Constellation Rearrangement for IEEE 802 16 m IEEE

Constellation Rearrangement for IEEE 802. 16 m IEEE 802. 16 Presentation Submission Template (Rev. 9) Document Number: IEEE S 802. 16 m-08/807 Date Submitted: 2008 -7 -15 Source: Hyungho Park, Han. Guy Cho, Sungho Moon LG Electronic Inc. LG R&D Complex, 533 Hogye-1 dong, Dongan-gu, Anyang, 431 -749, Korea *<http: //standards. ieee. org/faqs/affiliation. FAQ. html> Voice: +82 -31 -450 -1934 E-mail: hyunghopark@lge. com, hgcho@lge. com, lge. com Venue: Macau, China Re : IEEE 802. 16 m-08/024 – Call for Contributions on Hybrid ARQ (PHY aspects) Base Contribution: IEEE C 802. 16 m-08/807 Purpose: To be discussed and adopted by TGm for 802. 16 m SDD 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/sect 6 -7. html#6> and <http: //standards. ieee. org/guides/opman/sect 6. html#6. 3>. Further information is located at <http: //standards. ieee. org/board/pat-material. html> and <http: //standards. ieee. org/board/pat >.

Constellation Rearrangement [1] • HARQ mode for HARQ PHY structure – Both Chase HARQ and IR HARQ has been considered in IEEE 802. 16 m – Chase HARQ can achieve power gain with low complexity, however it has performance loss as compared with IR HARQ operation. – For IR HARQ, the structure which is combined with the process of Partial IR and Full IR would be considered in 16 m over retransmissions. Although higher coding gain may be achieved, its buffering overhead lay burden on a receiver side with decreasing mother code rate. • Conventional Co. Re – High cost effective solution for enhancement of 16 m HARQ • High additional HARQ gain regardless of MS’s mobility • Low implementation complexity – Unequal bit error probability • In case of high modulation order, the symbol has different bit reliabilities such as MSB, SB (64 QAM), and LSB. These kinds of bit reliability difference result in performance degradation in course of channel decoding

Constellation Rearrangement [2] – Co. Re related Bitwise operations • Swapping operation: Averaging out the difference of bit reliability between component bits (MSB, LSB) within signal constellation. • Inversion operation: Averaging out the difference of bit reliability candidate component bits • Considerations on enhancement of Co. Re for IEEE 802. 16 m – High modulation order support • Higher order modulated symbol has a larger potential gain from constellation rearrangement due to its increased number of component bits for bitwise rearrangement (up to 64 QAM) – Both Chase and IR HARQ support • The performance of IR HARQ can be also improved by Co. Re in the way that recursive systematic or parity bits adopt the bitwise operations such as swapping and inversion in order to average the reliability of coded bits – Incorporation of Multiple Antenna configuration • MIMO related LLR combing is not straightforward because the symbols transmitted from each antenna interfere with each other. As the number of retransmission is increased, the interference is further aggravated in course of LLR combing.

Constellation Rearrangement [3] • Proposed Constellation Rearrangement – Horizontal bitwise mapping • Swapping operation exchanges component bits (i 1, q 1, i 2, q 2) on signal constellation in order to average the difference of bit error probabilities. • Inversion operation averages out error probabilities of candidate component bits by taking inversion of the corresponding bits on signal constellation – Vertical bitwise mapping • perform to exchange component bits between transmit antennas for averaging the channel difference.

Constellation Rearrangement [4] • Example of proposed Co. Re for 16 QAM – 1 st retransmission • Horizontal bitwise mapping: swapping bit reliability between MSB and LSB • Vertical bitwise mapping : exchanging to average spatial channel difference between MSBs – 2 nd retransmission • Horizontal bitwise mapping: inversion of LSBs for averaging out the difference of bit reliabilities between candidate component bits(10, 11, 00) • Vertical bitwise mapping: exchanging to average spatial channel difference between LSBs

Performance comparison [1] • Comparison of proposed Co. Re and 16 e Chase/IR HARQ Co. Re over Chase (30 km) Co. Re over Chase (120 km) Co. Re over IR, (30 km) Co. Re over IR (120 km) Nre = 1 1. 7 d. B 1. 9 d. B 0. 30 d. B 0. 35 d. B Nre = 2 2. 1 d. B 2. 2 d. B 0. 15 d. B Nre = 3 2. 8 d. B 3. 1 d. B 0. 47 d. B Performance gain (10% FER) Nre: Maximum number of retransmission – Proposed Co. Re obtains approximately 2~3 d. B FER gain over 16 e Chase HARQ regardless of MS’s mobility – Proposed Co. Re shows little improvement in link performance gain over 16 e CTC-IR HARQ

Performance comparison [2] • Simulation Parameters Assumption Bandwidth 10 MHz Number of subcarrier 1024 Frame length 5 ms Channel estimation Perfect Channel code CTC 1/2 Modulation 16 QAM MIMO configuration Tx: 2, Rx: 2 Resource allocation PUSC Channel model VEH A MS mobility 30 km/h, 120 km/h Receiver type Linear MMSE Maximum number of retransmission 1, 2, 3 Retransmission latency 10 ms

Performance comparison [3] • Chase HARQ w/ Co. Re vs 16 e Chase HARQ

Performance comparison [4] • Chase HARQ w/ Co. Re vs 16 e IR HARQ

Text Proposal for 802. 16 m SDD [1] ---------------------- Start of the Text ------------------------x. x HARQ mode x. x. x. Constellation Rearrangement Constellation rearrangement considering both horizontal and vertical bitwise mapping shall be adopted for IEEE 802. 16 m. x. x. x. 1. Horizontal bitwise mapping changes the bit position and its value on signal constellation in order to get temporal diversity gain during retransmissions through the following operations. A specific mapping rule is FFS. x. x. x. 2 Vertical bitwise mapping perform to exchange components bits between transmit antennas for averaging the channel difference. A specific bitwise mapping rule is FFS ---------------------- End of the Text --------------------------