Zigbee无线传感器网络英文文献与翻译.doc

1、Zigbee Wireless Sensor Network in Environmental Monitoring ApplicationsI.ZIGBEE TECHNOLOGY Zigbee is a wireless standard based on IEEE802.15.4 that was developed to address the unique needs of most wireless sensing and control applications. Technology is low cost, low power, a low data rate, highly

2、reliable, highly secure wireless networking protocol targeted towards automation and remote control applications. Its depicts two key performance characteristics wireless radio range and data transmission rate of the wireless spectrum. Comparing to other wireless networking protocols such as Bluetoo

3、th, Wi-Fi, UWB and so on, shows excellent transmission ability in lower transmission rate and highly capacity of network.A. Zigbee Framework Framework is made up of a set of blocks called layers. Each layer performs a specific set of services for the layer above. As shown in Fig.1. The IEEE 802.15.4

4、 standard defines the two lower layers: the physical (PHY) layer and the medium access control (MAC) layer. The Alliance builds on this foundation by providing the network and security layer and the framework for the application layer.Fig.1 Framework The IEEE 802.15.4 has two PHY layers that operate

5、 in two separate frequency ranges: 868/915 MHz and 2.4GHz. Moreover, MAC sub-layer controls access to the radio channel using a CSMA-CA mechanism. Its responsibilities may also include transmitting beacon frames, synchronization, and providing a reliable transmission mechanism.B. Zigbees Topology Th

6、e network layer supports star, tree, and mesh topologies, as shown in Fig.2. In a star topology, the network is controlled by one single device called coordinator. The coordinator is responsible for initiating and maintaining the devices on the network. All other devices, known as end devices, direc

7、tly communicate with the coordinator. In mesh and tree topologies, the coordinator is responsible for starting the network and for choosing certain key network parameters, but the network may be extended through the use of routers. In tree networks, routers move data and control messages through the

8、 network using a hierarchical routing strategy. Mesh networks allow full peer-to-peer communication.Fig.2 Mesh topologies Fig.3 is a network model, it shows that supports both single-hop star topology constructed with one coordinator in the center and the end devices, and mesh topology. In the netwo

9、rk, the intelligent nodes are composed by Full Function Device (FFD) and Reduced Function Device (RFD). Only the FFN defines the full functionality and can become a network coordinator. Coordinator manages the network, it is to say that coordinator can start a network and allow other devices to join

10、 or leave it. Moreover, it can provide binding and address-table services, and save messages until they can be delivered.Fig.3 Zigbee network modelII.THE GREENHOUSE ENVIRONMENTAL MONITORINGSYSTEM DESIGN Traditional agriculture only use machinery and equipment which isolating and no communicating abi

11、lity. And farmers have to monitor crops growth by themselves. Even if some people use electrical devices, but most of them were restricted to simple communication between control computer and end devices like sensors instead of wire connection, which couldnt be strictly defined as wireless sensor ne

12、twork. Therefore, by through using sensor networks and, agriculture could become more automation, more networking and smarter. In this project, we should deploy five kinds of sensors in the greenhouse basement. By through these deployed sensors, the parameters such as temperature in the greenhouse,

13、soil temperature, dew point, humidity and light intensity can be detected real time. It is key to collect different parameters from all kinds of sensors. And in the greenhouse, monitoring the vegetables growing conditions is the top issue. Therefore, longer battery life and lower data rate and less

14、complexity are very important. From the introduction about above, we know that meet the requirements for reliability, security, low costs and low power.A. System Overview The overview of Greenhouse environmental monitoring system, which is made up by one sink node (coordinator), many sensor nodes, w

15、orkstation and database. Mote node and sensor node together composed of each collecting node. When sensors collect parameters real time, such as temperature in the greenhouse, soil temperature, dew point, humidity and light intensity, these data will be offered to A/D converter, then by through quan

16、tizing and encoding become the digital signal that is able to transmit by wireless sensor communicating node. Each wireless sensor communicating node has ability of transmitting, receiving function. In this WSN, sensor nodes deployed in the greenhouse, which can collect real time data and transmit d

17、ata to sink node (Coordinator) by the way of multi-hop. Sink node complete the task of data analysis and data storage. Meanwhile, sink node is connected with GPRS/CDMA can provide remote control and data download service. In the monitoring and controlling room, by running greenhouse management softw

18、are, the sink node can periodically receives the data from the wireless sensor nodes and displays them on monitors.B. Node Hardware Design Sensor nodes are the basic units of WSN. The hardware platform is made up sensor nodes closely related to the specific application requirements. Therefore, the m

19、ost important work is the nodes design which can perfect implement the function of detecting and transmission as a WSN node, and perform its technology characteristics. Fig.4 shows the universal structure of the WSN nodes. Power module provides the necessary energy for the sensor nodes. Data collect

20、ion module is used to receive and convert signals of sensors. Data processing and control modules functions are node device control, task scheduling, and energy computing and so on. Communication module is used to send data between nodes and frequency chosen and so on.Fig.4 Universal structure of th

21、e wsn nodes In the data transfer unit, the module is embedded to match the MAC layer and the NET layer of the protocol. We choose CC2430 as the protocol chips, which integrated the CPU, RF transceiver, net protocol and the RAM together. CC2430 uses an 8 bit MCU (8051), and has 128KB programmable fla

22、sh memory and 8KB RAM. It also includes A/D converter, some Timers, AES128 Coprocessor, Watchdog Timer, 32K crystal Sleep mode Timer, Power on Reset, Brown out Detection and 21 I/Os. Based on the chips, many modules for the protocol are provided. And the transfer unit could be easily designed based

23、on the modules. As an example of a sensor end device integrated temperature, humidity and light, the design is shown in Fig. 5. Fig.5 The hardware design of a sensor node The SHT11 is a single chip relative humidity and temperature multi sensor module comprising a calibrated digital output. It can t

24、est the soil temperature and humidity. The DS18B20 is a digital temperature sensor, which has 3 pins and data pin can link MSP430 directly. It can detect temperature in greenhouse. The TCS320 is a digital light sensor. SHT11, DS18B20 and TCS320 are both digital sensors with small size and low power

25、consumption. Other sensor nodes can be obtained by changing the sensors. The sensor nodes are powered from onboard batteries and the coordinator also allows to be powered from an external power supply determined by a jumper.C. Node Software Design The application system consists of a coordinator and

26、 several end devices. The general structure of the code in each is the same, with an initialization followed by a main loop. The software flow of coordinator, upon the coordinator being started, the first action of the application is the initialization of the hardware, liquid crystal, stack and appl

27、ication variables and opening the interrupt. Then a network will be formatted. If this net has been formatted successfully, some network information, such as physical address, net ID, channel number will be shown on the LCD. Then program will step into application layer and monitor signal. If there

28、is end device or router want to join in this net, LCD will shown this information, and show the physical address of applying node, and the coordinator will allocate a net address to this node. If the node has been joined in this network, the data transmitted by this node will be received by coordina

29、tor and shown in the LCD. The software flow of a sensor node, as each sensor node is switched on, it scans all channels and, after seeing any beacons, checks that the coordinator is the one that it is looking for. It then performs a synchronization and association. Once association is complete, the

30、sensor node enters a regular loop of reading its sensors and putting out a frame containing the sensor data. If sending successfully, end device will step into idle state; by contrast, it will collect data once again and send to coordinator until sending successfully.D. Greenhouse Monitoring Softwar

31、e DesignWe use VB language to build an interface for the test and this greenhouse sensor network software can be installed and launched on any Windows-based operating system. It has 4 dialog box selections: setting controlling conditions, setting Timer, setting relevant parameters and showing curren

32、t status. By setting some parameters, it can perform the functions of communicating with port, data collection and data viewing。Zigbee无线传感器网络在环境检测中的应用1. Zigbee技术Zigbee是一种基于IEEEE802.15.4的无线标准上被开发用来满足大多数无线传感器和控制应用的独特需求。Zigbee技术是低成本，低功耗，低数据速率，高可靠性，高度安全的无线网络协议实现自动化和远程控制应用的目标。它描述了两个关键的性能特点无线射频范围和无线频谱的数据传输速率。相较于其他如蓝牙，Wi-Fi技术，超宽带等无线网络协议，Zigbee虽然传输速率慢但传输容量大的特点向我们展示了他出色的传输能力。A. 技术框架Zigbee的框架是有一组层组成的。上诉层中每一层都要执行一组特定的服务任务。如图所示。在IEEE802.15.4标准定义了两个较低层：物理层（PHY）和媒体接入控制（MAC）层。Zigbee联盟建立在网络层和安全层及应用层框架提供的基础上。 图1 技术框架 在IEEE802.15.4有两个phy层，它们在两个不同的频率范围操作:868/915兆赫和2.4GHz。此外，MAC子层控制访问无线