Joint Communication And Control Based Beam Alignment And Tracking For Terahertz Communications

Terahertz communications,as one of the key technologies with the most promising to provide services for 6G,can provide wireless transmission rates of more than 10 Gbit/s and even 100 Gbit/s,and can meet the requirements of high-speed wireless transmission.On the other hand,terahertz has rich spectrum resources;Through the replacement of time resources and frequency resources,terahertz communications can significantly reduce the system delay and provide low latency communication(URLLC)services for real-time control tasks.However,the terahertz communications link is easily blocked,and its direct transmission link may even be blocked by a tiny shadow,so it is difficult to achieve seamless wide area coverage.Using unmanned aerial vehicles(UAV)and reconfigurable intelligent surface(RIS)for assistance communication is one of the important technologies to solve the above problem.UAV-RIS assisted terahertz communications not only provides a solution to the problem of insufficient terahertz occlusion and coverage,but also puts forward higher requirements for the speed,accuracy and complexity of terahertz beam alignment and tracking algorithm in UAV mobile scene.The above requirements pose a major challenge to UAV-RIS assisted terahertz communications.Focusing on the above challenges,this thesis studies the difficulty of terahertz beam alignment and tracking in high-speed mobile scene,and proposes a terahertz beam alignment and tracking method based on deep fusion of communication control,which can ensure the transmission rate requirements and UAV control performance at the same time.Firstly,this thesis establishes the communication and control model in the UAV assisted terahertz communication scenario,then the interaction between communication and control in the model is analyzed in detail:from the perspective of communication,the influence of beam misalignment on motion control is analyzed;from the perspective of control,the influence of sensor sampling value on beam alignment is analyzed.Next,the UAV event trigger control algorithm based on transmission rate is designed.Simulation results show that the terahertz beam alignment and tracking scheme based on communication control fusion in this thesis can ensure excellent communication performance and control stability,and effectively reduce the time resource overhead and transmission power loss of the system.Further,consider the scene of UAV-RIS assisted terahertz communications,on the premise of ensuring the data rate requirements of each user in the cell and the UAV control performance requirements,aiming at maximizing the terahertz transmission sum rate of cell users,a system scheduling method integrating communication and control is designed in this thesis.In order to solve the sum rate maximization problem,The following twostep solution method is designed:(1)a motion control activation scheme is designed to ensure the successful transmission of each user;(2)the optimal phase shift matrix of the RIS is obtained by Riemann conjugate gradient method.Simulation results show that this scheme can effectively improve the sum rate of the cell on the basis of ensuring excellent control performance.The results of this thesis can significantly reduce the time resource overhead and transmission power loss of the system with very low complexity algorithm under the condition of ensuring excellent communication performance and control stability.