LET-to-Camera Communication for Smartphones


Towards “intuitive” communication, which allows a user to directly obtain information from a device in the user interest, we are developing IoTorch, a flexible LED-to-camera communication for smartphones. IoTorch have two communication modes: 1) a long-range mode that supports several 10 bps of transmission even when an LED appears only few pixels to a smartphone, and 2) a short-range mode that supports several 1000 bps when an LED occupies an entire screen of a smartphone. In a long-range mode, IoTorch can receive the information regardless of the time at which the camera is started by adding information to the differential color shift between consecutive frames. On the other hand, in a short-range mode, IoTorch realizes fast and reliable communication by a minimum-repetition one-way transmission method considering characteristics of a rolling shutter system. By combining these modes, the user can specify a desired information source through the screen of the smartphone from long-range, and can obtain detailed information by approaching the device.