09-11-2012, 05:35 PM
Dragging the world towards wireless galaxy
[attachment=38828]
ABSTRACT
“Dragging the world towards wireless galaxy”
Various sensors are already in a broad use today as part of
different devices or as standalone devices connected to a network
usually to monitor industrial processes, equipments or installations.
The advancements in technology, wireless communications have
enhanced development of small, low power and low cost devices. Such
devices when organized into a network, present a powerful platform
that can be used in many interesting applications.
Bluetooth is a low cost, short-range, wireless technology with
small footprint, low power consumption and reasonable throughput.
Bluetooth wireless technology has become global technology
specification for “always on” wireless communication not just as a
point-to-point but was a network technology as well.
The kernel of this paper, deals about an implementation of
bluetooth based sensor networks.
Introduction
The communications capability of devices and continuous transparent
information routes are indispensable components of future oriented automation
concepts. Communication is increasing rapidly in industrial environment even at
field level.
In any industry the process can be realized through sensors and can be
controlled through actuators. The process is monitored on the central control room
by getting signals through a pair of wires from each field device in Distributed
Control Systems (DCS). With advent in networking concept, the cost of wiring is
saved by networking the field devices. But the latest trend is elimination of wires
i.e., wireless networks.
Wireless sensor networks
- networks of small devices equipped with
sensors, microprocessor and wireless communication interfaces.
In 1994, Ericsson Mobile communications, the global telecommunication
company based in Sweden, initiated a study to investigate, the feasibility of a low
power, low cost ratio interface, and to find a way to eliminate cables between
devices. Finally, the engineers at the Ericsson named the new wireless technology
as “Blue tooth” to honour the 10th century king if Denmark, Harald Blue tooth
(940 to 985 A.D).
The goals of blue tooth are unification and harmony as well, specifically
enabling different devices to communicate through a commonly accepted standard
for wire less connectivity.
Blue Tooth
Blue tooth operates in the unlicensed ISM band at 2.4 GHZ frequency band
and use frequency hopping spread spectrum technique. A typical Blue tooth device
has a range of about 10 meters and can be extended to 100meters. Communication
channels supports total bandwidth of 1 Mb / sec. A single connection supports a
maximum asymmetric data transfer rate of 721 KBPS maximum of three channels.
BLUE TOOTH – NETWORKS
In bluetooth, a Piconet is a collection of up to 8 devices that frequency hop
together. Each Piconet has one master usually a device that initiated establishment
of the Piconet, and up to 7 slave devices. Master’s Blue tooth address is used for
definition of the frequency hopping sequence. Slave devices use the master’s clock
to synchronize their clocks to be able to hop simultaneously.
A Piconet
MASTER ACTIVE SLAVE STANDBY
When a device wants to establish a Piconet it has to perform inquiry to
discover other Blue tooth devices in the range. Inquiry procedure is defined in such
a way to ensure that two devices will after some time, visit the same frequency
same time when that happens, required information is exchanged and devices can
use paging procedure to establish connection.
When more than 7 devices needs to communicate, there are two options.
The first one is to put one or more devices into the park state. Blue tooth defines
three low power modes sniff, hold and park. When a device is in the park mode
then it disassociates from and Piconet, but still maintains timing synchronization
with it. The master of the Piconet periodically broadcasts beacons (Warning) to
invite the slave to rejoin the Piconet or to allow the slave to request to rejoin. The
slave can rejoin the Piconet only if there are less than seven slaves already in the
Piconet. If not so, the master has to ‘park’ one of the active slaves first. All these
actions cause delay and for some applications it can be unacceptable for eg:
process control applications, that requires immediate response from the command
centre (central control room).
Scatternet consists of several Piconets connected by devices participating in
multiple Piconet. These devices can be slaves in all Piconets or master in one
Piconet and slave in other Piconets. Using scatternets higher throughput is
available and multi-hop connections between devices in different Piconets are
possible. i.e., The unit can communicate in one Piconet at time so they jump from
pioneer to another depending upon the channel parameter.
[attachment=38828]
ABSTRACT
“Dragging the world towards wireless galaxy”
Various sensors are already in a broad use today as part of
different devices or as standalone devices connected to a network
usually to monitor industrial processes, equipments or installations.
The advancements in technology, wireless communications have
enhanced development of small, low power and low cost devices. Such
devices when organized into a network, present a powerful platform
that can be used in many interesting applications.
Bluetooth is a low cost, short-range, wireless technology with
small footprint, low power consumption and reasonable throughput.
Bluetooth wireless technology has become global technology
specification for “always on” wireless communication not just as a
point-to-point but was a network technology as well.
The kernel of this paper, deals about an implementation of
bluetooth based sensor networks.
Introduction
The communications capability of devices and continuous transparent
information routes are indispensable components of future oriented automation
concepts. Communication is increasing rapidly in industrial environment even at
field level.
In any industry the process can be realized through sensors and can be
controlled through actuators. The process is monitored on the central control room
by getting signals through a pair of wires from each field device in Distributed
Control Systems (DCS). With advent in networking concept, the cost of wiring is
saved by networking the field devices. But the latest trend is elimination of wires
i.e., wireless networks.
Wireless sensor networks
- networks of small devices equipped with
sensors, microprocessor and wireless communication interfaces.
In 1994, Ericsson Mobile communications, the global telecommunication
company based in Sweden, initiated a study to investigate, the feasibility of a low
power, low cost ratio interface, and to find a way to eliminate cables between
devices. Finally, the engineers at the Ericsson named the new wireless technology
as “Blue tooth” to honour the 10th century king if Denmark, Harald Blue tooth
(940 to 985 A.D).
The goals of blue tooth are unification and harmony as well, specifically
enabling different devices to communicate through a commonly accepted standard
for wire less connectivity.
Blue Tooth
Blue tooth operates in the unlicensed ISM band at 2.4 GHZ frequency band
and use frequency hopping spread spectrum technique. A typical Blue tooth device
has a range of about 10 meters and can be extended to 100meters. Communication
channels supports total bandwidth of 1 Mb / sec. A single connection supports a
maximum asymmetric data transfer rate of 721 KBPS maximum of three channels.
BLUE TOOTH – NETWORKS
In bluetooth, a Piconet is a collection of up to 8 devices that frequency hop
together. Each Piconet has one master usually a device that initiated establishment
of the Piconet, and up to 7 slave devices. Master’s Blue tooth address is used for
definition of the frequency hopping sequence. Slave devices use the master’s clock
to synchronize their clocks to be able to hop simultaneously.
A Piconet
MASTER ACTIVE SLAVE STANDBY
When a device wants to establish a Piconet it has to perform inquiry to
discover other Blue tooth devices in the range. Inquiry procedure is defined in such
a way to ensure that two devices will after some time, visit the same frequency
same time when that happens, required information is exchanged and devices can
use paging procedure to establish connection.
When more than 7 devices needs to communicate, there are two options.
The first one is to put one or more devices into the park state. Blue tooth defines
three low power modes sniff, hold and park. When a device is in the park mode
then it disassociates from and Piconet, but still maintains timing synchronization
with it. The master of the Piconet periodically broadcasts beacons (Warning) to
invite the slave to rejoin the Piconet or to allow the slave to request to rejoin. The
slave can rejoin the Piconet only if there are less than seven slaves already in the
Piconet. If not so, the master has to ‘park’ one of the active slaves first. All these
actions cause delay and for some applications it can be unacceptable for eg:
process control applications, that requires immediate response from the command
centre (central control room).
Scatternet consists of several Piconets connected by devices participating in
multiple Piconet. These devices can be slaves in all Piconets or master in one
Piconet and slave in other Piconets. Using scatternets higher throughput is
available and multi-hop connections between devices in different Piconets are
possible. i.e., The unit can communicate in one Piconet at time so they jump from
pioneer to another depending upon the channel parameter.