MIMO双向中继网络的预编码设计与功控策略

为加强MIMO双向中继系统的空间复用增益，研究一种低复杂度的发送和接收预编码矩阵.利用子空间对齐方法，将双向MIMO信道分解为多路单入单出（SISO）的子信道形式，使得两个源用户能够使用网络编码获取更好的空间复用增益.同时通过矩阵计算和转化，给出了一种优化的功率分配方案.在确定优化矩阵后，该方案能够为每个子信道独立地进行优化功率分配，并且能够得到各节点间优化功率分配的闭合表达式，从而将算法复杂度从O（n3）降低为O（n）.仿真结果表明，在典型场景下，所提方案在具有更低复杂度的优势下，系统性能接近优化的梯度下降迭代方案，优于传统单纯前向放大转发方式（AF） ，有2.99 bit/（sHz）的性能增益. 

Joint Precoding Design and Power Control in MIMO Two-Way Relay Network

In order to enhance spatial multiplexing gain of multiple input multiple output (MIMO) two-way relay networks, the transceiver precoding matrixes for all nodes with low complexity were investigated. Using subspace alignment scheme, the bi-directional MIMO channel can be decoupled into several single input single output (SISO) sub-channels. It is accessible for source nodes to use network coding to obtain better spatial multiplexing gain. By calculating and transforming the matrices, an optimal power control method for MIMO two-way relay network was presented. This method can independently optimize each sub-channel power allocation with the fixed precoding matrix. Moreover, a closed-form solution for power allocation among relay nodes and users is derived which considerable decreases the complexity from O(n3) to O(n). Simulation results show that the performance of the proposed approach is close to the iterative gradient descent solution and outperform the traditional pure amplify-and-forward (AF) two-way mode 2.99 bit/(sHz) gains with less computational load in typical scenarios.