HARQ Bit Selection Algorithm IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number: IEEE C802.16m-09/0504r1 Date Submitted: 2009-3-10 Source: 1Zheng Yan-Xiu, Yu-Chuan Fang, Chang-Lan Tsai, Chung-Lien Ho, Hsi-Min Hsiao, Ren-Jr Chen Chien-Yu Kao, Cheng-Ming Chen, Yu-Tao Hsieh, Jen-Yuan Hsu, Pang-An Ting 1E-mail: zhengyanxiu@itri.org.tw. ITRI Venue: IEEE Session #60, Vancouver Base Contribution: N/A IEEE 802.16m-09/0012, “Call for Comments on Amendment Working Document” Target topic: “15.3.11 Channel coding and HARQ”. 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 >.

Bit Selection: Cocktail Therapy Bit Grouping: (Harmonization proposed by MediaTek, Huawei and Samsung) Method: Avoid mapping the encoded bits of the same indices onto the same bit level. Map the contiguous encoded bits different bit levels in 16QAM and 64QAM. Gain: provide better protection in the first transmission Prioritized Circular Reading (PCR): Method: control the prioritized code bits on MSB or LSB of a symbol and minimize complexity to the least Gain: obtain diversity, e.g. frequency domain diversity Priority Swapping (PS): Method: retransmit coded bits in MSB to LSB to average modulation effect Gain: acquire constellation diversity gain Shifted IR Redundancy Version Selection (SIRRVS): Method: improve performance by selecting code bits at first when complete code bits are selected Gain: enhance code bits influence in the later transmission to acquire coding gain Bit Inverting (BI): Method: exclusive OR code bits Gain: acquire more constellation diversity gain 2

Shifted IR redundancy version selection (SIRRVS) To select parity bits, Y1 & Y2, at first, when complete code bits are selected.

Illustration for CC-HARQ (1/3) 16-QAM, R=1/2 BI PCR PS

Illustration for CC-HARQ (2/3) 64-QAM, R=1/2

Illustration for CC-HARQ (3/3) represents the coded bit sequence at the first transmission, whose length is Lk. Fk represents the initial position of bit selection for the k-th subpacket, where k is the subpacket index and k = 0, 1, 2, 3. Thus the initial bit selected is denoted as . When the initial position is determined, the bits are accessed contiguously and circularly to generate the k-th subpacket for retransmissions. (k = 0 for the first transmission)

Definition of Parameters Ex: NT = NDT + NPT 1 stream: 108 = 102 + 6 2 streams: 108 = 96 + 12 4 streams: 108 = 92 + 16 7

Proposed bit selection for CC-HARQ PS BI PCR Initial position New address 8

Illustration for IR-HARQ (1/3) 16-QAM, R=1/2, NEP=12 PS PCR SIRRVS length for Group #1 length for Group #2 2TX 3TX 4TX 9

Illustration for IR-HARQ (2/3) 64QAM, R=1/2, NEP=12 length for Group #1 length for Group #2 2TX 3TX 4TX

Illustration for IR-HARQ (3/3) 16QAM, R=3/4, NEP=12 length for Group #1 length for Group #2 2TX 3TX 4TX

Proposed bit selection for IR-HARQ PS PCR BI PCR SIRRVS 12

Procedure of channel interleaver The modified channel interleaver for CTC comprises several parts. Bit separation (16e) Subbock interleaving (16e) Bit grouping (16e[1] or MBG[6]) Bit selection (proposed algorithm) [1] 16e represents the IEEE 802.16e. [6] MBG (modified bit grouping) denotes the proposal of Huawei, Samsung and MTK, IEEE C802.16m-09/0665, “Proposed Text of CTC Bit grouping for IEEE 802.16m Amendment.”

Simulation scenario

Simulation cases

Simulation Results In short, the simulation results show the combination of modified bit grouping (MBG) [6], prioritized circular reading (PCR) and priority swapping (PS) has the best performance, so only its results are shown in this contribution.

Fig. 7(a) MBG (modified bit grouping) denotes the proposal of Huawei, Samsung and MTK, IEEE C802.16m-09/0665, “Proposed Text of CTC Bit grouping for IEEE 802.16m Amendment.”

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Conclusions The proposed bit selection algorithm improve the HARQ technique significantly regardless of the bit grouping methods. The proposed bit selection cooperating with the modified bit grouping [6] has the better performance than with the 16e scheme.

References [1] IEEE P802.16 Rev2 / D8, “Draft Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Broadband Wireless Access,” Dec. 2008. [2] IEEE 802.16m-08/003r7, “IEEE 802.16m System Description Document” [3] IEEE 802.16m-07/002r7, “802.16m System Requirements” [4] IEEE C802.16m-08/043, “Style guide for writing the IEEE 802.16m amendment” [5] IEEE 802.16m-08/050, “IEEE 802.16m Amendment Working Document” [6] IEEE C802.16m-09/0665, “Proposed Text of CTC Bit grouping for IEEE 802.16m Amendment” [7] IEEE C802.16m-09/0573, “Bit Grouping Performance Comparison for Bit Priority Mapping and 16e Mapping in the 1st Transmission”