Performance analysis on spectral-energy efficiency tradeoff in the D2D-Relay Mechanism

The D2D-Relay mechanism, which integrates device-To-device (D2D) communications and relay technology, is promising in system performance improvement. This paper focuses on studying what kind of benefits the D2D-Relay mechanism could bring into a wireless communication system during the uplink transmission. To comprehensively analyze the system performance, we use a metric, which consists of the spectral efficiency (SE) and the energy efficiency (EE), as an indicator. With this criteria in mind, we theoretically describe the influence from users' preferences to the SE and the EE in detail. Noting that user pairing is an important part of this mechanism, we evaluate the performance of the D2D-Relay mechanism with three typical pairing algorithms based on different criteria. The simulation results conform to our derivations and reveal the performance gain brought by applying the D2D-Relay mechanism. In addition, with different configurations of the number of the users and their preferences to the SE and the EE, the most appropriate algorithm is suggested for the practical application.