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 IWWAN – 04 Oulu
Partners in in Romantik Romantik Partners 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 2/24 IWWAN – 04 Oulu
Outline Outline • Cooperative transmission schemes • Cooperative transmission schemes • Distributed space-time codes • Distributed space-time codes • Retransmission protocols • Retransmission protocols • Results • Results • Conclusions and trend lines • Conclusions and trend lines 3/24 IWWAN – 04 Oulu
Cooperation for for an an ad ad- -hoc hoc multihop multihop scenario scenario Cooperation [Barbarossa03, Sendonaris03] MAC - TDD/TDMA operation Source Destination node node Twice the physical resources used - Resource allocation in the relay slot crucial is for high network capacity ↔ ↔ ↔ ↔ TDD/TDMA frame 4/24 IWWAN – 04 Oulu
Cooperation for for an an ad ad- -hoc hoc multihop multihop scenario scenario Cooperation [Laneman03] MAC - TDD/TDMA operation Destination Source node node Equivalent to a MIMO system ↔ ↔ ↔ ↔ TDD/TDMA frame 5/24 IWWAN – 04 Oulu
Capacity gains gains of of the the cooperative cooperative schemes schemes Capacity Creates a “virtual” multiple input-multiple output (MIMO) transmission scheme ⇒ Capacity gains! Operating modes for cooperative schemes: - Amplify and forward (AF) Capacity is close to a The relay amplifies and retransmits M × 2 N MIMO system the received signal - Decode and forward (DF) Capacity is close to a ( M + R ) × 2 N MIMO The relay decodes and transmits the decoded symbols system 6/24 IWWAN – 04 Oulu
Cooperation in a in a cellular cellular system system: DL : DL Cooperation MAC - TDD/TDMA operation LB LBR HBR HBR - One of the time slots shared for coverage coverage coverage coverage cooperation PHY - Multiple antennas at BS and (possibly) at the RS RRM - Power allocation for the relay slot - Scheduling based on the Relay terminal cooperative channel state User equipment ↔ ↓ ↓ ↓ ↓ ↑ ↑ TDD/TDMA frame 7/24 IWWAN – 04 Oulu
Particularities of of cooperative cooperative schemes schemes Particularities Difficulties • Erroneous reception at the relay channel • Number of physical resources: reuse of relay channel 8/24 IWWAN – 04 Oulu
Cellular reuse reuse of of the the relay relay channel channel Cellular [Agustin04] • Game theorical approach: interaction of decision- makers with conflicting Scenario M=2,N=1,R=1 Max users=9 case=10 DF-UC - Users in Cooperation 900 1 8 objectives (power selection). 8 Base Station Mobile Station 0.9 800 Relay Station 4 0.8 • Decentralized algorithm 700 4 0.7 600 0.6 • Components of the non- 5 meters 500 0.5 cooperative game 5 1 0.4 2 – A set of players: UE = 400 6 1 6 {1,2,…K} 0.3 2 300 3 – Actions for each player 0.2 3 9 200 (relay power) 9 7 0.1 7 – Utility function to map 100 0 0 0 100 1 200 2 300 3 400 4 500 5 600 6 700 7 800 8 900 9 1000 10 actions into the real meters Users numbers (maximise the Single link throughput figures have bits/joule) to be scales to a factor K/(K+1) 9/24 IWWAN – 04 Oulu
Particularities of of cooperative cooperative schemes schemes Particularities 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 10/24 IWWAN – 04 Oulu
Cooperative transmission transmission (I) (I) Cooperative • Turbo coded transmission schemes – Non Cooperative BS • Alamouti – Cooperative A&F ( R=1 ) M=2 • Alamouti, VBLAST or QOD – Cooperative D&F ( R=2 ) • Alamouti, VBLAST or QOD RS • Retransmission combining schemes – HARQ I – HARQ II MS N=1 ~ 2x2 MIMO system 11/24 IWWAN – 04 Oulu
Distributed Space Space Time Time Coding Coding Distributed D&F implementation Space-time matrix associated to symbol q Data associated to M tx atennas BS Antennas a a a a L L ( ) ( ) 11 1 M + + 1 M 1 1 M R = A M O M Time q a a a a L L ( ) ( ) + + T 1 TM T M 1 T M R Data associated to R tx atennas RS Data associated to one transmitting antenna 12/24 IWWAN – 04 Oulu
Cooperative transmission transmission (II) (II) Cooperative • Turbo coded transmission schemes – Non cooperative BS • Alamouti M=2 – Cooperative A&F (R=1) – Cooperative A&F (R=1) Cooperative A&F (R=1) – • Alamouti , VBLAST or QOD • Alamouti Alamouti, VBLAST or QOD , VBLAST or QOD • – C ooperative D&F (R=2) – C C ooperative ooperative D&F (R=2) D&F (R=2) – • Alamouti , VBLAST or QOD • Alamouti Alamouti, VBLAST or QOD , VBLAST or QOD • RS • If the packet is wrongly decoded, incremental information is transmitted and combined at the MS receiver N=1 2x1 MIMO system 13/24 IWWAN – 04 Oulu
Cooperative transmission transmission (II) (II) Cooperative • Turbo coded transmission schemes – Non cooperative – Non cooperative Non cooperative – BS • Alamouti • Alamouti Alamouti • M=2 – Cooperative A&F ( R=1 ) • Alamouti, VBLAST or QOD – Cooperative D&F ( R=2 ) – Cooperative D&F Cooperative D&F ( ( R=2 R=2 ) ) – • Alamouti , VBLAST or QOD • Alamouti Alamouti, VBLAST or QOD , VBLAST or QOD • RS Amplify and Forward MS N=1 ~ 2x2 MIMO system 14/24 IWWAN – 04 Oulu
Cooperative transmission transmission (II) (II) Cooperative • Turbo coded transmission schemes – Non cooperative – Non cooperative Non cooperative – BS • Alamouti • Alamouti Alamouti • M=2 – Cooperative A&F ( R=1 ) – Cooperative A&F Cooperative A&F ( ( R=1 R=1 ) ) – • Alamouti , VBLAST or QOD • Alamouti Alamouti, VBLAST or QOD , VBLAST or QOD • Parity 1 – Cooperative D&F ( R=2 ) • Alamouti, VBLAST or QOD Parity 2 RS Decode and • RS and BS may use the same ST block code (for Forward MS Alamouti or VBLAST), or different (for QOD) N=1 • RS transmits uncorrelated symbols: different transmitted parity from BS and RS ~ 2x2 MIMO system 15/24 IWWAN – 04 Oulu
Turbo Codes for FEC/HARQ II Turbo Codes for FEC/HARQ II • Turbo Encoder implementation Input systematic 1 1 1 1 1 1 systematic packet = P 1 0 1 0 1 0 BS _1/ 2 parity 0 1 0 1 0 1 RSC Puncturing Π parity output packet RSC rate ~ 1/3 Improving diversity � Change puncturing • From the relay node • Between different retransmissions • Concatenation with ST codes Input Turbo - Space-Time Puncturing Encoder encoder packet 16/24 IWWAN – 04 Oulu
HARQ II Retransmission Strategy HARQ II Retransmission Strategy • HARQ-II transmission in a cooperative system 1 1 1 1 1 1 ( ) BS BS 1 = P 1 0 1 0 1 0 BS _1/ 2 M=2 M=2 0 1 0 1 0 1 1 0 1 0 1 0 A new transmission is required ? ( ) 2 = P 1 1 1 1 1 1 BS _1/ 2 1 0 1 0 1 0 Change puncturing at BS and RS RS RS • If RS decodes correctly, R=2 R=2 retransmits with puncturing matrix: MS MS N=1 N=1 1 0 1 1 0 1 = P 1 1 0 1 0 1 RS _1/ 2 • Use different puncturing matrices 1 0 1 1 1 0 for every retransmitted packet 0 1 0 1 0 1 ( ) 2 = P 1 0 1 0 1 0 RS _1/ 2 1 1 1 1 1 1 17/24 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 18/24 IWWAN – 04 Oulu
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