A New LED Response Model and its Application to Pre-Equalization in VLC Systems
Rifat Kısacık, M. Yaser Yağan, Murat Uysal, Alí Emre Pusane, Arda D. Yalçınkaya
Abstract
With the growing interest in visible light communication (VLC), it is desired to transmit data at very high rates despite the LED's bandwidth becoming a bottleneck. The bandwidth of a white LED usually ranges between hundreds of kHz and a couple of MHz, limiting transmission rates dramatically in a VLC system. Successful design of an efficient equalizer for VLC systems heavily depends on the realistic modeling of LED's frequency response. In this letter, we first propose a new LED response model taking the parasitic effects appearing at higher frequencies into account. The proposed model provides better match with measurements of commercially available LEDs over a wide frequency range as compared to the existing models in the literature. Then, we design a digital equalizer in line with the proposed model and implement it as an offline digital system in Matlab. The designed equalizer yields an overall flat system response over a wide frequency range. As a demonstration, we present the measured eye diagrams and bit error rate performance results of the equalized VLC system with on-off keying modulation and demonstrate improvements in data rate in comparison to the LED bandwidth.