Summary on the GDR ISIS day dedicated to Enabling Technologies for sub-THz and THz communication, which took place in ANFR Maisons-Alfort Paris the 18^th of September 2019. Twelve presenters described their recent research results. Talks covered many aspects of sub-THz and THz communication, channel coding, physical layer antenna, channel propagation and test benches. About 30 attendees from industry, regulation agency, research institutes and academics exchanged their visions and discussed of the future of sub-THz and THz communication systems.

A short description of the talks are proposed here. Slides are available here: Part 1, Part2.

Introduction, Doré JB (CEA Leti)

The day was introduced by recalling the context, i.e. the frequency bands and the scenarios considered around the use of the sub-THz and THz bands. A brief presentation of the BRAVE project was made. The BRAVE project has two main objectives: 1) elaborate and evaluate innovative waveforms that are adapted to the particular properties of the sub-THz physical layer. 2) identify which new applications could benefit from beyond-5G speeds, i.e. several hundreds of gigabit per second (Gbps) or above.

The operators will strongly invest resources in order to acquire the new spectrum and deploy 5G infrastructure during next decade, with continuous evolutions to support the ever increasing network demands. The commercial, societal, industrial and economic benefits will take a few years more before they convert into a positive return on investment. Nevertheless, like previous mobile communication generations, it is expected that the immense demand for network resources will eventually outweigh the promises made by 5G today. The process of developing technological solutions for next generation (from the research laboratory to validation, standardization and integration) requires a significant amount of time, typically 10 years. The first stages of research often precede the application needs, and have always been required to be able to deliver future requirements. (see BRAVE white paper)

Spectrum Regulation, mmWave to subTHz, Faussurier E (ANFR)

The talk covered the regulatory aspects of the spectrum and provided an update on the status of discussions on the bands between 90 and 240 GHz. Frequencies above 275 GHz up 450 GHz have not yet been attributed by international regulation. The regulation context, bodies and responsibilities have been presented with a particular focus on national and European situations. The way the regulation rules adapt to the three following different kinds of service is explained: mobile, fixed or SRD (short range devices).

Antenna design challenges, Motta Cruz E (IETR-Université de Nantes)

This talk swept away the issues of antenna design for millimeter wave. Different approaches were discussed (direct or indirect excitation of the antennas) as well as their strengths and weaknesses in terms of efficiency, size, bandwidth, cost, implementation and alignment capability. The state of the art on the mmWave and sub-THz antennas performance and proofs of concept is exposed. In particular, two antennas developed at the EITR are presented: the parallel-fed continuous transverse stub (CTS) array at 77 GHz, and the transmit-array antenna at 28 GHz.

Indoor and urban propagation modelling and characterization in the sub-THz spectrum, Corre Y (Siradel)

Modelling of wave propagation in the sub-THz spectrum was addressed in this presentation. In particular, the methods known as ray tracing may have an interest in predicting the coverage of a radio system and providing insight in the propagation channel properties. The presentation described methods and simulation results in two typical use-cases: outdoor point-to-point backhaul; and in-office radio propagation. Propagation channel statistics (path-loss, delay spread) are derived from detailed environments and multiple predicted links.

THz detectors:  from Submillimeter Wave Instrument for Jupiter Icy Moon Explorer to wireless communication testbench, Krieg J-M (Observatoire de Paris)

A presentation of LERMA’s activities was made along two main lines: the description of an on-board instrument for a future Jupiter exploration mission operating in the 1200GHz spectrum and the implementation of two benches dedicated to wireless communications in the 180GHz and 300GHz bands, all embedding LERMA Shottky devices. Some experimental results or demonstrations are shared.

Signal processing dedicated to sub-THz communications: from RF impairments to Hilbert spaces, Bicais S (CEA Leti)

Signal processing issues related to the use of high frequency oscillators introducing phase noise have been presented. An innovative adaptive modulation, that is specifically optimized for phase-noise channels and is able to deliver ultra high data rates e.g. for backhaul, was proposed. It is evaluated on “outdoor” deployment scenarios. Finally, an algebraic framework for envelope modulations was discussed to allow the design of new modulations, which may apply to low-complexity receivers e.g. for kiosk scenarios.

EPIC: Enabling Practical wireless Tb/s communications with next generation channel coding, Douillard C (IMT Atlantique)

Wireless Tb/s communications are expected to become a main technology trend within the next ten years and beyond. Furthermore, for several decades, improvement in silicon technology has provided higher frequency, lower cost per gate, higher integration density and lower power consumption. However, microelectronics has now reached a point where it can no longer keep pace with the requirements of future communication systems, alone. Therefore, the Tb/s data rate is a significant challenge for the design of transceivers and in particular for forward error correction (FEC), the most complex component in the baseband chain. Consequently, silicon implementations of advanced channel coding schemes require a cross-layer approach involving coding theory, decoding algorithm development, parallel hardware architectures and semiconductor technology. This talk has introduced the H2020 EPIC project (GA 760150, 2017-2020) which aims at designing and implementing FEC codes for wireless Tb/s technology and beyond-5G systems. The project objectives and the adopted methodology have been presented as well as some latest results.

Generalized Spatial modulation for sub-THz communications, C.F Bader (CentraleSupelec/IETR)

Generalized spatial modulation (GSM) is a promising technique that can highly increase the spectral efficiency for ultra-high data rate systems. However, its performance degrades in highly correlated channels such as those in the millimeter wave (mmWave) and sub-THz bands. GSM conveys information by the index of the activated transmit antenna combination (TAC) and by the M-ary symbols. The scheme was described and performance were assessed for various channel. Moreover the impact of phase noise was evaluated. Despite some open issues, the spatial modulation could be a candidate for low complexity modulation dedicated to sub-THz communications.

Dual Trellis construction for high-rate punctured convolutional codes, Vinh Hoang Son Le (IMT Atlantique)

Puncturing a low-rate convolutional code to generate a high-rate code has some drawback in terms of hardware implementation. In fact, a Maximum A Posteriori (MAP) decoder based on the original trellis will then have a decoding throughput close to the decoding throughput of the mother non-punctured code. A solution to overcome this limitation is to perform MAP decoding on the dual trellis of a high-rate equivalent convolutional code. In the literature, dual trellis construction is only reported for specific punctured codes with rate k/(k + 1). In this talk, a multi-step method to construct the equivalent dual code defined by the corresponding dual trellis for any punctured code was described. First, the equivalent nonsystematic generator matrix of the high-rate punctured code was derived. Then, the reciprocal parity-check matrix for the construction of the dual trellis was deduced. As a result, it was demonstrated that the dual-MAP algorithm applied on the newly constructed dual trellis yields the same performance as the original MAP algorithm while allowing the decoder to achieve a higher throughput. When applied to turbo codes, this method enables highly efficient implementations of high-throughput high-rate turbo decoders.

Energy efficiency of massive MIMO infrastructure, I Fijalkow (ETIS)

Massive MIMO aims to build wireless base stations with hundreds of coherently operating antennas
serving tens of single antenna users in order to improve both the transmission capacity by a factor 10-50 and the energy-efficiency trade-off by up to a thousand times.
Precoding at the base station has been proposed by T. Marzetta to efficiently implement digital beamforming. It implies a high signal dynamic range and therefore a power backoff resulting
in less energy-efficiency. One-bit quantized Zero-Forcing precoding has been proposed to efficiently handle the RF front-end when the array is implemented with so many antennas. In this study, we analyze the energy-efficiency of the quantized Zero-Forcing precoded systems for a large
number of users and a massive MIMO base station. We take into account realistic power amplifier and computer consumption models in order to discuss the base station energy efficiency. We consider power consumption values related to mmWaves.

THz Radio communications: an overview and future challenges for 6G applications, I Siaud (Orange)

THz communications get underway promising solutions for dedicated use cases, handling throughput up to several hundred Gbit/s that bridge macro/micro/nano applications. The talk provides an overview on the current status of THz Communication systems focusing on ongoing research activities thorough Academia, European Horizon 2020 framework and standardization activities turned towards ETSI ISG mWT, ITU-R and IEEE802 standardization bodies. Another key challenge of the presentation is to identify in a second step, new opportunities for 6G applications that telecom operator would advocate and delve.

In a first part, THz band is presented regarding spectrum properties and regulations issues. Use cases are then addressed in connection with the physical properties of the THz band, recent work done around 7 collaborative projects (ANR BRAVE, H2020 TERRAPOD, ICT EU/JP THOR, ….) and standardization bodies. The second part deals with technical locks and breakthrough dealing with THz propagation, communication systems and antennas, leading to software-defined meta-surfaces for indoor deployment issues. Throughout this work statement, it has reached a level of relative maturity to develop first technological solutions enabling the set-up of hardware demonstrators and emerging system design and services.

Important information: The IETR-INSA and Orange-Labs Rennes organize an international workshop entitled “mm-Wave and THz communications for beyond 5G applications“ on 8-th November 2019 hosted by INSA in Rennes, France.

This full day workshop addresses mm-waves and THz communications  status  for Beyond 5G and 6 G applications.  Mm-wave  communications  resulting from national and  international  project achievements as  CominLabs  M5-HESTIA, FP7-ICT EU/JP MiWEBA, FP7-ICT MiWaves, 5G PPP mm-MAGIC  and other collaborative projects shall provide solid solutions  for mm-wave deployments. Advanced beam management  over moving hot-spots mixing  digital processing and RF components  dived in  mobile  cellular communications  still discloses research domains to explore  for optimization issues. THz communications, as an implicit evolution of mm-wave,  raise new opportunities and horizons making  communicate optical , physics of materials  and radio communities to  address the THz gap. The objective of the workshop is to  highlight research statements  in the mm-wave and THz domains and sketch emerging  technical challenges  for 6G applications. State of the art and results will be shown through technical presentations.  Exhibitions and posters will illustrate  Proof of Concepts and  dedicated realizations.

The workshop program and the procedure for registration are available on the workshop website.