Research On Multi-UAV Relay Transmission Strategy And Optimal Position

With the development of emerging technologies such as Telematics and the commercialization of new generation communication technologies,the number of ground users is growing too fast,and the previous fixed relay communication is difficult to meet the actual communication demand due to its limitations in coverage capacity and deployment cycle.The combination of UAV and relay will play an important role in the highly dynamic scenarios of collaborative communication.In this paper,we focus on the UAV relay communication system and study the highly optimized problem of UAV relay for single-relay collaborative communication system and the problem of relay selection strategy for multi-relay communication system with the probability of interruption and bit error rate as the reliability index of communication,respectively.Firstly,the practical significance and research status of UAV relay communication are introduced,and the theoretical basics of collaborative communication are briefly introduced,which include wireless channel characteristics,common fading channels,forwarding protocols of relay collaborative communication,duplex mode and reliability indexes of collaborative communication system.Secondly,two highly dynamic single relay communication scenarios BS-UAV-MGU(BUM)and MGU-UAV-MGU(MUM)in half-duplex relay collaborative mode are proposed,where BUM is the signal transmission between ground base station and ground mobile user,and MUM is the exchange of data information between ground mobile user and ground mobile user.Considering that both relay collaborative communication scenarios are in dense urban environments,the system model introduces UAV path loss that is consistent with the actual situation.In the two communication scenarios of BUM and MUM,the expressions of the cumulative distribution function of the link signal-to-noise ratio are derived from Eq.And the approximate expressions of the BER and the exact expressions of the outage probability under BPSK modulation are solved by mathematical methods such as level approximation and integral operation based on the knowledge related to information theory,and the accuracy of the proposed expressions is proved by simulating the communication process through Monte Carlo simulation.The effect of UAV flight altitude on the reliability of the halfduplex single-relay communication system under BUM and MUM scenarios is analyzed based on the simulation results.Finally,for the full-duplex multi-relay communication system,two different highly dynamic communication scenarios BS-Multi-UAVs-MGU(BMUM)and MGU-Multi-UAVs-MGU(MMUM)are proposed in this paper,where the BMUM scenario describes the communication scenario between the ground base station and the ground mobile user,and its channel model uses Rayleigh and The MMUM scenario applies to the information transmission process between the mobile ground user and the mobile ground user,so the communication channel obeys the Double-Rayleigh distribution.The proposed system models for the two highly dynamic communication scenarios BMUM and MMUM both introduce a realistic UAV path loss model.In the BMUM and MMUM scenarios,the probability distribution function and cumulative distribution function expressions of the instantaneous channel parameters of each communication link during the information transmission are derived based on the corresponding channel models and on this basis,the communication reliability performance of the maximum signal-to-noise ratio selection strategy,partial signal-to-noise ratio selection strategy,minimum self-interference selection strategy and hybrid relay selection strategy are investigated respectively,and the reliability performance of the communication is obtained through the level expansion and other Due to the different channel parameters of each relay and the lack of instantaneous channel parameters to determine the selected relay,two approximate expressions for the outage probability are proposed for the minimum self-interference relay selection strategy and the hybrid relay selection strategy.The accuracy of the outage probability expressions for the maximum signal-to-noise ratio and the hybrid relay selection strategy,as well as the outage probability approximation expressions for the minimum self-interference and partial signal-to-noise ratio strategies,are verified by simulating the communication process.