Scheme Design And Performance Research Of UAV-assisted Relay Communication

In recent years,with the mass production of Unmanned Aerial Vehicle(UAV)equipment and the development of wireless communication technology,UAV communication technology has become a research hotspot of wireless communication.Due to its high mobility and rapid large-scale deployment of airborne platforms,UAVs can be used as relay nodes to enhance the spectrum efficiency and accessibility rate of existing networks,and improve the service quality and emergency capability of mobile communication networks.However,the mobility and miniaturization of UAV lead to the rapid change of channel state information and energy limitation,which makes the performance of UAV communication network face great challenges.Aiming at the many problems in UAV-assisted relay communication,this paper combines communication technologies such as energy harvesting(EH)and cognitive radio to effectively improve the spectrum efficiency of UAV-assisted relay communication while reducing the energy consumption of UAV,And improve the stability and reliability of the drone relay auxiliary communication system.The main research contents and innovation points of this paper are as follows:1.Aiming at the problems of limited energy in the UAV-assisted relay communication network,based on simultaneous wireless information and power transfer(SWIPT)technology,a UAV-assisted relay transmission model enhanced by energy harvesting was established,in which the transmission channels from the UAV relay node to the source and destination are subject to Nakagami-m distribution.Considering the system source node transmit power,channel state,time switching(TS)factor and power splitting(PS)factor and other parameters,the performance of the throughput,outage probability,and bit error rate(BER)of the UAV-assisted relay communication network enhanced by the energy harvesting technology when the destination is subject to aggregation interference is derived and analyzed.The effects of different parameters on system throughput,outage probability and bit error rate are simulated and analyzed,which lays a theoretical foundation for performance optimization of UAV-assisted relay communication network.2.Aiming at the problems of lack of spectrum resources and communication security in the UAV relay-assisted communication network,combined with cognitive radio and physical layer secure transmission technology,a cognitive secrecy transmission model for multiple UAVs Decode-and-Forward(DF)relay selection enhanced by energy harvesting technology under Nakagami-m fading channels is established.Based on the goal of maximizing the secrecy capacity of the system,this paper has derived closed expressions for the secrecy outage probability(SOP)and non-zero secrecy capacity probability of multiple UAVs-assisted communication systems under the TS and PS energy harvesting schemes.On this basis,the asymptotic expression of the confidential interrupt probability is derived,and the closed solution of the diversity gain of the system is obtained.The simulation verifies the rationality of the proposed scheme and the correctness of the theoretical analysis.3.Aiming at the problems of low spectrum efficiency and communication security in UAV relay-assisted communication networks,a cognitive secrecy transmission system is proposed that uses the cognitive radio network(CRN)primary user(PU)transmitter interference signal to provide energy for secondary user(SU)source nodes and UAV relay nodes.The closed expression of the optimal secrecy capacity at the destination is derived,and the closed expressions of the non-zero secrecy capacity probability and secrecy outage probability of the UAV-assisted relay communication network are obtained by using methods such as probability density function analysis and integral feature.By analyzing the asymptotic expression of the secrecy outage probability,the secrecy diversity degree and array gain performance of the UAV-assisted relay communication network are obtained.System simulation verifies the effectiveness of the proposed scheme and the correctness of the theoretical analysis.