Decoding Orders for Securing Untrusted NOMA

TL;DR

This paper proposes a new decoding order strategy for untrusted NOMA systems to enhance security, analytically identifying feasible orders and introducing a suboptimal policy that significantly improves performance.

Contribution

It introduces a novel decoding order strategy for untrusted NOMA, including analytical and numerical methods to identify secure orders and a suboptimal policy to reduce complexity.

Findings

Suboptimal policy achieves 137% performance gain over benchmarks.

Analytical identification of all possible decoding orders.

Numerical validation of secure decoding order feasibility.

Abstract

This letter focuses on exploring a new decoding order to resolve the secrecy issue among untrusted nonorthogonal multiple access users. In this context, firstly, we identify the total number of possible decoding orders analytically. Then, we propose a decoding order strategy ensuring positive secrecy rate for all users, and obtain the number of feasible secure decoding orders based on this proposed strategy numerically. Thereafter, we present a suboptimal policy to avoid the computational complexity involved in finding the best secure decoding order. Numerical results illustrate that the suboptimal solution provides a performance gain of about 137% over therelevant benchmark.