Modified Wavelet Transform for Performance Enhancement of OFDM Communication Systems

This paper presents a modification of the conventional Orthogonal Frequency Division Multiplexing (OFDM) system, which utilizes the Discrete Fourier Transform (DFT), by replacing it with the Discrete Wavelet Transform (DWT). The motivation behind this study is to enhance spectral efficiency and robustness in wireless communication systems by leveraging the sparsity property of the wavelet domain, an aspect underutilized in traditional OFDM designs. In this system, the constellation diagram of modulated Binary Phase Shift Keying (BPSK) bits transformed by the Inverse DWT (IDWT) reveals that half of the resulting values are zero, while the remaining half are real values. This observation forms the basis for an efficient modulation technique, where the zero-valued components are repurposed as the imaginary part during IDWT modulation, allowing for the transmission of an additional 0.5 N bits without expanding bandwidth or increasing power. Performance comparisons demonstrate that the proposed DWT-based OFDM scheme achieves a 50% higher data rate than conventional BPSK-based OFDM and exhibits up to 1.1 dB SNR gain over Quadrature Phase Shift Keying (QPSK) at a Bit Error Rate (BER) of 10⁻³, while maintaining lower Peak-to-Average Power Ratio (PAPR). Comparative analysis shows that the proposed system’s BER performance lies between that of BPSK and QPSK. This configuration achieves a data rate improvement of 0.5 N , where N is the number of subcarriers. Moreover, the system offers a practical middle ground between BPSK’s robustness and QPSK’s higher data rate, making it a compelling solution for scenarios requiring a balanced trade-off between error performance and data rate. Simulation results further confirm that the proposed approach maintains performance stability even in scenarios with estimation errors, demonstrating the robustness of the system. Overall, the proposed model outperforms conventional OFDM designs in terms of data rate, PAPR, and BER-SNR trade-off, providing a novel, power-efficient, and adaptable alternative to conventional OFDM systems, suitable for deployment in realistic communication environments.