Research On Priority-based MAC Protocol For Directional Antenna Ad Hoc Networks

At the beginning of the 21 st century,communication technology has entered a golden age of development,and users' requirements for network are constantly improving.How to meet the needs of real-time communication has become the main work of researchers.Wireless Ad Hoc network has become one of the main research directions at present because of its self-organization characteristics.Directional antenna technology is becoming more and more mature.Compared with omnidirectional antenna,wide communication range and low energy consumption provide conditions for its introduction into Ad hoc networks.With the continuous development of Ad Hoc networks,network services have gradually become diversified.Users have different requirements for the transmission of different types of services,which requires nodes in the network to distinguish the information to be transmitted to meet the needs of users.It is the main content of Ad Hoc network protocol research to study the MAC protocol of directional Ad Hoc network,optimize the spatial reuse degree of the network,improve the load capacity of the network and the processing capacity for multi-priority services.In this thesis,the advantages and negative effects brought by the application of directional antenna in wireless ad hoc networks and the multi-priority service processing strategy are studied.In this thesis,the neighbor discovery algorithm based on time slot scheduling and directional MAC protocol are optimized,and the key technologies in SPMA protocol are optimized and introduced into directional networks.In this thesis,firstly,the working principle and characteristics of wireless ad hoc networks and directional antennas are analyzed,and the network characteristics of wireless ad hoc networks,the positive and negative effects of the introduction of directional antennas are introduced,and the causes of the problems are analyzed to alleviate the adverse effects of the problems.Secondly,this thesis introduces the common directional neighbor discovery algorithms and the flow of MAC protocol,analyzes the performance and existing problems of the existing algorithms,and analyzes the influencing factors of the directional neighbor discovery process through mathematical methods,and calculates the state selection probability.The influence of the neighbor discovery process.Next,the directional MAC protocol based on slot scheduling is optimized.Aiming at the problem of beam alignment and information collision,the neighbor discovery algorithm is optimized,and the time required for neighbor discovery and neighbor list maintenance is obtained;Optimize the design of directional MAC protocol,introduce the processing strategy for multi-priority services,give full play to the advantages of directional antenna according to its beam characteristics,and alleviate the negative impact;Using OPNET to simulate the algorithm,the proposed MAC protocol can ensure the priority transmission of high-priority services,shorten the information transmission delay and improve the network capacity.Finally,the SPMA protocol is studied,and the key technologies such as channel load statistics,threshold setting and backoff window length setting mechanism in the SPMA protocol are studied,and the access mechanism in the SPMA protocol is modified according to the transmission characteristics of the directional antenna,so that it can adapt to the transmission characteristics of the directional network.This thesis uses OPNET software to compare and analyze the performance of omnidirectional SPMA protocol and directional SPMA protocol,From the simulation results,it can be seen that the directed SPMA protocol can provide higher successful delivery rate and lower transmission delay for high-priority services under heavy network load,and also improve the network's communication support for low-priority services.