Artificial Noise Generated in MIMO Scenario: Optimal Power Design

In wireless communication, the transmitter (Alice) can send artificial noise (AN) to interfere with the eavesdropper (Eve). This letter considers the AN MIMO scenario, i.e., both Alice and the legitimate receiver (Bob) are equipped with multiple antennas. A closed-form expression for the lower bound of secrecy capacity is obtained. It is proved that water-filling is the optimal power allocation scheme. An efficient iterative algorithm is proposed to find the optimal power distribution ratio between information and AN so that maximum secrecy capacity can be achieved. Simulation results show that the proposed algorithm converges fast, and multiple antennas can improve the secrecy capacity to some extent compared to the AN MISO case.