Reconfigurable multiple-input multiple-output can provide performance gains over traditional MIMO by reshaping the channels, i.e., introducing more channel realizations. In this paper, we focus on the achievable rate maximization pattern design for reconfigurable MIMO systems. Firstly, we introduce the matrix representation of pattern reconfigurable MIMO (PR-MIMO), based on which a pattern design problem is formulated. To further reveal the effect of the radiation pattern on the wireless channel, we consider pattern design for both the single-pattern case where the optimized radiation pattern is the same for all the antenna elements, and the multi-pattern case where different antenna elements can adopt different radiation patterns. For the single-pattern case, we show that the pattern design is equivalent to a redistribution of gains among all scattering paths, and an eigenvalue optimization based solution is obtained. For the multi-pattern case, we propose a sequential optimization framework with manifold optimization and eigenvalue decomposition to obtain near-optimal solutions. Numerical results validate the superiority of PR-MIMO systems over traditional MIMO in terms of achievable rate, and also show the effectiveness of the proposed solutions.

翻译：可重构多输入多输出(MIMO)系统通过重塑信道（即引入更多信道实现）可相比传统MIMO提供性能增益。本文聚焦于可重构MIMO系统的最大化可达速率方向图设计。首先，我们提出了方向图可重构MIMO (PR-MIMO) 的矩阵表示，并据此建立了方向图设计问题。为揭示辐射方向图对无线信道的影响，我们分别考虑单方向图情形（所有天线单元采用相同的优化方向图）与多方向图情形（不同天线单元可采用不同方向图）下的方向图设计。针对单方向图情形，我们证明方向图设计等价于在所有散射路径间重新分配增益，并获得了基于特征值优化的解。针对多方向图情形，我们提出一种结合流形优化与特征值分解的序贯优化框架，以获得近最优解。数值结果验证了PR-MIMO系统在可达速率方面优于传统MIMO，同时证明了所提方法的有效性。