Performance Evaluation of OFDM-Based Vehicular VLC Using Adaptive Bit-Loading

This paper demonstrates the superiority of direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) with adaptive bit-loading (BL) over DCO-OFDM without BL for the M-ary quadrature amplitude modulation (M-QAM) scheme in the visible light communications (VLC) system. Specifically, we implement VLC link using vehicle headlights and rear lights, and characterize of transmission performances in a vehicular scenario for a distance of 150 m between two vehicles. we intend to maximize the spectral efficiency (SE) through the proper selection of modulation order, M, while satisfying a targeted bit error rate (BER). For a light-emitting diode (LED) modulation bandwidth of 4.5 MHz and it is equal to the signal bandwidth, the study considers the BER of M-QAM for an M range of 4-128. Results show that a target BER of 7% forward error correction (FEC) limit, i.e. $3.8\times 10^{-3}$, can be achieved for the adaptive BL system while the bit rate and SE are $\sim$26.2Mb/s and $\sim$5.82b/s/Hz, respectively.