Full coded caching gains for cache-less users

Lampiris, Eleftherios; Elia, Petros
ITW 2018, IEEE Information Theory Workshop, 25-29 November 2018, Guangzhou

The  work  identifies  the  performance  limits  of the multiple-input single-output broadcast channel where cache- aided users coincide with users  that do not have caches. The main contribution is a new algorithm that employs perfect matchings on  a bipartite graph to offer full multiplexing as well as full coded-caching gains to both cache-aided as well as cache-less users. This performance is shown to be within a factor of at most  3 from the optimal, under the assumption of linear one- shot schemes. An interesting outcome is the following: starting from a single- stream centralized coded caching  setting with normalized cache size γ, then every addition of an extra transmit antenna allows for  the addition of approximately 1/γ extra cache-less users, at no added delay costs. For example,  starting from a single-stream coded caching setting with γ = 1/100, every addition of a trans- mit  antenna, allows for serving approximately an additional 100 more cache-less users, without any increase in the overall delay. Finally the work reveals the role of multiple antennas in removing the penalties typically associated to cache-size unevenness, as it shows that the performance in  the presence of both cache-less and cache-aided users, matches the optimal (under uncoded cache placement) performance of the corresponding symmetric case where the same cumulative cache volume is split evenly across all users.


Systèmes de Communication
Eurecom Ref:
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