Iterative decoding and demodulation for single-antenna vector OFDM systems
Iterative decoding and demodulation for single-antenna vector OFDM systems
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DOI：
10.1109/tvt.2006.877695
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发表时间：
2006-07
影响因子：
6.8
通讯作者：
Hong Zhang;X. Xia
中科院分区：
文献类型：
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作者：
Hong Zhang;X. Xia
用于单天线系统的矢量正交频分复用（OFDM）是OFDM的推广，因为它将符号间干扰（ISI）信道转换为多个“无ISI”矢量信道，并且在其单抽头均衡（解调）中涉及矢量信道矩阵而不是信道系数。在频率选择性衰落信道上，增加矢量长度的矢量OFDM隐含地提供了比OFDM更多的信号空间分集优势。然而，蛮力解调器的复杂度在向量大小方面呈指数增加。本文研究了卷积编码矢量OFDM系统的迭代解调和译码，提出并比较了采用线性抵消和具有矢量长度线性复杂度的低复杂度解调方案。在介绍了以理想线性抵消为基准的解调器之后，研究了硬干扰抵消解调器和软干扰抵消解调器及其初始化方案。具有软干扰消除的解调器基于从先前迭代传递的码位概率信息动态地更新符号估计及其瞬时可靠性测量。它通过硬干扰消除了对解调器有害的误差传播，并显示出接近蛮力解调器的性能，同时大大降低了整体复杂度。大量的仿真结果表明，所提出的方案和向量长度的选择如何影响迭代接收机的收敛速度和可达到的性能
Vector orthogonal frequency-division multiplexing (OFDM) for single-antenna systems generalizes OFDM in that it converts an intersymbol interference (ISI) channel into multiple "ISI-free" vector channels and involves vector channel matrices instead of channel coefficients in its one-tap equalization (demodulation). Over frequency-selective fading channels, vector OFDM with increasing vector length implicitly offers more signal space diversity advantages over OFDM. However, the complexity of the brute force demodulator increases exponentially in terms of the vector size. In this paper, iterative demodulation and decoding for convolutionally coded vector OFDM systems are studied, and in particular, low-complexity demodulation schemes that employ linear cancellation and feature linear complexity in terms of the vector length are proposed and compared. Following the introduction of demodulators with ideal linear cancellation as benchmark, demodulators with hard and soft interference cancellation and their initialization options are studied. The demodulator with soft interference cancellation dynamically updates the symbol estimates and their instantaneous reliability measure based on the code bit probabilistic information passed from preceding iterations. It alleviates error propagation that is detrimental to the demodulator with hard interference cancellation and shows performance close to that of the brute force demodulator, with great overall complexity reduction. Extensive simulation results demonstrate how the choice among the presented schemes and the vector length affect the convergence rate and the achievable performance of the iterative receivers