01-12-2012, 01:21 PM
THE ROLE OF ZIGBEE TECHNOLOGY IN FUTURE DATA COMMUNICATION SYSTEM
1THE ROLE OF ZIGBEE.pdf (Size: 129.66 KB / Downloads: 302)
ABSTRACT
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. 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.
ZigBee is a low-cost, low-power, wireless mesh networking standard. The low cost allows the technology
to be widely deployed in wireless control and monitoring applications, the low power-usage allows longer
life with smaller batteries, and the mesh networking provides high reliability and larger range.ZigBee has
been developed to meet the growing demand for capable wireless networking between numerous lowpower
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.
INTRODUCTION
ZigBee is an established set of specifications for
wireless personal area networking (WPAN), i.e.
digital radio connections between computers and
related devices. 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. The ZigBee Alliance, the standards
body which defines ZigBee, also publishes
application profiles that allow multiple OEM
vendors to create interoperable products.
ARCHITECTURE
ZigBee is a home-area network designed
specifically to replace the proliferation of
individual remote controls. ZigBee was created to
satisfy the market's need for a cost-effective,
standards-based wireless network that supports low
data rates, low power consumption, security, and
reliability. To address this need, the ZigBee
Alliance, an industry working group
(www.zigbee.org), is developing standardized
application software on top of the IEEE 802.15.4
wireless standard. The alliance is working closely
with the IEEE to ensure an integrated, complete,
and interoperable network for the market. For
example, the working group will provide
interoperability certification testing of 802.15.4
systems that include the ZigBee software layer.
The ZigBee Alliance will also serve as the official
test and certification group for ZigBee devices.
ZigBee is the only standards-based technology that
addresses the needs of most remote monitoring and
control and sensory network applications.
DEVICE TYPES
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.
ZigBee networks use three device types:
• The network coordinator maintains overall
network knowledge. It's the most
sophisticated of the three types and
requires the most memory and computing
power.
• The full function device (FFD) supports all
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's generally found in network-edge
devices.
CHANNEL ACCESS, ADDRESSING
Two channel-access mechanisms are implemented
in 802.15.4. For a non"beacon network, a standard
ALOHA CSMA-CA (carrier-sense medium-access
with collision avoidance) communicates with
positive acknowledgement for successfully
received packets. In a beacon-enabled network, a
superframe structure is used to control channel
access. The superframe is set up by the network
coordinator to transmit beacons at predetermined
intervals (multiples of 15.38ms, up to 252s) and
provides 16 equal-width time slots between
beacons for contention-free channel access in each
time slot. The structure guarantees dedicated
bandwidth and low latency. Channel access in each
time slot is contention-based. However, the
network coordinator can dedicate up to seven
guaranteed time slots per beacon interval for quality
of service.
CONLUSION
It is likely that ZigBee will increasingly play an
important role in the future of computer and
communication technology. 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). 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 and very
fast market adoption.