My main research interests lie in the design of mathematical models and algorithms to estimate, equalize and synchronize communication signals, with emphasis on low complexity and practical solutions. This includes the study of various waveforms (OFDM, FBMC-OQAM) and propagation mediums (wireless, optical fiber, fiber-wireless, VLC).

Channel modelling and estimation for massive MIMO systems

The deployment of massive multiple-input-multiple-output (MIMO) communications systems strongly rely on the acquisition of accurate channel state information (CSI) at base station (BS). Acquiring this CSI is a challenging task, especially in certains scenarios such as FDD or highly time and frequency varying propagation environments. At USC, I am the project leader for the project on massive MIMO systems, supported by Samsung. The goal of our project is to find and verify the applications of massive MIMO technologies based on channel measurements.

  • F. Rottenberg, T. Choi, P. Luo, J. Zhang,  A.F. Molisch. Performance Analysis of Channel Extrapolation in FDD Massive MIMO Systems. arXiv:1904.00798.
  • F. Rottenberg, R. Wang, J. Zhang, A. F. Molisch. Channel Extrapolation in FDD Massive MIMO: Theoretical Analysis and Numerical Validation, submitted to IEEE Globecom 2019. arXiv:1902.06844.
  • T. Choi, F. Rottenberg, J. Gomez, Jianzhong Zhang, A. F. Molisch. How Many Antennas Do We Need For Massive MIMO Channel Sounding? – Validating Through Measurement. Submitted to APS-URSI, 2019. arXiv:1903.08207.

Channel equalization for MIMO wireless systems

As propagation channels exhibit significant variations in time and frequency, the orthogonality of multicarrier systems is often progressively destroyed. Together with Dr. X. Mestre (CTTC, Spain), I have addressed the performance analysis and the design of compensation algorithms for various wireless multiple-antenna scenarios characterized by channels that are highly varying in time and frequency. The algorithms were initially devised for FBMC-OQAM systems. However, we recently showed (paper currently submitted) that the algorithms are general and can be applied to other modulations as well.

  • F. Rottenberg, X. Mestre, F. Horlin and J. Louveaux, “Performance Analysis of Linear Receivers for Uplink Massive MIMO FBMC-OQAM Systems,” IEEE Transactions on Signal Processing, 2018.
  • F. Rottenberg, X. Mestre, D. Petrov, F. Horlin and J. Louveaux, “Parallel Equalization Structure for MIMO FBMC-OQAM Systems under Strong Time and Frequency Selectivity,” IEEE Transactions on Signal Processing, 2017.
  • F. Rottenberg, X. Mestre, F. Horlin and J. Louveaux, “Single-Tap Precoders and Decoders for Multi-User MIMO FBMC-OQAM under Strong Channel Frequency Selectivity,” IEEE Transactions on Signal Processing, 2017.

Linear impairments compensation in optical fiber systems

The study of the applicability of the FBMC-OQAM modulation to optical fiber communication systems has been another major part of my PhD thesis. More specifically, in collaboration with Dr. T.-H. Nguyen (ULB, Belgium) I studied the design of compensation methods for linear impairments arising in optical fiber communications.

  • F. Rottenberg, T.-H. Nguyen, S.-P. Gorza, F. Horlin and J. Louveaux, “Advanced Chromatic Dispersion Compensation in Optical Fiber FBMC-OQAM Systems,” IEEE Photonics Journal, 2017.
  • T.H. Nguyen, F. Rottenberg, S. P. Gorza, F. Horlin and J. Louveaux, “Efficient Chromatic Dispersion Compensation and Carrier Phase Tracking for Optical Fiber FBMC/OQAM Systems,” IEEE/OSA Journal of Lightwave Technology, 2017.

New transmission for MIMO fiber-wireless systems

Fiber-wireless (FiWi) technology is currently seen as a very attractive backhaul/fronthaul solution for 5G deployment as it allows simple connection of central stations to a large amount of remote cell sites. The FiWi technology relies on the combination of an optical fiber between the central station and a remote antenna unit and a millimeter-wave wireless link between the remote antenna unit and the remote cell site. In collaboration with Dr. P. T. Dat (NICT, Japan), we recently demonstrated the use of new waveforms in FiWi systems and showed the advantages of using such technology for high speed trains.

  • P. T. Dat, A. Kanno, K. Inagaki, F. Rottenberg, N. Yamamoto and T. Kawanishi, “High-Speed and Uninterrupted Communication for High-Speed Trains by Ultrafast WDM Fiber-Wireless Backhaul System,” IEEE/OSA Journal of Lightwave Technology, 2019
  • F. Rottenberg, P. T. Dat, T.-H. Nguyen, A. Kanno, F. Horlin, J. Louveaux, N. Yamamoto. “2x2 MIMO FBMC-OQAM Signal Transmission over a Seamless Fiber–Wireless System in W-band,” IEEE Photonics journal, 2018