Energy-Efficiency of Selective Relaying in a MIMO Network-Coded Cooperative System

We evaluate the outage probability and the energy efficiency (EE) of a network composed of multiple sources, multiple relays and a single common destination, all of them provided with multiple antennas. More specifically, we resort to the network-coded cooperative (NCC) technique with multiple relay selection (MRS) and compare the EE of the network when operating under two combining techniques at the receiver, namely selection combining (SC) and maximum ratio combining (MRC). Our analysis, which adopts a realistic energy consumption model that encompasses the circuitry consumption, shows that MRC, which is optimal from the reliability perspective, may be outperformed by SC in terms of EE. Moreover, we also provide some insights about the number of relays that must be selected to maximize the EE. Finally, numerical results are presented and confirm the mathematical analysis.