Research On Media Access Control Algorithm And Network Management Of Wireless Avionics Network

With the development of wireless transmission technology,data rate and reliability of the wireless network have enormously improved.Therefore,there is a trend to use wireless connections to replace the cables of current networks.Recently,researchers are focusing on using wireless connections in avionics network to solve the problems of traditional avionics network like overheavy cables,difficulty of wiring and error detection,expense of wiring,lack of flexibility and expansibility,etc.Wireless avionics network provides new ways of connection for avionics networks and improves the overall performance of avionics systems.Based on the deployment environment and application requirements,a wireless avionics network architecture and protocol structure is designed,and a Medium Access Control algorithm that can control message delay and a series of network management functions are proposed.Firstly,the deployment environment and requirement of the avionics application is analyzed.Then,with reference to traditional avionics network,a network topology structure and protocol structure are proposed.In wireless avionics network,there is a unique network management node to enhance control of the entire network.Moreover,the wireless network can divide into two layers: the upper layer network of high data rate and the lower layer network of low speed.Therefore,the network suits different avionics applications of different data rate requirements better.The lower layer sub-network can continue to divide into several sub-networks,so that wireless avionics network can control the in-network interruption effectively and support more nodes to access.The designed avionics wireless network protocol includes five layers: Physical Layer,Data Link Layer,Network Layer,Transmition Control Layer and Application Layer.The designed protocol structure separates the functions of network clearly and supports the interconnection of designed wireless network,traditional wired avionics network and Ethernet.In order to improve network performance of message delay,the composition of message end-to-end delay is analyzed firstly.It is found that the fluctuation of message end-to-end delay is mainly caused by the delay fluctuation of message waiting medium access.So that the design of medium access method is the critical point of delay control.Therefore,a contention free medium control method is designed for data channel.This method based on Time Division Multiple Address,and each message can use the wireless channel only if it is scheduled time slot.In addition,the order of the time slots is generated by the message scheduling mechanism of 1553 B,which uses small cycle and big cycle to arrange different messages different loop cycles.The delay of waiting for medium access is restrict by the interval of message schedule.At the meantime,in order to transfer network management command and data time slots dynamic application,an independent control channel is set.Moreover,the medium control method of this control command channel is Round robin.Additionally,to enhance the reliability of network,a subnet control function switching method is proposed.Every node of the subnet can run as the control node of the subnet.Subnet will not break down when some nodes power off or fail,because new control node will be elected when the old one quit.Then the medium access control method and subnet control function switching method are realized in OPNET,and the designed algorithm are verified by simulation.In addition,the network management functions are designed.These functions can be devided into four types: device management functions,message management functions,synchronization functions and the other network management functions.And the implementation details of these functions are designed with reference to feathers of wireless avionics network.Furthermore,a prototype network is built by using computer,embedded hardware and commercial off-the-shelf wireless card.In this prototype network,the designed network topology and management functions are implemented,and the effectiveness of the design is verified.The network performance was simply tested and characteristics of wireless avionics network is demonstrated.