Multi-User Covert Communications via Intelligent Spectrum Control

TL;DR

This work tackles covert multi-user downlink in multi-cell networks with eavesdroppers and jammers. It proposes an intelligent spectrum control (ISC) scheme that couples high-accuracy spectrum sensing with AI-driven real-time scheduling to create dynamic time-frequency patterns for multiple users. It derives closed-form expressions for the eavesdropper detection error probability ($P_e$) and the legitimate users' reliable transmission probability ($P_u$), and shows how to optimize transmit power to maximize the covert rate ($CR$) and determine the maximum number of concurrent users ($k^*$) under covertness and reliability constraints. Simulations validate the analysis and show that ISC achieves higher $P_e$, higher $P_u$, and greater multi-user capacity than a benchmark AN-aided OFDM scheme, with tight agreement between analytical and Monte Carlo results.

Abstract

This paper investigates the performance of multi-user covert communications over a fixed bandwidth in a multi-cell scenario with both eavesdroppers and malicious jammers. We propose an intelligent spectrum control (ISC) scheme that combines high-accuracy spectrum sensing with AI-assisted real-time decision-making to generate time-frequency dynamic occupation patterns for multiple legitimate users. The scheme can proactively avoid external interference and intra-system co-channel collisions, thereby improving covertness and reliability. Within this framework, we derive closed-form expressions for the detection error probability (DEP) of the eavesdropper and the reliable transmission probability (RTP) of legitimate users under multi-user joint detection. We then analytically optimize the transmission power that can maximize the covert rate (CR), as well as the maximum number of users that can access the system covertly and concurrently under given covertness and reliability constraints. Simulation results confirm the tight match between the analytical and Monte Carlo curves, and show that the proposed scheme can achieve a higher DEP, a larger RTP, and a greater multi-user capacity than the benchmark scheme.

Figures (5)

• Figure 1: Illustration of the multi-user covert communication scenario.
• Figure 2: Illustration of the proposed ISC scheme.
• Figure 3: Performance comparisons vs. different SNR.
• Figure 4: Performance analyses vs. different user numbers.
• Figure 5: Maximum legitimate user numbers vs. different SNR.