The IEEE article “Overview of Sensor Networks” (Aug 2004) provides a concise summary on what wireless sensor networks are, their applications, and the challenges in their design.  Wireless sensor networks are collections of small computing devices with some sensing ability constrained by low computing capability and low energy restrictions.  Each device is ineffective on its own, but the overall interactions and behavior of the sensor network can produce results far superior to a single, high-performance device.

The primary application of wireless sensor networks is the monitoring of environmental processes.  This could range across anything from environmental monitoring to security to equipment maintenance.  The example given in the article is the monitoring of the ecosystem that exists in and around one redwood tree.  A network of sensors was positioned along the length of tree in various locations, measuring temperature, barometric pressure, and humidity, along with several other environmental factors.  Every five minutes, the sensors would collect data on these various environmental conditions and then transmit it to the base node.  The base node would process it and transmit it to the outside world, where the researchers could do further analysis on the data.

Several of the challenges involved in sensor networks include the complexity of the individual interactions among all the nodes, the sheer number of nodes, and the limited computing and power capabilities of each node.  The high number of nodes in the sensor network, along with limited communication among them, require that the nodes be self-organizing.  There is no central control unit that maintains and tends to every individual node.  The nodes must communicate among each other to organize themselves in order to accomplish their overall task.  In the example above, there was in fact a central processing node that handled the computations and managed the sensor nodes, but in a more advanced sensor network, the network would be large enough such that a central node would not be feasible.  Another challenge is the power limitations and computing limitations of each node.  Each node must be inexpensive and small, which restricts the individual capability of each node.  Thus, they will end up relying on each other to make up for their individual limitations.  For example, nodes in a sensor network will generally be in some sort of “sleep” mode to conserve power, and only activate when required, as communicated by neighboring nodes.

Wireless sensor networks are part of an emerging field in wireless information networks that are made possible because of the miniaturization of electronics along with advances in algorithms designed to handle networks.  Although this course is mostly concerned with social networks, the same principles and ideas surrounding social networks, along with their challenges and obstacles, can be applied to wireless sensor networks.