Reconfigurable intelligent surface (RIS) has been viewed as a promising solution in constructing reconfigurable radio environment of the propagation channel and boosting ... View more Metadata

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This paper aims to investigate the benefit of using intelligent reflecting surface (IRS) in multi-user multiple-input single-output (MU-MISO) systems, in the presence of eavesdroppers. We maximize the

In this work, we study a simultaneous transmitting and reflecting reconfigurable intelligent surface (RIS)-assisted multiple-input multiple-output network. For the system under consideration, we maximize the weighted sum rate, mainly based on the energy splitting (ES) scheme. To tackle this optimization problem, a sub-optimal block coordinate descent (BCD) algorithm is proposed to design the precoding matrices and the transmitting and reflecting coefficients (TRCs) in an alternate manner. Specifically, the precoding matrices are solved using the Lagrange dual method, while the TRCs are obtained using the constrained concave-convex procedure (CCCP). The simulation results reveal that: 1) Simultaneous transmitting and reflecting RIS (STAR-RIS) can achieve better performance than conventional reflecting/transmiting-only RIS; 2) In unicast communication, time switching (TS) scheme outperforms the ES and mode selection (MS) schemes, while in broadcast communication, ES scheme outperforms the TS and MS schemes.Index Terms-Reconfigurable intelligent surfaces, simultaneously transmitting and reflecting, block coordinate descent, constrained concave-convex procedure. I. INTRODUCTIONNowadays, the reconfigurable intelligent surface (RIS) has attracted great interest from both industry and academia. Since RIS can be installed on flat surfaces to reflect wireless signals and establish a virtual end-to-end link between the transmitter (Tx) and the receiver (Rx), RIS has emerged as a key technology in future wireless systems [1]. Recently, RIS has sparked significant works in various wireless applications such as the multiple-input multiple-output (MIMO) networks [2], energy harvesting network [3], and unmanned aerial vehicle (UAV) networks [4], among others.However, most existing works consider the reflecting-only RIS, e.g., the RIS can only reflect the incident signal. As such, Tx and Rx need to be located on the same side of the RIS, which restricts the deployment of RIS [5]. To overcome

This paper investigates the robust beamforming design in a secrecy multiple-input single-output (MISO) network aided by the intelligent reflecting surface (IRS) with simultaneous wireless information and power transfer (SWIPT). Specifically, by considering that the energy receivers (ERs) are potential eavesdroppers (Eves) and both imperfect channel state information (CSI) of the direct and cascaded channels can be obtained, we investigate the max-min fairness robust secrecy design. The objective is to maximize the minimum robust information rate among the legitimate information receivers (IRs). To solve the formulated non-convex design problem in bounded and probabilistic CSI error models, we utilize the alternating optimization (AO) and successive convex approximation (SCA) methods to obtain