Ultrasonic Time Synchronization and Ranging on Smartphones
Patrick Lazik, Niranjini Rajagopal, Anthony Rowe, Bruno Sinopoli

Citation
Patrick Lazik, Niranjini Rajagopal, Anthony Rowe, Bruno Sinopoli. "Ultrasonic Time Synchronization and Ranging on Smartphones". Real-Time and Embedded Technology and Applications Symposium, IEEE (ed.), 108-118, 13, April, 2015.

Abstract
In this paper, we present the design and evaluation of a platform that can be used for time synchronization and indoor positioning of mobile devices. The platform uses the Time- Difference-Of-Arrival (TDOA) of multiple ultrasonic chirps broadcast from a network of beacons placed throughout the environment. These chirps encode identification data and ranging information that can be used to compute the receiver's location. Our platform uses RF-based time synchronization to distribute clock synchronization from a subset of infrastructure nodes connected to a GPS source. Mobile devices use a novel time synchronization technique where signals from multiple ultrasonic transmitters can be used to synchronize the audio sampling subsystem of a smartphone with global time. Once synchronized, the devices can perform Time-Of-Flight (TOF) ranging from a single node. This significantly decreases the number of beacons required to cover an indoor space and improves performance in the face of obstructions. We show through experiments that this approach outperforms NTP on smartphones by an order of magnitude, pro- viding sub 100μs synchronization accuracy with clock drift rates as low 2ppm. The beacon platform also includes a microphone for node-to-node ranging. This can help auto- mate deployment and reduce error associated with incorrect transmitter geometries.

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Citation formats

• HTML

  Patrick Lazik, Niranjini Rajagopal, Anthony Rowe, Bruno
  Sinopoli. <a
  href="http://www.terraswarm.org/pubs/492.html"
  >Ultrasonic Time Synchronization and Ranging on
  Smartphones</a>, Real-Time and Embedded Technology and
  Applications Symposium, IEEE (ed.), 108-118, 13, April, 2015.

• Plain text

  Patrick Lazik, Niranjini Rajagopal, Anthony Rowe, Bruno
  Sinopoli. "Ultrasonic Time Synchronization and Ranging
  on Smartphones". Real-Time and Embedded Technology and
  Applications Symposium, IEEE (ed.), 108-118, 13, April, 2015.

• BibTeX

  @inproceedings{LazikRajagopalRoweSinopoli15_UltrasonicTimeSynchronizationRangingOnSmartphones,
      author = {Patrick Lazik and Niranjini Rajagopal and Anthony
                Rowe and Bruno Sinopoli},
      title = {Ultrasonic Time Synchronization and Ranging on
                Smartphones},
      booktitle = {Real-Time and Embedded Technology and Applications
                Symposium},
      editor = {IEEE},
      pages = {108-118},
      day = {13},
      month = {April},
      year = {2015},
      abstract = {In this paper, we present the design and
                evaluation of a platform that can be used for time
                synchronization and indoor positioning of mobile
                devices. The platform uses the Time-
                Difference-Of-Arrival (TDOA) of multiple
                ultrasonic chirps broadcast from a network of
                beacons placed throughout the environment. These
                chirps encode identification data and ranging
                information that can be used to compute the
                receiver's location. Our platform uses RF-based
                time synchronization to distribute clock
                synchronization from a subset of infrastructure
                nodes connected to a GPS source. Mobile devices
                use a novel time synchronization technique where
                signals from multiple ultrasonic transmitters can
                be used to synchronize the audio sampling
                subsystem of a smartphone with global time. Once
                synchronized, the devices can perform
                Time-Of-Flight (TOF) ranging from a single node.
                This significantly decreases the number of beacons
                required to cover an indoor space and improves
                performance in the face of obstructions. We show
                through experiments that this approach outperforms
                NTP on smartphones by an order of magnitude, pro-
                viding sub 100μs synchronization accuracy with
                clock drift rates as low 2ppm. The beacon platform
                also includes a microphone for node-to-node
                ranging. This can help auto- mate deployment and
                reduce error associated with incorrect transmitter
                geometries.},
      URL = {http://terraswarm.org/pubs/492.html}
  }
  

Posted by Anthony Rowe on 8 Feb 2015.