Efficient File Delivery for Coded Prefetching in Shared Cache Networks With Multiple Requests Per User

摘要

We consider a centralized caching network, where a server serves several groups of users, each having a common shared homogeneous fixed-size cache and requesting arbitrary multiple files. An existing coded prefetching scheme is employed where each file is broken into multiple fragments and each cache stores multiple coded packets, each formed by XORing fragments from different files. For such a system, we propose an efficient file delivery scheme by the server to meet the arbitrary multi-requests of all user-groups. Specifically, the stored coded packets of each cache are classified into four types based on the composition of the file fragments encoded. A delivery strategy is developed, which separately delivers a part of each packet type first, and then combinatorially delivers the remaining different packet types in the last stage. The rate, as well as the worst rate of the proposed delivery scheme, are analyzed. We show that our caching model and delivery scheme can incorporate some existing coded caching schemes as special cases. Moreover, for the special case of uniform requests and uncoded prefetching, we make a comparison with existing results, and show that our approach can achieve a lower delivery rate. We also provide numerical results on the delivery rate for the proposed scheme.