Path Planning Of Unmanned Aerial Vehicle Relay Communication System With CDMA

Unmanned Aerial Vehicle(UAV)relay communication is an essential technique for wireless relay communications.The UAV relay communication has the advantages in communication range,cost-effectiveness ratio,network coverage and the flexibility in repositioning.All these attractive features make UAV relay communication promising in a wide range of applications.However,there are some difficulties using UAV as a relaying technique,such as the path planning issue.Therefore,it is important to develop key technologies for the UAV communication systems.Aiming at the path planning problem in UAV relay communication system using a Code Division Multiple Access(CDMA)transmission scheme,the following work is done in this dissertation:First,the path planning issue of relaying UAV under frequency flat fading channel is investigated.Both the point-to-point UAV relay communication model and the Direct Sequence Code Division Multiple Access(DS-CDMA)signal model are given.Then,the outage probability of the relay link is studied,and the path planning method founded on the minimization of the outage probability criterion is given.Both the correctness of the outage probability and the validity of the path planning method are checked by computer simulation.The conclusion is as follows: the path planning method is able to guide the UAV to track the motion of the mobile user node,and keep UAV node flying between base station and user node.Second,the UAV path planning in point-to-point relay communication systems under frequency-selective fading channel is investigated.Both the DS-CDMA signal model and maximum ratio combining(MRC)RAKE receiver model are given.Then,both the outage probability and the average symbol error probability of the relay link are investigated,and the path planning method based on the minimization of the outage probability criterion is given.Both the correctness of the theoretic probability formulas and the validity of the path planning method are verified by computer simulation.The conclusion is as follows: the proposed system fully obtains the diversity gain of the frequency-selective fading channel,and the transmission reliability of the relay link is greatly improved.Third,in order to study the path planning problem of the relaying UAV in multiple-access UAV relay communication systems,the UAV relay communications model with multiple fixed users is given,and the RAKE receiver model of the target user is built.Then,both the outage probability and the average symbol error probability of the relay link are derived.Based on the criterion of minimizing the maximum user outage probability,the path planning method of the UAV is given.Both the correctness of the theoretic probability formulas and the validity of the path planning method are verified by computer simulation.The conclusion is as follows: the path planning method can guide the UAV to fly toward the optimal relaying point,and can improve the outage performance of the relay link.