Performance improvement for DCO-OFDM and ACO-OFDM systems using symbol time compression

Optical-orthogonal frequency division multiplexing (O-OFDM) systems, including the direct current biased optical OFDM (DCO-OFDM) and the asymmetrically clipped optical OFDM (ACO-OFDM), are very important to achieve high data rate transmission in visible light communication (VLC). However, the DCO-OFDM and ACO-OFDM systems suffer from adjacent channel interference (ACI) caused by out of band (OOB) and a high peak to average power ratio (PAPR). In this work, a pulse-shaping signal based on a symbol-time compression (STC) scheme is presented. The proposed shaped STC-DCOOFDM and shaped STC-ACOOFDM systems are capable of reducing both the ACI and the PAPR as well. Further, the OOB, PAPR, and computing complexity are analytically investigated. The simulation results verify the analytical study of the proposed methods for OOB reduction and power savings resulting in PAPR reduction. The proposed systems are evaluated for different modulation schemes, including BPSK, QPSK and 8QAM.