Decoding Orders and Power Allocation for Untrusted NOMA: A Secrecy Perspective

TL;DR

This paper addresses secure decoding and power allocation in untrusted NOMA systems, proposing strategies to enhance physical layer security and maximize secrecy rates in 5G networks.

Contribution

It introduces a secure decoding order strategy and joint optimization of decoding order and power allocation for untrusted NOMA, improving secrecy performance.

Findings

Proposed an efficient decoding order strategy for positive secrecy.

Developed an algorithm to find all feasible secure decoding orders.

Achieved about 27 dB secrecy rate gain with joint optimization.

Abstract

The amalgamation of non-orthogonal multiple access (NOMA) and physical layer security is a significant research interest for providing spectrally-efficient secure fifth-generation networks. Observing the secrecy issue among multiplexed NOMA users, which is stemmed from successive interference cancellation based decoding at receivers, we focus on safeguarding untrusted NOMA. Considering the problem of each user's privacy from each other, the appropriate secure decoding order and power allocation (PA) for users are investigated. Specifically, a decoding order strategy is proposed which is efficient in providing positive secrecy at all NOMA users. An algorithm is also provided through which all the feasible secure decoding orders in accordance with the proposed decoding order strategy can be obtained. Further, in order to maximize the sum secrecy rate of the system, the joint solution of decoding order and PA is obtained numerically. Also, a sub-optimal decoding order solution is proposed. Lastly, numerical results present useful insights on the impact of key system parameters and demonstrate that average secrecy rate performance gain of about 27 dB is obtained by the jointly optimized solution over different relevant schemes.