A Two-Stage Feedback Protocol Based on Multipath Profile for MU-MIMO Networks

Aijing LI  Chao DONG  Zhimin LI  Qihui WU  Guodong WU  

IEICE TRANSACTIONS on Communications   Vol.E103-B   No.5   pp.559-569
Publication Date: 2020/05/01
Publicized: 2019/11/21
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2019EBP3102
Type of Manuscript: PAPER
Category: Network
MU-MIMO,  multipath profile,  feedback protocol,  USRP,  

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As a key technology for 5G and beyond, Multi-User Multi-Input Multi-Output (MU-MIMO) can achieve Gbps downlink rate by allowing concurrent transmission from one Access Point (AP) to multiple users. However, the huge overhead of full CSI feedback may overwhelm the gain yielded by beamforming. Although there have been many works on compress CSI to reduce the feedback overhead, the performance of beamforming may decrease because the accuracy of channel state degrades. To address the tradeoff between feedback overhead and accuracy, we present a two-stage Multipath Profile based Feedback protocol (MPF). In the first stage, compared with CSI feedback, the channel state is represented by multipath profile which has a smaller size but is accurate enough for user selection. Meanwhile, we propose an implicit polling scheme to decrease the feedback further. In the second stage, only the selected users send their CSI information to the AP to guarantee the low overhead and accuracy of steering matrix calculation. We implement and evaluate MPF with USRP N210. Experiments show that MPF can outperform alternative schemes in a variety of radio environments.