Europe prepares to harmonise the 6 GHz spectrum band for Radio Local Area Networks

With wireless access systems set for rapid growth, there is a push in Europe to open the new band, writes Doriana Guiducci, Spectrum Expert, European Communications Office

Whereas it was once confined to large buildings and few homes, Wi-Fi has become ubiquitous in our lives. Today, smartphone, tablet and laptop users have access to Wi-Fi on public transport, in small cafes and even in public parks.

It's all thanks to wireless access systems including radio local area networks (WAS/RLANs), which are intended to cover smaller geographic areas like homes or offices, with WAS/RLAN deployments providing broadband wireless access in public locations such as airports, railway stations, conference centres and hotels. WAS/RLANs are also used to provide network access on trains, buses, cars or aboard aircraft.

In addition, the provision of free connectivity for citizens in public spaces including parks, squares, public buildings, libraries and museums is becoming more and more popular, as evidenced for example by the WiFi4EU initiative in the European Union, which promotes free access to Wi-Fi connectivity in such places throughout Europe.

Billions of WAS/RLAN devices are already in operation, and rapid growth is expected in the foreseeable future. Equipment will use different power levels and different technologies to meet the demand for greater throughput for advanced wireless applications. Based on current market share projections, the dominant technology is likely to be IEEE 802.11-based, although uptake of unlicensed cellular technologies (Licensed Assisted Access, MulteFire and 5G New Radio) is also expected.

Currently, the main frequency bands used by WAS/RLANs are in the 2.4 GHz and 5 GHz ranges. The frequency range 2400-2483.5 MHz is designated for industrial, scientific and medical (ISM) applications and radiocommunication services operating within these bands must accept harmful interference possibly caused by these applications. This frequency band is available for short range device (SRD) applications on a global basis. In Europe, ERC Recommendation 70-03 (Annex 3) covers frequency bands and recommends regulatory as well as informative parameters for Wideband Data Transmission Systems. The use of the 5150-5350 MHz and 5470-5725 MHz bands for WAS/RLANs is harmonised by ECC Decision (04)08, currently under revision, while ERC Recommendation 70-03 (Annex A) includes references to the harmonised European standard and national implementation information. WAS/RLAN use is also possible under the existing SRD regulation in the frequency band 5725-5875 MHz as per ERC/REC 70-03 Annex 1.

However, the increasing demand for spectrum for WAS/RLANs has already triggered several actions, with the aim of identifying bands that offer sufficient capacity. Such bands include the 57-71 GHz range for which the relevant regulation has been recently updated by ECC. CEPT has also assessed if proper conditions and mitigation techniques would allow additional WAS/RLAN use in the 5 GHz range; this task is part of the preparation of the upcoming World Radiocommunication Conference (WRC-19). Though, CEPT is of the view that no change to the Radio Regulation has to be applied except for the 5150-5250 MHz band, in line with ECC Decision (04)08. In that band, CEPT supports in-car usage up to 40 mW and in-train usage up to 200 mW e.i.r.p. It is also in favour of limited outdoor use with a maximum of 200 mW e.i.r.p.

In this situation, the possible opening of the 6 GHz band to WAS/RLAN is gaining momentum within Europe and beyond to provide an adequate amount of spectrum and to use channels with a bandwidth of up to 160 MHz. Last October, the Federal Communications Commission in the US proposed rules to promote new opportunities for unlicensed use in the 5925-7125 MHz band, while ensuring that licensed services already operating in the band continue to do so. A strong interest on this proposal has been registered both from the RLAN and cellular telecommunications community, and the discussion is still ongoing. ECC has been exploring further opportunities to make spectrum in the 5925-6425 MHz band available for WAS/RLANs, while protecting other radio services and applications currently in use.

In particular, in May 2017, a work item was created within ECC to study the technical feasibility of the introduction of low power WAS/RLAN in the band 5925-6425 MHz on a non-protected basis while ensuring certainty of continued operation, development and protection of existing services. ETSI was simultaneously developing Technical Report 103 524 with the System Reference Document on WAS/RLANs in the 5925-6725 MHz band.

The ETSI Technical Report was published in October 2018 and contains information to support CEPT activities covering the band 5925-6425 MHz, as per the co-operation between ETSI and ECC. It provides justification for additional licence-exempt spectrum for WAS/RLANs, and requests modifications to the regulatory rules of the 5925-6725 MHz frequency range. This would enable the operation in this band of WAS/RLANs which implement advanced spectrum-sharing techniques as appropriate. Nonetheless, frequencies above 6425 MHz are not under consideration by ECC.

In December 2017, CEPT received the Mandate from the European Commission (EC) to study and identify harmonised technical conditions for WAS/RLANs in the 5925-6425 MHz band for the provision of wireless broadband services. The Mandate presents two tasks that CEPT has to address by July 2020 with different timelines. Task 1 regards the study of compatibility and coexistence scenarios in the band 5925-6425 MHz, as well as the identification of relevant parameters and coexistence conditions to be implemented in the regulatory framework. These would enable coexistence between existing uses and WAS/RLAN systems. Task 2 deals with the development of harmonised technical conditions which would ensure operation of WAS/RLAN on a coexistence basis with the incumbent uses, taking into account possible mitigation techniques.

As a result of this work, ECC Report 302 was published in May 2019 and contains studies between WAS/RLAN systems and existing incumbents in the 5925-6425 MHz band and adjacent bands. In line with the European Common Allocations Table, which shows fixed, fixed-satellite and mobile as primary services allocated in the 5935-6425 MHz and adjacent 5850-5925 MHz band, the studies assess coexistence and compatibility scenarios between WAS/RLAN and the fixed service, the fixed-satellite service, as well as road intelligent transport systems and communication-based train control in the adjacent band. The radio astronomy service has also been taken into account, as some portions in the 6 GHz range are of importance for the observation of methanol and hydroxyl. Coexistence with ultra-wide band (UWB) systems has also been considered, bearing in mind that UWB devices are only authorised on a non-interference and non-protected basis. No change to existing regulations around UWB is foreseen.

Communication-based train control systems are used in some metropolitan cities in France (5915-5935 MHz), Denmark (5925-5975 MHz) and Spain (5905-5925 MHz) and some projects are planned in Austria, Belgium, Denmark, France, Germany and Spain. It´s worth noting that ECC agreed to propose the harmonisation of the 5925-5935 MHz band for safety-related urban rail intelligent transport systems applications, subject to national coordination with existing fixed-service networks and/or national studies to determine the sharing conditions. This is specified in CEPT Report 71, published in response to the EC Mandate to CEPT on intelligent transport systems. Therefore, adjacent compatibility studies between communication-based train control in the 5915-5935 MHz band and WAS/RLAN above 5935 MHz are specifically addressed in light of this proposal. Further details on this harmonisation activity for urban rail in Europe are available in the article on spectrum for railway mobile applications which is also available in this edition of the ECC Newsletter.

The assessment of sharing and compatibility scenarios in ECC Report 302 aims to identify technical conditions which would enable coexistence between existing uses and WAS/RLAN systems, without constraining incumbents in CEPT countries. The statistical and worst-case scenario studies rest on an agreed set of inputs. These include parametric inputs and distributions for scenarios based on models of 2025 deployments for WAS/RLAN, with power up to 1 W e.i.r.p., outdoor devices, and scenarios that assume indoor-only usage.

Based on the results of ECC Report 302, CEPT has now developed Draft Report 73 in response to the Task 1 ̶ the feasibility of coexistence scenarios for WAS/RLAN in the band 5925-6425 MHz ̶ of the EC Mandate to CEPT. Draft CEPT Report 73 is under public consultation and provides an assessment of the technical studies and the feasibility of some of the regulatory models which could be implemented for WAS/RLAN in the 5925-6425 MHz GHz band.

According to the studies conducted so far, CEPT expects that compatibility and coexistence between WAS/RLAN and existing services within and adjacent to the band 5925-6425 MHz is technically feasible under certain conditions. In particular, for scenarios with indoor-only deployment with a maximum e.i.r.p. in the range of 200-250 mW, the studies indicate that coexistence is feasible with fixed satellite services and with fixed services when considering the long-term aggregated interference protection criterion.

Coexistence with communication-based train control systems and road-intelligent transport systems would be technically feasible assuming suitable measures are implemented such as a guard band and requirements on WAS/RLAN in-band and/or out-of-band emissions. These measures would limit the available spectrum for WAS/RLAN to less than the entire 5925-6425 MHz band.

Other high-power and outdoor devices present a risk of harmful interference to the incumbents when sharing the band without restrictions.

The new Draft CEPT Report, which is being developed in response to Task 2 - the development of harmonised technical conditions - of the EC Mandate, will provide a regulatory framework including all relevant technical conditions. It will also address possible mitigation techniques and the use of geolocation methods. ECC has now started complementary studies and analyses in support of this new CEPT Report. It aims to address the short-term protection of point-to-point fixed services from WAS/RLAN indoor-only deployment, as well as from potential WAS/RLAN portable devices which operate outdoor with power levels significantly lower than those for indoor use. These additional studies may consider the design criterion and the link budget margins typically applied across CEPT when planning point-to-point links in this band. They should aim to quantify and qualify both the risk and possible effect of short-term interference occurring with respect to fixed-link availability at different WAS/RLAN maximum power levels.

A new work item has also been approved by ECC to develop a Decision to define harmonised technical conditions for WAS/RLANs in the 5925-6425 MHz band for the provision of wireless broadband services. This ECC Decision will be developed taking into account the results of ECC Report 302 and CEPT Reports in response to the EC Mandate, and should be based on the expectation of free circulation and use under a licence-exempt regime. With this Decision, expected by the end of 2020, ECC will develop a framework for the 48 CEPT countries in parallel to the ongoing process in the European Union. This timely development of a framework for WAS/RLAN in the 6 GHz band will provide regulatory certainty to industry and will place Europe in a leading position to pave the way for future broadband connectivity based on unlicensed regimes.