Improved Next-Generation Radio Access Networks Using a Centralized Opto-Electronic Oscillator


  • Mehmet Alp Ilgaz Trzaska cesta 25, Faculty of Electrical Engineering, University of Ljubljana, Slovenia
  • Kristjan Vuk Baliž Trzaska cesta 25, Faculty of Electrical Engineering, University of Ljubljana, Slovenia
  • Boštjan Batagelj Trzaska cesta 25, Faculty of Electrical Engineering, University of Ljubljana, Slovenia



optoelectronic oscillator, chromatic dispersion, front haul, phase noise, 5G radio access network, radio-over-fibre, wideband opto-electronic oscillator, integrated microwave photonics


Next-generation 5G and 6G radio access networks (RANs) require millimetre-wave (mm-W) oscillators to generate extremely low phase-noise signals for the frequency up-conversion and down-conversion in radio units (RUs). The opto-electronic oscillator (OEO) is an outstanding candidate for generating a high-purity mm-W signal in a centralized radio access network (C-RAN) where the distributed base-stations are dislocated from the digital units (DUs) and there are only RUs on the remote side. In this paper we propose placing an OEO in the central-office, while distributing its signal from there to multiple RU base-stations through the mobile front-haul network using a radio-over-fibre (RoF) transmission approach. This new approach was used in experiments that proved the smaller degradation of the phase noise compared to a degradation of 6 dB for the well-known frequency-doubling electrical oscillator in the RU. In addition, we present the signal-strength degradation due to fibre dispersion in mm-W signal distribution, as well as the challenges in long-term stability and multimode operation. We propose solutions to overcome these drawbacks and make our new approach useful for a centralized carrier signal distribution in next-generation RANs.


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Author Biographies

Mehmet Alp Ilgaz, Trzaska cesta 25, Faculty of Electrical Engineering, University of Ljubljana, Slovenia

Mehmet Alp Ilgaz received a bachelor degree in Electrical and Electronics Engineering from Yeditepe University in 2012 and a master’s degree in Electronics Engineering at the University of Bologna in 2015. He received his PhD from the University of Ljubljana in 2020 for Opto-electronic Oscillators in Radio Access Networks. His research interests include radio-frequency communications, opto-electronics, and integrated optics.

Kristjan Vuk Baliž, Trzaska cesta 25, Faculty of Electrical Engineering, University of Ljubljana, Slovenia

Kristjan Vuk Baliž received his master’s degree from the Faculty of Electrical Engineering, University of Ljubljana, Slovenia, in 2019. He is currently employed as an assistant teacher at the Faculty of Electrical Engineering in Ljubljana. His research interests include microwave photonics, electromagnetic radiation and wave propagation in telecommunications and numerical analysis of electromagnetic phenomena inside waveguide structures.

Boštjan Batagelj, Trzaska cesta 25, Faculty of Electrical Engineering, University of Ljubljana, Slovenia

Boštjan Batagelj received his PhD from the University of Ljubljana in 2003 for work on optical-fiber non-linearity measurements by four-wave mixing. Currently, he is an associate professor at the University of Ljubljana, Faculty of Electrical Engineering and a member of the international organizations IEEE and OSA. As a researcher he works in the Radiation and Optics Laboratory in the Information and Communications Technology Department. His current research interests include work on the physical layer of optical transport and optical access networks, including the convergence with radio systems and components. He is named as an inventor on ten patents.


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