EDGE Overview

5/22/2018 EDGE Overview

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EDGE Overview


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EDGE = Enhanced Data Rates for GSM (or Global) Evolution

Enhancement results from introduction of new modulation (8-PSK)+ channel coding schemes

ECSD (Enhanced Circuit Switched Data): circuit switched channels/ services EGPRS (Enhanced GPRS): packet switched channels/ services

New modulation triples the nominal bit rates

Update of the GSM Standard towards 3rd generation

networks/mobiles

What is EDGE?


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EDGE and 3G

The IMT-2000 3rdgenerationrequirements arefulfilled with EDGEtechnology, excluding2 Mbit/s indoorrequirement

Operators who do notget/want 3G-license

(UMTS/WCDMA) canprovide 3G-services

Gradual networkupdate with relativelow investments oninfrastructure


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New modulation: 8-PSK

(0,0,1)

(1,0,1)

(d(3k),d(3k+1),d(3k+2))=

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

(0,1,1)

(1,1,1)

(1,1,0)

(1,0,0)

8-PSK (Phase Shift Keying) hasbeen selected as the new

modulation added in EDGE

Non-constant envelopehighrequirements for linearity of thepower amplifier

Because of amplifier non-linearities, a 2-4 dB powerdecrease (back-off) is typically

needed

3 bits per symbol Symbol rate and burst length

identical to those of GMSK

EDGE GSMModulation 8-PSK, 3bit/sym GMSK, 1 bit/sym

Symbol rate 270.833 ksps 270.833 ksps

Payload/burst 342 bits 114 bits

Gross rate/time slot 68.4 kbps 22.8 kbps


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8-PSK Tx Power Reduction compared to GMSK Tx

GMSK

8PSK

Time

Envelope (amplitude)

Time

Envelope (amplitude)

Peak to Average of 3,2 dB

Pin

Pout

Back Off= 2 dB

Compression point


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EDGE in GSM/GPRS network

8-PSK coverage

EDGE capable TRX,GSM compatible

GMSK coverage

A-bis

BTS

BTS

MSC

Gn

GGSN

EDGE capableterminal,

GSM compatible

More capacity in interfacesto support higher data usage

GbBSC

A

SGSN

EDGE functionality in

the network elements


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EDGE vs GPRS

EDGE Benefits

EGPRS link level performance

EGPRS vs GPRS bitrates

Coverage comparison


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EDGE vs GPRSBenefits

EGPRS is the same as GPRS but with an enhanced radio interface (EDGE)

Same GPRS architecture and protocols Same mobility management Similar Radio Resource Management as GPRS

But... Enhanced RLC/MAC protocol:

Longer RLC windows

Enhanced re-transmission mechanism Incremental Redundancy

Retransmissions can be performed in different MCS from the original Better Link performance New requirements are needed in the Abis and Gb interfaces

Higher bitrates do not fit into Abis 16kbps channels throughputs

The Dynamic Abis Pool is a shared extra Abis resource for EGPRSchannels and TRXs


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EGPRS link level performance

EGPRS - TU3 noFH

0

10

20

30

40

50

60

0 5 10 15 20 25 30

CIR [dB]

Through

putperTSL

(Kbps)

MCS1 to MCS9

No IR

IR

EGPRS - TU3 noFH

0.001

0.010

0.100

1.000

0 5 10 15 20 25 30

CIR [dB]

BLER

MCS1 to MCS-9

Link Adaptation will select the (M)CS that maximizes SE whileachieving the user QoS requirements

Link Adaptation takes into account IR


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GPRS & EGPRS Coding Schemes

coding

scheme

modulation RLC blks /

radio blk

FEC

code rate

user bits /

20 ms

bit rate

(bps)CS-1 1 0.45 160 8,000

CS-2 1 0.65 240 12,000

CS-3 1 0.75 288 14,400

GPRS

CS-4 1 n/a 400 20,000

MCS-1 1 0.53 176 8,800

MCS-2 1 0.66 224 11,200

MCS-3 1 0.85 296 14,800

MCS-4

GMSK

1 1.00 352 17,600

MCS-5 1 0.38 448 22,400

MCS-6 1 0.49 592 29,600

MCS-7 2 0.76 448+448 44,800MCS-8 2 0.92 544+544 54,400

EGPRS

MCS-9

8-PSK

2 1.00 592+592 59,200

TS 03.64 Bit rate excluding RLC/MAC headers


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0

10

20

30

40

50

60

1 2 3 4 5 6 7 8 9 10 11

Pathloss distance [km]

DLThrough

putperTSL[Kbps]

EGPRS

GPRS CS1-2

GPRS CS1-4

Path loss [dB]120.8 132.1 138.8 143.5 147.1 150.1 152.6 154.8 156.7 158.4 160.0

EGPRS coverage compared with GPRS

L= 40(1-4x10-hb)Log10(R) -18Log10(hb) + 21Log10(f) + 80 dB.

Relationship between path-loss and distance given by Okumura-Hata based-formula:

Averagegain: 3.6

Averagegain: 2.3 Es/No=8.3 dB

Es/No=42.3 dB


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EDGE description

Modulation & Coding Schemes

EGPRS Channel Coding

EGPRS MCS families

Segmentation and ARQ

Retransmission mechanisms


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EGPRS Coding Schemes

Portion of data and coding varies in different coding schemes

the more coding the more errors can be corrected in the radio interface

data coding

Radio interface block (1392 bits in 8-PSK)

Scheme

Modulatio

n

Raw

data in

block

(bits)

Raw

data in

block

(octets) Family

Data rate

(kbit/s)

MCS-9 8-PSK 2x592 2x74 A 59.2

MCS-8 8-PSK 2x544 2x68 A 54.4

MCS-7 8-PSK 2x448 2x56 B 44.8

MCS-6 8-PSK 592 74 A 29.6

MCS-5 8-PSK 448 56 B 22.4MCS-4 GMSK 352 44 C 17.6

MCS-3 GMSK 296 37 A 14.8

MCS-2 GMSK 224 28 B 11.2

MCS-1 GMSK 176 22 C 8.8

PCUBTS

EGPRS


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EGPRS Modulation and Coding Schemes

EGPRS has nine basiccoding schemes, MCS-1...9.

In general, a higher codingscheme has higher codingrate, and consequently higherpeak throughput, but it alsotolerates less noise orinterference.

The figure shows throughput

vs. C/I of EGPRS codingschemes in TU50iFH, withoutincremental redundancy.

The basic unit of transmissionis radio block (= 4 bursts = 20ms on average), whichcontains one or two RLCblocks.

0

10

20

30

40

50

60

0 5 10 15 20 25 30

MCS-1

MCS-2

MCS-3

MCS-4

MCS-5

MCS-6

MCS-7

MCS-8

MCS-9


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EGPRS Channel Coding

EGPRS channel coding consists

of separate data and headercoding, as shown in the figurefor MCS-9 downlink.

Coding of data part: Data part includes user

data, two bits from RLC header, BCS(block check sequence)and tail bits.

Coded using 1/3 convolutional code.

Punctured with a selectable puncturingscheme (P1, P2 or P3). Two separate data parts for MCS-7...9.

Header part: Includes RLC/MAC header information

and information on the coding of thedata part (like used puncturingscheme).

Convolutional coding + puncturing.

USF

encoded USF P2 P3

P1 P2 P3

puncturing puncturing

puncturing

1st burst 2nd burst 3rd burst 4th burst

1/3 tailbiting

convolutional codingblock

coding

P1

header FBI+E data 2 BCS tail

1/3 convolutionalcoding

FBI+E data 1 BCS tail

1/3 convolutional

coding

mother code

mother code

protectedheader


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EGPRS MCS families

37 octets 37 octets 37 octets37 octets

MCS-3

MCS-6

Family A

MCS-9


MCS-2

MCS-5

MCS-7

Family B

22 octets22 octets

MCS-1

MCS-4

Family C

34+3octets34+3octets

MCS-3

MCS-6Family Apadding

MCS-8


The MCSs are divided into different families A,B andC.

Each family has a different basicunit of payload: 37(and 34), 28 and 22 octets respectively.

Different code rates within a family are achieved bytransmitting a different number of payload unitswithin one Radio Block.

For families A and B, 1 or 2 or 4 payload units aretransmitted, for family C, only 1 or 2 payload unitsare transmitted

When 4 payload units are transmitted (MCS 7, MSC-8 and MCS-9), these are splitted into two separateRLC blocks (with separate sequence BSN numbersand BCS, Block Check Sequences)

The blocks are interleaved over two bursts only,

for MCS-8 and MCS-9. For MCS-7 the blocks are interleaved over four

bursts


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EGPRS Dynamic Abis

GSM/GPRS Abis description

New EGPRS requirements for Abis

Dynamic Abis description

Dynamic Abis pool management, features and limitations


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The GSM/GPRS Abis Interface (1/3)

The Abis interface is situated between the BSC and the Base Station sites

The Abis interface is also used for GPRS services.

In a traditional GSM/GPRS system, each TRX channel is mapped statically to AbisPCM timeslots

AbisBSC

SGSNBTS

Um Gb

PCU


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New Requirements for EGPRS

In the air interface, higher rates are achieved through the use 8-PSK. Achievabletransmission rates are in the order of 59.2 Kbit/s per Radio Timeslot (RTSL)

Higher data rates dont fit in 16 kbit/s A-bis channels 32, 48, 64 or 80 kbit/s Abis links are needed Fixed Abis allocation of such links would be expensive and would lack flexibility

The Dynamic Abis Pool is a shared extra Abis resource for EGPRS channels andTRXs

The Dynamic Abis functionality allocates Abis transmission capacity to cells when

needed instead of reserving full fixed transmission link per TRX


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Dynamic Abis (1/3)

PCU frame types PCU data frame

Used when TRX not in EDGEmodeOnly able to carry CS1 and CS2

PCU master data frameUsed when TRX is in EDGE modeCarries CS1 or MCS1 on its ownand CS2-4 and MCS2-9 with thehelp of slave frame(s)

Includes pointers to the slaveframes PCU slave data frame

Carries additional data that doesnot fit in PCU master data frames

MCS-1 M

M

M

M

M

M

M

M

M

S

S

S

CS-4

CS-3

CS-2

CS-1

MCS-2

MCS-3

MCS-4

MCS-5

MCS-6

MCS-7

MCS-8

MCS-9

S

S

S

S

S

S

S

S

S

MM

M

M

S

S

S

S

S

S

S

S

CS-2CS-1

D

D

non-EDGE TRX

EDGE TRX

D

M

S

PCU data frame

PCU master data frame

PCU slave data frame

+

+

+

+

+

+

+

+

+

+

+

retrans M


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Dynamic Abis (2/3)

Fixed channels and EDAP For each GPRS radio timeslot on each

EDGE TRX, one fixed 16-kbps channelis allocated on the Abis for the transferof PCU master data frames

PCU slave data frames are allocated ina common pool, the EDAP (EDGEDynamic Abis Pool)

We are still going to make a staticallocation of 16 kbit/s per TCH, (used for

voice or data) In a PSD call, this sub-TSL is called amaster Abis channel, and if required, thesystem can allocate up to 4 extra slave

Abis sub-TSLs for same master fromdynamic pool

TS Bits used in timeslots

1 2 3 4 5 6 7 8

1

23

4

5

67

8

9

10

11

1213

14

15

16

1718

19

20

21

222324

Master

Slave

Reserved

Dynamic Abis Pool


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Dynamic Abis (3/3)

Dynamic Abis pointers Each downlink PCU master data frame

includes a pointer to downlink slaveframes on the same block period, and apointer to uplink slave frames on thenext block period

M M

S S S

S S S S

downlink PCMframes during

one block period

uplink PCMframes during

next block period


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Transmission Requirements for EGPRS MCS

Abis PCM allocation (fixed + pool)Coding Scheme Bit rate (bps)

CS-1 8,000

CS-2 12,000

CS-3 14,400

CS-4 20,000

MCS-1 8,800

MCS-2 11,200

MCS-3 14,800

MCS-4 17,600

MCS-5 22,400

MCS-6 29,600

MCS-7 44,800

MCS-8 54,400MCS-9 59,200

Slave Groups

CS-2 requires one Abis slave channel when the GPRS TBF is in EGPRS territory


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Incremental Redundancy

Incremental Redundancy description

Incremental Redundancy performance

Incremental Redundancy gains


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Incremental Redundancy (1)

IR is a physical layer performance enhancement for the acknowledged RLC modeof EGPRS

The basis for Incremental Redundancy (IR) is in the selective-reject-ARQ protocol of

the RLC layer. The ARQ protocol takes care of requesting and retransmittingincorrectly received blocks

By using the Backward Error Correction (BEC) procedures the selectiveretransmission of unsuccessfully delivered RLC/MAC blocks is obtained

IR improves the reception of retransmissions by combining the information in theoriginal transmission (which failed) with the received additional information, thereby

increasing the probability of correct reception The most important standardised feature of Incremental Redundancy is that MS has

mandatory IR combining in its receiver. IR has also been taken into account in thedesign of the coding schemes and block formats

Incremental Redundancy is suported by NOKIA. IR is set by default in NOKIAconfiguration


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Incremental Redundancy (2)

The figure shows an example of IR transmission and combining with differentpuncturing schemes for different transmission. The shown case corresponds to MCS-

4 or MCS-9, where the basic code rate is 1/1.

original data

1/3 coded data

1st xmission

2nd xmission

3rd xmission

1st decoding attempt

2nd decoding attempt

3rd decoding attempt

r = 1/3

r = 1/2

r = 1/1

r = 1/1

r = 1/1

r = 1/1


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Link Adaptation

Link Adaptation introduction

Link Adaptation algorithm

Bit Error Probability (Mean_BEP, CV_BEP)

Link Adaptation Procedure

I t d ti


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Introduction

In GSM Specification, there is full support for Bit Error Probability (BEP) based Link Adaptation(LA) algorithm

MS reports both mean and (normalized) standard deviation (std) of BEP values for thereceived radio blocks

Although mean BEP is clearly a dominant quantity in the selection procedure, stdBEP is found to be relevant for the strong coded MCSs

MS reports the network also if it has run out of IR memory The LA algorithm is based on these reports

The task of the LA algorithm is to select the optimal MCS for each radio condition to maximizechannel throughput

To maintain good throughput the goal for the LA algorithm is to adapt to situations wheresignal strength compared to interference level is changing within time

LA adapts to path loss and shadowing but not fast fading This corresponds to the "ideal LA"curves in link level simulations

Incremental Redundancy (IR) is better suited to compensate for fast fading

EGPRS LA is implemented in the Packet Control Unit (PCU)


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Resource Allocation Management

Multiple MS and Uplink Transmission

Multiple MS and Downlink Transmission

Radio Resource Operating Modes

EGPRS Territory Method

EGPRS Downgrades and Upgrades

Resource Allocation management from PCU


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Resource Allocation management from PCUMultiple Mobiles and Uplink Transmission

USF = 1

USF = 2

USF = 3

USF = 3

MSs

BTS

RLC Data Block

Mobile transmissions controlled by USF (Uplink State Flag) sent on DL

Mobile with correct USF will transmit in following block



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Resource Allocation management from PCUMultiple Mobiles and Downlink Transmission

TFI2

TFI5

TFI3

TFI2

MSs

BTS

TFI value included in RLC block header - indicates with which TBF the

RLC block is associated

RLC Data Block



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Resource Allocation management from PCU(E)GPRS territory method

RRM features optimally manage between circuit-switched and packet-

switched servicesTRX 1

Packet-switched TerritoryTRX 2

BCCH TCH TCH TCH TCH TCH TCH

TCHTCH P-TCH /

TCH

P-TCH /

TCH

P-TCH P-TCH

Circuit-switched TerritorySignalling

Circuit-switched Default (E)GPRS

Capacity

dedicated (E)GPRS(never filled with speech services)

P-TCH /

TCH

P-TCH /

TCH

PBCCH

Additional (E)GPRS

capacity

can be used for speech

Territory Border moves DYNAMICALLY based on CSW traffic load



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gTerritory Upgrades and Downgrades

The need for additional GPRS channels is checked when a new TBF is establishedor an existing TBF is terminated.

The PCU will request additional channels, if a GPRS territory contains less channels than could be allocated to a mobile

according to its multislot class or if the average number of TBFs per TSL is more than 1.5 after the allocation of

the new TBF (average TBF/TSL>1.5). These additional channels will be requested only if all GPRS default channels

are already in the GPRS territory.

The number of additional channels the PCU will request is the greater of thefollowing two numbers:

The number of additional channels needed in the allocation according to theMS's multislot class (this criterion is used only when the GPRS territory containsfewer channels than the MS is capable of using), and

The number of additional channels needed for the average number of allocatedTBFs per TSL to be 1(average TBF/TSL=1).

EDGE Overview

Documents

trxs5222018 edge overview

kbps5222018 edge overview

enhanced radio interface

edge vs gprsbenefits

different mcs

enhanced data rates

gprs architecture

introduction of new