02 introduction to edge

1 © Nokia Siemens Networks Introduction to EDGE / FAs / 22.05.2007For internal use

Introduction to EDGE

2 © Nokia Siemens Networks Flexi EDGE BTS OAM / FAs / 08.05.2007

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Objectives

At the end of this module the participant will be able to:• Understand the need for EDGE (Enhanced Data rates for Global /

GSM Evolution)• Describe the benefits for 2G network operators and end users• Describe the different services in EDGE phase 1 and 2 and EDGE

Evolution• Explain EGPRS modulation and coding schemes• Describe EGPRS link quality control• Describe the Abis interface requirement for EDGE


Mobile Data Traffic Increase


EDGE Evolution for better service continuity with WCDMA/HSPA

Many operators today have networks with EDGE - WCDMA service continuity for enhanced end user experience and increased revenues

Natural co-evolution tomeet end user demands

better end user better end user experienceexperiencemore revenuesmore revenuescost savingscost savings

WCDMAWCDMA

Ave. bit ratesAve. bit rates

HSPAHSPA

HSPA

GPRSGPRS EDGEEDGE EDGE EDGE EvolutionEvolution

EDGE Evolution

Servicecontinuity

Servicecontinuity


EDGEEDGE

Same content with same picture and sound qualitySame content with same picture and sound quality

SavingsSavings

Operator business case: service delivery cost evolution• EDGE at around half the cost of GPRS• EDGE Evolution at around half the cost of EDGE

EDGE EvolutionEDGEGPRS

4

21

Cost

EDGE EvolutionEDGE EvolutionGPRSGPRS

Cost savings opportunity example: Video clip download and play


ETSI Release 99 EDGE Implementation

UltraSite EDGE BTSMetroSite EDGE BTSFlexi EDGE BTSGSM compatible


EDGE Benefits for Operator

• Seamless delivery of all services across GSM / EDGE / WCDMA

• Higher capacity and coverage• Full global GSM / EDGE footprint and roaming as the

Americas now also go for GSM / EDGE - higher roaming incomes globally

• GSM / EDGE roll-out already on-going• EDGE and WCDMA with equal QoS support and

complementing data rates thus GSM / EDGE and WCDMA optimally complement each other

• 3G services delivery at lowest cost of coverage and capacity


EDGE Benefits for End Users

Edge offers better performance for data services:• WAP applications• Web browsing• Mobile video applications • Consumer applications

– Web browsing– E-mail– Chats– News push– Networked games– Electronic commerce– Digital photo post card

• Remote LAN & intranet access– Database access– File transfer– Corporate information exchange– Collaborative working– Electronic business card– Video conferences


EDGE Phase 1 (3GPP Release 99)

EDGE Phase 1 provides the following services and main features:• EGPRS at 8.8...59.2 kbps in up to 8 time slots• Modulation and Coding Schemes (MCS 1...9)• Link adaptation combined with Incremental Redundancy (LA / IR).• ECSD (specified, but not in NOKIA implementation)

– ECSD at 28.8kbps in transparent and non-transparent mode per time slot– ECSD at 43.2kbps in transparent and non-transparent mode in one time slot– ECSD at 57.6kbps in non-transparent mode in two time slots– ECSD at 64kbps in transparent mode in two time slots

EGPRS – Enhanced General Packed Radio Services


EDGE Phase 2 (3GPP Release 4/5)

EDGE Phase 2 provides improvements for voice and data services:• Introduction of real time packet services such as VoIP and Video over

IP.• Handover for packet-switched connections to enable real time

services.• Enhanced speech codecs “AMR".• Multi-call utilizing simultaneous voice and data.• Co-operation with UMTS Radio Access Networks.


EDGE Evolution

Further EDGE Evolution with new 3GPP work items starting from release 7:• 2-3 fold data speeds, voice and data capacity and spectral efficiency• <150 ms RTT (latency) • Enhanced service continuity with WCDMA/HSPA

NSN proposal for Rel. 7 features:• Downlink features

– MS Rx diversity – Dual Carrier

• Uplink features– Dual Symbol Rate

MS RX diversity: Mobile Station uses 2 receivers and 2 antennasDual Carrier: BTS uses 2 TRXs (carriers) to send data to the same MSDual Symbol Rate: Mobile uses new modulation technique (for instance 16-QAM or 32-QAM) to double the symbol rate (and bit rate)


GMSK Phase Trajectory


8-PSK vector diagram

3π/8 rotation

(0,0,1)

(1,0,1)

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

(0,1,1)

(1,1,1)

(1,1,0)

(1,0,0)


GMSK Normal Burst review

3 57 1 1 5726 8,253no. of bits

radio timeslot

TB:

data:

SB:

TS:

GP:

_____________________________________

_____________________________________

_____________________________________

_____________________________________

_____________________________________

___ ___ ___ ___ ___ ___ ___ ___use of bits


8-PSK Normal Burst

no. of bitsno. of symbols

radio timeslot

3173 17378

8,253

___ ___ ___ ___ ___ ___ ___ ___

11

use of bits


GMSK vs. 8-PSK burst

GMSK Modulated Burst 8-PSK Modulated Burst

Amplitude

Time

± 0.5dB± 8dB


8-PSK and GMSK Modulation Details Comparison

22.8kbps4x346bits=1,384bits/20ms(add. interleaving) = 69.2 kbps

Gross rate / time slot (channel coding included)

114 symbols(2*57 = 114bits)

116 symbols(2*3*58-2 = 346 bits)

Payload / burst(information part)

270.833 ksps270.833 kspsSymbol rate

GMSK, 1bit / symbol8-PSK, 3bit / symbolModulation

GSMEDGE


Note: GPRS is not a subset of EGPRS, i.e. the GPRS coding schemes CS1 to CS4 are different to EGPRS MCS1 to MCS9.

Scheme Modulation Data Rate (kbps)MCS-9MCS-8MCS-7MCS-6MCS-5

8PSK

59.254.444.829.6 22.4

MCS-4MCS-3MCS-2MCS-1

GMSK

17.614.811.28.8

Modulation and coding schemes

Protection

better

worse

From one data block to another, it is possible to switch between MCSs of the same “Family” (A, B or C), as it is in GPRS. However, in GPRS, once a data block is segmented to fit one particular coding scheme, it is not possible to switch the coding scheme on reception failure and the retransmission takes place with exactly the same protection as for its initial transmission. In EGPRS, it is possible to change the MCS i.e. the data block can be sent again but with better protection than for its initial transmission.


EGPRS Modulation and Coding Schemes


0

10

20

30

40

50

60

0 5 10 15 20 25 30

MCS-1MCS-2MCS-3MCS-4MCS-5MCS-6MCS-7MCS-8MCS-9

Throughput Vs. C/i

kbits/s

dB


Link Adaptation (LA)

The link adaptation mechanism works by adapting the protection of the information to be sent, according to the link quality.Requires accurate measurements of the link qualityUpcoming channel quality is predicted from measurements of the past. From prediction the relevant protection is decided.

-Accurate measurements of the link quality

New efficient measurements have been designed for EGPRS to accurately predict the upcoming link quality in several propagation channels (Typical Urban, Rural Area, Hilly Terrain, etc.) with various speeds.

-A finite set of protection of the information

For each user, the smallest allocated resource to send/receive some information is defined as one radio block (20ms). Since the resources are limited, the higher the level of protection for information, the less information is sent.

EDGE uses an enhanced 8-PSK modulation in addition to GMSK. Hence, different protection sets are available in GMSK and 8-PSK as these modulations do not have the same robustness to the propagation channel.


RLC data block sizes in MCS Families A,B and C

MCS-7

MCS-122

MCS-228

MCS-337

MCS-444

MCS-674

5656

MCS-86868

MCS-556

MCS-974 74

Family AFamily C

Family B


Link Adaptation in EDGE

EDGE enhancements• Better and faster measurements• Re-segmentation possible• 2 burst interleaving for MCS-7…9• Larger and dynamical window size

MS measurements• GPRS during idle slots, once every 120 ms• EDGE on each burst, once every 4.615 ms• In theory MCS can be changed after each 4 bursts• In practice adaptation limited to reporting period

Data

Report

Change MCS

MSBTS

Re-segmentation• GPRS cannot change coding during re-transmissions• EDGE can change coding within family

MCS-7

Report

Change MCS-5

MSBTS

Window size• GPRS window size fixed 64 blocks• EDGE dynamical from 64 to 1024 blocks

•Depending on the used MCS’s and no. of TSL in use

0 1 2 3 4 5 6 7 TDMA frame

in 4 bursts each 4.615 ms

burst 1

2 burst interleaving for MCS-7…9• 1184 bits delivered after each 20 ms• heading need all 4 bursts to code

GMSKMCS-7..9, 8-PSK

burst 2


Incremental Redundancy (IR)

Incremental Redundancy (IR) is an efficient combination of two techniques, automatic repeat request (ARQ) and forward error correction (FEC). ARQ• When receiver detects errors, it requests and receives a re-transmission of

the same RLC block.• The process continues until an uncorrupted copy reaches the destination. FEC• Adds redundant information to the user information at the transmitter• Receiver uses the information to correct errors caused by disturbances in

the radio channel.

The IR mechanism in EGPRS is designed with the nine MCSs . The basic characteristic of each MCS is its fixed data rate, hence a fixed protection level. For each of the MCSs, it is possible to reach the same data rate with the same protection level but with another protection scheme (there are 2 or 3 different protection schemes for each of the MCSs).


Incremental Redundancy (IR)

Block not accepted

Interference > corruption of data Store blockTransmission of GPSR data block

Puncturingscheme 1

Puncturingscheme 2

Soft combiningRe-transmission Interference > corruption of data Block accepted

Interference > corruption of data

Interference > corruption of dataTransmission of GPSR data block

Re-transmission Block not accepted

Re-transmission Interference > corruption of data Block not accepted

•EGPRS "send and minimize re-sending"

•GPRS "send and pray" "

The data block is first protected with the P1 of a certain MCS, and sent over the air to the receiver, which tries to recover the data. If this phase fails, the received P1 is stored in the receiver's memory for future use, and the transmitter sends the data block protected with the P2 of the same MCS. The receiver combines the received P2 with the stored P1 and tries to recover the data from the combination of P1, P2 and so on.

Note: If after P3, the data still cannot be recovered, P1 is sent again, and combined with the stored P1, P2 and P3 (which reaches a protection level of about 4 times the protection level of P1), and so on.


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

Incremental Redundancy (IR) Principle


Data Throughput Vs. C/i

Throughput vs C/I

0

10

20

30

40

50

60

0 5 10 15 20 25 30

dB

kbps

EGPRSGSM


Dynamic Abis enables higher EDGE bitrates with lessAbis capacity due to EDAP Pool

One master channel as today for voice and data, no blocking introducedFor higher data rates additional 16 kbps slave channels are always allocated as required by the MCS from the EDAP poolEach master timeslot can use individual 16 kbps slave timeslots from the EDAP. However when a master timeslot needs more than one slave timeslot then the consecutive slave timeslots are always reservedEDAP resources are reserved when TBF data transfer startsWhen at the end of data transmission the TBF is released also the allocated channels in the pool are releasedMaximal utilization of Abis resources, due to fact that Nokia Dynamic Abis does not introduce blocking nor RLC loss

TSL 0

TRX 1

TRX 2

TRX 3

TRX 4

TRX 5

012345678910111213141516171819202122232425262728293031

TRX 6

TRX 7

TRX 8

POOL

Example: MCS7, 44,8 kbit/s, 16k permanent + 3*16k in the pool


Coding scheme

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

MCS-1MCS-2MCS-3MCS-4MCS-5MCS-6MCS-7MCS-8MCS-9

Bit rate (bps)

8,012,014,420,0

8,811,214,817,622,429,644,854,459,2

Abis PCM allocation (fixed + pool/slave)

GPRSand

EDGE

EDGE

• Higher data rates than CS-1 and MCS-1 don’t fit into one 16 kbit/s channels

• then 32, 48, 64 or 80 kbit/s Abis links are needed

Higher EDGE air interface bit rates may require up to 5 fold Abis capacity

Technology

02 introduction to edge