Cooperative Device-to-Device (D2D) communications as an underlay of future mobile networks

Recently, the demand of people on mobile data has been growing constantly and rapidly. 3GPP has proposed an approach to involve Device-to-Device (D2D) communications as an underlay of future mobile networks. Nevertheless, in order to guarantee Quality of Service (QoS), as well as to provide higher data rates to meet the future throughput demands of users, a new enhancement is presented in this Thesis that is known as cooperative D2D communications. The goal of this Thesis is to evaluate the performance of cooperative D2D communications in different scenarios. In addition, we aim to identify the most convenient scenario for cooperative D2D communications, considering a reasonable tradeoff between the cost and the benefit of its implementation in practice. The approach that we consider is based on carrying out a system level simulation, where a cluster of Relaying Nodes (RNs) is used, to assist data transmissions from a main Transmitter (Tx) User Equipment (UE) to a main Receiver (Rx) UE. The relaying cluster can then select the most convenient transmit beamforming weighting factor with the aid of a limited channel feedback scheme. The outage probability for a given target End-to-End (E2E) spectral efficiency is used as performance measure. The analyses that were considered reveal that the use cooperative D2D communications have the potential to obtain a better performance than to use direct D2D communications. In addition, the effect of different parameters of the simulation scenario, like the distance between the main Tx and the main Rx, the total number of nodes in the area, the number of active RNs in the cluster, and the amount of feedback information in the second hop, have also been considered