We investigate the feasibility of second-order statistics-based blind channel estimation in the context of two-hop full-duplex relay systems. To that end, the performance of blind and traditional pilot-based (training sequence based) channel estimation approaches are compared. This is accomplished by deriving the Cramer-Rao Lower Bound (CRLB) expressions for both blind and pilot-based schemes, and comparing them to each other and to the mean-squared error (MSE) values measured via simulation. Post-equalization SINR expressions are also derived for both blind and pilot-based methods. Furthermore, a modified post-equalization SINR expression, where the channel estimation error is replaced by the inverse of the Fisher information matrix (FIM) is proposed, providing an upper bound for the post-equalization SINR. These analytically-predicted SINR values for the blind approach are compared to the SINR measured via link simulation. The performance of the two channel estimation methods is analyzed by comparing the CRLB, post-equalization SINR, and BER performance for two significantly different transmission packet sizes. All of the above metrics indicate that blind estimation provides clear performance advantages relative to the pilot-based counterpart. Additionally, the blind approach eliminates the overhead associated with the pilot-based method, where a portion of the system resources is allocated to the pilot sequence. To quantify this, the spectral efficiency of the FD relay system employing blind and pilot-based channel estimation methods are compared, indicating that at high SNR, the blind approach provides around 2-bps/Hz spectral efficiency gain relative to a typical pilot-based method. Finally, the computational complexity of the two channel estimation techniques are evaluated and compared. The blind approach has a clear computational advantage for larger packet sizes.

中文翻译：

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全双工无线中继系统中的盲信道估计


我们研究了两跳全双工中继系统中基于二阶统计的盲信道估计的可行性。为此，对盲信道估计方法和传统的基于导频（基于训练序列）的信道估计方法的性能进行了比较。这是通过推导盲方案和基于导频方案的 Cramer-Rao 下界 (CRLB) 表达式，并将它们相互比较以及与通过仿真测量的均方误差 (MSE) 值进行比较来实现的。还针对盲法和基于导频的方法导出均衡后 SINR 表达式。此外，提出了一种改进的均衡后 SINR 表达式，其中信道估计误差由 Fisher 信息矩阵 (FIM) 的逆矩阵代替，为均衡后 SINR 提供了上限。将盲法的这些分析预测的 SINR 值与通过链路模拟测量的 SINR 进行比较。通过比较两种明显不同的传输数据包大小的 CRLB、均衡后 SINR 和 BER 性能，分析了两种信道估计方法的性能。所有上述指标表明，相对于基于导频的盲估计，盲估计提供了明显的性能优势。另外，盲方法消除了与基于导频的方法相关的开销，其中一部分系统资源被分配给导频序列。为了量化这一点，对采用盲信道估计方法和基于导频的信道估计方法的 FD 中继系统的频谱效率进行了比较，表明在高 SNR 下，盲方法相对于典型的基于导频的信道估计方法提供了大约 2-bps/Hz 的频谱效率增益。方法。 最后，评估并比较了两种信道估计技术的计算复杂度。对于较大的数据包大小，盲法具有明显的计算优势。