Can IRS Alone Guarantee Secure Wireless Communication Without Eve's CSI?

This article discusses the secrecy rate performance of intelligent reflecting surface (IRS) aided multiple-input-single-output (MISO) downlink communication with one legitimate user (Bob) and one illegitimate user (Eve). It is assumed that channel state information (CSI) of Eve is not available for secrecy rate maximization. Hence, joint optimization of phase shift in IRS and transmit beamforming in a base station is performed using the Bob information only, which is basically a rate maximization problem, using block coordinate descent (BCD). Following this, the secrecy rate is computed. The main aim of the study is to find out if the IRS can guarantee secure communication without Eve's CSI or any other jamming strategy being incorporated into the system. We have presented the result through simulation and compared the performance with secrecy rate maximization when Eve's CSI is available. Additionally, we have varied the position of Eve while fixing the position of Bob to show the effect of Eve's position on secrecy.