New very high-speed mobile services, for applications such as enhanced internet browsing, video streaming and video calls, require significantly broader frequency channels and much more spectrum to accommodate their demands. This is a top issue in current spectrum management and a key issue for the European Parliament which is calling for at least 1200 MHz of spectrum to be made available for mobile data traffic (including the spectrum already available for mobile applications), anticipating a huge growth in demand for several years to come. Certainly the present rate of growth is remarkable. See the ECC PT1 group's survey on the growth of traffic in its Report on Mobile Broadband Landscape (September 2011) shown here in Figure 1.

Figure 1: growth in mobile data traffic in some European Countries 2007-2010

At its last plenary meeting in December 2011, the ECC took a firm step towards making this future mobile environment a reality by adopting a Decision on harmonised frequency arrangements for mobile/fixed communications networks (MFCN) in the bands 3400 - 3600 MHz and 3600 - 3800 MHz (ECC/DEC/(11)06). This ECC Decision is the result of around two years of intensive debates within ECC PT1, the ECC group responsible for International Mobile Telecommunications (IMT) systems¹, in order to identify proper harmonised frequency arrangements. This article gives some background to that decision and also outlines other initiatives now underway in these bands in order to improve the harmonisation framework.

The ECC harmonised frequency arrangements for these bands enhance the regulatory framework, and this in turn should reduce the development and implementation costs of manufacturing equipment, secure long term investments by providing economies of scale, as well as reduce the complexity of spectrum cross border coordination, allowing spectrum to be used more efficiently. The improvement of the harmonisation framework, is an important strategic objective for the ECC, particularly in the context of the current financial and economic situation.

A unique opportunity with a contiguous 400 MHz of radio frequency spectrum

Why choose these frequencies? The 3.4-3.6 GHz range has been identified for IMT in the ITU Radio Regulations since 2007. There are existing harmonisation measures in this range for fixed and broadband wireless access services (BWA). Although lower frequencies such as the 800 MHz ('Digital Dividend') and 900 MHz bands can bring mobile broadband to wider areas, in areas of greatest demand the higher capacity requirements need higher frequencies to support them (so as to provide higher bandwidths). So the ECC decided in 2007 to examine the 3.6 to 3.8 GHz band for IMT as well.

With a contiguous 400 MHz of radio frequency spectrum, these two frequency bands offer a unique opportunity to meet some of the new demands for mobile broadband. Transmission of higher data rates requires increased channel bandwidths. Technological development is ongoing for wider channel bandwidths taking us beyond the previous 5 MHz blocks: Report ITU-R M.2134² refers to a scalable bandwidth up to 40 MHz. The ECC surveyed current usages within the CEPT in these bands in 2008, and then, at the beginning of 2010, it decided to develop harmonised frequency arrangements in bands: 3.4 to 3.6 GHz and 3.6 to 3.8 GHz.

Harmonisation of frequency arrangements as a major step forward

The ECC launched this additional harmonisation activity for these bands, taking into account the regulatory framework which was already in place. An EC Decision, 2008/411/EC based on CEPT Report 15 and, which is binding for EU Member States, includes the specification of the least restrictive technical conditions. Those LRTC are based on the so-called 'Block Edge Masks' (BEM) earlier defined in ECC Recommendation (04)05, designed on the assumptions of BWA³. Also, ECC Decision (07)02⁴ designated these frequency bands to BWA but did not provide a harmonised frequency arrangement. Therefore, the ECC decided to develop the missing strategic element needed for mobile broadband: harmonised frequency arrangements for the high data rate mobile/fixed communications networks (MFCN), including IMT, utilising larger channel bandwidths than those envisaged in the existing regulatory framework. This was to be an evolution of the frequency plan rather than a requirement for the replacement of the currently deployed systems.

The ECC identified that the use of the 3600-3800 MHz band for the fixed satellite service (FSS) is generally more intensive than in the 3400-3600 MHz band. It also varies from one country to another within the CEPT across the whole band. It was also recognised that the 3400-3410 MHz band was not available for MFCN/IMT due to its use by land, airborne and naval military radars and other applications in some CEPT countries. Moreover, the current Radio Regulations context led the ECC to develop separate harmonised frequency arrangements for the 3400-3600 MHz and 3600-3800 MHz bands.

For 3600 to 3800 MHz, the ECC easily agreed on a TDD (Time Division Duplex)-based harmonised frequency arrangement with block size of 5 MHz, as shown on Figure 2 below: adjacent blocks can be combined to form higher capacity channels. This took into account the unanimous views expressed from industry, and significant technical and operational considerations. This is that the TDD mode would allow for more efficient spectrum use considering the coexistence with the existing FSS systems in the case of geographical sharing, harmonisation with countries implementing IMT only in a part of the band, etc.

Also, ECC PT1 noted that it would be beneficial to synchronise the TDD networks of different operators to avoid some blocks (the so-called 'restricted blocks') having more stringent spectrum emission requirements than necessary, as well as removing the need for frequency guard bands between operators. The ECC concluded though that the synchronisation (frames' timing and/or alignment of the uplink/downlink time slots ratio) of TDD networks of different operators in the same geographical area should be managed at a national level (e.g. voluntary agreements between operators or national regulatory measures). The use of frequency filters in base stations has also been identified as another solution to avoid restricted blocks / guardbands between those TDD networks.

The debates largely focused on the lower 200 MHz of the band (3400-3600 MHz) and, due to balanced positions expressed, decided to harmonise TDD and FDD (Frequency Division Duplex) arrangements in this frequency range with no expression of preference between them; these are shown in Figures 3 and 4. Nevertheless, the ECC will review the frequency arrangements not later than 2013, in order to identify a preferred one.

The harmonised frequency arrangements

Figure 2 Harmonised TDD frequency arrangement of the 3600-3800 MHz

Figure 3 Harmonised TDD frequency arrangement for the 3400-3600 MHz

Figure 4 Harmonised FDD frequency arrangement for the 3400-3600 MHz

This ECC Decision is expected to be progressively implemented due to the current legacy context. The administrations and regulators need flexibility to adapt the current use of these bands to national circumstances. The most suitable regulatory measures may need to be chosen at a national level. This may include a range of approaches, such as: refarming of the band, planning of renewal or extension of authorisations where BWA is to be maintained, and withdrawal of authorisations already issued but where no system has been deployed or where the systems deployed do not fulfil the obligations of the authorisations.

Other measures to improve the harmonisation

This new ECC Decision relates to the organisation of the frequencies for mobile broadband. But we are also taking three other initiatives to further improve the level of harmonisation in these frequency bands.

LRTC/BEM: There are existing technology-neutral conditions defined for the band, but these are designed for BWA. Based on a technical analysis carried out by ECC PT1, the ECC concluded that these technical conditions, currently defined in the form of Block Edge Masks (see above) are not suitable for the high data rate IMT applications provided by systems having larger channel bandwidths. The existing 3.5 GHz BEM are technically justified only when there is no commonly agreed frequency arrangement and maximum flexibility is needed. When harmonised frequency arrangements are adopted, there is no need for the unnecessarily tight BEM. Consequently, the ECC decided, as a further regulatory step, to adjust those BEM to the expected future usage in order to facilitate affordable equipment, increase spectrum efficiency (e.g. by reduced guard bands) and thus maximise the usable amount of spectrum. We expect to finalise this activity around the end of 2012.

Cross-border coordination: In order to maximise spectrum efficiency and avoid spectrum wastage, it is important to have appropriate cross-border coordination procedures and conditions applicable to services which use a given frequency range. For the band 3.4 - 3.8 GHz, ECC PT1 is working on the development of appropriate triggering coordination thresholds and other technical conditions. Additionally, ECC PT1 intends to combine several ECC Recommendations applicable to various mobile frequency bands and technologies in a single ECC Recommendation so as to develop one single document that will gather all the information in a harmonised format for all frequency bands.

Additional technical considerations: In the next few months, ECC PT1 will also focus on the coexistence between adjacent TDD networks (e.g. synchronisation, additional filtering, site coordination, restricted blocks/guard-bands), and the sharing studies between FDD and TDD systems at the 3600 MHz boundary. The assessment of the spectrum management migration issues from the current situation to the framework described in the new ECC Decision has also been identified. Of course, national regulation and competition issues are outside of the scope of this activity.

Due to the current EC Decision 2008/411/EC in force, the ECC has already informed the European Commission on the recent finalisation of these frequency arrangements. And on the result of its analysis on the non-suitability of the least restrictive technical conditions (LRTC) in force with future usage conditions as high data rate mobile/fixed communications networks expected in these bands. Under the Spectrum Decision, the ECC is ready to contribute to the enhancement of the current EC framework in force in these bands.

Ultimately, end users simply want high speed mobile applications that work, and care little about how this is achieved. That's for us to worry about and these regulatory measures are a big step towards meeting some of the future demands for mobile broadband and providing end users with the services on which they are coming to rely.

Didier Chauveau
Chairman of ECC PT1 - responsible for IMT matters

¹International Mobile telecommunications. The term IMT encompasses IMT-2000 (such as UMTS or its enhancement LTE) and IMT-Advanced (also known as "4G") systems . A wide range of systems are in competition: 6 IMT-2000 radio interfaces, 2 IMT-Advanced radio interfaces
²requirements related to technical performances for IMT-Advanced radio interfaces
³guidelines for accommodation and assignment of Multipoint Fixed Wireless systems in frequency bands 3400-3600 MHz and 3600-3800 MHz
⁴the availability of frequency bands between 3400-3800 MHz for the harmonised implementation of Broadband Wireless Access (BWA) systems