Flicker-free spatial-PSK modulation scheme for vehicular image sensor communications

Abstract

This paper proposes a 2-Phase Shift Keying (2-PSK) based modulation scheme for Image Sensor Communications. The considered communication system on a car uses a couple of LED light sources for transmitting data (either two rear light sources or two front light sources) and a typical-frame-rate camera (i.e. 30fps frame rate) which is either a global shutter camera or a rolling shutter camera for receiving data; therefore a flicker-free is required. Taking advantage of a dual light-source on a car, our spatial modulation approach allows a camera decoding a complete symbol from an image. Compared to a temporal approach, our scheme avoids a data decoding procedure that a symbol is demodulated from different images at which there is a high possibility of noise difference exposed by those two images especially in vehicular movement environment. Moreover, besides being compatible to both shutter types, global shutter and rolling shutter, our additional contribution on the paper is the ability to support a camera that has a wide frame-rate variation (i.e. a camera drops the frame rate to even less than 20fps) which was considered on the Technical Consideration Document (TCD) of the on-going IEEE 802.15.7r1 Task Group. Later, some analysis and experiment results are addressed to show the performance of the proposed modulation scheme.