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Soft-Input Soft-Output Block Decision Feedback Equalization for ISI Channels
IEEE Transactions on Communications ( IF 7.2 ) Pub Date : 2021-06-08 , DOI: 10.1109/tcomm.2021.3087205
Congji Yin , Wenjiang Feng , Junbing Li , Xiaolong Bao , Guojun Li

In this paper, a new class of soft-input soft-output block decision feedback equalizer (BDFE) for turbo equalization over inter-symbol interference (ISI) channels under minimum mean-square error (MMSE) criterion is proposed. First, the BDFE which employs both the a posteriori moments of estimated symbols and the a priori moments of unestimated symbols is investigated, and two recursive schemes are derived to reduce the complexity. Then, to mitigate error propagation, the bidirectional BDFE (Bi-BDFE) consisting of a forward BDFE and a backward BDFE is proposed. Furthermore, a threshold is employed to reduce the number of inverse matrix update process for the BDFE (T-BDFE), which can attain a flexible trade-off between complexity and performance. Finally, the bidirectional equalization is introduced into a low-complexity approximate solution of the BDFE (Bi-LC-BDFE) to further reduce the complexity and obtain time diversity gain, which utilizes a time-invariant covariance matrix. Simulation results show that the proposed equalizers significantly outperform the block linear equalizer (BLE), the exact MMSE-based linear equalizer (Exact-MMSE-LE) and the soft-decision feedback equalizers (SDFE), while keeping a similar complexity as the BLE. In addition, the Bi-BDFE can achieve better performance than the Max-Log-MAP equalizer while its complexity is on the same order as the BDFE.

中文翻译:


ISI 通道的软输入软输出模块判决反馈均衡



本文提出了一类新型软输入软输出块判决反馈均衡器(BDFE),用于在最小均方误差(MMSE)准则下对符号间干扰(ISI)信道进行涡轮均衡。首先,研究了同时采用估计符号的后验矩和未估计符号的先验矩的BDFE,并导出了两种递归方案以降低复杂度。然后,为了减轻错误传播,提出了由前向 BDFE 和后向 BDFE 组成的双向 BDFE (Bi-BDFE)。此外,采用阈值来减少BDFE(T-BDFE)的逆矩阵更新过程的数量,这可以实现复杂性和性能之间的灵活权衡。最后,将双向均衡引入BDFE的低复杂度近似解(Bi-LC-BDFE)中,利用时不变协方差矩阵,进一步降低复杂度并获得时间分集增益。仿真结果表明,所提出的均衡器显着优于块线性均衡器 (BLE)、基于精确 MMSE 的线性均衡器 (Exact-MMSE-LE) 和软判决反馈均衡器 (SDFE),同时保持与 BLE 相似的复杂度。此外,Bi-BDFE 可以实现比 Max-Log-MAP 均衡器更好的性能,而其复杂度与 BDFE 处于同一量级。
更新日期:2021-06-08
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