Energy-efficiency of multi-hop device-to-device communications underlaying cellular networks

Device-to-device (D2D) communication underlaying a cellular network is a promising technology in the future wireless networks to improve network capacity and user experience. In current works, D2D communications are considered as two user equipments (UEs) communicating directly without going through the central base station (BS). In fact, D2D communications can be further broadened to multi-hop D2D communications in which a UE may help other UEs communicate with each other, or assist other UEs to communicate with BS. In this paper, we investigate a scenario of multi-hop D2D communications where one UE may help other two UEs to exchange information, by utilizing analog network coding technique. We analyze the energy-efficiency of this multi-hop D2D communication, derive the average energy-efficiency under Rayleigh fading channels, and compare with direct one-hop D2D communication and traditional cellular communication through BSs.