Secrecy capacity of artificial noise aided Rician/Rayleigh MIMO channels

Recent research on physical security of wireless systems focus on artificial noise aided security. The main metric for analysis of such systems is the secrecy capacity of the system. Most of the AN schemes proposed in recent research are based on an hypothesis that the number of transmit antennas is larger than that of the receiver antennas. Under this assumption the system can utilize all eigen-subchannels, equal to number of receiver antennas, of a MIMO system to send messages, and use remaining null spaces for transmitting AN signals. These AN signals null out at the legitimate receivers and degrade illegitimate receiver's channels. However, this strategy can significantly impair the secrecy capacity of the system if number of transmit antennas is constrained or even smaller than number of receive antennas. Recently, a new strategy has been proposed, where messages are encoded in s (which is a variable) strongest eigen-subchannels based on ordered eigenvalues of Wishart matrices, while AN signals are generated in remaining spaces. In this paper, this strategy has been extended to Rician channels. The transmitter-receiver link is supposed to be effected by Rician fading while the illegitimate link is experiencing Rayleigh fading and consequently the secrecy capacity of such system is computed.