Space division multiplexing by adaptive thresholding for uplink optical camera communication using smartphone screen

Abstract

To increase symbol rate and security at the physical layer for uplink optical camera communication from a smartphone screen to indoor camera at a distance of 3.5 m, space division multiplexing by adaptive thresholding is proposed and experimentally verified. The adaptive thresholding sets the optimal threshold for a center cell with each outer 8-cell pattern in 3x3 cells. Although the outer 8-cell pattern is estimated from conventional fixed threshold, the pattern helps to determine the threshold adaptively. The adaptive thresholding achieved 216.75 and 168.75 kilo symbol per second using 85x85 and 75x75 cells at luminance of 255 and 95, respectively.