Performance Analysis of Short-Packet Non-Orthogonal Multiple Access With Alamouti Space-Time Block Coding

Abstract

This paper presents the analytical performance analysis for short-packet non-orthogonal multiple access (NOMA) systems with the Alamouti space-time block coding (STBC) scheme over Nakagami- $m$ fading channels. In the considered system, the base station (BS) with two antennas transmits short packets to two users with single antenna simultaneously by using Alamouti STBC, assuming that statistical and instantaneous channel state information (CSI) is known at the BS and the two users, respectively. The exact closed-from expressions are derived for the average block error rate (BLER) at each user. Then the simple expressions are derived for the asymptotic average BLER at high signal-to-noise ratios (SNRs). We further derive the optimal power allocation coefficients and the minimum blocklength to satisfy the average BLERs at two users. Finally, Monte Carlo simulations are used to verify the theoretical results and numerical results demonstrate the performance advantage of the STBC-NOMA scheme over the counterpart STBC-OMA one in terms of achieving low-latency transmission.