An optimal power allocation for D2D communications over multi-user cellular uplink channels

Device-to-Device (D2D) communications has emerged as a promising technology for optimizing spectral efficiency, reducing latency, improving data rate and increasing system capacity in cellular networks. Power allocation in D2D communication to maintain Quality-of-Service (QoS) remains as a challenging task. In this paper, we investigate the power allocation in D2D underlaying cellular networks with multi-user cellular uplink channel reuse. Specifically, this paper aims at minimizing the total transmit power of D2D users and cellular users (CUs) sub- ject to QoS requirement at each user in terms of the required signal-to- interference-plus-noise ratio (SINR) at D2D users and base station (BS) over uplink channel as well as their limited transmit power. We first derive expressions of SINR at the D2D users and BS based on which an optimization framework for power allocation is developed. We then propose an optimal power allocation algorithm for all D2D users and CUs by taking into account the property of non-negative inverse of a Z- matrix. The proposed algorithm is validated through simulation results which show the impacts of noise power, distance between D2D users, the number of D2D pairs and the number of CUs on the power allocation in the D2D underlaying cellular networks