【作者】 陆林燕；

【导师】 郑正奇；

【作者基本信息】 华东师范大学 ， 通信与信息系统， 2008， 硕士

【摘要】 信息时代的到来促使了通信技术的迅猛发展,各种无线通信技术更是成为了人们争相研究的热点。各种技术在发展方向的定位上也变得更为理性,不再一味地追求远距离,高速率等性能。因而造就了当前通信技术百花齐放的局面。人们可以根据实际应用的特点,更为灵活的选择相适应的技术。本文所要讨论的就是这些个性十足的短距离无线通信技术中的一个:Zigbee。Zigbee以低功耗,低成本、低速率等为特点。如果以传统的眼光来看,这种技术似乎无优点可言。然而在自动化和智能化越来越被看重的今天,Zigbee的独特之处使其成为了最炙手可热的无线通信技术之一。该技术将被广泛的应用于家庭智能化、工业控制等众多领域。从体系结构上看,自下至上zigbee由物理层、媒质访问控制层、网络层、应用支持层以及应用层构成。本文的工作将集中在网络层上。对网络层的研究工作是十分有意义的。一方面,网络层承担着承上启下的作用。就规范定义的角度:网络层由Zigbee联盟进行规范;其最下两层由IEEE802.15.4小组定义;而其最上两层的规范则由最终用户决定。网络层能否很好的提供两者之间的衔接将直接影响到zigbee技术的使用。就通信技术本身:网络层将是通信子网与信息子网的隔离者,它的优劣直接影响着通信及上层应用的质量。另一方面,在当前Zigbee芯片及模块的生产都已经相对成熟的市场条件下,能否建立起一个好的网络就成了这项技术的新课题,而组网的工作正是由网络层完成的。本文在基于IEEE802.15.4标准的物理层和媒质访问控制层软件的基础上,完成了对Zigbee网络层的开发,最终形成了一个具有分布式管理功能的自组织、自适应网络。本文的具体工作内容可以分为三个方面。第一,网络层软件平台的搭建。在c语言的环境中,汲取了面向对象编程语言的理念,将各功能进行模块化封装,并采用队列的方式对功能模块进行管理。实际的工作包括了功能的模块化、任务队列、时钟队列的建立、维护。本文所采用的任务队列管理方式,不仅使得ZigBee网络体系结构的层次更为明晰;同时屏蔽了层次间信息的流动方向,使得采用简单函数调用时存在软件结构混乱的情况得到了很好的解决。时间队列的使用则减少了同时使用多个物理时钟造成的器件功耗,并且解决了时钟资源不足的问题。第二,网络层功能的实现。包括数据的处理、网络发起、网络发现、允许节点加入网络、节点加入网络、节点直接加入网络、节点离开网络、启用路由、接收同步、信息库维护及器件重启等,共11个方面功能的实现。该部分的工作是为最终的网络互联以及数据的传递提供保障的。第三,网络路由机制的设计与实现。包括网络拓扑结构的选定;网络地址分配机制的设计:网络路由协议的改进。本文网络地址的分配原则摒弃了传统无线网络地址分配的随意性,力求使网络地址可以反映出一定的网络拓扑信息来,以最终实现对AODV协议的改进。带有拓扑信息的网络地址使得在路由建立过程中,路由请求报文得以不以广播的形式,而是一种更有目的性的方式进行传播,从而从系统的级别上降低功耗,延长了网络的存活时间。对网络地址的分布式管理也使得在网络拓扑结构发生改变时,节点可以以更高的效率对网络进行重构,使得网络的鲁棒性得到提高,信息的安全性得到保障。更多还原

【Abstract】 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.更多还原