Date Added: Jul 2011
A wireless sensor network consists of a group of sensor nodes that broadcast the sensed data to the base station hop by hop via radio frequency. It is useful only if the sensed data are associated with the locations of the sensor nodes. Therefore, location estimation of sensor nodes has become an important issue. Ideally, each sensor node can obtain its location by being equipped with a GPS device. However, this approach costs too much, contradicting the objective of low cost sensor nodes. Hence, it is reasonable that a few sensor nodes only are equipped with a GPS device, and the others estimate their own locations by way of the collected information.