Docstoc

Zigbee Technology

Document Sample
Zigbee Technology Powered By Docstoc
					Contents
        Abstract


   ●   Introduction


   ●   Origin of the name Zigbee


   ●   Characteristics


   ●   Architecture
        Physical layer
        Media access control layer
        Network layer
        Security layer

   ●   Comparison between the wireless standards


   ●   Applications
        A new twist on, "I've fallen and I can't get up”
       “The bugs this system catches aren't in software”
        “Home to homeowner: "The toilet is leaking."
   ●   ZIGBEEF


   ●   Conclusion



                                                           1
     ●   References




ABSTRACT                                     o INTRODUCTION

 ZigBee is a low-power wireless         Zigbee’s key technical features
 technology, rewriting the wireless    include three license free frequency
 sensor equation. It is a secure       bands-2.4GHz, 868MHz, 915MHz
 network technology that rides on      ;multiple channels ;up to 100mts
 top of the recently ratified IEEE     range; CSMA-CA channel access;
 802.15.4 radio standard.              low      power,   long   battery    life;
                                       supporting up to 255devices per
         It is designed to interact
                                       network.
 with the remote controlled devices,
 which are put under a single             Zigbee is used in home security
 standardized control interface that   systems where wireless sensors are
 can interconnect into a network       easily     installed than sensors that
 .Once associated with a network, a    need wiring. The same is true in
 ZigBee node can wake up and           industrial     environments,       where
 communicate with other ZigBee         wiring typically accounts for 80%
 devices and return to sleep.          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.




                                                                                   2
     o ORIGIN OF THE NAME ZIGBEE
                                       Principle. Using this silent, but
The network name comes from the
                                       powerful communication system,
zigzagging path a bee (a data
                                       whereby the bee dances in a zigzag
packet) takes to get from flower to
                                       pattern, they are able to      share
flower (or node to node). The
                                       information such as the location,
technique that honey bees use to
                                       distance, and direction of a newly
communicate         new-found   food
                                       discovered food source to her
sources to other members of the
                                       fellow colony members.
colony is referred to as the ZigBee




 o CHARACTERISTICS                         Reliable data transfer
                                           Appropriate levels of security
                                           Direct sequence spread spectrum
    Low cost — Extends wireless to         — Fast acquisition time
     virtually any sensor                  Range- 50m typical (5-500m
    Low power consumption — Ideal          based on environment)
     for battery operation                 Multiple topologies- star, peer-
    Small size, light weight — Easy        to-peer, mesh
     to integrate
    Ease of implementation


                                                                              3
      Data rates of 250 kbps (@2.4                 and 20 kbps (@868 MHz)
       GHz), 40 kbps (@ 915 MHz),



   o ARCHITECHTURE
ZigBee stack architecture follows the      The layers above them are defined by
standard         Open          Systems     the ZigBee Alliance.
Interconnection (OSI) reference model,         The model has five layers namely
ZigBee's protocol stack is structured in       1.      Physical   (PHY)      layer
layers. The first two layers, physical     2. Media access control (MAC) layer
(PHY) and media access (MAC), are              3. Network (NWK) and security
defined by the IEEE 802.15.4 standard.     layers 4. Application framework
                                               5. Application profiles




                                                                                  4
                      Application Framework                   ZP    ZigBee Device
                                                              UI
                                                                    Object (ZDO)
                  Application               Application
                  Object 240                 Object 1
                 [On Endpoint 240]          [On Endpoint 1]        [On Endpoint 0]

            AP     APSDE-SAP                 APSDE-SAP              APSDE-SAP        AP
            SS                                                                       S
            E-                                                                       M
            SA                                                                       E-
Security     P            Application Support (APS) Layer                            SA
                                                                                     P
Service     NL   NLDE-SAP                                                            NL
Provider    SE
             -
                                                                                     M
                                                                                     E-
            SA
             P                       Network (NWK) Layer                             SA
                                                                                     P


                 MCPS-SAP                                           MLME-SAP



                        Medium Access Layer (MAC) Layer
                   PD-SAP                                            PLME-SAP



                                     Physical (PHY) Layer

                                        Figure : ZigBee Stack Model




     PHYSICAL LAYER:


                                                    2.4GHz (16 channels), 40Kbps at
ZigBee-compliant products operate
                                                    915MHz (10 channels), and 20Kbps
in unlicensed bands worldwide,
                                                    at    868MHz      (1    channel).     The
including 2.4GHz (global), 902 to
                                                    transmission distance is expected to
928MHz (Americas), and 868MHz
                                                    range from 10 to 75m, depending
(Europe). Raw data throughput rates
                                                    on power output and environmental
of 250Kbps can be achieved at
                                                    characteristics. Like Wi-Fi, Zigbee


                                                                                                5
  uses       direct-sequence           spread              spacing. The 868 and 900MHz
  spectrum in the 2.4GHz band, with                        bands   also    use   direct-sequence
  offset-quardrature           phase-shift                 spread spectrum but with binary-
  keying modulation. Channel width                         phase-shift keying modulation
  is     2MHz       with   5MHzchannel

Table: Frequency bands and data rates



                                                Spreading Parameters             Data Parameters
            Frequency       Channel
 PHY
              Band         Numbering
                                                 Chip                     Bit    Symbol
                                                         Modulation                        Modulation
                                                 Rate                     Rate    Rate

            868 to 870                          300 k                      20     20 k
868 to                             0                        BPSK                             BPSK
              MHz                               chip/s                    kb/s    baud
 915
MHz
            902 to 928                          600 k                      40     40 k
                               1 to 10                      BPSK                             BPSK
              MHz                               chip/s                    kb/s    baud


 2.4          2.4 to                            2.0 M                     250     62.5 k     16-ary
                             11 to 26                      O-QPSK
 GHz       2.4835 GHz                           chip/s                    kb/s     baud    Orthogonal




        MEDIA ACCESS CONTROL LAYER



The media access control (MAC) layer                     MAC allows a reduced functionality
was      designed    to    allow       multiple          device (RFD) that needn't have flash nor
topologies without         complexity. The               large amounts of ROM or RAM. The
power management operation doesn't                       MAC was designed to handle large
require multiple modes of operation. The



                                                                                                   6
numbers of devices without requiring         superframe structure with beacons for
them to be "parked".                         time synchronization, and a guaranteed
                                             time-slot mechanism for high-priority
The MAC provides network association
                                             communications
and disassociation, has an optional
Frame structure: Figure illustrates the four basic frame types defined in 802.15.4:
data, ACK, MAC command, and beacon.




Figure:: The four basic frame types defined in 802.15.4: Data, ACK, MAC command,
and beacon

The data frame provides a payload of         Another important structure for 802.15.4
up to 104 bytes. The frame is numbered       is the acknowledgment (ACK) frame.
to ensure that all packets are tracked. A    It provides feedback from the receiver to
frame-check     sequence   ensures   that    the sender confirming that the packet
packets are received without error. This     was received without error. The device
frame structure improves reliability in      takes advantage of specified "quiet time"
difficult conditions.                        between frames to send a short packet




                                                                                    7
immediately     after     the    data-packet      Finally, the beacon frame wakes up
transmission.                                     client devices, which listen for their
                                                  address and go back to sleep if they don't
A MAC command frame provides the
                                                  receive it. Beacons are important for
mechanism for remote control and
                                                  mesh and cluster-tree networks to keep
configuration   of      client   nodes.   A
                                                  all the nodes synchronized without
centralized network manager uses MAC
                                                  requiring those     nodes    to     consume
to configure individual clients' command
                                                  precious battery energy by listening for
frames no matter how large the network.
                                                  long periods of time.




    NETWORK LAYER

Zigbee’s self-forming and self-healing            data reliability. It may also be used to
mesh-network architecture lets data and           build large, geographically dispersed
control messages pass from one node to            networks with smaller networks linked
another by multiple paths. This feature           to form a 'cluster-tree' network.
extends the network range and improves




                                               Mesh



 Star



                                                             PAN coordinator
        Cluster Tree                                         Full Function Device
                                                             Reduced Function Device




                                                                                            8
The NWK layer supports multiple                starting the network and for choosing
network    topologies    including     star,   key network parameters, but the network
cluster tree, and mesh, all of which are       may be extended through the use of
shown in Figure                                ZigBee routers. The routing algorithm
                                               uses a request-response protocol to
In a star topology, one of the FFD-type
                                               eliminate sub-optimal routing. Ultimate
devices assumes the role of network
                                               network size can reach 264 nodes (more
coordinator   and   is   responsible    for
                                               than we'll probably need). Using local
initiating and maintaining the devices on
                                               addressing, you can configure simple
the network. All other devices, known as
                                               networks of more than 65,000 (216)
end devices, directly communicate with
                                               nodes,     thereby     reducing     address
the coordinator. In a mesh topology, the
                                               overhead
ZigBee coordinator is responsible for




    Security layer

Security and data integrity are key                    data   encryption,    which   uses
benefits of the ZigBee technology.                      symmetric key 128-bit advanced
ZigBee leverages the security model of                  encryption standard
the IEEE 802.15.4 MAC sub-layer                        frame integrity to protect data
which specifies four security services:                 from being modified by parties
access control—the device maintains a                   without cryptographic keys
list of trusted devices within the network             sequential freshness to reject data
                                                        frames that have been replayed—
                                                        the network controller compares
                                                        the freshness value with the last


                                                                                         9
    known value from the device and                has not been updated to a new
    rejects it if the freshness value              value

      o COMPARISION BETWEEN THE WIRELESS
         STANDARDS




.




    o 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”




                                                                                  10
       The figure basically shows a home-
monitoring system for senior citizens.
Zigbee-based sensors keep an eye on
elderly residents living alone and warn
medics about changes in habits that are
potentially serious; It      includes a light
switch with a tiny digital    camera (left); a
pendant (center) worn        around the neck;
and movement tags (right), which can let
the system generate an alert based either on
detected movement or the lack of any
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




                                                                                     11
             “The bugs this system catches aren't in software”


         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 the technique now
used on several levels. Existing methods force
exterminators to physically check each station for
activity. Termites could cause severe damage long
before evidence of them could turn up during a
periodic inspection. In contrast, the Zigbee bait
stations monitor pest activity 24/7. And exterminators
need not make long trips just to examine bait stations

              “Home to homeowner: "The toilet is leaking."
                                                  your pocket or onto a key chain.
This type of home automation
                                                  When the Key leaves the range of
system called the Home Heartbeat
                                                  the base station, it carries with it the
system   gives   homeowners       an
                                                  last status of items such as doors,
awareness of what's going on inside
                                                  windows, and lights, as read by
their house, even if they happen to
                                                  sensors on the Zigbee network.
be thousands of miles away.
                                                  Homeowners wondering whether
Two key components of the system                  they left the garage door open could
are a base station and a Home Key.                conceivably tell by looking at the
The Key is envisioned to go into                  LCD in their Home Key. (However,



                                                                                         12
the system stops short of asking a            A variety of sensors have been devised
sympathetic neighbor to come over             for the system. In addition to proximity
and rectify the problem.)                     switches for doors and windows, there
                                              are devices designed to detect leaking
The base station is smart enough to
                                              pipes, ac loads, and even remind
notice if one of the sensors changes
                                              homeowners about periodic maintenance
state when the Home Key is out of
                                              items such as low batteries in smoke
range. In this case it can send the
                                              detectors or the need for seasonal gutter
homeowner's cell phone a text
                                              cleaning. One         worthy piece of the
message detailing what's wrong.
                                              system is a water shut-off valve.




8.6 Zigbeef




   o ZIGBEEF:
                                                reading-range over passive wand-
Zigbeef is a solution for tracking
                                                based tag technology. Producers are
cattle. Zigbee sensors give beef
                                                no   longer limited     to     infrequent
producers        the       ability      to
                                                opportunities to scan IDs. Zigbeef
electronically         identify      cattle
                                                allows identification         of          each
whether their herds are crowded
                                                animal on     the    range,        pen,     or
into chutes, gathered into pens, or
                                                working chute, at virtually any time.
grazing open pasture. Zigbeef radio-
                                                ZigBeef tags use mass-produced,
based cattle ear tags offer superior
                                                non-proprietary      wireless        sensor


                                                                                             13
technologies, offering a proven        [Refer the greeting preview for the
solution at an inexpensive price.      figure].




   o CONCLUSION

There are many wireless monitoring     Zigbee promises to put wireless
and control applications for           sensors in everything from factory
industrial and home markets which      automation systems to home
require longer battery life, lower     security systems to consumer
data rates and less complexity than    electronics. Zigbee is a new
available from existing wireless       standard that still needs to pass
standards like Bluetooth and Wi-Fi.    through the circles or rigorous
So, there was a need for a standard    technology critics and establish its
based, interoperable wireless          own place in the industry. The next
technology that addresses the          zigbee challenge will be devising
unique needs of low data rate          the proposed extension to the
wireless control and sensor based      802.15.4 standard,’4a’ which could
networks. In this regard, zigbee was   be based on ultra-wideband (UWB).
poised to become the global
control/sensor network standard.


  o REFERENCES

1. Electronics for you- November       6. www.nuri.com
2004

2. Computer networks-by
Tanenbaum

3. www.zigbeealliance.com

4. www.zigbee.org

5. www.zigbeef.com



                                                                              14

				
DOCUMENT INFO
Shared By:
Stats:
views:57
posted:7/24/2012
language:English
pages:14
Description: 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.