Outage Probability Based Power Distribution Between Data and Artificial Noise for Physical Layer Security

In this letter, we address physical layer security in MISO communications in the presence of passive eavesdroppers, i.e., the eavesdroppers´ channels are unknown to the transmitter. Spatial beamforming and artificial noise broadcasting are chosen as the strategy for secure transmission. With the aim of guaranteeing a given probability of secrecy, defined by quality of service constraints at the intended receiver and at the eavesdroppers, an optimum power allocation strategy between transmitted information and artificial noise is proposed. Both power constrained and power unconstrained systems are considered. Our proposed outage probability-based approach compares favourably to an existing second-order-statistic-based approach.