Cooperative D2D for Content Delivery in Heterogeneous Networks

Cache-enabled Device-to-Device (D2D) communication provides a flexible solution to alleviate the burden of data traffic in mobile cellular networks. To improve data offloading capabilities, we present a three-tier collaborative framework for content delivery, where the base station (BS), femtocaching auxiliary equipments (FAEs) and user terminals (UTs) work effectively. Moreover, we even go further and put forward many-to-one D2D communication at the user layer to take full advantage of storage redundancy in dense network scenarios. An optimization objective function based on multi-source D2D communication is deduced to achieve unprecedented average data rate. Considering the case where cellular users and D2D links multiplex the same resources in the uplink period, non-outage probability of the cellular communication is defined to guarantee the main communication quality. Numerical simulations show that our system yields network throughput exponentially while transferring traffic load of the base station reasonably.