Extending the optimality range of multi-antenna coded caching with shared caches

Parrinello, Emanuele; Elia, Petros; Lampiris, Eleftherios
ISIT 2020, IEEE International Symposium on Information Theory, 21-26 June 2020, Los Angeles, California, USA (Virtual Conference)

This work considers the cache-aided multiple-input single-output broadcast channel (MISO BC) where an L-antenna transmitter serves K receiving users, each assisted by one of  < K caches with normalized capacity. For this setting it was known that in the range of L 2 [K=;K ], one can achieve a Degrees-of-Freedom (DoF) performance of L + K. This very restrictive constraint that L  K excluded sharedcache settings with a large number of antennas from achieving the maximum DoF; for the more realistic regime of L > K, all existing coded caching schemes suffer substantially reduced caching or multiplexing gains. Our work provides a novel coded caching scheme that achieves the exact best known, near optimal, DoF L+K, and does so even if L > K, thus covering an important hole in identifying the optimal performance for the multi-antenna shared-cache problem. Therefore, our work reveals that shared-cache systems with many transmit antennas can also enjoy both full multiplexing gains (L) as well as full caching gains (K) despite the sharing of the caches. A side benefit of this scheme is its applicability in multi-antenna settings with dedicated users caches, where it can offer the advantage of reducing the subpacketization without sacrificing the DoF performance.

Los Angeles
Communication systems
Eurecom Ref:
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