Journal of Applied Sciences ›› 2012, Vol. 30 ›› Issue (5): 455-460.doi: 10.3969/j.issn.0255-8297.2012.05.003

• Communication Engineering • Previous Articles     Next Articles

Threshold-Based Feedback Scheme for Multi-beam Opportunistic Beamforming in OFDMA System

LIU Shan1, YANG Wei1;2   

  1. 1. School of Electronic and Information Engineering, Beijing Jiaotong University, Beijing 100044, China
    2. National Mobile Communications Research Laboratory, Southeast University, Nanjing 210096, China
  • Received:2010-11-13 Revised:2012-01-04 Online:2012-09-24 Published:2012-09-25

Abstract:

 Multi-user MIMO-OFDMA is an important technology in the future wireless communications. In MIMO-OFDMA system, a large amount of feedback information has to be used to achieve multiuser diversity when all users are exploited. To deal with the problem, a multi-beam opportunistic beamforming scheme is proposed, in which partial multiuser diversity is achieved by setting a feedback threshold. Each user calculates the received signal to interference-plus-noise ratio (SINR) of each beam at individual subcarriers. The SINR value is transmitted to the base station only when it is larger than the threshold. The threshold is optimized to guarantee a target average resource utilization rate. The amount of feedback in the proposed scheme is quantified, and it is proved that feedback is limited to a fixed level. Simulation results indicate that optimal threshold can be determined effectively from a predefined resource utilization rate. Also, the feedback load can be reduced significantly with little capacity loss.

Key words: multiple-input-multiple-output (MIMO), orthogonal frequency division multiple access (OFDMA), opportunistic beamforming, feedback, threshold

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