a technical review - wireless technology · pdf file- a technical review - (or ”what,...

- PCCA meeting Indianapolis 19-20 Aug 2003 -

EDGE- A Technical Review -

(or ”what, why and how...”)

Tomas KöhlerTechnical Manager – GSM Radio

Ericsson AB

EDGE Technical Presentation Rev A 20 Aug 2003 2 Ericsson AB


Common misunderstandings about EDGE:

• GPRS and EDGE are two different technologies• EDGE uses a modulation that is very sensitive to

poor radio conditions• EDGE and GPRS have almost the same throughput• EDGE needs more sites than GSM/GPRS due to

worse coverage performance• EDGE requires major network upgrades• There is no need for EDGE in Europe where WCDMA

is being deployed



”GPRS and EDGE are two different technologies” ...



The The Abbreviation

GPRS = GPRS = GGeneral eneral PPacket acket RRadio adio SSystemystem

EEGPRS = GPRS + EDGE modulationGPRS = GPRS + EDGE modulation

EDGE = EDGE = Enhanced Data rates for Global Evolution



EDGE – a standard evolution of GPRS

SGSN GGSN

Internet

GPRS = EDGE

SGSN GGSN

InternetGPRS Protocol (R’97)

BSC/PCUBTSGMSKTRUEDGE

EGPRS Protocol (R’99)

EDGE TRU

Minor network modification

GPRS

Protocol enhancements– Higher bit rate modulation (8PSK)– More robust radio protocol– Link Quality Control (combined LA and IR)



10

20

30

40

50

60

0

MC

S1

MC

S2

MC

S3

MC

S4

MC

S5

MC

S6

MC

S7

MC

S8

MC

S9

CS1

CS2

CS3

CS4

8.0

12.014.4

20.0

8.411.2

14.817.6

22.4

29.6

44.8

54.4

59.2

Standardized improvement IEDGE Coding Schemes

kbps

GMSK modulation 8PSK modulationGPRS EDGE



Standardized improvement II- Packet Re-transmission -

GPRS (R’97)

Re-transmission withanother CS not possible

EDGE (R’99)

Re-transmission withanother MCS possible



Packet Transfer and rePacket Transfer and re--transmissiontransmission- Example GPRS -

LLC frame 11 ......22 33 44 55 66 77 88LLC frame

22

33

5566

CS3CS3

CS1CS1

CS3 codedCS3 coded

Packet

DL ACK/N

ACK mess

age

Packet

DL ACK/N

ACK mess

age

Bitmap

:

Bitmap

:-- Pac

ket 2 a

nd 3 on

ce mor

e !

Packet

2 and 3

once

more !

11

22

33

44



Packet Transfer and rePacket Transfer and re--transmissiontransmission- Example EGPRS -

LLC frame 11 ......22 33 44 55 66 77 88LLC frame

et DL A

CK/NACK m

essa

et DL A

CK/NACK m

essa

:: and 3

once

more !

and 3

once

more !

MCS6 codedMCS6 coded

11

22

33

44

Pack

ge

Pack

ge

22

5566

33

MCS3

Bitmap

Bitmap

-- Packet

2

Packet

2



Standardized improvement IIIStandardized improvement III-- EGPRS addressing window ...EGPRS addressing window ...

PCUPCURLC/MACRLC/MACprotocolprotocol

11 2200 33 44 20462046 20472047 00 11 22 33 44 20452045 20462046 20472047

Sliding addressing window up to 1024Sliding addressing window up to 1024

… increased from … increased from 6464 to to 10241024 to avoidto avoidprotocol stalling !!!protocol stalling !!!



Standardized improvement IV- Measurement Reporting -

GPRS (R’97) EDGE (R’99)

Quality report based on GSM

channel structure analysis(Carrier strength, Bit Error Rate …)

Quality reportbased on

burst analysis(Bit Error Probability)



The Effect

NetworkNetwork

Slowadapting

LA

Fastadapting

LA

GPRSGPRS(R’97)(R’97)

EDGEEDGE(R’99)(R’99)



Standardized improvement V- Interleaving -

Burst1

Burst3

Burst2

Burst4

EDGE MCS 7/8/9Interleaved over 2 Bursts !

First half correct

Second half lost

Time

Retransmission of second half only

Quality

Burst1

Burst3

Burst2

Burst4

GPRS CS4

Radio Block lost !

Interleaved over 4 Bursts !

Time

Retransmission of lost Block necessary

Quality



Standardized improvement VI- Link Quality Control for EDGE -

0 5 10 15 20 25 30 350

10

20

30

40

50

60

C/I [dB]

Bitr

ate

[kbp

s]

IR LA

C/I [dB]Bi

t rat

e [k

bit/s

]

• Link Adaptation (LA)– Extensive set of modulation and

coding schemes

• Incremental Redundancy (IR)– Code combining of transmission

attempts

• LA and IR can be combined

Reliable link quality and efficient use of radio resources!



Link Adaptation- Use optimum MCS for the radio environment

C1220.538.8MCS-1

B1280.6611.2MCS-2

A1370.8514.8MCS-3

C1441.017.6GMSKMCS-4

B1560.3722.4MCS-5

A1740.4929.6MCS-6

B22*560.7644.8MCS-7

A22*680.9254.4MCS-8

A22*741.059.28PSKMCS-9

FamilyBlocks per 20 ms

OctetsCode Rate

Maximum rate[kbps]

Modulation

SchemeLINK

ADAPTATOIN



Incremental Redundancy- Transmit more coding if needed

-0.260.538.8MCS-1

-0.330.6611.2MCS-2

0.280.420.8514.8MCS-3

0.330.51.017.6GMSKMCS-4

-0.190.3722.4MCS-5

-0.240.4929.6MCS-6

0.250.380.7644.8MCS-7

0.310.460.9254.4MCS-8

0.330.51.059.28PSKMCS-9

P1+P2+P3

P1+P2P1Maximum rate [kbps]

Modulation

Scheme

Use same MCS forretransmissions

MCS-9 achieves similar robustness

and bitrate as MCS-5



EDGE Radio Link Performance

Link level simulations with Ericsson system algorithm

Assumptions:• MCS-9 and MCS-3 with

incremental redundancy, IR (unlimited memory)

• MCS-1 to MCS-9 without IR (no memory)

• Downlink• TU3 channel• No frequency hopping• Co-channel interference• No adjacent channel interference



”EDGE uses a modulation that is very sensitive to poor radio conditions” ...

”GPRS and EDGE have almost the same throughput” ...

”EDGE needs more sites than GSM/GPRS due to worse coverage performance” ...



GPRS/EDGE Performance in the radio environment

GSM HO

GPRS CS-2

GPRS CS-1-4

Note. GPRS CS-2 and CS-1-4 superimposed for indicative comparison only

Comparing robustnessGPRS – EDGE:- CS-1 ~ MCS-1- CS-2 ~ MCS-2- CS-3 ~ MCS-3- CS-4 ~ MCS-4

Voice

Typical C/I distribution- Cell border ~10-12 dB- Mean C/I ~18 dB



Conclusions from system simulationsand confirmed in trials

• EDGE performs well in a wide range of network scenarios– FH and no FH

– BCCH and non-BCCH frequencies

– Different reuse configurations

• In very tight reuse scenarios (e.g. 1 reuse), FH is essential



Optimizing EDGE throughput in a tight network

10

20

30

40

50

60Throughput per TS (kbps)

Voice

Data

EDGE

Separate channel groups for voiceand EDGE (and CS-3&4)

Higher throughput at cell border!GPRS CS1-4

GPRS CS-2

EDGE: >25 dB C/I

Voice: ~10 dB C/I

C/I (dB)10 20 30 40



EDGE Coverage

EDGE20 kbps/TS(practical value)

GPRS11-16 kbps/TS(theoretical value)

Voice still limits the coverage planning

➨ EDGE application coverage always better than GPRS and voice



GPRS/EDGE Performance Aspects- Throughput versus Latency

• Handshaking and signaling affects perceived data speed!– E.g. emails and web browsing

Laptop measurements include:1. Transfer time PC – MS interface (IR, Bluetooth, ...)2. MS internal processing3. Wait to send channel req4. Transfer time in BSS, CN, and out on the Internet...

• Typical RTT values: ~500-600 ms• Network dependent• Measurement setup dependent

GGSNPCUBSCBTS SGSN

R Um Abis Gb Gn Gi



Example: Email - Receive (POP3) and Send (SMTP)

Client Server

Message

Total time to download

email

Improved RTT EDGE

Signaling(RTT)

Download(FTP)



Example: Web browsing

Client Server

”FTP Part”

”RTT part”



Ericsson lab results of EDGE performance

LA, UDP, Effective RLC throughput DL, 2+1, (791)

0,00

20,00

40,00

60,00

80,00

100,00

120,00

140,00

51 10 29 48 7 26 45 4 23 42 1 20 39 58 17 36 55 14 33 52 11 30 49 8 27 46 5 24 43 2 21 40

Min:Sec

Kbi

t/s

RLC Kbit/s DL

Higher layer dies at C/I=5 dB

C/I=20 dBC/I=15 dB

C/I=10 dB

C/I=5 dB

C/I=0 dB



0

20

40

60

80

100

120

0 100 200 300 400

Time [s]

Kbit/

s

05101520253035404550

Re-tr

ansm

. [%

]

Kbit/s

Re-transmittedblocks DL [%]

Position A –Next to siteC/I ~25 dB

Position B –½ mile from siteC/I ~15 dB

IR PerformanceDrive test Position C – Past cell

border, 1 mile from siteC/I ~10 dB



”EDGE requires major network upgrades” ...



Upgrading to EDGE

BTS HW

Radio Network design, dimensioning Optional

BSS SW

BSC/PCU HW

Performance management: Counters, Alarms, processes, OSS, ...

Core Network: GSNs, DNS & Radius servers, HLRs, backbone NW, …

Competence: TCP/IP & Radio

Inheritedfrom GPRS Additions



Upgrading to EDGE

EDGE UNIT

BTS HW

BSS SW



”There is no need for EDGE in Europe where WCDMA is being deployed” ....



GSM operator with WCDMA spectrumRoll-out scenario

WCDMA

GSM/GPRSEDGE EDGE

Rural Sub-urban Urban Sub-urban Rural



End-user experience in focusService Continuity WCDMA – GSM

Perf

orm

ance

Coverage

~36kbps*

* 3 slot handset

EDGE

~128kbps*

=

GSM/GPRS

128kbps

WCDMA



Combined GSM/GPRS/EDGE/WCDMA NetworkApplicationService Capability

ServersApplication

Service

PSTN/ISDN

GSMGPRSEDGE

InternetIntranets

GGSN

BSC

Media GatewayWCDMARNC

Media Gateway

GMSCserver

HLR AuC FNRControl andTransport MSC

server SGSN

IP/ATM/TDM Network

User data Control




WCDMA

GSM/GPRSEDGE EDGEEDGE




Capacity Assumptions:10MHz spectrum1 Mio subscribersAnnual growth 10%EDGE handset penetration after 5 years = 70%

~9000 extra TRUs due to GPRS !

~2000 extra TRUs with EDGE !78% saving !



Capacity Assumptions:10MHz spectrum1 Mio subscribersAnnual growth 10%EDGE handset penetration after 5 years = 70%

Site splits reduced from ~1300 to ~600

50% saving !




GSM/GPRS

WCDMA

EDGE EDGEEDGE

Low segment / entry handsetsHigh segment / professional handsets




Conclusions

• EDGE is a standard evolution of the GPRS radio interface– Release 97 Release 99– 3 times higher bit rate modulation, more robust radio protocol

• EDGE performs well in lab and live tests– 100 kbps achieved in live network using 2 TS– Significant performance benefits in all practical radio environments– Coverage planning limited by voice only

• EDGE requires minor network modification– Fast rollout – one EDGE TRU per cell plus BSS SW upgrade

• EDGE complements WCDMA– Enhanced end-user experience – Increased data capacity in existing GSM spectrum

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