Abstract

Ensuring high reliability is one of the major goals of 5G systems. This work investigates the problem of cooperative relaying and the optimal number of devices to be directly connected to the base station, in order to meet best uplink performance in terms of throughput and reliability. We first propose a D2D-relaying system where devices cooperate forming groups of cellular devices serving as relays to other groups of D2D transmitters. Second we adopt a Markov chain framework, where the states are defined as the numbers of D2D-relays present in the network. Based on that, we derive the average network throughput and reliability. Next, we show that there exists an optimal device distribution, that maximizes the overall reliability and throughput. This number is strongly related to the switching probabilities of the devices and the network parameters such as the orthogonality factor, the cooperation level of D2D-transmitter, the network density and the cluster’s radius. Simulation results illustrate the optimal switching probabilities and the average number of D2D-relays that maximize the overall throughput and reliability.