Performance Analysis of Indoor Visible Light Communication System with Multiple LED-Sources

The present paper is concerned with quantitative analysis of the effect of employing multiple LED sources on the performance of indoor visible light communication (VLC) systems. The analysis is based on the evaluation of the received signal distortion caused by the varying propagation delays of the same signal transmitted by multiple LED sources distributed on the room ceiling. Under the assumption of employing light intensity modulation or, equivalently, on-off-keying (OOK), the employment of multiple LED sources for simultaneous transmission of the same signal results in two types of distortion of the received signal. These are the slow rising and the delay spread of the received square pulse (bit), which results in intersymbol interference (ISI) that affects the performance of indoor VLC. The present work proposes a new mathematical method to obtain an exact analytic expression for the impulse response of the indoor VLC channel with multiple LED sources at the location of the receiver. This impulse response can be used to calculate the signal strength, the received signal distortion, the ISI, the resulting signal-to-ISI ratio (SISIR), and the corresponding bit-error-rate (BER) at the mobile unit location. The numerical results show that a maximum BER of 1 × 10
⁻⁵
over the room area can be achieved. Also, the present work arrives at important recommendations for the VLC system design regarding the number of LED sources, their distribution on the room ceiling, and their optimal Lambert index to get comfortable illumination and, in the same time, to enhance the VLC system performance. These recommendations are based on complete quantitative assessment of the room illumination and VLC system performance metrics.