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Established 1992 in Silicon Valley. Comit provides complete chip, board and software engineering services to customers worldwide.
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Implementing Energy Efficient Wireless Sensor Networks
Wired networks of sensors have been widely used in many
environments for monitoring and control applications,
and have contributed to failure reduction, improved
productivity, and enhanced security. However, there
are significant hurdles to the continued ubiquitous use
of wired sensor networks. High installation and
maintenance costs result in the use of fewer nodes,
compromising the overall quality of the data
reported.
Wireless sensing networks (WSN) can significantly
reduce these costs by easing installation and
eliminating cabling and connectors. A typical WSN is
scalable, consumes less power, and has a lower
long-term cost of ownership, including lower upfront
installation costs and maintenance costs.
Applications that were not possible with wired networks
are now being enabled using wireless sensor networks
including mobile sensor nodes. With advances in low
power systems, we will start to see widespread
deployment of wireless sensor networks.
Wireless Sensor Networks
System Description
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A wireless sensor network is a wirelessly operating
network consisting of spatially distributed devices
that use sensors to monitor physical or environmental
conditions. The devices are called the "nodes" of
the network.
Advantages of wireless sensor nodes include ease of
installation, self-identification, self-diagnosis,
reliability and time awareness for coordination with
other nodes. These wireless sensor nodes communicate
between themselves and to a central coordinator, which
provides a connection to the wired world where we can
collect, process, analyze the measurement data.
Together this constitutes a typical WSN system.
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L = Wireless sensor Nodes
C = Coordinator of the Wireless Sensor Network
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Data is collected at the wireless sensor node and
transmitted to the gateway directly or, if required,
forwarded to the gateway through other wireless sensor
nodes. The transmitted data is then presented to the
system by the gateway connection.
The data is then processed for real-time monitoring and
control. It could also be archived for later
analysis. A client anywhere on the internet can access
the data as well
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WMSN System
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Power Considerations
A wireless device is not really wire-free if it has to
have power delivered to it. Routing power wires
complicates deployment and dramatically increases
installation costs.
Battery operated devices are not typically maintenance
free. It is inconvenient and costly to replace
batteries on any periodic basis. Disposal of used
batteries is not a "green" proposition. Neither is
wasting power on the RF link.
In order to reap the benefits of low-cost, wireless,
green devices, we need to either eliminate the use of
batteries by converting to energy harvesters, or get
extremely long life using inexpensive batteries.
Physical Layer Standards
With many sensor manufacturers on the market today, it
is not cost-effective to make special transducers for
every network on the market. With the introduction of
the IEEE 1451 standard, it is easier for sensor
manufacturers to interface their devices to any
network. Wireless communication protocol standards such
as 802.11 (WiFi), 802.15.1 (Bluetooth), 802.15.4
(ZigBee) are being considered as some of the physical
interfaces for IEEE P1451.5.
Several network standards based on IEEE 802.15.4-2006
are currently in use. ZigBee is a mesh-networking
standard used in consumer devices, home automation and
medical data sensing. ZigBee is also being promoted by
industrial players.
WirelessHART is an extension of the HART protocol, and
is specifically designed for industrial
applications. ISA100 and 6lowpan are two additional
standards.
Wireless Sensor Network Topologies
Star network (single point to multipoint): In
this topology, a single base station can send a message
to, or receive a message from, a number of remote
nodes. The remote nodes can only send or receive a
message from the single base station; they are not
permitted to send messages to each other. The
advantages of this topology are simplicity and low
power consumption in the nodes. The disadvantage of
this is the fact that it is not robust because of its
dependence on a single node for operation.
Mesh networks: A mesh network allows for
multi-hop communication, where a single node can talk
to any other node that is within its radio transmission
range. In this type of network, if a node wants to send
a message to another node that is out of its radio
range, it can use an intermediate node to forward it to
the desired node.
Scalability and redundancy are the advantages of this
topology. The main drawback of this topology is the
unequal power dissipation across nodes that implement
multihop versus the nodes that do not.
WSNs using the mesh network topology are called WMSNs
(Wireless Mesh Sensor Networks). Due to their
advantages WMSNs are more prevalent in sensor
networking.
Given below are the salient features of WMSNs:
- Ad-hoc self forming and self healing networks
- Reliable broadcast messaging
- Guaranteed message delivery applications
- Device and service discovery
- Optional acknowledged service
- Messaging with optional responses
- Security - symmetric key with AES-128 authentication and encryption
Differentiating factors of WMSNs:
- Scalability (number of nodes)
- Distances (Node to node, network total coverage)
- Price
- Bandwidth
- Power
- Low interference
- Standards compliance
Hybrid star mesh networks: A hybrid between the
star and mesh networks provides versatility and low
power consumption. In this network topology, the lowest
power sensor nodes are not enabled with the ability to
forward messages. This allows for minimal power
consumption to be maintained. However, other nodes on
the network are enabled with multihop capability,
allowing them to forward messages from the low power
nodes to other nodes on the network.
Applications
Several electric, water and other utilities are
investigating their options to deploy WSNs as part of
their Smart Grid and Smart Environment applications.
A typical Smart Environment installation uses sensors
to monitor the environment as well as to provide
feedback on critical controlled processes, to form a
closed loop. Other applications include:
- Safety and security
- Emergency Sensing
- Access & Security
- Remote Monitoring
- Theft protection
- Healthcare applications
- Patient Monitoring
- Remote Diagnostics
- Asset management and Logistics
- Active RF-ID
- Electronic Shelf Labeling
- Asset Tracking
- Location Tracking
- Theft protection
- Building & home automation
- Building Management
- Energy Control
- Occupancy Control
- Fire Protection
- Security
- Current protection
- Measuring
- Home Control
- Remote Control
- Light Switches
- Temperature Control
- Industrial automation
Automated Meter Reading
Measuring
Detection
Alarm
Quality Control
Comit's WMSN Solutions
Using its nearly two decades of design methodology
experience, Comit provides unique green WMSN solutions
to the industry that features:
- ultra low power wireless communication technology
- affordable and differentiating wireless sensor nodes
- customized control software for a wide range of applications
If you wish to contact Comit to see how Comit can help
with your organization's needs in this area, please click
here
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