ABSTRACT
This chapter presents an overview of the advances in radio localization techniques and discusses the traditional methods the anchor nodes use to evaluate their separation distance from the target node. Location-based services have been a part of every generation, combining satellite navigation through global positioning system (GPS) with cellular-based services due to the performance degradation of GPS services in dense urban and indoor environments. Localization of a target node may be classified as cooperative or non-cooperative. Time difference of arrival is another time-based method for localization which measures the difference in time between the signals arriving at two different receivers. Radio tomographic imaging is a localization technique that does not rely on any signal transmission by the subject and in that sense may be considered a fully passive localization method. In most localization scenarios, a number of parameters must be unknown to the localizing algorithm.
