Unified Characterization and Precoding for Non-Stationary Channels
Unified Characterization and Precoding for Non-Stationary Channels
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DOI：
10.1109/icc45855.2022.9839118
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发表时间：
2022-02
期刊：
影响因子：
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通讯作者：
Zhibin Zou;M. Careem;Aveek Dutta;Ngwe Thawdar
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文献类型：
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作者：
Zhibin Zou;M. Careem;Aveek Dutta;Ngwe Thawdar
现代无线信道越来越密集和移动的，使得信道高度不稳定。时变分布和跨多个自由度的关节干扰的存在（例如，用户、天线、频率和符号）使得传统的预编码在实践中是次优的，并且导致了其统计的历史上较差的表征。我们工作的核心是推导出高阶推广的美世定理，将非平稳信道分解为组成衰落子信道（2-D特征函数），这些子信道在其自由度上是联合正交的。因此，传输具有最佳导出系数的这些本征函数最终减轻了这些维度上的任何干扰，并形成了所提出的联合时空预编码的基础。经预编码的符号在解调时直接在接收机处重构数据符号，从而通过减轻对任何互补解码的需要来显著地减少其计算负担。这些特征函数对于提取二阶信道统计是至关重要的，因此完全表征了底层信道。理论和仿真结果表明，在非平稳信道下，这种预编码方法比现有方法在20 dB时的误码率提高了104倍以上。
Modern wireless channels are increasingly dense and mobile making the channel highly non-stationary. The time-varying distribution and the existence of joint interference across multiple degrees of freedom (e.g., users, antennas, frequency and symbols) in such channels render conventional precoding sub-optimal in practice, and have led to historically poor characterization of their statistics. The core of our work is the derivation of a high-order generalization of Mercer’s Theorem to decompose the non-stationary channel into constituent fading sub-channels (2-D eigenfunctions) that are jointly orthogonal across its degrees of freedom. Consequently, transmitting these eigenfunctions with optimally derived coefficients eventually mitigates any interference across these dimensions and forms the foundation of the proposed joint spatio-temporal precoding. The precoded symbols directly reconstruct the data symbols at the receiver upon demodulation, thereby significantly reducing its computational burden, by alleviating the need for any complementary decoding. These eigenfunctions are paramount to extracting the second-order channel statistics, and therefore completely characterize the underlying channel. Theory and simulations show that such precoding leads to >104× BER improvement (at 20dB) over existing methods for non-stationary channels.