Wireless Sensor Age - Gearing Up!

Recent advances in MEMS technology have made SoC(system on chip) very popular. SoC means presence of CPU, memory embedded on a single chip. Sensor node is one that comes under SoC. Each node consists of a microcontroller (CPU + RAM), flash storage, battery, sensors and radio for transmitting and receiving. Collection of such nodes forming a self-Organized network is called a Wireless Sensor Network (WSN). These nodes are generally deployed in inaccessible regions where there is a chance of little human intervention. Each node can do computation, storage, sensing and communication.

Every node can measure real world variables like temperature, pressure, humidity, motion speed etc. Flash storage in each node is used to store the data generated by sensing the environment. This data is communicated to a base station which is located at the user end. Base station is a typical desktop computer which collects data sent by the nodes. Every node need not communicate directly with the base station. This is due to presence of radio which has a only range from 10 to 100 meters. The data is moved to base station using multi-hop communication. Multi-hop communication means each node sending data to its neighbors (nodes which are in its radio range) and neighbors to their neighbors and so on till the data reaches the base station. Battery is the power source of every node. Nodes will switch often to sleep mode to conserve their power.

Wireless Sensor Network can be viewed as a distributed data base where each node is a data site. User issues queries from the base station to get the data stored in the network. Nodes process these queries and sends data to the base station. While sending data, nodes aggregate their data with their neighbors to reduce the amount of transmitting data. This is important because transmission operation consumes more energy.

WSN is used in many applications like habitat monitoring, forest fire detection, environmental monitoring, smart homes, supply chain monitoring, health monitoring, surveillance and tracking etc.