【作者】 滕远坤；

【导师】 刘磊；

【作者基本信息】 吉林大学 ， 软件工程， 2008， 硕士

【摘要】 无线传感器网络是现今为止,一项非常重要的技术。无线传感器往往工作在环境比较恶劣、常人无法到达或不能长时间工作的地域。无线传感器的使用,给人们带来了另一种感知世界的方式,人们的生活因此也发生了巨大的变化。无线传感器网络就是要把无线传感器连接到一起,使其发挥正常的功能。目前无线传感器网络中关键的技术有:传感器技术、低功耗芯片技术、无线通信技术、低能耗路由技术、低能耗MAC协议、协同定位技术、时钟同步技术、数据融合技术等等。本文研究的是无线通信技术中的跳频传输。通过设计并实现了一种无线传感器网络的跳频通信技术,使得无线传感器网络在通信上有一定的安全性。由于无线传感器节点自身的能力有限,所以设计的时候充分考虑到这一点,在减少无线传感器选择信道时的计算量上做了很多工作。最终使得无线传感器节点在小载荷的情况下,进行跳频通信。更多还原

【Abstract】 Wireless sensor networks are numerous sensors through wireless communications, interrelated, processing, and transmission of information networks. From the end of the last century, fieldbus technology began to be used in sensor network, it is used to build intelligent sensor networks, and large multifunctional sensors are used there, and use of wireless technology connectivity, wireless sensor networks gradually taking shape. Wireless sensor networks now being used in military, medical, environmental testing, and other aspects. Existing wireless sensor networks were generally consistent with the low-power, scalable, adaptive, and simple feature. At present there are many research in the area. The research can be divided into two parts :node level and network level. In the node level of content, including sensor technologies, low-power chip technology, wireless communications technology, In the network level of content , including low-power routing technology, low-power MAC protocol, and co-location technology, clock synchronization, data fusion technology. Currently wireless sensor networks in the frequency-hopping technology on the relatively small. This paper is a study of the technology.Wireless sensor networks generally consist of two parts: base stations and wireless sensors. Among them, wireless sensors and base station compose a tree-topology WSN with the means of self-organizing networks. Communications to the base station via Ethernet cable, and other means of communication with the remote data center.Through self-organization process, WSN would make many wireless communication nodes and base station to link up a sensor networks. Inline sensors send detection information regularly to show the activity of their own. If a wireless network node in a fault status and it can not continue to communications, other nodes will adjust its own network connection to bypass the disconnected node. Each node will have access accurate network time, each frame of data, and other important information will be stamped the network time, the base station will be launched time synchronization process regularly, to protect the entire network, and to ensure that accurate network time. Usually, we come into contact with the wireless communication system are fixed frequency communications systems, such as: mobile phones, car phones, are designated on the appointed frequency of communication, also known as fixed-frequency communications. If received interference, the communication quality of this communication system will decline, the long time interference or even causes communication interruption.For example: the radio programmes. Generally, one program is send with one channel,different programs occupy different emission frequencies. Sometimes there is a strong source of interference, a channel or multiple channels will be blocked, that audience can not received the signals correctly. Therefore, one program will be sent on several channels, as so as interference can not play a role. However, this approach would waste wireless communications resources. If radio stations and listeners can continue the conversion synchronous communications frequencies, so it can effectively escape frequency interference, and listen to good programming. This is a frequency-hopping systemThe existing frequency-hopping system, dependents on frequency-hopping logo to change communications channel. Therefore, a good frequency-hopping pattern would improve system overall performance at frequency hopping. Hopping pattern algorithm generally has the G function algorithm, Viterbi algorithm, DES algorithm. The realization of frequency-hopping logo needs to add hardware circuit, it can produce timely and accurate frequency hopping, but there need to modify the communication module, and the additional frequency-hopping controller will use greater power for wireless sensor. This is not suitable.So it is necessary to design a new program of frequency hopping, achieving on the sensors, to improve wireless communications security, at the same time, it also can reduce wireless communications often appear in the congestion situation. It can be a good choice to use the inherent function of the hardware as frequency hopping algorithm. Since the CC2420 has AES function, the program is designed and implemented based this function. Time is used as a parameter of AES, and then gets the choice of a communication channel so that it could achieve a disorderly hopping process. Precise time synchronization is the frequency-hopping communications important guarantee. The main objective of traditional time synchronization technology is how to obtain high-precision time synchronization. However sensor network time synchronization is designed to meet the accuracy of certain circumstances to reduce the complexity of the algorithm, thereby reducing power consumption, accuracy and the meet the need for balance between power and efficient compromise. Mainly said, it should be considered: energy efficiency, scalability, accuracy, robustness, the life-cycle, the appropriate scope, cost and size, timely manner.WSN select an approximation algorithm DMTS time synchronization strategy. In consideration of the demand of time synchronization accuracy and the practical limitations of wireless communications, so DMTS algorithm to a certain extent on improvements. Compared to the standard DMTS algorithm, the actually realized algorithm of the time is more than a synchronization algorithm for wireless communications. The CC2420 and TinyOS can not access the timestamp function of the MAC layer, and there can not be completely in accordance with the original algorithm to achieve the DMTS. Based on the characteristics of the existing hardware platform, the realization of the process selects the SFD as a symbol synchronization method.The propagation delay of electromagnetic signals in the air can be ignored, so two sides of the SFD of send and receive can be seen as be triggered at the same time. Therefore, in many programs can be achieved, this program is more suitable for the existing hardware environment. The synchronization process of this program is simple, it can be completed with sending twice one-way information. Secondly, it do not need to scan channel idle then to send, this will not cause the delay time, so this program is a kind of high accuracy time synchronization. Finally the program is not necessary to stamp timestamps on MAC level, this make this method more flexible and less limitation. Use this optimal time synchronization method for the system, it can provide reliable protection time synchronization.WSN is a low-speed network, the uncertainty of electromagnetic environment, brings more impact to the wireless communications. The design of the network construction is very important, based on this, the assessment of the performance of existing networks and the maximum load was very necessary. Through the design of a variety of test programs, the calculation of the maximum load and network traffic, the scale of the network can be estimated and then a more perfect WSN can be designed.更多还原