Investigations on Temporal Sampling and Patternless Frame Recovery for Asynchronous Display-Camera Communication

Alongside classic Visible Light Communication using LEDs and photodiodes, Optical Display-Camera Communication offers another promising way of transmitting data through visible light wirelessly: A display serves as a multi-parallel transmitter array and a camera as the corresponding receiver. Due to the high number of pixels, high data rates in the range of several Mbit/s can be achieved despite comparatively low temporal rates. A major challenge that all high rate system realizations have to overcome is the lack of synchronization between display and camera. Along with varying playback and recording behavior of the devices, this typically results in mixed recordings of display frames in the receiver, which complicates frame decoding. In this paper, we fundamentally investigate the temporal sampling process in display-camera communication. Using our improved modeling we determine the minimum temporal oversampling factor required for lossless frame acquisition, in order to maximize system efficiency in the temporal domain. We propose a solution for the synchronization problem for invisible system approaches with differential modulation, in which the original display frames are recovered from asynchronous recordings in the receiver. Experimental results show that this method works robustly even with high motion background videos and without the need for embedded synchronization markers.