Energy-Efficient Device-to-Device Privacy Content Transmission in Uplink Relay Networks.

The collaborative transmission of device-to-device (D2D) devices with the wireless networks enables the spectrum-efficient communication, which yet causes the interference of the wireless networks to D2D devices. It is fatal to the transmission of privacy content. To tackle the issue, we establish a collaborative D2D and uplink relay transmission model, in which D2D receiver eliminates the interference of the networks under the assist of the relay. Particularly, the relay and D2D receiver of the model can capture energy from the signals they received to relay the signals and facilitate the future D2D transmission, respectively. In order to guarantee the efficiency of D2D transmission, a novel energy-efficient D2D privacy content transmission protocol is proposed. In the protocol, a D2D transmission rate maximization problem is formulated subjected to several key rate and energy efficiency constraints. By solving the problem, the exact analytic solutions with respect to energy allocation parameters are acquired. Furthermore, the outage probabilities of the relay network and D2D transmission are characterized to verify the performance of the protocol. Finally, numerical results are provided to validate the analytical results of the protocol.