Outage constrained secrecy rate maximization using cooperative jamming

We consider a Gaussian MISO wiretap channel, where a multi-antenna source communicates with a single-antenna destination in the presence of a single-antenna eavesdropper. The communication is assisted by multi-antenna helpers that act as jammers to the eavesdropper. Each helper independently transmits noise, which lies in the null space of the helper-destination channel, thus creating no interference to the destination. Under source-eavesdropper channel uncertainty, we derive the optimal source covariance matrix that maximizes the secrecy rate subject to probability of outage and power constraints. Further, for the case in which the helper-eavesdropper channels follow a zero-mean Gaussian model with known covariances, we derive the outage probability in a closed form. Simulation results in support of the analysis are provided.