Wireless sensor networks (WSNs) are networks of interconnected, battery powered, wireless sensors called motes that are placed into the physical environment.

The motes collect data from many points over an extended space. Each mote contains processing, storage, and radio-frequency sensors and antennas. Each mote “wakes up” or activates for a fraction of a second when it has data to transmit.

It then relays those data to its nearest neighbor. So, instead of every mote transmitting its data to a remote computer at a base station, the data are moved mote by mote until they reach a central computer where they can be stored and analyzed.

An advantage of a wireless sensor network is that if one mote fails, then another one can pick up the data. This process makes WSNs very efficient and reliable. Also, if the network requires more bandwidth, it is easy to boost performance by placing new motes when and where they are required.

The motes provide information that enables a central computer to integrate reports of the same activity from different angles within the network.

Therefore, the network can determine with much greater accuracy information such as the direction in which a person is moving, the weight of a vehicle, and the amount of rainfall over a field of crops.

There are many applications of wireless sensors. Nest Labs produces a “digital thermostat” that combines sensors and Web technology. The thermostat senses not only air temperature, but also the movements of people in a house.

It then adjusts room temperatures accordingly to save energy. Placing sensors in all kind of products makes the products “smart.” Smart equipment includes sensors in bridges and oil rigs that alert their human minders when they need repairs, before equipment failure occurs.

Sensors in jet engines produce data in real time on the operating performance of the engines. Sensors in fruit and vegetable cartons can track location and “sniff” the produce, warning in advance of spoilage, so shipments can be rerouted or rescheduled.

In Dubuque, Iowa, IBM has initiated a long-term project with the local government to use sensors, software, and the Internet to improve the city’s use of water, electricity, and transportation.

In a pilot project introduced in 2011, digital water meters were installed in 151 homes. These meters contain software that monitors water use and patterns. It then informs residents about ways to consume less, and it alerts them to likely leaks. The pilot program decreased water use by 65 million gallons per year in the city.