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Enhanced Data Rate for GSM EvolutionEDGE

EDGE

Presentation for the

New Employees in ZTEMAY 2004

Presented by:

Zong Baiqing

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Contents

GPRSIntroductionBuilding blocks of a GPRS networkOperation

Interfaces between componentsQoSBenefits & ApplicationsSummary

EDGE

ArchitectureModulation & Coding SchemesPhysical Layer ParametersEDGE Normal Burst StructureLine Quality Control

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Migration to 3G

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GPRS

General Packet R adio Service

Part I

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Introduction

General Packet Radio Service

A standard from ETSI and others on packet data in GSM systems

Packet-data standard for TDMA/136 systems

Uses a packet-mode technique to transfer data in an efficient manner

Optimizes the use of network and radio resources

Maintains strict separation between the radio subsystem and networksubsystem

Offers air-interface rates up to 115 KbpsSupports multiple types of mobile terminals

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Implemented on the GSM structure

Addition of two network nodes,

Serving GPRS Support Node (SGSN)

Gateway GPRS Support Node (GGSN)

In addition a number of devices from the Internet Protocol (IP)

Building B locks

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MT, MS : Mobile Terminal, Mobile StationBSC : Base Station Controller SMSC : Short Message System Center HLR : Home Location Register

MSC : Mobile Switching Center VLR : Visitor Location Register

Building B locks ( ContD )

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IDLE StateThe subscriber is not attached to the GPRS mobility management.The MT and SGSN context hold no valid location or routing information for the subscriber.Data transmission to and from the mobile subscriber,

as well as the paging of the subscriber, is not possible.The GPRS MT is seen as not reachable in this case.

STAN D BY State

The subscriber is attached to GPRS mobility management.The MT and SGSN have established MM contexts for the subscriber.Pages for data or signalling information transfers may be received.Data reception and transmission are not possible in this state.

RE AD Y StateThe SGSN MM context corresponds to the STANDBY MM contextextended by location information for the subscriber on cell level.The MT is ready for data transmission.

Mobility Management ( MM )

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Cl ass A GSM / GPRS

GSM & GPRS networks are attached simultaneously.

User can receive GSM (voice, data, SMS) and GPRS (data)services together.

Cl ass B GSM / GPRS

Similar to Class A without simultaneous option.

If one service (GSM or GPRS) is ON, then the other is OFF.Cl ass C GSM or GPRS

Mobiles having both GPRS & GSM functions like Class A & Bexcept attaching to one of the networks one at a time.

Today mostly Class B mobiles are produced...

Mobile C lasses

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1. MT requests to be attached to the network. This request is sent to theSGSN. Including the information whether it wants to attach to a packet-switched service or a circuit-switched service

2. This is followed by an authentication request made between the MT and theHLR

3. In the third step, subscriber data from the HLR is inserted into the SGSNand the MSC/VLR

4. Finally the SGSN informs the MT that it is attached

GPRS Attach

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The MT must establish a PDP context to enable communication.

This activation process involves five major steps

1. MT requests a PDP context activation from the SGSN

2. The SGSN validates the request based on the informationreceived from the HLR during the GPRS attach process

Packet Data Protocol ( P D P ) Context Activation

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3. The access point name is then sent to a DNS to identify the IP address of the GGSN to which the SGSN will send data. This DNS can be integratedinto SGSN or another server on the GPRS backbone network

4. This is followed by establishing a logical connection between the SGSN andthe GGSN, a connection known as GPRS Tunneling Protocol (GTP).

5. At last, an IP address is assigned to the MT

This IP address could be dynamic, assigned by the GGSN

or static assigned by the HLR

PDP Context Activation ( Contd )

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Data transmission in a GPRS network follows a layered protocol structure,

Subnetwork Dependent Convergence Protocol (SNDCP) Layer The Logical Link Control (LLC) Layer The RLC/MAC Layer Base Station System GPRS Protocol (BSSGP) Layer Network Service (NS) Layer The SGSN requires support for the GTP Layer

Data Transmission Layers

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Air Interface

BCH : Z eroth slot reserved for GSM Broadcast ChannelC S : Circuit Switched Timeslots

P- D ata : Packet Data

PB CH : Packet Broadcast Channel

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Logical Channels

P CCH : Packet Common Control

PRACH : Packet Random Access

PPCH : Packet Paging

PAGCH : Packet Access Grant

PNCH : Packet Notification

PB CCH : Packet Broadcast Control

P D TCH : Packet Data Traffic

PA CCH : Packet Associated Ctrl.

PT CCH : Packet Timing Adv. Ctrl.

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1. SGSN informs MS by sending a detach request

2. SGSN requests from the GGSN to delete the MS PDP context.The GGSN responds to the request

3. SGSN sends a signal to MSC/VLR to remove the association with theSGSN

4. MS could send a detach accept message after receiving the request fromthe SGSN

GPRS Detach

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The Security function provides three main benefits:Guarding against unauthorised GPRS service usageProviding user identity confidentialityProvides user data confidentiality

Procedure :

1. SGSN sends authentication information to the HLR.2. The HLR responds with an acknowledgment.3. SGSN request MS for ciphering.4. The MS responds5. The MS starts ciphering

6. The SGSN starts ciphering

Security

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Coordination of GPRS & GSM Functions

Mode I

Mobile monitors one of the channels for paging during GPRS attach.

Network sends paging through one of the channels.

ModeII

GPRS/GSM common channel is used for both services

paging

Mobile has to monitor only common channel paging

Mode III

Mobile monitors both channels for paging during GPRS attach

Network sends circuit-switched paging via common channel andGPRS paging via GPRS paging channel.

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Associated with each PDP context

Considered to be a single parameter with multiple data transfer attributes.

Defined in terms of :

Precedence classDelay class

Reliability class

Peak throughput class

Mean throughput class

QoS parameters are mapped to the data network

Q oS

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Charging is a split function between the SGSN and the GGSN

The SGSN collects

Usage of the radio interfaceUsage of the PDP addresses

Usage of the general GPRS resources

The GGSN collects

Destination and source addressesUsage of the external data networks

Usage of the packet data protocol addresses

Location of MS within the network

Charging

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Packet Switched; Always ON, Cost per Data

Allows the network subsystem to be reused with other radio accesstechnologies

The infrastrucuture deployed could easily support broad-band mobilewireless technologies like UMTS

Does not mandate changes to an installed MSC baseAllows efficient use of radio and network resources

GPRS Benefits

GPRS ApplicationsInformation

News, Sports results, Stocks and Financial information....Database inquiry (including location)

White Pages, Yellow Pages, Corporate Directory, Personal Directory(including Directory Dialling), Market: Buy /Sell /Rent /Jobs...

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Efficient wireless access to external IP networks

Requires the introduction of the SGSN and GGSN

Negligible resource consumption by userswho are connected but are not exchanging data

Rates up to 115 kbps are supportable

Summary

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EDGE

E nhanced Data Rate for GSM E volution

Part II

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Introduction

Enhanced Data Rate for GSM Evolution

High data rates are expected from the Third-Generation (3G)

A stepwise way in the direction of 3G

Allowing existing cell plans to remain intactPreparing customers/users for the 3G services.

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Standardization

Introduced to the ETSI for the first time in 1997

EDGE is standardized by ITU and 3GPP

Global Standard

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EDGE & GSM/GPRS

EDGE is a further development of the GSM data services HSCSD and GPRS

It is suitable for circuit-switched and packet-switched services

Enhanced Circuit- S witched Data ( ECSD ) is the Circuit-Switched

Enhanced GPRS (EGPRS ) is the packet oriented partThe major changes over GSM standard are made in the radio interface .

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Architecture

SGSN

GGSN

External IPNetwork

PSTN/ISDN

GPRSregisters

HLR

VLR

MSC

G nInterface

A interface

Abisinterface

Elements Modified by ED G E

MS C

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Modulation & Coding Schemes (1 )

8-PSK is used which coexist with existing GMSK

Modification mostly concern the RLC/MAC and Physical Layers

New EDGE transceiver unit and software upgrades are introduced

Handles standard GSM/GPRS traffic

Automatic switching to EDGE mode when needed

Modulation GMSK 8PSK

Symbol Rate 270 kSymbols/s 270 kSymbols/s

Bits per Symbol 1 bit per symbol 3 bits per symbol

Modulation Bit Rate 270 kbits/s 810 kbits/s

Max Users Data Rate per TS 20 kbit/s for CS4 59.2 kbit/s for MCS9

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8-PSK Symbol Constellation

(0, 1, 0)

(0, 0, 0) (0, 1, 0)

(0, 0, 1)

(1, 1, 1)

(1, 1, 0)

(1, 0, 0)

(1, 0, 1)

I

R

8-PSK Modulation

The EDGE modulator rotates the phase of each modulating symbol bymultiples of 3 /8 during every symbol period.

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Modulation & Coding Scheme Parameters

EDGE provides 9 different MCS

It is possible to switch a connection between different schemes

Each MCS is designed to deliver the optimal throughput under differentradio environments C/I and C/N

Carrier-to-Interference ratio (C/I)Carrier-to-Noise ratio (C/N)

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Modulation & Coding Scheme Parameters

MCS Modulation Code Rate Header Code RateData (bit)

per Radio Block Family BCS TailData Rate

(kbps)MCS 8-PSK 1.0 0.36 2x592 A 2x12 2x6 59.2

MCS 8-PSK 0.92 0.36 2x544 A 2x12 2x6 54.4

MCS 8-PSK 0.76 0.36 2x448 B 2x12 2x6 44.8

MCS 8-PSK 0.49 1/3 592 (544+48) A 12 6 29.6 (27.2)

MCS 8-PSK 0.37 1/3 448 B 12 6 22.4

MCS GMSK 1.0 0.53 352 C 12 6 17.6

MCS GMSK 0.80 0.53 296 (272+42) A 12 6 14.8 (13.6)

MCS GMSK 0.66 0.53 224 B 12 6 11.2

MCS GMSK 0.53 0.53 176 C 12 6 8.8

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Physical Layer Parameters

D escription ED GE GSM

Modulation 8-PSK, 3 bit/sym GMSK, 1 bit/symSymbol Rate 271 kbs 271 kbs

Payload per Burst 346 114

Gross rate per Time slot 69.2 22.8

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GSM vs. EDGE Burst Structure: Normal burst

Tailbits Data bits Training Sequence Data bits Tail bits Guard Period bits

3 58 (incl. 1 stealing flag) 26 bits 58 (incl. 1 stealing flag) 3 8. 2 5

TailSym Data Sym Training Sequence Data Sym Tail Sym Guard Period Sym

3 58 (incl. 1 steal ing flag) 26 Sym 58 (incl. 1 steal ing flag) 3 8. 2 5

GSM: 156.25 symbols (156.25 bits)

EDGE: 156.25 symbols (468.25 bits)

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Link Q uality Control (L QC)

Different Modulation & Coding Schemes are optimal during different

situations depending on the link quality.

LQC is a technique used to adapt the channel coding of the radio link to the

varying channel quality.

LQC is performed in EDGE through:

Fast Power Control

Link Adaptation (LA)

Incremental Redundancy (IR)

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LQC : F ast Power Control

In-band signaling of measurement data and power control commands allows

the BTS to control the MS within 20ms steps, which is rather enhanced

compared to old GSM.

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LQC : LinkAdaptation (L A) - 1

Provides a dynamic switching between coding and modulation schemes

according to the time varying link quality

The network automatically adapts the coding scheme according to

the radio link quality.

This adaptation is done automatically for the downlink, and the network

commands the mobile station to use the optimum MCS for the uplink.

In order to perform this adaptation, the mobile station (for downlink transfer)

and the base transceiver station [BTS] (for uplink transfer) carry out the radio

Link Quality Measurements ( LQM)

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LQC : LinkAdaptation (L A) - 2

The LQC consists of the mean bit error probability (MEAN-BEP) and the

coefficient of variance of the bit error probability (CV-BEP)

The measurements are performed on every radio block and can be reported

back to the network for filtering and triggering of MCS changes withimproved reactivity and accuracy compared to GPRS

The link quality measurements provide an excellent indication of the radio

environment and, in particular, the C/I and C/N

With the knowledge of the estimated C/I, the networks can trigger MCSadaptation to deliver the maximum throughput for the environment

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LQC : LinkAdaptation (L A) - 3

Throughput versus C/I for each MCS

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LQC : Incremental Redundancy (IR) - 1

EDGE uses Hybrid ARQ of type II or Incremental Redundancy ( IR).

In a classical ARQ scheme (like the one used in GPRS)

The data at the transmitter is split into consecutive blocks.

In each block, the user data are encoded by adding some redundancy

using convolutional coding, and completed by a header and trailer.

A cyclic redundancy check (CRC) checksum is added in order to

guarantee the integrity of the received data after decoding.

After decoding if the data has not been correctly received, the receiver provides feedback to the transmitter using acknowledgement requesting

retransmission of the incorrectly received data blocks.

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LQC : Incremental Redundancy (IR) - 2

InIR, the redundancy added to the data is not the same at eachretransmission

Data is first sent with little redundancy.

Successful decoding - yields a very high user bit rate.

Unsuccessful decoding- Further redundancy is transmitted

PS-1 is used at first and if decoding is unsuccessful, PS-2 will be used andso on...

Soft values for unsuccessfully transmitted data blocks are stored and usedby combining them with the next retransmitted block's soft bits and increasethe chances for successful decoding

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Enhanced Q oS

EDGE is part of the (3GPP) Release 99 (Rel99) specifications, which

provides QoS enhancements to a wireless system. These include:

Rel99 introduces new QoS parameters in the QoS profile, which allows

a differentiation between different types of traffic (conversational,

streaming, interactive and background).

Rel99 also introduces the concept of packet flow context (PFC) and

associated procedures (creation, modification, and deletion), which

result in the negotiated QoS for a PDP Context.

Based on these enhancements, Rel99 offers a real end-to-end QoS solution

for GPRS/EDGE that is comparable to the way UMTS handles resources.

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GPRS/EDGE

Thank you!