Symbol Rate Maximization in Rolling-Shutter OCC: Design and Implementation Considerations

TL;DR

This paper models and experimentally investigates the maximum data rate in rolling-shutter optical camera communication systems, addressing synchronization issues and demonstrating the system's capability to operate at the Nyquist sampling rate.

Contribution

It introduces a digital communication model for rolling-shutter OCC, experimentally validates the maximum symbol rate, and characterizes ISI effects with compensation techniques.

Findings

Maximum symbol rate supported by the system is experimentally demonstrated.

Imperfect synchronization causes ISI, which can be mitigated with linear equalization.

The model accurately predicts system behavior at the Nyquist sampling rate.

Abstract

Optical Camera Communication (OCC) systems can take advantage of the row-by-row scanning process of rolling-shutter cameras to capture the fast variations of light intensity coming from Visible Light Communication (VLC) LED-based transmitters. In order to study the maximum data rate that is feasible in such kind of OCC systems, this paper presents its equivalent digital communication system model in which the rolling-shutter camera is modeled as a rectangular matched-filter whose time width is equal to the exposure time of the camera, followed by a sampling process at the pixel row sweep rate of the camera. Based on the proposed rolling-shutter camera model, the maximum symbol rate that such OCC systems can support is experimentally demonstrated, and the impact of imperfect time synchronization between the VLC transmitter and the rolling-shutter OCC receiver is characterized in the form of Inter-Symbol Interference (ISI). The equivalent three-tap channel model that results from this process is experimentally validated and the generated ISI is compensated with the use of linear equalization in reception. Simulation and experimental results show a strong correlation between them, demonstrating that the proposed approach can be used to make the OCC system work at the Nyquist sampling rate, which is equivalent to the pixel row sweep rate of the rolling-shutter camera used in reception.