Capacity of pervasive camera based communication under perspective distortions

Abstract

Abstract-Cameras are ubiquitous and increasingly being used not just for capturing images but also for communicating information. For example, the pervasive QR codes can be viewed as communicating a short code to camera-equipped sensors and recent research has explored using screen-to-camera communications for larger data transfers. Such communications could be particularly attractive in pervasive camera based applications, where such camera communications can reuse the existing camera hardware and also leverage from the large pixel array structure for high data-rate communication. While several prototypes have been constructed, the fundamental capacity limits of this novel communication channel in all but the simplest scenarios remains unknown. The visual medium differs from RF in that the information capacity of this channel largely depends on the perspective distortions while multipath becomes negligible. In this paper, we create a model of this communication system to allow predicting the capacity based on receiver perspective (distance and angle to the transmitter). We calibrate and validate this model through lab experiments wherein information is transmitted from a screen and received with a tablet camera. Our capacity estimates indicate that tens of Mbps is possible using a smartphone camera even when the short code on the screen images onto only 15% of the camera frame. Our estimates also indicate that there is room for at least 2.5x improvement in throughput of existing screen -camera communication prototypes.

Capacity of screen–camera communications under perspective distortions

“…Let α p represent the perspective scaling of the area of an imaged screen pixel when perturbed from camera focus. We modeled this perspective scaling factor and derived a general expression for α p in [15] using camera projection theory [16], that uses the camera projection matrix which maps the location of the screen pixels from the world coordinate frame to the camera coordinate system. In the simplest case, where the screen and camera are perfectly aligned at distance d, this factor can be expressed as,…”

Experimental Demonstration of Single-Channel EEG Signal Using 32 × 32 Pixel OLED Screen and Camera

“…The adverse impacts of RF signals on human wellbeing and interferences to other medical electronic devices have been in particularly in hospitals. Moreover, it has been stated by the World Health Organization that RF has the possibility of causing cancer in humans [10][11][12][13]. The fact that VLC is more friendly to human and medical electronics is one of the main advantages of using VLC in medicinal services or healthcare.…”

Systematic scheme for performance measurement in display–camera-based sensing networks

“…3 Display-camera communication has recently gained significant attention owing to the extensive advances in mobile phone cameras. [4][5][6][7][8] In the channel transmitter, the message is encoded and modulated into an image frame, for example, a barcode image, and is presented on a conventional display. At the receiving end, a mobile camera serves as the receiver.…”