Research On Communication Coverage Of UAV With Imperfect Channel State Information

In recent years,unmanned aerial vehicles(UAVs)have become a research hotspot in the field of wireless communication due to advantages such as low cost,wide coverage,no restrictions on complex terrain,and no blind spots in communication.As an air base station,UAVs have obvious advantages in improving the service quality of traditional cellular systems,reducing the cost of deploying communication facilities,and meeting the needs of rapid communication recovery in disaster areas.At present,the research on communication coverage of UAVs mainly focuses on the case of accurately known channel state information,and does not consider the situation where the channel state information of the transmitter is inaccurate due to estimation errors or quantization.Based on this,this thesis focuses on the inaccuracy of channel state information,and studies how to improve the communication coverage quality of the system by optimizing the 3D coordinates of the UAV base station.The specific research content is as follows:(1)Considering the probabilistic characteristics of direct and non-direct links of UAV air-ground communication links,aiming at the problem of channel estimation errors in actual communication,an air-ground communication mathematical model based on a probability elevation angle of UAV base stations under inaccurate channel information is established.Based on this,the theoretical analysis expression of air-ground communication link outage probability is derived using the link outage probability as a performance evaluation index.The analysis of theory is verified by the simulation results.And further analyze the influence of channel estimation errors on the outage probability of link.(2)For the UAV base station air-ground communication system with inaccurate channel state information,on the premise of ensuring the coverage of ground users in the area,a three-dimensional coordinate optimization problem of multi-UAV base stations with an optimization target of signal transmission outage probability was established.In order to solve this non-convex optimization problem,it is solved by setting it into two optimization sub-problems of horizontal dimension and vertical dimension,and an algorithm for solving three-dimensional coordinates of multiple UAV base stations based on alternating iteration is further proposed.The correctness of the theoretical analysis is verified by the simulation results.And also analyze the influence of channel estimation errors on the height and coverage area of UAV base station.(3)Aiming at the problem of maximizing ground user coverage of UAV base stations under inaccurate channel information,a three-dimensional coordinate optimization model of multiple UAV base stations with ground user coverage as the optimization target and signal transmission outage probability as a constraint was established.A joint iterative algorithm based on Newton's method and sequential convex approximation is proposed.The simulation results verify the correctness of the theoretical derivation,and clarify the effect of the channel estimation error on the height and coverage area of UAV base station under the condition of maximum user coverage.