Optimal power allocation in device-to-device communication with SIMO uplink beamforming

Cellular and device-to-device (D2D) communication may cause significant inter-cell interference (ICI) at a neighboring base station (BS). In this work, we aim to maximize the sum rate of a cellular user (CU) and a D2D pair, with receive beamforming at the BS equipped with multiple antennas, subject to per-node power, maximum ICI, and minimum SINR constraints. We propose an efficient algorithm to maximize the sum rate in two steps. We first consider the D2D admissibility problem to determine whether the D2D pair can share the spectrum with the CU while satisfying all the constraints and SINR requirements. We then obtain the optimal beam vector and the optimal power levels of the CU and D2D transmitters in closed form. The performance of the proposed algorithm is studied numerically. It is shown the proposed optimal solution substantially outperforms a CU-priority heuristic approach that selects the maximum CU power with minimum D2D interference.