystem - BSS

– Mobile Station Subsystem - MSS

– Network Switching Subsystem - NSS

GSM Network Layout

MSCArea

H LR

MSCArea

VLR

MSCTRAUBSC

BTS

BTS

BSS

MSC Area

BSS

BSSBTS

PSTN

PLMN - Public Land Mobile Netw ork

Gatew ayMSC

NSS


Overview of GSM - Mobile Station


Keyboard

Control

Display

Transmit AudioSignal

Processing

Receive AudioSignal

Processing

ChannelDecoding

DeinterleavingM essage

Regenerator

ChannelEncoding

InterleavingM essage

Generator

Ciphering

Ciphering

RFProcessing

RFProcessing

SIM

Duplexer

Antenna

ANTENNAASSEM BLY

TRANSM ITTER

RECEIVER

TRANSCEIVER UNITCONTROLSECTION

• Offered as a phone for voice services

• Data services will bring new devices to the market

• Two functional parts:

– HW/SW radio interface

– SIM

• Two types of SIM

– Smart Card

– Plug-in

GSM Mobile Architectural Diagram


Overview of GSM - Base Transceiver Station

• BTS is a set of transceivers (TX/RX).

• GSM BTS can host up to 16 TX/RX.

• In GSM one TX/RX is shared by 8 users.

• The main role of TX/RX is to provide conversion between traffic data on the network side and RF communication on the MS side.

• Depending on the application, it can be configured as macrocell, microcell, omni, sectored, etc.



Overview of GSM - Base Station Controller• Provides a small digital

exchange with some mobility tasks

• Connects to one or several BTS on the Abis Interface

• Connects to the MSC on the A Interface

• Designed to offload most of the radio link related processes from the MSC

• Provides clock distribution to BTS

• Communicates with the OMC



Overview of GSM - TRAU

• TRAU is responsible for transcoding the user data from 16Kb/sec to standard ISDN rates of 64Kb/sec.

• It can physically reside on either BSC side or MSC side.

• If it resides on the MSC side, it provides substantial changes in the backhaul – 4 users over a single T-1/E-1 TDMA channel.

• TRAU, BSC and BTSs form Base Station Subsystem (BSS)



Overview of GSM - MSC

• Responsible for connecting the mobile to the landline side

• GSM MSC is commonly designed as a regular ISDN switch with some added functionality for mobility support

• GSM Network can have more than one MSC

• One of the MSC has an added functionality for communication with public network – Gateway MSC (GMSC)

• All calls from the “outside networks” are routed through GMSC

GSM MSC and Gateway MSC



Overview of GSM - HLR/AuC

• Database for permanent or semi-permanent data associated with the user

• Logically, there is only one HLR per network

• Typical information stored in HLR: International Mobile Service Identification Number (IMSI), service subscription information, supplementary services, current location of the subscriber, etc.

• HLR is usually implemented as an integral part of MSC

• AUC is an integral part of HLR responsible for ciphering and encryption.

• GSM specifies elaborate encryption schemes.

• There are three levels of the encryption:

– A5/1 – Used by countries in Europe and USA

– A5/2 – Used by countries and the so called COCOM list

– No encryption – used by all other countries



Overview of GSM - VLR and EIR

• Temporary database that keeps the information about the users within the service area of the MSC

• Usually there is one VLR per MSC

• The main task of the VLR is to reduce the number of queries to HLR. When the mobile, registers on the system its information is copied from HLR to VLR

• VLR is usually integrated with the switch

• Separation of SIM and mobile opens possibility for market of stolen and fraudulent equipment.

• GSM Systems are equipped with Equipment Identity Register (EIR) – responsible for tracking the equipment eligibility for service.

• EIR maintains three lists of mobile terminals:

– White list: is the list of approved mobile types.

– Black list: list of the International Mobile Equipment Identity (IMEI) numbers that are barred from service.

– Gray List: The list of mobiles that are tracked within the GSM system.



Overview of GSM - Interfaces

• GSM defines different interfaces between two system components

• Allows for multi-vendor implementation

• Promotes more competition

• Lower costs

• Air interface is limiting in terms of capacity

• Air interface is also called Um interface

BTS

BSC MSC

VLR

EIR

VLR

Gatew ayMSCM S

H LR

E

FF

B B

C

D D

G

A -

In

terf

ace

Ab

is -

In

terf

ace

Air

- I

nte

rfac

e

GSM Interfaces



Overview of GSM - Air Interface

• GSM is a FDMA/TDMA based technology

• Transmissions are discontinuous

• Each user is assigned a timeslot

• Each frequency is divided into eight timeslots

• Each channel has a 200 kHz bandwidth

• Overhead signaling is required for coordination and control

• Information is sent in bursts

• Several types of bursts

GSM as a FDMA/TDMA Interface

BTS

USER 1 USER 2 .... USER 8

USER 6 USER 7 USER 8 USER 1

USER 1,ARFCN 1

USER 2,ARFCN 1

USER 8,ARFCN 1

USER 9,ARFCN 2

USER 10,ARFCN 2

USER 16,ARFCN 2

ARFCN 1

ARFCN 2



Overview of GSM - Burst Types

Tail Traffic/Signaling Flag Training Sequence Flag Traffic/Signaling Tail

3 57 1 26 1 57 3

Tail Synchronization Training Sequence Synchronization Tail

3 33939 64

• Used to carry information on both control and traffic channels

• Mixture of data and overhead

• GSM defines 8 training sequences assigned in color code mode

• Both on the forward and reverse link

• Facilitates the synchronization of the MS to the network at the base band

• Commonly referred to as S-burst

• Only on the forward link

• The same sync sequence is used in all GSM networks

Synchronization Burst

Normal Burst




• Used when the MS is accessing the system

• Shorter in length – burst collision avoidance

• Extended synchronization sequence

• Used only on the reverse link

• Supports MAHO

• Used to ensure constant power level of the broadcast control channel


Dummy Burst

Access Burst

Tail Predefined Bit Sequence Tail

3 3142

Tail Synchronization Access Bits Tail

8 41 36 3

• GSM mobiles use slotted ALOHA to access the system

• In the case of collision – a hashing algorithm is provided




• Sometimes referred to as the F-burst

• Provides mobile with precise reference to the frequency of the broadcast control channel

• Inserting the F-bursts on the control channel produces spectral peak 67.7 KHz above the central frequency of the carrier


• Spectral characteristics of the control channel.

• The peak in the spectrum allows for easier MS network acquisition

Tail Fixed Bit Sequence (All zeros) Tail

3 3142

fc fc+67.7 KHz frequency

Power Spectrum Density

BW = 200KHz



Overview of GSM - Physical Channels• A GSM physical channel can carry several different types of logical channels

• Can be divided into two categories: traffic and signaling

• Signaling channels can be further categorized as:

– Broadcast

– Common Control

– Dedicated Control



Overview of GSM - Frame Hierarchy

• Different organization on the superframe level for different logical channels

0 1 2 3 4 5 6 7 21 22 23 24 25

1 TDM A Frame4.615 ms

26 M ultiframe120 ms

51 M ultiframe235.4 ms

51 x 26 Superframe or 26 x 51 Superframe6s 120 ms

Hyperframe3 h 28 min 53 s 760 ms

0 1 2 3 4 48 49 50

0 1 2 3 4 5 6 7 2043 2044 2045 2046 2047

0 1 2 3 4 5 6 7 46 47 48 49 50

0 1 2 3 4 23 24 25

0 1 2 3 4 5 6 7



Overview of GSM - Additional Features• GSM supports additional features that enable a better

spectrum utilization and increased capacity:

– Timing Advance - TA

– Discontinuous Transmission - DTX

– Mobile Assisted Handover - MAHO

– Dynamic Power Control - DPC

– Hierarchical Cell Structure - HCS

– Frequency Hopping - FH

– Intracell handovers



Overview of GSM - Quiz!

• Name some of the components of the GSM architecture and briefly explain their function

• What are the different types of bursts?

– _______________

– _______________

– _______________

– _______________

– _______________

• What are the different types of logical channels ?

– _______________, _______________, _______________

– _______________, _______________, _______________

– _______________, _______________, _______________

– _______________



Class Agenda

• Overview of GSM

• What is GPRS?


• Protocol Stack

• Air Interface





• HSCSD, EDGE, and 3G Growth Path



What is GPRS?

• 2G technologies were designed for mobile telephony

• Landline services have higher data rates than wireless counterparts

• Next step: mobile wireless data services

• GPRS: General Packet Radio Service

• GSM has distinctive approach towards 3G

• Intermediate step refers to as 2.5 G

• Allows for smooth transition from voice to data services

• Maintain upgrade costs to a minimum



What is GPRS?

Source: Ericsson’s Web Site Oct-00

Su

bscr

ibe

rs (

M)

0

900

300

600

96 98 00 02 03

Cellular

Internet

Cellular Internet

• In voice networks, RF is the main limiting factor. In data networks, RF and many other factors will affect the performance for individual users

• Fixed network infrastructure performance

• Types of applications and service provision

• Number of users active in an area



What is GPRS? - Circuit vs Packet Switch

• 2G technologies are circuit switched

• Dial-up type connections

• A single user occupies a channel for the entire transmission

• Requires time-oriented billing

• GSM transmissions are bursty

• Bursty nature favors data services

• GPRS is packet switched technology

• More appropriate for data services

• Continuous flow is not required

• Access is based on demand only

• Several users can be multiplexed

• Billing based on negotiated QoS and usage



What is GPRS? - Types of Data Services• Most popular Internet data

applications include:

– E-mail

– Web browsing

– File transfers

– Real time audio

– Streaming video

• Different services have different throughput requirements

• GSM evolution is expected to provide services at throughputs similar to their landline counterparts



What is GPRS? - A 2.5 G Solution

GPRS - G eneral Packet R adio ServicePDN - Packet D ata N etworkLAN - Local A rea N etworkW W W - W orld W ide W eb

Laptop com puter

PALM DEVICE

PDNGPRS

Other GPRSNetw orks

AirIn terface

FTP

FileTransfer

Video

Multimedia

W W W

E-MAIL

LAN

• GPRS is a 2.5 G solution implemented over existing GSM network

• Theoretical data rates are up to 160 kbps

• GPRS makes a more efficient use of the air interface

• Supports point-to-point and point-to-multipoint transmissions

• GPRS will take over short message service (SMS) from GSM signaling channels

• New QoS parameters:

– Precedence

– Reliability

– Delay

– Throughput



What is GPRS? - Important Challenges• There are several hardware and software

limitations that will decrease the expected data rates significantly

• Mobile data will impose a demand for more IP addresses. The existing version of IP is already reaching saturation

• The idea that the market will accept mobile data service with eagerness is still somewhat questionable

• The 3G standards are already finalized and implementation will follow shortly after 2.5 G



Class Agenda

• Overview of GSM

• What is GPRS?

• Network Architecture– SGSN, GGSN

– GR, PCU

– Mobile Station

• Protocol Stack

• Air Interface






GPRS Network Architecture• GPRS introduces new entities to support data packet transmissions

• New entities are PCU, GSN, Border Gateway, and GPRS register

GPRS Network Architecture

ForeignPLMNBG

M S

BSC

DATA-BASESUBSYSTEM

Other SGSNBG

VLR H LRG R

EXTERNALNETW ORKS

BTS

BTS

GSMRADIOSUBSYSTEM

GPRSSUBSYSTEM

PDNGGSNSGSNPCU

AirInterface

GbInterface

GnInterface

GnInterface

GpInterface

GiInterface

GcInterface

GrInterface

GsInterface

AbisInterface

BTS - Base Transceiver StationBSC - Base Station ControllerPCU - Packet Control UnitSGSN - Service GPRS Support NodeGGSN - Gateway GPRS Support NodeBG - Border GatewayHLR - HomeLocation RegisterVLR - Visitor Location RegisterGR - GPRS RegisterPDN- Packet Data Netw ork



GPRS Network Architecture - SGSN

SGSNPCU

BSS

BSS

BSS

SGSNPCU

SGSNPCU

GGSN

• Serving GPRS support node

• Delivers data packets to the mobile stations

• Each SGSN is assigned to a specific service area

• Allows for very little change in the BTS and BSC

• All mobile stations communicate to the SGSN in the area

• Provides authentication and ciphering

• Handles mobility management

• Introduction of the routing area - RA

• Also responsible for billing over the air interface



GPRS Network Architecture - GGSN

GGSN

GGSN GGSN

PDNPDN

PLMN

PDN

• Gateway GPRS support node

• Allows the GPRS network to communicate with external PDNs

• Routes all packet data units through the corresponding SGSN

• Whereas the SGSNs can change during cell reselections, the GGSN remains the same during an ongoing packet transaction

• Supports PTP and PTM transmissions

• Responsible for billing related to connections with external PDNs



GPRS Network Architecture - GR and PCU

M S

BSC

SGSNPCU

BTS

TRAU MSC

• GPRS Register

– Database containing information about GPRS subscribers

• Packet Control Unit

– Manages and controls radio-related operations

– Converts frames coming from the SGSN into TRAU frames

– Compresses and decompresses frames

– PCU allows very few modifications to the BSS



GPRS Network Architecture - PCU Locations

M S

M S

M S

PCU

BSC SGSNPCU

BSC SGSN

BSC SGSNPCU

BTS

BTS

BTS

• Possibilities for location are similar to the TRAU

• From the resource utilization perspective, the best location for the PCU is at the SGSN

• Conceptually, PCU still remains a part of the BSC



GPRS Network Architecture - Border Gateway

ForeignPLMN

BGBGGGSN GGSN

HomePLMN

• Risk from hackers in external PLMNs

• Protect subscribers from security break-ins

• Border Gateway is implemented to provide a maximum level of security

• Acts as a firewall to the GPRS network

• No guidelines for protection at the Gi interface

• Gi security is left open to equipment manufacturers



GPRS

• GPRS standard defines three mobile station classes

• Class A supports simultaneous circuit and packet switched communications

• Class B supports packet and circuit switched sequentially

– Currently only Class B mobiles being developed

• Class C does not support parallel operation

• Operates in either packet or circuit mode only

• Low cost unit available for mass market deployment



GPRS Network Architecture - GSM and GPRS

GMSC

M S

ForeignPLMNBG

BSC

BSC

Other MSC

DATA-BASESUBSYSTEM

Other SGSNBG

VLRH LRG R

EXTERNALNETW ORKS

BTS

BTS

BTS

GSMRADIOSUBSYSTEM

GSMSW ITCHINGSUBSYSTEM

GPRSSUBSYSTEM

PDN

ISDN

MSCTRAU

GGSNSGSNPCU

AirInterface

AbisInterface

GbInterface

GnInterface

GnInterface

GpInterface

GiInterface

GcInterface

GrInterface

GsInterface

AInterface

BInterface

CInterface

EInterface

DInterface

AbisInterface

AirInterface

PSTNBTS

M S



GPRS Network Architecture - Quiz!

• Name some of the components of the GPRS architecture and briefly explain their function

• What are two types of GSNs?

– _______________

– _______________

• What are the different types of mobile classes ?

– _______________

– _______________

– _______________

• Which component allows for few changes at the BSS?

– _______________



Class Agenda

• What is GPRS?


• Protocol Stack– OSI/ISO Model

– GPRS Protocol Stack

– GTP

– SNDCP and BSSGP

– RLC/MAC and LLC

• Air Interface






GPRS Protocol Stack - ISO/OSI Model

Session Layer

Transport Layer

Netw ork Layer

Data Link Layer

PresentationLayer

Physical Layer

ApplicationLayer

1

2

3

4

5

6

7

Session Layer

Transport Layer

Netw ork Layer

Data Link Layer

PresentationLayer

Physical Layer

ApplicationLayer

1

2

3

4

5

6

7

Netw ork Layer

Data Link Layer

Physical Layer

Node A Node B Node C

peer-to-peer protocol

• International Telecommunications Union (ITU) and International Standardization Organization (ISO) developed Open Systems Interconnect (OSI)

• Allows for compatibility between different equipment manufacturers



GPRS Protocol Stack - ISO/OSI Model

Node A Node C

Application Layer

Presentation Layer

Session Layer

Transport Layer

Netw ork Layer

Data Link Layer

Physical Layer

234567Info

Info

2

3

4

5

6 7

7 Info

Info

6 7 Info

5 6 7 Info

4 5 6 7 Info

5 4 5 6 7 Info

6 5 4 5 6 7 Info 1

2

3

4

5

6

7

2

3

4

5

67

7Info

Info

67Info

567Info

4567Info

34567Info

234567Info1

2

3

4

5

6

7

Info

• Each layer adds its own header to the message

• Same layer at destination node removes its corresponding header

• Physical layer delivers message from one node to the next

• In GSM, layer 1 corresponds to the air interface

• GPRS layers fall between OSI layers 2 and 3



GPRS Protocol Stack

M SBTS

BSC PCU SGSN GGSN

RFL PhysicalLayer

PhysicalLayer

PhysicalLayer

PhysicalLayer

PhysicalLayer

PhysicalLayer

PhysicalLayer

PhysicalLayer

MACNSFR

RLC BSSGP

NSFR

L2

BSSGP IP

LLC UDP

SNDCP GTP

L2

IP

UDP

GTP

RFL

MAC

RLC

LLC

SNDCP

Netw orkLayer

Netw orkLayer

AbisInterface

AirInterface

InternalInterface

GbInterface

GnInterface

OSILayer 1

OSILayer 2

OSILayer 3



GPRS Protocol Stack - GTP

• GPRS Tunneling protocol

– Allows communication between the GGSN and SGSN

– Data transfer is done via encapsulation and tunneling

– GTP header includes such as PDU type, QoS parameters, and tunnel identifier (TID)

– TID differentiates PTP from PTM transactions


GTP PDU

N PDUTCP/IPHeader

User Data

Netw ork Layer

GTP Layer

GTPHeader

TID User Data


GPRS Protocol Stack - SNDCP & BSSGP• Subnetwork Dependent Convergence Protocol

– Makes GPRS network transparent to the common subscriber regardless of what application is running

– Responsible for converting network packet data units into GPRS suitable format

– Multiplexing of SN packet data units over the LLC layer

– Segmentation and Desegmentation of SN packets into LLC packets

– Compression of the IP header information• Base Station Subsystem GPRS

Protocol

– Routing between SGSN and PCU

– Provide radio related info for RLC/MAC

– Routing goes via Network Relay

– Transparent transfer of LLC frames

– Convey QoS information


TCP/IPHeader

User Data

Netw ork Layer

SNDCP Layer

SN-PDUHeader

Com pressed Inform ation TailSN-PDUHeader

Com pressed Inform ation Tail


GPRS Protocol Stack - LLC

• Logical Link Control

– Provides a logical reliable link between MS and SGSN

– Designed as independent as possible from the radio interface layers

– Encapsulation of SNDCP packet data units

– Ciphering procedures between MS and SGSN

– Detection and recovery of lost LLC packet data units

– Responsible for acknowledged/unacknowledged operation


Fram eHeader

Radio Blocks

SNDCP Layer

SN-PDUHeader

Compressed Inform ation TailSN-PDUHeader

Compressed Inform ation Tail

FCS

LLC Layer

Fram eHeader

Radio Blocks FCS Fram eHeader

Radio Blocks FCS


GPRS Protocol Stack - RLC / MAC

• RLC sublayer

– Transmission of data blocks across the air interface

– Retransmission of error data blocks using ARQ

• MAC sublayer

– Provides access to a given transmission medium

– Controls access signaling, medium sharing by multiple users

– Release operations over the radio channel

– Access is based on slotted ALOHA

– Performs mapping of RLC blocks onto the GSM physical channels


PC PCT TRLC

HeaderRLC/MAC Signaling

Inform ationUSF BCS USF BCS

RLC/MACLayer

RLC Data

RLC Data B lock RLC/MAC S ignaling B lock

Fram eHeader Radio Blocks FCS

LLC Layer

Fram eHeader Radio Blocks FCS Fram e

Header Radio Blocks FCS


GPRS Coding Schemes

• GPRS defines four coding schemes

• Only CS-1 is mandatory for the BTS

• All coding schemes are mandatory for the MS

• The higher the coding scheme, the higher the throughput

• The higher the throughput, the lower protection against errors

RLCHeader

RLC Data

160 Data Bits (depends on size RLC header)£

RLCHeader

RLC Data

240 Data Bits (depends on size RLC header)

RLCHeader

RLC Data


RLCHeader

RLC Data


£

£

£

CS-1

CS-2

CS-3

CS-4



GPRS Radio Block Structure

• A packet transmission is referred to as a temporary block flow (TBF)

• Each TBF is assigned a temporary flow identity (TFI)

• The TFI is located inside the LLC header information

• The TFI allows for multiplexing several users over the same timeslot

• The TFI also allows to assign priority classes


PC PC

NormalBurst

NormalBurst

NormalBurst

NormalBurst

NormalBurst

NormalBurst

NormalBurst

NormalBurst

T TRLC

HeaderRLC/MAC Signaling

Inform ationUSF BCS USF BCS

Netw ork Layer

SNDCP Layer

LLC Layer

RLC/MACLayer

RF Layer

RLC Data

approx 1.6 KB

1.5 KB or less

20 - 50 bytes

4 x 114 bits

RLC Data B lock RLC/MAC S ignaling B lock

Fram eHeader Radio Blocks FCS Fram e

Header Radio Blocks FCS Fram eHeader Radio Blocks FCS

SN-PDUHeader

Compressed Inform ation TailSN-PDUHeader

Compressed Inform ation Tail

TCP/IPHeader

User Data


Protocol Stack - Quiz!

• Mention the seven different layers of the ISO/OSI reference model:

– _______________, _______________, _______________

– _______________, _______________, _______________

– _______________

• The GPRS protocol stack consists of the following protocols

– _______________, _______________, _______________

– _______________, _______________

• The maximum throughput achieved using CS-2 and two timeslots is:

– _______________

• Different packet transactions from different users can be identified via the

– _______________



Class Agenda


• Protocol Stack

• Air Interface– GPRS Logical Channels

– The Master Slave Concept

– The 52-Multiframe

– Timing Advance

– Power Control







GPRS Air Interface

• Air interface continues to be limiting factor in terms of capacity

• GPRS shares the same interface with GSM

• Recall GSM has 200 kHz and eight TS

• GPRS utilizes multiplexing and dynamic channel allocation to use the air interface more efficiently

• Some channels can be configured for data traffic and others for voice traffic

• Channels are reconfigured accordingly based on demand

GPRS Air Interface


PhysicalLayer

MAC

RLC

RFL

MAC

RLC

MS BSS

RLC - Radio Link ControlM AC - M edium Access ControlRFL - Radio Frequency LinkM S - M obile StationBSS - Base Station Subsystem


GPRS Logical Channels

• Signaling and traffic channels are also required for GPRS

• A new family of packet data channels PDCHs has been defined

• Some of the existing GSM signaling channels can still be used for GPRS

• The GPRS mobile still requires to listen to the GSM broadcast channel for GPRS channel information



GPRS 52-Multiframe

• Each radio block is transmitted over 4 TDMA frames

• Resource allocation is done in terms of blocks for both uplink and downlink

• A 52-Multiframe consists of:

– twelve blocks for PDCHs signaling and traffic

– two timing advance frames

– two idle frames (for neighbor list and power control)

– 12 x 4 +2 + 2 = 52 frames

0

Block 0 Block 1 Block 2TA

1 2 3 4 5 6 7 8 9 10 11 12 13

Block 3 Block 4 Block 5 I

14 15 16 17 18 19 20 21 22 23 24 25 26

Block 6 Block 7 Block 8TA

27 28 29 30 31 32 33 34 35 36 37 38 39

Block 9 Block 10 Block 11 I

40 41 42 43 44 45 46 47 48 49 50 51

TA - T im ing A lignm ent F ram eI - Id le F ram e



GPRS 52-Multiframe

• The PDCHs are mapped and organized into a 52-Multiframe

0 1 2 3 4 5 6 7 21 22 23 24 25.5

0 1 2 3 4 49 50 51

0 1 2 3 4 5 6 7 21 22 23 24 25

1 TDM A Frame4.615 ms


51 M ultiframe235.4 ms

Hyperframe3 h 28 min 53 s 760 ms

0 1 2 3 4 48 49 50

0 1 2 3 4 5 6 7 2043 2044 2045 2046 2047

0 1 2 3 4 5 6 7 46 47 48 49 50

0 1 2 3 4 23 24 25


51 x 26 Superframe or 26 x 51 Superframe or 25.5 x 52 Superframe6s 120 ms

0 1 2 3 4 5 6 7



GPRS Master-Slave Concept

BCCH CCCH

TS

Option 1 (use all PDCHs)

Option 2 (use BCCH or PBCCH)

Option 3 (use BCCH, CCCH or PBCCH, PCCCH)

PDTCH PDTCH PDTCHTA

PDTCH PDTCH PDTCH I PDTCH PDTCH PDTCHTA

PDTCH PDTCH PDTCH I

PCCCH PDTCH PDTCHTA

PDTCH PDTCH PDTCH I PDTCH PDTCH PDTCHTA

PDTCH PDTCH PDTCH I

PBCCH PDTCH PDTCHTA

PDTCH PDTCH PCCCH I PCCCH PDTCH PDTCHTA

PDTCH PDTCH PDTCH I2

4

6

3

5

7

1

0

• One physical channel (frequency and timeslot) can be used for signaling and control

• Remaining channels are used for GPRS traffic channels - PDTCHs

• If no master channels are used, GPRS will rely on GSM signaling channels

• As demand for voice increases, slave channels can be released

• If Master PDCH is released, mobiles must retune to GSM broadcast channel

Master Slave Concept



GPRS Timing Advance - Uplink

0 1

2 3

4 5

6 7

8 9

10 11

12 13

14 15

8 x 52-multiframe = 416 framesTAI = 0 - 15

• The PTCCH/U is divided into 16 subchannels with eight 52-multiframes

• The 16 subchannels can be assigned to 16 different active mobile stations

• Every PTCCH/U has a cycle of 1.92 s

• Active mobile stations will transmit one access burst with TA=0 to the BTS once per eight 52-multiframes within their subchannel

• Based on the PTCCH/U message, the BTS can recalculate the timing advance value



GPRS Timing Advance - Downlink

One TA message in 4 normal burstsfor up to 16 MS

0 1

3 4

• Each mobile is assigned a timing advance index (TAI) value via the PTCCH/D

• The TA message sent on the downlink can convey timing advance information for up to 16 mobile stations

• The timing advance message contains the TAI values associated with each mobile station

• Since the message requires 4 frames, it is carried within four consecutive TA frames



GPRS Timing Advance - Example

• Example: An uplink temporary block flow (TBF) is initiated between a mobile station and a serving base station. The total file size is 80 kilobits and is transmitted using CS-1. The base station assigns the mobile station a timing advance index (TAI = 3). Assuming a constant data rate and no block retransmissions, how many timing advance messages are required from the mobile during this transmission.

– 1 frame =

– 1 block =

– A 52-multiframe =

– Time between identical TAIs =

– Total transmission time =

– Number of timing advances =



GPRS Power Control - MS Power Classes• Power control is used to minimize the transmit power and still

maintain a reliable link

• GSM power control is done by the BTS based on RXLEV and RXQUAL

• GPRS power control is performed by the mobile based on several parameters including:

– Maximum allowed Tx power

– Received Signal Level - RSL

– Mobile station power class

• Several mobile station power classes have been defined for GSM 900 and DCS 1800 respectively

Mobile Station Power Class GSM 900

Mobile Station Power Class DCS 1800



GPRS Power Control - Power Control Calculation• The formula for power control calculation as defined by ETSI

(GSM 03.64 version 8.50)

)),48(min( max0

PCPch CH

= 39 dBm for GSM 900 and 36 dBm for DCS 1800

CH = mobile and channel specific power control parameter. It is sent to the mobile in any resource assignment message. The values range from 0 to 62 dB in 2 dB increments based on interference measurements of the BTS. At any time during a packet transfer, the network can send new CH values to the mobile on the downlink PACCH

= is a system parameter. Its default value is broadcast on the PBCCH. Furthermore, the mobile and channel specific values can be sent to the mobile together with CH

C = received signal level at the mobile

Pmax = maximum allowed transmit power in the cell



GPRS Power Control - Example

• A GSM-1800 Class 3 mobile station is engaged in power control. The network parameters are =0.5, and CH = 4. The mobile reported C is –85dBm. What is the transmit power Pch ?

)),48(min( max0

PCPch CH



Air Interface - Quiz!

• What are the different types of GPRS logical channels ?

– _______________

– _______________, _______________, _______________

– _______________, _______________, _______________

• GPRS packet data channels are mapped onto a new structure called ________________

• The Uplink PTCCH is divided into _____ subchannels

• One timing advance message on the downlink is transmitted over _____ normal bursts and contains a timing advance index for up to _____ users

• In GSM, power control is done at the ____________. In GPRS, power control is done at the _____________.



Class Agenda


• Protocol Stack

• Air Interface

• Mobility Management– Mobility Management States

– GPRS Attach

– Mobile Originated Transfer

– Mobile Terminated Transfer

– Cell Selection/Reselection






GPRS Mobility Management States

• Mobility management states apply for both the mobile and the SGSN

• Idle: Mobile is powered on but not attached to GPRS

• Standby: Mobile is powered on and attached to GPRS. No packet transfer is in progress. Routing area updates are sent as needed.

• Ready: The mobile is currently engaged in packet transfer or recently terminated a packet transfer. The Ready state is determined by a timer. No need to page a mobile in Ready state

GPRS Mobility Management States for MS


Idle

Ready

Standby

Ready-TimerExpiry

PDUTransfer

GPRSDetach

GPRSAttach

PDUTransfer


GPRS Attach Process

M S BTS

BSC SGSN

AirInterface

GbInterface

GsInterface

VLRH LRG R

DInterface

Attach Request

Authentication and Ciphering Authentication and Ciphering

Routing Area Update

Location Area Update

Attach Acknow ledged

For GPRS

For GSM

• Process of registration of the mobile into the GPRS network

• Occurs when mobile is first powered on and can occur afterwards based on network settings

• Mobile registers directly with the SGSN

• Information Exchanged

– IMSI or P-TMSI

– TLLI

– RA, LA

– Power class mark

– Type of registration (GSM, GPRS)

– Authentication

– Ciphering



GPRS PDP Context Activation

M S BTS

BSC SGSN

AirInterface

GbInterface

GnInterface

Request PDP Context Create PDP Context

PDP Context ActivatedPDP Context Granted

GGSN

Message Includes:§ IP Address (Static of Dynamic)§ Access Point-AP(ie yahoo.com)§ QoS§ NSAPI

Message Includes:§ IP Address (Static of Dynamic)§ Access Point-AP(ie yahoo.com)§ QoS§ Tunneling ID (TID)

Message Includes:§ IP Address (Static of Dynamic)§ UPD Protocol Header§ QoS§ Tunneling ID (TID)

Message Includes:§ IP Address (Static of Dynamic)§ Priority Level§ QoS§ Tunneling ID (TID)§ NSAPI§ GGSN Address

• The mobile need to activate a packet data protocol context before it can transmit or receive information



GPRS Mobile Originated Transfer

M S

Packet Channel Request

Packet Channel Request

Tw o Phase Access

BSS

Packet Immediate Assignment

One Phase Access

Packet Uplink Assignment

Packet Resource Request

Packet Resource Assignment

• A mobile initiates a transfer on the random access channel RACH or PRACH

• One phase access: Network provides immediate packet channel assignment message with reserved PDTCHs for uplink

• Two phase access: Network provides immediate packet channel assignment message with only one single radio block reservation. Mobile sends a more detailed packet resource request. Network responds with message that contains reserved resources



GPRS - TFI, USF and CV

• Temporary flow identity (TFI) and uplink state flag (USF) allow for multiplexing of several users on downlink and uplink directions respectively

• TFI is a 5-bit header that uniquely identifies a packet data transfer (TBF)

• The same TFI can be assigned to different PDCHs on the uplink and downlink

• USF is a 3-bit value (000 to 111), where 000 indicates “FREE”

• Each mobile listens to its assigned USF on the downlink and will transmit one or up to four blocks on the uplink depending on the amount of reserved blocks

• Uplink also contains a countdown value (CV) to indicate blocks remaining



GPRS Acknowledged/Unacknowledged Mode

BSS

Data Block

Data Block

Data Block

Data Block

Data Block

NACK Message

Block # 1 2 3 4Status 1 1 0 1

Bitmap

Erroneous Block

Retransmitted Block

M S

• RLC layer can be set to mode of operation

• Unacknowledged mode offers no means for error detection

• Acknowledged mode uses ARQ for error detection

• Message type ACK/NACK contains a bitmap of received blocks (UL/DL)

• Recipient sends ACK/NACK message after receiving a packet transfer

• Correct blocks are “1”, incorrect blocks are “0”

• Erroneous blocks are retransmitted

GPRS Mobility Management States



GPRS Mobile Terminated Transfer/Cell Reselection• Mobile terminated transfer

– The Countdown Value is used on the uplink to determine the end of a TBF

– The Final Block Indicator is used in the downlink to indicate the end of a TBF

• Cell reselection

– There are no handovers in GPRS, mobile performs cell reselection

– In GSM, cell reselections are performed when mobile is in idle mode

– GSM uses C1 and C2 algorithms for cell reselection

– GPRS Cell reselections can be network or mobile controlled

– GPRS uses C31 and C32 algorithms for cell reselection

– C31 is based on selecting the best GPRS server in the area

– C32 allows for cell ranking when HCS is implemented

– C31 and C32 allow for a more efficient cell planning of GPRS networks

– There are three modes of operation for cell reselection: NC0, NC1 and NC2



Mobility Management - Quiz!

• What are the different mobility management states ?

– _______________, _______________, _______________

• In order to register to the GPRS network, the mobile station must perform a ________________

• In order to engage in a packet transfer, the mobile station must perform a ________________

• The two options for mobile originated transfer are:

– __________________

– __________________

• For downlink multiplexing, the ________ is used

• For uplink multiplexing, the ________ is used

• Errors in transmitted blocks are notified to the transmitting party via the _____



Class Agenda


• Protocol Stack

• Air Interface


• Quality of Service– Precedence Class

– Throughput

– Delay Class

– Reliability Class





Quality of Service - Precedence Class• Under normal network conditions, all users have equal access.

• During network congestion, users with a higher priority level shall be served before users with a lower priority

• A user with lower priority will suffer higher delay times and packet losses

• Three precedence class are defined



Quality of Service - Peak Throughput• Peak throughput refers to the

maximum data rate for packets to be transferred across the network

• There is no guarantee that this maximum data rate can be achieved or sustained for any time period

• Peak throughput is measured in octets per second

• Values are shown in bits per second for easier clarification

• Network may limit the subscriber to the negotiated peak throughput regardless of additional capacity



Quality of Service - Mean Throughput• Average rate at which data

is expected to be transferred across the GPRS network

• Measured in octets per hour

• Displayed in bits per second for easier clarification

• GPRS network may limit the subscriber to the mean throughput regardless of additional capacity

• A best effort throughput can be negotiated based on need and availability



Quality of Service - Delay

• ETSI has defined the maximum values for mean delay and 95 percentile delay that a packet may encounter while transferred over the GPRS network

• Delay class does not include delays caused by networks outside the PLMN

• Delay is defined based on the transfer of a service data unit (SDU)

• Two SDU sizes are specified: 128 octets and 1024 octets



Quality of Service - Reliability



Quality of Service - Reliability

• Reliability class defines the probability of:

– Loss packets

– Out of sequence packets

– Duplicate packets

– Corrupted packets



Class Agenda

• Air Interface



• Optimization and RF Planning– GSM Metrics

– GPRS Metrics

– Measurement Model

– RF Performance, Signal Quality, Data Performance



• Conclusions



Network Optimization Process

• Identify RF and fixed network parameters that impact network performance

RxLev

RxQual

BCH Pwr

BLERC/I

ThroughputPacket Delay Re-Connects

DNS Lookup

Packet Failure

DriveTest

DriveTest

DataProblem

DataProblem

ProblemID

ProblemID

RFProblem

RFProblem

Evaluation

Evaluation

Actions

Actions



GSM Metrics - RXLEV and RXQUAL

• Reported as a quantized value RXLEV: RXLEV = RSL[dBm] + 110

• Minimum RXLEV: -110, MAX RXLEV = -47

• Downlink measurements for both serving cell and up to 32 neighbors

• Up to 6 strongest neighbors are reported back to BTS through SACHH

• Only on the serving channel

• Reported as a quantized value RXQUAL

• For a good quality call RXQUAL < 3

• Measurements are averaged before the handover processing

• If DTX is active, the measurements are performed over the subset of SACCH that guarantees transmission



GSM Metrics - C/I, Neighbor Lists and Call Stats

dBlog10/

1_

__

N

iiR

CellServingR

P

PIC

• Co-channel: Undesirable signal attributed to reuse of the same frequency

• Adjacent: Undesirable signal attributed to bleed over from frequency components

• Neighbor lists: Assigned based on strongest signals for handover purposes

• Call Statistics:

– Dropped Calls

– Blocked Calls



GPRS Metrics - Throughput

• Rate at which data is transferred in either uplink or downlink (kbps)

• Can be measured as raw or effective

• Different applications require different throughputs

0

2

4

6

8

10

12

14

16

Time

Th

rou

gh

pu

t (k

bp

s)

TX Throughput RX Throughput



GPRS Metrics - Throughput Example• A downlink TBF has been negotiated using CS-2.

Calculate the effective throughput if the negotiated reliability is Class 1, assuming that the probability of retransmitted blocks is 40%. Also calculate the raw throughput if the negotiated reliability class is Class 4 (no error protection). Refer to Section for the reliability classes.

0)](Re1[ RpR TXTX



GPRS Metrics - Reliability

• ETSI reliability classes allow the engineer to benchmark performance against different types of applications

• Optimizing the RF link is first step towards correcting packets

• Duplicate packets are usually due to problems in the IP network



GPRS Metrics - Reliability

• Drive test measurement equipment can easily compute the probability of blocks in error (BLER) received by a mobile

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

Time

C V

alu

e

0

10

20

30

40

50

60

70

80

90

100

BL

ER

C Value Rx BLER



GPRS Metrics - Delay

GPS

M S

BTS

BSC PCU SGSN GGSN

GiInterface

Test ServerDrive Test System

Send SDU w ith GPS timestamp

Server calculates delay and sends back to test mobile

GPS

R

ReferencePoint

• Delay is specified for two SDU sizes: 128 octets and 1024 octets

• Smaller SDUs travel faster and with less delay than larger SDUs

• A good method to measure delay is by configuring a test server at the Gi interface and timestamp each SDU with GPS measurements

• Delay can also be computed from any other node inside or outside the PLMN



GPRS Measurement Model

Measurement Model

DataPerformance

Signal QualityRF

Performance

ApplicationLayer

GPRS LayersTest Mobile

ReportsRF Scanning

Receiver

• Data Performance:

– Application layer end-to-end tests

– GPRS Layers information collected by the phone

• Signal Quality: Phone reported parameters

• RF Performance: Scanning Receiver



GPRS Measurement Model

ApplicationLayer

End-to-End Data Performance

GPRS Layers

Physical Layer

ApplicationLayer

GPRS Layers

Physical Layer

GPRS Layers Data Performance

RF Link Quality Performance

• Hierarchical layer diagram based on ISO/OSI reference model



GPRS Measurement Model• Collected measured data can be post-process and analyzed with

commercial tools

Agilent OPAS 32 Post-processing and analysis tool

Shows uplink & downlink application layer throughput along with coding schemes in use for each link



GPRS Measurements - BLER versus C/I

0.001

0.01

0.1

1

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

C/I

BL

ER

CS1 CS2 CS3 CS4

• Block Error Rate (BLER) can be directly tied to the quality of the RF link, typically measured in terms of C/I



GPRS Measurements - BLER Example• Calculate the effective Rx throughput for a mobile

station that operates under C/I of 10dB and uses coding scheme CS-1. How long will it take to download a 150Kb data file?

0)](1[ RBLERpRRX

• Total Download Time =



GPRS Measurements - Signal Quality

Layer 1Radio

Resource(RR Info)

RLC / MACLayer

LLC / SNDCPLayers

GMM / SMInformation

BCCH TCH - ARFCN Multislot ClassAck/Unack

Mode

Service State(Idle, Standby,

Ready)

BSIC MAIONumber ofTimeslots

SAPIP-TMSI, TLLI

values

RXQUAL HSN MS Output Power Ciphering InfoRouting Area

Identifier

RXLEV MA List Ack/Unack ModeHeader

Compression

SM state(PDP active,inactive, etc.)

TimingAdvance

Coding SchemeData

CompressionTx Power TFI numberNeighbors TBF status

• Phone reported measurements include Layer 1, Layer 2 and Layer 3 parameters

• Provide valuable information about the performance of the network



GPRS Measurements - Drive Test Tool• Commercial GPRS tools can collect most GPRS related information

Agilent E7475 GPRS Drive Test Software



GPRS Measurements - Data Performance

Type of service Conversational Streaming Interactive BackgroundDelay Tolerance Low High Medium HighJitter Tolerance Low Low Medium High

Data raterequirement

Small to large High Low to medium Low

Data symmetry Symmetrical Asymmetrical Asymmetrical AsymmetricalReliabilityTolerance

High High Low Low

TypicalApplications

Circuit switchedtelephony

Audio-videobroadcasting

E-commerceand WWW

File transferand e-mail

• GPRS measurements provide information below the application layer and allows the engineer to detect the cause of problems that are hidden to the user

• Application layer measurements describe the performance that the user perceives depending on the application being tested

• Real-time applications can be simulated and tested



GPRS Measurements - End-to-End Process

Test Server

GPRS Netw ork

GiInterface

M SDrive Test System

• End-to-end test process is best approach towards measuring performance at the application layer

• Client - Server configuration

• On the uplink, the mobile sends packets over the GPRS network. A test server measures the performance and reports results back to the mobile

• On the downlink, the test server sends packets over the GPRS network. The test mobile measures performance and stores the results



GPRS Network Optimization Challenges• GPRS deployment is still in its beginning

stages

• Many questions regarding the performance metrics are yet to be answered

• As networks grow and more solutions arise a more defined methodology will be developed

• As of today, GPRS radios are not capable of frequency hopping

• Many GSM networks are already suffering congestion problems with voice traffic. GPRS will add more to the problem

• Today only Class B mobiles are available commercially

• Only coding schemes 1 and 2 are being implemented in trials

Sagem OT 96MGPRS

Motorola GPRS Timeport



Network Optimization - Quiz!

• What are some GSM performance metrics ?

– _______________, _______________, _______________

• What are some GPRS performance metrics?

– ______________,________________,________________

• Packets in error can be

– ______________

– ______________

– ______________

– ______________

• The GPRS measurement model tests for

– ______________

– ______________

– ______________



Class Agenda

• Protocol Stack

• Air Interface




• Traffic Planning– Estimation of GPRS Data Capacity


• Conclusions



Traffic Planning in GPRS

• GPRS over GSM creates a mixture of traffic types - voice & data

• Peak combined traffic does not necessarily coincide with either voice or data busy hour

Total traffic

D ata traffic

Voice traffic

Tota l peak traffic

Peak voice traffic Peak data traffic

T im e

Traffic volum e




• Proper dimensioning of GPRS over GSM requires:

– Peak circuit switched traffic in erlangs

– Peak data traffic in Kb/sec

– Circuit switched traffic load during total peak

– Packet switched traffic load during total peak

• Coding scheme usage depends on quality of radio channel

• The lower the coding scheme the higher the protection

• Traffic dimensioning assumes high loading and high interference, therefore CS-1 is used for estimates



Traffic Planning in GPRS - Example

• Consider a GSM/GPRS base station designed to support the aggregate data throughput of 40Kb/sec using coding scheme CS-1. Assume that 50% of users with the cell site's coverage area operate under favorable RF conditions that allow them to use coding scheme CS-2. Estimate the aggregate throughput that can be supported by the base station.

• The aggregate throughput can be calculated as:

Kb/sec_________aggR



• A GSM radio can hold eight timeslots

• Some of the timeslots are dedicated for signaling

• One trunk in GSM is defined as one timeslot on the radio transceiver

• Based on number of trunks and required Grade of Service (GOS), the amount of traffic loading can be calculated using the traditional Erlang B traffic model

Number oftransceivers

Number of timeslots available for

traffic

Voice capacity atGOS of 1% [E]

Voice capacity atGOS of 2% [E]

1 6 1.91 2.282 14 7.35 8.203 22 13.65 14.904 30 20.34 21.93



• To estimate the maximum aggregate data traffic that can be supported per GSM/GPRS sector, the following is assumed:

– Coding scheme is CS-1

– Threshold throughput per time slot is 5Kb/sec

– Dominant type of data service is WWW browsing with Pareto distribution

• Average throughput per timeslot can be calculated as

sqqs

sav TT

R

TT

TRR

10

0


• Where

– Rav = Threshold throughput

– R0 = Data rate of coding scheme

– Ts = Service time

– Tq = Waiting time in queue



• Using Allen-Cunneen’s formula and the Pareto characteristics of different data traffic types, we can estimate the erlang data capacity of a GPRS site


21

0

200

20

1

11

2

1

2

,1

n

m

nm

n

mDD

DDC

av xx

xx

x

x

nn

n

aC

aCE

R

R

• Where

– = shape parameter for the Pareto distribution

– = minimum message length

– = maximum message length

– = average data traffic load in erlangs

– = average number of time slots available for GPRS service,

– = Erlang C delay formula DDC aCE ,

DC

n

mx


Traffic Planning for GPRS

• Typical values of the Pareto distribution shape parameter

• To illustrate the traffic dimensioning concept, consider the following set of parameters


Traffic Planning for GPRS

• Using the previous equation and the information from the previous tables, the following information can be computed

• The information from the table below generates the curves shown to the right 0

20

40

60

80

100

120

140

160

180

200

220

240

0 5 10 15 20 25 30 35

Circuit switched traffic [erlang]

Ag

gre

gat

e G

PR

S t

hro

ug

hp

ut

[Kb

/sec

]

1 TX (6 TS) 2 TX (14 TS) 3 TX (22 TS) 4 TX (30 TS)

GOS of 2%

GOS of 1%


Traffic Planning in GPRS - Example

• Determine the number of GSM radios at the GSM/GPRS site required to support at least 7.5 erlangs of voice traffic at 2% GOS and an aggregate CS-1 packet data throughput of 80Kb/sec. If 50% of the users are in area of C/I that allows for CS-2 coding, what is the available aggregate throughput?

0

20

40

60

80

100

120

140

160

180

200

220

240

0 5 10 15 20 25 30 35


Ag

gre

ga

te G

PR

S t

hro

ug

hp

ut

[Kb

/se

c]

1 TX (7 TS) 2 TX (14 TS) 3 TX (22 TS)

(9.7 E, 80 Kb/sec)

(7.5 E, 95 Kb/sec)


Kb/sec_________aggR

• The aggregate throughput can be calculated as:


Traffic Planning in GPRS - Case Study• Consider a GSM provider trying to role out the GPRS service within

urban core area. We will assume that the traffic is following a fairly uniform geographical distribution and that the most dominant traffic type is WWW browsing. Other relevant data is given below:


• Determine the following:

– Number of sites necessary for handling the circuit switched voice at 2% GOS

– Aggregate GPRS capacity per site (for CS-1 coding scheme)

– If the system is to provide aggregate capacity of 2.5Mb/sec while serving the peak voice traffic load, how many sites need to be installed?


Traffic Planning in GPRS - Case Study• Analysis:

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14


Ag

gre

ga

te G

PR

S t

hro

ug

hp

ut

[Kb

/se

c]

GPRS Throughput Curve for 2TX

95.5v

D

A

R


ARFCNN

CELLN

aggR

vCELL aN

DCELL RN

£v

D

a

R

CELLN aggR


Class Agenda

• What is GPRS?


• Protocol Stack

• Air Interface






• Conclusions



HSCSD, EDGE and 3G Growth Path

EDGE

SMS, Data (9.6Kbit/s)

UMTS

2 Mbit/s

GPRS

171.2 kbit/s

HSCSD

60 kbit/s

Bandwidth

Technology

384 kbit/s

9.6 kbit/s

1997 1998 1999 2000 2001 2002 2003



HSCSD, EDGE and 3G Growth Path

G SM 2+9.6 Kb/sec

HSCSD64 Kb/sec

G PRS114 Kb/sec

EDG E384 Kb/sec

UM TS2M b/sec

19993Q

20001Q

20011Q

20022Q

2003

T im eline

D ataR ates

HSCSD - H igh S peed C ircu it Sw itched D ata

G PRS - G enera l P acket R ad io S ystemEDG E - Enhanced D ata G SM Environm ent

UM TS - U n iversa l M obile Te lephone S ervice

GPRS160 kbps

EDGE384 kbps

UMTS2 Mbps

HSCSD64 kbps

GSM 2+9.6 kbps

• High Speed Circuit Switch Data

– Existing GSM structure

– Combines multiple TS

– Software upgrade at BTS

• Enhanced Data for GSM Evolution

– Uses 8PSK modulation

– Provides higher data rates than GPRS

– Major changes to GSM

• UMTS - FDD

– 3G solution for GSM

– Up to 2Mbps data rates


Documents

Gprs 1