Diagonal Multi-Antenna Coded Caching for Reduced Subpacketization

Large subpacketization requirement is known to be a significant issue in the practical implementation of multi-antenna coded caching schemes. In this paper, we introduce a new class of schemes applicable to any network in which the spatial degrees of freedom alpha is larger than or equal to the coded caching gain. This class of schemes, called diagonal coded caching (DCC), is based on a tabular representation of transmitted codewords and includes consecutive diagonal shifting of such representations over a well-defined placement table. We find the lower-bound for the required subpacketization for any DCC scheme and show that it is achievable using simple, novel algorithms. This not only enables smaller subpacketization compared to state of the art but also makes it possible to control the subpacketization by carefully adjusting the alpha parameter.