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

ABSTRACT 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.