Design And Simulation Of UAV Swarm Access System

With the continuous development of unmanned aerial vehicle(UAV)technology,the mode of multi-uav cluster has been widely concerned.Multiple UAVs connect to the network in a selforganizing way and not only serve as network terminals to complete complex formation flight,but also as communication relays to solve communication problems that cannot be solved by traditional base stations.UAV cluster has the characteristics of high-speed mobility and rapid topology change,which easily causes serious channel access problems and the robustness of network cannot be guaranteed.Therefore,the channel fast access problem of UAV swarm networks has become a research hotspot.The access system of UAV swarm networks is studied in this thesis.Firstly,a multi-priority channel allocation algorithm is proposed to solve the problem of fast channel access.Then,based on OPNET,combined with the characteristics of UAV networking and network environments,the simulation platform for UAV swarm networks is built,and on this basis,the hardware-in-the-loop simulation platform is further constructed.The specific research contents are as follows:1)A multi-priority channel allocation algorithm for UAV swarm networks is proposed.Firstly,according to the channel load within the interference range of UAV nodes,the channel occupancy rate of each channel at the next moment is estimated by autoregressive model.Then different access thresholds are set based on the priorities of the services to be sent.Finally,the maximum competition window of different priority services is adjusted adaptively according to the network load,and the size of the backoff window is dynamically adjusted based on the value of channel busyness rate.Different from other algorithms,this algorithm not only considers the priority of different services,but also comprehensively considers the channel state and congestion of multiple time slots when designing the access threshold and backoff window.Compared with the traditional binary exponential backout algorithm,the proposed algorithm can ensure the high reliability of data transmission with different priorities and reduce network delay under the heavy load of multi-hop networks.2)The virtual simulation platform of UAV swarm network is built based on OPNET,and the hardware-in-the-loop simulation platform combining virtuality and reality is further constructed.a)Establish the network architecture of UAV swarm networks,and complete the design of application layer,transmission layer,network layer,media access control layer and physical layer.At the application layer,the probability density distribution function is used to simulate the probability distribution of sending packets with different priorities.At the transport layer,the port is applied to establish the connection and realizes the end-to-end communications.At the network layer,the route discovery and update process is realized based on Dijkstra algorithm.In the media access control layer,the channel allocation algorithm and the traditional binary backoff algorithm are implemented based on OPNET.In the physical layer,the different kinds of transmission channel are constructed to adapted to different electromagnetic environment and terrain.Further,the network scene,node model and process model for UAV networks are constructed,and the entire simulation platform for UAV swarm networks is finally built.Based on this,the simulation of UAV node dynamic access to the network is realized,by which the performance curves such as dynamic access time and dynamic access success rate can be obtained.b)Further complete the construction of virtuality-reality-integrated emi-physical simulation platform.During the realization of the emi-physical simulation,SITL gateway and link are established to connect the real object to the simulation environment,and the message format conversion process between virtual and real machines is completed to realize the data communication between the real and virtual environments.On this basis,by adding interference sources in different frequency bands on the reality platform,the influence of different electromagnetic environments is simulated,and the simulation of frequency resource identification is conducted on the emi-physical simulation.