The operational secrecy capacity of cognitive radio MIMO channel

Secure communications over cognitive radio (CR) MIMO channels is studied. The secrecy capacity, defined operationally as the maximum achievable secrecy rate subject to reliability and secrecy constraints, of CR MIMO wiretap channel is established under power and interference constraints, including a number of closed-form expressions, bounds and related properties. The secrecy capacity of this channel can be expressed as a minimax game between the transmitter (who selects the input covariance) and nature (who selects the noise covariance). Neither player can deviate from an optimal strategy without incurring a penalty.