Analysis of Content-Oriented Heterogeneous Networks with D2D and Cognitive Communications

Abstract

Content-oriented operation with D2D communications and spectrum sharing in the form of cognitive communications are expected to be enablers for cost-efficient nextgeneration wireless systems with bandwidth-hungry services. To this end, caching is an important building block of these systems. In this work, we model such a heterogeneous network and model a popularity-aware caching algorithm where we try to keep more popular contents in caches of system units with a higher probability compared to less popular contents. Moreover, for improving the usage of the channel capacity, overlaying for device-to-device (D2D) transmissions (unless these transmission interfere with each other) is enabled. We model our system with an analytical continuous time Markov chain (CTMC). We have a heterogeneous network architecture consisting of a LEO satellite, base station (BS) and a set of devices within the boundary of BS coverage that can get service from the satellite, from the BS or in D2D mode. Our devices operate in primary mode when they get service from the satellite but in secondary mode when they get service from the BS or some device in D2D mode over the terrestrial link. We evaluate our system for energy efficiency (EE) and goodput metrics. We looked how popularity-aware caching, integration of universal source concept and overlaying in D2D mode affect the network performance. Besides, we investigate how resource allocation (RA) and performance metrics are tangled.