Performance of Alamouti STBC-NOMA Scheme Employing Different Transmit Antenna Selection Strategies

In this paper, the average bit error rates of nonorthogonal multiple access (NOMA)schemes employing Alamouti space-time block coding (STBC) combined with different transmit antenna selection (TAS) strategies are investigated. With this purpose, the selection criteria that have been proposed for multiple-antenna schemes such as the conventional TAS (C- TAS) scheme which relies on determining the antenna with the highest channel gain, TAS-maj scheme which is based on majority voting, and, AIA and A³ schemes which respectively activates the antenna that maximizes the users with the worst and best channel conditions, have been considered. Within this examination, the antenna selection strategies that are proposed for single TAS case (i.e., TAS-maj, AIA and A³) are adapted to the case of determining two transmit antennas which would perform Alamouti codeword transmission. By using the Monte Carlo simulation method, the average bit error rate (BER) performance of each user at the downlink phase is examined for Rayleigh fading channels. After demonstrating the simulation results corresponding to the case of no antenna selection and the introduced TAS strategies, their advantages in terms of the average signal-to-noise ratio enhancements are exhibited.