Lattice code design criterion for MIMO wiretap channels

We consider the MIMO wiretap channel, where a legitimate transmitter (Alice) wishes to communicate a confidential message to the legitimate receiver (Bob) over a MIMO channel, while its messages are being eavesdropped by Eve through another MIMO channel. Supposing that Alice uses the nested lattice code proposed in [8], we characterize the expected value of amount of information leakage to Eve, and from minimizing this expected value, we derive a code design criterion for MIMO lattice wiretap codes. The special cases of block and fast fading channels are also studied. We also illustrate our lattice code design criterion using the Alamouti Code as the simplest MIMO code available in the literature.