Fine-grained acoustic positioning

The LOPSI group uses ultrasonic technology for high accuracy positioning in small indoor areas. By measuring the time-of-flight (TOF) of ultrasonic signals propagating from several static beacons to a mobile node, its position can be computed by multilateration techniques, usually with an accuracy around 1 cm.

3D-Locus is an ultrasound-based LPS designed and built by the LOPSI group and used to accurately locate archaelogical finds and transmit their position to a computer. A thorough description of the system is found here. We use this prototype system as a platform in which we develop new transducers, signal processing techniques, and positioning algorithms.

These are some of the research topics on the LOPSI group in the field of ultrasound-based positioning systems:

• Development of new ultrasonic transducers based on flexible ferroelectret materials (EMFi), in order to improve the system's bandwidth and control the transducer's directivity.

• Modulation and codification of ultrasonic signals with Code Division Multiple Access processing (CDMA) techniques, for simultaneous operation with multiple transducers and precise ranging; in essence, replicating with ultrasonic technology the main features of the GPS positioning system.

• Robust multilateration positioning in the presence of outliers in the time-of-flight measurements
  

• Autocalibration methods to determine the position of the network of beacons