Zigbee technology
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  • 1. www.1000projects.comwww.fullinterview.comwww.chetanasprojects.comZIGBEE TECHNOLOGY The ZigBee Alliance, the standards bodyABSTRACT: which defines ZigBee,[1] also publishesZigBee is the name of a specification for a application profiles that allow multiplesuite of high level communication protocols OEM vendors to create interoperableusing small, low-power digital radios based products. The current list of applicationon the IEEE 802.15.4-2006 standard for profiles either published or in the works are:wireless personal area networks (WPANs), • Home Automationsuch as wireless headphones connecting • ZigBee Smart Energywith cell phones via short-range radio. The • Telecommunication Applicationstechnology is intended to be simpler and less • Personal Homeexpensive than other WPANs, such asBluetooth. ZigBee is targeted at radio- INTRODUCTION:frequency (RF) applications that require a ZigBee is the name of a specification for a suitelow data rate, long battery life, and secure of high level communication protocols usingnetworking. small, low-power digital radios base on the IEEEZigBee is a low-cost, low-power, wireless 802.15.4-2006 standard for wireless personalmesh networking standard. The low cost area networks (WPANs), such as wirelessallows the technology to be widely deployed headphones connecting with cell phones viain wireless control and monitoring short-range radio. The technology is intendedapplications, the low power-usage allows to be simpler and less expensive than otherlonger life with smaller batteries, and the WPANs, such as Bluetooth. ZigBee is targeted atmesh networking provides high reliability radio-frequency (RF) applications that require aand larger range. 1www.1000projects.comwww.fullinterview.comwww.chetanasprojects.com
  • 2. www.1000projects.comwww.fullinterview.comwww.chetanasprojects.comlow data rate, long battery life, and secure ZigBee 2007 network, the same as ZigBeenetworking. 2006 or ZigBee 2007 devices must become ZEDs on a ZigBee Pro network.OVERVIEW:The relationship between IEEE 802.15.4 and DEVICE TYPES AND HISTORYZigBee is similar to that between IEEE There are three different types of ZigBee802.11 and the Wi-Fi Alliance. The ZigBee devices:1.0 specification was ratified on 14 • ZigBee coordinator (ZC): The mostDecember 2004 and is available to members capable device, the coordinatorof the ZigBee Alliance. The first ZigBee forms the root of the network treeApplication Profile, Home Automation, was and might bridge to other networks.announced 2 November 2007. There is exactly one ZigBeeThe first stack release is now called Zigbee coordinator in each network since it2004. The second stack release is called is the device that started the networkZigbee 2006, and mainly replaces the originally. It is able to storeMSG/KVP structure used in 2004 with a information about the network,"cluster library". including acting as the Trust CentreZigbee 2007, now the current stack release, & repository for security keys.contains 2 stack profiles, stack profile 1 • ZigBee Router (ZR): As well as(simply called ZigBee), for home and lightcommercial use, and stack profile 2 (called running an application function aZigBee Pro). ZigBee 2007 is fully backward router can act as an intermediatecompatible with ZigBee 2006 devices. Due router, passing data from otherto differences in routing options, ZigBee Pro devicesdevices must become non-routing ZigBee • ZigBee End Device (ZED): ContainsEnd-Devices (ZEDs) on a ZigBee 2006 or just enough functionality to talk to the parent node (either the 2www.1000projects.comwww.fullinterview.comwww.chetanasprojects.com
  • 3. www.1000projects.comwww.fullinterview.comwww.chetanasprojects.com coordinator or a router); it cannot the other hand, an uncertified physical layer relay data from other devices. This that malfunctions could cripple the battery relationship allows the node to be lifespan of other devices on a ZigBee asleep a significant amount of the network. Where other protocols can mask time thereby giving long battery life. poor sensitivity or other esoteric problems in A ZED requires the least amount of a fade compensation response, ZigBee memory, and therefore can be less radios have very tight engineering expensive to manufacture than a ZR constraints: they are both power and or ZC. bandwidth constrained. Thus, radios are tested to the ISO 17025 standard withSoftware and hardware: guidance given by Clause 6 of the 802.15.4-The software is designed to be easy to 2006 Standard. Most vendors plan todevelop on small, inexpensive integrate the radio and microcontroller ontomicroprocessors. The radio design used by a single chip.ZigBee has been carefully optimized for lowcost in large scale production. It has few History:analog stages and uses digital circuits • ZigBee-style networks began to bewherever possible. conceived about 1998, when manyEven though the radios themselves are installers realized that both WiFi andinexpensive, the ZigBee Qualification Bluetooth were going to beProcess involves a full validation of the unsuitable for many applications.requirements of the physical layer. This • The IEEE 802.15.4 standard wasamount of concern about the Physical Layer completed in May 2003.has multiple benefits, since all radios • The ZigBee specifications werederived from that semiconductor mask set ratified on 14 December 2004.would enjoy the same RF characteristics. On 3www.1000projects.comwww.fullinterview.comwww.chetanasprojects.com
  • 4. www.1000projects.comwww.fullinterview.comwww.chetanasprojects.com • The ZigBee Alliance announces A ZigBee network can adopt one of the public availability of Specification three topologies: Star, Tree, Mesh. These 1.0 on 13 June 2005, known as are illustrated on the left and briefly ZigBee 2004 Specification. described below. Star Topology : A Star network has a central node, which is linked to all other nodes in the network. All messages travel via the central node. Tree Topology :Origin of the term ZigBee: A Tree network has a top node with aAn urban myth perpetuated by the Zigbee branch/leaf structure below. To reach itsAlliance is that the term “ZigBee” originates destination, a message travels up the tree (asfrom the silent, but powerful method of far as necessary) and then down the tree.communication used by honeybees to report Mesh Topology:information about food sources. The myth A Mesh network has a tree-like structure insays that the communication system is which some leaves are directly linked. [8]known as the “ZigBee Principle" . By Messages can travel across the tree, when a"dancing" around in a zig-zag waggle dance, suitable route is available.a bee is able to share critical information,such as the location, distance, and direction Node Typesof a newly discovered food source to its This section describes the types of node thatfellow hive members. are used in a ZigBee network. Reference will be made to the toplogies introduced onZigBee Topologies the previous page (Star, Tree, Mesh), butTopology Overview : these topologies will be described in more detail later in this module. 4www.1000projects.comwww.fullinterview.comwww.chetanasprojects.com
  • 5. www.1000projects.comwww.fullinterview.comwww.chetanasprojects.comThe ZigBee standard has the capacity to tasks of the Co-ordinator at the networkaddress up to 65535 nodes in a single layer are:network. However, there are only three • Selects the frequency channel to begeneral types of node: used by the network (usually the one • Co-ordinator with the least detected activity) • End Device • Starts the network • Router • Allows other devices to connect to itThese node types are described below. (that is, to join the network)Co-ordinator The Co-ordinator can also provide messageAll ZigBee networks must have one (and routing (for example, in a Star network),only one) Co-ordinator, irrespective of the security management and other services.network topology. End Device • In the Star topology, the Co- End Devices are always located at the ordinator is the central node in the extremeties of a network: network. • In the Star topology, they are • In the Tree and Mesh topologies, the perimeter nodes Co-ordinator is the top (root) node in • In the Tree and Mesh toplogies, they the network. are leaf nodes This is illustrated below, where the End Devices are colour-coded in light blue.At the network level, the Co-ordinator ismainly needed at system initialisation. The 5www.1000projects.comwww.fullinterview.comwww.chetanasprojects.com
  • 6. www.1000projects.comwww.fullinterview.comwww.chetanasprojects.comThe specification goes on to complete the The Application Framework (AF) containsstandard by adding four main components: the application objects and facilitates • network layer interaction between the applications and the • application layer APS layer. An application object interacts with the APS layer through an interface • ZigBee device objects (ZDOs) known as a Service Access Point (SAP). (keeping of device roles, Service Access Points management of requests to join a A Service Access Point (SAP) implements a network, device discovery and set of operations to pass information and security) commands between layers. There are usually • manufacturer-defined application four types of operation implemented by a objects which allow for SAP: customization and favor total Request: Typically, a layer using the integration. services of another layer generates a RequestOn completing this section, you will be able to the lower layer.to describe: Confirm: In general, the lower layer • the three basic levels of the ZigBee responds with a Confirm, which indicates software stack whether it has accepted or rejected the • application endpoints that reside in a request. A rejection could occur if the ZigBee node Request is invalid or the layer does not • the components of the basic stack implement the operation concerned (the levels SAPs that allow an application operation could be defined as optional). to communicate with lower software Response: Normally, Requests result in layers and remote applications some sort of Response from the lower layer. This may be a simple status messageApplication Framework and SAPs indicating that the Request has beenApplication Framework 7www.1000projects.comwww.fullinterview.comwww.chetanasprojects.com
  • 7. www.1000projects.comwww.fullinterview.comwww.chetanasprojects.comThe main tasks of an End Device at the • In a Mesh topology, a Router can benetwork level are sending and receiving located anywhere that a messagemessages. Note that End Devices cannot passing node is required.relay messages and cannot allow other nodes However, in all topologies (Star, Tree andto connect to the network through them. Mesh), Router devices can be located at theAn End Device can often be battery- extremeties of the network, if they runpowered and, when not transmitting or applications that are needed in thesereceiving, can sleep in order to conserve locations - in this case, the Router will notpower. perform its message relay function, unless inRouter a Mesh network (see above).Networks with Tree or Mesh topologies The possible positions of Routers in theneed at least one Router. The main tasks of a different network topologies are illustratedRouter are: below, where the Routers are colour-coded • Relays messages from one node to in red: another • Allows child nodes to connect to itIn a Star topology, these functions arehandled by the Co-ordinator and, therefore,a Star network does not need Routers.In Tree and Mesh topologies, Routers are Note that a Router cannot sleep.located as follows: • In a Tree topology, Routers are ZigBee Software Architecture: normally located in network ZigBee builds upon the physical layer and positions that allow messages to be medium access control defined in IEEE passed up and down the tree. standard 802.15.4 (2003 version) for low- rate WPANs. 6www.1000projects.comwww.fullinterview.comwww.chetanasprojects.com
  • 8. www.1000projects.comwww.fullinterview.comwww.chetanasprojects.comThe ZigBee standard has the capacity to tasks of the Co-ordinator at the networkaddress up to 65535 nodes in a single layer are:network. However, there are only three • Selects the frequency channel to begeneral types of node: used by the network (usually the one • Co-ordinator with the least detected activity) • End Device • Starts the network • Router • Allows other devices to connect to itThese node types are described below. (that is, to join the network)Co-ordinator The Co-ordinator can also provide messageAll ZigBee networks must have one (and routing (for example, in a Star network),only one) Co-ordinator, irrespective of the security management and other services.network topology. End Device • In the Star topology, the Co- End Devices are always located at the ordinator is the central node in the extremeties of a network: network. • In the Star topology, they are • In the Tree and Mesh topologies, the perimeter nodes Co-ordinator is the top (root) node in • In the Tree and Mesh toplogies, they the network. are leaf nodes This is illustrated below, where the End Devices are colour-coded in light blue.At the network level, the Co-ordinator ismainly needed at system initialisation. The 5www.1000projects.comwww.fullinterview.comwww.chetanasprojects.com