DWMT transceiver equalization using overlap FDE for downlink ADSL

Abstract

Discrete wavelet multitone (DWMT) modulation is a wavelet transform based technique implemented using perfect reconstruction filter banks. It has been recently proposed for various wireline channels such as digital subscriber loops (DSLs) as a solution to the problems posed by a discrete multitone (DMT) transceiver including interblock interference (IBI) and lower spectral efficiency due to the employment of a cyclic prefix (CP) in the guard interval (GI) for DMT symbols. The greater side lobe attenuation offered by wavelet filter banks results in improved spectral containment and lower IBI in DWMT transceivers. However, no standard equalization technique exists for a DWMT based transceiver so as to remove the effect of channel on the transmitted signal in DWMT systems. This paper proposes the application of overlap frequency domain equalization (OFDE) in DWMT modulated systems and compares the bit error rate (BER) performance with time domain equalization (TDE) technique. It is shown through simulation results that minimum mean square error (MMSE) based OFDE can be applied as an equalization technique for a downlink asymmetric DSL (ADSL) channel with lower computational complexity and BER performance comparable to that of TDE.

Performance Analysis of DWMT Transceiver for ADSL Channel with Overlap FDE in Presence of AWGN, Crosstalk and Impulse Noise

“…For the first time, Overlap FDE was applied by Tomeba for MCM systems [13] and later used by Sohaib for wavelet OFDM [13]. In [7], authors showed its supremacy for ADSL systems for DWMT transceiver in presence of AWGN and FEXT, NEXT. In this paper, we are evaluating Overlap FDE performance for ADSL systems for DWMT transceiver in presence of AWGN, FEXT, NEXT and impulse noise.…”

“…Here is dimension of the signal. For Overlap FDE, the complexity of points is given by, [ ( ( )) ] represents the size of IFFT/FFT [7]. Complexity comparison for TDE and Overlap FDE for DWMT transceiver is shown in Table III. VII.…”

“…In case of large delay spread, TDE equalizer structure becomes complex, thus FDE is preferred because of its less complexity as compared to TDE [7].…”

“…Equalization is performed according to the taps optimized by either zero forcing (ZF) and minimum mean square error (MMSE). FDE weights ( ) are calculated by method given in [7].…”

“…FFT based systems have high energy containment in side lobes as compared to DWT based systems, which makes DWT systems more robust against narrowband interference and multipath fading affects [6]. WT based MCM technique has been standardized for power line communication (PLC) in IEEE P1901 [7].…”