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# Full frequency duplex link over 645m in the 300 GHz band

A Renau, C Maye, D Wrana, S Haussmann, I Kallfass, L John, B K Jung, U Hellrung, P Schlegel, T Kuerner, et al.

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A Renau, C Maye, D Wrana, S Haussmann, I Kallfass, et al. Full frequency duplex link over 645m in the 300 GHz band. Journée du Club Optique Micro-ondes (JCOM 2023), Jun 2023, Visio conference, France. hal-04160795

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Submitted on 12 Jul 2023

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# Full frequency duplex link over 645m in the 300 GHz band

A. Renau*<fnref n="1" />, C. Maye<fnref n="1" />, D. Wrana<fnref n="2" />, S. Haussmann<fnref n="2" />, I. Kallfass<fnref n="2" />, L. John<fnref n="3" />, B.K. Jung<fnref n="4" />, U. Hellrung<fnref n="4" />, P. Schlegel<fnref n="4" />, T. Kuerner<fnref n="4" />, R.P. Braun<fnref n="5" />, Y. Leiba<fnref n="6" />, T. Kawanishi<fnref n="7" />, S. Hisatake<fnref n="8" />, K. Kondou⁹, P. Szriftgiser<fnref n="10" />, G. Ducournau*<fnref n="1" />

**Abstract**—We present here a demonstration of THz transmission system enabling a full frequency duplex link in the 300 GHz band. This system is coupling a super-heterodyne architecture, E-band modems and duplexing system at 300 GHz.

**Keywords** — THz, wireless millimetre/sub-mm technologies.

## I. INTRODUCTION

Terahertz (THz) transmissions systems are getting more and more attention for the 6th generation of cellular wireless communications that requires backhaul links with very high data-rate. Beyond the D-band (140-170 GHz) that is envisioned to start to be used within next 5 years, the 300 GHz will be the next step towards 100 Gbit/s backhauls. Many system approaches are considered ahead of these future backhauls, but almost all demonstrations rely on unidirectional links. We propose here the validation of a full duplex system and demonstrate a full-duplex link on a single antenna pair over 645 m.

## II. LINK ARCHITECTURE AND PERFORMANCE

The link architecture is based on a super heterodyne approach which is able to up-convert traditional backhauling frequencies (< 100 GHz) up to the THz range and thus enabling channel aggregation. It was first demonstrated in [1], then it was shown that this approach enabled to meet the new IEEE 802.15.3d THz communication standard [2]. Targeting real implementation of THz backhauls in super heterodyne architecture, it is relevant to make the system compatible to a single antenna pair to simplify the alignment constraints for the expected outdoor use cases. This can be achieved with a duplexing system as shown in the figure 1. In this figure, a set of two up/converters are used to reach the 300 GHz band, where $f_{THz} = 3.f_{LO} + f_{IF}$, with $f_{LO} = 73.333$ GHz, and $f_{IF} = 74.6$ GHz or 84.6 GHz.

<figure><img src="image_3.png" /><figcaption>Figure 1: System architecture: two E-band modems with 10 GHz frequency spacing (74.6 and 84.6 GHz) are up/down converted into the 300 GHz band (295 and 305 GHz). The local oscillators are in this case achieved using a photomixing approach to avoid spurious tones in the LO signal at 73.333 GHz.</figcaption></figure>

<footnote n="1">¹Univ. Lille, CNRS, Centrale Lille, UPHF, JUNIA, UMR 8520 - IEMN, F-59652 Villeneuve d'Ascq, France</footnote>

<footnote n="2">²Institute of Robust Power Semiconductor Systems (ILH), University of Stuttgart, Stuttgart, Germany</footnote>

<footnote n="3">³Fraunhofer IAF, Fraunhofer Institute for Applied Solid State Physics, Freiburg, Germany</footnote>

<footnote n="4">⁴Technische Universität Braunschweig, Institut für Nachrichtentechnik, 38106 Braunschweig, Germany</footnote>

<footnote n="5">⁵DEUTSCHE TELEKOM AG, Winterfeldtstr. 21, 10781 Berlin, Germany,</footnote>

<footnote n="6">⁶Siklu Communications Ltd., Petach Tikva, Israel</footnote>

<footnote n="7">⁷Faculty of Science and Engineering, Waseda University,</footnote>

<footnote n="8">⁸Faculty of Engineering, Gifu University, 9HRCP Research and Development Partnership,</footnote>

<footnote n="10">¹⁰PhLAM Laboratoire de Physique des Lasers, Atomes et Molécules, 59650 Villeneuve d'Ascq, France</footnote>

<footnote>*alexandre.renau@univ-lille.fr, guillaume.ducournau@univ-lille.fr</footnote>
### III. BACK TO BACK PERFORMANCE

In order to estimate the link margin and the system is first testbed in back to back (B2B) case (ie with an attenuator between the T/R up/down converters, located at both ends. The modems in E-band are integrated with a monitoring system that enable to check the carrier to interference plus noise ratio (CINR), with a limit of 19 dB to be able to handle a QAM-32 signal. The channel bandwidth was here fixed by the E-band modem to 2.16 GHz, and the maximum net data-rate was 6.26 Gbit/s in each direction (total 12.52 Gbit/s). The data-rate was measured with the IPERF tool [3] dedicated for the testing of IP networks.

<figure><img src="image_4.png" /><figcaption>Figure 2 : Back to back test of the THz duplexed FSS system. For a QAM-32 operation, the system margin was evaluated to 21 dB.</figcaption></figure>

The THz link was then successfully tested in an outdoor configuration with a pair of two Cassegrain antennas (62 dBi) over a 645 m distance, with a QAM-32 performance (12.52 Gbit/s).

<figure><img src="image_5.png" /><figcaption>Figure 3: Outdoor validation of the duplexed link over a 645 m distance.</figcaption></figure>

### Références :

[1] I. Dan, G. Ducournau, S. Hisatake, P. Szriftgiser, R. -P. Braun and I. Kallfass, "A Terahertz Wireless Communication Link Using a Superheterodyne Approach," in IEEE Transactions on Terahertz Science and Technology, vol. 10, no. 1, pp. 32-43, Jan. 2020, doi: 10.1109/TTHZ.2019.2953647.

[2] D. Wrana, Y. Leiba, L. John, B. Schoch, A. Tessmann and I. Kallfass, "Short-Range Full-Duplex Real-Time Wireless Terahertz Link for IEEE802.15.3d Applications," 2022 IEEE Radio and Wireless Symposium (RWS), Las Vegas, NV, USA, 2022, pp. 94-97, doi: 10.1109/RWS53089.2022.9719954.

[3] IPERF Software [Online]. Available https://iperf.fr/iperf-download.php