  A wireless sensor network comprises of small sensor nodes each of which
consists of a processing device, small amount of memory, battery and radio
transceiver for communication. The sensor nodes are autonomous and spatially
distributed in an area of investigation. Certain applications and protocols of
wireless sensor networks require that the sensor nodes should be aware of their
position relative to the sensor network. For it to be significant and to be of
value, the data such as temperature, humidity and pressure, gathered by sensor
nodes must be ascribed to the relative position from where it was collected.
For this to happen, the sensor nodes must be aware of their relative positions.
Traditional location finding solutions, such as Global Positioning System, are
not feasible for wireless sensor nodes due to multiple reasons. Therefore, new
methods, techniques and algorithms need to be developed to solve the problem of
location and position estimation of wireless sensor nodes. A number of
algorithms and techniques based upon different characteristics and properties
of sensor nodes have already been proposed for this purpose. This chapter
discusses the basic principles and techniques used in the localization
algorithms, categories of these algorithms and also takes a more closer look at
a few of the representative localization schemes.

Networking and Internet Architecture