Alleviating LED Nonlinearity in a HACO System Using a Blend of Precoder and a \(\upmu\)-Law Compander

Due to its many advantages, orthogonal frequency division multiplexing (OFDM) is frequently utilised in optical wireless systems to achieve rapid data transmission. Hybrid asymmetrically clipped optical OFDM (HACO-OFDM) is a widely utilised approach in OFDM-based visible light communication (VLC) systems because it allows for high-rate burst transmission while maintaining reliability in a multi-path fading environment. Meanwhile, the congenital nonlinear characteristic of LEDs is a critical hindrance in VLC OFDM systems due to the high peak-to-average power ratio (PAPR) of OFDM signals. The high PAPR necessitates a large input back-off power to operate LEDs in the linear zone, lowering the BER of OFDM-based optical devices. In order to reduce PAPR and ameliorate non-linearity in the HACO-OFDM system, this work offers a hybrid precoder with \(\upmu\)-law compander approach. The auto-correlation association of modulated data symbols is suppressed by pre-processing in the frequency domain using a preset precoder matrix (PM), resulting in a low PAPR score. PAPR is further reduced by compressing the precoded signal in the time domain with the \(\upmu\)-law compressor. The PAPR of the proposed design is just 5.1 dB. It also reduces the non-uniform SNR spread among data symbols and mandates a low SNR for a 10\(^{-5}\) reference bit error rate (BER). Furthermore, with a reference BER of 10\(^{-3}\), the hybrid approach reduces the optical bit energy required for high-speed data transmission. The metric used to calculate the system’s non-linearity is the percentage error vector magnitude (EVM %). For 0 dB input back-off (IBO), the hybrid technique has an EVM of 5.59%, compared to 30% for a traditional HACO system. The reduction in LED nonlinearity reduces in-band and out-of-band distortion, allowing high-data-rate services to be supported.