Accuracy of the Point-Source Model of a Multi-LED Array in High-Speed Visible Light Communication Channel Characterization

During the indoor visible light communication (VLC) channel modeling procedure, the transmitter constituted by an array of light-emitting diodes (LED's) is frequently modeled as a single point source for convenience. However, how accurate this simplified treatment is remains unanswered. This paper compares the channel characteristics of both the simplified point-source model and six practical cases having various numbers of LEDs. Our numerical results show that the deviations in terms of the channel's optical path loss (OPL), as well as its bandwidth and the channel's delay spread, are steadily increased upon increasing the number of LEDs of each transmitter, until LEDs spread almost over the entire ceiling. Even in the worst case, the deviation of the OPL remains below 0.41 dBo, whereas that of the 3-dB transmission bandwidth is below 1.67 MHz. However, the deviation in terms of the root-mean-square (RMS) delay spread can reach 1.88 ns. Moreover, in terms of spatial distribution of the RMS delay spread, there is a nonnegligible difference between the simplified point-source model and different transmitter configurations.