Outage Analysis of Aerial Semi-Grant-Free NOMA Systems

TL;DR

This paper analyzes the outage performance of UAV-enabled downlink NOMA systems with semi-grant-free transmission, deriving outage probabilities and proposing a dynamic power allocation scheme to improve user performance.

Contribution

It introduces the first hybrid successive interference cancellation scheme in UAV-based NOMA and derives analytical outage probability expressions, including a new DPA scheme.

Findings

No-zero diversity order only under strict QoS conditions

DPA scheme relaxes data rate constraints effectively

UAV location and altitude significantly impact outage probability

Abstract

In this paper, we analyze the outage performance of unmanned aerial vehicles (UAVs)-enabled downlink non-orthogonal multiple access (NOMA) communication systems with the semi-grant-free (SGF) transmission scheme. A UAV provides coverage services for a grant-based (GB) user and one user is allowed to utilize the same channel resource opportunistically. The hybrid successive interference cancellation scheme is implemented in the downlink NOMA scenarios for the first time. The analytical expressions for the exact and asymptotic outage probability (OP) of the grant-free (GF) user are derived. The results demonstrate that no-zero diversity order can be achieved only under stringent conditions on users' quality of service requirements. Subsequently, we propose an efficient dynamic power allocation (DPA) scheme to relax such data rate constraints to address this issue. The analytical expressions for the exact and asymptotic OP of the GF user with the DPA scheme are derived. Finally, Monte Carlo simulation results are presented to validate the correctness of the derived analytical expressions and demonstrate the effects of the UAV's location and altitude on the OP of the GF user.