Optimal cooperative range of distributed transmitters for communications secrecy

In this paper, we investigate the optimal cooperative range for communications secrecy in an ultra dense network where the source nodes and eavesdroppers (Eves) are randomly distributed. Assuming that all the source nodes inside of the cooperative range (a distance range centered at the target user) participate in cooperative transmission, analytical approximations of the secrecy outage probability are derived for two typical cooperation modes, and the optimal cooperative range which minimizes the secrecy outage probability is illustrated. It is shown that the optimal cooperative range is affected by both the densities of the source nodes and Eves, as well as the cooperation modes that adopted by the transmitters.