1. Proposal for the Bit Selection Scheme for HARQ Document Number: IEEE C802.16m-09/0879 Date Submitted: 2009-04-27 Source: 1 Chien-Yu Kao, Yu-Tao Hsieh, Yu-Chuan Fang, 2 Zheng Yan-Xiu, Pang-An Ting. Email: 1 Eric_Kao@itri.org.tw, 2 zhengyanxiu@itri.org.tw ITRI Venue: IEEE Session #61, Cairo Base Contribution: None Re: IEEE C802.16m-09/0020 “Call for Contributions on Project 802.16m Amendment Working Document (AWD) Content”, Category: AWD comments / Area: Chapter 15.3.12 (Channel coding HARQ-PHY) “Comments on AWD 15.3.12 Channel coding HARQ-PHY” Purpose: Propose to be discussed and adopted by TGm for the use in Project 802.16m. 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: and.http://standards.ieee.org/guides/bylaws/sect6-7.html#6http://standards.ieee.org/guides/opman/sect6.html#6.3 Further information is located at and.http://standards.ieee.org/board/pat/pat-material.htmlhttp://standards.ieee.org/board/pat

2. Agenda Introduction Detail Description for the Proposal Simulation Results Conclusions Proposed Text

3. 3 Introduction for IR-HARQ in current AWD For downlink IR-HARQ in current AWD, the starting point for the bit selection algorithm as described as the table below. For uplink HARQ, the starting position for the bit selection algorithm as described as following equation is determined as a function of SPID for the following equation. For uplink HARQ, subpackets shall be transmitted in sequential order. In other words, for the t-th transmission, the subpacket ID shall be set to SPID = t mod 4. SPIDStarting position 0 1 2 (TBD) 3 (TBD) Table 15.x.2-1. Starting position determination for downlink HARQ ZTE’s latest proposal (ref. to C80216m-09_0858)

4. 4 Spatial diversity for MIMO (1/2) The common way is shown in Fig. (a). The modulation symbols, indexed as 0, 1, 2, etc., are distributed into 2 streams. For retransmission, all symbols are circularly shifted to the right by one tone length, i.e., all bits are shifted by N mod bits, where N mod is the modulation order, to exchange the assigned streams and obtain spatial diversity gain as shown in Fig. (b).

5. Spatial diversity for MIMO (2/2) LGE’s CoRe method considers spatial diversity, where two CoRe versions only switch bits within a tone between 2 streams. So, it may not work well for more Tx antennas (e.g. Tx=4). Circularly shifting by multiple of tones in bit selection can release this constraint –Proposed algorithm doesn’t average bit reliability as what CoRe does –More spatial diversity order (>2) can be expected –Not violating SDD –CoRe is kept by a bit-level interleaver (across different antenna) within a tone Proposed algorithm works for both DL and UL in a unified equation 5

6. 6 Illustration for IR-HARQ (1/2) Ex. DL, 64-QAM, R=½, Nep=12 The order of SPID in this example is 0  1  3  2. Control spatial

7. Illustration for IR-HARQ (2/2) Ex. UL, 64-QAM, R=½, Nep=12 The order of SPID for UL is 0  1  2  3. 7 Control spatial

8. 8 Proposed bit selection for IR-HARQ Control spatial

9. 9 Simulation Parameter ParametersAssumption Bandwidth10 MHz Number of subcarrier1024 Frame length5ms Channel estimationPerfect Channel codeCTC ½, 3/4, Modulation16 QAM, 64QAM MIMO configurationTx: 2, Rx:2 Resource allocationDistributed Channel modelPED B, VEH A MS mobility3km/h, 60km/h Receiver typeLinear MMSE Maximum number of retransmission1, 2 Retransmission latency10ms

10. 10 Simulation cases (1/2) - SPID order and CoRe indication In these simulation results, the order of SPID is a sequential order in UL for both 16QAM ½ and 64QAM ½. But for DL, the order is 0  1  3  2 for 16QAM ½ and 0  1  2  3 for 64QAM ¾. We also adopt ZTE’s latest proposal as starting point for DL IR-HARQ. For CoRe indication, it is assumed to be 0 and 1 by turns for both UL and DL. And all transmissions/retransmissions use the same CoRe version. Compared proposals: –MediaTek(MTK) (ref. to C80216m-09_0868) : 16e with modified bit grouping –LG (ref. to C80216m-09_0676r1 (with bit inverter)) : 16e with modified bit grouping and CoRe –ITRI : proposal with modified bit grouping and LG’s modified CoRe without bit inverter (ref. to C80216m-09_0868) For retransmissions, the simulations of ITRI, LG are all based on the modified bit grouping proposed by MediaTek.

11. Simulation cases (2/2) - Mapping Rule LG’s CoRe with bit inverter (ref. to C80216m-09_0676r1) LG’s modified CoRe without bit inverter (ref. to C80216m-09_868) ConstellationN cbps CRVMapping rule First symbolSecond symbol 16 QAM40b0b0 b1b1 b2b2 b3b3 --b4b4 b5b5 b6b6 b7b7 -- 41b1b1 b4b4 b3b3 b6b6 --b5b5 b0b0 b7b7 b2b2 -- 64 QAM60b0b0 b1b1 b2b2 b3b3 b4b4 b5b5 b6b6 b7b7 b8b8 b9b9 b 10 b 11 64 QAM61b2b2 b7b7 b0b0 b5b5 b 10 b3b3 b8b8 b1b1 b6b6 b 11 b4b4 b9b9

12. Simulation Results (1/8) - UL IR-HARQ 16QAM ½, PED-B 3km/hr

13. Simulation Results (2/8) - UL IR-HARQ 16QAM ½, VEH-A 60km/hr

14. Simulation Results (3/8) - UL IR-HARQ 64QAM ½, PED-B 3km/hr

15. Simulation Results (4/8) - UL IR-HARQ 64QAM ½, VEH-A 60km/hr

16. Simulation Results (5/8) - DL IR-HARQ 16QAM ½, PED-B 3km/hr

17. Simulation Results (6/8) - DL IR-HARQ 16QAM ½, VEH-A 60km/hr

18. Simulation Results (7/8) - DL IR-HARQ 64QAM ¾, PED-B 3km/hr

19. Simulation Results (8/8) - DL IR-HARQ 64QAM ¾, VEH-A 60km/hr

20. Conclusions This proposal is compatible with current LGe’s CoRe design (w/ bit inverter) for # Tx ant. 2. This proposal can be easily implemented with a circular shifter without increasing additional complexity. One unified equation for both fixed starting point of DL and sequential transmission of UL.

21. Proposed Text ---------------------------------------------------- Text Start -------------------------------------------------- 15.x.1.5.1.8. Bit selection and repetition Bit selection and repetition are performed to generate the subpacket. Let N CTC, k be the number of coded bits that shall be transmitted for the k-th FEC block. The value of N CTC, k is calculated by the following equation The index in the HARQ buffer for the j-th bit transmitted for the k-th FEC block, u k, j, i, shall be: where i is the subpacket ID (SPID = i), P i, k is the starting position for the i-th subpacket of the k-th FEC block as specified in 15.x.2.1, and is the buffer size for the k- th FEC block.