Bit Selection for 16m Downlink Transmission and Simulation Result Document Number: IEEE C802.16m-09/0494r1 Date Submitted: 2009-03-02 Source: Jin Xu, Bo Sun E-mail: ZTE Corporation E-mail: Xiaolu Dong, Ying Du, Daning Gong E-mail: Venue: IEEE Session #60, Vancouver, BC, Canada xu.jin7@zte.com.cn sun.bo1@zte.com.cn duying@mail.ritt.com.cn RE: Comments on final draft of Channel Coding and HARQ Drafting Group Base Contribution: Purpose: To be discussed and adopted by TGm for use in the IEEE 802.16m Amendment Working Document. 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 >. Instruction • IEEE 802.16m uses adaptive HARQ scheme in the downlink [1]. • The overlapping of successive transmission/retransmission is serious with 16e’s bit selection method in 16m DL [2]. • New defined starting positions should be considered to reduce the overlapping between successive transmission/retransmission. - The gain of bit selection depends on the first retransmission particularly, considering the possibility of the following retransmission is very low. - Mother code bits should to be covered as much as possible within the first two transmissions . Proposed Bit Selection Method • the first transmission the second transmission the third transmission P2 2K 33.3333% K the fourth transmission S 33.3333% • Suggested in C80216m-09_0203r1 33.3333% • The first transmitting subpacket starts from the beginning of mother code. It contains the first L0 bits of the mother code, where L0 denotes the first subpacket length. The second subpacket contains the last L1 bits of the mother code. The starting position is Nm - L1, where Nm and L1 denote the mother code length and the second subpacket length respectively. Nm=3×Nep. The mother code bits are indexed from 0 to Nm -1. The third subpacket starts from the beginning of the first parity bit branch (or named “Y parity bits”). The starting position is Nep, where Nep denotes the number of bits in the encoder packet (before encoding). The forth subpacket starts from the beginning of the second parity bit branch (or named “W parity bits”). The starting position is 2*Nep. P1 K • Baseline for comparison • 4 SPIDs equally spaced SPIDi 3 N EP Pi 24 4 24 Where, Pi denotes the starting position for the ith subpacket. Li denotes the ith subpacket length. Simulation Results (1) • Simulation Parameters Parameters Assumption Bandwidth 10 MHz Number of subcarrier 1024 Frame length 5ms Channel estimation Perfect Channel code CTC Modulation 16 QAM for each transmission MIMO configuration SISO HARQ mode Adaptive Channel model PED B, 3km/h Code Length 384 bits Code Rate [123/256, 204/256, 204/256,204/256] Maximum number of retransmission 3 Simulation Results (2) Simulation Results (3) • Simulation Parameters Parameters Assumption Bandwidth 10 MHz Number of subcarrier 1024 Frame length 5ms Channel estimation Perfect Channel code CTC Modulation [16QAM, QPSK, QPSK, QPSK] MIMO configuration SISO HARQ mode Adaptive Channel model Veh-A, 30km/h Code Length 480 bits Code Rate [123/256, 199/256, 199/256,199/256] Maximum number of retransmission 3 Simulation Results (4) Simulation Results (5) • Simulation Parameters Parameters Assumption Bandwidth 10 MHz Number of subcarrier 1024 Frame length 5ms Channel estimation Perfect Channel code CTC Modulation [QPSK, QPSK, QPSK, QPSK] MIMO configuration SISO HARQ mode Adaptive Channel model PED B, 30km/h Code Length 960 bits Code Rate [131/256, 229/256, 229/256,229/256] Maximum number of retransmission 3 Simulation Results (6) Conclusion • From above analysis and simulation, we conclude that the proposed bit selection method could improve the performance of retransmission with small complexity. • We suggest this new bit selection method to be adopted for CTC IR HARQ in 16m. Reference [1] IEEE 802.16m-08/003r7, “IEEE 802.16m System Description Document” [2] C80216m-09_0203r1,“The Bit Selection Method of CTC IR HARQ for IEEE 802.16m” Text Proposal for Amendment Working Document •15.x.2.1 IR HARQ HARQ IR is used in 802.16m, by changing the starting position of the bit selection for HARQ retransmissions. The starting position for each subpacket Pi is defined as: (1)The first transmitting subpacket, starts from the beginning of mother code. The starting position for the first transmitting subpacket is P1=0; (2) The second subpacket contains the last L1 bits of the mother code. The starting position is for the second transmitting subpacket is P2=3×Nep-mod(L1, 3×Nep); (3) The third subpacket starts from the beginning of the first parity bit branch (named “Y parity bits”). The starting position is P3=Nep; (4) The forth subpacket starts from the beginning of the second parity bit branch (named “W parity bits”). The starting position is P4=2×Nep