On Secure NOMA-Aided Semi-Grant-Free Systems

TL;DR

This paper analyzes the secrecy performance of NOMA-aided semi-grant-free systems, deriving analytical expressions for secrecy outage probability and evaluating the impact of system parameters through simulations.

Contribution

It provides the first analytical derivation of secrecy outage probability for NOMA-based SGF systems with multiple users and scheduling, including asymptotic analysis.

Findings

Secrecy outage probability depends mainly on outage target rate and secure target rate.

Analytical results closely match Monte Carlo simulations.

System parameters significantly influence secrecy performance.

Abstract

Semi-grant-free (SGF) transmission scheme enables grant-free (GF) users to utilize resource blocks allocated for grant-based (GB) users while maintaining the quality of service of GB users. This work investigates the secrecy performance of non-orthogonal multiple access (NOMA)-aided SGF systems. First, analytical expressions for the exact and asymptotic secrecy outage probability (SOP) of NOMA-aided SGF systems with a single GF user are derived. Then, the SGF systems with multiple GF users and the best-user scheduling scheme is considered. Analytical expressions for the exact and asymptotic SOP are derived by utilizing order statistics theory. Monte Carlo simulation results are provided and compared with two benchmark schemes. The effects of system parameters on the SOP of the considered system are demonstrated and the accuracy of the developed analytical results is verified. The results indicate that both the outage target rate for GB and the secure target rate for GF are the main factors of the secrecy performance of SGF systems.