Study On MAC Protocol Of Aeronautical Ad Hoc Networks Using Directional Antenna

Aeronautical Ad Hoc Network refers to a distributed self-organizing multi-hop network that uses airborne communication equipment to communicate between aircrafts.It is a new type of air communication.Due to the high cost of satellite communication and limited capacity,the coverage of the base station is limited,and aeronautical Ad Hoc network is expected to be an important supplement to the special scenario of the aeronautical mobile communication network.However,aeronautical Ad Hoc network has the characteristics of no center,large network span,long distance between nodes,high dynamic topology and diverse services,which leads to limited channel access and high propagation delay,difficult to quickly establish links and guarantee different types of services' QoS,bringing additional challenges to the design of MAC protocol.Therefore,this paper combined the National Natural Science Foundation of the project “Research on networking and key technologies of transoceanic civil aeronautical mobile broadband communication networks”,focusing on MAC protocol of aeronautical Ad Hoc network.Aiming at the requirements of aeronautical Ad Hoc network fair access,the rapid establishment of links and guaranteeing the QoS of the service,the MAC protocol of aeronautical Ad Hoc networks using directional antenna was proposed,using the characteristics of directional antenna's long transmission distance and high spatial reuse,which can establish a stable and efficient transmission link between aircrafts,increase the single-hop transmission distance of aeronautical Ad Hoc network,improve the network throughput,and meet a variety of services transmission requirements in aeronautical Ad Hoc network.The main research work is as follows:(1)A sub-slot model frame structure with guard interval and a packet structure with control information were designed for the problem of long distance between airplane nodes and handshaking of neighbor nodes with directional antenna in aeronautical Ad Hoc network.Aiming at the problem of neighbor discovery and link establishment in directional aeronautical Ad Hoc network,combined with ADS-B system,a neighbor discovery algorithm based on ADS-B was proposed.According to the number of neighbor nodes,the nodes switch the scanning beam by probability and change the probability of node sending mode using the number of neighbors in the reverse beam,so as to reduce neighbor discovery time and improve link establishment efficiency.Aiming at the problem of aeronautical Ad Hoc network access,combined with the dynamic allocation strategy,a time slot allocation strategy based on node traffic and link load was proposed.Through the mutual transmission of the neighbor information control packet,a time slot was assigned to the link fixedly to guarantee the channel access delay.According to the node services needs and link load situation,reserving additional time slots meets the transmission needs of sudden services and enabling unidirectional transmission mode to improve slot utilization and transmission efficiency,so as to avoid time slot competition,improve channel utilization,and ensure the fair use of the channel.(2)Aiming at the QoS requirement of aviation high priority service,the dynamic frame length optimization strategy of TD-DAMAC based on aeronautical traffic priority and load is proposed.By using the multi-queue method to prioritize the aeronautical service and tracking the load of high-priority service queues,the dynamic expansion and contraction of the frame length is performed with a power of two,which allocates more time slot resources to the services with higher safety factors in aeronautical Ad Hoc network.It not only guarantees the QoS of high priority service,meets the transmission requirements of various aeronautical services,but also improves the channel utilization effectively.(3)In this paper,the NS2 simulation platform of TD-DAMAC was established,and the TD-DAMAC protocol proposed in this paper was implemented.Simulation results show that,compared to SBA-R,TD-DAMAC reduced the neighbor discovery time by 30% to 40%,compared to DMAC,MMAC and omnidirectional STDMA,TD-DAMAC improved network throughput,can provide more than 85% packet delivery rate,can reduce the average transmission delay when the node density is not very large.Therefore,TD-DAMAC can improve the performance of aeronautical Ad Hoc network to a certain extent.