Device-to-device(d2d) communications underlaying MU-MIMO cellular networks

Device-to-device (D2D) communication underlaying cellular networks will become an important technology in the future networks such as International Mobile Telecommunications-Advanced (IMT-Advanced) to improve spectral efficiency. For the multi-user multi-input multi-output (MU-MIMO) architecture with multi-antenna base station, design and optimization of D2D communications underlaying such a network is an interesting research area that has not been fully investigated yet. In this paper, we consider a cellular network with multiple cellular user equipments (UEs) and multiple direct D2D pairs underlaying communications with a central base station equipped with multiple antennas. We generalize a joint optimization problem to maximize the overall rate of the cellular UEs and D2D pairs, with regard to the continuous beamforming vector design for all cellular UEs and the binary D2D pair association status search. In addition, to solve the mixed optimization problem approximately, we investigate three precoder design methods and propose a D2D pair association vector search algorithm. Simulation results show the performance gain under different precoder methods with the D2D association vector search algorithm.