Performance Impact of Imperfect CSI on Spatial Hiding Anti-jam Communications

This paper explores the effect of imperfect channel state information (CSI) on spatial hiding anti-jam (AJ) communications technique. Recently a fundamental technique of hiding a signal is proposed that provides a precoding technique that allows a pair of two-antenna transceivers to communicate while being jammed intentionally by a malicious single-antenna node. The precoder uses a small amount of CSI to shape the signal to appear orthogonal to the jammer at the intended receiver. However, performance of the scheme depends on the quality of two estimated parameters -- transceiver and jamming CSI. In practice, CSI estimation is always subject to error due to the presence of noise, statistical characteristics of wireless channel, and limitations of hardware. By modeling the CSI estimation error as independent complex Gaussian random variables, analytical model for post-processing residual interference is derived in closed-form for both transceiver and jamming CSI estimation error. In addition, a lower bound for jammers interference as a function of jamming CSI estimation error is derived. Through simulation we demonstrate the effect of imperfect CSI on spatial hiding anti-jam and validate the analytical model as well.