Advanced DFE and MLD Techniques for Enhanced 5G mm-Wave A-RoF Performance at 60 GHz

This article presents the Decision Feedback Equalizer (DFE) and the Maximum Likelihood detection (MLD) algorithms designed in MATLAB to equalize the received signal in a dispersive optical link up to 120 Km. The algorithms are tested using a converged 5G mm-wave analog radio-over-fiber (A-RoF) system at 60 GHz. The algorithm’s performance is measured regarding error vector magnitude (EVM) values before and after equalization, for different optical fiber lengths and modulation formats (QPSK, 16-QAM, 64-QAM, and 128-QAM) and shows a clear performance improvement of the output signal. Moreover, the performance of the proposed algorithms is compared to three commonly used algorithms: the simple least mean square (LMS) algorithm, the constant modulus algorithm (CMA), and the adaptive median filtering (AMF) demonstrating superior results in both QPSK and 16-QAM and extending the transmission distance up to 120 km. DFE has a significant advantage over LMS and AMF in reducing the inter-symbol interference (ISI) in a dispersive channel by using previous decision feedback, resulting in quicker convergence and more precise equalization. MLD on the other hand is highly effective in improving detection accuracy by taking into account the probability of various symbol sequences achieving lower error rates and enhancing performance in advanced modulation schemes. Furthermore, DFE and MLD are particularly suitable for higher-order modulation formats like 64-QAM and 128-QAM, where accurate equalization and error detection are of utmost importance. The enhanced functionalities of DFE and MLD in managing greater modulation orders and expanding transmission range highlight their efficacy in improving the performance and dependability of our system.