• Title/Summary/Keyword: channel quality indication (CQI)

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Dynamic Feedback Selection Scheme for User Scheduling in Multi-user MIMO Systems (다중 사용자 MIMO 시스템의 사용자 스케쥴링을 위한 동적 피드백 선택 기법)

  • Kim, I-Cheon;Kang, Chung G.
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.4
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    • pp.646-652
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    • 2015
  • In this paper, the system-level performance is evaluated for the feedback scheme on the pre-coding matrix index (PMI) and channel quality indication (CQI), which are required for user selection in the multi-user MIMO system. Our analysis demonstrates that the number of users, the number of selected users, and codebook size are the key factors that govern the performance of the best companion grouping (BCG)-based user scheduling. Accordingly, we have confirmed that the probability of forming the co-scheduled user group is determined by these factors, which implies that the number of PMI's and codebook size can be dynamically determined so as to maximize the average system throughput as the number of users varies in the cell.

Novel schemes of CQI Feedback Compression based on Compressive Sensing for Adaptive OFDM Transmission

  • Li, Yongjie;Song, Rongfang
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.5 no.4
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    • pp.703-719
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    • 2011
  • In multi-user wireless communication systems, adaptive modulation and scheduling are promising techniques for increasing the system throughput. However, a mass of wireless recourse will be occupied and spectrum efficiency will be decreased to feedback channel quality indication (CQI) of all users in every subcarrier or chunk for adaptive orthogonal frequency division multiplexing (OFDM) systems. Thus numerous limited feedback schemes are proposed to reduce the system overhead. The recently proposed compressive sensing (CS) theory provides a new framework to jointly measure and compress signals that allows less sampling and storage resources than traditional approaches based on Nyquist sampling. In this paper, we proposed two novel CQI feedback schemes based on general CS and subspace CS, respectively, both of which could be used in a wireless OFDM system. The feedback rate with subspace CS is greatly decreased by exploiting the subspace information of the underlying signal. Simulation results show the effectiveness of the proposed methods, with the same feedback rate, the throughputs with subspace CS outperform the discrete cosine transform (DCT) based method which is usually employed, and the throughputs with general CS outperform DCT when the feedback rate is larger than 0.13 bits/subcarrier.