Establishment Of ZigBee Network Layer And Research On Its Key Mechanism

The coming of the information times inspires the rapid development of the communication technologies, especially the different kinds of wireless technologies. However, the development directions of all these technologies are saner now. Capacities such as long distance and high speed are not the only goals. Thus technologies with different kinds of characters turn out in our times. And people are more convenient to choose the most proper wireless communication technology following their own application.The technology this paper working on is one of these short-range wireless communication technologies, which is full of personalities. It is called Zigbee, which aims at low consumption, low cost, low rate etc. This seems awful with traditional standard. However, nowadays with our continuously calling for automation and intelligence, it is these 'weak points' that make Zigbee one of the hottest wireless technologies. It can be used at all kinds of fields such as home intelligence, industry automation etc.From bottom to head, Physical Layer, Medium Accesses Control, Network Layer, Application Support Layer and Application Layer form the ZigBee architecture. And the work of this paper emphasizes on Network Layer, which is of great importance. In one hand, Network Layer is in the middle and acts as a connection. ZigBee Allegiance works on Network Layers. The two lowest layers are defined by IEEE801.15.4 group, and the two highest are designed by the terminal user. Zigbee allegiance works on Network Layers. So whether Network Layer gives a good connection will directly affect the use of the technology. What's more, take the view of communication itself, Network Layer is the boundary of communication subnet and information subnet. The performance of Network Layer will be the key element of the two subnets. In another hand, the production of Zigbee chips and modules are relatively sophisticated now, thus whether a good network can be established becomes the newest topic of the technology. To establish a network, we need the work of Network Layer.This paper finished the development of Network Layer, which bases on the existing Physical and Medium Access Control layer following IEEE802.15.4 protocol. A self-organization, self-adaptation network with distributed management is formed at last. The working content of the paper can be divided into three parts. Firstly, establish the software environment. The user friendly coding idea is imported into the c coding enviroment. The basic functions are encapsulated into modules uniquely and queues are used to order the modules. The work includes the encapsulation of function modules, the building and maintenance of the task and timer queues. The using of task queues in this paper make the structure of ZigBee net much clearer, as well as hiding the direction of the information flow. Thus the confusion of software caused by calling function is well solved. The using of timer queues reduces the consumption when using several physical timers at the same time, meanwhile it also makes the lack of physical timers no longer a problem. Secondly, the realization of network functions, including dealing with the data, the formation of the network, the discovery of the network, permitting joining, joining the network, joining the network directly, leaving the network, starting router, receiver synchronization, maintaining the information base and resetting a device. This part of work is preparing for the final connection of the net and the transmission of the data. Last but not least, the design and realization of the router mechanism. The topologies are compared and choused; the addressing mechanism is carefully designed; the existing router protocol is improved. Different from the traditional way to assign the net address which is at will, this paper tried to make the net address reflect some information of the topology in order to improve the AODV. During the establishment of the route, net address with topology information helps to avoid broadcasting the route request. Instead, it makes the transmission of the request more purposely which reduces the consumption systemically and extend the life of the whole net. The distribution management of net address also makes the nodes react more quickly when the topology is changed. Thus the robust of the net is improved and the safety of the data is ensured.