Performance Evaluation of DWT-OFDM and FFT-OFDM for Multicarrier Communications Systems using Time Domain Zero Forcing Equalization

Abstract

Other than the conventional fast Fourier transform (FFT) for multicarrier modulation, a new approach for multicarrier modulation (MCM) has been known. Meanwhile, multicarrier modulation involves dividing the broadband channel into many orthogonal but overlapping narrowband carriers. In an OFDM modulation based multicarrier system using the FFT, a cyclic prefix (CP) is inserted after each symbol frame to combat the effects of inter symbol interference (ISI). By inserting the CP, which results in spectral inefficiency OFDM schemes trades up to 25% of the transmit bandwidth. A new MCM approach that is void of the expense is the wavelet transform-based systems. These systems also have very suppressed side-lobes and exhibit improved BER performance. In wavelet based systems, the latest challenge in its implementation is in the channel estimation. In this work we have studied the performance of the FFT based OFDM system against wavelet transform (WT) based multicarrier system using a simple zero forcing (ZF) equalization in time domain. The studied system shows some improved BER performance.

Multicarrier QAM Modulation Based on Discrete Wavelet Transform Using Wireless MIMO System

“…DWT has large power spectral density as compared to OFDM due to the fact that DWT produce well contained side lobes with the narrower side lobe having the contained energy with reduced out-of-band energy [6]. The power of the wavelet transform comes from the fact that the basic functions of the wavelet are localized in time (or space) and frequency, and have different resolutions in these two domains.…”

“…Moreover, the pulse shaping function used to modulate each subcarrier extends to infinity in the frequency domain this leads to high interference and lower performance levels [5]. This scheme also required a cyclic prefix (CP) insertion which is added to each OFDM symbol in order to compensate for the ISI which wastes up to 25% of the scarce bandwidth [6].…”

“…Thus, there have been approaches of wavelet based OFDM which does not require the use of the CP extension [7 -10]. Since there is no CP, the equivalent copied noise during cyclic prefixing is saved so that the BER performance of the Wavelet based systems is improved [6].…”

Performance Analysis of Discrete Wavelet Transform Based Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing System for Different Wavelets in Different Channel Environment

“…In this conventional MIMO OFDM scheme the basic building block used for OFDM modulation is IFFT and for demodulation is FFT. In recent times it has been established that by replacing the IFFT/FFT blocks with IDWT/DWT blocks considerable amount of increase in the performance can be achieved (Abdullah and Hussain, 2009;Asif et al, 2012). Also for DWT based OFDM there is no need for cyclic prefix as in the case of conventional FFT based system.…”

A Unique Wavelet-based Multicarrier System with and without MIMO over Multipath Channels with AWGN

“…More recently, the present authors in R. Asif et al [25] have proposed DWT for multi-carrier modulations using time domain equalization. In this study we present a new way of channel equalization when working with wavelets.…”