Efficient power control for half-duplex relay based D2D networks under sum power constraints

Device-to-device (D2D) communications provide an effective way to improve local services in cellular networks which allow close-by users to communicate directly. Considering cooperative relay (CR) can achieve high spectrum and energy efficiency, this paper proposes a novel CR-based D2D communication scheme, referred to as CR-D2D, which allows a D2D link to underlay a cellular downlink by assigning a D2D transmitter as a half-duplex relay to assist cellular downlink communication. To maximize the achievable rates of D2D users and meanwhile to meet the minimum rate requirements of cellular users, transmission powers allocated to the base station (BS) and to the D2D transmitter are both optimized under the sum power constraint, while existing works usually perform the optimization at the BS and at the D2D transmitter independently. The simulation results show that the proposed CR-D2D scheme outperforms traditional cellular communication scheme in system throughput and in spectrum utilization efficiency.