On the Performance of Non-Orthogonal Multiple Access in Short-Packet Communications

This letter investigates the performance of non-orthogonal multiple access (NOMA) in short-packet communications. We aim to answer a fundamental question-for given reliability requirements of users: how much physical-layer transmission latency can NOMA reduce when compared with orthogonal multiple access in the finite blocklength regime? We derive closed-form expressions for the block error rates of users in NOMA. Further, we obtain the near-optimal power allocation coefficients and blocklength to ensure certain reliability. Numerical results validate our theoretical analysis and demonstrate the superior performance of NOMA in reducing transmission latency.