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The technology is designed to be simpler and cheaper than other WPAN s such as Bluetooth. The most capable ZigBee node type is said to require only about 10% of the software of a typical Bluetooth or Wireless Internet node, while the simplest nodes are about 2%.
As of 2004, the estimated cost of the radio for a ZigBee node is about $6 to the manufacturer.
ZigBee is aimed at applications with low data rates and low power consumption. ZigBee's current focus is to define a general-purpose, inexpensive self-organizing mesh network that can be shared by industrial controls, medical devices, smoke and intruder alarms, building-automation and home automation. The network is designed to use very small amounts of power, so that individual devices might run for a year or two with a single alkaline battery. The killer appA killer application (commonly shortened to killer app is a computer program that is so useful that people will buy a particular brand of computer simply to run that program. The first example of a killer app is generally agreed to be the VisiCalc spreads is probably meter-reading, although other applications, such as wireless light controls, should also be popular.
There are three basically different types of ZigBee devices: The most capable is a "ZigBee coordinator." It might bridge to other networks, and forms the root of the network tree. It is able to store information about the network. There is exactly one ZigBee coordinator in each network. A "full function device" (FFD) can act as an intermediate router, passing data from other devices. A "reduced function device" (RFD) is just smart enough to talk to the network; it cannot relay data from other devices. An RFD requires less memory, and therefore should be less expensive to manufacture, than an FFD. Similarly, an FFD requires less memory, and therefore should be less expensive to manufacture, than a ZigBee coordinator.
The protocols build on recent algorithmic research to automatically construct a low-speed ad-hoc network of nodes. In most large cases, the network is a cluster of clusters. It can also form a mesh or a single cluster.
The ZigBee protocols support both beaconing and non-beaconing networks. In beaconing networks, the network nodes transmit beacons to confirm their presence to other network nodes, and to allow nodes to sleep between beacons, thereby lowering their duty cycle and extending their battery life. Beacon intervals may range from 15.36 milliseconds to 15.36 ms * 2^14 = 251.65824 seconds; to obtain the benefits of low duty cycle operation with long beacon intervals, however, precise timing is needed, which can conflict with the need for low product cost. In non-beaconing networks, most devices typically have their receivers continuously active, requiring a more robust power supply; however, this enables heterogeneous networks, in which some devices receive continuously while some remain asleep, transmitting only when an external stimulus is detected. The typical example of a heterogeneous network is the wireless light switch: The ZigBee node at the lamp may receive constantly, since it is connected to the mains supply, while the battery-powered light switch remains asleep until the switch is thrown. The switch then wakes up, sends a command to the lamp, receives an acknowledgement, and returns to sleep. In such a network the lamp node is at least an FFD, if not the ZigBee coordinator; the switch node is typically an RFD.
In general, the ZigBee protocols minimize the time the radio is on in order to reduce the power used by the radio. In beaconing networks the network synchronizes nodes to talk and listen at particular times when they have anything to hear or say. In non-beaconing networks, power consumption is more asymmetrical; some devices are constantly active, while others (if present) are almost always asleep.
ZigBee uses the IEEE 802.15.4 Low-Rate Wireless Personal Area Network (WPAN) standard to describe its lower protocolFor the meaning in computer science, see protocol (computing). In addition to the meaning below, treaties are sometimes called protocols. The word derives from a Greek phrase meaning "first leaf", referring to the first draft of a treaty. Protocol is the layerA layer is the following: In abstraction, a layer is an abstract place conceived as having depth. In telecommunications a layer is an F region. In telecommunications networks and open systems architecture a layer is a group of related functions that are ps--the physical layer ( PHY ), and the medium access control ( MACMAC has several meanings, including: MAC (cosmetics) erroneously Macintosh computer by Apple Maximum Allowable Concentration of toxins, e. in food or as reference in environmental remediation mandatory access control Media Access Control hence MAC address) portion of the data link layer (DLL). This standard specifies operation in the unlicensed 2.4 GHz, 915 MHz and 868 MHz ISM bandThe industrial, scientific, and medical (ISM radio bands were originally reserved internationally for non-commercial use of RF electromagnetic fields for industrial, scientific and medical purposes. The ISM bands are defined by the ITU-T in S5. 150 of thes. The radio uses DSSSIn telecommunication, the term direct-sequence spread spectrum has the following meanings: 1. A system (a) for generating spread-spectrum transmissions by phase-modulating a sine wave pseudorandomly with a continuous string of pseudonoise code symbols, ea which is managed by the digital stream into the modulator. Conventional DSSS is employed in the 868 and 915 MHz bands, while an orthogonal signaling scheme that transmits four bits per symbol is employed in the 2.4 GHz band. The raw, over-the-air data rate is 250 kb/ s per channel in the 2.4 GHz band, 40 kb/s per channel in the 915 MHz band, and 20 kb/s in the 868 MHz band. Transmission range is between 10 and 75 metres (33~250 feet).
The basic mode of channel access specified by IEEE 802.15.4 is "carrier sense, multiple access" ( CSMA), that is, the nodes talk in the same way that people converse--they briefly check to see that no one is talking before they start. Beacons, however, are sent on a fixed timing schedule, and do not use CSMA. Message acknowledgements also do not use CSMA.