My main research interests lie in the design of mathematical models and algorithms to estimate, equalize and synchronize communication signals, at the crossroad between signal processing and channel propagation. In particular, current works include physical-layer security, massive MIMO systems and the study of new modulation formats for wireless, optical fiber and fiber-wireless communications.

I actively collaborate with the University of Southern California (Los Angeles, U.S.A.), the National Institute of Information and Communications Technology (Tokyo, Japan) and the Centre Tecnològic Telecomunicacions Catalunya (Castelldefels, Spain).

In the following, my main research activities are listed, including references to related major publications. For an exhaustive list of publications, you can go to publications.

Physical-layer security for future communications

I have recently started to lead a research activity on building advanced physical propagation models and proposing practical signal processing algorithms to provide information-theoretic security at the physical layer of future wireless communications systems. More details and related publications will be coming soon.

Channel modeling 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 Research America. The goal of our project is to find and verify the applications of massive MIMO technologies based on channel measurements.

  • F. Rottenberg, R. Wang, J. Zhang, A. F. Molisch. Channel Extrapolation in FDD Massive MIMO: Theoretical Analysis and Numerical Validation, IEEE Globecom 2019. arXiv:1902.06844.
  • T. Choi, F. Rottenberg, J. Gomez-Ponze, A. Ramesh, P. Luo, J. Zhang, A. F. Molisch. Channel extrapolation for FDD massive MIMO: procedure and experimental results. IEEE 90th Vehicular Technology Conference (VTC Fall) 2019. arXiv:1907.11401
  • 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. 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 that the algorithms are general and can be applied to the OFDM modulation with large benefits as well.

  • F. Rottenberg, X. Mestre, F. Horlin, J. Louveaux, “Efficient Equalization of Time-Varying Channels in MIMO OFDM Systems,” IEEE Transactions on Signal Processing, 2019.
  • 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