Minimizing distortion and enhancing security in Rayleigh fading channels

The trade-off between security, reliability, and distortion in a direct communication link with an eavesdropper is investigated by adjusting both the transmission power and the transmission rate, which affects the distortion size of the distortion-limited coding. This involves encoding data at a predetermined rate with Channel Side Information (CSI) to ensure successful data recovery within a defined distortion threshold. Using higher transmit power and coding rates effectively minimizes average distortion but increases intercept probability, whereas opting for lower transmit power and coding rates reduces interception probability while amplifying signal distortion. Thus, we investigate the distortion-intercept probability trade-off across feasible transmit powers and transmission intervals. For a Rayleigh fading channel, we derived a closed-form expression for the IP and calculated the maximum power when transmitting with a fixed power such that the intercept probability is below a threshold. We also present a water-filling-based power allocation to minimize the average distortion under some intercept probability requirements. With the proposed method, both numerical and Monte Carlo simulation demonstrate that employing a power control strategy reduces the average distortion and intercept probability to 78% and 50%, respectively, showcasing the effectiveness of the approach.