Performance Comparison of Wavelet Packet Transform (WPT) and FFT- OFDM System Based on QAM Modulation Parameters in Fading Channels

Orthogonal Frequency Division Multiplexing (OFDM) has been widely adopted in many applications due to its good spectral performance and low sensitivity to impulse noise and multipath channels. It has been widely adopted and standardized in many applications today. It is well known in OFDM that a cyclic prefix (CP) is appended to each symbol in order to mitigate the effect of Inter-Symbol-Interference (ISI). However, this reduces the spectral efficiency. A perfect reconstruction using wavelet packet transmultiplexer in OFDM transceiver counters the degrading effect of ISI, and also conserves bandwidth. In comparison to FFTOFDM, Wavelet Packet Modulation (WPM) offers much lower side lobes in the transmitted signal, which reduces inter carrier interference (ICI) and narrowband interference (NBI). WPM improves spectral efficiency due to the exclusion of CP. Nevertheless, it requires an efficient equalization technique to counter the ISI and ICI. Wavelet based OFDM has been suggested to improve BER performance of transceiver in wireless communication. In this paper, a study of wavelet packet transform modulation WPT-OFDM scheme is conducted, and the performance comparison is made against the traditional FFT-OFDM over various fading channels. The analysis is done using various number of modulation QAM constellation points. Specifically, the analysis is on the effect of QAM constellation points in AWGN channel, flat fading channel and frequency selective fading channels. Simulation results using QAM Modulation points (8 to 64 Point), and the BER best performance of WPTOFDM system is when the QAM Modulation parameter (QAM = 8) in all channels.