User-Pair Selection for QoS-Aware Secrecy Rate Maximization in Untrusted NOMA

TL;DR

This paper investigates how user-pair selection affects secrecy performance in untrusted NOMA systems, proposing optimization strategies to maximize secrecy rates while ensuring QoS for users with weaker channels.

Contribution

It introduces a novel optimization framework for user-pair selection in untrusted NOMA systems, enhancing secrecy rate maximization with practical power allocation and system parameter analysis.

Findings

Optimal power allocation improves secrecy rates.

User-pair selection significantly impacts secrecy performance.

System parameters influence the effectiveness of secrecy enhancement.

Abstract

Non-orthogonal multiple access (NOMA) has been recognized as one of the key enabling technologies for future generation wireless networks. Sharing the same time-frequency resource among users imposes secrecy challenges in NOMA in the presence of untrusted users. This paper characterizes the impact of user-pair selection on the secrecy performance of an untrusted NOMA system. In this regard, an optimization problem is formulated to maximize the secrecy rate of the strong user while satisfying the quality of service (QoS) demands of the user with poorer channel conditions. To solve this problem, we first obtain optimal power allocation in a two-user NOMA system, and then investigate the user-pair selection problem in a more generalized four user NOMA system. Extensive performance evaluations are conducted to validate the accuracy of the proposed results and present valuable insights on the impact of various system parameters on the secrecy performance of the NOMA communication system.