Coded Caching for MISO Systems with Linear Subpacketization

This paper considers the cache-aided multiple-input single-output (MISO) broadcast channel (BC), where a server with
$L$
transmit antennas and containing
$N$
equal-length files communicates to
$K$
users through a wireless broadcast link, and each user has a cache memory of
$M$
files. Multiple-antenna placement delivery array (MAPDA) is a combinatorial structure to design coded caching schemes with uncoded placement and one-shot linear delivery for this MISO BC problem. In this paper, by constructing a class of MAPDAs under cyclic placement, we obtain a new multi-antenna coded caching scheme with linear subpacketization, which achieves the optimal sum-DoF
$KM/N+L$
when
$M/N\leq L/K$
. Compared to existing schemes which achieve the optimal sum-DoF, the proposed scheme achieves lower sum-DoF with significantly lower subpacketization when
$M/N > L/K$
for some parameters. Compared to existing schemes under cyclic placement, the proposed scheme achieves higher sum-DoF with approximately the same subpacketization when
$M/N > \displaystyle \max\{L/K, 1/2\}$
.