Research On Wireless Communication Transmission Method Assisted With RIS Carried By UAV

With significant breakthroughs in theory and practice in various types of ultra-electromagnetic materials,more and more people are concerned that Reconfigurable Intelligent Surface(RIS),a new material with low cost and low power consumption,can be used to improve the quality of wireless networks.Compared to the RIS deployed on the surface of a building,which can only provide auxiliary communication for two terminals on the same side,the RIS carried by the drone can not only assist two terminals at any position on the ground in full angle reflection communication,but also dynamically adjust their optimal position in complex radio environments through the high mobility of the drone.Currently,most research on unmanned aerial vehicle(UAV)carrying RIS assisted communication is carried out under ideal assumptions,without considering the impact of UAV altitude on channel Lo S link probability in actual situations.In response to the above issues,this paper conducted research on wireless communication transmission methods assisted by RIS carried by unmanned aerial vehicles,with the specific research contents as follows:1)Aiming at the downlink wireless transmission system assisted by RIS for unmanned aerial vehicles,an optimal height design method for efficient UAV based on the optimal compromise of communication performance is proposed.Consider a communication system consisting of a single antenna base station,a single antenna ground user,and a UAV equipped with RIS.In this system,there are large obstacles blocking communication between the base station and ground users,and auxiliary communication is conducted through a cascade channel constructed by RIS.Firstly,using Jensen inequality,the upper bound expression of the system transmission rate is derived for a wireless communication system equipped with RIS for unmanned aerial vehicles.Secondly,with the goal of maximizing the upper bound of transmission rate,the optimal UAV altitude and RIS phase shift matrices are designed respectively.The simulation results show that the derived upper bound of the rate can well approximate the actual system transmission rate,and the designed optimal height of the UAV can significantly improve the system communication performance.2)Aiming at UAV equipped with Simultaneously Transmitting and Reflecting Reconfigurable Intelligence Surface(STAR-RIS)assisted non orthogonal multiple access wireless communication systems,an optimal height design method for efficient UAV based on optimal trade-offs in communication performance is proposed.Consider a communication system consisting of a single antenna base station,a single antenna ground user,a single antenna High Altitude Platform(HAP),and a UAV equipped with STAR-RIS.Due to obstruction factors,the base station can only transmit signals to ground users and HAPs simultaneously through STAR-RIS.Using Jensen inequality,the upper bound expressions of the system ergodicity and rate are derived.On this basis,with the goal of maximizing the traversal and upper bound of the rate,and on the premise of meeting the HAP rate requirements,the optimal UAV altitude and STAR-RIS optimal reflection and transmission phase shift matrices are designed respectively.Simulation results show that the proposed joint optimization algorithm can significantly improve system communication performance.