Citation
Niranjini Rajagopal, Patrick Lazik, Anthony Rowe. "Visual Light Landmarks for Mobile Devices". The 13th ACM/IEEE Conference on Information Processing in Sensor Networks (IPSN), April 2014.

Abstract
The omni-presence of indoor lighting makes it an ideal vehicle for pervasive communication with mobile de- vices. In this paper, we present a communication scheme that enables interior ambient LED lighting systems to send data to mobile devices using either cameras or light sensors in a manner that is imperceptible to people. By exploiting rolling shutter camera sensors that are com- mon on tablets, laptops and smartphones, it is possible to detect high-frequency changes in light intensity reflected off of surfaces and in direct line-of-sight of the camera. We present a demodulation approach that al- lows smartphones to accurately detect frequencies as high as 8kHz with 0.2kHz channel separation. In order to avoid humanly perceivable icker in the lighting, our system operates at frequencies above 2kHz and compensates for the non-ideal frequency response of standard LED drivers by adjusting the light's duty-cycle. By modulating the PWM signal commonly used to drive LED lighting systems, we are able to encode data that can be used as localization landmarks. We show through experiments how a binary frequency shift keying modu- lation scheme can be used to transmit data at 1.25 bytes per second from up to 29 unique light sources simultaneously in a single collision domain. We also show how low-power tags can demodulate the same signals using a light sensor instead of a camera for low power applications.

Electronic downloads

• https://www.src.org/library/publication/p069356/. (Link to SRC publication submission)
• http://delivery.acm.org/10.1145/2610000/2602367/p249-rajagopal.pdf?ip=128.32.47.132&id=2602367&acc=ACTIVE%20SERVICE&key=CA367851C7E3CE77%2E3158474DDFAA3F10%2E4D4702B0C3E38B35%2E4D4702B0C3E38B35&CFID=688825725&CFTOKEN=69099873&__acm__=1435613172_892a35ce75

• HTML

  Niranjini Rajagopal, Patrick Lazik, Anthony Rowe. <a
  href="http://www.terraswarm.org/pubs/253.html"
  >Visual Light Landmarks for Mobile Devices</a>,
  <i>The 13th ACM/IEEE Conference on Information
  Processing in Sensor Networks (IPSN)</i>, April 2014.

• Plain text

  Niranjini Rajagopal, Patrick Lazik, Anthony Rowe.
  "Visual Light Landmarks for Mobile Devices".
  <i>The 13th ACM/IEEE Conference on Information
  Processing in Sensor Networks (IPSN)</i>, April 2014.

• BibTeX

  @article{RajagopalLazikRowe14_VisualLightLandmarksForMobileDevices,
      author = {Niranjini Rajagopal and Patrick Lazik and Anthony
                Rowe},
      title = {Visual Light Landmarks for Mobile Devices},
      journal = {The 13th ACM/IEEE Conference on Information
                Processing in Sensor Networks (IPSN)},
      month = {April},
      year = {2014},
      abstract = {The omni-presence of indoor lighting makes it an
                ideal vehicle for pervasive communication with
                mobile de- vices. In this paper, we present a
                communication scheme that enables interior ambient
                LED lighting systems to send data to mobile
                devices using either cameras or light sensors in a
                manner that is imperceptible to people. By
                exploiting rolling shutter camera sensors that are
                com- mon on tablets, laptops and smartphones, it
                is possible to detect high-frequency changes in
                light intensity reflected off of surfaces and in
                direct line-of-sight of the camera. We present a
                demodulation approach that al- lows smartphones to
                accurately detect frequencies as high as 8kHz with
                0.2kHz channel separation. In order to avoid
                humanly perceivable icker in the lighting, our
                system operates at frequencies above 2kHz and
                compensates for the non-ideal frequency response
                of standard LED drivers by adjusting the light's
                duty-cycle. By modulating the PWM signal commonly
                used to drive LED lighting systems, we are able to
                encode data that can be used as localization
                landmarks. We show through experiments how a
                binary frequency shift keying modu- lation scheme
                can be used to transmit data at 1.25 bytes per
                second from up to 29 unique light sources
                simultaneously in a single collision domain. We
                also show how low-power tags can demodulate the
                same signals using a light sensor instead of a
                camera for low power applications.},
      URL = {http://terraswarm.org/pubs/253.html}
  }
  

Posted by Barb Hoversten on 9 Feb 2014.