Comparison of Two Differential Feedback Schemes for Beamforming IEEE Presentation Submission Template (Rev. 9) Document Number: IEEE C80216m-09_0528 Date Submitted: Source: Qinghua Li, Yuan Zhu, Eddie Lin, Shanshan Zheng, Jiacheng Wang, Xiaofeng Liu, Feng Zhou, Guangjie Li, and Yang-seok Choi Intel Corporation Venue: Session #60, Vancouver, Canada Re: TGm AWD Base Contribution: None Purpose: Discussion and adoption by TGm AWD Notice: This document does not represent the agreed views of the IEEE 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 Patent Policy: The contributor is familiar with the IEEE-SA Patent Policy and Procedures: and. Further information is located at and.

Outline Background Two differential schemes Performance comparison Complexity comparison Conclusions Proposed text

Background SDD supports differential feedback mode for SU and MU-MIMO precoding. Only “rotation based schemes” are supported. Two rotation based, differential schemes were proposed. –Scheme I: C80216m-09_0058r4.doc –Scheme II: C80216m-08_1187.doc Comparisons in throughput and complexity are made.

System Model is channel matrix of dimension. is beamforming matrix of dimension. is transmitted signal vector of dimension.

One-shot reset and differential feedback

Differential codebook

Scheme I Actual quantization at SS: Beamforming matrix reconstruction at BS: Beamforming at BS:

Scheme II Actual quantization at SS: Beamforming matrix reconstruction at BS: Beamforming at BS:

Codebook of Scheme I is compacter than Scheme II’s because of reduced dimension. Scheme I’s feedback matrix is N t xN s e.g. 4x1 while Scheme II’s is always N t xN t e.g. 4x4 regardless of rank. Scheme I has a codebook for each rank while Scheme II has a constant codebook.

Complexities 3-bit Scheme I (No. of real multiplications) 4-bit Scheme II (No. of real multiplications) 4x x Scheme II’s complexity is more than triple of Scheme I’s. – Matrix dimensions of Scheme II’s is greater than Scheme I’s.

System Level Simulations Isolate effect of reset (or initial) feedback – No reset feedback – Only measure performance of differential feedbacks No feedback error Scheme I’s 3-bit vs. Scheme II’s 4-bit

Simulation Parameters Parameter NamesParameter Values Network Topology57 sectors wrap around, 10 MS/sector MS ChannelITU PB3km/h Frame StructureTDD, 5DL, 3 UL Feedback Delay5ms Inter cell Interference ModelingOne tap fading Antenna Configuration4Tx, 2 Rx Code book configuration16e (4,1,3), TF with R tx, Diff(4,1,3,Ф) Tx Channel Correlation Matrix (only for TF code book) Ideal known to both MS and BS Q matrix update frequencyOnce for the whole simulation PMI errorfree PMI calculationML with SVD precoding vector System bandwidth10MHz, 864 data subcarriers Permutation typeAMC, 48 LRU CQI feedback1Subband=4 LRU, ideal feedback

4 Tx (0.5λ), 2Rx, 1 Stream SE gain over 16e 5%-ile SE gain over 16e Scheme I: 3-bit, 5 o 10.94%32.87% Scheme II: 4-bit, 0.9 ρ 7.09%25.65% Scheme I over Scheme II 3.60%5.75% Scheme I Scheme II

4 Tx (4λ), 2Rx, 1 Stream SE gain over 16e 5%-ile SE gain over 16e Scheme I: 3-bit, 20 o 6.08%18.86% Scheme II: 4-bit, 0.9 ρ 5.86%15.12% Scheme I over Scheme II 0.2%3.25% Scheme I Scheme II

4 Tx (Uncorrelated), 2Rx, 1 Stream SE gain over 16e 5%-ile SE gain over 16e Intel: 3-bit, 20 o 4.2%14.06% Samsung: 4-bit, 0.9 ρ 4.31%12.48% Intel over Samsung -0.1%1.41% Scheme I Scheme II

Conclusions In all cases, both SE and 5%-SE Scheme I outperforms Scheme II, except 0.1% SE loss in uncorrelated channel. –Scheme I’s overhead is less than Scheme II’s by 25%. –Scheme II’s codebook has unused codewords. –Since Scheme II’s codebook doesn’t have identity matrix, it often vibrates around optimum point. Scheme I’s complexity is three times less than Scheme II’s.

Proposed Text Adopt text in AWD.

Backup

Transition from reset feedback to differential feedback.