ZigBee_WikiP (Раздаточные материалы)

ZigBee is the name of a specification for a suite of high level communication protocols using small, low-power digital radios based on the IEEE 802.15.4 standard for wireless personal area networks (WPANs). The relationship between IEEE 802.15.4-2003 and ZigBee is similar to that between IEEE 802.11 and the Wi-Fi Alliance. The ZigBee 1.0 specification was ratified on December 14, 2004 and is available to members of the ZigBee Alliance. An entry level membership in the ZigBee Alliance costs US$ 3500 and provides access to the specifications. For non-commercial purposes, the ZigBee specification is available to the general public at the ZigBee Alliance homepage.

Contents [hide] 1 Introduction 2 Uses 3 Device types 4 Protocols 5 Software and hardware 6 ZigBee Home Automation Example 7 History 8 Device vendors 9 Chip/firmware vendors 10 External links 11 Related Technologies 11.1 Wireless 11.2 Powerline Protocols 11.3 Other Platforms and Protocols

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Introduction

ZigBee operates in the industrial, scientific and medical (ISM) radio bands; 868 MHz in Europe, 915 MHz in the USA and 2.4 GHz in most jurisdictions worldwide. The technology is intended to be simpler and cheaper than other WPANs 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%. However, actual code sizes are much higher, closer to 50% of Bluetooth code size. ZigBee chip vendors have announced 128-kilobyte devices.

As of 2005, the estimated cost of the radio for a ZigBee node is about $1.10 to the manufacturer in very high volumes. Most ZigBee solutions require an additional micro controller driving the price further up at this time. In comparison, before Bluetooth was launched (1998) it had a projected price, in high volumes, of $4-$6. The price of consumer-grade Bluetooth chips are now under $3.

ZigBee has started work on version 1.1. Version 1.1 is meant to take advantage of improvements in the 802.15.4b specification, most notably that of CCM* as an alternative to CCM (CTR + CBC-MAC) CCM mode. CCM* enjoys the same security proof as CCM and provides greater flexibility in the choice of Authentication and Encryption.

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Uses

ZigBee protocols are intended for use in embedded applications requiring 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 used for industrial control, embedded sensing, medical data collection, smoke and intruder warning, building automation, home automation, domotics, etc. The resulting network will use very small amounts of power so individual devices might run for a year or two using the originally installed battery.

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Device types

There are three different types of ZigBee device:

• ZigBee coordinator(ZC): The most capable device, the coordinator forms the root of the network tree and might bridge to other networks. There is exactly one ZigBee coordinator in each network. It is able to store information about the network, including acting as the repository for security keys.

• ZigBee Router (ZR): Routers can act as an intermediate router, passing data from other devices.

• ZigBee End Device (ZED): Contains just enough functionality to talk to its parent node (either the coordinator or a router); it cannot relay data from other devices. It requires the least amount of memory, and therefore can be less expensive to manufacture than a ZR or ZC.

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Protocols

The protocols build on recent algorithmic research (Ad-hoc On-demand Distance Vector) to automatically construct a low-speed ad-hoc network of nodes. In most large network instances, the network will be a cluster of clusters. It can also form a mesh or a single cluster. The current profiles derived from the ZigBee protocols support beacon and non-beacon enabled networks.

In non-beacon enabled networks (those whose beacon order is 15), an unslotted CSMA/CA channel access mechanism is used. In this type of network Zigbee Routers typically have their receivers continuously active, requiring a more robust power supply. However, this allows for heterogeneous networks in which some devices receive continuously, while others only transmit when an external stimulus is detected. The typical example of a heterogeneous network is a wireless light switch: the ZigBee node at the lamp may receive constantly, since it's connected to the mains supply, while a battery-powered light switch would remain asleep until the switch is thrown. The switch then wakes up, sends a command to the lamp, receives an acknowledgment, and returns to sleep. In such a network the lamp node will be at least a ZigBee Router, if not the ZigBee Coordinator; the switch node is typically an ZigBee End Device.

In beacon enabled networks, the special network nodes called ZigBee Routers transmit periodic beacons to confirm their presence to other network nodes. Nodes may sleep between beacons, thus lowering their duty cycle and extending their battery life. Beacon intervals may range from 15.36 milliseconds to 15.36 ms * 2¹⁴ = 251.65824 seconds at 250 kbit/s, from 24 milliseconds to 24 ms * 2¹⁴ = 393.216 seconds at 40 kbit/s and from 48 milliseconds to 48 ms * 2¹⁴ = 786.432 seconds at 20 kbit/s. However, low duty cycle operation with long beacon intervals requires precise timing which can conflict with the need for low product cost.

In general, the ZigBee protocols minimize the time the radio is on so as to reduce power use. In beaconing networks, nodes only need to be active while a beacon is being transmitted. In non-beacon enabled networks, power consumption is decidedly asymmetrical: some devices are always active, while any others present spend most of their time sleeping.

ZigBee devices are required to conform to the IEEE 802.15.4-2003 Low-Rate Wireless Personal Area Network (WPAN) standard. The standard specifies its lower protocol layers—the physical layer (PHY), and the medium access control (MAC) portion of the data link layer (DLL). This standard specifies operation in the unlicensed 2.4 GHz, 915 MHz and 868 MHz ISM bands. In the 2.4 GHz band there are 16 ZigBee channels, with each channel requiring 3 MHz of bandwidth. The center frequency for each channel can be calculated as, F_C = (2400 + 5*k) MHz, where k = 1, 2, ..., 16.

The radios use direct-sequence spread spectrum coding, which is managed by the digital stream into the modulator. BPSK is used in the 868 and 915 MHz bands, and orthogonal QPSK that transmits two bits per symbol is used in the 2.4 GHz band. The raw, over-the-air data rate is 250 kbit/s per channel in the 2.4 GHz band, 40 kbit/s per channel in the 915 MHz band, and 20 kbit/s in the 868 MHz band. Transmission range is between 10 and 75 metres (33~246 feet), although it is heavily dependent on the particular environment. The maximum output power of the radios is generally 0 dBm (1 mW).

The basic channel access mode specified by IEEE 802.15.4-2003 is "carrier sense, multiple access/collision avoidance" (CSMA/CA). 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. There are three notable exceptions to the use of CSMA. Beacons are sent on a fixed timing schedule, and do not use CSMA. Message acknowledgements also do not use CSMA. Finally, devices in Beacon Oriented networks that have low latency real-time requirements may also use Guaranteed Time Slots (GTS) which by definition do not use CSMA.

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Software and hardware

The software is designed to be easy to develop on small, cheap microprocessors. The radio design used by ZigBee has been carefully optimized for low cost in large scale production. It has few analog stages and uses digital circuits wherever possible.

Even though the radios themselves are cheap, the ZigBee Qualification Process involves a full validation of the requirements of the physical layer. This amount of concern about the Physical Layer has multiple benefits, since all radios derived from that semiconductor mask set would enjoy the same RF characteristics. On the other hand, an uncertifed physical layer that malfunctions could cripple the Battery lifespan of other devices on a Zigbee Network. Where other protocols can mask poor sensitivity or other esoteric problems in a fade compensation response, ZigBee radios have very tight engineering constraints: they are both power and bandwidth constrained. Thus, radios are tested to the ISO-17025 standard with guidance given by Clause 6 of the 802.15.4-2003 Standard. Most vendors plan to integrate the radio and microcontroller onto a single chip. (An interesting link: [1] look for the USB Dongle)

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ZigBee Home Automation Example

ZigBee Home Automation Example

The practical example shown is a home with a ZigBee network controlling lights, security system, fire system, and the heating and air conditioning.

The diagram shows a number of devices -- red marks a "router to router" link, and blue link an "end node to router" link.

Here, lighting fixture B (which might also be the "coordinator") has identified and established routes via routers embedded in lighting fixtures A and F, mains-powered (with battery backup) smoke detector C, and table lamp D.

All the routers are mains-powered devices (lamps, heat pump, lighting fixtures, smoke alarms) and the "end" devices are battery-powered (switches, thermostats, motion detectors). Sensors are bound to actuators sometimes through user choices, otherwise because of bindings specified by the manufacturer.

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History

• ZigBee-style networks began to be conceived about 1998, when many engineers realized that both WiFi and Bluetooth were going to be unsuitable for many applications. In particular, many engineers saw a need for self-organizing ad-hoc digital radios networks.

• The IEEE 802.15.4 standard was completed in May 2003.

• In the summer of 2003, Philips Semiconductors, a major mesh network supporter, ceased its investment. Philips Lighting has, however, continued Philips' participation, and Philips remains a promoter member on the ZigBee Alliance Board of Directors.

• The ZigBee Alliance announced in October 2004 that its membership had more than doubled in the preceding year and had grown to more than 100 member companies, in 22 countries. By April 2005 membership had grown to more than 150 companies.

• The ZigBee specifications were ratified on 14 December 2004.

• The ZigBee Alliance announces public availability of Specification 1.0 on 13 June 2005

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Device vendors

• Cirronet (802.15.4/ZigBee) - The ZMN-2400 2.4 GHz OEM module is available in 1 mW and 100 mW versions; the latter is also incorporated into separately available Modbus gateway, Ethernet gateway, signal conditioning board, and sensor modem products. The 900 MHz ZMN-900 OEM radio and derivative products are listed as "coming soon."

• MaxStream (802.15.4/ZigBee) - The "XBee" products are 2.4 GHz "radio modems" with a serial UART interface. Operation is peer-to-peer and mesh topologies are listed as "coming soon".

• Helicomm (802.15.4/ZigBee) - The "IP-Link" embeddable modules are 802.15.4-based transceivers operating at 916 MHz and 2.4 GHz. Modules support both modem-like features or can be used as "wireless MCU" to host custom applications. Company also offers 802.15.4-based multi-drop terminal products and GPRS/CDMA/3G integration with ZigBee WPAN.

• MeshNetics (formerly Luxoft Labs) (804.15.4/ZigBee) - The “ZigBit” OEM modules are based on Atmel ATmega 1281 MCU and AT86RF230 transceiver. The module measuring 18.8 x 13.5mm with PCB antenna output is available now. Versions with the external antenna connector and chip antenna are listed as “coming soon.”

• Crossbow Technology (802.15.4/ZigBee and nonstandard protocols) - Crossbow's MICA2, MICA2DOT, MICAz, and MCS Cricket radios are OEM modules compatible with a wide variety of Crossbow sensor modules (using the Atmel CPU). MICAz is the 2.4 GHz ZigBee radio (with Chipcon chipset). The Crossbows radios are relatively large, except for the MICA2DOT which is extremely small. The non-ZigBee versions use the open-source TinyOS stack, and support other frequencies such as 313.9–316.1 MHz, 433.1–434.8 MHz, 868–870 MHz, and 902–928 MHz.

• Millennial Net (ZigBee-like nonstandard protocol) - The MeshScape(tm) network consists of endpoints ("end node"), routers ("mesh node"), and a PC base station ("MeshGate"). The endpoints measure 1.5 x 0.6 inches for the OEM board; about twice that for the assembled demo board. The endpoints support typical analog/digital/USART sensor interface, and kits are available for 2.4 GHz and 916 MHz bands. NOTE: "MeshScape" is a renaming of Millennial Net's previous "i-Bean" (tm) brand.

• Dust Networks (802.15.4 but not ZigBee) - The SmartMesh(tm) transceivers ("motes") are OEM boards (1.2 x 1.1 inches) with a 3V Samtec MB1-130 interface supporting typical analog/digital/UART interfaces. Available in both 2.4 GHz (M2020) and 902–928 MHz (M1010) bands. The evaluation kit includes battery-powered plastic enclosures that are about 5" square.

• Innovative Wireless Technologies (802.15.4 and/or ZigBee) - The AXON(tm) transceiver modules utilize Chipcon radios and are available in 2.4 GHz, 915 MHz, and 868 MHz frequency bands. IWT also sells a nonstandard Synaptrix(tm) protocol stack that can be used with the same hardware.

• EnOcean (nonstandard mesh protocol) - The TCM 120/130 transceiver module is an 868.3 MHz OEM board measuring 24 x 42 x 5 mm. A limited mesh network can be formed using the TCM 110 repeater modules.

• Sensicast (802.15.4 or nonstandard mesh protocol) - They sell both retail packaged sensors and OEM boards that can participate in an endpoint/router/gateway mesh network ("SensiNet"). The endpoint modules are somewhat large compared to competitor products. Supported frequency bands include 900 MHz and 2.4 GHz. An 802.15.4 version is available (but not ZigBee).

• Microchip - Microchip Technology Announces Complete ZigBee™ Demonstration and Development Platform Supporting Multiple RF Transceivers; Offers Free Software

• FlexiPanel ZigBee/802.15.4 transceiver modules and firmware solutions using the Microchip ZigBee stack

• Control4 delivers a number of home automation devices using Ember ZigBee interfaces.

• Nedap Specials - Development and production of custom zigbee applications. Has experience with many wireless solutions including Zigbee. Located in the Netherlands.

• ShreeDutt Technologies Its company based in India.They have cost effective ZigBee module.One stop ZigBee product development.Required expertise in RF , embedded system & concurrent programming.Can provide Customized application development.Currently working on ZigBee based Automatic Meter Reading ( AMR ) solution and energy management solution.

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Chip/firmware vendors

• Atmel - The AT86RF230 Z-Link(tm) is an 802.15.4/ZigBee compliant 2.4 GHz radio chip.

• Oki Semiconductor - ML7065 2.4 GHz ZigBee/802.15.4 tranciever, the world's first integrated radio and IEEE802.15.4 MAC. Oki's chip is on one of the ZigBee certified development platforms

• Silicon Laboratories - Microcontrollers and complete development kits for ZigBee and 802.15.4 development.

• Chipcon/Texas Instruments - The 2.4 GHz CC2420 is an 802.15.4/ZigBee compliant radio chip operating at 2.4 GHz. The CC2430 is a ZigBee system-on-chip with a fast 8051 MCU, powerful peripherals and the CC2420 transceiver. Chipcon/TI also provides a full ZigBee stack for its devices.

• Freescale - The MC13193 is a 2.4 GHz RF transceiver data modem for ZigBee applications. The second-generation MC1321x family includes an 8-bit HCS08 microcontroller. Freescale also provides the full zigbee stack for its devices.

• Mindteck - Design & development services for ZigBee products, ZigBee applications and ZigBee protocol stacks.

• Ember Corporation - The EM250, EM260, and EM2420 are 802.15.4/ZigBee compliant 2.4 GHz radio chips. A ZigBee protocol stack firmware called "EmberZNet" is available, and also a nonstandard version called "EmberNet".

• San Juan Software - Develops firmware, ZigBee application level software and gives on-site ZigBee training.

• Jennic - The JT24Z001 2.4 GHz Transceiver and JS24Z121 2.4 GHz System on a Chip (SoC) Device for IEEE 802.15.4 and ZigBee standards. Also featured: JN5121, a 32bit Risc single chip processor/RF solution.

• Integration - 802.15.4/ZigBee compliant platforms, USB ZigBee Dongle, Training

• Wireless-Tools - 802.15.4/ZigBee compliant platforms, USB ZigBee Dongle, Training123

• Helicomm - ZigBee/802.15.4 stacks, profiles, and tools for Freescale/8051 MCUs and leading 802.15.4 transceiver ICs.

• UBEC - ZigBee/802.15.4 Transceiver IC (UZ2400-single chip at 2.4 GHz), ZigBee software stacks, evaluation board design and consultant

• MeshNetics (formerly Luxoft Labs) - 802.15.4/ZigBee “eZeeNet” networking stack firmware is based on modified TinyOS. The “ZigBeeNet” is a full ZigBee stack.

• IP Cores CCM* IP Core

• Institute for Information Industry - A leading ZigBee/802.15.4 software stacks/solutions provider in Taiwan.

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External links

• ZigBee

• ZigBee Tutorial and Forum Includes information on Technology, Architecture, Devices, Comparisons and Applications.

• Zigbee introduction course An introduction on Zigbee in the English and Dutch language.

• ZigbeeMania Resource site for documentation and links to ZigBee solutions

• Who Needs ZigBee? - Explains the difference between wireless standards, and provides insight into how ZigBee differs from the others.

• Palowireless ZigBee Resource Center Articles, news and resources.

• ZigBee Chatter Slashdot users discuss ZigBee technology

• IEEE 802.15.4 web site

• Open Source 802.15.4 Open Source implementation of an IEEE 802.15.4 stack for Freescale HCS08 and MC13192 in TinyOS.

• OpenBee A ZigBee Development Kit with a ZigBee Stack developed in UML

• A ZigbeeTM-subset/IEEE 802.15.4TM Multi-platform Protocol Stack A Zigbee-subset/IEEE 802.15.4 Multi-platform stack for educational, research, personal use; compatible with Microchip PICDEMZ and TI/Chipcon CC2430 SOC platforms.

• Using ZigBee Wireless Networking to Develop Commercial Products

• ZigBee Spanish Tutorial Includes Spanish information on Zigbee Technology.

• WSNUpdate.com News and Info on Zigbee and Wireless Sensor Networks