Robust Secure Beamforming in Cognitive MIMO Wiretap Channels With Bounded Channel Errors

This paper studies a cognitive multiple-input multiple-output (MIMO) network, in which a secondary transmitter aims to send confidential messages to its receiver in the presence of one multi-antenna eavesdropper, while has the interference temperature limit (ITL) for the primary user. Assuming that all the channels are imperfect and the errors are modeled by deterministically bounded model, we consider robust secure beamforming (RSB) design problem and our goal is to maximize the worst-case achievable secrecy rate subject to the total transmit power constraint and the ITL for the primary user. The formulated optimization problem is non-convex while the channel uncertainties make it more difficult to cope with. To address it, an inexact block coordinate descent (IBCD) approach is proposed to obtain the near-optimal solution, where we firstly linearize the two log-det terms of the objective function and then, the semi-infinite constraints with the bounded channel uncertainties are reformulated as linear matrix inequalities (LMIs). Finally, numerical results validate the performance of our proposed RSB algorithm.