Performance Analysis of Channel Extrapolation in FDD Massive MIMO Systems
Performance Analysis of Channel Extrapolation in FDD Massive MIMO Systems
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DOI：
10.1109/twc.2020.2967711
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发表时间：
2019-03
影响因子：
10.4
通讯作者：
François Rottenberg;Thomas Choi;Peng-Ju Luo;C. Zhang;A. Molisch
中科院分区：
文献类型：
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作者：
François Rottenberg;Thomas Choi;Peng-Ju Luo;C. Zhang;A. Molisch
频分双工（FDD）大规模多输入多输出（MIMO）系统下行链路的信道估计是众所周知的，因为在MIMO系统中，训练量通常随发射天线数量的增加而增加。在本文中，我们考虑了从上行导频估计到下行频带的信道频率响应外推的解决方案。这大大减少了下行导频开销，并完全消除了对用户反馈的需求。代价是信道估计的质量下降，降低了下行链路的频谱效率。我们首先证明了传统的估计器不能达到合理的精度。我们建议使用高分辨率信道估计。推导了外推信道均方误差（MSE）的Cramer-Rao下界（CRLB）。进一步推导了不完全信道状态信息（CSI）与下行链路用户性能之间的关系。通过数值模拟验证了基于外推的FDD大规模MIMO性能，并与相应的时分双工（TDD）系统进行了比较。考虑外推性能的优点包括信道MSE，波束形成效率，外推范围，频谱效率和未编码符号错误率。我们的主要结论是，信道外推是FDD大规模MIMO系统的可行解决方案。
Channel estimation for the downlink of frequency division duplex (FDD) massive multiple-input-multiple output (MIMO) systems is well known to generate a large overhead as the amount of training generally scales with the number of transmit antennas in a MIMO system. In this paper, we consider the solution of extrapolating the channel frequency response from uplink pilot estimates to the downlink frequency band. This drastically reduces the downlink pilot overhead and completely removes the need for a feedback from the users. The price to pay is a degradation in the quality of the channel estimates, which reduces the downlink spectral efficiency. We first show that conventional estimators fail to achieve reasonable accuracy. We propose instead to use high-resolution channel estimation. We derive the Cramer-Rao lower bound (CRLB) of the mean squared error (MSE) of the extrapolated channel. Furthermore, a relationship between the imperfect channel state information (CSI) and the downlink user performance is derived. The extrapolation-based FDD massive MIMO performance is validated through numerical simulations and compared to a corresponding time division duplex (TDD) system. Considered figures of merit for extrapolation performance include channel MSE, beamforming efficiency, extrapolation range, spectral efficiency and uncoded symbol error rate. Our main conclusion is that channel extrapolation is a viable solution for FDD massive MIMO systems.