Spectral Efficiency for Multi-bit and Blind Medium Estimation of DCO-OFDM Used Vehicular Visible Light Communication

Because of its relatively high and license-free bandwidth, great security, and low cost, visible light communication (VLC) is a strong competitor for vehicle VLC (V2LC). Its durability, high spectral efficiency, and ability to deal with inter-symbol interference make it an excellent choice for autonomous and connected vehicle applications that demand high data rate transmission (ISI). VLC systems can benefit from high-rate communication by reducing pilot overhead in standard pilot-based CE methods. However, this comes at the expense of greater complexity and decreased CE accuracy, which are both undesirable outcomes. Techniques for blind medium estimation (CE) for OFDM systems are discussed in the radio-frequency (RF) literature. There has been no work done in the VLC literature, however, on blind CE for OFDM systems. In order to improve CE accuracy for V2LC, we propose a new blind CE technique based on real-time data-based medium characteristics that is applicable to V2LC. The normalized medium frequency response (CFR) of V2LC broadcasts has been found to be unaffected by inter-vehicle distance, relative transmitter/receiver (Z) zenith angles, or even ambient light, according to real-world data collected from real cars to vehicles. As an alternative to estimating the normalization factor at each subcarrier individually, this medium characteristic is used to estimate the normalization factor for calculating the normalization factor in the blind CE. After running a large number of simulations at a variety of vehicle speeds, it was discovered that the suggested strategy beats pilot-based CE systems in terms of average throughput and bit error rate for all modulation schemes (BER). Moreover, for the realistic vehicle mobility scenario chosen from the Simulation of Urban Mobility, the real-time performance of the proposed blind CE is proven to be very close to the maximum throughput of each modulation scheme at high signal-to-noise ratio (SNR) levels (SUMO).