Cooperative Transmission in Cognitive and Energy Harvesting-Based D2D Networks

A cognitive device-to-device (D2D) network with D2D transmitters (DTs) that harvest radio-frequency (RF) energy from the primary transmitters (PTs) is investigated. A novel D2D transmitter-assisted cooperative (DTAC) protocol is proposed, in which a group of DTs that have no transmission opportunity act as potential relays to improve the communications of the primary network. The primary network outage probability is characterized and used to make comparisons between the direct link and the cooperative link which adopts different combining techniques at the primary receivers. The active probability of the DTs is derived, and the D2D network throughput is maximized by seeking an optimal transmission power for the PTs. Simulation results are provided to validate the theoretical analysis.