Research On Anti-doppler Technology Based On Intelligent Reflecting Surface

Intelligent reflecting surface(IRS)is one of the most attractive key techniques to realize smart radio environments.With the continuous development of the next generation mobile communication technology,new application scenarios will bring more challenging communication problems,so it is necessary to start a new communication mode,which puts higher requirements on the communication physical layer.Although some current communication technologies can greatly improve the spectrum efficiency of wireless systems,these technologies are often accompanied by high energy consumption and high hardware costs.In order to solve the problems faced by the development of mobile communication networks,further reduce the cost of wireless network and improve energy efficiency,the IRS technology was put forward and accepted by the public.IRS has broken the long-standing limitation of uncontrollable electromagnetic wave propagation environment in traditional cognition.Appropriate use of IRS in the system can realize directional reflection of incident signals and intelligently reconfigure the wireless propagation environment.Moreover,IRS has the advantages of low cost,easy integration and high flexibility,and it is a green and efficient communication technology with great application and development prospects.It is effective to mitigate Doppler effect in the high-mobility environments by deploying IRSs.An IRS-assisted Doppler mitigation method has been proposed for high-mobility communications in the literature;however,the computational complexity of IRS phase optimization is high due to maximum likelihood estimation for partial channel parameters.Based on high mobility communication system,this thesis studies IRS compensated Doppler effect in the system,and IRS reflection phase algorithm,transmission frame structure optimization and related parameter recovery methods are discussed in detail.The main work of this thesis is as follows:(1)In this thesis,the system model and channel model of IRS assisting mobile user equipment are established,and the working principle of IRS is explained in terms of the frame structure.(2)In this thesis,a simplified IRS phase optimization method is proposed,and the phase expression is derived.And two parameter recovery schemes are proposed in phase 2.The new scheme avoids the use of complex estimation methods,prevents the introduction of additional estimation errors,and effectively reduces the computational complexity.Numerical simulation results show that the new scheme can effectively reduce the program running time,while still achieving superior passive beamforming gain and strong robustness when pilot overhead is limited.(3)Combined with the new phase algorithm given in this thesis,a three-stage frame structure with transition phase is proposed.The numerical simulation results show that the new pilot frame structure can further reduce the pilot overhead on the basis of the new algorithm,and obtain a higher maximum achievable rate,while the calculation amount is reduced to a certain extent.