Throughput Analysis of the Cache-Enabled Device-to-Device Communication and Small Base Stations Assisting in Cellular Networks

Caching of content on wireless devices in conjunction with device-to-device (D2D) communications is becoming a promising technique in next generation mobile cellular networks (a.k.a., 5G). In this paper, we study the potential throughput benefits that could be obtained through a distributed caching strategy employing both user equipment units (UEs) and denselydeployed small base stations (SBSs). SBSs are able to store the most popular files and deliver user content accordingly. We assume that UEs use the random cache strategy to cache the content aligning with their own favorite interests. Based on the mathematic tool of stochastic geometry, we derive the success probabilities of the cellular link (from SBS to UE) and the D2D link (from UE to UE), respectively. Furthermore, we analyze the success-delivering probabilities of the D2D link with random caching strategy and the cellular link with deterministic caching strategy. Finally, we present the closed form expression of the throughput for such a network. The developed results are very helpful for network designers to efficiently determine the optimal network parameters at which the optimum system performance can be achieved. As corroborated by extensive numerical results, caching can significantly improve the network throughput, using both UEs and SBSs.