# Exploiting Inter-User Interference for Secure Massive Non-Orthogonal Multiple Access

## TL;DR

This paper proposes a novel secure massive access scheme for 5G networks that leverages inter-user interference to enhance security without artificial noise, supported by theoretical analysis and simulations.

## Contribution

It introduces a method to exploit inter-user interference for security in massive NOMA systems, including power optimization and secrecy performance analysis.

## Key findings

- Closed-form ergodic secrecy rate expression derived
- Inter-user interference effectively confuses eavesdroppers
- Power optimization improves security performance

## Abstract

This paper considers the security issue of the fifth-generation (5G) wireless networks with massive connections, where multiple eavesdroppers aim to intercept the confidential messages through active eavesdropping. To realize secure massive access, non-orthogonal channel estimation (NOCE) and non-orthogonal multiple access (NOMA) techniques are combined to enhance the signal quality at legitimate users, while the inter-user interference is harnessed to deliberately confuse the eavesdroppers even without exploiting artificial noise (AN). We first analyze the secrecy performance of the considered secure massive access system and derive a closed-form expression for the ergodic secrecy rate. In particular, we reveal the impact of some key system parameters on the ergodic secrecy rate via asymptotic analysis with respect to a large number of antennas and a high transmit power at the base station (BS). Then, to fully exploit the inter-user interference for security enhancement, we propose to optimize the transmit powers in the stages of channel estimation and multiple access. Finally, extensive simulation results validate the effectiveness of the proposed secure massive access scheme.