Block Error Performance of NOMA with HARQ-CC in Finite Blocklength

TL;DR

This paper analyzes the error performance of a two-user NOMA system with HARQ-CC in finite blocklength, deriving formulas for BLER, comparing NOMA to OMA, and optimizing parameters for reliability and low latency.

Contribution

It provides a new analytical framework for NOMA with HARQ-CC in finite blocklength, including closed-form BLER approximations and an algorithm for optimizing blocklength and power.

Findings

NOMA outperforms OMA in user fairness.

NOMA requires lower blocklength than OMA at high SNR.

NOMA achieves lower latency for reliability targets around 10^(-5).

Abstract

This paper investigates the performance of a two-user downlink non-orthogonal multiple access (NOMA) system using hybrid automatic repeat request with chase combining (HARQ-CC) in finite blocklength. First, an analytical framework is developed by deriving closed-form approximations for the individual average block error rate (BLER) of the near and the far user. Based upon that, the performance of NOMA is discussed in comparison to orthogonal multiple access (OMA), which draws the conclusion that NOMA outperforms OMA in terms of user fairness. Further, an algorithm is devised to determine the required blocklength and power allocation coefficients for NOMA that satisfies reliability targets for the users. The required blocklength for NOMA is compared to OMA, which shows NOMA has a lower blocklength requirement in high transmit signal-to-noise ratio (SNR) conditions, leading to lower latency than OMA when reliability requirements in terms of BLER for the two users are in the order of 10^(-5).