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Competitive pressures, globalization, rising energy prices, and increasingly stringent regulations are driving companies to cut costs while increasing efficiency and productivity. Industry leaders feel pressure to adopt new technologies that will help them gain competitive advantages wherever they can find them. One of these promising new technologies is wireless sensor networking.
Wireless sensor networks (WSNs) dramatically reduce the cost of installing and commissioning instrumentation in industrial facilities. More instrumentation means better visibility into operational and environmental variables that affect overall uptime, safety, and compliance.
WSNs connect critical processes and assets with the systems or experts that can interpret the data or take immediate action. At the end of the day, operational teams with more visibility into their processes can prevent unplanned shutdowns, increase efficiency, and keep workers safe.
WSN is a term used to describe an emerging class of embedded communication products that provide redundant, fault-tolerant wireless connections between sensors, actuators and controllers or systems. WSNs provide access to assets or instruments that were previously deemed unreachable due to physical or economic barriers.
The WSN label typically describes products that provide performance above and beyond traditional point-to-point solutions, particularly in areas of fault tolerance, power consumption and installation cost.
Wireless Challenges
While wireless provides clear cost and flexibility advantages, it also presents some challenges. Point-to-point radio communication links are notoriously variable and unpredictable.
A link that is strong today may be weak tomorrow due to environmental conditions, new obstacles, unanticipated interferers and myriad other factors. These factors can be boiled down into three major failure modes: RF interference, changes in the physical environment that block communication links, and loss of individual nodes.
RF interference: The small portion of the electromagnetic spectrum devoted to general-purpose wireless communication devices is crowded with traffic from Wi-Fi networks, cordless telephones, bar-code scanners, and innumerable other devices that can interfere with communications. Because there is no way to predict what interferers will be present in a facility at a given location, frequency, and time, a reliable network must be able to continually sidestep these interferers on an ongoing basis.
Blocked Paths: When a network is first deployed, wireless paths are established between devices based on the immediate RF environment and available neighbors. Unlike wired networks, these variables often change; paths may later be blocked by new equipment, repositioned partitions, delivery trucks, or very small changes in device position.
Assuring reliability for the life of the network, not just the first few weeks after installation, requires continually working around these blockages in a transparent, automatic fashion.
Node Loss: Node loss is an important issue to consider with wireless sensor networks. While node failure because of semiconductor or hardware malfunction is rare, nodes may be damaged, destroyed or removed during the life of the network.
Additionally, power surges, blackouts, or brownouts can cause nodes to fail unless they have an independent power source. End-to-end reliability requires the networking intelligence that routes around the loss of any single node.
Any of these problems will bring down a point-to-point wireless link. However, with a network architecture designed to protect against these issues, the network can isolate individual points of failure and eliminate or mitigate their impact, allowing the network as a whole to maintain very high end-to end reliability in spite of local failures.
Similarly, a well-designed wireless network architecture will transparently adapt to changing environments, allowing long-term operation with zero-touch maintenance.
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