Robust Design for STAR-RIS Secured Internet of Medical Things

This paper investigates the secure and efficient e-health data transmission problem in a simultaneously transmitting and reflecting (STAR) reconfigurable intelligent surface (RIS) assisted Internet of Medical Things (IoMT) network. The STAR-RIS is employed to safeguard the patients' telemedicine against eavesdroppers in the whole space. The joint active and passive beamforming is developed to maximize the secrecy energy efficiency (SEE), taking into account the imperfect channel state information (CSI) of all channels. By approximating the semi-infinite inequality constraints with
$S$
-procedure and general sign-definiteness, the reformulated problem is solved by an alternating optimization framework. Simulation results reveal that: 1) STAR-RIS can achieve more noteworthy SEE gain for IoMT networks than conventional reflecting-only RIS; 2) The equal time splitting mode of STAR-RIS is preferable for low power domain, while the energy splitting mode achieves the best performance when the downlink power is sufficient; 3) The accuracy of CSI estimation and the bit resolution power consumption are crucial to reap the SEE benefits offered by STAR-RIS.