Sharing between fixed point-to-point links and uncoordinated earth station receivers in 10.7–11.7 GHzDiscussion paperJULY 2019

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Executive summary

Issues for comment

Current national arrangementsOverview 3Spectrum allocations 3Supported services 3Fixed point-to-point links 3

Space-based communications system licensing options 5Requirement to licence earth station receivers 6

Planning and implementation issuesPreliminary ACMA view 7Technical feasibility 7Need for technical restrictions and operational conditions on uncoordinated earth station receivers 8

Implementation issues 9Licensing 9Pricing 9Licence assessment procedures 10

Invitation to commentMaking a submission 11

Appendix A: ARSP extracts

Appendix B: Summary of ARSP footnotes

Appendix C: Technical studyFixed link transmitter 16Transmitter power and EIRP 16Antenna pattern 17

Earth station receiver 19Interference threshold 19

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Contents (Continued)

Antenna pattern 19

Interference analysis 20Antenna gain and required propagation loss 20Propagation models 21

Summary of parameters 22Separation distances 22Discussion of results 22

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Executive summary

The 10.7–11.7 GHz band (the 11 GHz band) is planned and used in Australia for fixed point-to-point links1. The 11 GHz band is one of the most heavily used microwave fixed point-to-point link bands in Australia, with over 15,800 links licensed in the band2. The 11 GHz band is also used by the fixed satellite service (FSS) for earth receive stations. Both fixed point-to-point links and earth station receivers are subject to individual apparatus licensing on a coordinated basis.

The Australian Communications and Media Authority (ACMA) is considering the technical feasibility of arrangements to enable the use of uncoordinated earth station receivers under class licensing arrangements in the 11 GHz band. Currently, there is 1.05 GHz of bandwidth available for such usage in the adjacent band 11.7– 12.75 GHz. If implemented, access to the 11 GHz band would provide an additional 1 GHz of bandwidth for such applications—in total, 2.05 GHz of continuous spectrum.

Providing such access is intended to support the introduction of new satellite services and applications in Australia3 such as high-throughput satellite systems, support satellite-based internet of things, enable low-latency satellite services through low earth orbit non-geostationary orbit (NGSO) systems, and take advantage of technical developments supporting use of earth stations in motion in the fixed satellite service.

This review was included in the ACMA’s Five-year spectrum outlook (FYSO) 2018–22, and the draft FYSO 2018–23. The ACMA is looking to respond to submissions received by Q4 2019 (noting that participation in WRC–19 by both ACMA and industry may impact timing of next steps).

The ACMA’s preliminary view is that it is technically feasible to develop class-licensing arrangements to enable the non-protected use of uncoordinated earth station receivers in the 11 GHz band.

This preliminary view is based on the proviso that no constraints are placed on the future growth of fixed services in the 11 GHz band, given its extensive and growing use for point-to-point services. Therefore, under arrangements where uncoordinated earth station receivers are permitted, they would not be protected from interference—from either current or future fixed point-to-point links, nor would they be considered in future replanning processes for fixed services.

The ACMA seeks comment on the technical feasibility of allowing uncoordinated earth station receivers under class-licensing arrangements to operate in the 11 GHz band, as well as preliminary views on some technical, licensing and pricing issues for related space apparatus licences.

1 A fixed link comprises one transmitting radiocommunications station and one receiving radiocommunications station, each at a fixed location.2 Number of apparatus licences in the 11 GHz band in the ACMA’s Register of Radiocommunications Licences at 1 May 2019.3 As evident in responses from the satellite industry to the ACMA draft FYSO 2019–23.

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Issues for commentThe ACMA invites comments on the issues set out in this discussion paper, as well as comment on the following questions:1. Will the future use of the 11 GHz band by the fixed service be impacted if

arrangements are developed to facilitate the use of uncoordinated earth station receivers in the band?

2. Is it technically feasible for uncoordinated earth station receivers to operate in the interference environment that exists in the 11 GHz band?

3. Is there a need for technical restrictions or conditions on the operation of uncoordinated earth station receivers?

4. What, if any, are the implementation issues for licensing options, pricing and updates to licence assessment procedures?

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Current national arrangementsOverview The 11 GHz band is used in Australia for fixed point-to-point links and FSS earth receive stations. Both services are subject to individual apparatus licensing on a coordinated basis.

Spectrum allocationsAppendix A provides an extract from the Australian Radiofrequency Spectrum Plan 2017 (ARSP) Table of Frequency Band Allocations (ARSP Part 2) for the 11 GHz band and relevant international footnotes (ARSP Part 4). Appendix B provides a summary of the footnotes that apply in each part of these bands.

Supported servicesFixed point-to-point linksArrangements for 11 GHz fixed point-to-point services are described in Radiocommunications Assignment and Licensing Instruction (RALI) FX 3. There are over 15,800 licensed fixed point-to-point links in Australia; their geographical distribution is illustrated in Figure 1. Use of the band has increased significantly over recent years and growth is continuing (see Figure 2). While there are over 200 licensees, the majority of links (over 10,500) are licensed to just two operators: NBN and Optus (see Table 1).

Figure 1: Fixed point-to-point links in the 11 GHz band

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Figure 2: Growth in 11 GHz fixed point-to-point links: 2010–2019

2010 2011 2012 2013 2014 2015 2016 2017 2018 20190

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

Fixed point-to-point links in the 11 GHz band

Year

Num

ber o

f lin

ks

Table 1: 11 GHz fixed link licensees

Licensee* Number of links

NBN Co Limited 8336

Optus Mobile Pty Ltd 2588

Telstra Corporation Limited 882

Vodafone Australia Pty Ltd 610

South Australian Government Radio Network 192

GoldNet Pty Ltd 176

Vertical Telecoms Pty Limited 146

Australia Pacific LNG Pty Limited 140

ElectraNet Pty Ltd 110

Tasmanian Networks Pty Ltd 108

BHP Billiton Iron Ore Pty Ltd 104

Digital Distribution Australia Pty Ltd 104

Aussie Broadband Pty Ltd 78

Ergon Energy Corporation Limited 66

Jettech Networks Pty Ltd 62

BigAir Group Pty Limited 58

ESSO Australia Pty Ltd 58

Field Solutions Group Pty Ltd 56

Western Australia Police 56

The Pilbara Infrastructure Pty Ltd 52

*Licensees with over 50 links

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Earth station receivers Individual receiving earth stations can be apparatus licensed (using the earth receive licence type) in the 11 GHz band on a coordinated basis with fixed point-to-point links. This enables earth station receiver use at discrete locations on a shared, coordinated basis with fixed links. There are currently 44 earth receive licences in the 11 GHz band at eight unique locations; their geographical distribution is illustrated in Figure 3. Uncoordinated earth stations are currently not supported in the 11 GHz band.

Figure 3: Earth station receivers in the 11 GHz band

Space-based communications system licensing optionsUnder the regulatory framework for space-based communications systems, the operation of earth station transmitters and receivers is required to be authorised by a radiocommunications licence. In general, there are two broad options for licensing.

First, operators may obtain an apparatus licence for each of their earth stations individually, with an earth licence for the uplink and an earth receive licence for the downlink, if licensing via the ground segment. This approach allows the earth station to be individually coordinated with other services as required.

Alternatively, in certain bands, operators may obtain a licence for the space segment (that is, transmission and reception from satellites) with a space apparatus licence for the downlink and a space receive apparatus licence for the uplink. Uncoordinated earth stations are then authorised in these bands via the Radiocommunications (Communication with Space Object) Class Licence 2015 (the Communication with Space Object Class Licence). To that end, space segment licensing is only available in those frequency bands contained within this class licence. Under these arrangements,

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the authorised frequency range of the earth station under the class licence is the same as the frequency range of the associated space/space receive apparatus. While devices authorised under class licences are not subject to fees, apparatus licences require payment of licence fees.4 In effect, this means that licensing costs are paid directly by the space/space receive apparatus licensee and not individual users whose use is authorised under the class licence.

More details on these arrangements and ACMA licensing assessment procedures can be found in the ACMA’s business operating procedures for submission and processing of applications for:> earth and earth receive apparatus licences for fixed earth stations > space and space receive apparatus licences .

While the adjacent 11.7–12.75 GHz band is currently included in the Communication with Space Object Class Licence supporting the class-licensed operation of uncoordinated earth station receivers, the 11 GHz band is not.

Requirement to licence earth station receivers Section 46 of the Radiocommunications Act 1992 (the Act) requires that a person must not operate a radiocommunications devices otherwise than as authorised by a spectrum, apparatus or class licence.

Under section 7 of the Act, radiocommunications devices are radiocommunications transmitters and radiocommunications receivers of a kind specified by the ACMA. In the Radiocommunications (Specified Radiocommunications Receivers and Types of Transmitter Licences and Receiver Licences) Determination 2014, an earth receive station is specified as a radiocommunications receiver and is therefore a radiocommunications device. For this reason, all earth station receivers are required to be licensed and this includes uncoordinated earth station receivers in the 11 GHz band.

4 For details refer to ACMA’s apparatus licence fee information.

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Planning and implementation issuesUncoordinated earth receive station use would not pose an interference risk to fixed point-to-point links in the 11 GHz band. However, a relevant consideration is under what conditions earth station receivers could operate on an uncoordinated basis with an acceptable probability of receiving interference from 11 GHz band point-to-point transmitters. This is consistent with the ACMA generally not establishing planning arrangements unless they are considered fit for purpose for the intended use. The technical feasibility of such usage and potential implementation issues are explored to aid consideration of possible arrangements.

Preliminary ACMA view Consistent with the objective of maximising the overall public benefit derived from use of the spectrum through shared access when possible, the ACMA has formed the preliminary view that uncoordinated earth stations could be supported in the 11 GHz band on a non-protected basis.

This preliminary view is premised on the understanding that development of arrangements to allow the use of uncoordinated earth station receivers in the 11 GHz band would not:> create constraints on the use of the band by the fixed service either now or in the

future> constrain any future replanning to support fixed services.

As evidenced by the significant and growing use of this band, the 11 GHz band is and will continue to be a key resource for fixed point-to-point services.

1. Will the future use of the 11 GHz band by the fixed service be impacted if arrangements are developed to facilitate the use of uncoordinated earth station receivers in the band?

Technical feasibilityIn considering whether changes to planning arrangements can be made, the ACMA considers the technical feasibility of those changes including whether they are generally fit for purpose for the intended use.

Appendix C details a basic technical study on the likelihood of interference to an earth station receiver from a fixed point-to-point link in the 11 GHz band. The approach of the technical study is to calculate the co-channel separation distances as the antenna discrimination angles at the earth station receiver and fixed link transmitter vary (where antenna discrimination angle considers both azimuth and elevation angle). Refer to Appendix C for a full description of the technical study.

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The study is intended to be indicative only and uses simplistic modelling. For example, propagation modelling is based on free space loss with diffraction over a spherical earth for when distances are beyond line of sight, no additional clutter losses are included. As such it is likely that in some cases the resulting distance overestimates the required separation distances. It is up to potential operators of earth station receivers to determine the relevance of the technical study to deployment models they are considering. Under the assumptions of the study, separation distances vary from in the order of 50 km with an angular separation5 of 10 degrees to a minimum of 2 km with maximum antenna discrimination.

The results illustrate that the operation of uncoordinated earth station receivers in the 11 GHz band could be feasible with a modest probability of interference to earth receive stations.

To that end, comment is sought on whether it is feasible to operate in such an interference environment in the long term, noting that the planning intention would be not to compromise the future use of the 11 GHz band by the fixed service.

Need for technical restrictions and operational conditions on uncoordinated earth station receivers While the probability of interference to uncoordinated earth receive stations is expected to be modest, to further mitigate the potential for interference from current and future fixed link transmitters, technical and operational measures on the earth station receiver could be contemplated. These could include the ability to use an alternative channel, avoiding operation at low elevation angles and/or minimum antenna diameter requirements.

For example, should technical conditions (such as antenna size) be used to distinguish the types of earth stations that could be authorised on an uncoordinated basis under the Communication with Space Object Class Licence from those that should be individually coordinated and apparatus licensed (as is currently required).

Given the role that a gateway earth station receiver plays in a satellite network, there is likely a compelling operational case that they be individually licensed and coordinated, and therefore protected. In such a scenario, it is the responsibility of the individual user, not the ACMA, to choose whether to take out an individually coordinated and protected apparatus licence as required, recognising that if not coordinated then no interference protection is afforded.

Given the interference environment in the 11 GHz band, it is expected that satellite service providers would have measures to address the possibility of interference from fixed point-to-point services. For example, such measures could include measures to ensure that satellite systems operating in the 11 GHz band with uncoordinated earth station receivers are not fully reliant on specific frequencies within the 11 GHz band to maintain communications. That is, space station transmitters in the satellite system and associated earth station receivers would have the ability to switch to other frequencies to ensure continued communication in the event of interference from fixed services to an earth station receiver in a given area, for example, by switching to another channel in the 11 GHz band not being used by fixed point to-point services in the area of operation, or to the 11.7–12.75 GHz band.

Such a measure could be encouraged by only authorising use of the 11 GHz band where the user also holds an apparatus licence to authorise use in another frequency band. Alternatively, this could be noted as a risk of operating in the band and a

5 That is, the angular separation between main lobe of the earth station receive and fixed link transmitter antennas. Considers both discrimination in elevation and azimuth.

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licensee could choose to rely on the 11 GHz band and accept any consequences of interference.

Further approaches that could be employed in addition to or instead of the above measure could be to limit authorisation of uncoordinated earth station receivers to those operating above a minimum elevation angle or with a minimum antenna size. Both approaches would reduce the susceptibility of earth station receivers to point-to-point interference.

2. Is it technically feasible for uncoordinated earth station receivers to operate in the interference environment that exists in the 11 GHz band?

3. Is there a need for technical restrictions or conditions on the operation of uncoordinated earth station receivers?

Implementation issuesSeveral implementation issues need to be considered should the development of class-licensing arrangements for uncoordinated earth station receivers be pursued. These issues are interrelated because how licensing is approached will impact on related space apparatus licence pricing considerations and changes required to space apparatus licence assessment procedures. Also, if it is determined that there is a need for technical restrictions and conditions on uncoordinated earth station receivers, how these requirements are implemented may influence approaches to licensing and apparatus licence assessment procedures.

The discussion below provides an outline of implications for licensing, pricing and assessment procedures for space-based communications systems.

The ACMA is seeking preliminary views on these issues with the intention of providing further opportunity for comment if this proposal is pursued.

4. What, if any, are the implementation issues for licensing options, pricing and updates to licence assessment procedures?

Licensing Supporting the operation of uncoordinated earth stations in the 11 GHz band will require an amendment to the Communication with Space Object Class Licence to include the 10.7–11.7 GHz band as an authorised frequency range for reception.

Where there is a need for technical restrictions and conditions on the operation of uncoordinated earth station receivers, such requirements can also be included in the Communication with Space Object Class Licence.

The ACMA seeks comment on whether uncoordinated earth station receivers should be supported by the Communication with Space Object Class Licence, combined with a space apparatus licence, by amending the class licence to include the 11 GHz band as an authorised frequency range for reception.

Pricing The interference environment for uncoordinated earth station receivers in the 11 GHz band is different to that of the 11.7–12.75 GHz band. Uncoordinated earth station receivers in 11 GHz will be expected to accept interference from fixed services in the band and new fixed point-to-point services will be allowed without consideration of uncoordinated earth station receiver use of the band.

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In comparison, the 11.7–12.75 GHz band is specifically planned for satellite services to the exclusion of other services. That is, the planning arrangements that are in place to support uncoordinated earth station receiver use in the 11.7–12.75 GHz band create spectrum denial for other services. By contrast, use of the 11 GHz band by uncoordinated, unprotected earth station receivers would not result in any spectrum denial, therefore a case can be made for reviewing licence fees that apply to the associated space apparatus licence.

Pricing considerations will involve:> Reviewing apparatus licence fees for space and space receive licences. If this is to

occur, it may be considered in the ACMA’s broader work on pricing in implementing the recommendations of the Government’s Spectrum Pricing Review. What priority should be provided to reviewing these taxes as part of implementing the Spectrum Pricing Review?

> Considering whether any amendment to the Communication with Space Object Class Licence could be undertaken in a way that no licence fees are applicable for the 11 GHz band, provided use of the band 11.7–12.75 GHz is authorised.

Licence assessment procedures As outlined previously, a space/space receive apparatus licence is required for operation under the Communication with Space Object Class Licence to be authorised. When considering applications for space/space receive apparatus licences, the feasibility (technical compatibility) of a new satellite system is assessed in accordance with the requirements of the ACMA’s business operating procedure for submission and processing of applications for space and space receive apparatus licences.

A key element of these procedures is assessing the progress of the associated satellite network in the International Telecommunication Union (ITU) coordination process, including its ITU regulatory status and whether the ITU registration details of the satellite network are consistent with the technical characteristics of the proposed satellite services. Inclusion of the 10.7–11.7 GHz band in the Communication with Space Object Class Licence will require a review of the business operating procedures to examine whether any additional criteria are required when assessing applications for associated space apparatus licences.

If the Communication with Space Object Class Licence is proposed to be amended to authorise reception of transmissions in the 11 GHz band, as part of that consultation on a draft class licence the ACMA would also consult on any updates required to its procedures for submission and processing of applications for space and space receive apparatus licences.

At this stage the scope of updates the ACMA can envisage are:> Procedures to address assessment of compliance with any technical restrictions or

conditions imposed on uncoordinated earth station receivers.> Consideration of the arrangements for earth stations in motion in 11.7–12.75 GHz

to include 10.7–11.7 GHz. These arrangements are expect to be similar to those considered in IFC 6/2019 Earth stations in motion in Ku band6.

> Revisions of applicability of existing special conditions and advisory notes.> Including a requirement that space apparatus licensees provide written

confirmation that they accept that operation of uncoordinated earth station receivers would be on the basis that no protection is afforded from interference—from either current or future fixed links, and that operation is not to constrain the

6 The ACMA expects the outcome of the IFC 6/2019 consultation to be completed by Q3 2019.

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future growth of fixed services in this band nor would they be considered in future replanning processes for fixed services.

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Invitation to commentMaking a submissionThe ACMA invites comments on the issues set out in this discussion paper.

> Online submissions can be made via the comment function or by uploading a document. Submissions in Microsoft Word or Rich Text Format are preferred.

> Submissions by post can be sent to:

The ManagerSpectrum Engineering and Space SectionAustralian Communications and Media AuthorityPO Box 78Belconnen ACT 2616

The closing date for submissions is COB, Monday 19 August 2019.

Consultation enquiries can be emailed to freqplan@acma.gov.au.

Publication of submissionsThe ACMA publishes submissions on our website, including personal information (such as names and contact details), except for information that you have claimed (and we have accepted) is confidential.

Confidential information will not be published or otherwise released unless required or authorised by law.

PrivacyPrivacy and consultation provides information about the ACMA’s collection of personal information during consultation and how we handle that information.

Information on the Privacy Act 1988 and the ACMA’s privacy policy (including how to access or correct personal information, how to make a privacy complaint and how we will deal with the complaint) is available at acma.gov.au/privacypolicy.

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Appendix A: ARSP extractsTable 2 shows an extract from the ARSP for the 10.7–11.7 GHz band. The text of the relevant footnotes is included in Table 3, which are summarised at Appendix B.

Table 2: Extract from the ARSP for the 10.7–11.7 GHz band

Column 1: ITU Radio Regulations Table of Allocations Column 2:

Region 1 Region 2 Region 3 Australian Table of Allocations

10.7 – 10.95 FIXED FIXED–SATELLITE (space-to-Earth)

441 (Earth-to-space) 484 MOBILE except aeronautical mobile

10.7 – 10.95 FIXED FIXED–SATELLITE (space-to-Earth) 441 MOBILE except aeronautical mobile

10.7 – 10.95 FIXED FIXED–SATELLITE (space-to-Earth)

441 MOBILE except aeronautical mobile

10.95 – 11.2 FIXED FIXED–SATELLITE (space-to-Earth)

484A 484B (Earth-to-space) 484 MOBILE except aeronautical mobile

10.95 – 11.2 FIXED FIXED–SATELLITE (space-to-Earth) 484A 484B MOBILE except aeronautical mobile

10.95 – 11.2 FIXED FIXED–SATELLITE (space-to-Earth)

484A 484B MOBILE except aeronautical mobile

11.2 – 11.45 FIXED FIXED–SATELLITE (space-to-Earth)

441 (Earth-to-space) 484 MOBILE except aeronautical mobile

11.2 – 11.45 FIXED FIXED–SATELLITE (space-to-Earth) 441 MOBILE except aeronautical mobile

11.2 – 11.45 FIXED FIXED–SATELLITE (space-to-Earth)

441 MOBILE except aeronautical mobile

11.45 – 11.7 FIXED FIXED–SATELLITE (space-to-Earth)

484A 484B (Earth-to-space) 484 MOBILE except aeronautical mobile

11.45 – 11.7 FIXED FIXED–SATELLITE (space-to-Earth) 484A 484B MOBILE except aeronautical mobile

11.45 – 11.7 FIXED FIXED–SATELLITE (space-to-Earth)

484A 484B MOBILE except aeronautical mobile

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Table 3: Extract from the ARSP—footnotes

Footnote Text

441 The use of the bands 4 500–4 800 MHz (space-to-Earth), 6 725–7 025 MHz (Earth-to-space) by the fixed–satellite service shall be in accordance with the provisions of Appendix 30B. The use of the bands 10.7–10.95 GHz (space-to-Earth), 11.2–11.45 GHz (space-to-Earth) and 12.75–13.25 GHz (Earth-to-space) by geostationary-satellite systems in the fixed–satellite service shall be in accordance with the provisions of Appendix 30B. The use of the bands 10.7–10.95 GHz (space-to-Earth), 11.2–11.45 GHz (space-to-Earth) and 12.75–13.25 GHz (Earth-to-space) by a non-geostationary-satellite system in the fixed–satellite service is subject to application of the provisions of No. 9.12 for coordination with other non-geostationary-satellite systems in the fixed–satellite service. Non-geostationary-satellite systems in the fixed–satellite service shall not claim protection from geostationary-satellite networks in the fixed–satellite service operating in accordance with the Radio Regulations, irrespective of the dates of receipt by the Bureau of the complete coordination or notification information, as appropriate, for the non-geostationary-satellite systems in the fixed–satellite service and of the complete coordination or notification information, as appropriate, for the geostationary-satellite networks, and No. 43A does not apply. Non-geostationary-satellite systems in the fixed–satellite service in the above bands shall be operated in such a way that any unacceptable interference that may occur during their operation shall be rapidly eliminated.     (WRC-2000)

484 In Region 1, the use of the band 10.7–11.7 GHz by the fixed–satellite service (Earth-to-space) is limited to feeder links for the broadcasting–satellite service.

484A The use of the bands 10.95–11.2 GHz (space-to-Earth), 11.45–11.7 GHz (space-to-Earth), 11.7–12.2 GHz (space-to-Earth) in Region 2, 12.2–12.75 GHz (space-to-Earth) in Region 3, 12.5–12.75 GHz (space-to-Earth) in Region 1, 13.75–14.5 GHz (Earth-to-space), 17.8–18.6 GHz (space-to-Earth), 19.7–20.2 GHz (space-to-Earth), 27.5–28.6 GHz (Earth-to-space), 29.5–30 GHz (Earth-to-space) by a non-geostationary-satellite system in the fixed–satellite service is subject to application of the provisions of No. 9.12 for coordination with other non-geostationary-satellite systems in the fixed–satellite service. Non-geostationary-satellite systems in the fixed–satellite service shall not claim protection from geostationary-satellite networks in the fixed–satellite service operating in accordance with the Radio Regulations, irrespective of the dates of receipt by the Bureau of the complete coordination or notification information, as appropriate, for the non-geostationary-satellite systems in the fixed–satellite service and of the complete coordination or notification information, as appropriate, for the geostationary-satellite networks, and No. 43A does not apply. Non-geostationary-satellite systems in the fixed–satellite service in the above bands shall be operated in such a way that any unacceptable interference that may occur during their operation shall be rapidly eliminated.     (WRC-2000)

484B Resolution 155 (WRC-15) shall apply.     (WRC-15)

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Appendix B: Summary of ARSP footnotes

Comms direction

Frequency band (GHz)

Service ITU footnotes applicable

Summary of footnotes

Space to Earth:

10.7–10.95 FSS 441 GSO in accordance with Appendix 30BNGSO no interference to, no protection from GSONGSO coordination with NGSO subject to No. 9.12

10.95–11.2 FSS 484A 484B NGSO no interference to, no protection from GSO NGSO coordination with NGSO subject to No. 9.12Resolution 155 (WRC-15) shall apply

11.2–11.45 FSS 441 GSO in accordance with Appendix 30BNGSO no interference to, no protection from GSO

11.45–11.7 FSS 484A 484B NGSO no interference to, no protection from GSO NGSO coordination with NGSO subject to No. 9.12Resolution 155 (WRC-15) shall apply

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Appendix C: Technical studyThe interference scenario between a fixed point-to-point link transmitter station (fixed link transmitter) and an earth station receiver in the 11 GHz band is shown in Figure 4 below.

Figure 4: Illustration of technical study

As shown in Figure 4, the earth station receives a wanted signal from the satellite station transmitter (green line) and an unwanted signal from the fixed point-to-point transmitter (red line).

The angles illustrated in Figure 4 are:

δ: Receive antenna discrimination angle, the angular separation between main lobe of the earth station receive antenna (pointing towards the satellite station transmitter) and the angle towards the fixed link transmitter station antenna.

θ: Transmit antenna discrimination angle, the angular separation between the main lobe of the fixed link transmitter station antenna (pointing towards the fixed link receiver antenna) and the angle toward the earth station receiver antenna.

Φ: Earth station antenna angle, the elevation angle with respect to the horizon.

Note: Angular discrimination considers both azimuth and elevation.

The approach of the technical study is to calculate the co-channel separation distances, as the antenna discrimination angles at the earth station receiver and fixed link transmitter vary.

The study uses the free space loss/spherical earth diffraction propagation model with notional parameters for both the fixed link transmitter and earth station receiver station. Those parameters have been determined from analysis of technical records in the ACMA’s Register of Radiocommunications Licences and ITU documents.

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Fixed link transmitterTransmitter power and EIRP There were 15,814 point-to-point transmitters licensed in the 11 GHz band as at 1 May 2019. Figure 5 shows a box and whisker plot7 of the radiated power (EIRP (dBm/MHz) for these transmitters. Figure 6 shows transmitter power distribution.

The maximum fixed link radiated power (EIRP) in the band is 64.7 dBm/MHz. The 99th percentile of EIRP values is 58.0 dBm/MHz; the 75th percentile of EIRP values is 50.4 dBm/MHz; the median is 47.4 dBm/MHz; the 25th percentile of EIRP values is 44.4 dBm/MHz; and the 1st percentile of EIRP values is 36.8 dBm/MHz.

For interference assessment purposes an EIRP of 50 dBm/MHz is assumed (worst case scenario when no antenna discrimination). For off-axis assessments, considering the distribution of Figure 6, a transmitter power of 10 dBm/MHz is used with antenna gain as per the antenna radiated pattern (see next section). These values are considered typical scenarios, rather than worst case assumptions.

Figure 5: Box and whisker plot, showing the distribution of EIRP values for fixed link transmitters in the 11GHz band.

7 A graphic way to display the median, quartiles, and extremes of a data set on a number line to show the distribution of the data.

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Figure 6: Transmitter power distribution for 11 GHz fixed point-to-point links.

0-2 2-4 4-6 6-8 8-10 10-12 12-14 14-16 16-18 18+0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

Transmiter power distribution (dBm/MHz)

Transmitter power (dBm/MHz)

Coun

t

Antenna patternThe distribution of fixed link antenna size is shown in Figure 7. For interference assessment purposes a 1.2m antenna is assumed with the antenna radiation pattern taken from Recommendation ITU-R F.699 (recommends 2.2.1 for antennas with D/λ < 100, for a 11 GHz 1.2m antenna D/λ is 42.8). Maximum antenna gain is taken to be 40 dBi based on analysis of existing fixed links being radiated power (50 dBm/MHz) minus transmitter power (10 dBm/MHz). In comparison, using F.699 the maximum antenna gain is 40.33 dBi. In practice, except for maximum antenna gain which is only required to determine worst case separation distances, the choice of antenna size has only a minor impact on the resulting separation distances. As with an angular discrimination of 2 degrees or greater the radiation pattern is independent of maximum antenna gain. Figure 8 illustrates how antenna radiation pattern varies with antenna size.

The equations for the radiation pattern are:

G (φ )=Gmax−2.5×10−3(Dλ φ)2

for 0<φ<φm

G (φ )=G1 for φm≤φ<100 λD

G (φ )=52−10 log Dλ−25 logφ for 100 λ

D≤φ<48 °

G (φ )=10−10 log Dλ

for 48 ° ≤φ<180 °

Where ϕm=20 λD √Gmax−G1 degrees

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Recommends 3 of F.699 provides the following approximation for maximum antenna gain, where only the ratio D/ is known, as:

Gmax≈20 log Dλ

+7.7

Figure 7: Fixed link antenna sizes

0 0.6 0.8 0.9 1 1.2 1.8 2.4 3 3.70

500

1000

1500

2000

2500

3000

3500

4000

4500

Fixed link antenna sizes

Antenna size (m)

Coun

t

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Figure 8: Comparison of antenna radiation patterns for different antenna sizes

0 5 10 15 20 25 30 35 40 45 50

-20

-10

0

10

20

30

40

50

Fixed link antenna radiation patterns

0.6m 0.9m 1.2m 1.8m

Off-axis angle (degrees)

Gain

(dBi

)

Earth station receiverParameters for uncoordinated earth station receivers have been determined with reference to ITU Radio Regulations and ITU reference radiation patterns.

Interference thresholdA notional interference threshold has been determined by applying the approach used in the update8 to RALI MS 44 “Frequency coordination procedures for the earth station protection zones” which for 11 GHz specifies -154 dBW/MHz or -124 dBm/MHz for 20% of the time.

Antenna patternA notional earth station receive antenna pattern has been derived using ITU Recommendation ITU-R S.465-6 ‘Reference radiation pattern of earth station antennas in the fixed-satellite service for use in coordination and interference assessment in the frequency range from 2 to 31 GHz’.

The radiated pattern of S.465 is specified as:

G=32−25 log φ dBi for φmin≤φ<48 °

G=−10 dBi for 48 ° ≤φ<180°

where:

8 Refer IFC 46/2018 Proposed updates to RALI MS 44

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φmin=1 or 100 λD

degrees (whichever is the greater) for D/ ≥ 50.

φmin=2 or 114 (Dλ )−1.09

degrees (whichever is the greater) for D/ < 50

For the purposes for this study, to determine a worse case separation distance (occurs when fixed transmitter and earth station receiver are directly pointing at each other—an unlikely scenario), main lobe antenna gain is assumed to be 40 dBi (based on 1.2m diameter). In all other scenarios (with an angular discrimination of 2 degrees or greater) the radiation pattern is independent of maximum antenna gain. The radiation pattern is illustrated in Figure 9.

Figure 9: Earth station receiver antenna radiation pattern

0 10 20 30 40 50 60 70 80 90 100

-15

-10

-5

0

5

10

15

20

25

30

Off-axis angle (degrees)

Gai

n (d

Bi)

Interference analysisUnwanted received power can be expressed as:

Pr=Pt+Gt+Gr−LpAlternatively, when rearranged:

Lp=Pt+Gt+Gr−Pr

Where:Pr : unwanted received power at the input to the receiver (-114 dBW/MHz);Pt : transmitter power (10 dBm/MHz);Gt : gain of the fixed link transmitting antenna with a transmit antenna discrimination

angle of θ (dBi);Lp : propagation loss between the transmit and receive antennas (dB);Gr : gain of the earth station receiving antenna with a receive antenna discrimination

angle of δ (dBi);

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Where (with reference to Figure 5):

δ: Receive antenna discrimination angle, the angular separation between main lobe of the earth station receive antenna (pointing towards the satellite station transmitter) and the angle towards the fixed link transmitter station antenna.

θ: Transmit antenna discrimination angle, the angular separation between the main lobe of the fixed link transmitter station antenna (pointing towards the fixed link receiver antenna) and the angle toward the earth station receiver antenna.

Note: angular discrimination considers both azimuth and elevation

Antenna gain and required propagation lossFrom the antenna radiation patterns, antenna gain (Gt and Gr) can be calculated for various combinations of earth station receive antenna and fixed link transmitter antenna discrimination angles (Table 4). With these values the required propagation loss (Table 5) can be calculated. The required propagation loss varies from 204 dB in the worst case with no antenna discrimination, to 107 dB for maximum antenna discrimination.

Propagation modelsFree space (Recommendation ITU-R P.525-3, ‘Calculation of free-space attenuation’) and diffraction over a spherical earth (ITU Recommendation ITU-R P.526–14, section 3.1.1.2) when beyond line of sight. From P.526, line of sight distance is given by:

d loss=√2ae (√h1+√h2 )

For this study, the effective height of the fixed link is assumed to be 50m (modelling a fixed link on a hill) and earth station receiver antenna height 10m (modelling an antenna mounted on a building roof). Thus, the distance when beyond line of sight is 42 km.

Table 4: Earth station receiver and fixed link transmitter antenna gain by discrimination angle

Fixed link transmitter antenna discrimination (degrees)

Ear

th s

tatio

n re

ceiv

er a

nten

na

disc

rimin

atio

n (d

egre

es)

0 2 10 18 26 34 42 50 90

0 80 67 50 44 40 37 35 33 33

2 65 51 35 29 25 22 19 18 18

10 47 34 17 11 7 4 2 0 0

18 41 27 11 5 1 -2 -4 -6 -6

26 37 23 7 1 -3 -6 -8 -10 -10

34 34 20 4 -2 -6 -9 -11 -13 -13

42 32 18 2 -4 -8 -11 -14 -15 -15

50 30 17 0 -6 -10 -13 -15 -17 -17

90 30 17 0 -6 -10 -13 -15 -17 -17

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Table 5: Required propagation loss by discrimination angle

Fixed link transmitter antenna discrimination (degrees)

Ear

th s

tatio

n re

ceiv

er a

nten

na

disc

rimin

atio

n (d

egre

es)

0 2 10 18 26 34 42 50 90

0 204 191 174 168 164 161 159 157 157

2 189 175 159 153 149 146 143 142 142

10 171 158 141 135 131 128 126 124 124

18 165 151 135 129 125 122 120 118 118

26 161 147 131 125 121 118 116 114 114

34 158 144 128 122 118 115 113 111 111

42 156 142 126 120 116 113 110 109 109

50 154 141 124 118 114 111 109 107 107

90 154 141 124 118 114 111 109 107 107

Summary of parametersIn summary the following parameters have been used:

Fixed link transmitterRadiated power (main lobe): 50 dBm/MHz EIRP Transmitter power: 10 dBm/MHz Antenna size: 1.2 m, Maximum antenna gain: 40 dBiAntenna pattern: ITU-R Rec F. 699 (Recommends 2.2.1)Antenna height: 50 m

Earth station receiverInterference threshold: -124 dBm/MHzAntenna size: 1.2 m, Maximum antenna gain: 40 dBi Antenna pattern: ITU-R Rec F. 465 (Recommends 2)Antenna height: 10 m

Propagation:Frequency: 10.7 GHzPropagation models: ITU-R P.525, ITU-R P.526

Separation distancesSeparation distances from various discrimination angles are listed in Table 6. These distances are calculated using free space propagation and diffraction over a spherical earth (when beyond line of sight) in effect median (50% of the time) propagation models. Different reliability requirements and different equipment performances assumptions will result in different distances. It is up to an operator to determine the relevance of the assessment to intended operation.

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Table 6: Co-channel separation distance by antenna discrimination angle*

Fixed link transmitter antenna discrimination (degrees)

Ear

th s

tatio

n re

ceiv

er a

nten

na

disc

rimin

atio

n (d

egre

es)

0 2 10 18 26 34 42 50 90

0 67.3 61.0 53.4 50.5 48.6 47.3 46.2 45.6 45.6

2 60.0 53.8 46.2 43.3 41.5 40.2 39.1 38.5 38.5

10 52.0 45.7 38.2 35.3 24.3 17.4 13.4 11.4 11.4

18 49.0 42.8 35.3 18.5 11.7 8.4 6.4 5.4 5.4

26 47.2 40.9 24.3 11.7 7.4 5.3 4.0 3.4 3.4

34 45.8 39.6 17.4 8.4 5.3 3.8 2.9 2.5 2.5

42 44.8 38.6 13.4 6.4 4.0 2.9 2.2 1.9 1.9

50 44.1 37.9 11.4 5.4 3.4 2.5 1.9 1.6 1.6

90 44.1 37.9 11.4 5.4 3.4 2.5 1.9 1.6 1.6

*Grey shaded distances indicate beyond line of sight

Discussion of resultsThe study is intended to be indicative only; it is up to potential operators of earth station receivers to determine the relevance of the study to deployment models they are considering. Under the simplified assumptions of the study, separation distances can be as much as 67 km when there is no angular discrimination9. Distances drop to around 50 km when there is an angular separation of 10 degrees (of either the earth station receiver antenna or fixed link transmitter antenna), and to a minimum of less than 2 km with maximum antenna discrimination.

In practice, unless an earth station is pointing at a low angle above the horizon and/or it is located on or near the path of a fixed link, the required separation distances will be towards the lower end of this range. These distances would reduce further if clutter (which is not assumed in this study) exists between the point-to-point interferer and the earth station receiver.

The results illustrate that the operation of uncoordinated earth station receivers in the 11 GHz band could be feasible. To mitigate the potential for interference from current and future fixed link transmitters, technical measures such as the ability to use an alternative channel or avoiding operation at low elevation angles would seem to be desirable and may be necessary in areas of high fixed link use.

9 That is, the angular separation between main lobe of the earth station receiver and fixed link transmitter antennas.

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