Content Delivery Analysis in Multiple Devices to Single Device Communications

Content caching at mobile user devices (UDs) utilizing device-to-device (D2D) communications is a promising technology to enhance the performance of mobile networks in terms of latency, throughput, and energy consumption. In this paper, a novel method of content delivery using multiple devices to single device (MDSD) communications through D2D links is presented. In this method, the Zipf distribution with an exponent shape parameter is adopted to model the content caching popularity for the analysis of the achievable signal-to-interference-plus-noise ratio. In order to investigate the advantage of the proposed MDSD method, first, a closed-form expression of the outage probability is theoretically derived for a single D2D communication to evaluate the success of content delivery to a reference UD. Second, the expression of the outage probability for MDSD communication is derived, where the outage probability is modeled as a function of content caching popularity, the density of UDs, and the size of cooperative area. The research work is further extended to address the frequency reuse among different UDs in one cell, where a frequency band factor is introduced, and the optimal radius of the cooperative area is introduced and analyzed. The analytical results, validated by the simulation results, show that the outage probability decreases drastically when the popularity of the content increases or the radius of the cooperative area increases. Using the derived closed-form expression of the outage probability, the area spectral efficiency (ASE) of the system is presented. Furthermore, the results show that as the frequency band factor increases, the outage probability decreases, and also the ASE decreases. Finally, it is shown that the MDSD outperforms the single-D2D-based method.