This is an extended journal version of the conference paper published in ISIT 2025; submitted to IEEE Transactions on Communications (TCOM). Integrating coded caching (CC) into multiple-input multiple-output (MIMO) communications significantly enhances the achievable degrees of freedom (DoF). This paper investigates a practical cache-aided asymmetric MIMO configuration with cache ratio $γ$, where a server with $L$ transmit antennas communicates with $K$ users. The users are partitioned into $J$ groups, and each user in group $j$ has $G_j$ receive antennas. We propose four content-aware MIMO-CC strategies: \emph{min-$G$} enforces symmetry using the smallest antenna count among users; \emph{Grouping} maximizes intra-subset spatial multiplexing gain at the expense of some global caching gain; \emph{Super-grouping} aggregates users into optimized \emph{min-$G$}-based super-sets with identical effective receive multiplexing gains before applying \emph{Grouping} across them; and \emph{Phantom} redistributes spatial resources assuming ``phantom'' antennas at the users to bridge the performance gains of \emph{min-$G$} and \emph{Grouping}. We develop these asymmetric strategies under three reference symmetric CC placement-delivery policies with guaranteed linear decodability: a DoF-optimal policy achieving the optimal single-shot DoF, and two closed-form policies, namely combinatorial and linear cyclic low-complexity constructions, with the cyclic policy attaining DoF performance close to the others in many operating regimes. Analytical and numerical results demonstrate significant DoF improvements across various system configurations, and that policy-strategy combinations offer flexible trade-offs between DoF and subpacketization complexity.

翻译：本文为发表于ISIT 2025的会议论文的扩展期刊版本；投稿至IEEE Transactions on Communications (TCOM)。将编码缓存(CC)集成到多输入多输出(MIMO)通信中可显著提升可达自由度(DoF)。本文研究了一种实用的缓存辅助非对称MIMO配置，其中配备$L$根发射天线的服务器与$K个用户通信$，缓存比为$γ$。用户被划分为$J$组，第$j$组中的每个用户拥有$G_j$根接收天线。我们提出了四种内容感知MIMO-CC策略：\emph{min-$G$}策略通过用户中最少天线数强制对称性；\emph{Grouping}策略以牺牲部分全局缓存增益为代价最大化子集内空间复用增益；\emph{Super-grouping}策略先聚合用户形成基于\emph{min-$G$}的优化超集（具有相同有效接收复用增益），再对其应用\emph{Grouping}策略；\emph{Phantom}策略假设用户拥有“虚拟”天线来重新分配空间资源，以桥接\emph{min-$G$}和\emph{Grouping}策略的性能增益。我们在三种具有可保证线性可解码性的参考对称CC放置-传输策略下发展这些非对称策略：达到最优单次DoF的DoF最优策略，以及两种闭式构造策略——组合构造和线性循环低复杂度构造。其中循环策略在多数运行场景下可达到与其他策略相近的DoF性能。解析和数值结果表明，所提策略在多种系统配置下均可实现显著的DoF提升，且策略-方案组合能在DoF与子包化复杂度之间提供灵活折衷。