Design and Comparison of Discrete Wavelet Transform Based OFDM (DWT-OFDM) System

Orthogonal frequency division multiplexing (OFDM) that is typical for the current fourth generation mobile communication system, is a multi-carrier modulation (MCM) system that enables high-speed communication using multiple carriers. The existing OFDM scheme that maps symbols to subcarriers using an inverse fast Fourier transform (iFFT) operation uses a cyclic prefix (CP) to reduce inter-symbol interference in a multipath channel, which is a disadvantage of power and spectral efficiency respectively. Therefore, this paper aims to complement the existing shortcomings for next generation high-speed communication and to design more efficient MCM system. The proposed system uses IDWT (inverse discrete wavelet transform) operation instead of iFFT operation used in conventional OFDM. A wavelet transform is an operation that filters a signal using wavelet and scaling basis functions. Therefore, we compared the bit error rate (BER), spectral efficiency, and peak to average power ratio (PAPR) performance with the conventional OFDM system through the design of OFDM system based on wavelet transform. As a result, the conventional OFDM and wavelet-OFDM exhibited the same BER performance, and wavelet-OFDM using the Discrete Meyer wavelet had the same spectral efficiency as the conventional OFDM. In addition, all systems of wavelet-OFDM based on various wavelets confirm PAPR performance lower than conventional OFDM.