Secure MIMO Communications Under Quantized Channel Feedback in the Presence of Jamming

We consider the problem of secure communications in a MIMO setting in the presence of an adversarial jammer equipped with nj transmit antennas and an eavesdropper equipped with ne receive antennas. A multiantenna transmitter, equipped with nt antennas, desires to secretly communicate a message to a multiantenna receiver equipped with nr antennas. We propose a transmission method based on artificial noise and linear precoding and a two-stage receiver method employing beamforming. Under this strategy, we first characterize the achievable secrecy rates of communication and prove that the achievable secure degrees-of-freedom (SDoF) is given by ds=nr-nj in the perfect channel state information (CSI) case. Second, we consider quantized CSI feedback using Grassmannian quantization of a function of the direct channel matrix and derive sufficient conditions for the quantization bit rate scaling as a function of transmit power for maintaining the achievable SDoF ds with perfect CSI and for having asymptotically zero secrecy rate loss due to quantization. Numerical simulations are also provided to support the theory.