HARQ Feedback Joint Coding IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number: IEEE S802.16m-09/0046 Date Submitted: 2009-1-5 Source: Zheng Yan-Xiu, Yu-Chuan Fang, Chang-Lan Tsai, Chung-Lien Ho, Hsi-Min Hsiao, Ren-Jr Chen, Richard Li, E-mail: zhengyanxiu@itri.org.tw. ITRI Venue: IEEE Session #59, San Diego. Base Contribution: N/A Re: 802.16m-08/052, Call for Comments on 802.16m SDD (802.16m-08/003r6), Section 11.13.2.6 UL HARQ Feedback Purpose: To be discussed and approval by IEEE 802.16m TG Notice: This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.16. Patent Policy: The contributor is familiar with the IEEE-SA Patent Policy and Procedures: <http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and <http://standards.ieee.org/guides/opman/sect6.html#6.3>. Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and <http://standards.ieee.org/board/pat >.

Motivation HARQ feedback introduces significant overhead in uplink control channel due to 1-bit information feedback The HARQ feedback highly influences system coverage and occupies large radio resource Concurrent HARQ feedbacks would occur for some scenarios Multi-carrier introduces parallel and concurrent HARQ feedback channels from different carriers Multiple streams MIMO transmission needs multiple HARQ feedbacks for multiple streams TDD mode makes multiple HARQ feedbacks aggregated on the same subframe In IEEE 802.16m, two or three bits HARQ feedback would occur within one subframe due to TDD mode, Coding or information aggregation on these multiple feedbacks improves feedback reliability or enlarge HARQ feedback channel capacity

Examples of Concurrent HARQ Feedback Multi-Carrier TDD Mode Multiple Streams MIMO

Mapping Concept Mapping multiple HARQ feedbacks on a sequence or a composite sequence The composite sequences can be linear combination of sequences for 1-bit feedback Since more than one feedbacks are transmitted by one sequence, power can be aggregated Power gain or coding gain can be acquired

Existing Design No. orthogonal Sequence 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 0 1 0 1 1 1 0 0 0 1 0 3 1 0 0 1 0 1 1 1 0 0 0 1 4 1 1 0 0 1 0 1 1 1 0 0 0 5 1 0 1 0 0 1 0 1 1 1 0 0 6 1 0 0 1 0 0 1 0 1 1 1 0 7 1 0 0 0 1 0 0 1 0 1 1 1 8 1 1 0 0 0 1 0 0 1 0 1 1 9 1 1 1 0 0 0 1 0 0 1 0 1 10 1 1 1 1 0 0 0 1 0 0 1 0 11 1 0 1 1 1 0 0 0 1 0 0 1 12 1 1 0 1 1 1 0 0 0 1 0 0 IEEE C80216m-08_1057r2 12 orthogonal sequences 6 for ACK and 6 for NACK 6 independent HARQ channels for 6 users Distribute the code three 2x6 or 6x2 resource tile Non-coherent detection is used to detect code sequence

Example of 2-bit Concurrent HARQ Feedbacks 12 orthogonal sequences with length 12 for HARQ feedback channel Two HARQ channel feedbacks from a user Three users share this HARQ feedback channel Conventional design 6 for ACK and 6 for NACK Each user chooses two from ACK sequences and two from NACK sequences Two sequences are transmitted by one user New design 3 for ACK-ACK; 3 for ACK-NACK; 3 for NACK-NACK; 3 for NACK-ACK One sequence are transmitted by one user Channel Bandwidth 10MHz Over-sampling Factor 28/25 FFT Size 1024 Cyclic prefix (CP) ratio 1/8 Channel condition PB3, VA120, VA350 The number of antennas Tx:1, Rx:2 Modulation BPSK FMT size 6x2 Block size 6x6 Receiver HARQ FB: non-coherent detection, MLD

Example of Nine-State HARQ feedback No. orthogonal Sequence S1 1 1 1 1 1 1 1 1 1 1 1 1 S2 1 0 1 0 1 1 1 0 0 0 1 0 S3 1 0 0 1 0 1 1 1 0 0 0 1 S4 1 1 0 0 1 0 1 1 1 0 0 0 S5 1 0 1 0 0 1 0 1 1 1 0 0 S6 1 0 0 1 0 0 1 0 1 1 1 0 S7 1 0 0 0 1 0 0 1 0 1 1 1 S8 1 1 0 0 0 1 0 0 1 0 1 1 S9 1 1 1 0 0 0 1 0 0 1 0 1 S10 1 1 1 1 0 0 0 1 0 0 1 0 S11 1 0 1 1 1 0 0 0 1 0 0 1 S12 1 1 0 1 1 1 0 0 0 1 0 0 12 sequences 2 HARQ feedback channel 3 states per channel: ACK, NACK and DROP Choose S1, S2, S3 and S4 as a subset Construct sequences C1~C9 by Mapping of C1~C9 is shown as following table Code C1 C2 C3 C4 C5 C6 C7 C8 C9 Channel 1 ACK NACK DROP Channel 2

Performance of Nine State Joint Coding Similar performance is achieved to provide extra information “DROP” Channel Bandwidth 10MHz Over-sampling Factor 28/25 FFT Size 1024 Cyclic prefix (CP) ratio 1/8 Channel condition PB3, VA120, VA350 The number of antennas Tx:1, Rx:2 Modulation BPSK FMT size 6x2 Block size 6x6 Receiver HARQ FB: non-coherent detection, MLD

Example of 2-bit Concurrent HARQ Feedbacks Three distributed 6x2 resource tiles Non-coherent detection 12 orthogonal sequences with length 12 for HARQ feedback channel Two HARQ channel feedbacks from a user Three users share this HARQ feedback channel Conventional design 6 for ACK and 6 for NACK Each user chooses two from ACK sequences and two from NACK sequences Two sequences are transmitted New design 3 for ACK-ACK; 3 for ACK-NACK; 3 for NACK-NACK 3 for NACK-ACK Each transmit one of these sequences to represent 2-bit HARQ feedbacks Only one sequence is transmitted and power gain is acquired

Conclusion Mapping multiple HARQ feedbacks on one sequence provides performance gain. The sequence can be constructed by choosing 1-bit feedback or composite 1-bit feedbacks with normalized power. More information can be transmitted with similar performance, e.g. tri-state feedback. Multicarrier, TDD mode and multiple streams MIMO are highly recommended to adopt this feedback to enhance link reliability or capacity.

SDD TEXT Proposal 11.13.2.6 HARQ feedback A basic ACK/NAK channel to transmit 1-bit feedback is supported. 1-bit feedback compatible joint coded HARQ feedback will be supported to enhance feedback channel reliability or increase the capacity for concurrent feedback scenarios, e.g. multi-carrier, TDD mode, multiple streams MIMO. Mapping multiple feedbacks by 1-bit feedback or composite 1-bit feedbacks with normalized power will be used. An enhanced ACK/NAK control channel with some additional information is FFS.