Design of an OFDM System for VLC with a Viterbi Decoder

Abstract

In this research, we designed digital signal processing (DSP) modeling using Matlab for visible light communications (VLC) systems using orthogonal frequency division multiplexing (OFDM). The DSP modeling comprises three main parts: transmitter, receiver, and channel models. The receiver is designed to suppress the inter carrier interference (ICI) that may occur in a communications system using OFDM. To achieve it, we designed a synchronizer that comprises sampling frequency error estimation and a fine time synchronizer. Additionally, a Viterbi algorithm is used as the decoder to reduce the bit error rate (BER) of the system. In the transmitter, convolutional encoding is used to correct the frequency error of the OFDM signal. In the channel model, since light as a communications medium has several considerations that can affect signal quality, we model several conditions that can affect the quality of the transmission. To evaluate system reliability, we tested the system with various mappers: binary phase shift keying, quadrature phase-shift keying, quadrature amplitude modulation 16 (QAM16), and QAM64. From the simulation results, for signal-to-noise ratio (SNR) values that are not too small, a system with channel encoding and decoding has smaller BER values. Therefore, this study shows that convolutional encoding and the Viterbi algorithm in a VLC system using OFDM are able to reduce the system BER.