Impact of channel-dependent variation of path loss exponent on Wireless Information-Theoretic Security

Recent published works have manifested a renewed interest in the impact of the wireless channel itself on the achievable level of secure information exchange between two or more communication nodes, in the presence of an undesired eavesdropper, developing the research field of Wireless Information-Theoretic Security (WITS). For quasi-static Rayleigh fading channels, information-theoretic security has been proven to be achievable even when the eavesdropper's channel has a better average Signal-to-Noise Ratio (SNR) than the main channel, thus bypassing the limits considered in the classic AWGN-channels model. In these works, a typical value has been assigned to the path loss exponent that dominates the distance ratio (faction of distance between the legitimate receiver and the transmitter to the distance between the eavesdropper and the transmitter). Extensive research has proven, however, that the path loss exponent value varies according to the type and the intrinsic characteristics of the wireless channel in question. In our work, we take into account this variation of the path loss exponent and examine its impact on the secrecy capacity and the outage probability for a given normalized secrecy rate. Our results establish a link between the different types of wireless environment and the boundaries of secure communications.