Intersymbol Interference in Indoor Visible Light Communication Systems Employing LED Sources of Large Area

Abstract

This work is concerned with the assessment of inter-symbol interference (ISI) encountered in indoor visible light communication (VLC) system inside a room of relatively small dimensions (room area). The signal-to-ISI ratio (SISIR) is evaluated over the horizontal plane of the mobile units (at a height of about above the room floor). The present paper provides performance assessment of the VLC system employing a light source of wide rectangular area in comparison to the VLC system employing a point LED source. It is assumed that the indoor light propagation is impaired by noise including ambient light, shot noise and thermal noise. The overall noise is modelled as additive white Gaussian noise (AWGN). The signal-to-interference-plus-noise ratio (SINR) including the effects of ISI and AWGN is evaluated over the horizontal plane of the mobile units. The corresponding bit-error-rate (BER) is also evaluated. The dependencies of the average propagation delay, root-mean-squared (RMS) delay spread, and SINR on the area of the LED source are numerically investigated. It is shown the SISIR for the indoor VLC system under consideration is significantly decreased with increasing the area of the LED source. Also, it is shown that the performance of the VLC is degraded with increasing the area of the LED source. The effect of increasing the radiated light power is shown to decrease the BER error rate and, hence, to improve the VLC performance especially at the room corners.