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Towards the implementation of the digital dividend
ITU–R Joint Task Group 5–6 completes its studies
 
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Alexandre Kholod
Federal Office of Communications (OFCOM), Switzerland
  John Lewis
Consultant in international spectrum management, Added Value Applications Limited

As the world goes digital, the switchover from analogue to digital television broadcasting may result in less spectrum requirement for traditional television broadcasting and the release of part of the ultra-high frequency (UHF) 470–862 MHz band for other applications. This band is allocated to the broadcasting service on a primary basis in all three ITU Regions — Region 1 (Europe and Africa), Region 2 (Americas) and Region 3 (Asia and Australasia). The UHF spectrum being potentially freed up by the switchover is referred to as the digital dividend. Actual availability of these UHF frequencies depends on national timescales for the switchover from analogue to digital television broadcasting.

A dominant issue at the ITU World Radiocommunication Conference in 2007 (WRC-07) was how to identify radio-frequency spectrum that could be used for the rapidly expanding needs of broadband wireless access systems. The UHF band is particularly attractive because radio waves can travel further and deeper within buildings than is the case in existing mobile spectrum bands.

WRC-07 identified an additional 72 MHz of frequencies in the upper part of the UHF band (790–862 MHz) for International Mobile Telecommunications (IMT) in Region 1. It allowed some countries in Region 1 to use this band immediately under certain conditions. The UHF frequencies allocated to the mobile service on a primary basis in Region 2 and Region 3 were also identified by WRC-07 for IMT use.

WRC-07 confirmed that the GE06 Agreement, adopted in Geneva at the ITU Regional Radiocommunication Conference 2006, must be respected. The GE06 Agreement covers 120 countries in Region 1 (except Mongolia) and the Islamic Republic of Iran. The agreement calls for the transition to digital broadcasting to be completed by 17 June 2015 for most of the countries. WRC-07 said that if, before that date, countries wish to implement mobile services in the band 790–862 MHz, they should prevent interference with broadcasting services that are still operating in that band. And before putting such mobile services into operation, agreements must be obtained from neighbouring countries.

Recognizing the potential for interference between the mobile service and other primary services in the band 790–862 MHz, WRC-07 also decided in Resolution 749 (WRC-07) that the ITU Radiocommunication Sector (ITU–R) would conduct technical studies on the sharing between the mobile and other allocated services in the band in Regions 1 and 3.

The results of these studies will be reported to the World Radiocommunication Conference 2012 (WRC-12) under Agenda item 1.17 in order to ensure the adequate protection of services to which the frequency band 790–862 MHz is allocated, and take appropriate action.

In view of the complexity and importance of the issues related to Agenda item 1.17, a dedicated Joint Task Group 5–6 (JTG 5–6) was established under the chairmanship of Alexandre Kholod. The Conference Preparatory Meeting (CPM) for WRC-12 set out the terms of reference of JTG 5–6. In particular, it mandated JTG 5–6 to study how the mobile service can share the relevant band with the broadcasting, aeronautical radionavigation and fixed services.

Meetings of Joint Task Group 5–6

Around 180 participants attended the five JTG 5–6 meetings and submitted some 180 input contributions, showing the importance administrations and Sector Members attach to the work of the group.

JTG 5–6 completed its work in May 2010, and has prepared a draft text on Agenda item 1.17, which will be considered by the Special Committee on Regulatory/Procedural matters, as well as by the second session of the Conference Preparatory Meeting in 2011. In addition, JTG 5–6 put together a compendium of the materials it received and considered. This compendium can be used by ITU–R Study Groups 5 and 6 in the development of ITU–R Recommendations or reports.

Views differed about the studies called for in Resolution 749 (WRC-07). In particular, there was disagreement about whether or not the protection of the mobile service against interference from other services (such as the broadcasting service) fell within the scope of Agenda item 1.17.

JTG 5–6 noted that the band 790–862 MHz had been allocated to the mobile service in Region 3 and in a number of countries in Region 1 by conferences prior to WRC-07, under conditions stipulated in the relevant footnotes of the Final Acts of those conferences.

Adjacent channel interference might occur if only part of the 790–862 MHz band is used for the mobile service. JTG 5–6 agreed that, within a given country, such interference is a national matter to be resolved by the administration of that country. JTG 5–6 further concluded that adjacent band interference (i.e. below 790 MHz and above 862 MHz) should be treated by the administrations concerned, using mutually agreed criteria or those contained in relevant ITU–R Recommendations. From a technical point of view, the evaluation of adjacent channel interference within the band 790–862 MHz is likely to be the same as at the band limit of 790 MHz.

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Photo credit: AFP

Methods to resolve the sharing issues in the band 790–862 MHz

Sharing between terrestrial services in Region 3 is to be based on negotiations between the administrations concerned. However, there are a number of conflicting provisions with regard to sharing between the countries of Regions 1 and 3. First, the GE06 Agreement introduces the notion of broadcasting allotments, which are not taken into account when non-contracting parties make their own frequency assignments (under Radio Regulation No 11.31). Second, there is an allocation for the aeronautical radionavigation service in Region 1. Third, there is no formal coordination requirement between the terrestrial services in Regions 1 and 3 — although these services have been operated successfully to date without any requirements in the Radio Regulations. JTG 5–6 managed to balance these provisions and suggest a fair way of coordinating the operation of services between Regions 1 and 3. This method is optional in nature and is reflected in a new Resolution [JTG 5–6] proposed for adoption by WRC-12.

For contracting parties, the GE06 Agreement contains all the required technical and regulatory mechanisms (coordination procedures) for the protection of the broadcasting service from the mobile service. In its studies, JTG 5–6 investigated the potential impact of a mobile service implemented by one administration on a frequency used by another administration for its broadcasting service network. These studies particularly addressed the potential aggregated effect of multiple base stations on the coordination trigger field strength defined by the GE06 Agreement. They demonstrate that the cumulative effect of interference from base stations that individually do not trigger the need for coordination with the broadcasting service could be significant.

However, a number of factors, such as mobile network design or interference from coordinated base stations situated close to the border, suggest that the potential impact of cumulative interference might be less significant in practice. Alternatives (optional, mandatory or no additional arrangements) to take account of the potential impact of the cumulative effect of interference from the mobile service to the broadcasting service are addressed in the draft CPM text.

No consensus was reached on a proposal to deactivate the agreement-seeking procedure in Nos. 9.21 and 5.316B of the Radio Regulations, and replace it by procedures for coordination between countries implementing the mobile service and countries listed in No. 5.312 continuing to operate the aeronautical radionavigation service (ARNS). Some administrations expressed the view that this would be a balanced approach to ensuring protection to ARNS, while providing conditions for equitable access to spectrum by both ARNS and the mobile service after 17 June 2015. Others took the view that the approach is based on purely procedural considerations and is not supported by any of the sharing studies required by the terms of reference of JTG 5–6. The different views are reflected in the draft text for the CPM report.

Choices to be made

JTG 5–6 could not reach consensus on solutions for all of the sharing issues considered under Agenda item 1.17. As a result, in some cases, JTG 5–6 proposes more than one option for resolving the problems. Administrations and Sector Members will need to conduct further studies to reduce the number of options.

For the sake of the digital dividend, administrations will have to compromise, and make good use of the time remaining before the Conference Preparatory Meeting in 2011 and the World Radiocommunication Conference in 2012 to find acceptable solutions.

 


* This article continues the discussion of the digital dividend started in the January 2010 issue of ITU News.

 

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