Integrating coded caching (CC) techniques into multi-input multi-output (MIMO) setups provides a substantial performance boost in terms of the achievable degrees of freedom (DoF). In this paper, we study cache-aided MIMO setups where a single server with $L$ transmit antennas communicates with a number of users each with $G$ receive antennas. We extend a baseline CC scheme, originally designed for multi-input single-output (MISO) systems, to the considered MIMO setup. However, in a proposed MIMO approach, instead of merely replicating the transmit strategy from the baseline MISO scheme, we adjust the number of users served in each transmission to maximize the achievable DoF. This approach not only makes the extension more flexible in terms of supported network parameters but also results in an improved DoF of $\max_{\beta \le G} \beta \lfloor \frac{L-1}{\beta} \rfloor + \beta (t+1)$, where $t$ is the coded caching gain. In addition, we also propose a high-performance multicast transmission design for the considered MIMO-CC setup by formulating a symmetric rate maximization problem in terms of the transmit covariance matrices for the multicast signals and solving the resulting non-convex problem using successive convex approximation. Finally, we use numerical simulations to verify both improved DoF results and enhanced MIMO multicasting performance.

翻译：将编码缓存（CC）技术与多输入多输出（MIMO）架构相结合，可在可达自由度（DoF）方面实现显著的性能提升。本文研究了一种缓存辅助的MIMO系统，其中配备$L$根发射天线的单个服务器与多个用户进行通信，每个用户配备$G$根接收天线。我们将一种最初为多输入单输出（MISO）系统设计的基准CC方案扩展到所考虑的MIMO场景中。然而，在所提出的MIMO方案中，并非简单地复制基准MISO方案中的传输策略，而是通过调整每次传输中服务的用户数量来最大化可达DoF。该方法不仅使扩展方案在支持的网络参数方面更具灵活性，还产生了改进的DoF：$\max_{\beta \le G} \beta \lfloor \frac{L-1}{\beta} \rfloor + \beta (t+1)$，其中$t$为编码缓存增益。此外，我们还针对所考虑的MIMO-CC系统提出了一种高性能多播传输设计，即通过建立关于多播信号发射协方差矩阵的对称速率最大化问题，并利用逐次凸近似方法求解该非凸问题。最后，通过数值仿真验证了改进的DoF结果和增强的MIMO多播性能。