非正交多址光通信系统信道均衡的虚拟时反方法

Virtual time reversal method for channel equalization in non-orthogonal multiple access optical communication systems

  • 摘要: 室内非正交多址(non-orthogonal multiple access, NOMA)可见光通信系统(visible light communications, VLC)可实现高速率多用户通信,但多径效应会造成通信可靠性及用户公平性明显下降,为此,提出一种虚拟时间反转技术(virtual time reversal mirror, VTRM)对NOMA-VLC进行信道均衡,消除多径效应对通信过程的影响。分析了多用户场景下室内NOMA-VLC系统模型及其通信光链路的特性,依据光链路增益的稀疏特性采用稀疏度自适应匹配追踪(sparsity adaptive matching pursuit,SAMP)算法,估计NOMA-VLC系统的信道冲激响应(channel impulse response, CIR)。在此基础上,采用VTRM方法对NOMA-VLC进行信道均衡,通过VTRM的时空聚焦特性减少信道衰落影响,并重构接收信号,抑制多径效应。理论分析和实验结果表明:经论文算法均衡后的NOMA-VLC系统,在满足前向纠错(forward error correction,FEC)误码率阈值的同时,用户1性能提高了4.4 dB,用户2性能提高了5.7 dB,两用户平均性能提高了5.05 dB,用户间性能差异由1.6 dB降为0.5 dB,为NOMA-VLC信道均衡提供了有效的解决方案。

     

    Abstract: Indoor non-orthogonal multiple access (NOMA) visible light communications (VLC) systems have the potential to enable high-rate multi-user communication. Nonetheless, the multipath effect may lead to a substantial reduction in communication reliability and user fairness. Therefore, a virtual time reversal mirror (VTRM) technology for NOMA-VLC channel equalization to eliminate the influence of multipath effect on communication performance was proposed. Initially, the indoor NOMA-VLC system model and the characteristics of communication optical links in multi-user scenarios were analyzed. To leverage the sparsity characteristics of optical links gains, the sparsity adaptive matching pursuit (SAMP) algorithm was adopted to estimate the channel impulse response (CIR) of NOMA-VLC systems. On this basis, the VTRM method was introduced to equalize the channel of NOMA-VLC, reducing the impact of channel fading through the spatio-temporal focusing characteristics of VTRM, and the received signal was reconstructed to suppress the multipath effect. The theoretical analysis and simulation results show that the NOMA-VLC system equalized by the proposed algorithm improves the performance of user 1 by 4.4 dB, user 2 by 5.7 dB, improves the average signal-to-noise ratio (SNR) of the two users by 5.05 dB, and reduces the performance difference between users from 1.6 dB to 0.5 dB, when the forward error correction (FEC) bit error rate (BER) threshold is met. Overall, this method provides an effective approach for NOMA-VLC channel equalization.

     

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