In this paper, a two-stage channel estimation scheme for two-way MIMO relay systems with a single relay antenna is proposed. The backward channel is estimated by using linear minimum mean square estimator (LMMSE) at the first stage, where the optimal training signal is designed. We then mainly focus on the forward channel estimation by using singular value decomposition (SVD) based maximum likelihood method, and the related training signal is proposed. We note that the forward channel estimator is nonlinear and by analyzing the asymptotic Bayesian Cramer-rao Lower Bound (BCRLB), we seek BCRLB as the criterion for training signal design. Finally, the numerical results show that the proposed training signal can improve the MSE performance.

翻译：在本文中,提出了具有单一中继天线的双向MIMO中继系统双向信道估计计划。后向通道估算方法是在设计最佳培训信号的第一阶段使用线性最低平均平方测深器(LMMSE)进行估算,然后我们主要侧重于前向通道估算,方法是使用基于单值的最大概率分解法(SVD),并提出相关的培训信号。我们注意到前向通道测深器是非线性,通过分析无线性能的Bayesian Cramer-rao Nower Bound(BCRLB),我们寻求BCRLB作为培训信号设计的标准。最后,数字结果表明,拟议的培训信号可以改善MSE的性能。