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| Adaptive robust beamformer for multi-pair two-way relay networks with imperfect channel state information |
| Jin Wang, Feng Shu, Ri-qing Chen, Yu-di Cui, Yu Chen, Jun Li |
| School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China; College of Computer and Information Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China; National Mobile Communications Research Laboratory, Southeast University, Nanjing 210096, China |
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Abstract In wideband multi-pair two-way relay networks, the performance of beamforming at a relay station (RS) is intimately related to the accuracy of the channel state information (CSI) available. The accuracy of CSI is determined by Doppler spread, delay between beamforming and channel estimation, and density of pilot symbols, including transmit power of pilot symbols. The coefficient of the Gaussian-Markov CSI error model is modeled as a function of CSI delay, Doppler spread, and signal-to-noise ratio, and can be estimated in real time. In accordance with the real-time estimated coefficients of the error model, an adaptive robust maximum signal-to-interference-and-noise ratio (Max-SINR) plus maximum signal-to-leakage-and-noise ratio (Max-SLNR) beamformer at an RS is proposed to track the variation of the CSI error. From simulation results and analysis, it is shown that: compared to existing non-adaptive beamformers, the proposed adaptive beamformer is more robust and performs much better in the sense of bit error rate (BER); with increase in the density of transmit pilot symbols, its BER and sum-rate performances tend to those of the beamformer of Max-SINR plus Max-SLNR with ideal CSI.
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Received: 28 April 2015
Published: 07 March 2016
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多用户对双向中继系统自适应稳健波束成形
目的：在宽带多用户对双向中继系统中，中继的波束成形性能与信道状态信息（channel state information，CSI）的准确性密切相关。CSI的准确性取决于多普勒扩展、信道估计反馈时延、导频符号数目和发射功率等因素。本文将Gaussian-Markov信道估计误差模型系数建模为反馈时延、多普勒扩展和信噪比的联合函数。在估计出的实时CSI误差系数基础上，设计一种基于最大化信干噪比和最大化信泄噪比准则的自适应稳健波束成形算法。该算法能实时跟踪无线信道CSI估计误差的变化，提高系统的和速率和误码性能。
创新点：建模Gaussian-Markov误差模型中的信道估计误差系数为反馈时延、多普勒扩展和信噪比的联合函数。在此基础上，构建一种基于最大化信干噪比和最大化信泄噪比准则的自适应稳健波束成形算法。
方法：首先，根据Gaussian-Markov信道估计误差模型，利用统计理论，设计一种不完全信道状态信息下基于最大化信干噪比和最大化信泄噪比准则的波束成形算法。然后，将信道估计误差模型系数建模为反馈时延、多普勒扩展和信噪比的联合函数。通过实时估计CSI时延和信道估计器引起的误差系数，实时设计匹配于信道变化的稳健波束成形器。最后，通过仿真结果验证该算法的正确性、稳健性和自适应性。
结论：仿真表明：提出的自适应稳健波束成形算法误码率性能明显优于现有的非自适应算法，并且随着导频符号数目的增加，该算法的性能会逐渐趋于理想CSI条件下的性能。
关键词：
多用户对双向中继,
自适应稳健波束成形,
信道状态信息,
最大化信干噪比,
最大化信泄噪比
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