STAR-RIS-UAV-Aided Coordinated Multipoint Cellular System for Multi-User Networks

Abstract

Different from conventional reconfigurable intelligent surfaces (RIS), simultaneous transmitting and reflecting RIS (STAR-RIS) can reflect and transmit signals to the receiver. In this paper, to serve more ground users and increase deployment flexibility, we investigate an unmanned aerial vehicle (UAV) equipped with STAR-RIS (STAR-RIS-UAV)-aided wireless communications for multi-user networks. Energy splitting (ES) and mode switching (MS) protocols are considered to control the reflection and transmission coefficients of STAR-RIS elements. To maximize the sum rate of the STAR-RIS-UAV-aided coordinated multipoint (CoMP) cellular system for multi-user networks, the corresponding beamforming vectors as well as transmitted and reflected coefficient matrices are optimized. Specifically, instead of adopting the alternating optimization, we design an iteration method to optimize all variables for both the ES and MS protocols at the same time. Simulation results reveal that the STAR-RIS-UAV-aided CoMP system has a much higher sum rate than systems with conventional RIS or without RIS. Furthermore, the proposed structure is more flexible than fixed STAR-RIS and could greatly promote the sum rate.

Deep Learning-Based Link Quality Estimation for RIS-Assisted UAV-Enabled Wireless Communications System

“…The update gate (z) controls the history and newly added channel data with the RIS phase shift, which can be computed according to (12). Meanwhile, the reset gate (r) controls the flow of new input data to the preceding GRU unit and can be computed according to (13). To calculate the current hidden unit, two steps are involved.…”

“…Moreover, the quality of wireless communication between the UAV and the ground users can be severely impacted by various factors, such as signal fading, interference, and path loss. Moreover, in an RIS-assisted UAV communication system, the UAV is constantly moving, and the channel conditions are constantly changing due to different factors [13]. Therefore, accurate and fast LQE is critical to enable efficient beamforming and reflection coefficient adaptation to maintain a reliable communication link [14].…”

“…(1) Numerous studies in the literature assess the quality of links in communication systems that utilize UAVs [11][12][13]. This article accurately estimates link quality in UAV-based communication systems by considering slow fading and fast fading while integrating RIS.…”

Joint Phase Shift Design and Resource Management for a Non-Orthogonal Multiple Access-Enhanced Internet of Vehicle Assisted by an Intelligent Reflecting Surface-Equipped Unmanned Aerial Vehicle

“…Third, compared to the construction of fixed BSs or communication towers, using an IRS-equipped UAV significantly reduces the cost of infrastructure construction and maintenance, making it particularly suitable for remote or economically disadvantaged rural areas. Finally, on rural roads where communication is obstructed, the stable communication service provided by UAVs can effectively support the operation of an ITS, such as automatic vehicle queuing, traffic flow management, and emergency response, improving road utilization efficiency, reducing traffic congestion, and enhancing driving safety [28,29]. To maximize the energy efficiency of IRS-equipped UAVs, a scheme for the joint optimization of resource allocation, phase shift, and trajectory was proposed in [30].…”