Performance analysis of FFT based OFDM and DWT based OFDM for Underwater Acoustic Communication

The underwater acoustic communication demands high data rate with low power. One of the very important techniques for the requirement is Orthogonal Frequency Division Multiplexing (OFDM). The OFDM systems implemented is a conventional OFDM which has Fast Fourier Transform (FFT) blocks in their receivers and Inverse FFT (IFFT) blocks in their transmitters. Now the research shows the use of Discrete Wavelet Transform (DWT) in place of FFT and Inverse DWT (IDWT) in place of IFFT renders the increased system performance. The major reasons for the performance degradation in the conventional FFT OFDM compared to The DWT OFDM are Carrier Frequency Offset (CFO), Multipath effect and Doppler Effect which need to be tested. The paper discusses about the BER (Bit Error Rate) performance of the DWT OFDM in presence of Channel and without channel individually and the results are compared with that of the conventional OFDM. For this, The Channel estimation is carried over in both DWT OFDM and FFT OFDM using same procedure and their BER performance are simulated using MATLAB and Simulink. In both, for the given channel condition the DWT OFDM fairly outperforms the FFT OFDM.