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INTRODUCTION
ZigBee is a low-power wireless
technology, rewriting the wireless
sensor equation. It is a secure network
technology that rides on top of the
recently ratified IEEE 802.15.4 radio
standard. It is designed to interact with
the remote controlled devices, which are
put under a single standardized control
interface that can interconnect into a
network. Once associated with a
network, a ZigBee node can wake up
and communicate with other ZigBee
devices and return to sleep.
Zigbee’s key technical features include three license free frequency bands-2.4GHz, 868MHz, 915MHz;multiple channels; up to 100mts range; CSMA-CA channel access; low power, long battery life; supporting up to 255devices per network.
Zigbee is used in home security systems
where wireless sensors are easily
installed than sensors that need wiring.
The same is true in industrial
environments, where wiring typically
accounts for 80% of the cost of sensor
installations. And then there are
applications for sensors where wiring
isn't practical or even possible. ZigBee
promises to put wireless sensors in
everything from factory automation
systems to home security systems to
consumer electronics.
ORIGIN OF THE NAME ZIGBEE
The network name comes from the
zigzagging path a bee (a data packet)
takes to get from flower to flower (or
node to node). The technique that
honeybees use to communicate
newfound food sources to other
members of the colony is referred to as
the ZigBee Principle. Using this silent,
but powerful communication system,
whereby the bee dances in a zigzag
pattern, they are able to share
information such as the location,
distance, and direction of a newly
Zig BeeBy B. Samirana Acharya & N.Vamshikrishna
Kamala institute of technology & science (Singapuram) Huzurabad, Karimnagar (Dist), A.P
Mobile No: 9441847039 E-mail: [email protected]
discovered food source to her fellow
colony members.
CHARACTERISTICSCHARACTERISTICS Low costLow cost — Extends wireless to — Extends wireless to
virtually any sensor virtually any sensor
Low power consumptionLow power consumption — Ideal for — Ideal for
battery operation battery operation
Small size, light weight Small size, light weight — Easy to— Easy to
integrate integrate
Ease of implementation Ease of implementation
Reliable data transfer Reliable data transfer
Appropriate levels of security Appropriate levels of security
Direct sequence spread spectrumDirect sequence spread spectrum — —
Fast acquisition time Fast acquisition time
Range- 50m typical (5-500m based onRange- 50m typical (5-500m based on
environment)environment)
Multiple topologies- star, peer-to-peer,Multiple topologies- star, peer-to-peer,
mesh mesh
Data rates of 250 kbps (@2.4 GHz), 40Data rates of 250 kbps (@2.4 GHz), 40
kbps (@ 915 MHz), and 20 kbpskbps (@ 915 MHz), and 20 kbps
(@868 MHz) (@868 MHz)
ARCHITECHTUREARCHITECHTURE
ZigBee stack architectureZigBee stack architecture follows the follows the
standardstandard Open Systems Interconnection Open Systems Interconnection
(OSI) reference model; ZigBee's protocol(OSI) reference model; ZigBee's protocol
stack is structured in layers. The first twostack is structured in layers. The first two
layers, physical (PHY) and media accesslayers, physical (PHY) and media access
(MAC), are defined by the IEEE 802.15.4(MAC), are defined by the IEEE 802.15.4
standard. The layers above them arestandard. The layers above them are
defined by the ZigBee Alliance. defined by the ZigBee Alliance.
The model has five layers namely The model has five layers namely
1. Physical (PHY) layer 1. Physical (PHY) layer
2. Media access control (MAC) layer2. Media access control (MAC) layer
3. Network (NWK) and security layers3. Network (NWK) and security layers
4. Application framework 4. Application framework
5. Application profiles5. Application profiles
PHYSICAL LAYER:
ZigBee-compliant products operate
in unlicensed bands worldwide,
including 2.4GHz (global), 902 to
928MHz (Americas), and 868MHz
(Europe). Raw data throughput rates of
250Kbps can be achieved at 2.4GHz (16
channels), 40Kbps at 915MHz (10
channels), and 20Kbps at 868MHz (1
channel). The transmission distance is
expected to range from 10 to 75m,
depending on power output and
environmental characteristics. Like Wi-
FFiigguurree:: ZZiiggBBeeee SSttaacckk MMooddeell
Physical (PHY) Layer
Security Service Provider
PD-SAP
APSSE-SAP
NLSE-
SAP
PLME-SAP
Medium Access Layer (MAC) Layer
MLME-SAP MCPS-SAP
Network (NWK) Layer
NLME-SAP
NLDE-SAP
Application Support (APS) Layer
APSDE-SAP APSDE-SAP APSDE-SAP APSME-SAP
Application Framework
Application Object 240
[On Endpoint 240]
Application Object 1
[On Endpoint 1]
ZPUI
ZigBee Device Object (ZDO)
[On Endpoint 0]
Fi, Zigbee uses direct-sequence spread
spectrum in the 2.4GHz band, with
offset-quardrature phase-shift keying
modulation. Channel width is 2MHz
with 5MHzchannel spacing. The 868
and 900MHz bands also use direct-
sequence spread spectrum but with
binary-phase-shift keying modulation
Table: Frequency bands and data rates
PHY PHY FrequencFrequenc
y Band y Band
ChannelChannel
NumberinNumberin
gg
SpreadingSpreading
ParametersParametersData Parameters Data Parameters
ChipChip
RateRate
ModMod
ulatiulati
onon
BitBit
RateRate
SymSym
bolbol
RateRate
ModMod
ulatiulati
on on
868 to868 to
915915
MHz MHz
868 to868 to
870 MHz870 MHz00
300 k300 k
chip/schip/s
BPSBPS
KK
2020
kb/skb/s
20 k20 k
baudbaud
BPSBPS
KK
902 to902 to
928 MHz928 MHz1 to 101 to 10
600 k600 k
chip/schip/s
BPSBPS
KK
4040
kb/s kb/s
40 k40 k
baudbaud
BPSBPS
KK
2.42.4
GHzGHz
2.4 to2.4 to
2.48352.4835
GHz GHz
11 to 2611 to 262.0 M2.0 M
chip/schip/s
O-O-
QPSQPS
KK
250250
kb/s kb/s
62.562.5
kk
baud baud
16-16-
aryary
OrthOrth
ogonogon
al al
MEDIA ACCESS CONTROL LAYER
The media access control (MAC)The media access control (MAC)
layer was designed to allow multiplelayer was designed to allow multiple
topologies without complexity. Thetopologies without complexity. The
power management operation doesn'tpower management operation doesn't
require multiple modes of operation. Therequire multiple modes of operation. The
MAC allows a reduced functionalityMAC allows a reduced functionality
device (RFD) that needn't have flash nordevice (RFD) that needn't have flash nor
large amounts of ROM or RAM. Thelarge amounts of ROM or RAM. The
MAC was designed to handle largeMAC was designed to handle large
numbers of devices without requiring themnumbers of devices without requiring them
to be "parked". to be "parked".
The MAC provides network associationThe MAC provides network association
and disassociation, has an optionaland disassociation, has an optional
superframe structure with beacons for timesuperframe structure with beacons for time
synchronization, and a guaranteed time-synchronization, and a guaranteed time-
slot mechanism for high-priorityslot mechanism for high-priority
communicationscommunications
Frame structureFrame structure ::
Figure illustratesFigure illustrates the four basic frame the four basic frame
types defined in 802.15.4: data, ACK, types defined in 802.15.4: data, ACK,
MAC command, and beacon. MAC command, and beacon.
Figure:Figure:: The four basic frame types: The four basic frame types
defined in 802.15.4: Data, ACK, MACdefined in 802.15.4: Data, ACK, MAC
command, and beaconcommand, and beacon
The The data framedata frame provides a payload of up provides a payload of up
to 104 bytes. The frame is numbered toto 104 bytes. The frame is numbered to
ensure that all packets are tracked. Aensure that all packets are tracked. A
frame-check sequence ensures that packetsframe-check sequence ensures that packets
are received without error. This frameare received without error. This frame
structure improves reliability in difficultstructure improves reliability in difficult
conditions. conditions.
Another important structure for 802.15.4 isAnother important structure for 802.15.4 is
the the acknowledgment (ACK) frameacknowledgment (ACK) frame. It. It
provides feedback from the receiver to theprovides feedback from the receiver to the
sender confirming that the packet wassender confirming that the packet was
received without error. The device takesreceived without error. The device takes
advantage of specified "quiet time"advantage of specified "quiet time"
between frames to send a short packetbetween frames to send a short packet
immediately after the data-packetimmediately after the data-packet
transmission. transmission.
A A MAC command frameMAC command frame provides the provides the
mechanism for remote control andmechanism for remote control and
configuration of client nodes. Aconfiguration of client nodes. A
centralized network manager uses MAC tocentralized network manager uses MAC to
configure individual clients' commandconfigure individual clients' command
frames no matter how large the network. frames no matter how large the network.
Finally, the Finally, the beacon framebeacon frame wakes up client wakes up client
devices, which listen for their address anddevices, which listen for their address and
go back to sleep if they don't receive it.go back to sleep if they don't receive it.
Beacons are important for mesh andBeacons are important for mesh and
cluster-tree networks to keep all the nodescluster-tree networks to keep all the nodes
synchronized without requiring thosesynchronized without requiring those
nodes to consume precious battery energynodes to consume precious battery energy
by listening for long periods of time. by listening for long periods of time.
NETWORK LAYERNETWORK LAYER
ZigBee's self-forming and self-healingZigBee's self-forming and self-healing
mesh-network architecture lets data andmesh-network architecture lets data and
control messages pass from one node tocontrol messages pass from one node to
another by multiple paths. This featureanother by multiple paths. This feature
extends the network range and improvesextends the network range and improves
data reliability. It may also be used todata reliability. It may also be used to
build large, geographically dispersedbuild large, geographically dispersed
networks with smaller networks linked tonetworks with smaller networks linked to
form a 'cluster-tree' network. form a 'cluster-tree' network.
The NWK layer supports multiple networkThe NWK layer supports multiple network
topologies including star, cluster tree, and topologies including star, cluster tree, and
mesh, all of which are shown in mesh, all of which are shown in Figure Figure
In a star topology, one of the FFD-typeIn a star topology, one of the FFD-type
devices assumes the role of networkdevices assumes the role of network
coordinator and is responsible forcoordinator and is responsible for
initiating and maintaining the devices oninitiating and maintaining the devices on
the network. All other devices, known asthe network. All other devices, known as
end devices, directly communicate withend devices, directly communicate with
the coordinator. In a mesh topology, thethe coordinator. In a mesh topology, the
ZigBee coordinator is responsible forZigBee coordinator is responsible for
starting the network and for choosing keystarting the network and for choosing key
network parameters, but the network maynetwork parameters, but the network may
be extended through the use of ZigBeebe extended through the use of ZigBee
routers. The routing algorithm uses arouters. The routing algorithm uses a
request-response protocol to eliminate sub-request-response protocol to eliminate sub-
PAN coordinator Full Function Device Reduced Function Device
Star
Mesh
Cluster Tree
optimal routing. Ultimate network size canoptimal routing. Ultimate network size can
reach 264 nodes (more than we'll probablyreach 264 nodes (more than we'll probably
need). Using local addressing, you canneed). Using local addressing, you can
configure simple networks of more thanconfigure simple networks of more than
65,000 (216) nodes, thereby reducing65,000 (216) nodes, thereby reducing
address overheadaddress overhead
Security layerSecurity layer
Security and data integrity are key benefitsSecurity and data integrity are key benefits
of the ZigBee technology. ZigBeeof the ZigBee technology. ZigBee
leverages the security model of the IEEEleverages the security model of the IEEE
802.15.4 MAC sub-layer which specifies802.15.4 MAC sub-layer which specifies
four security services: access control—thefour security services: access control—the
device maintains a list of trusted devicesdevice maintains a list of trusted devices
within the network within the network
Data encryption, which usesData encryption, which uses
symmetric key 128-bit advancedsymmetric key 128-bit advanced
encryption standard encryption standard
Frame integrity to protect data fromFrame integrity to protect data from
being modified by parties withoutbeing modified by parties without
cryptographic keys cryptographic keys
Sequential freshness to reject dataSequential freshness to reject data
frames that have been replayed—theframes that have been replayed—the
network controller compares thenetwork controller compares the
freshness value with the last knownfreshness value with the last known
value from the device and rejects it ifvalue from the device and rejects it if
the freshness value has not beenthe freshness value has not been
updated to a new value updated to a new value
COMPARISION BETWEEN COMPARISION BETWEEN THE WIRELESS STANDARDSTHE WIRELESS STANDARDS
APPLICATIONS
Potential applications of zigbee include the
building automation, industrial, medical
and residential control & monitoring
A new twist on, "I've fallen and I
can't get up”
The figure basically shows a home-The figure basically shows a home-
monitoring system for senior citizens.monitoring system for senior citizens.
Zigbee-based sensors keep an eye onZigbee-based sensors keep an eye on
elderly residents living alone and warnelderly residents living alone and warn
medics about changes in habits that aremedics about changes in habits that are
potentially serious;potentially serious; It includes a lightIt includes a light
switch with a tiny digital camera (left); aswitch with a tiny digital camera (left); a
pendant (center) worn around the neck;pendant (center) worn around the neck;
and movement tags (right), which can letand movement tags (right), which can let
the system generate an alert based eitherthe system generate an alert based either
on detected movement or the lack of anyon detected movement or the lack of any
movement.movement.
Zigbee doesn't have the bandwidth to
handle video. So light switch / camera
combos deliver still images to a controller.
An alert from the pendant or from one of
the tags activates the camera.
The pendant includes accelerometers that
detect the forces of a person falling. It also
contains a panic button. The device can
send a warning either to a monitoring
company or family member if something
is up. It can be programmed to generate an
alert, for example, if a bedroom or
refrigerator door hasn't opened by noon.
The bugs this system catches aren't inThe bugs this system catches aren't in
softwaresoftware
One of the more offbeat
applications for Zigbee sensors is in
catching termites. Wireless bait stations
are devised which act as Zigbee nodes.
In operation, the bait stations go
into the ground at numerous spots
surrounding a house. Each bait station has
a special sensor that triggers when termites
eat at the wood it contains. The station
then signals this activity to a receiver,
which sends an e-mail.
This wireless approach beats theThis wireless approach beats the
technique now used on several levels.technique now used on several levels.
Existing methods force exterminators toExisting methods force exterminators to
physically check each station for activity.physically check each station for activity.
Termites could cause severe damage longTermites could cause severe damage long
before evidence of them could turn upbefore evidence of them could turn up
during a periodic inspection. In contrast,during a periodic inspection. In contrast,
the Zigbee bait stations monitor pestthe Zigbee bait stations monitor pest
activity 24/7. And exterminators need notactivity 24/7. And exterminators need not
make long trips just to examine baitmake long trips just to examine bait
stationsstations
Two key components of the
system are a base station and a Home
Key. The Key is envisioned to go into
your pocket or onto a key chain.
When the Key leaves the range of the
base station, it carries with it the last
status of items such as doors,
windows, and lights, as read by
sensors on the Zigbee network.
Homeowners wondering whether they
left the garage door open could
conceivably tell by looking at the
LCD in their Home Key. (However,
the system stops short of asking a
sympathetic neighbor to come over
and rectify the problem.)
The base station is smart enough to
notice if one of the sensors changes
state when the Home Key is out of
range. In this case it can send the
homeowner's cell phone a text
message detailing what's wrong.
A variety of sensors have been devised for
the system. In addition to proximity
switches for doors and windows, there are
devices designed to detect leaking pipes,
ac loads, and even remind homeowners
about periodic maintenance items such as
low batteries in smoke detectors or the
need for seasonal gutter cleaning. One
worthy piece of the system is a water shut-worthy piece of the system is a water shut-
off valve.off valve.
Zigbeef is a solution for trackingZigbeef is a solution for tracking
cattle. Zigbee sensors give beef producerscattle. Zigbee sensors give beef producers
the ability to electronically identify cattlethe ability to electronically identify cattle
whether their herds are crowded intowhether their herds are crowded into
chutes, gathered into pens, or grazing openchutes, gathered into pens, or grazing open
pasture.pasture. ZigBeef radio-based cattle earZigBeef radio-based cattle ear
tags offertags offer superior reading-range oversuperior reading-range over
passive wand-based tag technology.passive wand-based tag technology.
Producers are no longerProducers are no longer limited tolimited to
infrequent opportunities to scaninfrequent opportunities to scan
IDs.IDs. ZigBeef allowsZigBeef allows identification of eachidentification of each
animalanimal on the range, pen, or workingon the range, pen, or working
chute, at virtually any time. ZigBeef tagschute, at virtually any time. ZigBeef tags
use mass-produced, non-proprietaryuse mass-produced, non-proprietary
wireless sensor technologies, offering awireless sensor technologies, offering a
proven solution at an inexpensive price.proven solution at an inexpensive price.
[refer the greeting preview for the figure].[refer the greeting preview for the figure].
CONCLUSION
There are many wireless monitoring and
control applications for industrial and
home markets which require longer battery
life, lower data rates and less complexity
than available from existing wireless
standards like Bluetooth and Wi-Fi. So,
there was a need for a standard based,
interoperable wireless technology that
addresses the unique needs of low data rate
wireless control and sensor based
networks. In this regard, zigbee was poised
to become the global control/sensor
network standard.
Zigbee promises to put wireless sensors in
everything from factory automation
systems to home security systems to
consumer electronics. Zigbee is a new
standard that still needs to pass through the
circles or rigorous technology critics and
establish its own place in the industry. The
next zigbee challenge will be devising the
proposed extension to the 802.15.4
standard,’4a’ which could be based on
ultra-wideband (UWB).
REFERENCES
1. Electronics for you- November 2004
2. Computer networks-by Tanenbaum
3. www.zigbeealliance.com4. www.zigbee.org5. www.zigbeef.com6. www.nuri.com