Design And Simulation Of Distributed Ad-hoc Network System Based On Statistical Priority

Tactical data link is a data communication system that realizes tactical information switching between combat platforms.With the rapid development of information technology and communication technology,data link provides powerful support for the future information war.As the modern wireless communication network system,distributed ad hoc network does not rely on the ground infrastructure,and has the characteristics of high networking speed,good scalability and strong self-healing ability,which is suitable for data link application.The network uses routing protocol,which can dynamically organize the network and reduce the network planning time.In the military communication-oriented scenario,the message to be sent is divided into several priorities according to the degree of urgency.For example,tactical instructions are usually strict on time,while physical environment information can tolerate higher delay.When the channel load and end-to-end delay are large,the traditional MAC protocol can not guarantee the quality of service,and can not meet the transmission requirements of large data link capacity and short delay of data link.A low latency and high reliability medium access control protocol with multi-level Qo S guarantee mechanism is essential.Tactical targeting network technology uses Statistical Priority-based Multiple Access(SPMA)in MAC layer.Compared with traditional MAC protocol,it always chooses the highest priority packet for transmission,which has better network dynamic effect and stricter delay requirements,and is more suitable for military applications.In this thesis,distributed ad hoc network will be adopted as the network architecture.By selecting appropriate routing protocols,the flow of nodes entering and leaving the network is designed,which reduces the network planning time and realizes dynamic networking.On this basis,an medium access control protocol based on statistical priority is designed.Firstly,the operation mechanism and characteristics of the protocol are described.Then three key algorithms are determined: channel load prediction algorithm,full load threshold setting algorithm and backoff time algorithm.Because there is no central control node in the network that can directly obtain the channel load of the whole network,this thesis predicts the channel load value by broadcasting data packets carrying load statistics in MAC layer.Because the topology of distributed ad hoc network is highly dynamic,the fixed full load threshold can not adapt to the network well,so a dynamic full load threshold setting algorithm is designed based on the statistical results of priority packets;Backoff time plays an important role in load level control.Based on priority,channel load prediction value and the number of priority packets,a backoff time algorithm is designed according to the design idea.The three cooperate to realize the multi-priority mechanism.In this paper,a data link network simulation system based on distributed ad hoc network is established by using OMNe T + + simulation platform,and SPMA protocol is modeled.The network performance indexes such as throughput and delay of different priority services are obtained by statistics,and CSMA/CA protocol with no priority is selected to compare its performance.Simulation results show that in the distributed ad hoc network system based on SPMA protocol,the system throughput remains stable and the high priority quality of service is guaranteed.