On Gaussian MIMO compound wiretap channels

We study the two-user one-eavesdropper discrete memoryless compound wiretap channel, where the transmitter sends a common confidential message to both users, which needs to be kept perfectly secret from the eavesdropper. We provide a new achievable secrecy rate which is shown to be potentially better than the best known lower bound for the secrecy capacity of this compound wiretap channel. We next consider the two-user one-eavesdropper Gaussian multiple-input multiple-output (MIMO) compound wiretap channel. We obtain an achievable secrecy rate for the Gaussian MIMO compound wiretap channel by using dirty-paper coding (DPC) in the achievable scheme we provided for the discrete memoryless case. We show that the corresponding achievable secrecy rate achieves at least half of the secrecy capacity of the two-user one-eavesdropper Gaussian MIMO wiretap channel. We also obtain the secrecy capacity of the two-user one-eavesdropper Gaussian MIMO compound wiretap channel when the eavesdropper is degraded with respect to one of the two users.