Secrecy Sum-Rates with Regularized Channel Inversion Precoding Under Imperfect CSI at the Transmitter
In this paper, the authors study the performance of regularized channel inversion pre-coding in MISO broadcast channels with confidential messages under imperfect Channel State Information at the Transmitter (CSIT). They obtain an approximation for the achievable secrecy sum-rate which is almost surely exact as the number of transmits antennas and the number of users grow to infinity in a fixed ratio. Simulations prove this analysis accurate even for finite-size systems. For FDD systems, they determine how the CSIT error must scale with the SNR, and they derive the number of feedback bits required to ensure a constant high-SNR rate gap to the case with perfect CSIT.