A variety of systems have been proposed that call for the ability for wireless sensor networks (WSNs) to determine the location of a node within a wireless communication system. For example, in asset control, it is desirable to know the locations of objects (e.g., laptop computers, cell phones, shipping containers with a built-in sensor node, shared hospital equipment with either an attached or built-in sensor node, . . . , etc.) within the confines of, say, an office building, factory floor, or other general or specialized space. Unfortunately, many location applications for wireless sensor networks are characterized by their severe resource constraints (e.g. energy, bandwidth, processing power, and memory), which have a considerable impact on the location performance. For example, many WSN applications require very long lifetime to avoid frequent re-charging or battery replacement. A difficulty in designing an efficient location technique is managing the tradeoff between resource usage and the location performance. Minimizing resource consumption leads to degradation in location accuracy, while increasing resource consumption leads to a more accurate location estimate. Therefore a need exists for a method and apparatus for determining the range and location of a node within a wireless communication system that balances resource constraints with location accuracy.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. Those skilled in the art will further recognize that references to specific implementation embodiments such as “circuitry” may equally be accomplished via replacement with software instruction executions either on general purpose computing apparatus (e.g., CPU) or specialized processing apparatus (e.g., DSP). It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.