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Zigbee

What is ZigBee

The mission of the ZigBee Working Group is to bring about the existence of

a broad range of interoperable consumer devices by establishing open

industry specifications for unlicensed, untethered peripheral, control and

entertainment devices requiring the lowest cost and lowest power

consumption communications between compliant devices anywhere in andaround the home.

The ZigBee membership includes Philips, Honeywell and Invensys

Metering Systems, and others and is responsible for defining and

maintaining higher layers above the MAC. The alliance is also developing

application profiles, certification programs, logos and a marketing strategy.

Philips Semiconductors and other chip vendors plan to launch their first

ZigBee products as early as 2003. ZigBee was formerly known as

PURLnet, RF-Lite, Firefly, and HomeRF Lite.

The ZigBee logo

The ZigBee specification is a combination of HomeRF Lite and the

802.15.4 specification. The spec operates in the 2.4GHz (ISM) radio band -

the same band as 802.11b standard, Bluetooth, microwaves and some other

devices. It is capable of connecting 255 devices per network. The

specification supports data transmission rates of up to 250 Kbps at a range ofup to 30 meters. ZigBee's technology is slower than 802.11b (11 Mbps) and

Bluetooth (1 Mbps) but it consumes significantly less power.

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ZigBee is a home-area network designed specifically to replace the

proliferation of individual remote controls. ZigBee was created to satisfy the

market's need for a cost-effective, standards-based wireless network that

supports low data rates, low power consumption, security, and reliability. To

address this need, the ZigBee Alliance, an industry working group

(www.zigbee.org), is developing standardized application software on top of

the IEEE 802.15.4 wireless standard. The alliance is working closely with

the IEEE to ensure an integrated, complete, and interoperable network for

the market. For example, the working group will provide interoperability

certification testing of 802.15.4 systems that include the ZigBee software

layer.

The ZigBee Alliance will also serve as the official test and certification

group for ZigBee devices. ZigBee is the only standards-based technology

that addresses the needs of most remote monitoring and control and sensorynetwork applications.

ZigBee/IEEE 802.15.4 - General Characteristics:

Dual PHY (2.4GHz and 868/915 MHz)

Data rates of 250 kbps (@2.4 GHz), 40 kbps (@ 915 MHz), and 20kbps (@868 MHz)

Optimized for low duty-cycle applications (

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History

ZigBee-style networks began to be conceived around 1998, when

many installers 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 radio 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 the 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 the 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, and byDecember 2005 membership had passed 200 companies.

The ZigBee specifications were ratified on 14 December 2004.

The ZigBee Alliance announces public availability of Specification

1.0 on 13 June 2005, known as ZigBee 2004 Specification.

The ZigBee Alliance announces the completion and immediate

member availability of the enhanced version of the ZigBee Standard

in September 2006, known as ZigBee 2006 Specification.

During the last quarter of 2007, ZigBee PRO, the enhanced ZigBee

specification was finalized.

Origin of ZigBee name

The name of the brand is originated with reference to thebehavior of honey

bees after their return to the beehive.

As an international non-profit association of professional engineers, the

IEEE provides a forum that engages in the worldwide advancement of all

forms of technology that relate to the use of electricity. With members in

over 175 countries around the globe, the Institute of Electrical and

Electronic Engineers ensures that information about developments within

the engineering field are readily available to all electrical professionals,

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regardless of where they live and work. Here is some background on the

IEEE, how it functions, and how membership in this professional

organization benefits many industries.

Electricity is an essential commodity in the function of most types of

business today. Without access to the latest technology, many companies

would fall behind and ultimately fail. From such important industries as

telecommunications to international manufacturing corporations, electronics

play a key role in product and service distribution, sales efforts, and general

operations. The work of the IEEE makes it possible for businesses in all

types of industries to be aware of and utilize electricity option to the fullest.

Formed in 1963 by the mergerof the Institute of Radio Engineers and the

American Institute of Electrical Engineers, the IEEE combined the specific

interests of both organizations into one interrelated focus. Including suchvital areas as wire communications,power supply systems, and radio

engineering, the formation of the IEEE resolved the issue of competing

organizations whose areas of expertise were becoming increasingly

intertwined in a modern world. The end result was the establishment of a

central conduit of information flow that would allow the association to

effectively make use of innovations in a number of electrical related fields.

This central information flow provided members with the chance to learn

from one another in ways that was not possible prior to that time.

Today, the IEEE makes use of a number of learning opportunities, such asprofessional journals, online learning tools, conferences and conventions and

accredited courses to further the interests of electronic technology in the

world today. Many countries have benefited from the presence of certified

IEEE members in residence, since they often have access to concepts and

ideas that help to improve the internal power supply structure and offer new

solutions to old problems.

ZigBee is the set of specs built around the IEEE 802.15.4 wireless protocol.

The IEEE is theInstitute of Electrical and Electronics Engineers, a non-

profit organization dedicated to furthering technology involving electronics

and electronic devices. The 802 group is the section of the IEEE involved in

network operations and technologies, including mid-sized networks and

local networks. Group 15 deals specifically with wireless networking

technologies, and includes the now ubiquitous 802.15.1 working group,

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which is also known as Bluetooth. The standard itself is regulated by a

group known as the ZigBee Alliance, with over 150 members worldwide.

While Bluetooth focuses on connectivity between large packet user

devices, such as laptops, phones, and major peripherals, ZigBee is designed

to provide highly efficient connectivity between small packet devices. As a

result of its simplified operations, which are one to two full orders of

magnitude less complex than a comparable Bluetooth device, pricing for

ZigBee devices is extremely competitive, with full nodes available for a

fraction of the cost of a Bluetooth node.

ZigBee devices are actively limited to a through-rate of 250 Kbps, compared

to Bluetooth's much larger pipeline of 1Mbps, operating on the 2.4 GHz

ISM band, which is available throughout most of the world.

ZigBee has been developed to meet the growing demand for capable

wireless networking between numerous low-power devices. In industry

ZigBee is being used for next generation automated manufacturing, with

small transmitters in every device on the floor, allowing for communication

between devices to a central computer. This new level of communication

permits finely-tuned remote monitoring and manipulation. In the consumer

market ZigBee is being explored for everything from linking low-power

household devices such as smoke alarms to a central housing control unit, to

centralized light controls.

The specified maximum range of operation for ZigBee devices is 250 feet

(76m), substantially further than that used by Bluetooth capable devices,

although security concerns raised over "sniping" Bluetooth devices

remotely, may prove to hold true for ZigBee devices as well.

Due to its low power output, ZigBee devices can sustain themselves on a

small battery for many months, or even years, making them ideal for install-

and-forget purposes, such as most small household systems. Predictions of

ZigBee installation for the future, most based on the explosive use of ZigBee

in automated household tasks in China, look to a near future when upwards

of 60 ZigBee devices may be found in an average American home, all

communicating with one another freely and regulating common tasks

seamlessly.

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Concept behind development of Zigbee

Why do we require zigbee when we already have Bluetooth

Why the ZigBee Standard?

ZigBee was created to address the market need for a cost-effective,standards-based wireless networking solution that supports low data-rates,

low-power consumption, security, and reliability. ZigBee is the only

standards-based technology that addresses the unique needs of most remote

monitoring and control and sensory network applications.

The initial markets for the ZigBee Alliance include Consumer Electronics,

Energy Management and Efficiency, Health Care, Home Automation,

Building Automation and Industrial Automation.

The ZigBee Alliance

The ZigBee Alliance is an association of companies working together on an

open global standard for wireless network monitoring and control products.

ZigBee enables companies to have a simple, reliable, low-power, global

wireless public standard optimized for the unique needs of remote

monitoring and control applications.

Zigbee alliance has more than 150+ members

and many more....

http://www.zigbee.com/http://www.zigbee.com/

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ZigBee stack architecture

It may be helpful to think of IEEE 802.15.4 as the physical radio and ZigBee

as the logical network and application software, as Figure 1 illustrates.

Following the standard Open Systems Interconnection (OSI) reference

model, ZigBee's protocol stack is structured in layers. The first two layers,

physical (PHY) and media access (MAC), are defined by the IEEE 802.15.4

standard. The layers above them are defined by the ZigBee Alliance. The

IEEE working group passed the first draft of PHY and MAC in 2003. A final

version of the network (NWK) layer is expected sometime this year.

ZigBee-compliant products operate in unlicensed bands worldwide,

including 2.4GHz (global), 902 to 928MHz (Americas), and 868MHz

(Europe). Raw data throughput rates of 250Kbps can be achieved at 2.4GHz

(16 channels), 40Kbps at 915MHz (10 channels), and 20Kbps at 868MHz (1channel). The transmission distance is expected to range from 10 to 75m,

depending on power output and environmental characteristics. Like Wi-Fi,

Zigbee uses direct-sequence spread spectrum in the 2.4GHz band, with

offset-quadrature phase-shift keying modulation. Channel width is 2MHz

with 5MHz channel spacing. The 868 and 900MHz bands also use direct-

sequence spread spectrum but with binary-phase-shift keying modulation.

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The four basic frame types defined in 802.15.4: Data, ACK,

MAC command, and beacon

The data frame provides a payload of up to 104 bytes. The frame isnumbered to ensure that all packets are tracked. A frame-check sequence

ensures that packets are received without error. This frame structure

improves reliability in difficult conditions.

Another important structure for 802.15.4 is the acknowledgment (ACK)

frame. It provides feedback from the receiver to the sender confirming that

the packet was received without error. The device takes advantage of

specified "quiet time" between frames to send a short packet immediately

after the data-packet transmission.

A MAC command frame provides the mechanism for remote control and

configuration of client nodes. A centralized network manager uses MAC to

configure individual clients' command frames no matter how large thenetwork.

Finally, the beacon frame wakes up client devices, which listen for theiraddress and go back to sleep if they don't receive it. Beacons are important

for mesh and cluster-tree networks to keep all the nodes synchronized

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without requiring those nodes to consume precious battery energy by

listening for long periods of time.

Channel access, addressing

Two channel-access mechanisms are implemented in 802.15.4. For a

non"beacon network, a standard ALOHA CSMA-CA (carrier-sensemedium-access with collision avoidance) communicates with positive

acknowledgement for successfully received packets. In a beacon-enabled

network, a superframe structure is used to control channel access. The

superframe is set up by the network coordinator to transmit beacons at

predetermined intervals (multiples of 15.38ms, up to 252s) and provides 16

equal-width time slots between beacons for contention-free channel access

in each time slot. The structure guarantees dedicated bandwidth and low

latency. Channel access in each time slot is contention-based. However, the

network coordinator can dedicate up to seven guaranteed time slots per

beacon interval for quality of service.

Device addresses employ 64-bit IEEE and optional 16-bit short addressing.

The address field within the MAC can contain both source and destination

address information (needed for peer-to-peer operation). This dual address

information is used in mesh networks to prevent a single point of failure

within the network.

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