Evaluation of Turbo H-ARQ Schemes for Cooperative MIMO Transmission - - PowerPoint PPT Presentation

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Evaluation of Turbo H-ARQ Schemes for Cooperative MIMO Transmission - - PowerPoint PPT Presentation

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Evaluation of Turbo H-ARQ Schemes for Cooperative MIMO Transmission Adrin Agustn, Josep Vidal , Eduard Calvo, Olga Muoz Universitat Politcnica de Catalunya (UPC) Barcelona, SPAIN IWWAN 04 Oulu Partners in in Romantik Romantik

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SLIDE 1

IWWAN – 04 Oulu

Evaluation of Turbo H-ARQ Schemes for Cooperative MIMO Transmission

Adrián Agustín, Josep Vidal, Eduard Calvo, Olga Muñoz

Universitat Politècnica de Catalunya (UPC) Barcelona, SPAIN

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SLIDE 2

2/24 IWWAN – 04 Oulu

Partners Partners in in Romantik Romantik

UPC – Universitat Politècnica de Catalunya

  • Prof. Josep Vidal

Department of Signal Theory and Communications UoB – University of Bristol

  • Prof. Andrew Nix

Centre for Communications Research DUN – Dune, Ingegneria dei Sistemi Otello Gasparini INFO – Università di Roma “La Sapienza”

  • Prof. Sergio Barbarossa

INFOCOM Department ICOM – Intracom

  • Dr. George Aggelou

Development Projects Department FLE – Fujitsu Laboratories of Europe

  • Dr. Sunil Vadgama

Advanced Radio Access Systems TELENOR – Telenor Communication II AS

  • Dr. Geoffrey Canright

Telenor R&D

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SLIDE 3

3/24 IWWAN – 04 Oulu

Outline Outline

  • Cooperative transmission schemes
  • Distributed space-time codes
  • Retransmission protocols
  • Results
  • Conclusions and trend lines
  • Cooperative transmission schemes
  • Distributed space-time codes
  • Retransmission protocols
  • Results
  • Conclusions and trend lines
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SLIDE 4

4/24 IWWAN – 04 Oulu

Cooperation Cooperation for for an an ad ad-

  • hoc

hoc multihop multihop scenario scenario

[Barbarossa03, Sendonaris03]

Source node

MAC

  • TDD/TDMA operation

Destination node

Twice the physical resources used

  • Resource allocation in the relay

slot crucial is for high network capacity ↔ ↔ ↔ ↔

TDD/TDMA frame

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SLIDE 5

5/24 IWWAN – 04 Oulu

Cooperation Cooperation for for an an ad ad-

  • hoc

hoc multihop multihop scenario scenario

[Laneman03]

Destination node

MAC

  • TDD/TDMA operation

Equivalent to a MIMO system

Source node

↔ ↔ ↔ ↔

TDD/TDMA frame

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SLIDE 6

6/24 IWWAN – 04 Oulu

Capacity Capacity gains gains of

  • f the

the cooperative cooperative schemes schemes

Creates a “virtual” multiple input-multiple output (MIMO) transmission scheme ⇒ Capacity gains! Operating modes for cooperative schemes:

  • Amplify and forward (AF)

The relay amplifies and retransmits the received signal Capacity is close to a M × 2N MIMO system

  • Decode and forward (DF)

The relay decodes and transmits the decoded symbols Capacity is close to a (M +R) × 2N MIMO system

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SLIDE 7

7/24 IWWAN – 04 Oulu

Cooperation Cooperation in a in a cellular cellular system system: DL : DL

LB LBR coverage coverage HBR HBR coverage coverage

Relay terminal User equipment

↑ ↑ ↓ ↓ ↓ ↔ PHY

  • Multiple antennas at BS and

(possibly) at the RS MAC

  • TDD/TDMA operation
  • One of the time slots shared for

cooperation RRM

  • Power allocation for the relay slot
  • Scheduling

based

  • n

the cooperative channel state ↓

TDD/TDMA frame

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SLIDE 8

8/24 IWWAN – 04 Oulu

Particularities Particularities of

  • f cooperative

cooperative schemes schemes

Difficulties

  • Erroneous reception at the relay channel
  • Number of physical resources: reuse of relay channel
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SLIDE 9

9/24 IWWAN – 04 Oulu

Cellular Cellular reuse reuse of

  • f the

the relay relay channel channel

100 200 300 400 500 600 700 800 900 1000 100 200 300 400 500 600 700 800 900 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 meters meters Scenario Base Station Mobile Station Relay Station 1 2 3 4 5 6 7 8 9 10 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Users M=2,N=1,R=1 Max users=9 case=10 DF-UC - Users in Cooperation

[Agustin04]

  • Game

theorical approach: interaction

  • f

decision- makers with conflicting

  • bjectives (power selection).
  • Decentralized algorithm
  • Components of the non-

cooperative game – A set of players: UE = {1,2,…K} – Actions for each player (relay power) – Utility function to map actions into the real numbers (maximise the bits/joule)

Single link throughput figures have to be scales to a factor K/(K+1)

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SLIDE 10

10/24 IWWAN – 04 Oulu

Particularities Particularities of

  • f cooperative

cooperative schemes schemes

Difficulties

  • Erroneous reception at the relay channel
  • Number of physical resources: reuse of relay channel

Design options:

  • Space-time coding: distributed codewords
  • A&F or D&F operation
  • Combined FEC/Retransmission scheme
  • Role of relay node in retransmissions:
  • Incremental
  • Selective
  • Receivers: linear vs. optimum
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SLIDE 11

11/24 IWWAN – 04 Oulu

Cooperative Cooperative transmission transmission (I) (I)

  • Turbo coded transmission schemes

– Non Cooperative

  • Alamouti

– Cooperative A&F (R=1)

  • Alamouti, VBLAST or QOD

– Cooperative D&F (R=2)

  • Alamouti, VBLAST or QOD
  • Retransmission combining schemes

– HARQ I – HARQ II BS

M=2

RS MS

N=1

~ 2x2 MIMO system

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SLIDE 12

12/24 IWWAN – 04 Oulu

Distributed Distributed Space Space Time Time Coding Coding

D&F implementation

( ) ( ) ( ) ( )

11 1 1 1 1 1 1 M M M R q T TM T M T M R

a a a a A a a a a

+ + + +

    =       L L M O M L L

Data associated to

  • ne transmitting

antenna Data associated to M tx atennas BS Data associated to R tx atennas RS

Space-time matrix associated to symbol q

Antennas Time

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SLIDE 13

13/24 IWWAN – 04 Oulu

Cooperative Cooperative transmission transmission (II) (II)

  • Turbo coded transmission schemes

– Non cooperative

  • Alamouti

– – – Cooperative A&F (R=1) Cooperative A&F (R=1) Cooperative A&F (R=1)

  • Alamouti

Alamouti Alamouti, VBLAST or QOD , VBLAST or QOD , VBLAST or QOD – – – C C C ooperative

  • operative
  • operative D&F (R=2)

D&F (R=2) D&F (R=2)

  • Alamouti

Alamouti Alamouti, VBLAST or QOD

BS M=2

, VBLAST or QOD , VBLAST or QOD

RS

  • If the packet is wrongly decoded, incremental

information is transmitted and combined at the receiver MS N=1 2x1 MIMO system

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SLIDE 14

14/24 IWWAN – 04 Oulu

Cooperative Cooperative transmission transmission (II) (II)

  • Turbo coded transmission schemes

– – – Non cooperative Non cooperative Non cooperative

  • Alamouti

Alamouti Alamouti – Cooperative A&F (R=1)

  • Alamouti, VBLAST or QOD

– – – Cooperative D&F Cooperative D&F Cooperative D&F ( ( (R=2 R=2 R=2) ) )

  • Alamouti

Alamouti Alamouti, VBLAST or QOD

BS M=2 RS Amplify and Forward

, VBLAST or QOD , VBLAST or QOD

MS N=1 ~ 2x2 MIMO system

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SLIDE 15

15/24 IWWAN – 04 Oulu

Cooperative Cooperative transmission transmission (II) (II)

  • Turbo coded transmission schemes

– – – Non cooperative Non cooperative Non cooperative

  • Alamouti

Alamouti Alamouti – – – Cooperative A&F Cooperative A&F Cooperative A&F ( ( (R=1 R=1 R=1) ) )

  • Alamouti

Alamouti Alamouti, VBLAST or QOD , VBLAST or QOD , VBLAST or QOD – Cooperative D&F (R=2)

  • Alamouti, VBLAST or QOD

BS M=2 RS MS N=1 ~ 2x2 MIMO system Decode and Forward

  • RS and BS may use the same ST block code (for

Alamouti or VBLAST), or different (for QOD)

Parity 1 Parity 2

  • RS transmits uncorrelated symbols: different

transmitted parity from BS and RS

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SLIDE 16

16/24 IWWAN – 04 Oulu

Turbo Codes for FEC/HARQ II Turbo Codes for FEC/HARQ II

  • Turbo Encoder implementation

RSC Π RSC

Input packet

rate ~ 1/3

Puncturing

  • utput

packet systematic parity

  • Concatenation with ST codes

Input packet

Turbo - Encoder Puncturing Space-Time encoder Improving diversity Change puncturing

  • From the relay node
  • Between different retransmissions

_1/ 2

1 1 1 1 1 1 1 1 1 1 1 1

BS

P     =      

systematic parity

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SLIDE 17

17/24 IWWAN – 04 Oulu

HARQ II Retransmission Strategy HARQ II Retransmission Strategy

  • HARQ-II transmission in a cooperative system

( )

_1/ 2

1

1 1 1 1 1 1 1 1 1 1 1 1

BS

P     =      

BS M=2 RS R=2 MS N=1 BS M=2 RS R=2 MS N=1

( )

2 _1/ 2

1 1 1 1 1 1 1 1 1 1 1 1

BS

P     =      

_1/ 2

1 1 1 1 1 1 1 1 1 1 1 1

RS

P     =      

  • If RS decodes correctly,

retransmits with puncturing matrix:

A new transmission is required ? Change puncturing at BS and RS

  • Use different puncturing matrices

for every retransmitted packet

( )

2 _1/ 2

1 1 1 1 1 1 1 1 1 1 1 1

RS

P     =      

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SLIDE 18

18/24 IWWAN – 04 Oulu

Results Results

  • Scenario

– List Sphere Decoder (near optimum receiver) – Symmetric configuration. All links have equal average SNR level – Flat Rayleigh fading channel, uncorrelated among links – 4 QAM constellation – Source: 2 antennas Relay: 1-2 antennas Destination: 1 antenna – HARQ-II retransmissions of equal or different size

  • Evaluation of throughput in the downlink

– Non cooperative 2 x 1 transmission – Cooperative D&F – diversity gain – Cooperative D&F – multiplexing gain – Cooperative A&F

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SLIDE 19

19/24 IWWAN – 04 Oulu

Non cooperative vs. cooperative Non cooperative vs. cooperative

  • 5

5 10 15 20 0.5 1 1.5 2 2.5 3 3.5 4 4.5 HARQ2 NC - Alamouti 2x1 4 QAM SNR Throughput (bits/s/Hz) rate 1/2 rate 3/4 rate 1

  • 5

5 10 15 20 0.5 1 1.5 2 2.5 3 3.5 4 4.5 HARQ2 DF-RC Alamouti - RS only tx if it decodes correctly 4 QAM SNR Throughput (bits/s/Hz) rate 1/2 rate 3/4 rate 1 MIMO 2x2

MIMO 2x2 ergodic capacity for 4 QAM

Alamouti coding: Cooperation achieve about 3 dB gain Rate of codes has no major impact: HARQ-II manages it efficiently

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SLIDE 20

20/24 IWWAN – 04 Oulu

Cooperative D&F Cooperative D&F – – multiplexing gain multiplexing gain

  • 5

5 10 15 20 0.5 1 1.5 2 2.5 3 3.5 4 4.5 HARQ2 DF-UC - QOD - RS always tx 4 QAM SNR Throughput (bits/s/Hz) rate 3/4 rate 1 MIMO 2x2

Distributed Quasi-Orthogonal STC Distributed VBLAST

  • 5

5 10 15 20 0.5 1 1.5 2 2.5 3 3.5 4 4.5 HARQ2 DF-RC - VBLAST - RS always tx 4 QAM SNR Throughput (bits/s/Hz) rate 3/4 rate 1 MIMO 2x2

Both codes achieve multiplexing gain at high SNR, but poorer performance than Alamouti at low SNR…

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SLIDE 21

21/24 IWWAN – 04 Oulu

Cooperative D&F Cooperative D&F – – multiplexing gain multiplexing gain

Alamouti ST code (rate 1)

  • 5

5 10 15 20 0.5 1 1.5 2 2.5 3 3.5 4 4.5 HARQ2 DF-UC - QOD - RS always tx 4 QAM SNR Throughput (bits/s/Hz) Alamouti QOD MIMO 2x2

QOD ST codes (rates 2)

… this is suggesting the choice of the STBC rate as a parameter for the dynamic link control.

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SLIDE 22

22/24 IWWAN – 04 Oulu

Cooperative A&F Cooperative A&F

Amplify and forward (A&F) shows about 2 dB loss with respect to D&F, but that the relay may be implemented with a single antenna.

  • 5

5 10 15 20 0.5 1 1.5 2 2.5 3 3.5 4 4.5 HARQ2 AF - RS always tx 4 QAM SNR Throughput (bits/s/Hz)

Alamouti VBLAST MIMO 2x2

Alamouti ST code (rate 1) VBLAST ST code (rate 2)

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SLIDE 23

23/24 IWWAN – 04 Oulu

HARQ HARQ-

  • I vs. HARQ

I vs. HARQ-

  • II retransmissions

II retransmissions

Alamouti is used as ST coder HARQ-II adapts closely the required rate to the channel conditions, and requires lower number of retransmissions Alamouti is used as ST coder Retransmissions of shorter duration (in red) ⇒ approaches capacity more closely (at the expenses of higher delay)

  • 5

5 10 15 20 0.5 1 1.5 2 2.5 3 3.5 4 4.5 HARQ1 - DF - Full Slot Retransmissions - 16 QAM SNR Throughput (bits/s/Hz) rate 1/2 rate 3/4 rate 1

  • 5

5 10 15 20 0.5 1 1.5 2 2.5 3 3.5 4 4.5 HARQ2 - DF - Full Slot Retransmissions - 16 QAM SNR Throughput (bits/s/Hz) rate 1/2 rate 3/4 rate 1

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SLIDE 24

24/24 IWWAN – 04 Oulu

Conclusions Conclusions

  • Cooperation schemes are able to provide multiplexing

gains even if terminals use a single antenna, by using STBC borrowed from MIMO systems

  • Capacity approaching schemes may be based on:
  • The selection of the STBC or
  • The retransmissions at fractional rate

different implications for the selection of the MAC layer and the latency experienced.

  • The A&F solution is a good compromise between

performance and complexity of the relay node

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SLIDE 25

25/24 IWWAN – 04 Oulu

Publications Publications

Evaluation of different ARQ schemes Adrian Agustin, Eduard Calvo, Josep Vidal, Olga Muñoz, “Evaluation of Turbo- Coded Cooperative Retransmission Schemes”, IST Mobile Communications Summit 2004¸ Lyon, France, 27-30 June 2004. Linear vs. near-optimum receivers Adrian Agustin, Josep Vidal, Eduard Calvo, Olga Muñoz, “Evaluation of Turbo H-ARQ Schemes for Cooperative MIMO Transmission”, IEEE IWWAN 2004, Oulu, Finland, June 2004. Design of STBC in distributed operation Adrian Agustin, Josep Vidal, Eduard Calvo, Meritxell Lamarca, Olga Muñoz, “Hybrid Turbo FEC/ARQ Systems and Distributed Space-time Coding for Cooperative Transmission in the Downlink”, IEEE PIMRC 2004, Barcelona, Spain, September 2004.