Analysis of Multiantenna UAV-Aided NOMA Relay Systems for Short-Packet Communications between Multiuser Pairs

This article analyzes the performance of a multiantenna unmanned aerial vehicle (UAV)-aided nonorthogonal multiple access (NOMA) relay system to support the finite-blocklength communications between multiple user pairs. To achieve better performance, at the multiantenna UAV, the maximal-ratio combining and maximal-ratio transmission are deployed, and the greedy algorithm is utilized to select the optimal user pair. Based on the approximate Gaussian–Chebyshev quadrature and the incomplete Gamma function, we successfully derive the exact and asymptotic closed-form expression for the average block error rate (BLER), throughput, and goodput of the investigated multiantenna UAV-aided NOMA relay system, taking the impacts of the line-of-sight probability, communication environments, and UAV velocity into consideration. Moreover, we also study other metrics, such as reliability, age of information (AoI), and average packet arrival rate. Simulation results verify the accuracy of the analytical framework. Numerical results indicate that the investigated system meets the requirements of ultrareliable and low-latency communications. Notably, the results showed that the multiantenna UAV-aided NOMA relay system has a reliability higher than 99.99% and an AoI of less than 1 s. Moreover, the optimal UAV altitude, blocklength, and number of transmission bits can be found to maximize the throughput and goodput and minimize the BLER and AoI of the system.