Achieving Covertness in Cooperative Systems With Power Allocation

Abstract

This work addresses the challenge of achieving covert communication in cooperative wireless systems, which consist of a source, a decode-and-forward relay, and a destination. The direct link between the source and the destination is often impaired by deep fading, necessitating the use of a relay to forward signals. The relay also attempts to transmit its covert signal to the destination over the same spectrum, complicating the source’s detection capabilities. To tackle this issue, we propose two power allocation schemes: 1) fixed power allocation (FPA) and 2) dynamic power allocation (DPA). The FPA scheme maintains a constant power allocation for the source’s message, while the DPA scheme adjusts power based on the channel quality from the relay to the destination. Considering noise uncertainty at the source, we derive closed-form expressions for false alarm probability, miss detection probability, and minimum detection error probability, which are crucial for evaluating the source’s detection performance while ensuring Quality of Service for both source and relay messages. Simulation results demonstrate that the DPA scheme outperforms the FPA scheme in terms of covert throughput, especially under conditions of higher transmission rate thresholds and improved channel conditions.