Many mobile-phone applications (apps) use spatial positioning technology to present their user with location-specific information such as directions to nearby amenities.
By simultaneously predicting the location of the mobile-user and the data access points, or hotspots, improved accuracy of positioning is now available, thanks to an international research team including Sinno Jialin Pan from the A*STAR Institute for Infocomm Research1. Software developers expect that such improvements will enable a whole new class of apps that can react to small changes in position.
Traditionally, device position was determined by the Global Positioning System (GPS) that uses satellites to triangulate approximate location, but its accuracy falters when the mobile device is indoors. An alternative approach is to use the ‘received signal strength’ (RSS) from local transmitters. Attenuation of radio waves by walls can limit accuracy; and, it is difficult to predict signals in complex, obstacle-filled environments.
Software developers have tried to circumvent these problems by using so-called ‘learning-based techniques’ that identify correlations between RSS values and access-point placement. Such systems do not necessarily require prior knowledge of the hotspot locations; rather they ‘learn’ from data collected on a mobile device. This also has drawbacks: the amount of data can be large, making calibration time consuming. Changes in the environment can also outdate the calibration.
Pan and his co-workers reduced this calibration effort in an experimental demonstration of a protocol that calculates both the positions of the device and the access points simultaneously — a process they call colocalization. “Integrating the two location-estimation tasks into a unified mathematical model means that we can fully exploit the correlations between mobile-device and hotspot position,” explains Pan.
First, the researchers trained a learning-based system with the signal-strength values received from access points at selected places in the area of interest. They used this information to calibrate a probabilistic ‘location-estimation’ system. Then, they approximated the location from the learned model using signal strength samples received in real-time from the access points.
Experimental trials showed that this approach not only required less calibration, but it was more accurate than other state-of-the-art systems. “We next want to apply the method to a larger-scale environment,” says Pan. “We also want to find ways to make use of the estimated locations to provide more useful information, such as location-based advertising.” As this technique could help robots navigate by themselves, it may also have important implications for the burgeoning field of robotics.
The A*STAR-affiliated researchers contributing to this research are from the Institute for Infocomm Research
Pan, J. J., Pan, S. J., Yin, J., Ni, L. M. & Yang, Q. Tracking mobile users in wireless networks via semi-supervised colocalization. IEEE Transactions on Pattern Analysis and Machine Intelligence 34, 587–600 (2012).
More articles from Information Technology:
Wayne State University researcher’s technique helps robotic vehicles find their way, help humans
15.05.2013 | Wayne State University - Office of the Vice President for Research
DMTF, ETSI, OASIS, OCEAN, OGF, OW2 and SNIA announce Cloud Interoperability Week
15.05.2013 | FOKUS - Fraunhofer-Institut für Offene Kommunikationssysteme
University of Würzburg physicists have succeeded in creating a new type of laser.
Its operation principle is completely different from conventional devices, which opens up the possibility of a significantly reduced energy input requirement. The researchers report their work in the current issue of Nature.
It also emits light the waves of which are in phase with one another: the polariton laser, developed ...
Innsbruck physicists led by Rainer Blatt and Peter Zoller experimentally gained a deep insight into the nature of quantum mechanical phase transitions.
They are the first scientists that simulated the competition between two rival dynamical processes at a novel type of transition between two quantum mechanical orders. They have published the results of their work in the journal Nature Physics.
“When water boils, its molecules are released as vapor. We call this ...
Researchers have shown that, by using global positioning systems (GPS) to measure ground deformation caused by a large underwater earthquake, they can provide accurate warning of the resulting tsunami in just a few minutes after the earthquake onset.
For the devastating Japan 2011 event, the team reveals that the analysis of the GPS data and issue of a detailed tsunami alert would have taken no more than three minutes. The results are published on 17 May in Natural Hazards and Earth System Sciences, an open access journal of ...
A new study of glaciers worldwide using observations from two NASA satellites has helped resolve differences in estimates of how fast glaciers are disappearing and contributing to sea level rise.
The new research found glaciers outside of the Greenland and Antarctic ice sheets, repositories of 1 percent of all land ice, lost an average of 571 trillion pounds (259 trillion kilograms) of mass every year during the six-year study period, making the oceans rise 0.03 inches (0.7 mm) per year. ...
About 99% of the world’s land ice is stored in the huge ice sheets of Antarctica and Greenland, while only 1% is contained in glaciers.
However, the meltwater of glaciers contributed almost as much to the rise in sea level in the period 2003 to 2009 as the two ice sheets: about one third. This is one of the results of an international study with the involvement of geographers from the University of Zurich.
21.05.2013 | Studies and Analyses
21.05.2013 | Life Sciences
21.05.2013 | Studies and Analyses
17.05.2013 | Event News
15.05.2013 | Event News
08.05.2013 | Event News