Towards Practical File Packetizations in Wireless Device-to-Device Caching Networks

We consider wireless device-to-device (D2D) caching networks with single-hop transmissions. Previous work has demonstrated that caching and coded multicasting can significantly increase per user throughput. However, the state-of-the-art coded caching schemes for D2D networks are generally impractical because content files are partitioned into an exponential number of packets with respect to the number of users if both library and memory sizes are fixed. In this paper, we present two novel combinatorial approaches to coded caching design in D2D networks with the goal of reducing the required packetization while keeping the desired throughput gain compared to the conventional uncoded unicasting. The first proposed approach is based on a novel “hypercube” design, where each user caches a “hyperplane” in this hypercube and the intersections of “hyperplanes” lead to coded multicasting codewords. In addition, we also extend this centralized scheme to a decentralized design. The second approach uses the RuzsaSzeméredi graph to define the cache placement and disjoint matchings on this graph represent coded multicasting opportunities. Both approaches yield an exponential reduction of packetizations with respect to the number of users while providing a per-user throughput that is comparable to the state-of-the-art designs in the literature. Furthermore, by using the spatial reuse in D2D networks, besides further reducing the required packetizations, we demonstrate that the per user throughput can be improved significantly for some parameter regimes.