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1、Zigbee Wireless Sensor And Its Applications in Environmental Monitoring1.1 Standars Wireless sensor standards have been developed with the key design requirement for low power consumption. The standard defines the functions and protocols necessary for sensor nodes to interface with a variety of netw
2、orks.Someof these standardincludeIEEE802.15.4,ZigBee,WirelessHART,ISA100.11,IETF6LoW-PAN,IEEE802.15.3,Wibree.The follow-ing paragraphs describes these standards in more detail. IEEE802.15.4:IEEE802.15.437 is the proposed stan-dard for low rate wireless personal area networks (LR-WPANs).IEEE802.15.4
3、focuses on low cost of deployment,low complexity, and low power consumption.IEEE802.15.4 is designed for wireless sensor applications that require short range communication to maximize battery life. The standard allows the formation of the star and peer-to-peer topology for communication between net
4、-work devices.Devices in the star topology communicate with a central controller while in the peer-to-peer topol-ogy ad hoc and self-configuring networks can be formed.IEEE802.15.4devices are designed to support the physical and data-link layer protocols.The physical layer supports 868/915 MHz low b
5、ands and 2.4 GHz high bands. The MAC layer controls access to the radio channel using the CSMA-CA mechanism.The MAC layer is also responsible for validating frames, frame delivery, network interface, network synchronization, device association, and secure services.Wireless sensor applications using
6、IEEE802.15.4 include residential, industrial, and environment monitor-ing, control and automation. ZigBee 38,39 defines the higher layer communication protocols built on the IEEE 802.15.4 standards for LR-PANs. ZigBee is a simple, low cost, and low power wireless com- munication technology used in e
7、mbedded applications.ZigBee devices can form mesh networks connecting hun- dreds to thousands of devices together. ZigBee devices use very little power and can operate on a cell battery for many years. There are three types of ZigBee devices:Zig-Bee coordinator,ZigBee router, and ZigBee end device.Z
8、ig-Bee coordinator initiates network formation,stores information, and can bridge networks together. ZigBee routers link groups of devices together and provide mul-ti-hop communication across devices. ZigBee end devic consists of the sensors, actuators, and controllers that col-lects data and commun
9、icates only with the router or the coordinator. The ZigBee standard was publicly available as of June 2005. WirelessHART:The WirelessHART40,41 standard pro-vides a wireless network communication protocol for pro-cess measurement and control applications.The standard is based on IEEE802.15.4 for low
10、power 2.4 GHz operation. WirelessHART is compatible with all existing devices, tools, and systems. WirelessHART is reliable, secure, and energy efficient. It supports mesh networking,channel hopping, and time-synchronized messaging.Network com-munication is secure with encryption,verification,authen
11、-tication,and key management.Power management options enable the wireless devices to be more energy effi-cient.WirelessHART is designed to support mesh, star, and combined network topologies. A WirelessHART network consists of wireless field devices,gateways, process auto- mation controller, host ap
12、plications,and network man-ager.Wireless field devices are connected to process or plant equipment.Gateways enable the communication be-tween the wireless field devices and the host applications. The process automation controller serves as a single con-troller for continuous process.The network mana
13、ger con-figures the network and schedule communication between devices. It also manages the routing and network traffic. The network manager can be integrated into the gateway, host application, or process automation control-ler. WirelessHART standards were released to the industry in September 2007
14、 and will soon be available in commer- cial products. ISA100.11a: ISA100.11a 42 standard is designed for low data rate wireless monitoring and process automation applications. It defines the specifications for the OSI layer, security, and system management.The standard focuses on low energy consumpt
15、ion,scalability, infrastructure,robustness, and interoperability with other wireless de-vices. ISA100.11a networks use only 2.4 GHz radio and channel hopping to increase reliability and minimize inter-ference.It offers both meshing and star network topolo-gies. ISA100.11a also provides simple, exibl
16、e, and scaleable security functionality. 6LoWPAN: IPv6-based Low power Wireless Personal Area Networks 43-45 enables IPv6 packets communica-tion over an IEEE802.15.4 based network.Low power device can communicate directly with IP devices using IP-based protocols. Using 6LoWPAN,low power devices have all the benefits of IP communication and management.6LoWPAN standard provides an adaptation layer, new packet format, and address management. Beca
