Design and Performance Investigation of Discrete Wavelet Transform (DWT) Based OFDM Using 4-PAM for Indoor VLC System

Combining Discrete Wavelet Transform (DWT) with Pulse Amplitude Modulation (PAM) based OFDM in Visible Light Communication (VLC) will reduce the complexity of signal processing and answer the challenge of VLC. This paper has successfully simulated single level and four level DWT based OFDM using 4-PAM for indoor VLC system with various wavelet. The result is investigated by comparing BER and PAPR of DWT-OFDM with FFT-OFDM using QPSK and 4-QAM and DCT-OFDM using 4-PAM. From the investigation, haar and db1 are the wavelet type with smallest BER. BER of DWT based OFDM is smaller than BER of FFT-OFDM and DCT-OFDM in various channel condition that is modelled in this research. For θ=0° and 10° BER of DWT-OFDM reach 10^-3 at SNR 17dB and 18dB respectively, whereas FFT-OFDM reach 10^-3 at SNR 23dB. On the other hand, BER of DCT-OFDM only reach minimum value at 10^-2 with SNR 40dB. Four level DWT-OFDM reduce BER and PAPR. Its BER reach 10^-3 at SNR 10dB. The low PAPR is achieved by four level DWT-OFDM using db1 (7.7753dB) and haar (7.7995dB) compared to FFT-OFDM with 4QAM (13.3420dB), QPSK (13.4430dB) and DCT-OFDM (13.2816dB). The detail investigation is explained in depth in this research.