Near Optimal Joint Switched Beamforming and User Pairing for MISO Communication System
Résumé
In order to meet the energy efficiency requirements of future wireless communication systems, we propose in this paper a joint switched beamforming and user pairing scheme. We designate by switched beamforming the process of choosing between non-orthogonal multiple access (NOMA) and spatial multiplexing as the beamforming scheme for a group of users. In this context, we formulate the power minimization problem subject to the quality of service (QoS) constraints and pairing constraints for a multiple-input single-output (MISO) communication system. In order to solve the nonconvex optimization problem, we propose a two-step solution. Firstly, given a group of users, we provide an efficient method to compute the optimal beamformers using semidefinite relaxation. Then, we propose an algorithm to determine the optimal pairing strategy and the optimal beamforming scheme for each group. Results reveal that the proposed scheme outperforms NOMA and spatial multiplexing, confirming the importance of exploiting the switched beamforming problem and the user pairing problem jointly to minimize the power consumption. Particular attention is thus paid to the assessment of the impact of the number of antennas on the choice of the beamforming scheme.