Performance of antenna selection schemes for massive multiple-input multiple-output systems under Non-orthogonal multiple access cooperative communication

Non-orthogonal multiple access (NOMA) has emerged as a promising technology for 5G systems. The most important characteristic of NOMA is that other users' messages is available to the users with better channel conditions. In this work, a modified antenna selection scheme called Double threshold generalized selection combining (DT-GSC) to save power in receivers used for massive multiple-input multiple-output (MIMO) applications are proposed. The diversity combiner selects the paths above two threshold values set at the combiner, the input and the combiner's output. These threshold values are selected based on the practical communication scenario. The average number of combined branches and estimated path are shown mathematically. The bit error performance of DT-GSC and maximal ratio combiner (MRC) are plotted. Through numerical examples it is evident that the new combining technique performs better compared to the existing ones. This combining technique is beneficial in the massive MIMO base station and user equipment with multiple antennas or cooperative communication set up with users employing the MRC scheme. Simulation results are presented to demonstrate the performance of the proposed technique.