Optimal transmission with artificial noise in misome wiretap channels

We investigate the optimal physical-layer secure transmission with artificial noise in the wiretap channel with N antennas at the transmitter, a single antenna at the receiver, and M antennas at the eavesdropper. We analyze the performance and determine the optimal transmission parameters for two distinct schemes: 1) an on-off transmission scheme and 2) an adaptive transmission scheme. For the on-off transmission scheme, where a channel-realization-independent secrecy rate is used for all transmission periods, we derive closed-form expressions for the secure transmission probability, the hybrid outage probability, and the effective secrecy throughput. For the adaptive transmission scheme, where a channel-realization-dependent secrecy rate is used for each transmission period, we derive closed-form expressions for the secure transmission probability, the secrecy outage probability, and the effective secrecy throughput. Using these closed-form expressions, we determine the optimal power allocation between information signals and artificial noise signals for both schemes to maximize the secure transmission probability. We also determine the optimal secrecy rate for both schemes to maximize the effective secrecy throughput. We explicitly examine the impact of N and M on the optimal power allocation and the optimal secrecy rate. Finally, we demonstrate the performance gain of the adaptive transmission scheme over the on-off transmission scheme.