Randomised Jammer Activation for Physical Layer Security: A Probabilistic Approach to Thwart Multi-Antenna Eavesdroppers

We study a wireless communication system consisting of a transmitter, a legitimate receiver, multi-antenna eavesdroppers and randomly distributed friendly jammers. A secrecy guard zone surrounds the transmitter, within which eavesdroppers can be detected or denied entry. To counter the multi-antenna eavesdroppers' ability to mitigate jamming, we propose a randomised activation strategy where jammers independently transmit artificial noise with a probability. We derive closed-form expressions for the transmission probability and secrecy outage probability, and develop an optimisation framework to adjust the rates of transmitted codewords and confidential messages. Simulation results validate our analytical derivations and demonstrate that the proposed strategy effectively maximises secrecy throughput while maintaining the secrecy outage probability below a specified threshold.