This technology, developed at Vanderbilt University’s Institute for Software Integrated Systems, uses radio interferometry to locate tangible objects and attains, simultaneously, a higher degree of accuracy (within 3 centimeters), considerably longer range (up to 160 meters) and lower cost than other technologies.
Challenges in sensor localization for wireless sensor networks (WSN)
- Most WSN applications require the knowledge of the location of individual nodes that form the network
- Although GPS and acoustic ranging are used for this, robust sensor localization is still an unresolved problem
- GPS technologies are relatively expensive and not accurate enough for many applications, whereas acoustic ranging technologies are more accurate, but have limited range
- Ultrasound, the only option for applications that require stealth, have limited range and directionality constraints
- Traditional radio based methods typically rely on received signal strength that is relatively accurate over short distances (with extensive calibration), but are imprecise beyond a few meters and are very expensive
The novel idea behind the proposed technology is that it utilizes two simple transmitters to create the interference signal directly. If the frequencies of the two emitters are almost the same, the composite signal will have a low frequency envelope that can be measured by modestly priced and simple hardware readily available on a WSN node. Relative phase offset of the signal at two receivers is then used, which is a function of the relative positions of the four nodes involved and the carrier frequency. By making multiple measurements in a network that contains a minimum of seven nodes, it is possible to reconstruct the relative location of the nodes in three dimensions.
In addition to wireless sensor networks, this technique is equally relevant to any application that requires highly accurate, three dimensional positioning including structural engineering, sports and robotics.
Intellectual Property and Product Development Status
- U.S. Patent number 7,558,583
- Prototype implementation runs on the XBow MICA2 platform and yields an average localization error as small as three centimeters and a range of up to 160 meters
- Vanderbilt collaborated with the Oak Ridge National Laboratory to showcase this technology during a “Dirty Bomb Detection and Localization” demonstration at the Vanderbilt stadium. This technology was used to track a plain clothes security guard who circulated through the stadium with a cell phone-integrated radiation detector both on a television monitor and on a Google Earth™ user-interface
- More details and Demonstration videos are available at: http://www.isis.vanderbilt.edu/projects/rips