Wireless sensor networks are becoming very popular technology; however it is very important to understand the architecture for this kind of network before deploying it in any application.
A wireless sensor network consists of automatic sensors which will monitor either physical or environmental conditions. These include temperature, sound, vibration, pressure, humidity, motion or pollutants. They then send data through the network back to the main location.
It is built from nodes and they can range in number from hundreds to thousands within the network. These nodes contain several parts including a radio transceiver with an internal antenna or connection to an external antenna, a microcontroller, an electronic circuit for interfacing with the sensors and an energy source which may be a battery or an embedded form of energy harvesting.
The most common structure of WSN's follows the OSI model. There are 5 layers needed in the network including an application layer, transport layer, network layer, data link layer and a physical layer.
It is also made up of cross planes/layers which include power management plane, mobility management plane and task management plane. These are used to manage the network and make the sensors work together in the correct order to increase efficiency.
The WSN is installed over a region where some phenomenon is to be monitored. An example is the use of sensors to detect enemy intrusion; a civilian example is the geo-fencing of gas or oil pipelines.
When the sensors detect the event being monitored (heat, pressure), the event is reported to one of the base stations.
Environmental Sensor Networks has evolved to cover many applications of WSNs to earth science research. This includes sensing volcanoes, oceans, glaciers, forests etc.
Air pollution monitoring
WSN's have been deployed in several cities including Stockholm, London and Brisbane, to monitor the concentration of dangerous gases. These can take advantage of the ad-hoc wireless links rather than wired installations, which also make them more mobile for testing in different areas.
They can be used to control the temperature and humidity levels inside commercial greenhouses. When the temperature and humidity drops below certain levels, the greenhouse manager must be notified via e-mail or cell phone text message, or host systems can trigger misting systems, open vents, turn on fans, or control a wide variety of system responses.
Machine health monitoring
Wireless sensor networks have been developed for machinery condition-based maintenance (CBM) as they offer significant cost savings and enable new functionalities. In wired systems, the installation of enough sensors is often limited by the cost of wiring. Previously inaccessible locations, rotating machinery, hazardous or restricted areas, and mobile assets can now be reached with wireless sensors.
WSN's can be used for the collection of data for monitoring environmental information, this can be as simple as the monitoring of the temperature in a fridge to the level of water in overflow tanks in nuclear power plants. The data can then be used to show how systems have been working.
There are many opportunities for using wireless sensor networks within the water/wastewater industries. Facilities not wired for power or data transmission can be monitored using industrial wireless I/O devices and sensors powered using solar panels or battery packs can also be used in pollution control.
These are just a few of the uses for WSN's, the list goes on.
Wireless communicationscompared with wired solutions means you are able to reduce implementation costs, become more energy efficient and reach sensors in remote locations.