National Autonomy in the Use of Spectrum in the UK – Part 1 Technical Options Final Report to Ofcom March 2004

National Autonomy in the use of spectrum in the UK – Part 1

Technical options

Final report to Ofcom

March 2004

Contributors: Chris Davis John Berry Nick Kirkman Charles Chambers

Quotient Associates Limited ATDI Limited PO Box 716 15 Kingsland Court Comberton Three Bridges Road, Crawley Cambridge, CB3 7UW West Sussex, RH10 1HL

E-mail: [email protected] E-mail: [email protected] Web: www.QuotientAssociates.com Web: www.atdi.co.uk National Autonomy – Technical options Contents

CONTENTS Page

1. Introduction ...... 1 1.1 Project objectives...... 1 1.2 Our approach ...... 1 1.3 Technical options ...... 3

2. Development of scenarios ...... 4 2.1 Initial ideas ...... 4 2.2 Selection of scenarios...... 5 2.3 The Workshop...... 6

3. Broadcasting on Public Correspondence channels ...... 9 3.1 Objective ...... 9 3.2 Background...... 9 3.3 The scenario ...... 9 3.4 Results ...... 11 3.5 Conclusions ...... 11 3.6 Tentative assertions...... 12

4. VHF sound broadcasting in the 68 - 88 MHz band ...... 13 4.1 Objective ...... 13 4.2 Background...... 13 4.3 The scenario ...... 13 4.4 Results ...... 15 4.5 Conclusion ...... 18 4.6 Tentative assertions...... 18

5. Wide band PMR in Band III...... 19 5.1 Objective ...... 19 5.2 Background...... 19 5.3 The scenario ...... 20 5.4 Results ...... 21 5.5 Conclusion ...... 23 5.6 Tentative assertions...... 23

6. Unrestricted wide band PMR at 450 - 470 MHz...... 24 6.1 Objective ...... 24 6.2 Background...... 24 6.3 The scenario ...... 25 6.4 Results ...... 26 6.5 Tentative assertions...... 29

7. UTRA TDD in spare DVB-T channels...... 30

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© 2004. Hard copies or higher resolution versions of the documents are available on application to the Ofcom Contact Centre, Riverside House, 2a Southwark Bridge Road, London SE1 9HA. National Autonomy – Technical options Contents

CONTENTS Page

7.1 Objective ...... 30 7.2 Background...... 30 7.3 The scenario ...... 31 7.4 Results ...... 32 7.5 Tentative assertions...... 35

8. Fixed wireless access in the 900 MHz TETRA band ...... 36 8.1 Objective ...... 36 8.2 Background...... 36 8.3 The scenario ...... 36 8.4 Results ...... 37 8.5 Conclusion ...... 39 8.6 Tentative assertions...... 40

9. Refarming of GSM spectrum to UTRA...... 41 9.1 Objective ...... 41 9.2 Background...... 41 9.3 The scenario ...... 42 9.4 Results ...... 43 9.5 Conclusions ...... 49 9.6 Tentative assertions...... 49

10. Terrestrial DAB local radio at 1800 MHz...... 50 10.1 Objective ...... 50 10.2 Background...... 50 10.3 The scenario ...... 50 10.4 Results ...... 51 10.5 Conclusion ...... 54 10.6 Tentative assertions...... 55

11. Part of the 1800 MHz band re-allocated to Fixed Links ...... 56 11.1 Objective ...... 56 11.2 Background...... 56 11.3 The scenario ...... 56 11.4 Results ...... 57 11.5 Conclusion ...... 61 11.6 Tentative assertions...... 61

12. Portable wireless DSL in the 2010 to 2025 MHz band...... 62 12.1 Objective ...... 62 12.2 Background...... 62 12.3 The scenario ...... 63 12.4 Results ...... 64

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CONTENTS Page

12.5 Coordination with fixed links in France ...... 67 12.6 Conclusion ...... 67 12.7 Tentative assertions...... 68

13. Fixed links in the 2.7 - 2.9 GHz Aeronautical band...... 69 13.1 Objective ...... 69 13.2 Background...... 69 13.3 The scenario ...... 69 13.4 Results ...... 70 13.5 Conclusion ...... 72 13.6 Tentative assertions...... 72

14. FWA spectrum at 3.5 GHz is returned to ENG/OB use ...... 74 14.1 Objective ...... 74 14.2 Background...... 74 14.3 The scenario ...... 74 14.4 Results ...... 75 14.5 Conclusion ...... 77 14.6 Tentative assertions...... 77

15. Terrestrial fixed services at 32 GHz...... 78 15.1 Objective ...... 78 15.2 Background...... 78 15.3 The scenario ...... 78 15.4 Results ...... 80 15.5 Tentative assertions...... 81

16. Technical options ...... 83 16.1 Options applicable to the scenarios modelled ...... 83 16.2 Other options ...... 84 16.3 Conclusion ...... 86

17. Summary and conclusion...... 87 17.2 Results ...... 88 17.3 Conclusions ...... 92 17.4 Northern Ireland ...... 93

18. Annex A ...... 97 18.1 The Essence of the Tool ...... 97 18.2 Path Modelling ...... 97 18.3 Interference Modelling ...... 98 18.4 Reporting ...... 99

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1. INTRODUCTION

1.1 Project objectives

The overall objectives of the National Autonomy project are to develop an understanding of the extent to which it would be feasible for the UK to make more flexible use of the spectrum whilst still behaving responsibly towards its neighbours and meeting its international treaty obligations. The key interest is in opportunities that would arise from not adhering to harmonised applications and standards but remain consistent with Article 5 of the Radio Regulations. Nevertheless, it is important to explore the opportunities to make spectrum available without any restrictions on the application. This project therefore considers different levels of flexibility (referred to here as different degrees of autonomy1) and the corresponding regulatory situations.

The project is divided into four parts; the objectives of each part are as follows:

Part 1: For a range of services and frequency bands, to determine the technical conditions under which autonomous use of the spectrum could be achieved;

Part 2: To quantify the technical consequences of autonomous use of the spectrum for a set of example cases. These results are used by the parallel International Harmonisation project which seeks to quantify the potential economic benefits of autonomous spectrum use;

Part 3: To identify in outline additional opportunities for autonomous use of other parts of the spectrum;

Part 4: To identify the risk and consequential impact of subsequent changes in the international regulatory environment that could affect autonomous use.

Part 1 is reported on here with the other Parts being the subject of separate reports.

1.2 Our approach

In order to obtain as realistic a view as possible consistent with the project scope it was decided that a set of scenarios should be modelled in some detail. The results then provide data on the extent to which particular parts of the spectrum can be used

1 Throughout this report, where spectrum is used autonomously of harmonised standards or applications, or outside the scope of the ITU-R Frequency Allocation Table, we will refer to systems and operations using this spectrum as autonomous. Note that, within the context of this study, autonomous operation does not imply there will be no coordination with neighbouring Administrations. Whilst this may be appropriate where operation is on a no interference, no protection basis, there will need to be cross border agreements in other situations.

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autonomously for specific applications and, with further analysis, can be used to identify more general conditions for autonomous operation.

It should be noted that the examples of autonomous use (the scenarios) referred to in this report have been developed solely for the purposes of this study. They in no way reflect the views, plans or expectations of Ofcom and no inferences can be drawn from their inclusion the study.

This approach relies on the selection of an appropriate set of scenarios which must encompass a suitable range of frequencies, services, technologies and regulatory regimes. A significant effort in the early part of the project was therefore devoted to the careful selection of these scenarios. The process and results are described in Chapter 2 of this report.

The extent to which a particular part of the spectrum may be used autonomously depends in large degree on the extent to which the applications on either side of the border can co-exist, and in particular on the level of interference that the autonomous system can both export and tolerate. Co-existence for each scenario was therefore modelled using the radio planning tool ICS Telecom from ATDI. The results for each scenario and overall conclusions are given in the later sections of this report.

In developing the scenarios and undertaking the modelling a number of general principles were followed.

5What might constitute an acceptable level of interference in particular circumstances and what levels of cross border emissions neighbouring Administrations may consider reasonable are important parameters in each scenario, and clearly can have a significant impact on the usability of systems operating autonomously. Wherever possible, therefore, these levels were derived from existing bi-lateral or multi-lateral cross border agreements, from CEPT, ERC or ECC Recommendations, or from ITU-R Recommendations. In some cases, alternative protection criteria were considered both to identify how different regulatory regimes would affect the conclusions and to obtain an understanding of the sensitivity of the results to the levels chosen (see Chapters 4, 8 and 10).

5Propagation modelling was always based on the ITU-R model appropriate to the frequency and application, or on the model defined in the relevant cross border agreement or recommendation.

5Since the objective is to understand the extent to which autonomous use of spectrum might be practical modelling, of most scenarios was confined to the path estimated to lead to the most restrictive conditions.

5Similarly, only cross border issues have been addressed here. Issues of compatibility between autonomous applications and existing applications operating in adjacent spectrum are not addressed here.

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5Relevant equipment parameters were taken from existing commercial equipment or, where that was not possible, from relevant standards.

A description of ICS Telecom is given in Annex A of this report and comprehensive details of the modelling undertaken for each scenario are given in separate appendices.

1.3 Technical options

The work reported here considers what technical options would be available to mitigate the impact of cross border interference. However, autonomous use of spectrum could also be enhanced through the use of more advanced assignment techniques, perhaps ultimately taking account of actual interference levels rather than predicted ones. This issue is considered, and a phased implementation approach is outlined, in the report “Smart spectrum management methods, URS for software tools” developed as part of this project.

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2. DEVELOPMENT OF SCENARIOS

The ITT identified a number of frequency bands and applications thought likely to provide good candidates for autonomous use of the spectrum, and these were used as the starting point for the development of the scenarios. In order to explore future as well as current possibilities a broad range of ideas were developed initially. It was agreed that these should not be overly constrained by currently available equipment but, nevertheless, that all assumptions should be based on known technical capabilities. The initial ideas were then refined through a number of steps. The process is illustrated in Figure 2.1 and outlined below.

Status of bands + Ideas RARA & & Harmonisation Harmonisation Study Study

Initial list of scenarios

Short list of scenarios Initial filter

Rank according to Selection selection criteria criteria

Workshop Review & finalise selection Figure 2.1: The process used to develop and select the scenarios for analysis.

2.1 Initial ideas

The first step was to identify the current status of the bands of interest including the current use, usage in neighbouring countries and key issues and/or strategic plans that the Agency might have. At the same time the current regulatory regime was identified and all the information was collected in a working report. As the information was collected ideas for scenarios were generated. Additional ideas came from discussions with Agency personnel, from the parallel Harmonisation Study and from an internal Agency workshop. Some 40 ideas were assembled at this stage.

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The list was then filtered to remove scenarios which were clearly impractical or which duplicated or closely overlapped with others. The resulting short list for further consideration consisted of 21 scenarios.

2.2 Selection of scenarios

The next step was to select the final set of scenarios for modelling and analysis. This was performed in four steps:

5Firstly, detailed descriptions of the 21 scenarios were developed both to identify the situation in more detail and to determine the information likely to be gained towards the study;

5Secondly, a set of criteria was developed against which the scenarios could be judged;

5Thirdly, the scenarios were ranked based on the criteria;

5Fourthly, the criteria and the ranking of scenarios was reviewed and revised in a Workshop held with Agency personnel.

2.2.1 The selection criteria

The selection criteria were based on the overall objectives of the project as given in the previous chapter and were used to rank the scenarios in terms of their relative importance to this study. They were:

1. Very important scenarios (indicative score 5):

5Involve a change of Service and/or application away from existing harmonisation initiatives, or Services which are likely to be subject to a major change;

5Some should attempt to push the bounds of autonomous use (e.g. go against Article 5 of the Radio Regulations);

2. Important scenarios (indicative score 3) involve:

5Services or frequency bands where there is a spectrum shortage;

5Services which make a significant contribution to the UK GDP;

5Services or frequency bands where major change is likely over the next 5 to 10 years.

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3. Less important scenarios (indicative score 1) involve:

5Only a change of technology.

In addition the scenarios had to be practical, but not overly constrained by the availability of equipment today, and the final set needed to cover a range of frequency bands, regulatory environments and services.

2.3 The Workshop

The Scenario Workshop was an important part of the selection process. By bringing together the project team and Agency personnel expert in different areas of spectrum management it was possible to review and confirm both the selection criteria and the practicality of each scenario. The Workshop then debated the relevance of each scenario to current Agency issues and where appropriate modified the score allocated. The debate was particularly constructive and led to the inclusion and selection of an additional scenario.

Finally, the highest scoring scenarios were selected for modelling and a check made that the necessary range of frequency bands, services, technologies and regulatory regimes, were included. The scenarios selected are listed in Table 2.1.

Following the Workshop, the scenario descriptions were finalised with the details of the technologies, the protection needs, and the regulatory regime assumptions. These descriptions formed the basis for the subsequent modelling. They are included in the separate appendices which provide a full description of each scenario and the modelling undertaken.

Throughout this process liaison was maintained with the Harmonisation Study to ensure that the quantitative results required by that study would be provided. It was agreed that a quantitative analysis would be undertaken for five of the scenarios, and these are identified in Table 2.1.

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Table 2.1

Scenario Regulatory status

1 Use of HF Public Correspondence frequencies for local area Outside FAT therefore operates on NINP basis. broadcasting (around 15 MHz)

2 Extension of analogue VHF sound broadcasting into the 68 - 88 Outside FAT and ECAT therefore operates on a NINP basis. MHz mobile band

3 France migrates Band III TV service to DVB-T & the UK assigns Within FAT Footnote (excluding the Republic of Ireland) and in wide band (200 kHz) PMR in Band III line with current UK / France MOU.

4 Unrestricted assignment of wide band (200 kHz) digital PMR in In conformance with FAT and ECAT but out of line with ECC the 450 – 470 MHz mobile band Recommendations on the introduction of wide band digital PMR.

5 3G mobile operators deploy UTRA TDD in spare UHF TV Outside FAT primary allocation between 470 - 790 MHz but channels within Footnote (excluding Belgium and Republic of Ireland). Would operate on an NINP basis.

6 Fixed wireless access in the 900MHz TETRA band Within FAT but outside ECAT and harmonisation of band for digital PMR.

7 Refarming the GSM 900 MHz and 1800 MHz spectrum to IMT- In conformity with FAT and ECAT but potentially out of line with 2000 ECC harmonisation initiatives.

8 Terrestrial DAB-based local radio in the 1800MHz mobile band Outside FAT and ECAT therefore operates on a NINP basis.

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Commercial in Confidence. No part of the contents of this document may be disclosed, used or reproduced in any form, or by any means, without the prior written consent of Quotient Associates Ltd. National Autonomy – Technical options Development of scenarios

Scenario Regulatory status

9 Part of the 1800MHz mobile band re-allocated to Fixed Links Within FAT and ECAT but disregards harmonisation of the band for digital cellular use.

10 FWA/Mobile (802.20 or similar) in the UTRA TDD band 2010 to Within FAT and ECAT but outside harmonised allocation to IMT- 2025 MHz 2000.

11 Fixed links in the Aeronautical Radiolocation band 2.7 to 2.9 Outside FAT and would operate on an NINP basis. GHz

12 FWA spectrum at 3.5GHz is returned to ENG/OB use for Within FAT and ECAT. temporary fixed links

13 Relaxation of technical standards and channel plans for In line with FAT but ignores harmonised standards and channel terrestrial fixed services at 32 GHz plans.

Table 2.1: The final set of scenarios selected for modelling in ascending order of frequency. (The following abbreviations are used: FAT – ITU-R Frequency Allocation Table for Region 1; ECAT – the European Common Allocation Table; NINP – no interference, no protection.)

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3. BROADCASTING ON PUBLIC CORRESPONDENCE CHANNELS

3.1 Objective

The objective of this scenario is to identify the practicality of using HF frequencies for applications within the borders of the UK.

3.2 Background

Generally speaking HF frequencies are used for long distance communications and a range of specific frequencies may be assigned to a particular service to ensure that communication can be achieved throughout the day. Allocations within the band are largely to the Fixed, Broadcasting, and the Aeronautical and Maritime Mobile services. Other uses of the band include SRDs and, at the higher frequencies, paging and Citizens Band.

With the wide spread use of cellular and satellite phones, the use of maritime Public Correspondence channels has very largely ceased in Western Europe. In the UK, the ship to shore phone service was closed a few years ago when no-one was prepared to take over the service from BT and, as a result, there are several Public Correspondence channels across the HF band which are no longer used.

In addition to the continuing demand for commercial broadcasting frequencies there is also strong interest from a number of special interest groups who would like to broadcast to their local community.

This scenario therefore considers the possibility that some of the disused Public Correspondence frequencies could be assigned to groups, such as churches, for local broadcasting purposes.

3.3 The scenario

In this scenario we imagine that a number of Public Correspondence channels, between 15 MHz and 19 MHz, are assigned to religious and other groups for the purpose of broadcasting to their local community. Because these channels are allocated to the Maritime Mobile service, their use for broadcasting has to be on the basis of no interference and no protection. Licences are therefore issued with the maximum transmit powers limited to that necessary to cover the local community, with an upper limit of 20W ERP.

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To model this situation a transmitter with an ERP of 20W, operating at around 17 MHz was placed in the south of England. The range2 achieved was checked for representative HF broadcast receivers (see Figure 3.1) and was found to be around 15 km which is considered adequate for most local communities.

Figure 3.1: Field strengths from a 20W ERP transmitter at 17 MHz. The minimum usable signal is 20 dBµV/m3 giving a range of ~15 km and a coverage area of ~700 km2.

To determine whether or not such a transmission in the UK would cause co-channel interference to other users, a Public Correspondence channel was selected (17258.4 kHz) and the current co-channel users determined. Five such users were found between Tokyo and Rome. The level of interference that would be caused by the UK transmitter was then calculated for each one.

Both the broadcast station and the residential receivers were assumed to use sleeved dipole antennas. A channel bandwidth of 3 kHz was assumed.

2 The ground wave propagation model was based on ITU-R Recommendation P.368 and the sky wave model on ITU-R Recommendation P.533. Near Vertical Incident Skywave was also considered here but needs to operate at less than about 8 MHz to achieve reliable propagation.

3 The minimum usable signal was calculated taking account of man made noise in residential areas and a C/I requirement of 10dB.

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3.4 Results

The signal from the UK transmitter was deemed to cause noticeable interference if it exceeded a 5dB signal to noise ratio at the victim location4. The percentage of time that interference would be noticeable was then determined for frequencies between 15 MHz and 19 MHz for two different sun spot numbers. The results are tabulated below.

Percentage of time with Distance from interference the UK (km)

Sun spot number Sun spot number 20 150

Rio, Brazil 0% 0% 9190

Tokyo, Japan 0% 0% 9580

Istanbul, Turkey 35% 52% 2500

Rome, Italy 19% 35% 1440

Reykjavik, Iceland 4% 28% 1890

Table 3.1: The percentage time that a signal from a 20W ERP UK transmission between 15 and 19 MHz5 would exceed a signal to noise ratio of 5dB is shown for different sun spot numbers. In each case, the percentage is the average for February, June and October.

A supplementary estimate shows that reducing the transmitted power to 1W ERP would increase the signal to noise ratio to such an extent that the interference would likely not be noticeable. In this case, however, the range achieved in the UK would reduce to 7 km (equivalent to the light blue area (30 dBµV/m) in Figure 3.1) and be of limited usefulness.

3.5 Conclusions

Three conclusions can be drawn from Table 3.1:

5Firstly, there are co-channel assignments to Public Correspondence channels that would suffer interference from 20W ERP transmissions in the UK;

4 A S/N ratio of 5 dB was chosen as an interfering signal at this level is very likely to be noticeable at the victim system. However, the results inTable 3.1 are insensitive to the specific value selected.

5 Similar results are obtained for frequencies up to 24 MHz.

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5Secondly, the duration of the interference would be long enough to disrupt local use of the frequencies (and long enough for interference from these co-channel users to disrupt its use for broadcast purposes in the UK).

5Thirdly, co-channel assignments have to be several thousand kilometres distant in order that interference is not be an issue.

Overall, we can conclude that the general use of HF frequencies without international coordination will only be possible at low radiated powers of the order of 1W ERP or less. And, at this level, the range achievable will severely limit the usability of these frequencies.

It is worth noting, however, that the hours each day during which interference will occur are predictable. Non-time sensitive applications might therefore be able to make use of these frequencies. Applications which transmit in short bursts, and which operate to a “listen before transmit” protocol might be able to make use of these frequencies on an un-coordinated basis.

3.6 Tentative assertions

We will use the results of all scenarios to develop a set of general conclusions on the autonomous use of spectrum and the attributes that make specific parts more or less suited to autonomous use. At this stage, we have extracted some initial assertions based on the results of individual scenarios. For this scenario they are:

5HF frequencies cannot generally be used without international coordination;

5Nevertheless, applications requiring very short ranges (of a few kilometres only), or able to make use of times when skywave propagation is known to be poor, or requiring to transmit for short periods of time, may be able to use these frequencies without causing noticeable interference.

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4. VHF SOUND BROADCASTING IN THE 68 - 88 MHZ BAND

4.1 Objective

This scenario considers the practicality of operating local analogue sound broadcasting on a no interference, no protection basis in a VHF mobile band.

4.2 Background

With the exception of frequencies between 74.8 and 75.2 MHz, the whole of the band 68.0 to 87.5 MHz is allocated to Fixed and Mobile Services on a co-primary basis in the ITU-R Frequency Allocation Table for Region 1 (the FAT). With the same exception, the European Common Allocation Table (the ECAT) allocates the band to the Mobile Service only on a primary basis. Again with the same exception, the UK has allocated the band on a primary basis to Land Mobile except that between 78 and 88 MHz Fixed Services are included on a co-primary basis.

The band is commonly used for PMR operations in European countries. In the UK it is also largely used for PMR along with CT0 (to be phased out), some military mobile communications, and PMSE talk back. However, the band is not heavily used in the UK and future demand for PMR assignments in this band is expected to be light.

4.3 The scenario

There are now around 250 national and local commercial radio stations in the UK and there is a continuing demand for more licences. A recent review by the Agency concluded that there was scope for additional licences to be issued in urban areas for services with coverage limited to a radius as little as 5 km. The same review concluded that it was unlikely that larger scale services could be introduced under the current planning criteria6. This scenario therefore considers the situation in which the 68.0 to 87.5 MHz band is re-organised to release spectrum for use for VHF broadcast services.

As noted above the FAT makes no allocation to Broadcasting in the band 68.0 to 87.5 MHz. Any use for broadcasting would therefore have to be on the basis of no interference, no protection. Clearly, this will impose limits on the power that can be radiated and for this scenario we have therefore assumed that:

6 UK Spectrum Strategy, 2002, Chapter 2.

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5Broadcast transmissions are only permitted in the PMR base station transmit band (so avoiding interference from a high broadcast transmitter into a high base station receiver)7;

5Frequencies are only allocated for local broadcasting services.

We have further assumed that no agreement is reached with neighbouring countries and that UK licensees have to operate in a manner which avoids harmful interference to users of mobile radio on the continent.

An indication of the signal level that could be considered not to cause harmful interference can be obtained from CEPT Recommendation T/R 25-088. This specifies signal field strengths from land mobile radio systems that are not to be exceeded at country borders without coordination between the respective authorities. For the frequencies of interest here the limit is set at 6 dBµV/m (in a channel bandwidth of 12.5 kHz, equivalent to 18 dBµV/m in the 200 kHz bandwidth of an analogue sound broadcast channel).

An alternative approach is to limit the interfering signal level to 6dB below the receiver noise floor. At frequencies below 100 MHz the noise floor is dominated by man made noise and varies with the environment. In a “business” environment where noise levels are highest, this leads to a limit similar to T/R 25-08. In a rural environment, however, the limit would be 10dB lower. Both values are considered in the results that follow.

UK licensees would also have to accept any interference caused by legitimate transmissions from the continent. To assess the impact of such interference we have identified the interfering signal level that would just breach the level of protection required against tropospheric interference for the minimum usable signal for stereophonic broadcasts9.

Interference into the UK was determined by modelling multiple PMR base stations along the French coast configured to just meet the T/R 25-08 limit. PMR base station antennas were assumed to be mounted 20m above ground level.

Restrictions on transmit powers in the UK were determined for representative broadcast transmitters such that the interfering signal strength did not exceed the limit

7 This means that some other use would need to be found for the PMR mobile transmit frequencies that would be released under this scheme.

8 This recommendation covers planning criteria and coordination of frequencies in the land mobile service in the range 29.7 to 960 MHz.

9 This is 10 dBµV/m (in 200 kHz). Protection ratios were taken from ITU-R Recommendation BS. 412-9 and Geneva 84, Regional Agreement relating to the Use of the Band 87.5 - 108 MHz for FM Sound Broadcasting. Steady interference is also important but results in a less onerous protection requirement.

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identified above at the French coast. Broadcast antennas were taken to be mounted 75m above ground level10.

4.4 Results

4.4.1 Interference into the UK

Figure 4.1 shows the areas along the south coast of the UK where signal levels from mobile radio users in France could cause noticeable interference to FM radio listeners.

Figure 4.1: Areas in the UK where interference from the continent would result in a signal to interference ratio to below the minimum acceptable for FM radio broadcasts. Note, the limit is only exceeded at the edge of the broadcast service area (where the received signal is weakest).

The affected areas extend up to 50 km inland although 10 to 30 km is more typical, and cover a total area of 5,200 km2. Note, interference would only be noticeable at the edges of the broadcast coverage area where the wanted signal was weak. The effect would be to reduce the broadcaster’s service area in the affected regions.

There are currently 45 sound broadcasting stations within this zone.

10 Representative station parameters and locations were taken from the Radio Authority web site, www.radioauthority.org.uk.

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4.4.2 Restrictions on UK transmit powers

Figure 4.2 shows the area over which restrictions to broadcast transmitter powers would apply in order to comply with the signal level limit derived from T/R 25-08.

Figure 4.2: Geographic radiated power (ERP) restrictions required to meet T/R 25-08 signal strength limits at the border with France. (The limit is 18 dBµV/m in an analogue sound broadcast channel.)

Restricting radiated powers reduces the potential coverage area of transmitting stations. For local radio, however, ERPs of 1 Watt or less can provide adequate coverage suggesting that all except the south east corner of the UK (the red area in Figure 4.2) would be usable.

To obtain a more precise picture of the viability of local radio in this band, we note that a population coverage of about 50,000 is the minimum for a commercially viable local radio station11. Twenty seven local radio stations were modelled at current transmitter

11 Private communication. In addition, examination of the Radio Authority’s web site shows that around 50% of population centres with 50,000 to 90,000 heads, and 25% of centres with 25,000 to 50,000 heads, are served by local radio stations. The population covered will be larger as areas outside the population centre, including nearby population centres, may be served from one transmitter. Nevertheless, these figures are in accord with a minimum population coverage of 50,000.

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sites in the south of the UK between the Medway and Newbury, and their radiated powers controlled to just meet the cross border interference limits identified above. As shown in Figure 4.3 these sites lie in both the red and brown areas of Figure 4.2.

Figure 4.3: Local radio stations modelled in the south of the UK with radiated powers adjusted so as not to exceed the T/R 25-08 signal strength limits at the border with France.

Of the 27 sites considered 33% would provide coverage to in excess of 250,000 people, 70% would provide coverage to at least 100,000 people, and two provided coverage to less than 50,000 people. Both of the two were in Kent and within the red area of Figure 4.2.

We conclude that viable assignments could be made for local radio in all areas of main land UK with the exception of the relatively small area in the south east corner.

4.4.3 More stringent conditions

As noted in the previous section a more stringent interpretation of what constitutes harmful interference could result in signal level limits 10dB less than that derived from T/R 25-08. In this case, the ERP levels given in Figure 4.2 would all be reduced by 10dB, and deployment of local radio stations would be difficult in both the red and brown areas. This corresponds to an area of approximately 25,000 km2 (and a population of around 12 million).

4.4.4 Overcoming the restrictions

A practical solution in many situations where the restrictions on radiated power reduced the population coverage below a sustainable level would be to use a directional antenna. For example, simple Yagi antennas with beam widths of 130° to 150° can provide front to back ratios of 10 to 14 dB at these frequencies. This would be adequate to overcome the impact of the more stringent conditions discussed above,

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enabling deployment in all areas other than the far south east (the red area in Figure 4.2).

4.5 Conclusion

We conclude that local VHF radio stations could be established in the 78 to 88 MHz mobile band with adequate coverage areas in the whole of main land UK with the exception of the south east corner of the country, provided that the limits derived from T/R 25-08 are accepted as preventing harmful interference.

However, given that Broadcasting would be outside both the FAT and the ECAT, it is quite likely that the UK would have to limit its emissions by up to a further 10dB. In this case, the deployment of analogue FM local radio stations would be difficult for between 50 km and 100 km inland along to the south and south east coasts. Nevertheless this would leave a large proportion of the UK where broadcast stations could be established.

4.6 Tentative assertions

5Low power sound broadcasting for local radio is compatible with land mobile services;

5But, only the base station transmit frequencies can be used for broadcast purposes potentially leaving the base station receive frequencies unused.

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5. WIDE BAND PMR IN BAND III

5.1 Objective

This scenario examines the juxtaposition of wide band digital PMR systems in the UK with digital TV in France in the Band III TV band, and compares it with the current situation of analogue PMR in the UK and analogue TV in France. It therefore provides guidance on the change in coordination requirements that the move to digital technologies could make in this band.

5.2 Background

In Region 1 the band 174 to 223 MHz is allocated to the Broadcast Service and, through footnote S.5.23512, to the Land Mobile Service on a co-primary basis. The ECAT allocates the band 174 to 216 MHz to Broadcasting and Land Mobile on a co- primary basis.

When TV transmissions in Band III were closed down in the UK in the early 1980s it was decided that the band should be used for PMR including, at the time, two national trunked radio networks. However, the French continued to use the band for analogue TV transmissions and the two Administrations negotiated a coordination agreement which enabled PMR assignments to co-exist with the existing French TV stations. The UK now uses the bands 177 to 191 MHz, 193 to 207 MHz and 209 to 215 MHz largely for PMR applications although PMSE (for talk back and radio microphones) and SRDs also have assignments here.

Because greater coverage can be achieved at these frequencies than at the higher UHF frequencies designated for DVB-T it could be advantageous for the French to continue to use the band for TV but with a switch over to digital modulation. In the UK, there is currently some unassigned spectrum in the Land Mobile allocation and the band could therefore be an ideal location in which to make initial digital wide band PMR assignments.

This scenario therefore considers the situation in which France migrates its existing analogue TV stations to the DVB-T standard and the UK begins to make assignments to wide band (200 kHz) digital PMR systems. We assume that the existing coordination between the two countries is renegotiated to provide levels of protection to TV reception in France similar to that currently enjoyed by analogue viewers.

12 The footnote makes an additional allocation to the land mobile service in several countries including Belgium, France, Germany and the Netherlands but not the Republic of Ireland.

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5.3 The scenario

For the purposes of this scenario we assume that the migration to digital technology takes place at similar times in both France and the UK, and we therefore consider only the co-existence of digital with digital and analogue with analogue technologies. And, since the basis of the current agreement is to protect the TV viewers rather than PMR assignments, we consider only the restrictions that would apply to UK base station emissions and not the impact of any interference generated by French TV transmissions.

The coordination agreement between France and the UK identifies a number of test points in France and the median field strength of the TV signal that is to be protected at each. The levels specified vary but the lowest is 55 dBµV/m, and this is consistent with the value defined in ITU-R Recommendation BT.417. This value is therefore used in the analysis here.

As shown in Figure 5.1 the level of protection required varies across the 8 MHz bandwidth of the analogue TV signal with a maximum of 50 dB close to the vision carrier and a minimum of 24 dB.

ProtectionRatio

Protection Ratio dB 25 20 -2-1012345678 Frequency MHz from Vision Carrier

Figure 5.1: The variation in the level of protection required for the analogue TV signal as a function of the separation between the interfering PMR carrier and the TV vision carrier.

An additional degree of protection has to be included to allow for interference from multiple PMR base stations. The coordination process, agreed with France, takes account of all base stations within 300 km of a test point using the Simplified Multiplication Method to aggregate the signals13. For the purposes of modelling 20dB of additional protection has been used to account for the impact of multiple interferers.

13 Band IIII, A Guide to the Co-ordination Calculations (RA document: A Bhatt August 1988).

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For analogue TV the level of interference, generated by a single PMR base station, not to be exceeded at the test points14 therefore lies between -15 dBµV/m and +11 dBµV/m (in a bandwidth of 8 MHz).

In the case of digital TV the minimum median field strength and the required level of protection are taken from ITU-R Recommendation BT.1368 resulting in a maximum interfering signal level of 41.5 dBµV/m. Making the same allowance for the interference from multiple base stations, the interference level caused by a single PMR base station should not exceed 21.5 dBµV/m at the same test points.

The scenario was modelled by taking PMR base stations with antennas 20m above ground level, and determining the maximum ERP that could be radiated towards France without exceeding the interference levels identified above. The digital PMR system considered was the TETRA Advanced Packet System, with a channel bandwidth of 200 kHz. In the analogue case, conventional FM systems with a channel bandwidth of 12.5 kHz were modelled. The nominal ERPs for both narrow and wide band PMR transmissions were taken to be 25W.

5.4 Results

5.4.1 Analogue PMR and analogue TV

Figure 5.2 shows that, over approximately 103,000 km2 of the UK, the transmit power of an analogue PMR base station may need to be reduced. In the blue area the radiated power will need to be reduced if the PMR channel aligns with the TV vision carrier. The reduction will be less or may be zero when the channel lies elsewhere within the TV carrier bandwidth. In the red area (13,000km2) ERPs have to be reduced even for PMR assignments at the edge of the TV channel where the protection requirement is at a minimum. An assignment aligned with a vision carrier in this area would need to be reduced by at least 26 dB.

The total area potentially affected by coordination with French TV transmissions is large. Practice has shown, however, that by assigning carriers away from the vision carriers a useful proportion of the spectrum can be successfully used for PMR.

14 The test points are defined to be 10m above ground level.

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Reduced power for some assignments

Reduced power for all assignments

Figure 5.2: Geographic areas where the radiated power of analogue PMR transmissions may need to be reduced below the nominal value of 25 W ERP. In the red area ERPs have to be reduced regardless of where the PMR channel lies relative to the (analogue) TV vision carrier (but by more if close to the vision carrier). In the blue area a reduced ERP is necessary where the PMR channel aligns with the vision carrier, but may not be necessary for other separations between the two.

5.4.2 Wide band digital PMR and digital TV

The level of protection required for DVB-T transmissions is 10 to 25dB less than for analogue, and the areas over which ERPs would need to be reduced will be correspondingly smaller. However, the coverage area of a 25W ERP wide band digital PMR base station will also be less than for a narrow band analogue transmitter. To achieve similar coverage areas, an additional 11dB of radiated power would be required (resulting in a nominal ERP of 315W). In practice the transmit power available from the mobile will limit the coverage achievable.

Figure 5.3 shows the restrictions that would apply to wide band digital PMR transmissions in order to avoid interference to digital TV in France15. In the light blue and green areas, ERPs would need to be reduced below 25W. If higher powers were possible, these would be additionally constrained as shown in the two darker blue

15 Note, the same results hold for analogue PMR transmissions with digital TV in France.

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areas. But for either case, the areas affected (700 km2 and 8000 km2 respectively) are substantially smaller than in the case of analogue PMR and TV.

250W – 80W

80W – 25W

25W – 8W

8W – 2.5W

2.5W – 0.8W

Figure 5.3: The geographic restrictions on the radiated power of wide band digital PMR transmissions required to avoid interference to French digital TV reception.

5.5 Conclusion

This scenario illustrates that a move to digital TV in Band III in France would substantially reduce the constraints on the assignment of PMR frequencies in the same band in the UK. Although the area affected would be larger if the UK licensed higher ERPs to mitigate the reduced coverage area of wide band digital PMR (compared to narrow band analogue PMR) the affected areas remain substantially smaller than for the analogue case.

5.6 Tentative assertions

5Digital TV is less susceptible than analogue TV to interference from PMR systems.

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6. UNRESTRICTED WIDE BAND PMR AT 450 - 470 MHZ

6.1 Objective

This scenario examines the technical implications of assigning wide band digital PMR systems in the 450 to 470 MHz mobile band without regard to the harmonised approach defined in recent ECC Decisions.

For the Harmonisation Study this scenario compares the above situation with one in which the UK deploys narrow band digital PMR systems in the band, in accord with ECC Decisions.

6.2 Background

The band 450 to 470 MHz is allocated to Fixed and Mobile Services on a primary basis in the FAT but the ECAT primary allocation is to Mobile only. In the UK, the band is very largely used for mobile services although some scanning telemetry, Programme Making and Special Events, and Maritime (onboard) assignments are also accommodated here. The great majority of mobile assignments are to self provided PMR systems. However, the band also accommodates two public mobile data operators, paging and some military applications.

For historical reasons the use of duplex frequencies in this band is reversed relative to practice in much of Europe16. Over the years this has led to significant interference problems between UK systems and those operating on the European main land, especially during the period of extensive NMT 450 deployment in the late 1980s. Following the 1993 CEPT recommendation17 which designated a new band at 380 to 400 MHz for public safety services, the Home Office decided to relocate UHF police communications from the 450 to 470 MHz band to the new band (where the new Airwave network is located).

Once migration of police force communications is completed 2 x 3 MHz of spectrum will become vacant. This provides an opportunity to realign duplex use of the band with the CEPT plan, and Ofcom is planning to undertake this exercise over the next 5 years or so.

The majority of self provided PMR systems in use today use analogue technologies. There is, however, a growing interest in digital PMR systems both narrow and wide

16 The duplex bands were defined in 1968 in CEPT Recommendation T/R 25-08.

17 CEPT Recommendation T/R 02-02.

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band18. In response, the ECC has adopted channel plans for both narrow band and wide band19 (200 kHz) digital PMR/PAMR systems in a number of bands, including 450 to 470 MHz. In addition, ECC Report 25 proposes a common migration strategy to new technologies. For the 450 to 470 MHz band, this involves assigning narrow band systems from the lower end of the band and assigning wide band systems from the top end. However, the extent and pace at which wide band digital systems will be taken up is as yet unclear.

6.3 The scenario

This scenario considers the situation in which PMR users in the 450 to 470 MHz band in neighbouring countries migrate to digital PMR but predominantly to narrow band systems. Following band reversal in the UK, however, we assume that there is a significant take up of wide band systems and that the UK authorities respond by permitting assignments anywhere within the band in disregard of the ECC migration strategy. The following analysis therefore identifies the technical restrictions that would result from the deployment of wide band digital PMR systems in the UK in the same spectrum used for narrow band digital systems in continental Europe. For comparison purposes, we also evaluate the technical restrictions that would apply when narrow band systems are deployed both in the UK and in main land Europe.

In current practice there is little coordination of PMR assignments with neighbouring Administrations although assignments considered likely to cause interference to our neighbours are checked for general compliance with CEPT Recommendation T/R 25-08. Once the band reversal exercise is completed, coordination will be more effective and we have therefore assumed that digital assignments in the UK and in neighbouring countries will meet the current cross border interference limits specified in T/R 25-08. In the case of wide band digital systems, we have assumed that the same cross border limits, scaled for bandwidth, will be agreed.

The analysis was performed by deploying approximately 150 narrow band digital PMR base stations in Northern France. The density of base stations was commensurate with that in the south east of England20, and base station frequencies were assigned according to a frequency plan using 17 contiguous channels (and therefore covering 200 kHz, the bandwidth of wide band PMR). Transmitter powers21 were adjusted as

18 Narrow band encompasses 10, 12.5 and 25 kHz channel spacing, wide band includes 200 kHz and 1.25 MHz channel spacing (although the latter is some times referred to as broad band).

19 ECC/DEC/(02)03 and ECC/DEC/(03)01 respectively.

20 PMR base densities for Urban/suburban, rural, and wood and scrub land areas were determined from Agency data for 760 Band III assignments along the south coast and in East Anglia.

21 Nominal 25W ERP transmitters 10m above ground level were assumed. Mobile antenna heights of 1.5m were assumed. Channel bandwidth was 12.5 kHz.

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necessary to ensure that signals radiated into the UK did not exceed the T/R 25-08 limit of 20 dBµV/m at the UK coastline.

Narrow and wide band PMR base stations were then established on the Kent coast and configured so as to not exceed the permitted levels of interference into France. The resulting restrictions on UK deployments and the impact of interference from French base stations was then assessed.

Narrow band base stations in the UK were given the same RF characteristics as the French deployment. Wide band base station parameters22 were based on the TETRA Advanced Packet Service (TAPS) standard which has a channel spacing of 200 kHz. Interference from TAPS at the French coast line was taken to be limited to less than 32dBµV/m23.

6.4 Results

The effect of deployments in France and the UK on one another can be most easily seen in terms of:

5The area of the UK within which special measures would need to be taken to ensure that the signals radiated into France did not exceed the agreed limits;

5The area within the UK over which the effect of interfering signals from French base stations would be noticeable (note, the French systems are assumed to meet the same agreed interference limits).

Figure 6.1 shows the areas over which radiated powers towards France would need to be controlled. Both wide and narrow band base stations were assumed to have a nominal output of 25W ERP. These “coordination” areas24 amount to 4,500 km2 in the case of wide band systems and to 24,400 km2 in the case of narrow band systems.

Figure 6.2 shows the areas where interference from France into UK mobiles could be detectable. The areas involved are 1,200 km2 in the case of wide band systems and 7,800 km2 in the case of narrow band systems.

22 Nominal 8W transmitters with 5 dBd antennas were assumed.

23 Derived from the current limit in T/R 25-08 scaled for the wider bandwidth.

24 Areas within which transmit powers have to be maintained below the nominal level are referred to as “coordination” areas. Areas over which interference has a noticeable effect are referred to as “interference” areas, and “sterilised” (or “exclusion”) areas refer to areas within which transmitting stations cannot be operated.

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Narrow band PMR

Wide plus narrow band PMR

Figure 6.1: The “coordination” areas over which radiated powers have to be reduced below 25W ERP. The red area applies to wide band systems, red plus blue to narrow band systems.

Narrow band PMR

Wide plus narrow band PMR

Figure 6.2: Areas within the UK where interference from narrow band digital PMR systems in France would be noticeable by users of wide and narrow band PMR mobiles in the UK25.

25 Note, interference from multiple French base stations is aggregated here so this represents the situation where heavy use of the 450 to 470 MHz band is made in Northern France. The criteria for a noticeable effect is that interference raises the receiver noise floor by 1dB or more.

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6.4.1 Technical restrictions

To identify the technical restrictions that would apply to UK networks, a small number of PMR base stations were planned in eastern Kent close to the coast using existing UK site locations. Both narrow and wide band base stations were planned in this way, and coverage areas in the case of wide band systems are shown in Figure 6.3.

Figure 6.3: Coverage areas for four wide band digital PMR sites planned at existing PMR sites in Kent.

The results of this exercise show that:

5For the coordination areas shown in Figure 6.1:

ZThe coordination areas extend to approximately 200 km from the French coast for narrow band systems, and to approximately 100 km from the French coast for wide band systems;

ZOn the coast directional antennas are required to direct emissions away from the French coast;

ZBase stations right on the coast are strongly affected, with transmit powers restricted to a few watts for wide band systems and to less than one watt for narrow band systems.

ZCoverage areas are reduced to 100 km2 and less, although the reduction in area is much smaller for base stations 15 km or more inland (the geography helps here);

ZThe effects are larger for narrow band systems.

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5And, for the interference affected areas shown in Figure 6.2, signals from France reduce coverage areas by:

ZA few percent for wide band systems;

ZAround 20% for narrow band systems located within 15 km of the coast.

To put these figures into context we note that the average coverage area for nominal 25W ERP base stations is 860 km2 for wide band systems and 1800 km2 for narrow band systems26.

Clearly, wide band (200 kHz) digital systems will be less affected by narrow band deployments on the continent than narrow band systems. Thus, disregarding the migration strategy propounded in ECC Report 25 and making wide band assignments anywhere within the 450 to 470 MHz band, will not lead to any additional technical constraints on UK deployments27.

We note, however, that agreement on the use of preferred frequencies would be possible with coordinated narrow band deployments but not with uncoordinated wide band deployment. The use of preferred frequencies would halve the capacity available within the coordination zone but reduce the costs of deployment (since coverage areas are maximised). The use of preferred frequencies is therefore of benefit where coverage rather than capacity is the main requirement.

6.5 Tentative assertions

5Replacing narrow band with wide band systems for similar services using similar technology and transmit powers, results in relaxed technical constraints;

5But uncoordinated mixing narrow and wide band systems will prevent the use of preferred frequencies (which reduce deployment costs at the expense of capacity).

26 These areas were determined from a sample of 760 actual assignments in Band III in East Anglia and along the south coast with ERPs of 25W.

27 It should be remembered that this study is concerned only with the impact of cross border interference and coordination. The impact of co-locating narrow and wide band systems in adjacent spectrum is not considered here, but will require guard bands, see ECC Report 22. Hence ‘random’ packing of wide band and narrowband systems within the UK would likely reduce the usable spectrum.

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7. UTRA TDD IN SPARE DVB-T CHANNELS

7.1 Objective

The objective of this scenario is to determine the feasibility of deploying UTRA TDD network technology within a DVB-T multiplex in the UHF band and to examine the restrictions likely to apply to the deployment of any such network if the TDD system is to operate within the accepted interference levels of the European DVB-T coordination plan.

For the Harmonisation Study this scenario will identify any geographic areas where UTRA TDD cannot be deployed and/or the increased number of base stations, compared with no interference constraints, that would need to be deployed to provide the same level of coverage.

7.2 Background

In the UK, land mobile is a secondary allocation in the frequency band 470 to 590 MHz (i.e. Band IV, TV channels 21 to 35). Mobile is co-primary or secondary with Broadcasting in the ECAT across the whole band but only for applications ancillary to broadcasting up to 790 MHz. However, a footnote (S5.136) was added at WRC 03 which made Mobile a co-primary allocation between 790 MHz and 862 MHz in some countries. These include the UK, France and the Netherlands but not Belgium or the Republic of Ireland.

Digital terrestrial TV (DVB-T) broadcasting will replace traditional analogue broadcasting throughout Europe over the coming decade, and ITU-R Regional Radio Conferences (RRCs) in 2004 and 2005 will finalise re-planning of the UHF broadcast spectrum. The use of the DVB-T standard will provide additional capacity and it is possible that some TV channels allotted to the UK could be available for other applications.

The Chester Agreement28 of 1997 already identifies some of the technical criteria and coordination procedures required to migrate the use of the broadcast spectrum. Under this agreement, consistent with Stockholm-61, the interference arising from all broadcasting stations is aggregated and a channel is only identified for use if the total interference at test points does not exceed an interference threshold. In this way additional channels can incrementally be added into the broadcasting frequency plan.

28 The Chester 1997 multilateral coordination agreement relating to technical criteria, coordination principles and procedures for the introduction of terrestrial digital video broadcasting.

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The Chester Agreement accounts for services other than broadcasting to be used within this frequency band:

“For stations of services other than broadcasting, the provisions of the Radio Regulations shall apply, taking into account the categories of service and allocations specified in Article S5 thereof. Contracting Administrations proposing to change the technical characteristics of such stations or to establish new stations of such services shall take into account the broadcasting stations appearing in the Plan or brought into use in accordance with this Agreement and shall do so after reaching mutual agreement with the administrations that may be concerned.”

For this scenario we will assume that the UK uses a channel, consistent with the DVB-T coordination principles, for a mobile application. However, it should be noted that any such use could be secondary to subsequent use for a new broadcast station by a UK neighbour. This is permitted under the Chester agreement which allows for additional transmitters to use a given frequency if the cumulative noise rise at a series of test points remains below an agreed limit.

Counter-intuitively this may mean that it is preferable to use a channel (for the non- broadcast application) that is close to the limit. It would then be less likely that the channel would be used for an additional TV transmitter in a neighbouring country and claim precedence over the non-broadcast application.

7.3 The scenario

Any (mobile) application that uses this spectrum will need to fit within the 8MHz DVB-T channel plan and technologies requiring duplex channels are unlikely to be suitable. This scenario therefore considers the re-use of DVB-T channels for UTRA TDD networks. Future demand for this technology could arise to provide high downlink capacity in urban areas or to provide additional wide area coverage, for example, to facilitate improvement of rural communications.

It is assumed that, at the forthcoming RRCs, it is agreed that some DVB-T channels may be used for mobile applications provided the levels of interference set in the DVB-T coordination plan are not exceeded. This plan is not yet finalised. However, some digital transmitters are already operational and we have used these to estimate the levels of interference that will be permitted under the new plan. In addition, some channels may be available on a national basis within the UK, and others on a regional basis. For this reason our approach here is to evaluate the use of UTRA TDD within the service area of a single DVB-T transmitter, and to extrapolate the results to the case of a nationally available frequency.

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The high power DVB-T transmitter at Sutton Coldfield (20KW, with a 233m omni- directional antenna29) was used to establish the DVB-TV coverage area and the highest levels of interference along the France/Belgium/Netherlands coast at the 10m coordination height. It is assumed that any UTRA network would need to take measures to ensure that the cumulative interference radiated into neighbouring countries from the UTRA TDD system did not exceed the levels that would be produced by a DVB-T transmitter.

For comparison purposes, this scenario also assesses the impact of operating UTRA TDD in both the south of England and in Northern France assuming harmonised use in both countries. In this case it is assumed that the relevant Administrations agree that cross border coordination is to be based on ERC Recommendation ERC/REC/(01)01 scaled for operation at 500MHz. This equates to a maximum field strength of 24 dBµV/m, from any given transmitter30, at a height of 3m above ground level beyond the border for preferential codes and frequencies. It is assumed that a UTRA macro cell base station at 500MHz will use antennas 20m above ground level, and have a transmitter power output of up to 25W (power increased to accommodate lower antenna gain) and an antenna gain of 8dBd, giving an ERP of 160W (22 dBW).

7.4 Results

7.4.1 UTRA TDD in DVB-T channels

The signal level from the Sutton Coldfield DVB-T transmitter is shown in Figure 7.1. The highest level of interference due to this transmitter in France, Belgium or Holland was found to be 34 dBµV/m at 10m above ground level. This level was selected as the highest permissible level of cumulative interference31 received from UK-based UTRA TDD systems in Europe at 10m above ground level for 50% time and 50% locations.

We understand that 16QAM will be used in the UK which, for a coding rate of ½ and a coverage probability of 95%, requires a minimum median signal level of 43 dBµV/m32. On this basis the service area of the Sutton Coldfield transmitter is some 70,000 km2 (the green areas in Figure 7.1).

29 DVB-T transmitter parameters were taken from the CEPT DVB-T database.

30 Hence, in this case, there is no need to aggregate the interference from multiple transmitters using a method such as the Simple Multiplication Method.

31 This is a worst case (i.e. low) estimate since interference from other co-channel transmitters has not been included here.

32 The Chester 1997 multilateral coordination agreement relating to technical criteria, coordination principles and procedures for the introduction of terrestrial digital video broadcasting.

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Figure 7.1: Signal level and interference in neighbouring countries from a high-powered DVB-T transmitter.

To determine where UTRA TDD networks could be operated, representative TDD base station characteristics were used to determine the area where constraints would be required to prevent interference exceeding the DVB-T interference limits established above. This coordination zone was found to have an area of approximately 3,500 km2 which corresponds to seven UTRA TDD base stations (a typical coverage area at 500 MHz is ~510 km2). Since it is the aggregate interference level that must not be exceeded, the interference gain from 7 UTRA base stations was determined using the SMM method (giving an aggregation gain of approximately 15dB). Using this ‘interference aggregation gain’ the maximum UTRA transmitter power level possible without exceeding the DVB-T interference threshold was determined. The result is shown in Figure 7.2.

A comparison of Figure 7.1 and Figure 7.2 shows that the coordination zone overlaps to some extent with the DVB-T service area. Thus UTRA TDD base stations of up to 160W ERP could be operated anywhere within the service area of a DVB-T transmitter apart from within the overlap area. In this case, the overlap area amounts to approximately 10,000 km2. Within this area UTRA TDD base station ERPs would have to be reduced in order not to exceed the DVB-T interference threshold but the necessary reductions would be less than 6dB over 70% of the area.

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ERP 22 dBW 19 dBW 16 dBW 13 dBW 10 dBW 7 dBW 4 dBW 1 dBW -2 dBW -5 dBW -8 dBW

Figure 7.2: Areas in which UTRA TDD base station ERPs have to be constrained below 160W to avoid exceeding the acceptable DVB-T interference level in neighbouring countries.

To determine the size of the area over which UTRA TDD transmit powers would need to be reduced when operated within a nationally available DVB-T channel we note that, for good reception, the TV signal at the Kent coast would be 20dB higher than that from the Sutton Coldfield transmitter (see Figure 7.1). UTRA TDD transmit powers could therefore also be 20dB higher and, in this case, the coordination area reduces to just 1,800 km2 in the south east corner of the UK (the red and brown areas of Figure 7.2). Thus UTRA TDD base stations could be operated in a national DVB-T channel at their full nominal power of 160W ERP over all except this small area of the south east coast.

7.4.2 UTRA TDD co-ordinated with UTRA TDD

It is considered unlikely that there will be a European-wide allocation of DVB-T channels to mobile applications. Nevertheless, for the purposes of comparison in the companion Harmonisation Study, we examine the restrictions that would apply to UTRA TDD deployed at 500 MHz when the UK’s neighbours also use the same part of the UHF TV spectrum for UTRA TDD, assuming adjacent countries co-ordinate their use.

Using the nominal base station configuration, the maximum transmit power that can be used without exceeding the field strength limit of 24 dBµV/m33 at the French coastline is shown in Figure 7.3.

33 This is the limit specified in ERC Recommendation ERC/REC/(01)01) scaled to the lower frequency.

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ERP 22 dBW 19 dBW 16 dBW 13 dBW 10 dBW 7 dBW 4 dBW 1 dBW -2 dBW -5 dBW -8 dBW

Figure 7.3: Areas in which UTRA TDD base station ERPs have to be constrained below 160W to avoid exceeding the interference level specified by ERC Recommendation ERC/REC/(01)01 scaled for operation at 500 MHz.

The area where transmit powers have to be constrained to an ERP of less than 160W is approximately 16,000km2. Within this area a TDD network operator would need to take interference reduction measures to prevent unacceptable interference in neighbouring countries. These measures would include transmit power reduction, antenna down-tilting and placing base stations on the border and transmitting away from neighbour countries.

7.5 Tentative assertions

5Introducing a low power system into spectrum planned for high power wide area use can work well.

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8. FIXED WIRELESS ACCESS IN THE 900 MHZ TETRA BAND

8.1 Objective

The objective of this scenario is to determine the feasibility of deploying fixed wireless access in the rural parts of Northern Ireland using the 900 MHz TETRA band.

8.2 Background

The frequency band 870 to 876 MHz paired with 915 to 921 MHz was identified for harmonised use for TETRA systems in 1996. In early 2003 a further ECC Decision identified the band as one of three possible bands from which demand for wide band digital PMR systems should be met but did not specify the technology to be used. In 2000 the Agency allocated 2 x 1 MHz34 for private TETRA use and, in 2002, assigned 2 x 4 MHz35 to Inquam for wide band TETRA. However, no TETRA equipment is currently available for this band.

The band is allocated to Mobile, Fixed and Broadcasting Services on a co-primary basis within the FAT and solely to the Mobile Service in the ECAT. Of our nearest neighbours, the Republic of Ireland and the Netherlands have allocated the band to Land mobile while France and Belgium are believed to retain tactical military radio links in this spectrum.

8.3 The scenario

Given the lack of activity in TETRA at 900 MHz to date, we consider the situation in which the UK decides to allocate the 900 MHz TETRA band to fixed wireless access as a way of enabling higher speed access in rural areas. This allocation would be contrary to European harmonisation Decisions and to the ECAT but is in accord with the FAT. The Irish are assumed to deploy narrow band TETRA systems or at least to wish to protect their spectrum for future deployments.

This scenario therefore examines the extent to which a fixed wireless access system could be deployed in Northern Ireland while affording appropriate levels of protection to TETRA systems deployed in the Republic of Ireland. Two situations are considered:

5Firstly we assume that ComReg insists that the band is protected over all of its territory. An MOU is assumed to be negotiated which specifies the maximum field

34 871 – 872 MHz paired with 916 – 917 MHz.

35 872 – 876 MHz paired with 917 – 921 MHz.

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strength that the FWA system may generate at the border. The field strength is derived from the existing cross border agreement applicable in the frequency band 380 to 385 MHz paired with 390 to 395 MHz36 and scaled to reflect the different frequency and bandwidth. The resulting limit is 44dBV/m for 50% of locations and 10% of the time.

5Secondly we consider the situation in which the Irish adopt a more flexible approach and permit higher signal levels to radiate across the border provided the above limit is not exceeded in areas where the TETRA systems are actually deployed. These are assumed to be the towns close to the border. We note that it is considered unlikely that such an agreement would be acceptable to the Irish authorities.

The most problematic interference is likely to be transmissions from customer premise equipment (CPEs) into TETRA base station receivers. However, we assume that the FWA operators accept the constraint that CPE’s near the border have to be pointed away from the Republic even if this means that the subscriber is linked to a second choice base station. The FWA base stations in Northern Ireland are taken to radiate a maximum ERP of 10W from an antenna 20m above ground level.

8.4 Results

Figure 8.1 (on the following page) shows the areas in which the power radiated towards the border has to be restricted to prevent breach of the field strength limits at the border.

In the red areas ERPs have to be limited to between 1W and 10W (dependent on the exact location), to between 0.1W and 1W in the blue areas and to less than 0.1W in the green areas. The restrictions extend up to 60 km into Northern Ireland and would therefore cover the majority of the province.

Power reduction, transmitter down tilt and directional antennas could all be used to limit cross border interference levels. However, each 10dB of reduction in radiated power reduces the coverage area by up to 50%. Down tilt provides more limited attenuation and again reduces the coverage area. The use of directional antennas can be effective but roughly twice as many base stations can be required to achieve the same coverage. And in areas close to the border even this may not provide a solution as CPEs would then radiate towards the border.

36 Memorandum of Understanding Between the Administrations of Belgium, France, Germany, Ireland, Luxemburg, Netherlands, Switzerland and United Kingdom Concerning Coordination of Frequencies in the Frequency Band 380 – 385 MHz and 390 – 395MHz.

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1W – 10W

0.1W – 1W

0.01W – 0.1W

Figure 8.1: Estimated ERP limits for FWA base stations operating in Northern Ireland.

In practice a mixture of all three techniques would be used. Nevertheless, given that the restrictions would apply across much of Northern Ireland the overall impact would be significant, possibly increasing the base stations requirement by 50%. And even then it is likely that some deployments would not be possible in the border area.

8.4.1 Protecting actual installations

The restrictions discussed above are the result of protecting the whole of the Republic of Ireland from interfering signals whereas in the more rural parts of the country there may be no wireless installations requiring protection. Figure 8.2 shows how the situation would change if the FWA operators in Northern Ireland had only to protect the areas where the TETRA network was deployed. (For this purpose representative TETRA deployments were modelled in the towns along the Irish side of the border. The operational areas assumed are illustrated in Figure 8.3 on the next page.)

In this case the restrictions are far less onerous and typically extend less than 10 km back from the border. Special engineering of base stations and CPEs would still be needed in the areas highlighted and deployment could still be problematical close to the border. Nevertheless, it is clear that the overall impact on network deployment would be much reduced.

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1W – 10W

0.1W – 1W

0.01W – 0.1W

Figure 8.2: Estimated ERP limits for FWA base stations when only the operational areas of the Irish TETRA network are to be protected from interference.

8.5 Conclusion

Deployment of a fixed wireless access system in Northern Ireland in the 900 MHz TETRA band would entail special engineering across the majority of the network in order not to export more interference across the border than the UK and Irish Administrations would likely agree. The special engineering techniques needed would be:

5Reduced transmit power levels and consequential reductions in coverage areas;

5Antenna down tilt;

5The extensive use of base stations covering only sectors pointing away from the border;

5Careful planning of CPEs to avoid radiation towards the border.

The resulting increase in the number of base stations and associated costs would seriously jeopardise the commercial viability of any such deployment.

However, the situation would be very much improved if the UK and Irish Administrations were to agree that only existing installations within the Republic of Ireland were to be protected.

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Figure 8.3: The assumed service areas for the TETRA networks deployed in the Republic of Ireland.

8.6 Tentative assertions

5Measures such as directional antennas can mitigate the effect of cross border emissions but come at a cost;

5Providing protection to installed systems (to stations or to operational areas) can reduce the constraints noticeably.

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9. REFARMING OF GSM SPECTRUM TO UTRA

9.1 Objective

The objective of this scenario is to identify the impact of the UK choosing to re-farm GSM spectrum (at both 900MHz and 1800MHz) for FDD UTRA applications ahead of re-farming in neighbour countries.

For the Harmonisation Study, this scenario also provides a quantitative comparison with the situation in which the UK and its neighbours refarm on similar time scales.

9.2 Background

GSM networks at both 900 MHz and 1800 MHz are widely used across Europe, and operate in spectrum harmonised for mobile phone services. At 900 MHz the band 880 to 915 MHz paired with 925 to 960 MHz is generally used although the 1987 EC Directive which mandated the band for digital cellular usage strictly applies only to 905 to 914 MHz paired with 950 to 959 MHz. ERC Decision 94(01) later extended the band to 890 to 915 MHz paired with 930 to 960 MHz.

The 1800 MHz band37 was designated for use with the GSM 1800 mobile standard by the ERC Decision (95)03. The Mobile Directive in 1996 identified the band for mobile use but did not mandate the use of GSM technology. Thus the 1800 MHz band could be refarmed to the UTRA 3G mobile standard without conflicting with EC Directives whereas to do so at 900 MHz would require abrogation of a Directive.

Third generation technology, such as UTRA, is capable of supporting a richer set of services and can provide capacity more cost effectively than GSM. Since UTRA has been designed to allow migration of the existing 2G infrastructure to a 3G capability, some operators could be motivated to migrate their 2G networks to UTRA, where there is sufficient demand for 3G services.

The south of England is a high traffic area for today’s mobile services and is likely to be a priority area for any re-farming. In contrast Northern France is more rural and it is possible that French operators would chose to migrate use of 2G spectrum in the border region with the UK at a slower pace than UK operators. Hence, this scenario will consider a mature 2G network in France coexisting with a mature 3G network in the UK. Note, because of the unequal split of 900 MHz and 1800 MHz spectrum between the GSM operators in the UK, it is likely that refarming of both bands would occur at around the same time.

37 1710 to 1785 MHz paired with 1805 to 1880 MHz.

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In the UK the 900 MHz and 1800 MHz bands identified above are licensed to the four GSM operators. In France, parts of both bands have continued to be used by the military. However, this use is thought to be ceasing and, for the purposes of this scenario, we assume that the French bands will be used exclusively for public mobile services by the time that refarming begins.

9.3 The scenario

Any move by the UK to refarm current GSM spectrum to UTRA ahead of its neighbours would be in conformity with both the FAT and the ECAT but, we assume, would be out of line with relevant European Directives and Decisions. We therefore assume that our neighbours would be prepared to negotiate cross border coordination agreements. Given that their existing GSM networks will already conform to the existing coordination agreements38 we further assume that the new agreements would continue to provide essentially the same protection as these networks enjoy under the current regime.

On this basis, France and the UK agree that UTRA signals radiated into France from the UK will not exceed the field strength already agreed for non-preferential39 GSM frequencies (suitably scaled for the difference in channel bandwidths) this being lower than the level defined in the ERC Recommendation (01)01 on border coordination for UMTS/IMT-2000 systems (suitably scaled for frequency). Similarly, the agreement is assumed to state that the existing French GSM networks will continue to conform to the existing agreements and, that once UTRA networks are deployed on both sides of the border, both countries will conform to ERC Recommendation (01)01, suitably scaled for frequency.

This scenario was modelled at 900 MHz using the system parameters described below.

9.3.1 UTRA coordinated with UTRA

UTRA base stations are assumed to have transmit powers of 20W, with antennas sited 20m above ground level and having gains of 12dBi at 900MHz (i.e. the EIRP is approximately 316 W).

The maximum interference allowed to be transmitted across borders is defined by ERC Recommendation ERC/REC/(01)01 scaled for operation at 900MHz. The dominant

38 France and the UK have agreed MOUs on the coordination of frequencies in the GSM bands at both 900 MHz and 1800 MHz.

39 The existing GSM MoUs are based upon small segments of spectrum identified for preferred and non- preferred use. Since no segment is large enough to accommodate the wide band UTRA signal, it would be reasonable that UTRA interference into French GSM networks should not exceed the limit for non- preferred GSM frequencies.

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interference allowed will be the limit consistent with preferred codes. This is 45 dBµV/m in 5MHz, 3m above ground level for 50% locations and 10% of time. This scales to 38 dBµV/m in 5MHz at 900MHz.

On the down link, it is assumed that the effective noise floor of a mobile terminal is –96 dBm40 (or 40 dBµV/m in 5 MHz). The minimum signal power required41 to support a 12.2Kbit/s voice service is –116 dBm (or 20 dBµV/m in 5MHz at 900MHz into a 0dBi antenna).

9.3.2 UTRA coordinated with GSM

The UTRA parameters identified above are re-used in this case. The GSM base stations consist of 2 transceivers with each channel having a maximum power of 8W, with antenna sited 20m above ground level and having gains of 12dBi at 900MHz.

It is assumed that the French GSM operators will have preferred frequencies directed towards the UK and that up to 12 of these carriers can be present in the 5 MHz UTRA carrier bandwidth. The current GSM MOU between the UK and France limits the signal strength at the border for preferred frequencies to 26 dBµV/m at 3m above the ground for 50% of time and 50% locations. This is therefore the level of interference that could be received by a UK UTRA handset from a single GSM base station.

The same MOU limits the field strength for non-preferred frequencies to 11 dBµV/m under the same conditions as noted above. This scales to 25 dBµV/m in 5 MHz and is the maximum field strength that a UK UTRA base station is permitted to cause in France.

9.4 Results

The implications of cross border coordination and interference for UK deployments are exemplified by:

5The extent to which signals radiated by UTRA base stations in the UK have to be controlled in order to comply with the agreed cross border limits, and;

5The areas within the UK over which interference from French networks will have a noticeable effect. Interference from French base stations into UK mobile terminals is likely to be more severe than from French mobile terminals into UK base stations, and the former has therefore been modelled.

40 For a noise figure of 8dB, and an intra-system interference margin of 4dB at the cell edge.

41 Including allowance for factors such as penetration loss, 95% coverage probability and processing gain.

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9.4.1 UTRA coordinated with GSM at 900 MHz

Figure 9.1 shows the areas in the south east of the UK within which UTRA signals radiated towards France would need to be restricted in order to comply with the cross border field strength limit of 25 dBµV/m. These results show that EIRPs would have to be reduced by up to 15 dB, from a nominal 316W, over an area of approximately 4,500 km2.

Figure 9.1: The geographic restrictions on EIRPs radiated towards France required to meet the cross border limit for non-preferred GSM frequencies at 900 MHz.

The level of interference in the UK from GSM networks in France was determined for 68 base stations located around the coast of Northern France, each of which was assumed to transmit on two carriers and to meet the existing MOU limit of 26 dBµV/m for preferred frequencies. Interference was aggregated and taken to have a noticeable effect on UTRA mobiles when it raised their noise floor by more than 1 dB, that is when it exceeded 34 dBµV/m. The area over which the total interference exceeded this level covers some 950 km2 as illustrated in Figure 9.2.

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34 – 36 dBµV/m 37 – 39 dBµV/m 40 – 42 dBµV/m 43 – 45 dBµV/m 46 – 48 dBµV/m

Figure 9.2: Areas within the UK over which interference from GSM networks in Northern France would have a noticeable effect on a UK UTRA network42.

9.4.2 UTRA coordinated with UTRA at 900 MHz

Once France has refarmed its 900 MHz GSM spectrum to UTRA, ERC Recommendation (01)01 comes into force and the limit on signals radiated across the border rises from 25 to 38 dBµV/m. As a result the area over which restrictions would apply to UTRA base station transmit powers is reduced, as illustrated in Figure 9.3.

Figure 9.3: The geographic restrictions on EIRPs radiated towards France required to meet the cross border limit of 38 dBµV/m for UTRA base stations using preferred codes in the base station transmit band.

42 The cumulative effect of interference from multiple base stations was taken into account using the Simplified Multiplication Method.

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The area affected, 1,800 km2, is less than half that in the case of GSM networks in France.

The area over which interference would be noticeable in the UK was calculated in the same way as before for a network of UTRA base stations in Northern France, with the French base stations constrained by the same cross border signal level limit of 38 dBµV/m. The area of interference is now increased, relative to the situation with GSM, to around 7,200 km2 as shown in Figure 9.4

34 – 36 dBµV/m 37 – 39 dBµV/m

40 – 42 dBµV/m

43 – 45 dBµV/m

46 – 48 dBµV/m

Figure 9.4: Areas within the UK over which interference from UTRA networks in Northern France would have a noticeable effect on a UK UTRA network.

The above analysis shows that, compared to the situation with adjacent cross border UTRA networks, coordinating UTRA networks with cross border GSM networks results in greater restrictions on the UTRA base station transmit powers but smaller areas of interference to the UTRA network. Table 9.1 summarises these results.

Area over which UTRA base Area over which UTRA station EIRPs are restricted networks suffer interference

UTRA to GSM 4,500 km2 950 km2

UTRA to UTRA 1,800 km2 7,200 km2

Table 9.1: Summary of the impact of cross border coordination arrangements.

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9.4.3 Refarming at 1800 MHz

Our assumption in this scenario is that the cross border agreement at 1800 MHz would be based on the same principles as at 900 MHz. Thus differences arise from the different conditions in the existing agreements at 1800 MHz43. Table 9.2 summarises the resulting field strength limits for UTRA / GSM coordination and compares them with the levels derived earlier for 900 MHz.

Field strength limits at the border or Area affected at coast line of the adjacent country 900 MHz

900 MHz 1800 MHz

Radiation from UTRA 25 dBµV/m 39 dBµV/m Transmit power base stations in GSM (in 5 MHz) (in 5 MHz) restriction over networks 4,500 km2

Radiation from GSM 26 dBµV/m 29 dBµV/m44 Interference over base stations in (in 200 kHz) (in 200 kHz) 950 km2 UTRA networks

Radiation from UTRA 38 dBµV/m 44 dBµV/m Transmit power base stations into (in 5 MHz) (in 5 MHz) reduction over UTRA networks 1,800 km2

Radiation from UTRA 38 dBµV/m 44 dBµV/m Interference over base stations into (in 5 MHz) (in 5 MHz) 7,200 km2 UTRA networks

Table 9.2: Comparison of field strength limits applied at 900 MHz and 1800 MHz.

Comparing the limits at 900 and 1800 MHz and noting the areas affected at 900 MHz we can draw the following inferences on the impact of cross border coordination at 1800 MHz. Taking the cases in the same order as in Table 9.2:

5The limit on cross border emissions from UTRA base stations into a GSM network is 14 dB higher than at 900 MHz. Combined with the greater signal attenuation at 1800 MHz this means that restrictions on base station EIRPs can be eased by around 20dB. Examination of Figure 9.1 shows that the area over which transmitter powers would need to be controlled will be reduced to ~300 km2 (the red area) for the same nominal EIRP.

43 In addition to different values for the trigger levels, the trigger level for preferred frequencies is defined at 15 km inside the border rather than at the border or coast line.

44 The value given in T/R 22-07 is increased by 4dB to scale the limit back to the border.

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5The permitted level of radiation from GSM into a UTRA network is 3 dB higher at 1800 MHz. However, this is more than offset by the 6dB increase in the mobile receiver noise floor to give a 3dB reduction in the effective level of interference. Inspection of Figure 9.2 indicates that the area affected will be reduced to approximately 250 km2 (interference no longer occurs in the dark blue area)45.

5The limit on emissions from UTRA base stations into a cross border UTRA network is 6 dB higher than at 900 MHz. With the additional signal attenuation experienced at 1800 MHz this indicates a relaxation in EIRP restrictions by 10 to 15dB. Inspection of Figure 9.3 suggests that the area over which transmitter powers would need to be controlled will be substantially reduced to the red and part of the green area (an area of ~350 km2);

5In the case of interference from French UTRA base stations into a UK UTRA network, the limit on cross border radiation is again 6dB higher but the mobile receiver noise floor is also increased by 6dB. As a result, the area over which interference from a French UTRA network would be noticeable, will be essentially unchanged at 7,200 km2.

These conclusions are summarised and compared with the 900 MHz results in Table 9.3.

Area over which UTRA Area over which UTRA base station EIRPs are networks suffer restricted interference

900 MHz 1800 MHz 900 MHz 1800 MHz

UTRA to GSM 4,500 km2 ~300 km2 950 km2 ~250 km2

UTRA to UTRA 1,800 km2 ~350 km2 7,200 km2 ~7,200 km2

Table 9.3: Comparison of the size of the areas affected by cross border coordination at 900 MHz and 1800 MHz.

9.4.4 Minimising the impact of the restrictions

The use of directional antenna, common practice for mobile networks, will reduce both the reduction in transmitter power required and the level of interference received in sectors pointing away from the France.

45 The increased signal attenuation at 1800 MHz is ignored here on the basis that it occurs relatively close to the base station, as may be seen by comparison of CEPT Recommendations T/R 20-08 and T/R 22-07, so that 900 MHz and 1800 MHz interfering signals may be assumed to decay at similar rates beyond the border.

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9.5 Conclusions

Should the UK decide to refarm the existing GSM bands to UTRA ahead of France there would need to be restrictions on the powers radiated towards France at 900 MHz to keep interference levels within reasonable bounds. The restrictions at 1800 MHz would be minimal. The impact of interference on UK networks would be small.

When France subsequently deploys UTRA these restrictions would ease significantly. The areas over which interference would be noticeable in the UK would, however, increase at both 900 MHz and 1800 MHz.

9.6 Tentative assertions

5Changing the technology but maintaining the same application leads to relatively small changes in cross border constraints.

5Different MOUs for similar applications can be significantly different (this was determined from the quantitative analysis of this scenario).

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10. TERRESTRIAL DAB LOCAL RADIO AT 1800 MHZ

10.1 Objective

This scenario considers the practicality of deploying local digital radio broadcasting stations on a no interference, no protection basis in a band used for GSM cellular services.

10.2 Background

The “1800 MHz” band46 is widely used for GSM across Europe. Its application to GSM technology is defined in the ERC Recommendation ERC/REC/(95)03 and the Mobile Directive 96/2/EC states that Members cannot refuse to allocate mobile licences once they have signed ERC/DEC/(95)03. However, the band is not mandated for use for GSM systems by an EC Directive in the way that the 900 MHz band is.

In the UK it is almost entirely assigned to, and used by, the four GSM operators. In France part of the band was assigned to the GSM operators and part continued to be used for tactical links by the military. It is understood that the military spectrum has now been vacated and will be assigned to the mobile operators. In Belgium, the Republic of Ireland and the Netherlands the band is assigned to the GSM operators.

Within the FAT and within the ECAT the band is allocated on a primary basis to the Fixed and Mobile Services.

10.3 The scenario

In this scenario we imagine the situation in which it turns out that the spectrum allocated to IMT-2000 is greater than needed, and one (or more) of the GSM operators sells spectrum in the 1800 MHz band to a broadcaster planning a new network of local radio stations.

Because this band is not allocated to Broadcasting in the FAT, the new radio service has to operate on a no interference, no protection basis. However, the UK and French authorities negotiate an agreement which permits the broadcasters to radiate the same spectral power density into France as permitted from base stations for non-preferential frequencies under the relevant ERC Recommendation47 for GSM 1800 (this is 25dBµV/m for GSM transmissions, equivalent to 35dBµV/m for T-DAB transmissions).

46 1710 to 1785 MHz (base station receive) and 1805 to 1880 MHz (base station transmit)

47 CEPT Recommendation T/R 22-07 (note, this is about 7dB more stringent than the UK/France MOU on GSM 1800 coordination).

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However, the agreement is only applied to transmissions in the upper duplex (base station transmit) band in which the French GSM mobiles will suffer interference. Transmissions at this level are not permitted in the lower duplex band as the GSM 1800 base station receivers will be on relatively high masts and the potential for interference is considered too high48.

This scenario was first modelled by identifying the locations in Northern France that would suffer the greatest levels of interference from T-DAB stations in the south east corner of the UK. The maximum T-DAB transmit powers that would meet the assumed MOU were then determined for different areas of the UK.

The broadcast antennas were taken to be mounted at 50m above ground level, and the field strengths were calculated at 3m above ground level in line with the current MOU.

10.4 Results

The geographic restrictions on T-DAB transmitter powers are shown in Figure 10.1.

Figure 10.1. The maximum permissible ERPs for T-DAB transmitters to meet the assumed MOU field strength limit in France.

48 This, of course, means that other uses would have to be found for the spectrum released by the GSM operators in the lower duplex band. Note also that no consideration has been given to compatibility with other mobile operators in the band.

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It is estimated that a transmitter power of 1 to 10kW is likely to be adequate for most situations in the UK. On this basis, T-DAB local radio would be viable in the dark blue areas, generally viable the light blue area, but probably not viable in the green areas. The brown and red areas in the south eastern corner of the UK would not be usable. The sterilised area (green, brown and red areas) covers 26,000 km2 and a population of about 12 million.

Clearly, there is a significant area of the UK where it would not be possible to use these frequencies49. Nevertheless, these results indicate that the upper half of the 1800 MHz band could be used for local digital radio over a good proportion of the country.

10.4.1 Operation on a no interference basis

If the presumed agreement could not be reached with the French authorities, UK broadcasting in this band would have to operate on a no interference, no protection basis. To identify the implications of this we note that it is generally accepted that the effect of interference is just noticeable if it raises the receiver noise floor by 1dB. This implies that the interference should be at least 6dB below the noise floor which, for GSM 1800 mobiles, corresponds to 21 dBµV/m. This is 4dB less than the coordination trigger level of 25 dBµV/m on which the previous calculations were based50.

Figure 10.2 shows that the geographic limits are pushed further north by around 30 km. The sterilised area is increased to 41,000 km2 covering a population of around 18 million.

10.4.2 Relaxed cross border constraints

Cross border interference limits are often (sensibly) set conservatively. We have therefore considered what might be an acceptable upper limit to the interference exported to France at 1800 MHz.

In addition to identifying the cross border field strength limits ERC Recommendation T/R 22-07 also gives the minimum field strength to be protected as 42 dBµV/m and the co-channel C/I for multiple interferers as 9dB suggesting that a total interference of 33 dBµV/m might be tolerable for GSM 1800 mobiles51. Calculations were therefore

49 Operation would be possible with lower radiated powers however this would reduce a station’s coverage area and diminish its commercial viability. We have therefore assumed a minimum ERP of 1 kW.

50 See earlier discussion in Section 10.3.

51 This may be an overly optimistic level as no allowance for shadowing is made, and the C/I with T-DAB may be different. However, we note that in the MOU between the UK and France on coordination in the DCS 1800 MHz band the UK accepts interference at 10m above ground level at this level from fixed links in France.

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repeated with the maximum permissible cross border signal raised to 43 dBµV/m52 for the mobile antenna height of 1.5m. The results are shown in Figure 10.3.

Figure 10.2: The maximum permissible T-DAB ERPs when operating on a no interference, no protection basis.

Figure 10.3. The maximum permissible ERPs for T-DAB transmitters to meet the relaxed limit of 43 dBµV/m in France.

52 This is just 33 dBµV/m scaled for the larger T-DAB bandwidth.

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Under these more relaxed conditions, local digital radio would be usable in all areas of the UK with the exception of about 1000 km2 in the south eastern corner (the green, brown and red areas).

10.4.3 Overcoming the restrictions

At these frequencies coverage is considerably more limited than at the commonly used lower frequencies and it is therefore not realistic to consider the use of lower transmit powers from single sites as modelled here. However, T-DAB has the capability to provide coverage from a network of transmitters all broadcasting the same programmes on the same frequency. Such networks have not been modelled here but other work53 indicates that single frequency networks (SFNs) could be implemented at these frequencies with transmitting stations located every 10 to 20 kilometres with powers of 10 to 100W. These lower powers cannot be directly related to the transmit powers illustrated in the figures above because of the different network configuration. Nevertheless, use of SFNs holds the promise of significantly reducing the exclusion zones identified here albeit at the cost of additional broadcast stations.

It is also worth noting that directional antennas and geographic features could be used to reduce interference levels into France.

10.5 Conclusion

Single transmitter local digital radio could be operated in the 1800 MHz GSM base station transmit band. If operated on the basis of no interference and no protection or on the basis that interference levels in France could be similar to those currently accepted from UK GSM networks, the broadcast networks would be excluded from an area running from Suffolk to the south east corner of the country and along the south coast, and extending up to 170 km inland from the coast. Although this is a large area of the densely populated south east of the UK, a substantial proportion of the population could be served elsewhere in the country.

The use of multiple transmitters in a single frequency network to provide local coverage would be expected to reduce the size of the exclusion zones, although it would increase infrastructure costs54.

Under conditions that might be described as the maximum potentially acceptable level of interference, the restrictions would reduce to exclusion from a few thousand square

53 R. Brugger, Single–frequency networks at 1.5 GHz for Digital Audio Broadcasting, EBU Technical Review, Winter 1993, pp 3 –13.

54 Finding additional sites could be a significant problem in establishing SFNs.

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kilometres of the south eastern tip of the UK plus a few small areas along the south coast.

Finally we note that, although it is unlikely that any of the GSM operators would dispose of their 1800 MHz spectrum as assumed in this scenario, the 1800 to 1805 MHz band is currently assigned to the TFTS service which has not been taken up. These results suggest that an alternative use of these frequencies could be for digital radio broadcasting.

10.6 Tentative assertions

5Introducing a high power system into spectrum planned for low power imposes significant constraints;

5Measures, such as directional antennas or multi-transmitter networks (utilising lower power transmitters) can mitigate the effect of higher power emissions but come at a cost.

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11. PART OF THE 1800 MHZ BAND RE-ALLOCATED TO FIXED LINKS

11.1 Objective

This scenario explores the situation in which fixed links and mobile services are mixed in a cross border situation at 1800 MHz. In particular, this scenario was used to examine the impact of fixed links on mobile services. The implications of interference for fixed link services are not assessed in detail for this case but are considered in other scenarios.

11.2 Background

The duplex frequency band, 1710 to 1785 MHz paired with 1805 to 1880 MHz, is widely used for GSM 1800 networks across Europe. Although its use for mobile services is identified in Mobile Directive 96/2/EC, its use for GSM technology is not mandated in the same way as in the original 900 MHz band and other technical standards could be used. Where it is used for GSM 1800, use of the band is harmonised through ERC Recommendation ERC/REC/(95)03.

Within the FAT and within the ECAT the band is allocated on a primary basis to the Fixed and Mobile Services. Prior to its use for mobile services the band was widely used for civil and military fixed links.

In the UK the band is almost entirely assigned to the four GSM operators. In France part of the band was assigned to GSM operators and part continued to be used for tactical links by the military. It is understood that the military spectrum has been vacated and will be assigned to the mobile operators. In Belgium, the Republic of Ireland and the Netherlands, the band is entirely assigned to the GSM operators.

11.3 The scenario

This scenario considers the situation in which the two UK mobile operators with both 900 MHz and 1800 MHz spectrum decide that their 900 MHz allocation provides adequate capacity for their foreseen needs in the less populated parts of the country. They therefore choose to sell their 1800 MHz spectrum in rural parts of Northern Ireland to others who have identified a market for low capacity point to point links in the band.

Because Fixed Services have a primary allocation within the band, the UK claims that the fixed services are entitled to full protection under the Radio Regulations. The Republic of Ireland decides that the spectrum already allocated to GSM 1800 is to

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remain so55 and the two countries agree that fixed link deployments in Northern Ireland should not cause noticeable interference to the existing GSM 1800 networks in the Republic, and that future GSM 1800 base station deployments should likewise not cause noticeable interference to fixed links already deployed56. In view of the fairly limited use of the 1800 MHz frequencies for mobile coverage in rural areas of the border, the Irish authorities take a fairly relaxed attitude and it is agreed that the maximum level of interference into the GSM 1800 system is to be based on the minimum field strengths to be protected and the minimum C/I ratios as defined in T/R 22-07. The resulting maximum levels of interference are 29 dBµV/m for base stations and 33 dBµV/m for mobiles57. The equivalent field strengths for emissions from fixed links with a 3.5 MHz bandwidth are 41 dBµV/m and 45 dBµV/m respectively.

We note that these levels are noticeably higher than the trigger levels for coordination set in T/R 22-07 (25 dBµV/m at the border for non preferential frequencies). However, they are equivalent to the levels of interference that the UK accepts from fixed links in France58.

To model this situation it was first assumed that the fixed link operators in Northern Ireland adopt a policy of pointing away from the border all link ends which transmit in the GSM 1800 base station receive band (so providing about 22dB of protection to GSM base station receivers suffering interference from point to point transmitters and to point to point receivers suffering interference from GSM base stations). Interference from fixed links into GSM base stations and into GSM handsets were both modelled.

Eight Mbits per second (channel bandwidth of 3.5 MHz) fixed links were assumed to radiate a maximum of 800W EIRP from directional antennas mounted 20m above ground level. GSM mobiles were taken to have an antenna height of 1.5m and base stations a height of 20m above ground level.

11.4 Results

To illustrate the impact of protecting the GSM 1800 networks in the Republic of Ireland, the maximum EIRPs of fixed links in Northern Ireland were determined such that the

55 We note that ComReg proposed the use of spare GSM 1800 MHz spectrum for non-GSM broadband wireless services but decided not to proceed after consultation.

56 As discussed later, interference to the fixed links will be the dominant restriction on usability. For the moment we concentrate on interference into the GSM network.

57 T/R 22-07 gives the minimum signal levels to be protected as 38 for base stations and 42 for mobiles with a minimum C/I of 9 dB in both cases.

58 MOU between France and the UK on coordination in the 1710 – 1785 and 1805 – 1880 MHz bands.

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interference levels were not exceeded for a number of representative base station and mobile locations.

11.4.1 Protecting GSM 1800 base stations

Figure 11.1 shows the geographic restrictions on radiated powers that would have to be applied to fixed links in order not to exceed the agreed field strength limits at representative GSM 1800 base station locations in the Republic of Ireland. Within the dark blue coordination zone radiated power would be restricted to between 80W and 800W ERP depending upon its actual location. Within the light blue zone the limit is 8W to 80W ERP, and 0.8W to 8W ERP within the red zone. The restrictions extend up to around 30 km from the border.

80W – 800W

8W – 80W

0.8W – 8W

Figure 11.1: The geographic restrictions on the maximum EIRP that can be radiated by fixed links in the neighbourhood of the border. The red circles mark the location of GSM 1800 base stations presumed to be protected in the Republic of Ireland.

These results are for links that point parallel to the border. Links which point further into Northern Ireland will benefit from a higher level of attenuation (see Figure 11.2). At 30° relative to the border the antenna will provide an additional 9dB of attenuation. Thus for approximately two thirds of base station deployments the restrictions identified in the previous paragraph would be reduced by 10 dB (so that EIRPs would be limited to

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between 80W and 800W in the green rather than the blue zone). In these cases the transmit power restrictions would apply up to about 10 km from the border.

Border

90° 120°

22 dB 31+ dB Attenuation across the border

Figure 11.2: Illustration of how interference from a link at 30° to the border will benefit from an additional ~10dB of attenuation across the border towards Irish GSM base stations. A representative antenna pattern is shown on the right.

11.4.2 Protecting GSM 1800 mobiles

The restrictions on fixed link EIRPs to protect GSM 1800 mobiles are shown in Figure 11.3.

80W – 800W 8W – 80W 0.8W – 8W

Figure 11.3: The geographic restrictions on the maximum EIRP levels required to protect GSM 1800 mobiles in the vicinity of the border.

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Comparison with Figure 11.1 shows that the restrictions are dominated by the protection needs of the base stations.

11.4.3 Protecting the fixed links

The above analysis shows that the restrictions on point to point systems would not be too onerous in terms of restrictions on power radiated across the border. However, as shown in other scenarios (see for example “Public wireless DSL in the 2010 to 2025 MHz band”) fixed link services themselves are very sensitive to interference.

In this case, signals from the GSM 1800 base stations would be received by the fixed link terminals facing the border causing a serious degradation in their performance. A simple interfering field strength prediction59, Figure 11.4, shows that base stations to the south of the border alone would preclude fixed link usage in most of Northern Ireland. Interference from base stations across the western border (not included in the prediction in Figure 11.4) would preclude operation across the whole of the country.

Figure 11.4: Interfering field strengths in Northern Ireland caused by GSM 1800 base stations to the south of the border. To avoid a noticeable level of interference to the fixed links the interfering signal would need to be less than 9 dBµV/m.

59 Interference levels were predicted for 0.1% of time, with interference deemed noticeable if it raised the noise floor by 0.2dB or more. The impact of interference from multiple base stations was ignored here (and would increase the level of interference).

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11.5 Conclusion

Operation of fixed links within 10 to 30 km of the border could be achieved without causing excessive interference to the GSM 1800 network provided fixed link terminals transmitting in the base station receive band pointed away from the border, and provided EIRPs were restricted in the area of the border.

However, interference from the GSM 1800 network into the fixed links would degrade their performance to such an extent that their use would be precluded over the majority of Northern Ireland.

11.6 Tentative assertions

5Fixed link services, with their requirements for high availabilities, are severely impacted by cross border interference and can only practically be coordinated with other systems which also utilise highly directional antennas;

5Co-existence of wide area or mobile services with existing high availability, high sensitivity receivers is problematic.

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12. PORTABLE WIRELESS DSL IN THE 2010 TO 2025 MHZ BAND

12.1 Objective

This scenario examines the situation in which the band at 2010 to 2025 MHz, currently harmonised for self provided 3G mobile services, is opened for licensed use for both fixed and mobile services.

For the Harmonisation Study, this situation is compared with the one in which both the UK and its neighbours permit the deployment of self provided UTRA TDD networks in this band.

12.2 Background

The 2010 to 2025 MHz band is allocated on a co-primary basis to Fixed and Mobile services in both the FAT and the ECAT, and at WARC 92 it was identified as part of the spectrum to be allocated to IMT-2000. In 1999 a harmonised approach to the use of IMT-2000 spectrum was set by ERC Decision (99)25, and this identified 2010 to 2025 MHz for IMT-2000 TDD and the sub-band 2010 to 2020 MHz for self provided applications. The ERC Recommendation (01)01 provides a basis for cross border coordination of UTRA systems although it has not yet been adopted by any Administration.

To date, there has been little interest from industry and there have been no moves to open this spectrum for self provided applications. A few countries, for example Germany and the Netherlands but not the UK or the Republic of Ireland, licensed the 2020 to 2025 MHz TDD sub-band to 3G mobile operators along with IMT-2000 FDD spectrum. However, there have been no TDD deployments so far. France is understood to still operate tactical military point to point links at these frequencies with the intention of migrating the band to IMT-2000 at a future date.

Over the past few years there has been continuing interest in broadband wireless access and in the use of TDD with new allocations of unpaired spectrum for mobile and fixed services and several new product offerings in the 2.4 to 3.5 GHz frequencies. These products60 are claimed to overcome the shortcomings of earlier FWA equipment through higher capacities, improved range and resilience to multipath, lower costs and, in some cases, through the ability to support nomadic applications.

60 Some of the companies promoting the benefits of non-line of sight FWA technologies are Alvarion, BeamReach, CoWave, Navini, Oak and Vectrad.

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12.3 The scenario

This scenario considers the situation in which there is a continued lack of interest in self provided IMT-2000 applications. The UK therefore takes the opportunity to licence the spectrum 2010 to 2020 MHz for any combination of fixed and mobile services, and places a minimum of technical constraints on the licensee other than those necessary to ensure compatibility with adjacent services. The licensee is assumed to elect to implement a mobile broadband fixed wireless access system exemplified by the Portable Wireless DSL (PWDSL) offering from Oak BV.

With the exception of France, the UK’s neighbours decide to continue to reserve the spectrum for self provided IMT-2000 systems and deployments begin shortly afterwards. These self provided systems are extensively deployed in urban areas, both indoors and outdoors, but provide only local coverage using configurations similar to the micro cell layer of a conventional 3G network. These neighbours agree that ERC/REC/(01)01 is a suitable basis for cross border coordination between their deployments and the PWDSL systems in the UK, and fix the maximum field strength at borders as 36 dBµV/m. However, they also adopt a light licensing regime for self provided systems which simply limits the maximum EIRP to 25W to avoid excessive cross border interference but does not check that the cross border limits into the UK are met.

The UK licences provide that UK PWDSL EIRPs are limited in the same way as the existing 3G licences61 and also requires that the field strength limit of 36 dBµV/m is adhered to.

The French are assumed to take time to decommission their existing fixed links in the band and, in the meantime, the UK and other neighbours agree to coordinate deployments with the French Administration. Thereafter, the French also deploy self provided UTRA TDD networks.

The PWDSL technology makes use of adaptive antennas to maximise both network capacity and frequency re-use. For the purposes of modelling it is assumed that 8 contiguous PWDSL carriers are located at each base station and occupy the same 5 MHz of spectrum as a UTRA TDD carrier. Further, all 8 frequencies are assumed to be reusable at every base station. PWDSL deployments are taken to be for wide area usage and antenna heights are therefore fixed at 20m above ground level.

The narrow beams formed by the adaptive antennas of PWDSL would be expected to reduce average cross border signal levels but no account of this benefit has been allowed for in the modelling62.

61 3G EIRPs are limited to a maximum of 62 dBm per carrier or 58 dBm per MHz, whichever is the more restrictive. In fact the PWDSL technology modelled here has a maximum EIRP per carrier of 56dBm.

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Self provided UTRA TDD networks are assumed to deployed for outdoor use but only over a limited area. Antennas have therefore been modelled at a height of 4m above ground level.

The fixed links in France are modelled as using high gain (29.5 dBi) antennas mounted 20m above ground level.

12.4 Results

We first consider the situation in which France has decommissioned fixed links in the band and deployed self provided UTRA TDD systems. The impact of coordination with their fixed links is considered subsequently.

Both PWDSL and UTRA operate in TDD mode in this scenario. Interference is therefore likely to be most severe between base stations and this is the interference mechanism considered here.

12.4.1 PWDSL with UTRA TDD in neighbouring countries

PWDSL base stations will be affected both by the need to control transmitter powers so as not to breach the agreed field strength limit at the coast of France, and by interference radiated from UTRA deployments in France.

Figure 12.1 shows the limits on the EIRP that PWDSL base stations can radiate towards France and still conform to the cross border agreement. The area of this coordination zone extends up to 200 km from the French coast and amounts to a land area of 24,000 km2. The calculation was performed for the maximum transmit power of 56 dBm EIRP per carrier although a good many base station deployments would be expected to operate at lower powers. Close to the UK coast radiated powers could be limited to 18 dBm per carrier or less.

Figure 12.2 shows the level of interference that would be caused by UTRA TDD base stations operating on the coast of France. As noted above, we assume that the only practical restrictions on interference from self provided systems would be set by the maximum permitted EIRP of 25W, and that the cross border limit would not be enforced63.

62 Similarly, the TDD nature of PWDSL and UTRA TDD means that base stations will not be transmitting continuously. For the purposes of modelling the networks are assumed to be heavily download biased and base stations are modelled as transmitting 100% of the time.

63 In contrast deployment of PWDSL in the UK would be by licensed operators who would be expected to respect the cross border limits.

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35 – 33 dBW 32 – 30 dBW 29 – 27 dBW 26 – 24 dBW 23 – 21 dBW 20 – 18 dBW < 18 dBW

Figure 12.1: Geographic restrictions on the EIRP level radiated towards France in order not to exceed the limit of 36 dBµV/m (in 5 MHz) at the French coast. Each PWDSL base station is assumed to have eight carriers giving a maximum EIRP of 35 dBW.

Figure 12.2: The maximum interfering signal levels that would be generated by 25W EIRP UTRA TDD base stations on the coast of northern France and received at UK PWDSL base stations.

The interference from France would have minimal impact on PWDSL base stations provided it was at least 6dB below the receiver noise floor which corresponds to an

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interfering signal level of 24 dBµV/m64 (in 5 MHz). Thus interference would have some effect on PWDSL base stations in all except the darkest blue areas of Figure 12.2, an area extending up to 250 km from the French coast and covering some 35,000 km2 of the UK.

Note that, because PWDSL base stations operate in TDD mode, the impact of transmitted power limits occurs during base station transmit periods and the impact of received interference during base station receive periods. The overall effect on coverage is therefore determined by whichever effect is the larger.

12.4.2 Overcoming the restrictions

Restrictions on transmitter powers and interference from French UTRA systems will both have the effect of reducing the coverage area of PWDSL base stations, and both effects can be mitigated through the use of directional antennas. Directional antennas pointing away from the French coast would be able to transmit at higher powers and would also attenuate interference coming from France. This fits well with PWDSL as sectored sites would typically be used in any deployment.

Along a small proportion of the coast, where the largest radiated power reductions would be required, directional antennas illuminating cells from one side would likely be needed.

12.4.3 UTRA TDD in adjacent countries

In this section we consider the effects of cross border interference in the situation in which both the UK and its neighbours permit the deployment of self provided UTRA TDD systems. As before we assume that a light regulatory regime is instituted in which base station EIRPs are limited to 25W but no effort is made to ensure that the cross border field strength limits are adhered to.

In this situation there will be no coordination zone within which transmitter powers are controlled although there will be interference from UTRA systems deployed in France. Self provided UTRA TDD base stations will be designed to work in the presence of co- channel interference from other UTRA base stations, and the level of interference from France will be less than it would be from neighbouring UTRA base stations in the UK. The impact of interference between UTRA systems in France and the UK is therefore expected to be minimal.

64 This level is calculated from the receiver noise floor adjusted to allow for antenna gain and the bandwidth of a PWDSL carrier.

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12.5 Coordination with fixed links in France

To examine the potential implications of coordinating UK deployments with existing high availability fixed links in France, limits on EIRPs in the UK were determined on the basis that the fixed link receiver noise floors should not be increased by more than 0.2 dB. The resulting geographic restrictions on levels radiated towards France by PWDSL and UTRA TDD deployments are shown in Figure 12.3 and Figure 12.4 respectively.

The areas over which EIRPs would be restricted are extensive. The extent to which this would restrain deployment in the UK would depend on the number of French links but, unless the number were small, deployment of either PWDSL or self provided UTRA TDD systems would be very largely impractical.

65 – 56 dBm 55 – 46 dBm 45 – 36 dBm 35 – 26 dBm 25 – 16 dBm 15 – 6 dBm < 6 dBm

Figure 12.3: Geographic restrictions on EIRPs radiated towards France by PWDSL base stations required to avoid disturbance to fixed links in France.

12.6 Conclusion

Wide area PWDSL base stations deployed in the 3G spectrum at 2010 to 2020 MHz will suffer from reduced coverage over an area of up to 35,000 km2 in the south east of main land UK when self provided UTRA TDD systems are deployed in neighbouring countries. The effects, however, can be mitigated through the use of sectored sites which are anyway likely to be used in any extensive deployment.

Where self provided UTRA TDD systems are deployed in the UK and in neighbouring countries, cross border effects are expected to be minimal. Directional antennas would again mitigate any degradation.

44 – 33 dBm 34 – 23 dBm 24 – 13 dBm 14 – 4 dBm 4 – -5 dBm -6 – -15 dBm < -15 dBm

Figure 12.4: Geographic restrictions on EIRP levels radiated towards France by UTRA TDD systems located in the UK required to avoid disturbance to fixed links in France.

However, so long as fixed links are deployed in France in any number, the degree of protection that they would need to be afforded will make deployment of both PWDSL and UTRA TDD networks difficult if not impractical.

12.7 Tentative assertions

5Mixing high powered, narrow band mobile systems with low powered, wide band systems results in greater restrictions to the narrow band network;

5Mixing mobile networks with fixed links leads to large exclusion zones.

13. FIXED LINKS IN THE 2.7 - 2.9 GHZ AERONAUTICAL BAND

13.1 Objective

This scenario examines the potential for autonomy when the existing cross border service has a very high protection requirement.

13.2 Background

The band 2.7 to 2.9 GHz is allocated to the Aeronautical Radionavigation Service on a primary basis in both the FAT and in the ECAT, and it is used extensively throughout Europe for airfield, surveillance and air traffic radars. Its use for air traffic and surveillance radars is considered a safety service65 which cannot accept harmful interference and these installations are therefore afforded a high degree of protection.

With the development of alternative technology, such as narrowband radars, a hypothetical situation could be considered whereby the use of an alternative band for aeronautical radars may be envisaged, thus freeing the 2.7 to 2.9 GHz band. This scenario therefore considers the situation in which the UK decides to entirely cease the operation of radar in this band and to use it for fixed point to point links.

13.3 The scenario

Fixed services have no allocation in this band and their operation would therefore be on a no interference no protection basis. On the other hand Aeronautical radars, having a safety of life function, require a high level of protection.

To avoid noticeable interference to radars in continental Europe the UK decides that interference should be controlled so as not to exceed a level 10 dB below the radar receiver noise floor, this being the protection criteria recommended in ITU-R Recommendation M.146466. In view of the safety of life function of these radars, the UK further decides that each fixed link deployed in the UK has to be checked for conformity with this limit for all known radars within 500 km of the fixed links terminals. The scenario assumes that the UK’s neighbours cooperate with this approach and provide the location and technical description of those radars that could be affected.

The type and location of aeronautical radars in France and other neighbouring countries are not currently known to Ofcom. To model this situation we therefore

65 As defined by Article S.410 of the Radio Regulations.

66 ITU-R Recommendation M.1464 identifies the characteristics of, and protection criteria for, radionavigation and meteorological radars operating in the 2.7 to 2.9 GHz band.

identified the location of airfields along the coast of Northern France and assumed that each operated an air traffic radar in the band. The maximum acceptable level of interference was determined for each different type of radar characterised in ITU-R M. 1464, and the level which would be acceptable to all ATC radars was taken as the limit (some weather radars are more sensitive). This corresponds to a signal level of –6 dBµV/m (in a bandwidth of 3.5 MHz67) at the antenna.

ECC Recommendation (02)09 gives conditions under which digital cordless cameras could be operated within the band. For comparison with the limit selected above we note that it recommends that an Administration should be considered as affected by cordless camera operation if the field strength generated at the border exceeds -2 dBuVm (in a bandwidth of 8 MHz).

The scenario was modelled by determining the maximum EIRP levels that fixed links in the UK could transmit towards the French coast without exceeding the maximum acceptable level of interference at any of the airfields identified along the coast of France. Fixed link antennas were mounted at 20m above ground level, and radar antennas at 10m above ground level. In line with ECC Recommendation (02)09 the probability of interference was set at 0.001%.

13.4 Results

The minimum path lengths for 4 GHz links currently permitted in the UK are 16 km for high capacity links and 24.5 km for low capacity links and we have therefore taken 20 km as an indication of the minimum useful length for a link in the 2.7 to 2.9 GHz band. In this case a minimum useful EIRP would be between 50 and 500 mW (see Figure 13.1).

Figure 13.2 shows the geographic restrictions on EIRPs radiated towards France. These restrictions would only apply to a link which pointed at a French radar. However, with the affected areas potentially extending several hundred kilometres into France, the likelihood of encompassing at least one airfield will be high68. Therefore, even at the minimum useful power levels identified above, very large areas of the UK (the red area in Figure 13.2) would be excluded from use.

67 A narrow bandwidth fixed link was assumed here as this minimises the acceptable level of interference for narrow band radars.

68 Links on the south coast of the UK, operating in the range 50 to 500 mW EIRP, would generate interference across ~25,000 km2 of French territory, and therefore have a high probability of impinging upon a French airfield radar.

Figure 13.1: Fixed link path lengths in the 2.7 to 2.9 GHz band for various EIRP levels with 1.2m or 3.7m antennas.

Figure 13.2: The geographic restrictions on the EIRPs that could be radiated towards a French radar site without exceeding the interfering signal limit of -6 dBµV/m.

It should be noted that the restrictions illustrated in Figure 13.2 are derived from just six airfields along the northern coast of France. With the large coordination distances involved here, airfields in Belgium, the Netherlands, the Republic of Ireland and parts of Scandinavia would further increase the restrictions in the UK.

13.5 Conclusion

The restrictions required to ensure that fixed links in the UK did not interfere with aeronautical radars in continental Europe would be so onerous as to preclude any useful deployments69.

We note, however, that work by the ECC70 shows that low power (0 dBW EIRP) devices can share with safety of life aeronautical radars under controlled conditions.

13.6 Tentative assertions

5Any service sharing spectrum with aeronautical radars on a no interference, no protection basis will be subject to stringent limits on power levels that can be radiated. Nevertheless, there are some low power applications that may be able to successfully share;

69 Note, the impact of radar emissions on fixed links could also be significant but has not been considered as part of this scenario.

70 See ECC Recommendation (03)09 and ECC Report 6.

5Co-existence with existing high sensitivity receivers (such as safety of life equipment) with high EIRP systems is likely to be impractical.

14. FWA SPECTRUM AT 3.5 GHZ IS RETURNED TO ENG/OB USE

14.1 Objective

The objective is to determine what restrictions would apply to the deployment of temporary links used for outside broadcasting in the 3.5 GHz band currently assigned to FWA operators.

14.2 Background

The 3.4 to 3.6 GHz band is allocated on a primary basis to Fixed and Fixed Satellite Services in the FAT, and to Fixed, Fixed Satellite and Mobile services on a primary basis in the ECAT. An ERC Recommendation71 identifies harmonised channel plans and block allocations for point to point, point to multi-point, and ENG/OB applications between 3410 and 3600 MHz.

Several countries, including France, the UK and the Republic of Ireland have assigned spectrum in the band to FWA operators. In the UK the band is allocated between ENG/OB, FWA and the Home Office (for Heli-Telly).

14.3 The scenario

This scenario considers the situation in which the FWA spectrum in the UK is returned to Ofcom and re-allocated to ENG/OB for temporary uni-directional video OB links. The FWA networks already deployed in France are assumed to continue in operation and to be deployed extensively in urban areas.

The re-allocation by the UK conforms with the FAT and with the ECAT. However, France is assumed to insist on full protection of its existing and future FWA systems. An MOU is therefore agreed which limits interference on main land France to a level (16dBµV/m) which would cause a rise of no more than 1dB in the noise floor of the subscriber’s receiver. We further assume that the FWA systems will have been designed to give a high availability, say 99.9%. In order that the interfering signal produce no noticeable effect it should not exceed the limit for more 1/10 of the planned outage, which would be 0.01%. However, the temporary nature of the OB links means that any given frequency will be unused for much of the time. The interfering signal is therefore permitted to exceed the agreed limit for 0.1% of the time72.

71 ERC Recommendation 14-03.

72 Note that the exclusion areas are quite sensitive to this assumption. Exclusion areas have therefore been calculated for a range of values. They can be found in the separate appendices.

To model the situation an OB video link transmitter is assumed to radiate directly towards the French coast on the subscriber receive frequency from an antenna 20m above ground level. The maximum permissible EIRP was then determined as a function of distance back from the UK coast.

14.4 Results

Figure 14.1 shows the areas from which an OB link could transmit a given EIRP and not exceed the permitted interference level. Thus, to be sure of not exceeding the limit, the EIRP would be restricted to 1kW in the dark blue areas.

Figure 14.1: Areas colour coded by the EIRP that could be radiated directly towards France without exceeding the limit of 16dBµV/m more than 0.1% of the time.

Clearly, the area of the UK where restrictions would apply is large extending well beyond the Midlands. However, two points have to be considered.

5Firstly, links of around 100W EIRP would provide useful path lengths and could be used without restriction in all areas except those coloured green, orange and red.

5Secondly, these results are for links pointing directly at the French coast whereas many links would point elsewhere. Inspection of Figure 14.1 shows that about one third of links in the south of the UK would point towards the French coast (the

proportion becoming smaller as the link moved northwards). Signals from the other two thirds would benefit from an additional 20dB of attenuation in the direction of France.

Taking the two points together suggests that in the dark and light blue areas links of up to at least 100W EIRP could be used in any direction, and powers of up to 10kW EIRP could be in all except one sixth of directions. And, in the green and orange areas links of up to at least 100W EIRP could be used in all directions except around 30% which would point at the French coast.

The red area would be restricted to EIRPs of less than 10W and to pointing away from France.

In practice the above restrictions can probably be further relaxed for two reasons:

5Firstly, CPEs in France use directional antennas with beam widths of around 20°. Therefore, about 75% of CPEs will anyway point away from potential sources of interference.

5Secondly, the temporary nature of OB links further reduces the impact of any interference. By way of illustration, if the requirement not to exceed the interference limit was relaxed from 0.1% to 1% of the time, the geographic extent of the above restrictions would be roughly halved.

14.4.1 Coordination

The above restrictions would protect all parts of the French main land and require no further coordination with the French Administration. However, further use could be made of the spectrum with some limited cooperation with the French authorities. Two possibilities are:

5FWA deployments in France may not become extensive and will likely remain localised to the conurbations. With suitable agreement, OB links could therefore be used in the restricted areas (the green, orange and red areas) provided that they did not point at any of these conurbations;

5Although OB transmitters operate in 20 MHz channels the radiated power is concentrated within 8 MHz, with power outside this range reduced by 30 dB. Thus an agreement could be made whereby OB equipment pointing towards France used specific frequencies which were not used in France (or at least not close enough to the coast for interference to be an issue).

14.5 Conclusion

The spectrum at 3.5 GHz used by the French for FWA applications could be used in the UK for uni-directional outside broadcast links in the greater part of the UK, and in the southern parts of the country with some restrictions on EIRPs and pointing directions.

With limited cooperation between the UK and French Administrations (agreement on areas to be protected and the identification of specific frequencies for OB use) the restrictions could be further relaxed.

14.6 Tentative assertions

5Where high availabilities are required autonomous operation is more difficult and constraints can be significant although where the two conflicting systems both use highly directional antennas the effects are reduced;

5A specific aspect of the autonomous system can help (its intermittent use in this case);

5Coordination between two conflicting systems taking account of factors such as location and technical characteristics will help to maximise the usability of the spectrum.

15. TERRESTRIAL FIXED SERVICES AT 32 GHZ

15.1 Objective

The objective of this scenario is to determine what additional restrictions there would be on the deployment of fixed links in the Fixed Services band at 31.815 to 32.319 GHz paired with 32.627 to 33.131 GHz if the requirement to adhere to CEPT channel plans and ETSI standards was removed.

For the Harmonisation study this scenario will compare the density of fixed links that could be deployed in the UK in the situation in which assignments conform to the existing harmonised channel plans and equipment standards with the situation in which the UK permits users to deploy equipment to any recognised standard or channel plan.

15.2 Background

Fixed Services have a primary allocation, along with other services, in the band 31.8 to 33.4 GHz, both under the FAT the ECAT. Harmonised channel plans73 have been developed and a number of European standards74 apply to fixed equipment at these frequencies.

In the UK, one third of the band has been opened for fixed links with the remaining two thirds allocated to general fixed services. The latter frequencies are potentially available for assignment to companies who would manage the spectrum and define equipment standards to avoid harmful interference to others. So far no use has been made of the band. It is also believed that, at the present time, the UK’s nearest neighbours have no equipment operating in the bands.

15.3 The scenario

This scenario compares the situation in which companies make use of the relaxed UK regulations to deploy lower cost fixed link equipment which does not align with the CEPT channel plan or technical standards, with the situation in which all UK assignments are made in accord with the harmonised channel plan and standards.

The UK’s nearest neighbours are assumed to deploy fixed link equipment at the same time but in accord with the European standards. Because the UK is compliant with the Radio Regulations it claims, and obtains agreement from its continental neighbours,

73 CEPT Recommendation T/R 01-02

74 ETSI specification EN 300 197

that cross border coordination should be on a station by station basis, with existing stations taking precedence.

To model this situation, representative fixed link receivers were placed on the coast of France pointing at the UK and the maximum transmit power that would not produce noticeable interference to the French links was determined. The exercise was repeated at different distances back from the UK coast to determine the size of the exclusion area that would apply to different transmit powers. The result is shown in Figure 15.1.

45 – 41 dBW 41 – 37 dBW 37 – 36 dBW 36 – 32 dBW 32 – 28 dBW 28 – 27 dBW 27 – 23 dBW 23 – 19 dBW < 19 dBW

Figure 15.1: Maximum transmit EIRPs for fixed links pointing towards a co-channel fixed link receiver on the coast of France.

The links in France were assumed to be designed for an availability of 99.99%. The maximum acceptable interfering signal was taken to be that which would not raise the receiver noise floor by more than 0.2dB75 for more than 0.001% of the time. All antennas were assumed to be mounted 20m above ground level and the victim receiver was assumed to use a 0.9m dish.

75 This figure was taken from an agreement (the Berlin Agreement 2001, http://ba.bmwa.bund.de/) between France, Germany and others (but not the UK) on coordination of Fixed Services between 29.7 MHz and 43.5 GHz.

15.4 Results

Links at this frequency are most likely to be used with path lengths of a few kilometres. Allowing for rainfall and fade margins to meet an availability of 99.99% radiated powers of between 10W and 100W (20dBW) EIRP will be required with the smaller (0.3m) dishes. We have, therefore, evaluated interference into France on the basis of EIRPs of up to 100W76.

Figure 15.2 gives an expanded view of the EIRP limits along the south coast. These results show that interference would be possible from UK links within around 100 km of much of the south coast although this distance increases up to around 150 km in places (the coloured areas of the map).

19 – 14 dBW 14 – 9 dBW 9 – 4 dBW

4 – -1 dBW -1 – -6 dBW -6 – -11 dBW -11 – -16 dBW

-16 – -21 dBW -21 – -26 dBW < -26 dBW

Figure 15.2. EIRP limits for fixed links on the south coast of the UK pointing towards France required to avoid interference to co-channel French links.

In practice cases of interference will be less common than these predictions would suggest for a number of reasons:

5Links at these frequencies are likely to be deployed largely in and around urban areas where shielding effects will be significant;

5The small angles subtended by the radiated beams significantly reduce the chance of two links interfering. For example, taking a beam width of ±5° (giving an attenuation of 30dB), an interference zone extending 100 km into France, 18

76 Some equipment is capable of transmitting at the lower power required in the absence of rain and of increasing power during rain periods. We understand that this facility is not widely implemented but clearly it would reduce levels of potential interference in France.

frequency pairs and one link per 50 km2 in France, the probability that a new UK deployment on the south coast would cause interference is under 10%;

5Any links which have any downwards tilt in the direction of France will have a significantly reduced footprint in France.

Nevertheless, it is likely that there will be a need for coordination in these areas for a small proportion of links77.

15.4.1 Relaxed regulations

The use of equipment meeting other standards would change the above conclusion if:

5Higher radiated powers were required (generating higher levels of interference in France);

5Receivers were more sensitive (and therefore more susceptible to interference from neighbours);

5Different channel bandwidths resulted in higher levels of interference within the bandwidth of a receiver.

Inspection of a number of products to American ANSI and European CEPT/ETSI standards shows very little difference between receiver performance and link budgets. Typical differences are a few dB. Channel bandwidths are different with CEPT using a raster of 3.5 MHz and the USA a raster of 2.5 MHz. Taking the worst case of two 20 MHz interfering carriers impinging on a single 28 MHz receiver, the interfering power would be only 1.5 dB greater than with a single 28 MHz interfering carrier.

Relaxing the regulations to permit equipment meeting other professional standards will not, therefore, change the extent to which coordination will be needed between the UK and our continental neighbours.

15.5 Tentative assertions

77 Ofcom’s experience at 26/28 GHz is that a few installations in the south east corner of the UK can require coordination.

5At frequencies around 30 GHz coordination with France will be required for a small percentage of fixed link assignments within about 100 – 150 km of the south coast;

5Relaxing adherence to channel plans and equipment standards for millimetre microwave fixed links results in no additional constraints.

16. TECHNICAL OPTIONS

Autonomy is facilitated by any measures which enable co-existence between cross border wireless systems or which reduces the technical constraints. Since the problem is largely one of interference useful measures either reduce the level of interference exported or minimise the susceptibility of a system to interference. This section summarises the main options identified during analysis of the scenarios.

16.1 Options applicable to the scenarios modelled

16.1.1 Radiated power reduction

The obvious way to reduce the level of exported interference is to reduce the radiated power, and this was the option considered most widely in the scenarios modelled. The consequential reduction in range will usually result in the need for more infrastructure and therefore greater costs to the user.

16.1.2 Accommodating interference

For systems in which interference has the effect of raising the noise floor, range and therefore coverage will be reduced. This can again be overcome by increasing the wireless infrastructure, again at a cost to the user.

16.1.3 Directional antennas

Directional antennas can be a useful means of directing emissions away from the border so that the need to reduce radiated power levels is minimised.

16.1.4 Special network planning

For a number of systems it is possible to minimise cross border effects by adopting specific design rules. As an example, in the scenario considering an FWA system in conflict with a cross border TETRA system, it would be possible to reduce the interference effects by ensuring that all the FWA consumer premises terminals in the vicinity of the border directed their transmissions away from the border. Again, there will be a cost to the user in that a non-optimal network design is a likely consequence.

Similarly, where the direction of a point to point link leads to an interference problem, it may be possible to avoid it by replacing the single link with two links each at an angle to the problem direction. Clearly, this approach requires coordination between the systems on either side of the border.

16.1.5 Multi-transmitter networks

Certain systems are able to use multiple, low power transmitters to provide coverage over large areas. The use of multiple transmitter, single frequency T-DAB networks is an example. Cellular networks could also be designed to use smaller low power cells in border areas. Although more transmitters will be involved, the aggregate interference exported across a border can be less.

This could be an effective means of reducing cross border emissions although it would not necessarily reduce the susceptibility of the network to incoming interference. There would be additional costs associated with the need for more transmitters and associated sites, and cross border agreements would need to take account of interference aggregation.

16.1.6 Special protocols

The scenario which examined the use of HF Public Correspondence frequencies showed that interference could be avoided in this case by transmitting only during periods when sky wave propagation ensured that interference would not be caused (or received). An alternative protocol in which transmissions were made only in short bursts after checking that the frequency was unused at the point in time, also provides a possible solution.

However, special protocols of this sort will only be suited to a restricted range of applications, and may require the development of special equipment.

16.2 Other options

Other technical options can facilitate cross border co-existence. These include:

16.2.1 Intelligent systems

Intelligent systems respond to their radio environment and react in a way that minimises or avoids interference. An example is DECT where action is taken to dynamically select another frequency or time slot when interference is detected. This type of system can work well but generally only with other systems of the same type.

16.2.2 Resilient systems

This category covers systems such as CDMA where the modulation scheme minimises the effects of any interference to which it is victim.

Resilient systems can, of course, also be intelligent. Licence exempt technologies such as IEEE 802.11 and Bluetooth are examples.

16.2.3 Smart antenna systems

By transmitting just enough energy in the required direction and only for the duration of the communication, a smart antenna system can minimise the energy radiated in other potentially harmful directions. Similarly, a smart antenna system has the potential to avoid interference temporarily coming from a cross border network. Such systems have the effect of reducing the probability of interference but do not prevent its occurrence.

16.2.4 Smart coordination

Autonomous use of the spectrum does not necessarily imply that there should be no coordination between cross border systems. Indeed, the scenarios modelled have shown that the closer cross border arrangements are matched to the actual operation and location of the systems the greater the degree of co-existence that can be achieved.

The downside of coordination is the time taken to undertake the process whether it be to negotiate an overall agreement or to coordinate each assignment on a station by station basis. But with suitable, automated tools and adequate knowledge of actual deployments there is the potential to use smart coordination as a tool to facilitate maximum use of the spectrum when one neighbour or the other uses it autonomously78.

Such systems will take time to implement. In the meantime it would be possible to negotiate agreements with neighbours that go part of the way. For example, an agreement with the French authorities to protect FWA systems in areas of deployment but to accept higher levels of interference elsewhere was identified as a means of minimising constraints on OB links at 3.5 GHz (see Chapter 14).

78 This issue is addressed, and a phased implementation approach outlined, in the report “Smart spectrum management methods, URS for software tools” developed as part of this project.

16.3 Conclusion

Clearly, there is no panacea to cross border interference to facilitate autonomous use of the spectrum. Different approaches will help by different amounts in different situations, and each of which will require evaluation before autonomous assignments can be made.

17. SUMMARY AND CONCLUSION

The key objective of Part 1 of the National Autonomy project is to identify the extent to which it could be feasible for the UK to achieve a greater degree of national autonomy in the use of the spectrum and the technical restrictions that are likely to apply. The focus of this part of the study has been on the terrestrial mobile, broadcast and fixed services, and on frequencies between 30 MHz and 30 GHz. Table 17.1 at the end of this chapter provides a summary of the main features and conclusions drawn from each of the scenarios.

The scenarios cover a range of different regulatory situations corresponding to the UK exercising greater or lesser degrees of autonomy in its use of the spectrum. In considering and interpreting the overall results it is useful to classify these into three categories of autonomy. Similarly it is helpful to classify the level of technical constraint that would apply to an autonomous spectrum user into a manageable number of categories. Both sets of categories are defined below.

17.1.1 Degrees of autonomy

1. The minimum degree of autonomy considered is where the UK permits a change of technology, or relaxes adherence to technical standards, but does not permit a change to the application. Thus permitting use of a non-harmonised mobile standard in that part of the 900 MHz band harmonised for use with the GSM technology would fall into this category.

2. The second level of autonomy covers the situation in which the UK permits a change of application or service, which conflicts with current European practice, but only to a service which is allocated on a primary basis within the ITU-R Frequency Allocation Table for Region 1.

3. The third level of autonomy considers the situation in which the UK permits change to a service which falls outside the allocations specified by the ITU-R Frequency Allocation Table. In this case operation would be on a no interference, no protection basis in accord with Article 4.4 of the Radio Regulations.

It should be noted that, in the context of this study, autonomous operation does not imply that there would be no coordination with the neighbouring administrations. Whilst this could be appropriate where operation was on a no interference, no protection basis, in all other cases there would need to be agreement at least on the levels of interference that could be exported across the border in both directions.

17.1.2 Levels of technical constraint

The scenarios identified the technical constraints that would apply to the autonomous spectrum user in the UK in terms of the area over which their operations would be

affected either by the need to restrict transmitted power levels or by interference from cross border radio stations, or in terms of the area over which it would not be possible to operate radio stations79. These constraints were grouped into three categories as defined here.

1. Limited restrictions80 – refers to constraints which are broadly in line with what would be expected when UK spectrum use was aligned with that of its neighbours. Scenarios were placed in this category if the sterilised area was less than 10,000 km2 or if the coordination and interference areas were each less than 20,000 km2.

2. Significant restrictions – refers to constraints which, while imposing significant restrictions81 on the spectrum user, would not preclude autonomous use. Scenarios were placed in this group if the sterilised area was less than 30,000 km2 or the coordination and interference areas were both less than 60,000 km2.

3. Severe restrictions – refers to cases where the constraints are likely to make autonomous use of the spectrum impractical. All scenarios with constraints greater than “significant” were placed in this category.

In the case of scenarios which were modelled for the border with the Republic of Ireland, the categorisation was based on the distance back from the border over which the constraints would apply.

17.2 Results

Figure 17.1 shows how the scenarios break down according to the degree of autonomy involved and the corresponding level of constraints on the spectrum user.

79 Referred to as the coordination, interference and sterilised areas respectively.

80 These criteria are based on the observation that with narrow band 450 MHz PMR systems in the UK and France, the coordination area is calculated to cover some 24,000 km2 including London, and that a sterilised area of 10,000 km2 would (just) miss London.

81 Note, in making this assessment judgements were made as to how seriously a business might be affected by the constraints.

Severe FS/GSM (9) Radio/PC (1) restrictions PWDSL/FS (10a) FS/Aero (11) UTRA/FS (10b)

Significant FWA/TETRA (6) T-DAB/GSM (8) restrictions

PMR/TV (3) Limited PMR/PMR (4) OB/FWA (12) Radio/PMR (2) restrictions UTRA/GSM (7) PWDSL/UTRA (10) UTRA/DVB-T (5) FS stds (13)

Change of Change within Change outside technology / Region 1 FAT Region 1 FAT relaxed stds

Figure 17.1: Summary of scenario results in terms of the degree of autonomy achieved and the consequential level of restriction on the spectrum users. Each scenario is identified by the technologies involved and its number (corresponding to that in Table 17.1) given in brackets.

Two observations can be made immediately:

Firstly, there is some trend towards more restrictive constraints as the degree of autonomy moves from, say, a change to a non-harmonised technology to complete autonomy where the new application would be outside the FAT.

Secondly, even where applications outside the FAT are considered and operation has to be on a no interference, no protection basis, the constraints on spectrum users need not always be severe.

More specifically the following conclusions can be drawn.

1. In the case of all the scenarios involving just a change of technology or a relaxation of adherence to harmonised standards, the consequential technical restrictions were found to be limited. The scenarios in this category covered a range of frequencies (from 450 MHz to 1800 MHz) and both mobile and broadcasting services. Note that in the case of Scenario 13, Terrestrial Fixed Services at 32 GHz, the restrictions are limited because of the high frequencies involved and the consequential short propagation distances. The general conclusion is:

ZWhere autonomous use involves only a change of technology, or a relaxation of adherence to technical standards, but no change to the application there are likely to be few additional restrictions on the new application.

2. For the remaining scenarios, whether the change of use is in accord with the FAT or not, the restrictions range from limited to severe. However, if we disregard those scenarios which involve fixed point to point services (Scenarios 9, 10a, 10b82 and 11), and the one scenario at HF frequencies (Scenario 1), we find that for the remaining scenarios the restrictions are either limited or significant. For Scenario 8, Terrestrial DAB local radio at 1800 MHz, the constraints were identified as significant. However, the modelling results show that with a more stringent but still realistic interpretation of no interference, no protection conditions the level of restrictions would increase to severe. The general conclusion is therefore:

ZWhere autonomous use involves a change of service within or outside the scope of the FAT, and the services involved are mobile, broadcast or fixed wireless access, the consequential technical constraints on the new service are variable but often not to the extent of making the new service impractical.

ZWe note that the level of constraints will have to be determined on a case by case basis.

3. Scenarios 9, 10a, 10b and 11 are all subject to severe restrictions as a result of the high levels of availability required and the correspondingly low levels of interference that can be tolerated. The general conclusion to be drawn is:

ZAutonomous operation involving fixed point to point services on one side of the border or the other are likely to be impractical. Other services requiring similarly high levels of availability are also likely to be impractical in general83.

ZNote that Scenarios 12 and 13, FWA spectrum used for OB links, and Terrestrial fixed services at 32 GHz, do not contradict this assertion. In the case of Scenario 12 the links considered were uni-directional and used only intermittently. In the case of Scenario 13 the high frequency meant that propagation distances were short.

4. In Scenario 13 the restrictions were found to be limited due to relatively short propagation distances associated with the high frequency. This is in accord with the

82 Scenario 10 also briefly considered the situation in which fixed links continue in use in continental Europe while PWDSL or UTRA were deployed in the UK. These results are referenced as 10a and 10b respectively.

83 Co-existence with other services is possible in specific circumstances. Thus fixed point to point services can, with careful coordination, co-exist with fixed satellite services.

experience of Ofcom that there is little need for international coordination of fixed links at frequencies around 26/28 GHz. The conclusion is:

ZAt frequencies of 30 GHz and above, autonomous use of terrestrial services will generally be possible with few restrictions.

5. Scenario 1 showed that the long propagation distances typical at HF frequencies make autonomous operation impractical other than under specific, special conditions. There is no sharp cut off to propagation distance with increasing frequency but, as a rough rule of thumb, all services below 30 MHz are likely to be subject to the same limitations. Thus:

ZHF and lower frequencies cannot generally be used without international coordination except under specific, special conditions.

17.2.1 Further observations

Figure 17.2 shows the pairing of autonomous applications in the UK with the different applications in neighbouring countries covered by the scenarios modelled.

on N ati eig plic hb ap ou us r’s mo Mobile Mobile ap no 7 pli to Broadcast cat Au 8 4 5 Broadcast ion FWA FWA 6 2 3 Fixed ptp 10 Fixed ptp

9 10b

12 10a 13

Figure 17.2: This figure shows the pairings between autonomous applications in the UK and spectrum usage in neighbouring countries that were evaluated through scenario modelling. The level of constraints on the autonomous user are identified by the shading: Green – Limited restrictions; Blue (vertical lines) – Significant restrictions; Red (diagonal lines) – Severe restrictions. The numbers refer to the scenario number given in Table 17.1.

Figure 17.2 shows the association of severe technical constraints with point to point services but otherwise shows little correlation between the level of constraints and the service. Nevertheless, the following observations can be made.

1. The two scenarios involving the autonomous operation of broadcast services in mobile bands (Scenarios 2 and 8, Local VHF sound broadcasting in the 66 to 87.5 MHz band, and Terrestrial DAB in the 1800 MHz band) show that broadcasting will be restricted to relatively low transmit powers, and therefore to local services, and to operation in the mobile base station transmit bands.

2. The two scenarios involving the use of broadcast spectrum for mobile services (Scenarios 3 and 5, Digital wide band PMR with digital TV in Band III, and UTRA TDD in spare DVB-T channels) show that such use will generally require fairly detailed coordination or, equivalently, the use of broadcast channels already allotted, and therefore coordinated, for use in the UK. The former scenario also shows how the introduction of digital modulation techniques can facilitate co- existence between services.

3. Scenarios 2 and 8 (Local VHF sound broadcasting in the 66 to 87.5 MHz band, and Terrestrial DAB at 1800 MHz) show how the level of technical restrictions can change significantly with a change in the level of protection afforded to the service in the neighbouring country. Scenario 6 shows how the restrictions can be eased if the geographic areas to be protected from interference are confined to the operational area of the potential victim as opposed to protecting all areas up to the border.

ZThis suggests that agreement on acceptable levels of cross border interference and, where possible, additional coordination between operations on either side of the border will minimise the restrictions under which the autonomous user will have to operate. Of course, such negotiations can take time and delay implementation which in itself could detract from the value of autonomy.

4. Scenarios 4 and 7 (Unrestricted wide band PMR in the 450 to 470 MHz band, and Re-farming of GSM spectrum to UTRA) show that the use of preferred frequencies as a way of equitably sharing spectrum in cross border situations can be lost with the autonomous introduction of a new service.

ZThis suggests that it would be advantageous to agree preferred frequencies in relatively large blocks so as to maximise the possibility of fitting both wide and narrow channel systems within the same scheme.

17.3 Conclusions

The key conclusions that can be drawn from this analysis of the scenario results are:

1. HF and lower frequencies cannot generally be used without international coordination except under specific and rather limiting conditions;

2. At frequencies around 30 GHz and above autonomous use of the spectrum for terrestrial applications will generally be possible with few restrictions;

And for terrestrial mobile, broadcasting and fixed services between 30 MHz and 30 GHz:

3. Where the autonomous use involves only a change of technology, or a relaxation of adherence to technical standards, but no change to the type of application there are likely to be few additional restrictions on the autonomous spectrum user;

4. Where the autonomous use involves a change of service within or outside the scope of the FAT, the consequential technical constraints on the new service will vary depending upon the specific situation, but often not to the extent of making the new service impractical;

5. Where fixed point to point services are involved autonomous spectrum use is likely to be impractical. Other services, requiring similarly high levels of availability are also likely to be impractical.

6. Where autonomous services are operated in broadcast spectrum a fairly detailed level of coordination will be required. Where autonomous broadcast services are operated they will be restricted to low transmit powers and therefore to local coverage.

7. Coordination between autonomous operations and the cross border user of the same frequencies will be an important factor in minimising the restrictions under which the autonomous user will have to operate. Indeed, the closer cross border arrangements are tailored to the specific technologies and their deployment, the smaller the restrictions are likely to be.

8. Defining preferred frequency arrangements in relatively large blocks of spectrum would maximise the possibility of accommodating different systems within the same scheme.

9. The opportunities for autonomous operation are likely to increase as more systems move to the use of digital modulation techniques.

17.4 Northern Ireland

With the border between Northern Ireland and the Republic of Ireland being a land border extending around two sides of the country, cross border problems will be more difficult than between the UK and its continental neighbours. Thus the same general comments as above will apply but the additional costs of, and the restrictions on, autonomous operation will be greater.

It is worth noting that, because cross border interference levels are more restrictive in this case, the gain to obtained from protecting operational areas (or individual stations), rather than applying a level of protection at the border, will be greater.

No. Scenario Regulatory model Coordination / Summary Notes Conclusion Interference area 1 Community sound Outside FAT therefore Several thousand Usable only under very Usable during parts of the Autonomous use only broadcasting on HF on NINP basis kilometres from the UK restrictive conditions day in short bursts with possible under very Public Correspondence "listen before transmit" restrictive conditions channels protocol 2 Local VHF sound Outside FAT and ECAT <2000 km2 and along the Viable except in south One duplex band is left Viable with limited broadcasting in the 66 to therefore used on a edge of the south coast east corner of Kent unused restrictions but one 2 88 MHz mobile band NINP basis Increases to 26,000 km2 (<2000 km ) and within Directional broadcast duplex band is unused under more stringent 10 - 30 km of the south antenna could be used to NINP conditions. coast minimise emissions into France

3 Digital wide band PMR Within FAT Footnote Digital Coordination Viable with limited with digital TV in Band III (excluding the Republic 700 to 8000 km2 requirements restrictions (200 MHz) of Ireland) and ECAT, Analogue substantially reduced and in line with current 13,000 to 100,000 km2 compared to the current UK / France MOU analogue situation

4 Unrestricted wide band In conformance with FAT 4,500 km2 Unconstrained wide With narrow band in the Viable with limited PMR in the 450 - 470 and ECAT but out of line band assignments put no UK and France the restrictions MHz band with narrow with ECC additional restrictions on coordination/interference band in France Recommendations on UK deployments area increases to 24,000 the introduction of wide But prevents use of km2 band digital PMR preferred frequencies

5 UTRA TDD in spare Outside FAT primary <2000 km2 for nationally UTRA TDD could be With UTRA TDD in the Viable with limited DVB-T channels (500 allocation between 470 - available channels operated anywhere UK and France the restrictions MHz) 790 MHz but within within the DVB-T coordination area is Footnote (excluding coverage area with few 16,000 km2 Belgium and the restrictions on Republic of Ireland) transmitter ERPs But operates as NINP

No. Scenario Regulatory model Coordination / Summary Notes Conclusion Interference area 6 Fixed wireless access in Within FAT but outside Within 60 km of the Irish Special engineering Coordination area is Probably viable in UK 900 MHz TETRA band ECAT and border would make it expensive significantly reduced with significant Harmonisation for digital in NI when only operational restrictions PMR areas are protected 7 Re-farming of GSM In conformity with FAT 900 MHz - 4,500 km2 Minimal restrictions on Constraints are larger for Viable with limited spectrum to UTRA (900 and ECAT but potentially 1800 MHz - ~300 km2 UTRA deployments UTRA to UTRA restrictions MHz & 1800 MHz) out of line with ECC coordination Harmonisation initiatives

8 Terrestrial DAB local Outside FAT and ECAT 26,000 km2 Usable although an One duplex band is left Viable but under radio at 1800 MHz therefore used on a Increases to 41,000 km2 important part of the unused significant restrictions NINP basis under more stringent south east could be Coordination/interference NINP conditions excluded area reduces to a few 1000s km2 if more relaxed conditions are acceptable 9 Part of 1800 MHz band Within FAT and ECAT The majority of Northern Largely unusable in NI Restrictions to protect the Probably usable in UK reallocated to fixed links but disregards Ireland (due to interference from GSM users in RoI are not under severe restrictions harmonisation for digital GSM) except where onerous cellular use protected by topography

10 Portable Wireless DSL in Within FAT and ECAT 35,000 km2 Usable with serious Deployment would be Categorised under the 2010 - 2020 MHz but outside harmonised restrictions on PWDSL very difficult if fixed links limited restrictions as IMT-2000 band allocation to IMT-2000 EIRPs only in ~4000 km2 are operational in France serious restrictions apply (for both PWDSL and only to a very small area UTRA)

No. Scenario Regulatory model Coordination / Summary Notes Conclusion Interference area 11 Use of 2.7 - 2.9 GHz Outside FAT and would Most of the UK Not viable But low power devices, Autonomous use only Aeronautical band for operate on NINP basis such as cordless TV possible under severe fixed links cameras, can share the restrictions spectrum 12 FWA spectrum used for Within FAT and ECAT ~50,000 km2 Usable although EIRPs Narrow beam widths and Viable with limited OB links at 3.5 GHz and direction would be intermittent nature of use restrictions restricted in the south of minimise need for the UK coordination 13 Disregard technical In line with FAT and 100 to 150 km from the No impact on need for The likelihood of UK and Viable with limited standards and channel ECAT but ignores south coast coordination, and little or French links pointing at restrictions plans for terrestrial fixed harmonised standards no need for coordination each other is small services at 32 GHz and channel plans in practice

Table 17.1: Summary of the scenarios investigated.

18. ANNEX A

All modelling in the Autonomy project was completed using ICS Telecom Version 6.84. Terrain and other data needed for this modelling was created and manipulated using ICS Map Server Version 7.45. Further details on these tools can be found at www.atdi.co.uk.

18.1 The Essence of the Tool

The heart of ICS Telecom (and indeed most modelling tools that use statistical models) is the path profile. This is extracted from a linear array of height points representing the terrain (and potentially buildings) and held as a digital terrain model. At each height point a second overlay file provides a statement of the ground usage at that point. This file can be used to describe many aspects of ground usage but in the Autonomy project was used for expression of clutter (water, buildings and trees) and for definition of ground conductivity at HF. Finally a further overlay is used describing a colour at each terrain point. This then allows a map image to be used such that modelled results can be expressed in relation to common features such as coastline and towns.

Once the profile has been extracted and held in memory, various analyses can be conducted. The result is a prediction of the path loss between a given transmitter and any point on the ground at which there might be a receiver. This path loss can be both wanted (from a local service to which the receiver subscribes) or unwanted (from a distant service considered a nuisance if received above a given threshold level). Once wanted and unwanted are predicted they can be related to yield a wanted to unwanted ratio. It is this ratio that forms the basis of interference modelling.

18.2 Path Modelling

Path modelling in ICS Telecom takes two principal forms:

5Empirical where copious data has been collected and are developed into a model where loss can be looked up using graphs or polynomials;

5Physical where past research has developed algorithms which are used together depending on the geometry of the path to give a final predicted value.

These models cover all the characteristics of a path as it lengthens firstly covering distances within the radio horizon where losses are calculated for paths with line of sight, with sub-path diffraction and with diffraction. Then as the length extends, the methods predict trans-horizon loss and ultimately tropospheric losses where a simple diffraction calculation of the Earth bulge would be too pessimistic. The models include terrain clearance angle, radio refractivity, clutter shielding and the use of radio meteorological data.

The modelling methods also include antenna pointing losses using a three-dimensional model of the antenna polar response.

18.2.1 Fading and Stochastic Effects

The prediction of a loss over a path is governed by probability. The loss will vary both temporally and spatially. The mechanisms that cause this variation are modelled in ICS Telecom using a variety of models defining the confidence that a given level will be experienced. It is therefore possible to define a maximum path loss for a high confidence commensurate with a desired high connectivity whilst defining a loss from an unwanted station for a very low confidence commensurate with a nuisance marginally reducing service connection benefit. Both are dealt with in ICS Telecom either in the propagation model or in the margins above median operating level that are calculated case by case.

18.3 Interference Modelling

Once the path loss between a given point and both wanted and unwanted stations are defined by median values and by variances accounting for spatial and temporal change, the values of received signal can be related. The method used to relate these signals depends on the scenario and the technologies involved. The simplest is the use of a C/I or wanted to unwanted ratio. Laboratory tests are used and published to define minimum values of C/I before the unwanted degrades the service benefit below a defined threshold. Once defined this C/I can be used to determine a nuisance field above which the C/I minimum will be breached. This method of modelling is used extensively in the development of Memoranda of Understanding and has been used extensively within the Autonomy Project since it defines areas of exclusion where stations cannot be located else interference will result.

Use of ‘drop in threshold’ (DiT) methods is made where the interferer can be considered as noise, reducing the available carrier to noise ratio. These methods are useful particularly where there are multiple interferers of differing modulation schemes and bandwidths. In this case a maximum threshold impairment is quoted in place of a limit C/I. Locations on the ground where this threshold will be breached can be determined in the same way as C/I breach locations outlined above.

In both C/I and DiT methods aggregation of interfering signals is essential to obtain a view of the total effect of distant transmitters. Throughout the Autonomy Project the interference calculations used, as appropriate, both power sum aggregation (where signals emanate from the same location) and simplified multiplication method (where they come from geographically separated locations).

18.4 Reporting

Throughout the work, reporting has taken two forms:

5Tabular where signals from stations are compared and their propensity to interfere noted;

5Colours on a map overlay where the colours define the severity of degradation pixel by pixel.

Which is used depends on the scenario and the desired output.

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