Learn About Sensor network

Globalization, rising energy prices, and a strict regulatory environment are driving companies in a wide variety of industries to cut costs while increasing efficiency and productivity. Changes in organizational infrastructure and processes are being made in order to stay competitive.

Meanwhile, trying to meet production and profitability goals still remains a significant organizational hurdle. Given these market dynamics, industry leaders are feeling pressure to adopt new technologies that will help them gain competitive advantages wherever they can find them.

Recent advances in wireless sensor networking leverage the capabilities of existing monitoring and control infrastructure to areas not possible before, more than doubling the available monitoring points at a lower cost per point than current wired solutions.

Wireless sensor networks connect critical process asset (valves, motors, bearings) with the systems or experts that can interpret the data and take corrective action.

Utilizing mesh networking technologies, wireless sensor networks ensure reliable wireless connection points throughout industrial facilities.

At the end of the day, operational teams with full visibility into their processes through more connected monitoring points can prevent shutdowns and increase efficiencies while reducing the total cost of data acquisition.

Making industrial wireless viable
Industrial-grade monitoring and control applications demand extremely high reliability " typically greater than 99.9% end-to-end delivery rate.

However, as many companies have discovered, traditional point-to-point wireless networks are prone to failure when faced with the challenging and dynamic radio-frequency (RF) landscape presented by typical industrial environments.

Likewise, wireless mesh sensor networks designed for consumer-grade applications such as home automation, PC peripherals, and remote controls are often inadequate for applications that require high levels of reliability and low user intervention for the entire life of the network.

Any viable wireless solution must be designed from the ground-up to meet the unique challenges of industrial monitoring and control. Several companies and organizations, including the HART Foundation, are working to define the specific requirements of industrial markets and applications.

Reliability is invariably at the top of every list. This is an absolute requirement for any monitoring technology " if the data is not reliable then the economic benefits of low install cost are irrelevant.

Specifically, for a wireless technology to be reliable in industrial applications it must:

• Function in harsh industrial environments with unpredictable EMI, RF fading and multi-path interference
• Co-exist in the field with other wireless devices such as Wi-Fi, RFID, walkie-talkies, instant connect phones, pagers, cell phones, remote controls and other wireless data networks
• Survive single-point failures or blocked communication paths without impacting end-to-end performance

Wireless sensor networks are uniquely capable of adapting to these challenges. With a network architecture designed to protect against these issues, wireless mesh sensor networks 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. There are three fundamental techniques that enable a reliable, resilient wireless mesh sensor network: redundant routes, frequency hopping and packet-level integrity checks. This paper will discuss each of these techniques and how they contribute to long-term reliable operation.

Redundant routes

Unlike wired networks, these variables often change and paths may later be blocked by new equipment, partitions, or even delivery trucks. The network must continually work around these blockages in a transparent and automatic fashion to assure reliability for the life of the network, not just the first few weeks after installation.

Wireless sensor networks using a mesh topology address single points of failure by building redundant routes all the way to the network's edge.

Traditional wired networks and some wireless networks use star or cluster-tree topologies, but mesh networks by definition work so that each mote, a battery-operated wireless sensor networking device, communicates with multiple neighbors, which ensures reliable, end to end communication, even when any single point-to-point link is compromised.

Think about the hammock in your backyard: if you cut one string, the hammock can still support a whole load. Same with a mesh network; one broken link does not hinder successful packet delivery across the network.

So if one path is blocked by a newly installed machine, that mote will utilize its other neighbors to ensure successful packet delivery regardless of the blocked path.

Each mote in the network communicates regularly with at least two parents; if a wireless link to one parent is interrupted, all the child's traffic is simply passed through the other parent.

If an interrupted path remains unavailable for an extended period, the mote will connect to an alternate neighbor that is also within range, re-establishing redundancy. This type of autonomous healing and routing is the only way to achieve long-term stability and reliability.

Another critical feature of wireless mesh sensor networks is that they are self-organizing. In other words, they form redundant links without requiring complex planning, installation, and configuration.

Motes interconnect based on the actual characteristics of the environment rather than an expensive and potentially out-of-date RF survey. Additionally, extending a sensor network is as simple as placing new motes; no follow-on capacity planning or RF surveys are required.