On the performance of non-orthogonal multiple access in the finite blocklength regime

Abstract

In this paper, we present a finite-block-length comparison between the orthogonal multiple access (OMA) scheme and the non-orthogonal multiple access (NOMA) for the uplink channel. First, we consider the Gaussian channel, and derive the closed form expressions for the rate and outage probability. Then, we extend our results to the quasi-static Rayleigh fading channel. Our analysis is based on the recent results on the characterization of the maximum coding rate at finite block-length and finite block-error probability. The overall system throughput is evaluated as a function of the number of information bits, channel uses and power. We find what would be the respective values of these different parameters that would enable throughput maximization. Furthermore, we analyze the system performance in terms of reliability and throughput when applying the type-I ARQ protocol with limited number of retransmissions. The throughput and outage probability are evaluated for different blocklengths and number of information bits. Our analysis reveals that there is a trade-off between reliability and throughput in the ARQ. While increasing the number of retransmissions boosts reliability by minimizing the probability of reception error, it results in more delay which decreases the throughput. Nevertheless, the results show that NOMA always outperforms OMA in terms of throughput, reliability and latency regardless of the users priority or the number of retransmissions in both Gaussian and fading channels.Keywords: non-orthogonal multiple access (NOMA), finite blocklength, ultra reliable communication (URC).

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Random-Access NOMA in URLL Energy-Harvesting IoT Networks With Short Packet and Diversity Transmissions

“…In particular, closed-form expressions for the block error rates of a two-users NOMA network have been derived, while demonstrating the superior performance of NOMA over OMA in reducing transmission latency. Closed-form expressions for the rate and outage probability in an UL NOMA scenario with two users have been derived in [27] for the Gaussian and Rayleigh fading channels. Furthermore, the authors investigated the trade-off between reliability and throughput in the ARQ regime, and demonstrated that NOMA is always superior to OMA in terms of throughput, reliability, and latency.…”

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