Lecture 15

Vishal Choudhary
vishalhim@yahoo.com
ZigBee Wireless Technology
Architecture and Applications

What is Zigbee Technology
 Zigbee communication is specially built for control
and sensor networks on IEEE 802.15.4 standard
for wireless personal area networks (WPANs),
and it is the product from Zigbee alliance.
This communication standard defines physical
and Media Access Control (MAC) layers to handle
many devices at low-data rates. These Zigbee’s
WPANs operate at 868 MHz, 902-928MHz and
2.4 GHz frequencies. The date rate of 250 kbps is
best suited for periodic as well as intermediate
two way transmission of data between sensors
and controllers.

 Zigbee is low-cost and low-powered mesh
network widely deployed for controlling and
monitoring applications where it covers 10-100
meters within the range. This communication
system is less expensive and simpler than the
other proprietary short-range wireless sensor
networks as Bluetooth and Wi-Fi.

 Zigbee supports different network configurations
for master to master or master to slave
communications. And also, it can be operated in
different modes as a result the battery power is
conserved. Zigbee networks are extendable with
the use of routers and allow many nodes to
interconnect with each other for building a wider
area network.

Zigbee Architecture
Zigbee system structure consists of three different
types of devices such as
 Zigbee coordinator,
 Router
 End device.

Every Zigbee network must consist of at least
one coordinator which acts as a root and bridge
of the network. The coordinator is responsible for
handling and storing the information while
performing receiving and transmitting data
operations. Zigbee routers act as intermediary
devices that permit data to pass to and fro
through them to other devices. End devices have
limited functionality to communicate with the
parent nodes such that the battery power is
saved as shown in the figure. The number of
routers, coordinators and end devices depends
on the type of network such as star, tree and

zigbee protocol architecture consists of a stack of
various layers where IEEE 802.15.4 is defined by
physical and MAC layers while this protocol is
completed by accumulating Zigbee’s own network
and application layers.

 Physical Layer: This layer does modulation and
demodulation operations up on transmitting and
receiving signals respectively. This layer’s frequency,
date rate and number of channels are given below.

 MAC Layer: This layer is responsible for reliable
transmission of data by accessing different networks
with the carrier sense multiple access collision
avoidance (CSMA). This also transmits the beacon
frames for synchronizing communication.
 Network Layer: This layer takes care of all network
related operations such as network setup, end device
connection and disconnection to network, routing,
device configurations, etc.

 Application Support Sub-Layer: This layer enables
the services necessary for Zigbee device object and
application objects to interface with the network
layers for data managing services. This layer is
responsible for matching two devices according to
their services and needs.
 Application Framework: It provides two types of
data services as key value pair and generic message
services. Generic message is a developer defined
structure, whereas the key value pair is used for
getting attributes within the application objects. ZDO
provides an interface between application objects
and APS layer in Zigbee devices. It is responsible for
detecting, initiating and binding other devices to the
network.

Zigbee Operating Modes and Its
Topologies
Zigbee two way data is transferred in two modes:
Non-beacon mode and Beacon mode.
In a beacon mode, the coordinators and routers
continuously monitor active state of incoming
data hence more power is consumed. In this
mode, the routers and coordinators do not sleep
because at any time any node can wake up and
communicate. However, it requires more power
supply and its overall power consumption is low
because most of the devices are in an inactive
state for over long periods in the network.

 In a beacon mode, when there is no data communication
from end devices, then the routers and coordinators enter
into sleep state. Periodically this coordinator wakes up and
transmits the beacons to the routers in the network. These
beacon networks are work for time slots which means,
they operate when the communication needed results in
lower duty cycles and longer battery usage. These beacon
and non-beacon modes of Zigbee can manage periodic
(sensors data), intermittent (Light switches) and repetitive
data types.

Network topologies
 Zigbee supports several network topologies;
however, the most commonly used configurations
are star, mesh and cluster tree topologies. Any
topology consists of one or more coordinator. In a
star topology, the network consists of one
coordinator which is responsible for initiating and
managing the devices over the network. All other
devices are called end devices that directly
communicate with coordinator. This is used in
industries where all the end point devices are
needed to communicate with the central
controller, and this topology is simple and easy to
deploy.

Applications of Zigbee Technology
 industrial Automation: In manufacturing and
production industries, a communication link
continually monitors various parameters and critical
equipments. Hence Zigbee considerably reduce this
communication cost as well as optimizes the control
process for greater reliability.
 Home Automation: Zigbee is perfectly suited
for controlling home appliances remotely as a lighting
system control, appliance control, heating and cooling
system control, safety equipment operations and
control, surveillance, and so on.
 Smart Metering: Zigbee remote operations in smart
metering include energy consumption response,
pricing support, security over power theft, etc.
 Smart Grid monitoring: Zigbee operations in this
smart grid involve remote temperature monitoring,
fault locating, reactive power management, and so
on.

6LoWPAN
PAN provides the upper layer system for use with
low power wireless communications for IoT and
M2M, originally intended for 802.15.4, it is now
used with many other wireless standards.

 WPAN system is used for a variety of applications
including wireless sensor networks. This form of wireless
sensor network sends data as packets and using IPv6 -
providing the basis for the name - IPv6 over Low power
Wireless Personal Area Networks.
 6LoWPAN provides a means of carrying packet data in the
form of IPv6 over IEEE 802.15.4 and other networks. It
provides end-to-end IPv6 and as such it is able to provide
direct connectivity to a huge variety of networks including
direct connectivity to the Internet.
 In this way, 6LoWPAN adopts a different approach to the
other low power wireless sensor network solutions.

 6LoWPAN was originally conceived to build on top of
IEEE 802.15.4, a standard that set out the lower
layers for a 2.4 GHz low power wireless system, it is
now being developed and adapted to work with many
other wireless bearers including Bluetooth Smart;
power line control, PLC, and low power Wi-Fi.
 The 6LoWPAN group have then defined the
encapsulation and compression mechanisms that
enable the IPv6 data to be carried of the wireless
network.
 The development of the 6LoWPAN system was not
as easy as might be thought as the basic natures of
the two systems are very different. However it was
believed that using packet data over a low power
wireless sensor network would offer significant
advantages in terms of data handling and

WPAN application areas
 any low power wireless sensor networks and
other forms of ad hoc wireless networks, it is
necessary that any new wireless system or
technology has a defined area which it
addresses. While there are many forms of
wireless networks including wireless sensor
networks, 6LoWPAN addresses an area that is
currently not addressed by any other system, i.e.
that of using IP, and in particular IPv6 to carry the
data.
 The overall system is aimed at providing wireless
internet connectivity at low data rates and with a
low duty cycle. However there are many
applications where 6LoWPAN is being used:

 LoWPAN technology utilizes IEEE 802.15.4 to provide the lower
layers for this low power wireless network system. While this
seems a straightforward approach to the development of an
packet data wireless network or wireless sensor network, there
are incompatibilities between IPv6 format and the formats
allowed by IEEE 802.15.4. This differences are overcome within
6LoWPAN and this allows the system to be used as a layer over
the basic 802.15.4.
 In order to send packet data, IPv6 over 6LowPAN, it is necessary
to have a method of converting the packet data into a format that
can be handled by the IEEE 802.15.4 lower layer system.
 IPv6 requires the maximum transmission unit (MTU) to be at
least 1280 bytes in length. This is considerably longer than the
IEEE802.15.4's standard packet size of 127 octets which was set
to keep transmissions short and thereby reduce power
consumption.
 To overcome the address resolution issue, IPv6 nodes are given
128 bit addresses in a hierarchical manner. The IEEE 802.15.4
devices may use either of IEEE 64 bit extended addresses or 16
bit addresses that are unique within a PAN after devices have
associated. There is also a PAN-ID for a group of physically co-
located IEEE802.15.4 devices.

Lecture 15

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Lecture 15