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S80216maint-08_240r1.ppt MIMO/BF in Release 1.x: Discussion on Codebook Computational Complexity Sangwoo Lee, Jiyun Seol, Keun Chul Hwang, Mune Joon, Inseok Hwang Samsung Copyright 2006 WiMAX Forum “WiMAX Forum™” and "WiMAX Forum CERTIFIED™“ are registered trademarks of the WiMAX Forum™. * All trademarks are the properties of their respective owners.
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Purpose of this presentation
S80216maint-08_240r1.ppt 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.
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Problem statements Codebook computation example
S80216maint-08_240r1.ppt 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
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Suggestion on Codebook for Rel.1.x
S80216maint-08_240r1.ppt 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
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Performance Simulation
S80216maint-08_240r1.ppt 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
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Computation Complexity
S80216maint-08_240r1.ppt Computation Complexity Assumption: 4X2 Computational Complexity (per codeword) 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.
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S80216maint-08_240r1.ppt Conclusions Codebook computational complexity can be reduced by including the rank-1 codebook vectors in rank-2 codebook matrices without performance degradation.
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Appendix: Proposed V(4,2,6)
S80216maint-08_240r1.ppt Appendix: Proposed V(4,2,6) V(4,2,6) in current 16e is generated with Householder and concatenation HC(V(4,1,3), V(3,1,3) Current 16e: V(4,2,6) = HC(V(4,1,3),V(3,1,3)) For V(4,2,6), we propose to use H(V(4,1,6)) to reduce the computation complexity Proposed : V(4,2,6) = H(V(4,1,6))[1 2+mod(k,3)]
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Appendix: Performance of proposed V(4,2,6)
S80216maint-08_240r1.ppt Appendix: Performance of proposed V(4,2,6) Performance of proposed codebook is the same as that of current 16e codebook. (difference is less than 0.11dB)
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