基于信道质量干扰比量化准则的有限反馈波束形成

Channel Quality-to-Interference Ratio Quantization Criterion  for Limited Feedback Beamforming Systems

  • 摘要: 波束形成技术是MIMO无线通信系统的关键技术之一,它能够使系统有效性与可靠性都得到显著地提高,但它需要系统所有在线用户反馈其全部瞬时变化的信道状态信息,这将使拥挤的无线频谱资源更加紧张。为了降低系统所需的反馈量,本文结合LTE系统MIMO下行链路环境,将采用DFT基码本对信道状态信息进行量化,仅需要用户给基站反馈其最优码本索引;同时本文也首次提出基于信道质量干扰比为量化准则的一种新波束形成方案,并给出了质量干扰比的详细计算公式。此量化准则能够兼顾到量化信道的质量信息和子信道之间的互干扰信息,比传统的量化准则更具优良的性能。仿真结果表明,本文提出方案不仅可以明显降低系统反馈量,而且其性能超过随机波束形成,尤其在低信噪比场景下甚至优于特征波束形成的系统性能。理论分析和仿真验证表明本文方案是一种比较好的波束形成方案。

     

    Abstract: Beamforming is one of the key techniques for the multiple-input multiple-output (MIMO) wireless communication systems, which enables the system to achieve higher transmission reliability when the full instantaneous channel state information(CSI) of all the online users are available. This makes the crowded spectrum resources become more limited. In this paper, since the Discrete Fourier Transform (DFT) based codebook is simple to generate, it is employed to quantize CSI so that the quantity of channel feedback of the system is reduced in the downlink of Long Term Evolution (LTE) with MIMO. Moreover, a novel beamforming scheme adopting the DFT-based codebook is also proposed, which dramatically reduces the quantity of feedback. The proposed beamforming scheme is based on the channel quality-to-interference ratio (QIR) quantizing criteria, which is defined in the paper. The QIR quantizing criteria jointly considers the influences of the quality of quantized channels and the mutual interference among the subchannels. Hence, the proposed scheme outperforms the traditional quantizing criteria, where only one factor is concerned. The extensive simulation results verify that the novel beamforming scheme can reduce the quantity of feedback greatly. Besides, its throughput is better than that of the random beamforming (RBF) with a little feedback (that is, the logarithm of the codebook size). The simulations also show that, under the low SNR scenario, the performance of the proposed scheme, with rather small feedback, is even better than that of the eigen-beamforming (EBF). Thus, the novel beamforming scheme proves to be effective.

     

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