In our data-driven society, innovators and engineers are looking at the Internet of Things (IoT) as an opportunity to introduce new data collection methods that will dramatically change how organizations learn about their surroundings and respond to threats and changes - and there's at least one new technology that's making an impact.

Of course, we're talking about wireless sensor networks, or WSNs: groups of internet-enabled sensors that can be dispersed throughout a target area to provide constant feedback and data on environmental changes across a number of dimensions. In industries where timely information is critical to reducing event response times and ensuring successful incident resolution, WSNs are already playing a strong role in monitoring environments and providing immediate and actionable feedback on detected changes.

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What is a Wireless Sensor Network?

Wireless sensor networks (WSN) are a unique application of the Internet of Things that uses groups of spatially dispersed sensors to monitor environmental changes in a defined area. A WSN is made up of individual nodes that may connect to a variety of sensors, collecting data from the environment about temperature changes, sounds, pollution levels, humidity, wind and more. Sensor nodes engage in communication with other nearby nodes in the network to cooperatively facilitate the transfer of sensor data through the network and to a main location where operators receive it.

Wireless sensor networks can be constructed using a standard "wheel-and-spoke" or "star" topology, but larger implementations where sensors are significantly dispersed may use a multi-hop wireless mesh topology where data travels in multiple steps between sensor nodes before arriving at the main location. Sensor nodes have three main functions in the network:

1. To collect information from sensors
2. To transmit sensor data through the network to the main location
3. To relay sensor data from other sensor nodes through the network to the main location

Each sensor node is made up of simple components that facilitate its basic objectives: a low-powered battery or another power source, a microcontroller, an electronic circuit that connects the microcontroller to the sensors and power source and a radio transceiver to facilitate communications on the network.

Several different types of sensors can be implemented in wireless sensor networks, such as:

Inductive Proximity Sensors

Inductive proximity sensors can sense the approach of a metal target using one of three methods: change in capacitance, magnetism, or electromagnetic induction. These sensors are useful in military applications where an alert from a sensor could signal the arrival of enemy combatants in the monitored area.

Ultrasonic Sensors

Ultrasonic sensors use high-frequency sound waves to measure the distance between the sensor and its intended target. The sensor head emits a sound wave which reflects off the target and is picked up by a receiver, with the time delay used to measure distance between the sensor and its target. Ultrasonic sensors can be used to detect transparent objects in the environment or those with complex shapes.

Temperature Sensors

WSNs that monitor temperatures can be effectively deployed into forests as an early warning system for forest fires, or into corporate data centers to provide alerts when cooling functions fail and hardware is at risk of overheating. Temperature regulation is a critical requirement in many contexts and sensor networks that measure temperature do an excellent job of maintaining the ongoing status of temperature-sensitive environments.

What are the Advantages of Wireless Sensor Networks?

WSNs are Effective in Harsh or Hostile Environments

Wireless sensor networks were first developed for battlefield surveillance in military engagements, situations where building a wired network of sensor devices would essentially be impossible. These difficult conditions created a need for a wireless sensor network that could be deployed with minimal risk and used to monitor environmental conditions in the battlefield. Wireless sensor nodes can be dropped out of a plane into any target area where they immediately begin to relay data and information back to the main location for analysis.

Beyond the military context, WSNs can be useful in any case where it would be difficult or unsafe for a human to manually collect the data that the sensors would collect. For example, having a sensor node measuring water quality at the bottom of a reservoir would be safer and cheaper than checking it manually.

WSNs Offer an Easily Scaled Solution

The typical network architecture of WSNs makes them an easily scaled solution for conducting environmental surveillance. If you have deployed a number of sensor nodes to monitor a specific area and you've decided to expand your area of surveillance, you can configure additional sensor nodes to communicate on the same network and deploy them into the expanded area. There is no need to change or modify existing sensors to add new ones to your network.

WSNs Enable Long-distance Data Collection and Transmission

Each sensor node in the WSN acts as a relay station between other sensor nodes in the network and the main location where data must ultimately be transmitted. There are many implementations of WSNs where the majority of sensor nodes are completely out of the wireless connectivity range of the main location: they depend entirely on signal relays and cooperation from other nodes in the network to transmit their data.

As a result, the main location can receive data from areas that would otherwise be totally out of range. The signal relay capability makes it possible for users to collect data that would otherwise be inaccessible using WSN.

WSNs Can Anticipate Natural Disasters

Some of the most significant use cases for WSNs so far have centered around environmental and Earth sensing to develop early knowledge of changes in the environment. Researchers have effectively implemented wireless sensor networks to detect the onset of forest fires via changes in temperature, humidity, and airborne gases, and to anticipate landslides by sensing the subtle movements of soil that may precede a large landslide.

In these contexts, there is no question that WSNs can save lives with the real-time feed of data that they provide. If WSN users can anticipate landslides, they can start evacuation procedures in time to prevent casualties. If forest fires are discovered at an early stage, emergency personnel have a better chance of containing the damage while avoiding loss of life or unnecessary destruction of property.

WSNs Can Protect Hardware and Data Assets

Corporations need to implement temperature sensing in their data centers to avoid data loss and unplanned downtime that can result from an overheated server. These data centers are typically packed with servers, and the addition of new wired sensors into the environment can add a lot of additional clutter to the existing maze of cables. Wireless sensor nodes make it easier for corporations to realize the benefits of real-time temperature sensing in their data centers without adding a lot of extra cabling into the environment.

Disadvantages of Sensor Networks

Sensor networks are a relatively new technology, and while many of the initial use cases show promise that WSNs will succeed, there are still some barriers to overcome. The relatively simple functioning of sensor node devices makes these networks easy to deploy, but it also makes them vulnerable to malicious security attacks, as these sensors often lack any robust security systems. WSNs may be large and span a wide area, meaning that there are many sensor nodes that could serve as an access point to the network for a malicious attacker.

In addition to security risks, the inherent nature of WSNs introduces practical issues with their deployment. These networks are comprised of low-energy and low-range devices - they need to be inexpensive because there are frequently so many of them deployed in the same network. Some engineers have discovered that periodically toggling the power on the sensor node can extend their operational lifetime, but this practice can lead to network latency and routing overhead.

In general, this problem reflects competing needs to:

1. Use sensor nodes that have ample battery life and transmitting capabilities
2. Use sensor nodes that are inexpensive to purchase and operate

Power availability and performance will be ongoing issues for these low-power connected devices, but engineers can use the latest diagnostic tools for embedded systems to ensure that their sensor nodes are functioning as efficiently as possible and that no power is wasted.