[Modification of CL-MIMO Codebooks] IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number: IEEE S802.16maint-08/240r2 Date Submitted: 2008-05-14 Source: Sangwoo Lee, Jiyun Seol, Keun Chul Hwang, Mune Joon,Inseok Hawng Voice: 82-31-279-7349 Samsung Electronics E-mail: sangwoo07.lee@samsung.com Hassan Yaghoobi Intel Corporation E-mail: hassan.yaghoobi@intel.com Peiying Zhu Nortel E-mail: pyzhu@nortel.com *<http://standards.ieee.org/faqs/affiliationFAQ.html> Venue: IEEE 802.16 Session #55 Base Contribution: Purpose: For discussion and approval by IEEE802.16 Maintenance TG 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 >.

Purpose of this presentation Share some views on how to reduce the codebook computational complexity. Suggest a codebook generation rule based on current 16e codebook.

Problem statements Codebook computation example In current 16e codebook for 2Tx, rank-1 codebook vectors are the first columns of rank-2 codebook matrices  MS’s codebook computation burden can be reduced by calculating only the rank-2 metric For 4Tx codebooks, rank-1 codebook vectors are not the first columns of rank-2 codebook matrices.  MS’s should calculate the rank-1 and rank-2 metric for rank selection separately. Rank=1 Rank=2

Suggestion on Codebook for Rel.1.x For 4Tx codebook, we suggest to include the rank-1 codebook vectors in rank-2 codebook matrices. Current 16e: The codebook generated with HE operation is composed with the last M columns, with which the rank-1 codebook vectors are excluded in rank-2 codebook matrices. Note that rank-1 codebook vectors are the first columns of H(v) Proposed : For the codebook generated with HE operation, we propose to take the first M columns to include the rank-1 codebooks Example: Proposed V(4,2,3) Current 16e: V(4,2,3) = H(V(4,1,3)):,3:4 Proposed : V(4,2,3) = H(V(4,1,3)):,1:2

Performance Simulation Performance of proposed codebook is the same as that of current 16e codebook. Simulation results (4X2, perfect CE, 10dB Tx SNR) Mean PD SINR (dB) Current 16e Proposed Difference (proposed-16e) 3bits V(4,2,3) 11.58dB 11.60dB +0.02dB

Computation Complexity Assumption: 4X2 Computational Complexity (per codeword) In one calculation, reduction of complexity is about 31% Rank=1 Rank=2 Current 16e Proposed 35 CMs 24 CMs (31% reduction) Current 16e: 35 CMs are needed Rank-1: 11 Complex Multiplication (CMs)= 8 CMs for Hvk + 2 CMs for || ||2 + 1 CMs for . Rank-2: 24 CMs = 16 CMs for HVk + 6 CMs for VkHHHHVk + 2 CMs for det(). Proposed: Only 24 CMs are needed, since the rank-1 calculation of 1+  *||Hvk||2 can be obtained with (1,1) element of rank-2 matrix of I+  * VkHHHHVk.

Conclusions Codebook computational complexity can be reduced by including the rank-1 codebook vectors in rank-2 codebook matrices without performance degradation.