Modification to OL Precoder Cycling Document Number IEEE

Modification to OL Precoder Cycling Document Number: IEEE S 80216 m-09_1918 Date Submitted: 2009 -08 -29 Source: Kiran Kuchi, J. Klutto Milleth, Padmanabhan M S CEWi. T, India Voice: E-mail: kkuchi@cewit. org. in, klutto@cewit. org. in Venue: Comments on P 802. 16 m/D 1: Base Contribution: IEEE C 80216 m-09_1918 Purpose: To discuss and adopt the proposed text in section 15. 3. 7. 1. 2. 1 To discuss in TGm for appropriate action. 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 >.

Advantage of precoder cycling Localized allocation uses N 1 cycling i. e. , same precoder is applied in a subband precoder changes from subband to subband N 1 cycling artificially introduces peaks and nulls in the channel With best band scheduling high multi-user diversity DRU and mini-band CRU uses SFBC or SM with precoding In channels with low frequency selectivity e. g. , PEDA, precoder cycling increases the diversity benefit

Current OL precoder cycling specification In the D 1 OL precoder cycles every N 1=4 PRUs N 1 cycling is optional in rank-1 OL region The precoder to be applied in each PRU is predetermined before permuting the subbands and mini-bands

Problems with current precoder cycling specification With multiple frequency partitions, In some cases, the subbands which are allocated in the same frequency partition are contiguous in frequency and they share the same precoder If the channel does not change across contiguous subbands, it adversely degrades best-band scheduling gain when user is allocated in the same frequency partition

Problems with current precoder cycling specification contd. In certain frequency partitions, the precoder allocated in mini-band CRUs DRUs take the same value Loss in diversity advantage in channels with low frequency selectivity such as PED-A Even in channels with high frequency selectivity, there will be loss in diversity advantage if the allocated min-band CRUs are adjacent in frequency

Proposed Remedy This problem is overcome if precoder cycling is specified in each frequency partition separately In each frequency partition (FP), define a logically contiguous sub-band CRU index to all the subbands and allocated in that FP define a logically contiguous mini-band CRU index to all the mini band CRUs allocated in that FP define a logically contiguous mini-band DRU index to all the mini band DRUs allocated in that FP In each FP, For subband CRUs, Precoder cycling based on logical sub-band index For mini-band CRUs, Precoder cycling based on logical miniband-CRU index For mini-band DRUs, Precoder cycling based on logical miniband-DRU index

Precoder cycling: illustration Black color: precoder cycling before FP Red color: logical index based cycling Precoder allocation before FP C(0), C(0) C(1), C(0), C(0) C(1), C(0) C(1), C(1) C(0), C(0), C(1) C(0) C(1), C(0) C(1), C(1) C(0), C(0), C(1) C(0), C(0) C(1), C(1) C(1), C(0) C(1),

Precoder cycling illustration In CRU(FP 1), if precoder cycling is done before frequency partition, two contiguous subbands are allocated with same precoder C(0) Loss in best-band scheduling gain if channel does not vary across these sub-bands With the proposed precoder cycling two distinct precoders will be allocated in these subbands In DRU(FP 3), current method allocates same precoder C(1) to all PRUs. The proposed method cycles between C(0) and C(1) sequentially

Proposal Adopt the text proposed in C 80216 m-09_1918 for OL precoder cycling in OL MIMO region In OL region, the MS need not know the OL precoder, the proposed solution does not increase implementation complexity at AMS.