Initial Access Mechanism Of OFDMA Ad Hoc Network

With the development of wireless communication and avionics technology,Unmanned Aerial Vehicles(UAVs)are widely used for rescue and emergency in the civilian sector,or surveillance and patrols in the military sector because of their strong autonomy,high flexibility,and easy deployment.Compared with the limited execution efficiency of a single UAV,multiple UAVs have a greater ability to work together and can accomplish complex tasks more efficiently and quickly.In addition,Flying Ad Hoc Network(FANET)is characterised by self-organisation,centrelessness,fast movement and frequent changes in network topology.Therefore,how to build a strong real-time,highly reliable trunking communication network to face the huge network scale is the urgent problem of the FANET nowadays.As a key part of the FANET framework,the MAC layer is responsible for the access of each network node to the channel and uses scientific scheduling to solve the problems of network congestion and competition conflicts.The design of the MAC layer protocols can significantly affect the performance of the Ad Hoc in terms of latency,fairness,throughput and energy consumption.In the FANET,longer distances between nodes will lead to an increased end-to-end latency of CSMA protocols and the problem of hidden terminals,thus making traditional CSMA protocols inapplicable.This paper discusses the advantages and disadvantages of various MAC protocols of Ad Hoc and combines them with FANET characteristics to design a MAC protocol for FANET based on orthogonal frequency division multiple access.Owing to the high number of nodes and the large size of the network,a flat structure would lead to poor scalability,and the increased number of nodes would reduce the throughput of the network.Combining with the characteristics of the network communication model,channel model and node model,this paper designs a complete MAC access flow,including initial network establishment,cluster head node update,service interaction design and message format design,etc.Finally,through simulation experiments of FANET communication in the simulation platform,results show that the protocol has the advantages of short networking time,low packet loss rate and strong resistance to destruction.This paper investigates the random access mechanism in the FANET scenario,which solves the problems caused by the long-distance of nodes in the network and the extended transmission time.By building a model,describing the mechanism,evaluating the performance,and validating it through simulation,this paper designs a grant-free random access mechanism based on secondary cluster head collaboration.This mechanism reduces signalling costs,transmission latency and power consumption of terminals,and it reduces collisions and access latency by enabling the secondary cluster head node to assist the primary cluster head node in receiving and processing random access requests.