| Summary: | Device-to-device (D2D) communications, which can increase system throughput, allow two cellular devices to communicate directly with each other. Compared with half-duplex relay, full-duplex relay can significantly improve the spectrum efficiency if the self-interference can be efficiently eliminated. This paper proposes a D2D communication scheme, which assigns the fixed D2D transmitter as full-duplex amplify-and-forward relay to assist cellular uplink transmission. Cellular user close to the fixed D2D transmitter can directly download the video by D2D communications. An optimization problem is formulated to maximize the uplink rate of cellular user while guaranteeing the rate requirement of D2D user. We first obtain the feasible region of the power splitting factor, which characterizes the proportion of fixed D2D transmitter power allocated to cellular uplink and D2D communications. Then, a closed-form expression of the optimal power allocation scheme is derived. Also simulation results are presented to validate the proposed optimal power allocation scheme for uplink rate maximization.
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