European recommendations on sub-THz frequency usage

Only limited regulation is available today in Europe for the use of frequencies above 90 GHz. Information is provided in this page on the European harmonisation measures related to the fixed service completed in 2018 and ongoing activities related to radiodetermination applications in 120-260 GHz.

CEPT regulations for the fixed service in frequencies above 90 GHz

CEPT (European Telecommunication Office) investigations on FS (Fixed Services) in the frequency ranges 92-114.25 GHz (“W-band”) and 130-174.8 GHz (“D band”) were completed in 2018 with the publication of the following deliverables:

  • ECC Report 282: Point-to-Point Radio Links in the Frequency ranges 92-114.25 GHz and 130-174.8 GHz;
  • Revised ECC Recommendation (14)01: Radio frequency channel arrangements for fixed service systems operating in the band 92-95 GHz;
  • ECC Reconditionnement (18)01: Radio frequency channel/block arrangements for Fixed Service systems operating in the bands 92-94 GHz, 94.1-100 GHz, 102-109.5 GHz and 111.8-114.25 GHz;
  • ECC Recommendation (18)02: Radio frequency channel/block arrangements for Fixed Service systems operating in the bands 130-134 GHz, 141-148.5 GHz, 151.5-164 GHz and 167-174.8 GHz

The main features that are advocated forfixed radio systems operating in this part of the spectrum are highlighted as follows:

  • Availability of very wide bandwidths, allowing for the low cost of traffic in multi service provider operation area;
  • Feasibility of deploying radio links is much easier in comparison to alternative wire-bound solutions;
  • Ability to ensure high security because of low possibility of interference/capture of signals.

The channel arrangements in ECC/REC/(18)01 and ECC/REC/(18)02 account for flexible FDD/TDD deployment, with continuous frequency slot raster of 250 MHz channels, without specifically defining either paired or unpaired use. No strict limitation on the number of aggregate channels (i.e. no limitation on the maximum channel bandwidth) is specified. Bands and Carrier Aggregation (BCA) may also be considered for the W-band and D-band to improve capacity and link availability.

Consideration is given in ECC Report 282 on current high capacity commercial systems in the E-band (71-76 GHz and 81-86GHz) allowing transport of 1 Gbit/s in a channel size of about 250 MHz, with modulation in the order of 128 QAM. Capacity demand can require aggregating channels for at least 500 MHz to a 2 GHz bandwidth. Indication is also given on maximum specificationsand capabilities, (capacity up to 6 Gbit/s using Dual Polarisation Multiplexing and modulation up to 256 QAM), which would however not meet the requirements for the foreseen future applications and use cases.

Around 15 GHz of spectrum is available in the W-band and more than 30 GHz of spectrum is available in the D-band. Optimised trade-off between very wide channels and spectrum efficiency would allow achieving very compact equipment and low power consumption for ultra-high capacity backhauling,front-hauling and possibly fixed wireless access, with up to about 1 km hop lengths in line-of-sight conditions.High density short links under 200m can be used for 5G mobile backhauling tail link with capacity of over 10 Gbit/s. Indoor application for internal connection of a data centre (inter-server) is also considered with short links in the order of tens of metres, providing capacity around 40 Gbit/s. The report also mentions link capacity in the order of 100 Gbit/s planned in the future.

For D-band systems simulation, ECC Report 282 considers maximum antenna gain of up to 40 dBi and +5 dBm output power.

As for the compatibility with passive services, the conclusions and methodologies in ECC Report 124 have been extrapolated in ECC/REC/(18)01 (D-band) and ECC/REC/(18)02 (W-band) in order to establish the FS unwanted emission mask to ensure protection of EESS (passive). This approach had been already applied to the FS band 92-95 GHz in ECC/REC/(14)01. The unwanted emissions of FS transmitters that are falling into adjacent passive bands (i.e. bands where footnote RR No. 5.340 applies) should be limited at the FS antenna port according to the same approach with a sloped decrease of the emission limit from -41dBW/100MHz at the frequency border between FS and passive services and across 1GHz of spectrum within the passive band down to the flat level of -55 dBW/100MHz,which is applied across the remaining of the passive band (see Annex 5 of ECC/REC/(18)01 and Annex 4 of ECC/REC/(18)02).

Radioastronomy service: the calculation of appropriate separation distances between FS transmitters and a radioastronomy site should be done on a case-by-case basis by the national administration.

Radiodetermination applications in 120-260 GHz

Work has been initiated in 2019 within CEPT to address the spectrum requirements expressed by ETSI on radiodetermination application within the frequency range 120 GHz to 260 GHz, as presented in ETSI TR 103 498 V1.1.1 (2019-02).

The ETSI SRdoc refers to available Ultra-Wideband (UWB) technology and to different measurement applications which cannot be conducted adequately at the moment in the SRD bands 122-123 GHz and 244-246 GHz due to the limited bandwidth. It distinguishes between applications types A, B and C, which vary from applications with potential maximum radiated emissions into the open sky in any direction outside a shielded environment, building or housing (type A) -which would be most critical regarding the generation of harmful interference into radiocommunication services- to applications emitting inside a confined and shielded environment, building or housing (type C).

In terms of regulatory approach, the reference to UWB basically suggests that the possible spectrum regulations to be developed would not be limited within the relevant spectrum allocations of the Radio Regulations and also that no protection can be granted to these radiodetermination applications. Administrations would have to assess the justification for these requirements, to consider some enforcement aspects in relation with the various specific applications, and also to consider suitable mechanisms to ensure the protection of radiocommunication services e.g. by ensuring that a required geographical separation is met in case of in-vehicle sensor applications.