BER Improvement in OFDM Systems Using Wavelet Transform Based on Kalman Filter

Introduction

The FFT based systems are replaced by one of the wavelet transforms called the discrete wavelet transform (DWT). Since DWT based OFDM does not use cyclic prefix, so a better spectral control of channels can be achieved. Discrete wavelet transform employs a low pass filter (LPF) and a high pass filter (HPF) which operates as a quadrature mirror filters fulfilling perfect reconstruction and orthogonal properties. In order to transmit the modulated signal zero padding and vector transposing is done in DWT OFDM systems. The use of wavelet promises to reduce the inter symbol interference (ISI) and inter carrier interference (ICI). The wavelet transform offers a higher suppression of side lobes. First, gives the already existing self-cancellation scheme and adaptive modulation to decrease ICI in OFDM system have been explained. Kalman filter (KF) method, statistically estimate the frequency offset and correct the offset, using the estimated value at the receiver. It has been showed that using Kalman filter with DWT based OFDM systems; improvement in BER can be made Kalman filter has been discussed laterally. From discussion then observed that the proposed DWT-based OFDM system outperforms than other existing schemes.