Low-complexity improved schemes for ACO-OFDM based on hartley transform or real-fourier transform over AWGN channel

SANYA, Max Fréjus Owolabi and CHOBLI, Hermine IGABOUY and SANYA, Stanislas Arthur Oladélé and ALONOUMI, Zola Cédric Bosco and AGLIKPO, Dounicia Laurence and MAGNIDET, Fifamè Merci-Ange (2025) Low-complexity improved schemes for ACO-OFDM based on hartley transform or real-fourier transform over AWGN channel. World Journal of Advanced Research and Reviews, 25 (2). pp. 1085-1098. ISSN 2581-9615

As a widely used Intensity Modulation and Direct Detection (IM/DD) system, Asymmetrically Clipped Optical Orthogonal Frequency Division Multiplexing (ACO-OFDM) is considered one of the most promising modulation techniques for high-speed optical communications. Conventional ACO-OFDM uses Hermitian Symmetry (HS) to guarantee a real signal, which results in high computational complexity. The Real Discrete Fourier Transform (RDFT) and Discrete Hartley Transform (DHT) offer alternative approaches to generating real-valued OFDM signals without the need for HS. In the existing literature, various modified techniques have been proposed to enhance ACO-OFDM in terms of bit error rate (BER) or spectral efficiency. However, these methods often suffer from high computational complexity or poor BER performance due to DC offsets and low-frequency noise. To the best of our knowledge, few studies have explored low-complexity yet improved ACO-OFDM schemes that use alternatives to the conventional Discrete Fourier Transform (DFT). In this context, this paper investigates the implementation of Diversity-Combining (DC) and Improved Noise Cancellation (INC) techniques using the Discrete Hartley Transform (DHT) and Real-DFT in an ACO-OFDM scheme over an Additive White Gaussian Noise (AWGN) channel. Simulations conducted in MATLAB 2021 show that both DHT-based and Real-DFT ACO-OFDM achieve similar BER performance compared to conventional ACO-OFDM. Furthermore, the proposed schemes demonstrate a 3 dB power gain in an AWGN channel over traditional ACO-OFDM. Given their low complexity and high performance, DHT-based and Real-DFT INC-ACO-OFDM emerge as promising candidates for optical network systems. Among them, DHT-based solutions are particularly advantageous due to their lower computational complexity.