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 ≤ 5m × 5m). The signal-to-ISI ratio (SISIR) is evaluated over the horizontal plane of the mobile units (at a height of about 1m above the room floor). The present work may be considered as providing comparative performance assessment between the VLC system employing a point LED source and that of the VLC system employing a light source of rectangular area. It is assumed that the indoor light propagation is impaired by noise including
ambient light, shot noise and thermal noise. The overall noise is modeled 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 dependencies of the average propagation delay, rootmean-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.