Wireless coded caching with shared caches can overcome the near-far bottleneck

Zhao, Hui; Bazco-Nogueras, Antonio; Elia, Petros
ISIT 2021, IEEE International Symposium on Information Theory, 12-20 July 2021, Melbourne, Victoria, Australia (Virtual Conference)

We investigate the use of coded caching in the singlecell downlink scenario where the receiving users are randomly located inside the cell. We first show that, as a result of having users that experience very different path-loss, the real gain of the original coded caching scheme is severely reduced. We then prove that the use of shared caches — which, we stress, is a compulsory feature brought about by the subpacketization constraint in nearly every practical setting — introduces a spatial-averaging effect that allows us to recover most of the subpacketizationconstrained gains that coded caching would have yielded in the error-free identical-link setting. For the ergodic-fading scenario with different pathloss, we derive tight approximations of the average (over the users) rate and of the coded caching gain by means of a basic high-SNR approximation on the point-to-point capacity. These derived expressions prove very accurate even for low SNR. We also provide a result based on the regime of large number of users which is nonetheless also valid for settings with few users. These results are extensively validated using Monte-
Carlo simulations that adhere to 3GPP recommendations on system parameters for urban micro or macro cells.

Systèmes de Communication
Eurecom Ref:
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