HARQ Feedback Channel for 2bit HARQ feedback IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number: C80216m-09/0672 Date Submitted: 2009-03-08 Source: Jinyoung Chun (jychun03@lge.com) Sukwoo Lee (sugoo@lge.com) Bin-Chul Ihm (bcihm@lge.com) LG Electronics *<http://standards.ieee.org/faqs/affiliationFAQ.html> Re: Call for Comments on Amendment Working Document, IEEE 802.16m-09/0012 Target topic: UL PHY Control Base Contribution: None Purpose: Discussion and adoption for 802.16m AWD 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 >.

Contents UL HARQ feedback channel for 1bit feedback Refer to C80216m-09_0386 (output of UL Ctrl DG). The necessary of 2bit (or more) feedback Proposed UL HARQ feedback channel for 2bit feedback The comparison with other proposals Proposed AWD text

UL HARQ feedback channel for 1bit feedback The structure for 1bit feedback There are 2 HARQ feedback channels in three HMTs, which is 2x2. Orthogonal sequence 1-bit feedback [+1 +1 +1 +1] ACK of channel 1 [+1 -1 +1 -1] NACK of channel 1 [+1 +1 -1 -1] ACK of channel 2 [+1 -1 -1 +1] NACK of channel 2

The necessary of multiple bit feedback The usage scenario of multiple bit feedback for a MS Multiple bits feedback for a DL burst Multiple codeword (MCW): When a MS receives MCW bursts, the MS may transmit a HARQ feedback. Multiple ACK/NACKs for multi-hop in Relay: Multiple NAK for multi-hop and single ACK is needed in Relay. Multiple bits feedback for multiple DL bursts Multiple ACK/NACKs in multicarrier: When a MS receives data to Primary Carrier and Secondary Carrier, the MS may transmit a HARQ feedback to a Carrier. Asymmetric ratio of DL and UL subframe in TDD: When the ratio of DL subframes and UL subframes is asymmetric and a MS receives data in two or more DL subframes, the MS may transmit a HARQ feedback in a UL subframe. Therefore we need to consider multiple bit feedback for a MS. Then how we can support it?

The structure for 2bit feedback There are three options. Option 1: two HARQ feedback channels separately MS transmits two HARQ channels for 1bit feedback separately. Option 2: two HARQ feedback channels jointly MS transmits a signal made from two HARQ channels. Option 3: one HARQ feedback channels MS transmits a HARQ channel modulated to QPSK. Orthogonal sequence 1-bit feedback 2-bit feedback [Option 1] [Option 2] [Option 3] [+1 +1 +1 +1] ACK of channel 1 ACK of 1st bit in channel 1 ACK/ACK in channel 1 [+1 -j +1 -j] : ACK/ACK of channel 1 : ACK/NACK of channel 1 [+1 -1 +1 -1] NACK of channel 1 NACK of 1st bit in channel 1 ACK/NACK in channel 1 [+1 +j +1 +j] [+1 -1 +1 -1] : NACK/ACK of channel 1 : NACK/NACK of channel 1 [+1 +1 -1 -1] ACK of channel 2 ACK of 2nd bit in channel 1 NACK/ACK in channel 1 [+1 -j -1 +j] : ACK/ACK of channel 2 : ACK/NACK of channel 2 [+1 -1 -1 +1] NACK of channel 2 NACK of 2nd bit in channel 1 NACK/NACK in channel 1 [+1 +j -1 -j] [+1 -1 -1 +1] : NACK/ACK of channel 2 : NACK/NACK of channel 2

The structure for 2bit feedback The comparison of the three schemes Normally if we only transmits HARQ feedback channel (HFBCH) for 1-bit feedback, we can map DL burst and HFBCH to one-to-one. Therefore we don’t need any HFBCH indication. In case of 2-bit feedback, option 1 and 2 need HFBCH indication because one or two HFBCHs can be allocated to a DL burst. But option 3 use the same resource with 1-bit feedback and we don’t need any HFBCH indication. Option 1 Option 2 Option 3 MS power ½ power in each channel 1 power in a channel Resource 2 HARQ feedback channels 1 HARQ feedback channels Performance Good Better DL control signaling overhead Need indication for channel index No need indication for channel index

Overhead comparison Assumption (Multiple codeword (MCW)) Overhead Bandwidth 10MHz DL/UL ratio 4:4 DL bursts per subframe 12 Total # of bursts in a frame 60 # DL burst with SCW 36 bursts Max. # of bursts associated to a UL subframe for UL HFBCH 48 # DL burst with MCW 12 bursts Option 1 & 2 Option 3 Notes Required HFBCHs 60 = 36 + 2x12 48 = 36 + 12 Required UL PRUs 4 {=ceil(60/18)} 3 {=ceil(48/18)} UL Overhead ratio 2.08 % 1.56 % Required bits to indicate the index of HFBCH in DL MAP (bits) 6 {=ceil(log2(60) } In case of option 3, the index of HFBCH follows the one of DL grant. Required DL PRUs 8 {=ceil(6x60x2/96)} DL Overhead ratio 3.13 % 0 % Total Overhead ratio 2.61 % 0.78 %

Overhead comparison Assumption (Asymmetric ratio of DL and UL subframe in TDD) Overhead Bandwidth 10MHz DL/UL ratio 5:3 DL bursts per subframe 12 Total # of bursts in a frame 60 # user with 1 DL burst 42 users (42 bursts) Max. # of bursts associated to a UL subframe for UL HFBCH 36 # user with 2 DL burst 9 users (18 bursts) Option 1 & 2 Option 3 Notes Required HFBCHs 60 Required UL PRUs 4 {=ceil(60/18)} UL Overhead ratio (%) 2.78 Required bits to indicate the index of HFBCH in DL MAP (bits) 6 {=ceil(log2(60) } In case of option 3, the index of HFBCH follows the one of DL grant. Required DL PRUs 8 {=ceil(6x60x2/96)} QPSK ¼ considered DL Overhead ratio (%) 3.3 Total Overhead ratio (%) 3.13 1.04 8/9 8

Conclusion We prefer option 3 to transmit 2bit HARQ feedback. There is a little performance loss but not critical. Moreover, we maintain the same capacity with 1bit feedback and apply the same indexing rule with 1bit feedback without any indication overhead.

Proposed AWD text Add the text below 15.3.9.2.2. HARQ Feedback Control Channel in C80216m-09_0386 (UL Ctrl DG)