Cooperative jamming for MIMO wiretap channels

This paper addresses secure communications over MIMO wiretap channels with the help of multiple cooperative jammers. The worst-case scenario for Alice, Bob and jammers is considered: Eve has the knowledge of all channel matrices, while neither her channel matrix nor her location is known to the remaining terminals. We propose an artificial noise aided cooperative jamming (AN-CJ) scheme, allowing the total jamming signals to be nulled at Bob. The new scheme is valid for the case where the eavesdropper has more antennas than the transmitter. To evaluate the performance of the AN-CJ scheme, we first derive a closed-form expression for the achievable ergodic secrecy rate with Gaussian input alphabets. Then, we show how Gaussian input alphabets achieve the ergodic secrecy capacity.