Performance Analysis of Improved Noise Cancellation Discrete Hartley Transform ACO-OFDM in a AWGN channel

Asymmetrically Clipped Optical Orthogonal Frequency Division Multiplexing (ACO-OFDM) stands as one of the most promising modulation techniques in high-speed optical communications. However, enhancing the error rate or spectral efficiency of conventional ACO-OFDM in optical systems remains a challenge. Existing enhanced ACO-OFDM demodulation techniques often suffer from either high computational complexity or poor performance due to limitations like DC-offsets and low frequency noise. To address this challenge, we propose a novel ACO-OFDM demodulation scheme based on Hartley transform and Pulse Amplitude Modulation (PAM), named "Improved Noise Cancellation ACO-OFDM (INC ACO-OFDM)". This scheme combines the advantages of both Diversity-Combined ACO-OFDM (DC ACO-OFDM) and Noise Cancellation ACO-OFDM (NC ACO-OFDM) without employing Hermitian symmetry. The proposed INC ACO-OFDM technique uses a Virtual Clean Windows (VCW) identification process, allowing the use of even subcarriers of ACO-OFDM to enhance the demodulation performance, even in the presence of DC offset. Simulation results conducted using MATLAB R2021a over an Additive White Gaussian Noise (AWGN) channel demonstrate that the proposed INC ACO-OFDM technique achieves similar Bit Error Rate (BER) performance as DC ACO-OFDM with a significant reduction in computational complexity, providing a 3 dB power gain compared to ACO-OFDM with similar spectral efficiency.