Opportunistic Power Control for Low Probability of Detection Communication

Abstract

Power control strategies are widely used in wireless networks to minimize transmit power and manage interference. On fading channels that vary with time, however, power control can occasionally lead to high transmit powers that make the transmitter easy to detect by an adversary. In this paper, we propose opportunistic power control, a new transmission strategy for covert communication with low probability of detection. Opportunistic power control, similar to truncated power control, can be thought of as conventional power control with an on-off switch that turns off the transmitter when the channel gain falls below a threshold. The combination of the threshold value and the alphabet size are tuned to ensure that a target spectral efficiency is achieved. We show that, for certain spectral efficiencies, increasing the alphabet size leads to improved LPD performance, at the expense of an increase in the end-to-end delay. We present numerical results that quantify the LPD-delay tradeoff.