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Seminar Report On ZigBee: Next Generation Wireless Network
Seminar Report
ZigBee: Next Generation Wireless Network
Submitted by
Anil Kumar K
In the partial fulfillment of requirements in degree of
Master of Technology (M-Tech)
2005Page 2

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
ZigBee is an open technology developed by the SigBee Alliance to overcome the limitations of
BLUETOOTH and Wi-Fi. ZigBee is an IEEE 802.15.4 standard for data communications with
business and consumer devices. It is designed around low-power consumption allowing batteries to
essentially last forever. BLUETOOTH as we know was developed to replace wires and Wi-Fi to
achieve higher data transfer rate, as such till now nothing has been developed for sensor networking
and control machines which require longer battery life and continuous working without human
intervention. ZigBee devices allow batteries to last up to years using primary cells (low cost)
without any chargers (low cost and easy installation).
The ZigBee standard provides network, security, and application support services operating on top
of the IEEE 802.15.4 Medium Access Control (MAC) and Physical Layer (PHY) wireless standard.
It employs a suite of technologies to enable scalable, self-organizing, self-healing networks that can
manage various data traffic patterns. The network layer supports various topologies such star,
clustered tree topology and self healing mesh topology which is essential in Smartdust
Apart from easy installation and easy implementation ZigBee has a wide application area such as
home networking, industrial networking, Smartdust, many more, having different profiles specified
for each field. The upcoming of ZigBee will revolutionize the home networking and rest of the
wireless world. Page 3

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
Table of Contents
1. Intorduction
2. Existing Standards
2.1. Wi-Fi (IEEE standard 802.11)
2.1.1. Standards
2.1.2. Network Types
2.2. Bluetooth (IEEE standard 802.15.1)
2.3. ZigBee (IEEE standard 802.15.4)
3. Intoduction to ZigBee
3.1. The ZigBee Alliance
3.2. The Name ZigBee
3.3. Why ZigBee
3.4. IEEE 802.15.4
3.5. Components of IEEE 802.15.4
4. ZigBee/IEEE 802.15.4 “ General Characteristics
4.1. ZigBee/IEEE 802.15.4 “ Typical Traffic Types Addressed
5. ZigBee Protocol Stack
5.1. The Physical Layer (PHY)
5.2. Media Access Layer (MAC)
5.2.1. Frame Structure
5.2.2. Super Frame Structure
5.3. Network and Security Layer
5.4. Application Layer
5.4.1. ZigBee Device Object
5.4.2. Application Support Layer
6. ZigBee Security
7. ZigBee Applications
8. Conclusion
9. Bibliography
29 Page 4

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
It was in 1896 that Guglielmo Marconi invented the first wireless telegraph. In 1901 he sent
telegraphic signals across the Atlantic ocean from Cornwall to St. Johnâ„¢s Newfoundland; a distance
of 1800 miles. Over the last century, advances in wireless technologies have led to the radio, the
television, the mobile telephone, and communication satellites. All type of information can now be
send to any corner of the world.
A wireless network is a flexible data communication system, which uses wireless media such as
radio frequency technology to transmit and receive data over the air, minimizing the need for wired
connections. Wireless networks are used to augment rather than replace wired networks and are
most commonly used to provide last few stages of connectivity between a mobile user and a wired
Wireless networks use electromagnetic waves to communicate information from one point to
another without relying on any physical connection. Radio waves are often referred to as radio
carriers because they simply perform the function of delivering energy to a remote receiver. The
data being transmitted is superimposed on the radio carrier so that it can be accurately extracted at
the receiving end. Once data is superimposed (modulated) onto the radio carrier, the radio signal
occupies more than a single frequency, since the frequency or bit rate of the modulating information
adds to the carrier. Multiple radio carriers can exist in the same space at the same time without
interfering with each other if the radio waves are transmitted on different radio frequencies. To
extract data, a radio receiver tunes in one radio frequency while rejecting all other frequencies. The
modulated signal thus received is then demodulated and the data is extracted from the signal.
Wireless networks offer the following productivity, convenience, and cost advantages over
traditional wired networks:
Mobility: provide mobile users with access to real-time information so that they can roam
around in the network without getting disconnected from the network. This mobility
supports productivity and service opportunities not possible with wired networks. Page 5

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
Installation speed and simplicity: installing a wireless system can be fast and easy and can
eliminate the need to pull cable through walls and ceilings.
Reach of network: the network can be extended to places which can not be wired
More Flexibility: wireless networks offer more flexibility and adapt easily to changes in the
configuration of the network.
Reduced cost of ownership: while the initial investment required for wireless network
hardware can be higher than the cost of wired network hardware, overall installation
expenses and life-cycle costs can be significantly lower in dynamic environments.
Scalability: wireless systems can be configured in a variety of topologies to meet the needs
of specific applications and installations. Configurations can be easily changed and range
from peer-to-peer networks suitable for a small number of users to large infrastructure
networks that enable roaming over a broad area.
2. Existing Standards
In the world of wireless communication there are many standards existing today, each with a
specific application field and characteristics which best suites the need. However among so many
standard we will only discuss about Wi-Fi, Bluetooth and ZigBee as they are the most
complementary standards among all.
2.1.Wi-Fi (IEEE standard 802.11)
Wi-Fi is the wireless way to handle networking. It is also known as 802.11 networking and wireless
networking. The big advantage of Wi-Fi is its simplicity. Mobile connectivity for computers is a
rapidly growing requirement. Of the schemes that are available the IEEE 802.11 standard, often
termed Wi-Fi has become the de-facto standard. With peak operating speeds of around 54 Mbps it is
able to compete with many wired systems. As a result of the flexibility and performance of the
system, many Wi-Fi hotpots have been set up and more are following. These enabvle people to
use their laptop computers as they wait in hotels, airport lounges, cafes, and many other places using
a wire less link rather that needing to use a cable. Page 6

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
2.1.1. Standards
There is a plethora of standards under the IEEE 802 LMSC (LAN / MAN Standard Committee). Of
these even 802.11 has variety of standards, each with a letter suffix. These cover everything from
the wireless standards themselves, to standards for security aspects, quality of service and the like:
802.11a “ Wireless network bearer operating in the 5 GHz. ISM band with data rate up to 54 Mbps.
802.11b “ Wireless network bearer operating in the 2.4 GHz ISM band with data rates up to 11
802.11e “ Quality of service and prioritization
802.11f “ Handover
802.11g “ Wireless network bearer operating in 24.GHz ISM band with data rates up to 54 Mbps
802.11h “ Power control
802.11i “ Authentication and encryption
802.11j “ Internetworking
802.11k “ Measurement reporting
802.11n “ stream multiplexing
802.11s “ Mesh networking
Of these the standards that are most widely known are the network bearer standards, 802.11a,
802.11b, 802.11g.
2.1.2 Network types
There are two types of network that can be formed: infrastructure networks; and ad-hoc networks.
The infrastructure application is aimed at office areas or to provide a hotspot. It can be installed
instead of a wired system, and can provide considerable cost savings, especially when used in
established offices. A backbone wired network is still required and is connected to a server. ThePage 7

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
wireless network is then split up into a number of cells, each serviced by a base station or Access
Point (AP) which acts as a controller for the cell. Each Access Point may have a range of between
30 and 300 metres dependent upon the environment and the location of the Access Point.
The other type of network that may be used is termed as Ad-Hoc network. These are formed when a
number of computers and peripherals are brought together. They may be needed when several
people come together and need to share data or if they need to access a printer without the need for
having to use wire connections.
In this situation the user4s may only communicate with each other and not a larger wired network.
As a result there is no Access Point and special algorithms within the protocols are used to enable
one of the peripherals to take over the role of master to control the network with the others acting as
2.2. Bluetooth
Bluetooth is based on IEEE standards 802.15.1. Bluetooth has now established itself in the market
place enabling a variety of devices to be connected together using wireless technology. Bluetooth
technology has come into its own connecting remote headsets to mobile phones, but it is also used in
a huge number of other applications as well.
Bluetooth technology originated in 1994 when Erricsson came up with a concept to use a wireless
connection to connect items such as an earphone and a cordless headset and the mobile phone.
The name of the Bluetooth standard originates from the Danish king Harald Blatand who was king
of Denmark between 940 and 981 AD. His name translates as Bluetooth and this was used as his
nickname. A brave warrior, his main achievement was that of uniting Denmark under the banner of
Christianity, and then uniting it with Norway that he had conquered. The Bluetooth standard was
named after him because Bluetooth endeavors to unite personal computing and telecommunications
devices. Page 8

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
Bluetooth is a wireless data system and can carry data at speeds up to 721 Kbps in its basic form and
in addition to this it offers up to three voice channels. Bluetooth technology enables a user to
replace cables between devices such as printers, fax machines, desktop computers and peripherals,
and a host of other digital devices. Furthermore, it can provide a connection between an ad-hoc
wireless network and existing wired data networks.
The technology is intended to be placed in a low cost module that can be easily incorporated into
electronics devices of all sorts. Bluetooth uses the license free Industrial, Scientific and
Medical(ISM) frequency band for its radio signals and enables communications to be established
between devices up to a maximum distance of 100 metres. Running in the 2.4 GHz ISM band,
Bluetooth employs frequency hopping techniques with the carrier modulated using Gaussian
Frequency Shift Keying (GFSK).
After a network connection is established between two devices they change their frequency 1600
times per second thus leaving no time for interference, and if by chance there is interference it will
be for few microseconds. No other sub network will be working at the frequency at which other sub
networks work, thus eliminating interference.
2.3. ZigBee
ZigBee is a wireless networking standard that is aimed at remote control and sensor applications
which is suitable for operation in harsh radio environments and in isolated locations, It builds on
IEEE standard 802.15.4 which defines the physical and MAC layers. Above this ZigBee defines the
application and security layer specifications enabling interoperability between products from
different manufacturers. In this way ZigBee is a superset of the 802.15.4 specification.
With the applications for remote wireless sensing and control growing rapidly it is estimated that the
market size could reach hundreds of millions of dollars as early as 2007. This makes ZigBee a very
attractive proposition, and one, which warrants the introduction of a focused standard. Page 9

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
3. Introduction to ZigBee
The past few years have witnessed a rapid growth of wireless networking. However, up to now
wireless networking has been mainly focused on high “ speed communications, and relatively long
range applications such as IEEE 802.11 wireless local area network standards. The first well known
standard focusing on low rate wireless personal area networks was BLUETOOTH. However it has
limited capacity for networking of many nodes. There are many wireless monitoring and control
applications in industrial and home environments which require longer battery life, lower data rates
and less complexity than those from existing standards. For such wireless applications, a new
standard called IEEE 802.15.4 has been developed by IEEE. The new standard is also called
3.1 The Zigbee Alliance
The ZigBee standard is organized under the auspices of the ZigBee Alliance. The ZigBee alliance is
an organization of companies working together to define an open global standard for making low
power wireless networks. The intended outcome of ZigBee alliance is to create a specification
defining how to build different network topologies with data security features and interoperable
application profiles. This organization has over 150 members, of which seven have taken on the
status of what they term promoter. These seven companies are Ember, Honeywell, Invensys,
Mitsubishi, Motorola, Philips and Samsung. A big challenge for the alliance is to make the
interoperability to work among different products. To solve this problem, the ZigBee Alliance has
defines profiles, depending on what type of category the product belongs to. For example there is a
profile called home lightning that exactly defines how different brands of home lightning-products
should communicate with each other. Under the umbrella of the ZigBee Alliance, the new standard
will be pushed forward, taking on board the requirements of the users, manufacturers and the system
The Alliance has specified three profiles:Page 10

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
Private Profile: In this profile interoperability is not at all important. However producers
cannot use the official ZigBee stamp, but can claim that Ëœbased on ZigBee platformâ„¢.
Published Profile: A private profile is shared among other users. Still one cannot use official
ZigBee stamp, but can claim Ëœbased on ZigBee platformâ„¢.
Public profile: It is the official ZigBee profile.
3.2. The Name ZigBee
The name ZigBee is said to come from the domestic honeybee which uses a zig-zag type of dance to
communicate important information to other hive members. This communication dance (The
ZigBee Principle) is what engineers are trying to emulate with this protocol “ a bunch of separate
and simple organisms that join together to tackle complex tasks.
3.3 Why ZigBee?
There are a multitude of standards like Bluetooth and Wi-Fi that address mid to heigh data rates for
voice, PC LANs, video etc. However, up till now there hasnâ„¢t been a wireless network standard that
meets the unique needs of sensors and control devices. Sensors and controls donâ„¢t need high
bandwidth but they do need low latency and very low energy consumption for long battery lives and
for large device arrays.
There are a multitude of proprietary wireless systems manufactured today to solve a multitude of
problems that donâ„¢t require high data rates but do require low cost and very low current drain. These
proprietary systems were designed because there were no standards that met their application
requirements. These legacy systems are creating significant interoperability problems with each
other and with newer technologies.
The ZigBee Alliance is not pushing a technology; rather it is providing a standardized base set of
solutions for sensor and control systems. Here are the following points that justify the use of ZigBee
over the existing standards. Page 11

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
Low power consumption, simply implemented: Users expect batteries to last many months to
years! Consider that a typical single-family house has about 6 smoke/CO detectors. If the
batteries for each one only lasted six months, the home owner would be replacing
batteries every month!
In contrast Bluetooth, which has many different modes and states depending upon your
latency and power requirements, ZigBee/IEEE 802.15.4 has two major states:
active(transmit/receive) or sleep. The application software needs to foicus on the
application, not on which power mode is optimum for each aspect of operation.
Even mains powered equipment needs to be conscious of energy. ZigBee devices will be
more ecological than their predecessors saving megawatts at it full deployment. Consider
a future home that has 100 wireless control/sensor devices,
Case 1: 802.11 Rx power is 667 mW (always on) @ 100 devices/home & 50,000
homes/city = 150 3.33 megawatts.
Case 2: 802.15.4 Rx power is 30 mW (always on) @ 100 devices/home & 50,000
homes/city = 150 kilowatts.
Case 3: 802.15.4 power cycled at .1% (typical duty cycle) = 150 watts
Low cost to the users means low device cost, low installation cost and low maintenance.
ZigBee devices allow batteries to last up to years using primary cells (low cost)
without any chargers (low cost and easy installation). ZigBeeâ„¢s simplicity allows
for inherent configuration and redundancy of network devices provides low
High density of nodes per network: ZigBeeâ„¢s use of the IEEE 802.15.4 PHY and MAC
allows networks to handle any number of devices. This attribute is critical for massive
sensor arrays and control networks.
Simple protocol, global implementation: ZigBeeâ„¢s protocol code stack is estimated to be
about 1/4
of Bluetoothâ„¢s or 802.11â„¢s. Simplicity is essential to cost, interoperability, and
maintenance. The IEEE 802.15.4 PHY adopted by ZigBee has been designed for the 868 Page 12

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
MHz band in Europe, the 915 MHz band in N America, Australia, etc; and the 2.4 GHz
band is now recognized to be a global band accepted in almost all countries.
3.4 IEEE 802.15.4
IEEE 802.15 is the working group 15 of the IEEE 802 which specializes in Wireless PAN standards.
It includes four task groups (numbered from 1 to 4):
Task group 1 (WPAM/Bluetooth) deals with Bluetooth, having produced the 802.15.1
standard, published on June 14, 2002. It includes a medium access control and physical
layer specification adapted from Bluetooth 1.1.
Task group 2 (coexistence) deals with coexistence of Wireless LAN (802.11) and Wireless
Task group 3 is in fact two groups: 3 (WPAN High Rate) and 3a (WPAN Alternate Higher
Rate), both dealing with high-rate WPAN standards (20 Mbit/s or higher).
Task group 4 (WPAN Low Rate) deals with low rate but very long battery life (months or
even years). The first edition of the 802.15.4 standard was released in May 2003. In
March 2004, after forming Task Group 4b, task group 4 put itself in hibernation.
The new Task Group 4b aims at clarifying and enhancing specific parts of the Task Group 4
3.5 Components of IEEE 802.15.4
IEEE 902.15.4 networks use three types of devices.
The network coordinator maintains the overall network knowledge. It is the most
sophisticated one of the three types and required the most memory and computing power. Page 13

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
The Full Function Device (FFD) supports all IEEE 802.15.4 functions and features specified
by the standard. It can function as a network coordinator. Additional memory and
computing power make it ideal for network router functions or it could be used in
network-edge devices (where the network touches the real world).
The Reduced Function Device (RFD) carries limited (as specified by the standard)
functionality to lower cost and complexity. It us generally found in network-edge
4. ZigBee/IEEE 802.15.4 “ General Characteristics
Data rates of 250 kbps (@2.4 GHz), 40 Kbps (@ 915 MHz) and 20 kbps (@868 MHz)
Optimized for low duty-cycle applications (<0.1%).
Low power (battery life multi-month to years).
Multiple topologies: star, peer-to-peer, mesh.
CSMA-CA channel access yields high throughput and low latency for low duty cycle devices
like sensors and controls.
Addressing space of 64 bits “ 18,450,000,000,000,000,000 devices (64 bit IEEE address) “
65,535 networks.
Optional guaranteed time slot for applications requiring low latency.
Fully hand-shaked protocol for transfer reliability
Range: 50m typical (5-500m based on environment).
4.1 ZigBee/IEEE 802.15.4 “ Typical Traffic types Addressed
Following are typical traffic types specified:
Periodic dataPage 14

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
Application defined rate (e.g. sensors)
Intermittent data
Application/external stimulus defined rate (e.g. light switch)
Repetitive low latency data
Allocation of time slots(e.g. mouse)
Each of these traffic types mandates different attributes from the MAC. The IEEE 802.15.4 MAC is
flexible enough to handle each of these types.
Periodic data can be handled using the beaconing system whereby the sensor will wake up for
the beacon, check for any messages and then go back to sleep.
Intermittent data can be handled either in a beaconless system or in a disconnected fashion.
In a disconnected operation the device will only attach to the network when it needs to
communicate saving significant energy.
Low latency applications may choose to the guaranteed time slot (GTS) option. GTS is a
method of QoS (Quality of Service) in that it allows each device a specific duration of
time each Superframe to do whatever it wishes to do without contention or latencyPage 15

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
5. ZigBee Protocol Stack
The ZigBee protofol stack is 1/4
of that of Wi-Fi and Bluetooth. It may be helpful to think of IEEE
802.15.4 as the physical radio and ZigBee as the logical network and application software.
Following the standard Open Systems Intenconnection (OSI) reference model, ZigBeeâ„¢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 as shown in the figure Ëœfig 5.1â„¢. The layers above them are
defined by the ZigBee Alliance. The IEEE working group passed the first draft of PHY and MAC in
Fig 5.1 ZigBeeâ„¢s Protocol Stack
ZigBee or OEM
AlliancePage 16

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
5.1 The Physical Layer (PHY)
ZigBee-compliant products operate in unlicensed bands worldwide, including 2.4 GHz (global), 902
to 928 MHz. (America) and 868 MHz (Europe). Raw data throughput rates of 250Kbps can be
achieved at 2.4 GHz (16 channels), 40 Kbps at 915 MHz (10 channels), and 20 Kbps at 868 MHz (1
channel). 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 2.4 GHz band, with offset-quadrature phase shift keying modulation. Channel width is 2 MHz
with 5 MHz channel spacing. The 868 and 900 MHz bands also use direct-sequence spread
spectrum but with binary-phases shift keying modulation.
868/915 MHz Band Modulation
The transmitter must be capable of transmitting atleast “3dbm although this should be reduced when
possible to reduce interference to other users. The maximum allowable power will depend on local
regulatory bodies. The receiver must have a packet error rate of <1% for input signals at the antenna
connector of >-92dBm.
2450 MHz Band Modulation
The transmitter must be capable of transmitting at least “3dBm although this should be reduced
when possible to reduce interference to other users. The maximum allowable power will depend on
local regulations.
What is Direct Sequence Spread Spectrum (DSSS)?
In direct Sequence Spread Spectrum a bit is assigned a particular code spectrum that is transmitted
and on the destination node that code is replaced by that specific bit, this way assigning the code
spectrum utilizes bandwidth efficiently. Page 17

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Department of Computer Science, CUSAT
The fig 5.2. shows the operating frequencies offered by the physical layer of ZigBee protocol. The
phusical also specifies other parameters for transmission such as device types that are used.
Speading Parameters
Data Parameters
Numbering Chip Rate Modulation Bit Rate
868 to 870
20 Kb/s 20 Kbaud
868 to
902 to 928
1 to 10
40 Kb/s 40 Kbaud
2.4 GHz
2.4 to 2.4835
11 to 26
62.5 Kbaud
Fig 5.2 Table showing ZigBeeâ„¢s operating frequency and modulation technologies used
Tow types of devices are defined: Full Function Device (FFD) and Reduced Function Device
(RFD). An FFD can serve as a coordinator or a regular device. It can communicate with any other
devices within its transmission range. An RFD is a simple device that associates and communicates
only with an FFD, The IEEE 802.15.4 PHY layer provides a parameter, Link Quality Indivation
(LQI), to characterize the quality of received signal. It can be the received power, the estimated
signal-to-noise-ration (SNR), or a combination of both. LQI is passed to MAC layer and finally
available to the network and upper layers. Other futures of PHY layer include the activation and
deactivation of the radio transceiver, channel selection, clear channel assessment, and
transmitting/receiving packets across physical medium.
5.2 Media Access Layer (MAC)
There are two channel access mechanisms used by MAC Layer:
Non-Beacon mode
Beacon mode
ZigBee networks can use beacon or non-beacon environments. Beacons are used to synchronize the
network devices, identify the PAN and describe the structure of the superframe. The beacon Page 18

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Department of Computer Science, CUSAT
intervals are set by the network coordinator and vary from 15ms to over 4 minutes. Sixteen equal
time slots are allocated between beacons are message delivery. The channel access in each time slot
is contention-based. However, the network coordinator can dedicate up to seven guaranteed time
slots for non contention based or low-latency delivery.
The non-beacon mode is a simple, traditional multiple-access system used in simple peer and near-
pear networks. It operates like a two-way radio network, where each client is autonomous and can
initiate a conversation at will, but could interfere with others unintentionally. The recipient may not
here the call or the channel might already be in use
Beacon Mode is a mechanism for controlling power consumption in extended networks such as
cluster tree or mesh. It enables all the clients to know when to communicate with each other. Here,
the two-way radio network has a central dispatcher that manages the channel and arranges the calls.
The primary value of beacon mode is that it reduces the systemâ„¢s power consumption
Non-beacon mode is typically used for security systems where client units, such as intrusion sensors,
motion detectors, and glass-break detectors, sleep 99.999% of the time.
Remote units wake up on a regular, yet random, basis to announce their continued presence in the
network. When an event occurs, the sensor wakes up instantly and transmits the alert (Somebody is
on the front porch). The network coordinator, powered from the main source, has its receiver on all
the time and can therefore wait to hear from each of these stations. Since the network coordinator
has an infinite source of power it can allow clients to sleep for unlimited periods of time, enabling
them to save power.
Beacon mode is more suitable when the network coordinator is battery-operated. Client units listen
for the network coordinatorâ„¢s beacon (broadcast at intervals between 0.015 and 252 s). A client
registers with the coordinator and looks for any messages directed to it. If no messages are pending,
the client returns to sleep, awaking on a schedule specified by the coordinator. Once the client
communications are completed, the coordinator itself returns to sleep. Page 19

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This timing requirement may have an impact on the cost of the timing circuit in each end device.
Longer intervals of sleep mean that the timer must be more accurate or turn on earlier to make sure
that the beacon is heard, both of which will increase receiver power consumption. Longer sleep
intervals also mean the timer must improve the quality of the timing oscillator circuit (which
increases cost) or control the maximum period of time between because to not exceed 252s, keeping
oscillator circuit costs low.
5.2.1 Frame Structure
The frame structures have been designed to keep the complexity to minimum while at the same time
making them sufficiently robust for transmission on a noisy channel. Each successive protocol layer
adds to the structure with layer-specific headers and footers.
The IEEE 802.15.4 MAC defines four frame structures:
A beacon frame, used by a coordinator to transmit beacons. The beacon frame wakes up
client devices, which listen for their address and go back to sleep if they donâ„¢t receive it.
Beacons are important for mesh and cluster-tree networks to keep all the nodes
synchronized without requiring those nodes to consume precious battery energy by
listening for long periods of time.
A data frame, used for all transfers of data. The data frame provides a payload of up to 104
bytes. The frame is numbered 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. This frame is shouwn in fig. 5.3.
An acknowledgment frame, used for confirming successful frame reception 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, used for handling all MAC peer entity control transfers. A Mac
command frame provides the mechanism for remote control and configuration of clientPage 20

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nodes. A centralized network manager uses MAC to configure individual clientsâ„¢
command frames no matter how large the network
The data frame is illustrated below in fig 5.3:
Fig 5.3 ZigBeeâ„¢s Data Frame
The Physical Protocol Data Unit is the total information sent over the air. As shown in the
illustration above the Physical layer adds the following overhead:
Preamble sequence
4 Octets
Start of Frame Delimiter
1 Octet
Frame Length
1 Octet
The MAC adds the following overhead:
Frame control
2 Octets
Data Sequence Number
1 Octet
Address Information
4 to 20 OctetsPage 21

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Department of Computer Science, CUSAT
Frame Check Sequence
2 Octets
The total overhead for a single packet is therefore 15 “ 31 octets (120 bits); depending upon the
addressing scheme used (short or 64 bit addresses). These numbers do not include any security
5.2.2 Super Frame Structure
The LR-WPAN standard allows the optional use of a superframe structure. The format of the
superframe is defined by the coordinator. The superframe is bounded by network beacons, is sent by
the coordinator and is divided into 16 equally sized slots as shown in fig 5.4. The beacons are used
to synchronize the attached devices, to identify the PAN and to describe the structure of the
superframes. Any device wishin to communicate during the contention access period (CAP)
between two beacons shall compete with other devices using a slotted CSMA-CA mechanism. All
transactions shall be completed by the time of the next network beacon.
Fig. 5.4 ZigBeeâ„¢s super frame structure bounded by two beacons
For the low latency applications or applications requiring specific data bandwidth, the PAN
coordinator may dedicate portions of the active superframe to that application. These portions are
called guaranteed time slots (GTSs). The guaranteed time slots comprise the contention free period
(CFP), which always appears at the end of the active superframe starting at a slot boundaryPage 22

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immediately following the CAP, as shown in fig. 5.5. the PAN coordinator may allocate up to seven
of these GTSs and a GTS may occupy more than one slot period. However, a sufficient portion of
the CAO shall remain for contention-based access of other networked devices or new devices
wishing to join the network. All contention-based transactions shall be complete before the CFP
begins. Also each device transmitting in a GTS shall ensure that its transaction is complete before
the time of the next GTS or the end of the CFP.
Fig. 5.5 ZigBeeâ„¢s superframe structure with contention access and free period
5.3 Network and Security Layer (NWK)
The NWK layer associates or dissociates devices using the network coordinator implements security,
and routes frames to their intended destination. In addition, the NWK layer of the network
coordinator is responsible for starting a new network and assigning an address to newly associated
The NWK layer supports multiple network topologies including star, cluster tree, and mesh as
shown in fig 5.6 and fig 5.7. In a star topology, one of the FFD-type devices assumes the role of
network coordinator and is responsible for initiating and maintaining the devices on the network.
All other devices, known as end devices, directly communicate with the coordinator. Page 23

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Department of Computer Science, CUSAT
Fig. 5.6 Star and pear-to-pear network topology
In a mesh topology, the ZigBee coordinator is responsible for starting the network and for choosing
key network parameters, but the network may be extended through the use of ZigBee routers. The
routing algorithm uses a request-response protocol to eliminate sub-optimal routing. Ultimate
network size can reach 264 nodes (more than weâ„¢ll probably need). Using local addressing, you can
configure simple networks of more than 65,000 (2
) nodes, thereby reducing address overhead. Page 24

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Department of Computer Science, CUSAT
Pan Coordinator
Cluster Head
Fig 5.7 Cluster tree topology
5.4 Application Layer.
The ZigBee application layer consists of the APS sub-layer, the ZDO and the manufacturer-defined
application objects. The responsibilities of the APS sub-layer include maintaining tables for
binding, which is the ability to match two devices together based on their services and their needs,
and forwarding messages between bound devices. Another responsibility of the APS sub-layer is
discovery, which is the ability to determine which responsibilities of the ZDO include defining the
role of the device within the network (e.g. ZigBee coordinator or end device), initiating and/or
responding to binding requests and establishing a secure relationship between network devices. The
manufacturer-defined application objects implement the actual applications according to the ZigBee-
defined application descriptions. Page 25

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Department of Computer Science, CUSAT
5.4.1 ZigBee Device Object
Defines the role of the device within the network (e.g. ZigBee coordinator or end device)
Initiates and/or responds to binding requests
Establishes a secure relationship between network devices selecting one of ZigBeeâ„¢s security
methods such as public key, symmetric key etc.
5.4.2 Application Support Layer
This layer provides the following services:
Discovery: The ability to determine which other devices are operating in the personal operating
space of a device.
Binding: The ability to match two or more devices together based on their services and their needs
and forwarding messages between bound devices.
The General Operation Framework (GOF) is a glue layer between applications and rest of the
protocol stack. The GOF currently covers various elements that are common for all devices. It
includes sub-addressing and addressing modes and device descriptions, such as type of device,
power source, sleep modes, and coordinators using an object model, the GOF specifies methods,
events, and data formats that are used by application profiles to construct set/get commands and their
Actual application profiles are defined in the individual profiles of the IEEEâ„¢s working groups.
Each ZigBee device can support up to 30 different profiles. Currently, only one profile, Commercial
and Residential Lighting, is defined. It includes switching and dimming load controllers,
corresponding remote-control devices, and occupancy and light sensors.
6. ZigBee Security
When security of MAC layer frames is desired, ZigBee uses MAC layer security to secure MAC
command, beacon, and acknowledgment frame. ZigBee may secure messages transmitted overPage 26

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Department of Computer Science, CUSAT
single hop using secured MAC data frames, but for multi-hop messaging ZigBee relies upon upper
layers (such as the NWK layer) for security. The MAC layer uses the Advanced Encryption
Standard (AES) as its core cryptographic algorithm and describes a variety of security suites that use
the AES algorithm. These suites can protect the confidentiality, integrity, and authenticity of MAC
frames. The MAC layer does the security processing, but the upper layers, which set up the keys
and determine the security levels to use, control this processing. When the MAC layer transmits
(receives) a frame with security enabled, it looks at the destination (source) of the frame, retrieves
the key associated with that destination (source), and then uses this key to process the frame
according to the security suite designated for the key being used. Each key is associated with a
single security suite and the MAC frame header has a bit that specifies whether security for a frame
is enabled or disabled.
7. ZigBee Applications
The ZigBee Alliance targets applications Across consumer, commercial, industrial and government
markets worldwide. Unwired applications are highly sought after in many networks that are
characterized by numerous nodes consuming minimum power and enjoying long battery lives.
ZigBee technology is designed to best suit these applications, for the reason that it enables reduced
costs of development, very fast market adoption and rapid ROI..
For the last few years, we have witnessed a great expansion of remote control devices in our day-to-
day life. Five years ago, infrared (IR) remotes for the television were the only such devices in our
homes. Now the number of devices is uncountable. This number will only increase as more devices
are controlled or monitored from a distance. To interact with all these remotely controlled devices,
we will need to put them under a single standardized control interface that can interconnect into a
network, specifically a HAN or home-area network.
ZigBee applications can be divided into the following groups.
Home networking
Industrial control and management
Human and computer interfacePage 27

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Department of Computer Science, CUSAT
Smart dust
Intrusion sensors, motion detectors and glass break detectors.
The Home is receiving a lot of attention lately as the place that could do with a lot of new
technology. Some of it seems like wishful thinking. Ideas that we want to connect all our electronic
devices at home “ from PCs, stereos, TV and DVD players to the security system, all utility meters,
microwave oven, fridge and even toaster “ to a single home network that is then connected to the
internet does not stand up to much scrutiny at this time. Why would we all want to do that?
In fact, the home networking market appears to be fragmented into four different application areas:
PC networking, connecting two or more PCs to a single broadband connection to the Internet
as well as printers and other resources that can be shared.
Home entertainment distribution, sharing content among televisions, stereos, and game
consoles around the home.
Home control, where one group of applications offers electronic control of heating, lighting
and security systems.
Home appliances, where your fridge can access recipes on the Internet or shop on your
behalf and your washing machine can call a service engineer.
Then there is Microsoftâ„¢s work on SPOT (Smart Personal Object Technology) that seems to be a
way for Microsoft to try to Improve everyday household objects like alarm clocks, key chains ad
Of these, PC networking is clearly in the ascendancy at present, as a direct result of the rollout of
broadband connections to the home. The second typically involves connecting the TC to the Stereo
system, for example, and looks a little less certain as a mass market. It may well pick up steam
though also as a result of broadband connections “transferring those music and video files from the
PC to the home entertainment system perhaps. Page 28

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Department of Computer Science, CUSAT
Industrial automation includes extending existing manufacturing and process control systems
reliably and improve asset management by continuously monitoring critical equipment.
Using ZigBee we can reduce energy costs through optimized manufacturing process and
to identify inefficient operation or poorly performing equipment.
Smart dust an emerging technology can be used for various purposes such as surveillance,
military purposes, weather monitoring and many other things which are still beyond reach.
The goal of the Smart Dust project is to build a self-contained, millimeter-scale sensing and
communication platform for a massively distributed sensor network. This device will be
around the size of a grain of sand and will contain sensors, computational ability, bi-
directional wireless communications, and a power supply, while being inexpensive
enough to deploy by the hundreds. Smart Dust may not be the subject matter of science
fiction any longer “ the advent of ZigBee and other wireless protocols suitable for sensor
networks is pushing the technology to the next level. Page 29

ZigBee: Next Generation Wireless Network
Department of Computer Science, CUSAT
8. Conclusion
Bluetooth has already matured and graduated to version 1.2 after its initial hype. Lots of products
compliant to Bluetooth version 1.1 are available on the market. Will ZigBee be able to compete
with Bluetooth in the market? And if yes, will it replace Bluetooth? This question is asked by the
people where since ZigBee came to the market. We have already seen all the aspects of both
ZigBee and Bluetooth. And hence can be concluded that ZigBee and Bluetooth are two solutions for
two different application areas. The differences are from their approach to their desired application.
Bluetooth has addressed a voice application by embodying a fast frequency hopping system with a
master slave protocol. ZigBee has addressed sensors, controls, and other short message applications
by embodying a direct sequence system with a star or peer-to-peer protocols. Minorchanges to
Bluetooth or ZigBee wonâ„¢t change their inherent behaviour or characteristics. The different
behaviours come from architectural differences. Page 30

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9. Bibliography
Behrouz A. Frouzan, Data Communication, Third Edition, Tata McGraw-Hill Publishing
company Limitted, 2004
Andrew S. Tenenbaum, Computer Networks, Fourth Edition Pearson Publication
Limited, 2003
William Stalling, Wireless Communication and Networks, Fourth Edition, Pearson
Publication Limited, 2004
James Kurose & Keith W. Ross, Computer Networks, Fourth Edition, Pearson
Publication Limited, 2

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RE: Seminar Report On ZigBee: Next Generation Wireless Network

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Presented By:




Zig bee is a ad-hoc networking technology for LR-WPAN

It provides a high data throughput in applications
where the duty cycle is low


Intended for 2.45GHZ , 868MHZ and 915Mhz band

Data rates touch 250kbps , 40kbps and 20kbps

Low cost , power consumption as compared to
competing technologies













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1. Introduction
ZigBee is a communication standard that provides a short-range coast effective networking capability. It has bee developed with the emphasis on low-coast battery powered application such as building automation industrial and commercial control etc. Zigbee has been introduced by the IEEE and the zigbee alliance to provide a first general standard for these applications. The IEEE is the Institute of Electrical and Electronics Engineers. They are 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, which is also known as Bluetooth.
The name "ZigBee" is derived from the erratic zigging patterns many bees make between flowers when collecting pollen. This is evocative of the invisible webs of connections existing in a fully wireless environment. 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 250Kbps, compared to Bluetoothâ„¢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 sixty ZigBee devices may be found in an average American home, all communicating with one another freely and regulating common tasks seamlessly.
2. What is wireless technology
Wireless networks are becoming more pervasive, accelerated by new wireless communications technologies, inexpensive wireless equipment, and broader Internet access availability. These networks are transforming the way people use computers and other personal electronics devices at work, home, and when traveling.
There are many wireless communications technologies that can be differentiated by frequency, bandwidth, range, and applications. In this white paper, we survey these technologies, which can be broadly organized into the four categories depicted in Figure below. These categories range from wireless wide area networks (WWANs), which cover the widest geographic area, to wireless personal area networks (WPANs), which cover less than 10 meters.
Bluetooth wireless technology is the prevalent WPAN technology today. It operates in the 2.4-GHz unlicensed frequency band. Figure 2 shows its evolution from version 1.1 at a data rate of 1 Mbps to version 1.2, which improves the signaling and frequency band coexistence mechanisms. The 3-Mbps Bluetooth 2.0+ Enhanced Data Rate (EDR) was ratified in November 2004 and products are beginning to appear on the market.
Over the next three years, WPAN applications that require higher data rates may adopt the emerging high bandwidth Ultrawideband (UWB) technology. UWB provides high bandwidth by transmitting at very low power across a broad frequency spectrum. The UWB physical interface (or PHY) specification”802.15.3a” is under development in the IEEE, and a competing specification is under development by an industry working group called the Multi Band Orthogonal Frequency Division Multiplexing (OFDM) Alliance (MBOA). Initial UWB products with data rates of 100-480 Mbps are anticipated in early 2006. Future versions are expected to have data rates of up to 1 Gbps. Failure to resolve the issue of competing standards may stall the market opportunity for UWB technology. In addition, although the U.S. Federal Communications Commission (FCC) has approved a large amount of spectrum for UWB in the U.S., there are regulatory and regional policy issues outside the U.S.
An additional wireless technology that fits roughly in the WPAN category”ZigBee (802.15.4)”is optimized for low-bandwidth niche applications such as instrumentation and home automation. Zigbee is not depicted in Figure 2 because it is unlikely that it will be deployed outside these specialized applications.
Wireless Local Area Networks
In contrast to WPANs, WLANs provide robust wireless network connectivity over a local area of approximately100 meters between the access point and associated clients. Today's WLANs are based on the IEEE 802.11 standard and are referred to as Wi-Fi networks. 802.11b was the first commercially successful WLAN technology. It operates in the 2.4-GHz frequency band at 11Mbps. By implementing a different data transmission method, data rates were increased to 54 Mbps in 2003with 802.11g in the 2.4-GHz band and 802.11a in the 5-Ghz band. Today, dual-band Wi-Fi access points and client network adapters that support various combinations of 802.11a, b, and g are common. Highly integrated, single-chip solutions that are smaller and require less power have enabled new designs and applications.
In addition, new standards address Wi-Fi network security. Wi-Fi Protected Access (WPA) and 802.11i (or WPA2) focus on user authentication and encryption. WPA2 employs next-generation Advanced Encryption Security (AES) encryption. A component of WPA and WPA2”the IEEE 802.1X standard”provides a port-level authentication framework. Finally, the upcoming 802.11e standard addresses quality of service (QoS). QoS enables the prioritization of latency-sensitive applications such as voice and multimedia. The Wi-Fi Alliance, an industry group responsible for certification and interoperability testing, has developed the Wi-Fi Multi- media (WMM) test specification to certify product compliance with the 802.11e standard.
The next-generation WLAN standard is IEEE 802.11n, which is currently being defined. 802.11n will be backward-compatible with 802.11a, b, and g, and will provide data rates in excess of 100 Mbps. The 802.11n performance increases stem from new Multiple-Input, Multiple-Output (MIMO) radio technology, wider radio frequency (RF) channels, and improvements to the protocol stack. MIMO enables higher data rates by increasing the number of radios and antennas in a wireless device. 802.11n is scheduled for IEEE ratification in mid-2006. Dell is leading an initiative in the Wi-Fi Alliance to launch a product certification program concurrent with ratification of the IEEE 802.11n standard.
Wireless Metro Area Networks
A WMAN is a wireless communications network that covers a large geographic area such as a city or suburb. Traditionally, long-distance wireless technologies providing T1 or T3 data rates have been proprietary owned and operated by major telephone companies, in dependent local exchange carriers (ILECs), and other providers to link remote sites or large campuses. The IEEE has standardized a new set of WMAN technologies that operate in licensed and license exempt frequency bands. The best known of these technologies” IEEE 802.16d or WiMax”will operate in the 2- to11-GHz frequency range. (In the U.S., it will operate in the 2.5-, 3.5-, and 5.8-GHz frequency bands.) Its maximum data rate when operated within line of sight and under ideal conditions is 70 Mbps over 50 kilometers. Initial deployments will require an external antenna at the customer premises. A mobile version”802.16e”is planned in 2007. It is not yet clear when (or whether) telecommunications and Internet service providers will broadly deploy the required infrastructure to support either the fixed or mobile versions of Wi-Max. However, it is widely expected that WiMax deployments will lever age existing and emerging tower infrastructures and installations.
Wireless Wide Area Networks
WWANs are digital cellular networks used for mobile phone and data service and operated by carriers such as Cingular Wireless, Vodafone, and Verizon Wireless WWANs provide connectivity over a wide geographical area, but, until recently, data rates have been relatively low”115 Kbps”compared to other more localized wireless technologies.
Two WWAN technologies Global System for Mobile Communications (GSM) and Code Division Multiple Access (CDMA)”dominate WWAN deployments worldwide. These two technologies are expected to evolve on parallel paths for the foreseeable standardized early on GSM. Today, GSM and its associated wireless data capability, General Packet Radio Service (GPRS) and next-generation Enhanced Data GSM Evolution (EDGE), have about two thirds of the worldwide market. These technologies have been deployed in North America, Europe, and Asia. Next-generation EDGE boosts GPRS data rates by 3“4 times. Other GSM operators, especially those that have acquired new 3G frequency spectrum, are commercializing Wideband CDMA (WCDMA), which is expected to have data rates of 2 Mbps. An extension called High-Speed Downlink Packet Access (HSDPA) is expected to be deployed starting in 2006. HSDPA will further increase these data rates to 3.6 Mbps and beyond.
CDMA technology dominates in the U.S. The CDMA2000 WWAN technology has seen strong deployments in North America, Japan, Korea, and China. The CDMA2000 single-carrier radio transmission technology (1xRTT) version has been widely deployed. The next-generation 1xEvolution-Data Optimized (1xEV-DO) is currently being aggressively deployed by Verizon Wire- less and Sprint PCS in the U.S. and will support a data rate of 2.4 Mbps. Carriers will build on EV-DO with version A of the specification, which will support even higher data rates and Voice over Internet Protocol (VoIP) calls.
3. Need of zigbee
Wireless sensor networking is one of the most exciting technology markets today. They say that over the next five to ten years, wireless sensors will have a significant impact on almost all major industries as well as our home lives. Broadly, this technology market includes application segments such as automated meter reading, home automation, building automation, container security/tracking, and many others.
Although products that span these application segments are diverse and different in how they operate and what they do, their requirements from a wireless communication technology are very similar. For example, these applications generally require low data rates and are battery powered.
The main motivations for migrating these products to wireless
communications are three-fold:
1. Installation cost “ The cost of running wires in a typical building automation project in an existing facility can be as high as 80% of the total project cost
2. Maintenance “ It is easier to configure a hot-water heater controller with a hand-held remote than a keypad in the closet.
3. New markets “ Eliminating the wire opens new markets that were previously unavailable to wired products.
In the wireless worlds of WiFi and BlueTooth, market growth was fueled by standards development that ultimately brought down the cost of the technology and ensured excellent value to the user. In that spirit, a number of companies forged an alliance to create a wireless standard for the embedded wireless market space, also called personal area networking (PAN); this standard is now called Zigbee. The list of promoting members is prominent and includes names like Honeywell, Phillips, Motorola, Freescale, Invensys, and many others.
Technically, Zigbee is a protocol standard that defines network, security, and application framework protocol software. Zigbee is designed to work on top of the IEEE 802.15.4 PHY/MAC layer standard. The IEEE 802.15.4 standard was ratified in May of 2003; to our knowledge the Zigbee standard is not at the time of this writing ratified, though we understand that it is very close.
4. What is Zigbee / 802.15.4
The IEEE 802.15.4 standard defines the PHY and MAC layers, which are used by Zigbee.
PHY description
Three frequency bands are specified, though an implementation need only operate on one of the three, the bands are:
868 MHz - for European applications
902-928 MHz - for North American applications
2.450 GHz -for world wide application
In all bands, the modulation scheme is direct sequence spread spectrum. In the
868 and 902-928 MHz bands, the transmitter is modulated using BPSK. In the
2.450 GHz band, the transmitter is modulated using offset-QPSK, which is more bandwidth efficient than BPSK.
Direct sequence spread spectrum is a technique that essentially spreads the narrow band of data over a much broader bandwidth by using a pseudo-random chipping sequence. This process provides gain at the receiver because of the correlating effect of de-spreading the data. The amount of gain is determined by the ratio of the chipping rate to the data rate. The higher the ratio, the higher the gain. This gain also provides proportional rejection of on channel interference. As the wanted signal is correlated and de-spread, the interferer is spread, increasing the level of the wanted signal and decreasing the level of the interfering carrier. The amount of rejection is determined by the spreading gain.
In the 2.450 GHz band, an 802.15.4 radio spreads the data using an 8 bit chipping sequence. Actually, the chipping sequence is 32 bits, but the data being spread is actually 4 bits, thus the 8:1 chipping ratio. The process gain in dB is calculated by multiplying ten times the log of the chipping ratio; in this case the gain is 9dB. Receiver sensitivity is specified at “85dBm; adjacent channel rejection is 0dB minimum.
In the 868 and 902-928 MHz band, an 802.15.4 radio spreads the data using a 15 bit chipping sequence. In this case, chipping ratio is 15 and spreading gain is
12dB. Receiver sensitivity is specified at -92dBm; adjacent channel rejection is 0dB minimum.
Zigbee/802.15.4 Specifications by Band
868 MHz 902-928 MHz 2.450 GHz
Data Rate 20 kbps 40 kbps 250kbps
# channels 1 10 16
TX Power -3dBm -3dBm -3dBm
RX Sensitivity -92dBm -92dBm -85dBm
Link Budget 89dB 89dB 82dB
Adjacent channel
channel rejection
0dB 0dB 0dB
30dB 30dB 30dB
MAC Description
The 802.15.4 specification defines a very complicated MAC layer, and I will not attempt to give a detailed explanation here.802.15.4 defines two classes of implementations: full function devices (FFD) and reduced function devices (RFD).
An FFD can operate in three modes serving as a PAN coordinator, a coordinator, or a device. FFDs contain all of the features of 802.15.4 and can talk to both RFDs and FFDs. A PAN coordinator is the primary controller of the network, and it must be a FFD. There can be only one PAN controller per network. A PAN controller is required for an 802.15.4 network. A coordinator is a FFd that provides synchronization Services by transmitting beacons.
A RFD can operate only as a device. RFDs contain a subset of the features of
802.15.4 and are intended to be high-volume, low cost devices. They can be duty-cycled to reduce power consumption. RFD devices can talk only to FFDs. This means that RFDs have no routing capability, so they must be on the perimeters of a mesh network. A device is a simple end-point. A device can be a RFD or FFD. Conceptually, each network would have one FFD that acted as the PAN coordinator and several more FFDs that formed the mesh network. The majority of the nodes in the network would be low-cost RFDs. The number and position of FFDs in the network would determine the coverage of the network.
The illustration on the above shows an example Zigbee network configuration. There is one PAN coordinator, six FFD devices, and nine RFD devices. The actual mesh network is formed by the FFD devices and the PAN coordinator. The RFD devices form a point to multipoint network with FFD devices that are in range Node 8 is not connected to the network. Although it is in range of nodes 7 and 9, it cannot connect to them because all three are RFD devices. An additional FFD device would be required to connect node 8 to the network.
There in lies an inherent limitation of the Zigbee model. The number of FFD devices in the network determines the coverage area; the more FFD devices, the larger the coverage area. It is probable, given the current 802.15.4 specification, that a real-world application of Zigbee would require a high ratio of FFD devices to RFD devices to attain the required coverage, which will adversely affect the pricing model.
This also has implications in system deployment. The primary factor driving the market need is lower installation cost . Using the example just given, it is easy to see how the installation will be complicated. If a device (node 8) is installed in a location that is not in range of an FFD device, it will not be connected to the network. The installer would then be required to place an additional FFD device to serve as an intermediate router. This would have to be done by trial and error, increasing both labor and materials cost.
If this all sounds complicated, that is because it is. The 802.15.4 specification alone consumes 670 printed pages. A typical implementation requires nearly 32K of flash, and that is just for the MAC layer.
The Zigbee specification is likely to be just as large and the software implementation requires another 32K or more of flash memory.
The important aspects of the 802.15.4 standard are listed below :
82-89 dB link budget
0 dB adjacent channel rejection
10 channels @ 900 MHz, 16 channels at 2.450 GHz MHz
40kbps @ 900 MHz, 250 kbps @ 2.450 GHz
RFD devices are not a part of the mesh network
Every network requires a PAN coordinator
The coverage area is determined by both the 802.15.4 link budget and the number of FFD devices deployed
5. Benefits of zigbee
In all of its uses, ZigBee offers four inherent characteristics that are highly beneficial:
Low cost
The typical ZigBee radio is extremely cost-effective. Chipset prices can be as low as $12 each in quantities as few as 100 pieces (while the 802.15.4 and ZigBee stacks are typically included in this cost, crystals and other discrete components are not). Design-in modules fall in the neighborhood of $25 in similar quantities. This pricing provides an economic justification for extending wireless networking to even the simplest of devices.
Range and obstruction issues avoidance:
ZigBee routers double as input devices and repeaters to create a form of mesh network. If two network points are unable to communicate as intended, transmission is dynamically routed from the blocked node to a router with a clear path to the dataâ„¢s destination. This happens automatically, so that communications continue even when a link fails unexpectedly. The use of low-cost routers can also extend the networkâ„¢s effective reach; when the distance between the base station and a remote node exceeds the deviceâ„¢s range, an intermediate node or nodes can relay transmission, eliminating the need for separate repeaters
Multi-source products
As an open standard, ZigBee provides customers with the ability to choose among vendors. ZigBee Alliance working groups define interoperability profiles to which ZigBee-certified devices must adhere, and certified radio will interoperate with any other ZigBee-certified radio adhering to the same profile, promoting compatibility and the associated competition that allows the end users to choose the best device for each particular network node, regardless of manufacturer.
Low power consumption
Basic ZigBee radios operate at 1 mW RF power, and can sleep when not involved in transmission (higher RF power ZigBee radios for applications needing greater range also provide the sleep function). As this makes battery-powered radios more practical than ever, wireless devices are free to be placed without power cable runs in addition to eliminating data cable runs.
6. Technology behind zigbee
IEEE 802.15.4
The IEEE workgroup 802.15.4 has standardized the PHY and MAC, layer within WPAN (Wireless Personal Area Network) area. The primary goal for the working group within IEEE was to define the standard to meet requirements on low complexity, low cost and low power consumption.
802.15.4 MAC
The MAC sublayer provides interfaces towards the PHY and higher (Zigbee) layers. The MAC is responsible for several functions, such as: generation of acknowledgment frames, association, disassociation, security control, and some optional services such as: beacon generation and guaranteed time slot management. One aim when defining the MAC was to make the scheduling engine simple, thus improving the overall power consumption.
Channel Access
For all types of deployed networks the Carrier Sense Multiple Access Collision Avoidance (CSMA-CA) protocol is used. This method is useful to avoid unnecessary collision over the radio channel. CSMA-CA is used for all traffic except beacons, ACK frames and transmissions within a GTS.
Beacon signaling
Only a FFD has the capability of generating beacon frames in a true peer-to-peer network topology there can only be FFDs operating. One exception is when a RFD operates as a peripheral device without routing capability.
Guaranteed Time Slot (GTS)
By using GTS scheduling at the MAC level two important attributes can be achieved over the channel.
Low latency: For specific applications sensitive for delays such as alarms, PC mice, lamp switches or QoS differentiation based on application software. It is possible to reach response times down to 15 msec in GTS mode.
Bandwidth allocation:
Useful for applications that requires to generate a known data traffic rate. The higher layer protocol is responsible for assigning the traffic rate and the MAC level will grant the request.
802.15.4 PHY
The physical layer provides the interface to the wireless medium and is responsible for low-level control for link quality, energy detection, activation/deactivation of the radio transceiver etc. The PHY in 802.15.4 has three different modes of operation depending of geographically region.
The IEEE 802.15.4 PHY uses Direct Sequence Spread Spectrum (DSSS) as the transmission distances ranges from 10-100 meter (approx), depending on output power, radio environment and antenna solution.
Network Topologies
In general there exist three different network topologies:
¢ Star
¢ Cluster Tree
¢ Mesh
In this mode the PAN Coordinator is responsible for updating routing tables, transmit beacons, maintaining synchronization, routing of messages between nodes etc. within the network.
Antenna Considerations
The antenna design is often very crucial for the overall product. One requirement is often to minimize the size of the antenna, which is needed in many embedded applications for short range wireless communications. However, a small antenna may be inefficient unless attention is paid to the design of both the antenna and its placement in the product.
Choice of antenna
There are several design choices in the case of an internal antenna.
The obvious and cheapest choice is to use a substrate antenna, by using a piece of circuit board trace. One disadvantage with this solution is the relative resistive loss and the possible cross interference with components on the board and nearby ground planes.
Another choice is wire antennas where the antenna can be placed away from the board, which improves the performance. One drawback is that this solution may require tuning, due to mechanical differences and size variations. A third choice is to use ceramic antennas which offers smaller physical size than the above mentioned solutions but with a substantially higher cost.
ZigBee Alliance
The ZigBee alliance was founded in order to develop a common standard for Short Range Devices (SRD) with focus on low power consumption, ad-hoc behavior, low latency, self configurable radio nodes. The ZigBee alliance is today an association with over 50 member companies. The main focus within ZigBee is to define the routing mechanisms that together with IEEE802.15.4 will form the total solution.
General Characteristics
¢ Data rates from 20 to 250 kbps
¢ Star Topology/Peer to Peer (mesh)
¢ 255 devices / network
¢ CSMA-CA Access Scheme
¢ Enumeration (new node) ~ 15-30 ms
¢ Dual PHY (868/915 MHz, 2.4 GHz), DSSS
¢ Range: 10-100 m
¢ Low Duty Cycle (< 0 .1%, TX)
¢ Low Power Cons, +1 year battery life time
¢ Complexity: 4 -32 kB (protocol)
7. Applications
Water level sensing
Zigbee can be installed in remote location where conventional GSM modems would be out of their network coverage area, such as inside water tanks. Zigbee transceiver can be hermetically sealed with batteries and co-located with sensors. Each transceiver transmits periodically to another unit installed above ground. A GSM modem transmits the data to base.
In building control
Zigbee-enabled switches and lights can be reduce installation costs in new building by eliminating the need to route light control through the walls, and remove the need to call in qualified electrician when switches need to be relocated. Thermostats and air-conditioning placed anywhere, free of any wiring constraints.
8. Conclusion
The Zigbee solution will be available soon. It will not hit the $10 price point until 2009. The 802.15.4 radio specification has a very poor link budget; 89dB. A Zigbee based solution is not scalable; it will not work reliably with only two end-points separated by the length of a house. It is complicated and requires a significant learning curve from the engineer and significant resources from the protocol controller. The customer must form three supplier relationships; the chip vendor, the software vendor, and the microcontroller vendor.
In addition to cost, reliability, and scalability, Zigbee purports to offer other advantages over proprietary solutions such as Interoperability, Vendor independence and Common platform.
There are three separate frequency bands specified for Zigbee. If one manufacturer of heating controls chooses the 900 MHz band, and another chooses the 2.4 GHz band, the products will not operate together. Additionally, it is likely that IC vendors will add proprietary features to their 802.15.4 implementations in an effort to differentiate their product; if the OEM uses these proprietary features, the benefit of interoperability will be negated. In the end, the only way to guarantee interoperability using Zigbee is to design only 2.4GHz products using only Zigbee standard features.
9. References
Chipcon, CC2420 2.4 GHz IEEE 802.15.4 RF Transceiver Data Sheet
On World, October 2004, Wireless AMR and submetering: A market dynamics study on fixed wireless technologies
Electronic Design, The Zigbee buzz is growing: New low- power wireless standard opens powerful possibilities
On World, Wireless Sensor Networks: Mass Market
IEEE, 802.15.4 Part 15.4: Wireless Medium Access control
(MAC) & Physical (PHY) Layer Specifications for Low Rate Wireless Personal
Area Networks
ZigBee Open House Oslo.htm
Zigbee Alliance -- Home Page.htm
Zigbee Tutorial.htm
please read and for getting more information of zigbee technology

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07-06-2010, 08:17 PM
Post: #4
RE: Seminar Report On ZigBee: Next Generation Wireless Network

.docx  ZIGBEE TECHNOLOGY.docx (Size: 173.46 KB / Downloads: 507)
Y.Naveen kumar
G.Siva kumar
Final year
Electronics And
Communications Engineering
Sir C.R.Reddy College Of



ZigBee is one of the newest technologies enabling Wireless Personal Area
Networks (WPAN). The specification characterized by low data rates and very low
power consumption is revolutionising home networking.
ZigBee is an established set of specifications for wireless personal area
networking (WPAN), i.e. digital radio connections between computers and related
WPAN Low Rate or ZigBee provides specifications for devices that have
low data rates, consume very low power and are thus characterized by long battery life.
ZigBee makes possible completely networked homes where all devices are able to
communicate and be controlled by a single unit.


When you hold the TV remote and wish to use it you have to necessarily
point your control at the device. This one-way, line-of-sight, short-range communication
uses infrared (IR) sensors to enable communication and control and it is possible to
operate the TV remotely only with its control unit.
Add other home theatre modules, an air- conditioner and remotely enabled fans and lights
to your room, and you become a juggler who has to handle not only these remotes, but
also more numbers that will accompany other home appliances you are likely to use.
Now picture a home with entertainment units, security systems including
fire alarm, smoke detector and burglar alarm, air-conditioners and kitchen appliances all
within whispering distance from each other and imagine a single unit that talks with all
the devices, no longer depending on line-of-sight, and traffic no longer being one-way.
This means that the devices and the control unit would all need a common
standard to enable intelligible communication. ZigBee is such a standard for embedded
application software and has been ratified in late 2004 under IEEE 802.15.4 Wireless
Networking Standards.ZigBee is an established set of specifications for wireless personal
area networking (WPAN), i.e., digital radio connections between computers and related
devices. This kind of network eliminates use of physical data buses like USB and
Ethernet cables. The devices could include telephones, hand- held digital assistants,
sensors and controls located within a few meters of each other.
ZigBee is one of the global standards of communication protocol formulated by the
relevant task force under the IEEE 802.15 working group. The fourth in the series,
WPAN Low Rate/ZigBee is the newest and provides specifications for devices that have
low data rates, consume very low power and are thus characterized by long battery life.
Other standards like Bluetooth and IrDA address high data rate applications such as
voice, video and LAN communications.
The ZigBee Alliance has been set up as an association of companies working together to
enable reliable, cost-effective, low-power, wirelessly networked, monitoring and control
products based on an open global standard.Once a manufacturer enrolls in this Alliance
for a fee, he can have access to the standard and implement it in his products in the form
of ZigBee chipsets that would be built into the end devices. Philips, Motorola, Intel, HP
are all members of the Alliance . The goal is to provide the consumer with ultimate
flexibility, mobility, and ease of use by building wireless intelligence and capabilities into
every day devices. ZigBee technology will be embedded in a wide range of products and
applications across consumer, commercial, industrial and government markets
worldwide. For the first time, companies will have a standards-based wireless platform
optimized for the unique needs of remote monitoring and control applications, including
simplicity, reliability, low-cost and low-power.
The target networks encompass a wide range of devices with low data rates in
the Industrial, Scientific and Medical (ISM) radio bands, with building-automation
controls like intruder/fire alarms, thermostats and remote (wireless) switches, video/audio
remote controls likely to be the most popular applications. So far sensor and control
devices have been marketed as proprietary items for want of a standard. With acceptance
and implementation of ZigBee, interoperability will be enabled in multi-purpose, self-
organizing mesh networks


Though WPAN implies a reach of only a few meters, 30 feet in the case of
ZigBee, the network will have several layers, so designed as to enable intrapersonal
communication within the network, connection to a network of higher level and
ultimately an uplink to the Web.
The ZigBee Standard has evolved standardized sets of solutions, called Ëœlayers'.
These layers facilitate the features that make ZigBee very attractive: low cost, easy
implementation, reliable data transfer, short-range operations, very low power
consumption and adequate security features.
1. Network and Application Support layer : The network layer permits growth of
network sans high power transmitters. This layer can handle huge numbers of nodes. This
level in the ZigBee architecture includes the ZigBee Device Object (ZDO), user-defined
application profile(s) and the Application Support (APS) sub- layer.
The APS sub- layer's responsibilities include maintenance of tables that enable matching
between two devices and communication among them, and also discovery, the aspect that
identifies other devices that operate in the operating space of any device.
The responsibility of determining the nature of the device (Coordinator / FFD or RFD) in
the network, commencing and replying to binding requests and ensuring a secure
relationship between devices rests with the ZDO (Zigbee Define Object). The user-
defined application refers to the end device that conforms to the ZigBee Standard.
2. Physical (PHY) layer : The IEEE802.15.4 PHY physical layer accommodates high
levels of integration by using direct sequence to permit simplicity in the analog circuitry
and enable cheaper implementations.
3. Media access control (MAC) layer : The IEEE802.15.4 MAC media access control
layer permits use of several topologies without introducing complexity and is meant to
work with large numbers of devices.
Figure 1: IEEE 802.15.4 / ZigBee Stack Architecture

Device Types:

There are three different ZigBee device types that operate on these layers in any self-
organizing application network. These devices have 64-bit IEEE addresses, with option
to enable shorter addresses to reduce packet size, and work in either of two addressing
modes “ star and peer-to-peer.
1. The ZigBee coordinator node : There is one, and only one, ZigBee coordinator in
each network to act as the router to other networks, and can be likened to the root of a
(network) tree. It is designed to store information about the network.
2. The full function device FFD : The FFD is an intermediary router transmitting data
from other devices. It needs lesser memory than the ZigBee coordinator node, and entails
lesser manufacturing costs. It can operate in all topologies and can act as a coordinator.
3. The reduced function device RFD : This device is just capable of talking in the
network; it cannot relay data from other devices. Requiring even less memory, (no flash,
very little ROM and RAM), an RFD will thus be cheaper than an FFD. This device talks
only to a network coordinator and can be implemented very simply in star topology.

ZigBee Characteristics:

The focus of network applications under the IEEE 802.15.4 / ZigBee standard include the
features of low power consumption, needed for only two major modes (Tx/Rx or Sleep),
high density of nodes per network, low costs and simple implementation.
These features are enabled by the following characteristics
¢ 2.4GHz and 868/915 MHz dual PHY modes. This represents three license- free bands:
2.4-2.4835 GHz, 868-870 MHz and 902-928 MHz. The number of channels allotted to
each frequency band is fixed at sixteen (numbered 11-26), one (numbered 0) and ten
(numbered 1-10) respectively. The higher frequency band is applicable worldwide, and
the lower band in the areas of North America, Europe, Australia and New Zealand .
¢ Low power consumption, with battery life ranging from months to years. Considering
the number of devices with remotes in use at present, it is easy to see that more numbers
of batteries need to be provisioned every so often, entailing regular (as well as timely),
recurring expenditure. In the ZigBee standard, longer battery life is achievable by either
of two means: continuous network connection and slow but sure battery drain, or
intermittent connection and even slower battery drain.
¢ Maximum data rates allowed for each of these frequency bands are fixed as 250 kbps
@2.4 GHz, 40 kbps @ 915 MHz, and 20 kbps @868 MHz.
¢ High throughput and low latency for low duty-cycle applications (<0.1%)
¢ Channel access using Carrier Sense Multiple Access with Collision Avoidance (CSMA
- CA)
¢ Addressing space of up to 64 bit IEEE address devices, 65,535 networks
¢ 50m typical range
¢ Fully reliable hand-shaked data transfer protocol.
¢ Different topologies as illustrated below: star, peer-to-peer, mesh
Figure 2: ZigBee Topologies

Traffic Types:

ZigBee/IEEE 802.15.4 addresses three typical traffic types. IEEE 802.15.4 MAC can
accommodate all the types.
1. Data is periodic. The application dictates the rate, and the sensor activates, checks for
data and deactivates.
2. Data is intermittent. The application, or other stimulus, determines the rate, as in the
case of say smoke detectors. The device needs to connect to the network only when
communication is necessitated. This type enables optimum saving on energy.
3. Data is repetitive, and the rate is fixed a priori. Depending on allotted time slots, called
GTS (guaranteed time slot), devices operate for fixed durations.
ZigBee employs either of two modes, beacon or non-beacon to enable the to-and- fro data
traffic. Beacon mode is used when the coordinator runs on batteries and thus offers
maximum power savings, whereas the non-beacon mode finds favour when the
coordinator is mains-powered.
In the beacon mode, a device watches out for the coordinator's beacon that gets
transmitted at periodically, locks on and looks for messages addressed to it. If message
transmission is complete, the coordinator dictates a schedule for the next beacon so that
the device Ëœgoes to sleep'; in fact, the coordinator itself switches to sleep mode.
While using the beacon mode, all the devices in a mesh network know when to
communicate with each other. In this mode, necessarily, the timing circuits have to be
quite accurate, or wake up sooner to be sure not to miss the beacon. This in turn means an
increase in power consumption by the coordinator's receiver, entailing an optimal
increase in costs.
Figure 3: Beacon Network Communication
The non-beacon mode will be included in a system where devices are Ëœasleep' nearly
always, as in smoke detectors and burglar alarms. The devices wake up and confirm their
continued presence in the network at random intervals.
On detection of activity, the sensors Ëœspring to attention', as it were, and transmit to the
ever-waiting coordinator's receiver (since it is mains-powered). However, there is the
remotest of chances that a sensor finds the channel busy, in which case the receiver
unfortunately would Ëœmiss a call'.
Figure 4: Non-Beacon Network Communication

Network Model:

The functions of the Coordinator, which usually remains in the receptive mode,
encompass network set- up, beacon transmission, node management, storage of node
information and message routing between nodes.
The network node, however, is meant to save energy (and so Ëœsleeps' for long periods)
and its functions include searching for network availability, data transfer, checks for
pending data and queries for data from the coordinator.
Figure 5: ZigBee Network Model
For the sake of simplicity without jeopardising robustness, this particular IEEE standard
defines a quartet frame structure and a super- frame structure used optionally only by the

The four frame structures are

Beacon frame for transmission of beacons
Data frame for all data transfers
Acknowledgement frame for successful frame receipt confirmations
MAC command frame
These frame structures and the coordinator's super- frame structure play critical roles in
security of data and integrity in transmission.
All protocol layers contribute headers and footers to the frame structure, such that the
total overheads for each data packet range are from 15 octets (for short addresses) to 31
octets (for 64-bit addresses).
The coordinator lays down the format for the super- frame for sending beacons after every
15.38 ms or/and multiples thereof, up to 252s. This interval is determined a priori and the
coordinator thus enables sixteen time slots of identical width between beacons so that
channel access is contention- less. Within each time slot, access is contention-based.
Nonetheless, the coordinator provides as many as seven GTS (guaranteed time slots) for
every beacon interval to ensure better quality.

Technology Comparisons:

The Why ZigBee question has always had an implied, but never quite
worded follower phrase ¦when there is Bluetooth. A comparative study of the two can
be found .
The bandwidth of Bluetooth is 1 Mbps, ZigBee's is one- fourth of this
value. The strength of Bluetooth lies in its ability to allow interoperability and
replacement of cables, ZigBee's, of course, is low costs and long battery life.
In terms of protocol stack size, ZigBee's 32 KB is about one-third of the
stack size necessary in other wireless technologies (for limited capability end devices, the
stack size is as low as 4 KB).
Most important in any meaningful comparison are the diverse application
areas of all the different wireless technologies. Bluetooth is meant for such target areas as
wireless USB's, handsets and headsets, whereas ZigBee is meant to cater to the sensors
and remote controls market and other battery operated products.
In a gist, it may be said that they are neither complementary standards
nor competitors, but just essential standards for different targeted applications. The
earlier Bluetooth targets interfaces between PDA and other device (mobile phone / printer
etc) and cordless audio applications.
The IEEE 802.15.4“based ZigBee is designed for remote controls and
sensors, which are very many in number, but need only small data packets and, mainly,
extremely low power consumption for (long) life. Therefore they are naturally different
in their approach to their respective application arenas.

The ZigBee Alliance targets applications "across consumer,
commercial, industrial and government markets worldwide". Unwired applications are
highly sought after in many networks that are characterized by numerous nodes
consuming minimum power and enjoying long battery lives.ZigBee technology is
designed to best suit these applications, for the reason that it enables reduced costs of
development, very fast market adoption, and rapid ROI.
Airbee Wireless Inc has tied up with Radiocrafts AS to deliver "out-of-the-box"
ZigBee-ready solutions; the former supplying the software and the latter making the
module platforms. With even light controls and thermostat producers joining the ZigBee
Alliance, the list is growing healthily and includes big OEM names like HP, Philips,
Motorola and Intel.
With ZigBee designed to enable two-way communications, not
only will the consumer be able to monitor and keep track of domestic utilities usage, but
also feed it to a computer system for data analysis.


A recent analyst report issued by West Technology Research Solutions estimates
that by the year 2008, "annual shipments for ZigBee chipsets into the home automation
segment alone will exceed 339 million units," and will show up in "light switches, fire
and smoke detectors, thermostats, appliances in the kitchen, video and audio remote
controls, landscaping, and security systems."
Futurists are sure to hold ZigBee up and say, "See, I told you so". The ZigBee Alliance is
nearly 200 strong and growing, with more OEM's signing up. This means that more and
more products and even later, all devices and their controls will be based on this standard.
Since Wireless personal Area Networking applies not only to household devices, but also
to individualised office automation applications, ZigBee is here to stay. It is more than
likely the basis of future home-networking solutions.

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22-06-2010, 01:35 PM
Post: #5
RE: Seminar Report On ZigBee: Next Generation Wireless Network
ZigBee and IEEE 802.15.4
ZigBee technology is a low data rate, low power consumption, low cost, wireless networking proto¬col targeted towards automation and remote control applications. IEEE 802.15.4 committee started working on a low data rate standard a short while later. Then the ZigBee Alliance and the IEEE decided to join forces and ZigBee is the commercial name for this technology.
ZigBee is expected to provide low cost and low power connectivity for equipment that needs battery life as long as several months to several years but does not require data transfer rates as high as those enabled by Bluetooth. In addition, ZigBee can be implemented in mesh networks larger

than is possible with Bluetooth. ZigBee compliant wireless devices are expected to transmit 10-75 meters, depending on the RF environment and the power output consumption required for a given application, and will operate in the unlicensed RF worldwide(2.4GHz global, 915MHz Americas or 868 MHz Europe). The data rate is 250kbps at 2.4GHz, 40kbps at 915MHz and 20kbps at 868MHz.
IEEE and ZigBee Alliance have been working closely to specify the entire protocol stack. IEEE 802.15.4 focuses on the specification of the lower two layers of the protocol(physical and data link layer). On the other hand, ZigBee Alliance aims to provide the upper layers of the protocol stack (from network to the application layer) for interoperable data networking, security services and a range of wireless home and building control solutions, provide interoperability compliance testing, marketing of the standard, advanced engineering for the evolution of the standard. This will assure consumers to buy products from different manufacturers with confidence that the products will work together

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