Placement Delivery Array Design for Combination Networks with Edge Caching
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A major limitation for implementing coded caching techniques into practical systems, are their high subpacketization levels. For the simple network with a single server and multiple users with cache memories, Yan et al. proposed an alternative scheme that requires slightly larger link rates but significantly reduces the subpacketization level. The main contribution of this paper are three low-subpacketization schemes for combination networks, i.e. for networks with a single server, multiple relays, and multiple users with cache memories that are connected to subsets of relays. One of the schemes achieves the cutset lower bound on the link rate when the cache memories are sufficiently large. Our other two schemes apply only to resolvable combination networks. For these networks, the new schemes perform close to the currently best-known coded caching schemes for a wide range of cache sizes while having significantly reduced subpacketization levels. These schemes are obtained by extending placement delivery arrays (PDA), proposed by Yan et al. to combination networks. Specifically, we define the class of combinational PDAs (C-PDA) to characterize the caching schemes for combination network with a single array.
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