The main BRAVE results for the modeling, characterization and optimization of the PHY layer of future 6G subTHz communications were presented on September 28^th 2021, at CentraleSupélec (Rennes) in front of an audience of about 40 people (partly on site, partly remote).

Launched in January 2018, the ANR-BRAVE project will be completed soon, after a 45-month innovation effort to characterize, consolidate and promote the opportunities offered by the subTHz spectrum (90 – 300 GHz) towards very-high-speed 6G communications. The project partners (ANFR, CEA-Leti, Centrale Supélec and SIRADEL) are among the pioneers in the exploration of the subTHz physical layer (PHY), and today offer solutions to adapt the modulations, transceiver design and test/simulation tools according to specific subTHz constraints. Those solutions allow for a more efficient usage of a new spectrum with potentially several tens of GHz available.

The agenda included the following presentations:

• Summary on BRAVE outcomes, by Yoann Corre (SIRADEL), project’s coordinator.

Summary of the research effort on subTHz regulation; modeling of the propagation channel and RF performance; identification of modulations adapted to the subTHZ PHY layer properties; performance evaluation of future subTHz networks. These results have been widely disseminated via publications, scientific national or international events, and open data.

• SubTHz P-QAM modulations, by Jean-Baptiste Doré (CEA-Leti).

Phase noise is one of the major RF impairments of mmWave/subTHz RF transceivers. In this talk, we will describe a framework and results for the optimization of QAM constellation inherently robust to Gaussian phase noise when associated to a single carrier waveform. 

• MIMO energy detector, by Jean-Baptiste Doré (CEA-Leti).

The significant amount of unused spectrum in subTHz frequencies is contemplated to realize high rate wireless communications. Yet, the performance of radio-frequency subTHz systems is severely degraded by strong oscillator phase noise. Therefore, we studied the use of multiple-input multiple-output (MIMO) systems with energy detection receivers to achieve high rate communications robust to phase noise. We considered a realistic scenario modeling an indoor wireless link in sub-THz with directive antennas and strongly correlated line-of-sight channels. Our results demonstrate that spatial multiplexing with non-coherent subTHz transceivers can be realized on strongly correlated line-of-sight channels using the proposed detection schemes.

• New Index modulations, by Carlos Bader, Majed Saad and Mohammad Alawieh (CentraleSupélec).

Summary of our research work in the waveform, modulation and transceiver design for low-power Wireless Terabits systems: proposed approach for subTHz systems to mitigate the technological limitations and RF impairments; proposed novel index modulation techniques for high spectral and energy efficiency; system optimization for better performance and lower transceiver complexity; comparative study of different potential MIMO candidates and performance assessment in subTHz environment.

• SubTHz network simulation, by Yoann Corre and Laurent Maviel (SIRADEL).

The simulation of backhaul and access networks in the subTHz band require suitable tools; this includes precise modeling of the environment, realistic prediction of the propagation channel, and relevant modeling of system performance. The simulation of backhaul links or coverage maps for different implemented scenarios allows to refine the characterization of the BRAVE technologies, and to demonstrate their application. In particular, LiDAR data was used together with ray-tracing and an automated optimization method to dimension a Fixed Wireless Access network in the 150 GHz band.