As sensors in a sensor node typically measure slow varying analog quantities, nodes need only be active for a short duration to transmit data before they go back to sleep. This means that sensor nodes have to have excellent standby current capabilities. Also, most of the data transmission occurs between the sensor nodes to the base station.
Network architecture and communication protocols must exploit this asymmetry of sensor communication from sensor node to base station. Design of a low power sensor is critical. Micro Electro Mechanical Systems (MEMS) based sensors with low power capabilities are also critical. Sensor nodes may operate in an environment of densely distributed nodes from different sources. Sensor nodes may also need to transmit using very low power in noisy environments.
Aggregation of data from sensor nodes
The data from a sensor network must be aggregated and processed in a centralized location. Data handling in a sensor network can be split into data dissemination and data gathering. Data dissemination is the process by which information is routed in the sensor network. This information could be data acquired from the sensor or requests for data from other sensors. A number of algorithms are available for disseminating data across a sensor network. Data gathering algorithms maximize the number of communications that happen with a sensor node before the node dies. The trade off in this case is between delay and power consumption. In case of a direct transmission, every node sends collected data directly to a centralized network as in the case of nodes with GSM capabilities. Nodes of a wireless sensor network would have an operating system ported onto it. This enables an easy expansion through the addition of more wireless sensors. The operating systems for sensor networks resemble embedded operating systems since they are developed keeping an application in mind and are