Transmission Concepts and System Realization for Terahertz Wireless Communications

• Applicants: Professor Wolfgang Gerstacker; Professor Dr.-Ing. Robert Schober; Professor Dr.-Ing. Martin Vossiek
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 389189659

• Final Report Year: 2023

Final Report Abstract

The project aimed at improving the understanding and modeling of limitations usually seen in THz communication and channel sounding, to examine these limitations with practical measurements and to develop novel communication methods based on the findings. The following results were obtained in the project. Static channel sounding data has been acquired with a VNA setup up to 500 GHz, and the captured data has been compared to simulated data. We have identified phase noise and dynamic range as typical hardware challenges for THz systems and developed a new holistic approach to realistically model phase noise. Furthermore, we have developed and tested a novel channel sounder based on two-way ranging radar measurements. The potential benefit of the “coherent full-duplex double-sided two-way ranging” technique has been verified for our novel channel sounder by simulations. A practical application of this technique seems not feasible currently due to unforeseen hardware limitations, which imply that white noise dominates the system performance even at low distances. Until the time of finalizing the report, we could not verify the novel approach with measurements yet due to the limitations of the available hardware. For a reliable THz transmission, we have designed fast beam alignment schemes for a multiple-antenna system for both line-of-sight and non-line-of-sight scenarios. Corresponding codebooks have been constructed for both cases, and a Multi-Armed Bandit (MAB) algorithm has been developed for a fast beam code selection with beamforming gains close to upper bounds at a significantly reduced latency compared to a full search and other MAB schemes. For acquisition of the channel impulse response of an indoor THz transmission, several compressive sensing based estimation schemes with high performance have been designed. Since the investigation of THz hardware impairments conducted in the project has identified phase noise as a dominant imperfection, we have developed a new transmission concept based on constant-weight codes which enable a low-complexity maximum-likelihood sequence detection in the presence of strong phase noise even without requiring channel knowledge. A theoretical error rate analysis and simulation results have shown the superiority of the proposed scheme for strong phase noise compared to benchmark schemes. Furthermore, we have designed modulation and coding schemes for a short-block THz transmission with high reliability and low latency. In general, our results indicate a need for additional research, especially regarding THz hardware components, to facilitate future research on THz communication.

Publications

• Compressive Sensing for Indoor THz Channel Estimation. 2018 52nd Asilomar Conference on Signals, Systems, and Computers. IEEE.
  Schram, Viktoria; Moldovan, Anamaria & Gerstacker, Wolfgang H.
  
• Analysis of THz Communications in the Finite Blocklength Regime. 2019 IEEE 20th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), 1-5. IEEE.
  Schram, Viktoria & Gerstacker, Wolfgang
  
• “Approximate Message Passing for Indoor THz Channel Estimation”, in Proc. of Third International Balkan Conference on Communications and Networking (BalkanCom), Skopje, North Macedonia, 2019, pp. 1-5.
  V. Schram, A. Bereyhi, J.-N. Zaech, R. R. Müller & W. Gerstacker
  
• Comparison of Transmission Concepts for Indoor THz Communication Systems. 2020 Third International Workshop on Mobile Terahertz Systems (IWMTS), 1-5. IEEE.
  Schram, Viktoria; Wu, Yifei; Kolleshi, Monika & Gerstacker, Wolfgang
  
• Hierarchical Beam Alignment in Single-User MIMO Single-Carrier Frequency Division Multiple Access Terahertz Communication Systems. 2021 IEEE International Conference on Communications Workshops (ICC Workshops), 1-7. IEEE.
  Wu, Yifei; Koch, Johannes; Vossiek, Martin & Gerstacker, Wolfgang
  
• Hierarchical beam alignment in SU-MIMO terahertz communications. ITU Journal on Future and Evolving Technologies, 2(7), 63-80.
  Yifei, Wu; Johannes, Koch; Martin, Vossiek & Wolfgang, Gerstacker
  
• A Novel Approach for Modeling and Digital Generation of RF Signals Distorted by Bandlimited Phase Noise. IEEE Journal of Microwaves, 2(4), 699-710.
  Tschapek, Peter; Korner, Georg; Fenske, Patrick; Carlowitz, Christian & Vossiek, Martin
  
• ML Detection without CSI for Constant-Weight Codes in THz Communications with Strong Phase Noise. GLOBECOM 2022 - 2022 IEEE Global Communications Conference, 831-836. IEEE.
  Wu, Yifei; Koch, Johannes David; Vossiek, Martin; Schober, Robert & Gerstacker, Wolfgang