Joint Antenna Selection and Power Allocation for Clustered Downlink NOMA Networks With Alamouti Space-Time Block Coding

In this paper, the problem of joint antenna selection and power allocation (J-AS-PA) for Alamouti space-time block coding (STBC)-based clustered downlink nonorthogonal multiple-access (NOMA) networks is considered. Essentially, the aim is to assign a pair of antennas to each user cluster and perform power allocation to maximize the network sum-rate, while satisfying quality-of-service (QoS) requirements for all users. However, the problem is nonconvex and computationally-expensive. In turn, it is split into two subproblems; antenna selection, and power allocation over each (user cluster, antenna pairs) combination, and then solved via a two-stage solution procedure. In Stage 1, antenna selection is solved using the stable marriage matching algorithm, whereas the power allocation problem is reformulated as a concave maximization problem. In Stage 2, a swap matching algorithm is devised to ensure stability and further improve the network sum-rate. Simulation results illustrate that the proposed solution procedure achieves a near-optimal network sum-rate in comparison with the global optimal J-AS-PA scheme, and is superior to the OMA-based network. Not only that, but the Alamouti-based schemes will be shown to outperform the conventional non-Alamouti STBC counterpart schemes, which is due to the spatial-diversity gains. Lastly, light is shed on the effect of imperfect successive interference cancellation (SIC) and channel state information (CSI), where the Alamouti-based schemes demonstrate more robustness against SIC and CSI errors than other benchmark schemes.