Improved DWT-OFDM system performance with wavelet domain equalization for Co-CFO mitigation

Orthogonal Frequency Division Multiplexing (OFDM) systems using the Discrete Wavelet Transform (DWT) have shown improved spectral efficiency and time–frequency localization over traditional Discrete Fourier Transform (DFT)-based systems. However, a key problem arises in Multiple-Input Multiple-Output (MIMO) DWT-OFDM systems when operating over co-Carrier Frequency Offset (co-CFO) Rayleigh fading channels, where conventional Frequency Domain Equalizers (FDEs) exhibit degraded performance and high computational complexity. To address this issue, the aim of this paper is to develop an efficient and low-complexity equalization scheme tailored for the wavelet domain. We propose a Joint Low Complexity Regularized Zero Forcing–Wavelet Domain Equalizer (JLCRLZF-WDE) that replaces conventional FDEs and operates directly in the wavelet domain. The proposed method combines regularized zero forcing techniques with the wavelet transform to reduce complexity while maintaining robustness against channel impairments. The equalizer is tested under various MIMO scenarios (2 × 2, 3 × 3, and 4 × 4) using a simulated co-CFO Rayleigh fading channel environment. Simulation results show that the proposed JLCRLZF-WDE significantly reduces the average bit error probability and processing time compared to conventional approaches. Additionally, the scheme offers enhanced data rate, demonstrating its suitability for high-performance wireless communication systems. So, the JLCRLZF-WDE provides an effective and computationally efficient solution for equalization in MIMO DWT-OFDM systems, offering clear advantages in fading and frequency-offset scenarios.