Hybrid Coded Caching in Cellular Networks with D2D-Enabled Mobile Users

Content caching has emerged as a promising technique to reduce the backhaul multimedia traffic rising due to the proliferation of mobile devices. To address the bottleneck issue arising as a result of sparse wireless resources, the current literature is mainly focused on designing centralized or decentralized coded caching schemes. In this paper, we present a hybrid coded caching approach in a cellular network considering mobile users, where both downlink transmission from the base-station (BS) and device-to-device (D2D) communications are permitted. The proposed method comprises of two phases in content delivery. In the first phase, coded packets are delivered using decentralized coded caching which provides concurrent transmissions through spatial reuse. The BS broadcasts the remaining files using the centralized coded caching paradigm in the second phase in order to compensate for the diminishing returns in D2D communications as time progresses. We analytically derive and analyze the optimal switching point for which the network performance improves in terms of throughput and response time delay under two random user mobility models. Validated by simulation results, our hybrid strategy significantly reduces the finishing time as compared to existing schemes.