ZIGBEE-TECHNOLOGY by keralaguest




             “ZEITGEIST „09”

                  NIMRA NAGAR



  ●   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."

  ●   Conclusion

  ●   References


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

                                       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                         Appropriate levels of security
                                           Direct sequence spread spectrum
                                            — Fast acquisition time
    Low cost — Extends wireless to        Range- 50m typical (5-500m
     virtually any sensor                   based on environment)
    Low power consumption — Ideal         Multiple topologies- star, peer-
     for battery operation                  to-peer, mesh
    Small size, light weight — Easy       Data rates of 250 kbps (@2.4
     to integrate                           GHz), 40 kbps (@ 915 MHz),
    Ease of implementation                 and 20 kbps (@868 MHz)
    Reliable data transfer

                                        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

                          Application Framework                   ZP    ZigBee Device
                                                                        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
 Service      NL     NLDE-SAP                                                            NL
 Provider     SE
               P                         Network (NWK) Layer                             SA

                     MCPS-SAP                                           MLME-SAP

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

                                         Physical (PHY) Layer

                                            Figure : ZigBee Stack Model


                                                     on power output and environmental
  ZigBee-compliant products operate
                                                     characteristics. Like Wi-Fi, Zigbee
  in unlicensed bands worldwide,
                                                     uses     direct-sequence          spread
  including 2.4GHz (global), 902 to
                                                     spectrum in the 2.4GHz band, with
  928MHz (Americas), and 868MHz
                                                     offset-quardrature           phase-shift
  (Europe). Raw data throughput rates
                                                     keying modulation. Channel width
  of 250Kbps can be achieved at
                                                     is     2MHz      with     5MHzchannel
  2.4GHz (16 channels), 40Kbps at
                                                     spacing. The 868 and 900MHz
  915MHz (10 channels), and 20Kbps
                                                     bands    also    use    direct-sequence
  at   868MHz    (1    channel).     The
                                                     spread spectrum but with binary-
  transmission distance is expected to
                                                     phase-shift keying modulation
  range from 10 to 75m, depending

Table: Frequency bands and data rates

                                           Spreading Parameters              Data Parameters
          Frequency      Channel
            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
          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


The media access control (MAC) layer         numbers of devices without requiring
was    designed      to   allow   multiple   them to be "parked".
topologies without        complexity. The
                                             The MAC provides network association
power management operation doesn't
                                             and disassociation, has an optional
require multiple modes of operation. The
                                             superframe structure with beacons for
MAC allows a reduced functionality
                                             time synchronization, and a guaranteed
device (RFD) that needn't have flash nor
                                             time-slot mechanism for high-priority
large amounts of ROM or RAM. The
MAC was designed to handle large

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           A MAC command frame provides the
up to 104 bytes. The frame is numbered         mechanism for remote control and
to ensure that all packets are tracked. A      configuration    of     client        nodes.   A
frame-check     sequence      ensures   that   centralized network manager uses MAC
packets are received without error. This       to configure individual clients' command
frame structure improves reliability in        frames no matter how large the network.
difficult conditions.
                                               Finally, the beacon frame wakes up
Another important structure for 802.15.4       client devices, which listen for their
is the acknowledgment (ACK) frame.             address and go back to sleep if they don't
It provides feedback from the receiver to      receive it. Beacons are important for
the sender confirming that the packet          mesh and cluster-tree networks to keep
was received without error. The device         all the nodes synchronized without
takes advantage of specified "quiet time"      requiring those       nodes      to     consume
between frames to send a short packet          precious battery energy by listening for
immediately     after   the     data-packet    long periods of time.


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



                                                             PAN coordinator
        Cluster Tree                                         Full Function Device
                                                             Reduced Function Device

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
ZigBee coordinator is responsible for

    Security layer

Security and data integrity are key             frame integrity to protect data
benefits of the ZigBee technology.               from being modified by parties
ZigBee leverages the security model of           without cryptographic keys
the IEEE 802.15.4 MAC sub-layer                 sequential freshness to reject data
which specifies four security services:          frames that have been replayed—
access control—the device maintains a            the network controller compares
list of trusted devices within the network       the freshness value with the last
                                                 known value from the device and
      data   encryption,    which    uses
                                                 rejects it if the freshness value
       symmetric key 128-bit advanced
                                                 has not been updated to a new
       encryption standard




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-
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

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

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

8.6 Zigbeef

                                                based cattle ear tags offer superior
Zigbeef is a solution for tracking
                                                reading-range over passive wand-
cattle. Zigbee sensors give beef
                                                based tag technology. Producers are
producers        the       ability      to
                                                no   longer limited     to     infrequent
electronically         identify      cattle
                                                opportunities to scan IDs. Zigbeef
whether their herds are crowded
                                                allows identification         of          each
into chutes, gathered into pens, or
                                                animal on     the    range,        pen,     or
grazing open pasture. Zigbeef radio-

working chute, at virtually any time.    solution at an inexpensive price.
ZigBeef tags use mass-produced,          [Refer the greeting preview for the
non-proprietary    wireless     sensor   figure].
technologies, offering a proven


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.


1. Electronics for you- November         4. www.zigbee.org
                                         5. www.zigbeef.com
2. Computer networks-by
Tanenbaum                                6. www.nuri.com

3. www.zigbeealliance.com


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