Secure Transmission in Massive MIMO System With Specular Component-Based Beamforming and Artificial Noise Over Ricean Fading Channel

This letter investigates the secure transmission in a multi-user massive MIMO system over Ricean fading channel in the presence of a multi-antenna eavesdropper. In order to reduce the system complexity and the channel estimation overhead, a low-complexity beamforming (BF) scheme using only the specular component is presented. Moreover, the generation of artificial noise (AN) is employed at the base station (BS) for additional security enhancement. Specifically, a tractable closed-form lower bound for the achievable ergodic secrecy rate is derived. Furthermore, the optimal power allocation factor between the transmit data power and AN signal power with fixed total power limit is obtained based on the asymptotic analysis to maximize the achievable ergodic secrecy rate. The analytical results reveal that the ergodic secrecy rate improves with the increase of Ricean K-factor and converges to a specific constant when increasing the number of antennas at the BS. The performance of the proposed scheme is evaluated through comprehensive simulations.