Inmarsat response to the Ofcom Consultation Document

New Spectrum for Audio PMSE

18 December 2015

1 Introduction

In this response, Inmarsat provides its comments regarding the possible introduction of audio PMSE devices in the band 1525-1559 MHz. Inmarsat is very concerned by this proposal, as we believe that the operation of PMSE devices in this band will lead to harmful interference to our services for reasons explained below.

We therefore oppose the introduction of PMSE devices in this band as suggested by Ofcom but we support Ofcom’s proposal to allow audio PMSE access to the band 960-1164 MHz as an alternative to the band 1525-1559 MHz.

2 Use of the band 1525-1559 MHz by Inmarsat and other MSS operators

The band 1525-1559 MHz is globally allocated to the mobile-satellite service (MSS) for downlinks. It has been used by Inmarsat satellites since the early 1990s. We currently have a fleet of nine geostationary satellites operating in this band, which together cover almost the entire Earth surface, and additional future Inmarsat satellites are also planned to operate in this band.

Compared to some other, higher frequency bands, the L-band spectrum has desirable qualities, for example having negligible loss from rain or other atmospheric effects.

The band is used for a wide range of mobile earth stations (MESs) and for a range of different service capabilities. A non-exhaustive overview of the range of services available is given in the following table.

Maritime

Inmarsat-C Inmarsat C is two-way store and forward communication system that can handle data and messages up to 32kb in length. Inmarsat-C is one element of the GMDSS.

Fleet-77

Inmarsat Fleet 77 offers voice and the choice of mobile ISDN up to 64kbps or an always-on Mobile Packet Data Services (MPDS) for cost-effective, virtually global communications. Fleet 77 also meets the distress and safety specifications of the Global Maritime Distress and Safety System (GMDSS) for voice communication. Distress voice calls made on Fleet 77 are routed through a Land Earth Station to a Maritime Rescue Co-ordination Centre (MRCC).

Fleetbroadband A range of terminals and services for a wide range of

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maritime requirements. Provides voice and IP data, up to 432 kbps.

Air

Classic Aero Voice and data communications, up to 10.5 kbps. Complies with ICAO standards and is approved for Air Traffic Services (ATS) use throughout the world

SwiftBroadband Voice and IP data up to 432 kbps. Used for crew and passenger communications. Increasing being used for in-flight connectivity for passengers. Safety services over SwiftBroadband are being introduced.

Land

IsatDataPro (IDP)

A range of terminals for store and forward messaging, used in fixed and mobile locations, for M2M applications

IsatPhone Pro Handheld mobile terminals for voice, SMS and low datarate connectivity.

BGAN A range of small portable terminals, for voice and IP data, with datarates up to 492 kbps.

All of the above terminals and services, and other Inmarsat services not described above, operate in the band 1525-1559 MHz1 in the UK and other locations around the world. There are other MSS operators which operate in the same frequency bands, some of which also provide services to the UK.

The maritime services provided by Inmarsat may operate from ships around the coastline of the UK and also on the larger inland waterways. The aeronautical services provided by Inmarsat are used on the majority of large passenger aircraft when in flight over the oceans and over terrestrial airspace for tracking and for ‘FANS accommodation’ under the European Commission Datalink Implementation Rule2. The terminals are also used when the aircraft is on the ground, in some cases so that safety-critical equipment can be tested before take-off.

The land services provided by Inmarsat are used by a variety of user groups, including enterprise users, military users, and the emergency services. They may be used at any location in the UK, including rural and urban areas.

An area of high growth is for machine-to-machine (M2M) applications and Inmarsat provides a range of services and terminals to meet the range of user needs. Some of the applications which use Inmarsat M2M solutions are described below.

1. Backhaul connectivity for critical data: BGAN M2M offers higher reliability than traditional cellular providers for the backhaul of mission critical machine data for enterprise customers and for the Internet of Things (IoT).

2. Point of Sale Solutions : BGAN M2M is widely used as the primary connectivity solution for critical point of sale systems such as information kiosks and ATMs

3. Out of band Management: Out-of-Band Management from Inmarsat uses BGAN M2M to restore operations for traditional communications equipment at the site when the primary network link is down. IDP is widely used within city areas to provide a low cost, satellite based Out-of-Band Management solution to enable remote management of equipment.

1 excluding the band 1544-1545 MHz, which is used by Cospas-Sarsat 2 Data Link Services Implementing Rule (DLS-IR) was adopted on 16 January 2009 by the European Commission and published as EC Reg. No. 29/2009

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4. Backup Connectivity: Both BGAN and IDP have hybrid variants, which can operate across both cellular and satellite networks. The Cobham E540 M2M terminal comes integrated with both a 3G modem as well as a BGAN modem. The terminal automatically routes its data over a satellite network in the event of congestion or outage in the cellular network. Due to its dual mode capabilities and small form factor, it is ideal for use within heavily built city areas. Similarly, the IDP 782 terminal from Skywave supports both satellite and cellular connectivity for mobile applications

5. Vehicular BGAN Services: Mobile BGAN fulfils the critical communications requirements around, two-way interactive voice and data communications for NGOs, governmental and commercial organisations for emergency services such as fire and ambulance services.

6. Fleet Management & Asset Tracking: The IDP service finds increasing usage in the fleet and telematics management sector. Combined with sensor and telematics alerts, companies are able to track usage, reduce maintenance and fuel costs. Reliability and availability of this service is key to ensuring security and safety of both drivers and their cargo.

It is notable that some of the applications are based on the use of satellite terminals even in areas where there is terrestrial mobile coverage.

It is important to highlight the services provided by Inmarsat include critical safety services for ships and aircraft. In the case of maritime safety, the Inmarsat safety services ensure that ships can meet their requirements under the International Convention for the Safety of Life at Sea (SOLAS). The frequencies for which priority in coordination is given to the GMDSS in the Radio Regulations include the band 1530-1544 MHz (see RR No. 5.353A), which is part of the MSS band examined by Ofcom. In the case of aeronautical safety services, these have traditionally been limited to the part of the L-band MSS spectrum where priority is given to the AMS(R)S in coordination, i.e. the band 1545-1555 MHz (see RR No. 5.357A). However, recent work undertaken by ICAO has now permitted the use of AMS(R)S safety services in the full band of 1525-1559 MHz, and operational evaluation of the SwiftBroadband Safety services in this larger band are currently taking place on commercial air transport aircraft in the Pacific (flight evaluation in the North Atlantic airspace will begin in Q1 2016).

The MSS services which are not GMDSS or AMS(R)S are in any case often used for critical activities or high social value, such as by emergency services in remote locations, and to support the transportation industry.

Considering all the above elements, it is apparent that any part of the band 1525-1559 MHz may be used by safety related services and other high value services, and so it is necessary for all spectrum regulators, including Ofcom, to ensure that harmful interference is not caused to those users. Furthermore, it is not practicable to establish areas where satellite terminals would not operate, including urban areas. In line with current MSS operations, it should therefore be assumed that terminals can operate in all environments (urban and rural), and on land, at sea and on aircraft.

3 Allocation Status

The band 1525-1559 MHz is allocated to the MSS on a primary basis in both in the ITU Radio Regulations and the UK Frequency Allocation Table. Audio PMSE devices would operate as part of the mobile service which is allocated on a secondary basis in the band 1525-1535 MHz and would therefore be required not to cause harmful interference to MSS operations. In the band 1535-1559

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MHz, there is no allocation to the mobile service, both in the ITU Radio Regulations and in the UK Frequency Allocation Table.

Considering the current allocations in these bands, MSS operators have had no reason to anticipate potential interference from PMSE devices or any other mobile application in any part of the band 1525-1559 MHz. Ofcom has not offered any explanation of how PMSE devices would operate in conformance with the UK frequency allocation table.

4 Comments on the consultation document

4.1 Potential improvements in efficiency of spectrum use by wireless microphones

Inmarsat does not comment on Ofcom’s assessment of the expected growth in demand in PMSE services. However, we are surprised to read about the poor spectral efficiency with which PMSE equipment currently uses the UHF band as described in the Cambridge Consultants report3. The Cambridge Consultants report indicates that in some cases, when more than about 20 radio microphones are co-located, some types require more than 1 MHz bandwidth each. An average bandwidth requirement of 1 MHz per audio channel or more is extraordinarily poor efficiency. Cambridge Consultants identify a number of technical options to improve the frequency use of analogue and digital systems in sections 3.3.2 and 3.3.3 of their report. It seems that there is a significant potential for the PMSE community to make better use of the currently available spectrum, and with sufficient time and incentives, that might avoid the need to identify any new frequency bands for PMSE applications. As stated by the consultants: “It is concluded that, in general, technology advances will make possible deployment of the predicted simultaneous instances [of PMSE use] despite proposed reductions in available spectrum, so long as equipment manufacturers, hire companies and other users have sufficient incentive to invest in them. This means, as a minimum, a long-term guarantee of the spectrum available to PMSE, so that the high development costs and equipment costs can be amortised over time, for the relatively small manufactured volumes of professional equipment.”

We therefore believe that Ofcom should provide further encouragement to the PMSE community to use more spectrally efficient equipment in the existing bands.

4.2 Coexistence Analysis for the band 1525-1559 MHz

In section 4 of the consultation document, starting at para 4.43, Ofcom discusses the feasibility of using the band 1525-1559 MHz for PMSE operations. The use of this band for MSS operations in the UK and elsewhere is described in section 2 of this document. This band is used by receiving mobile earth stations, which may operate from any location in the UK. Given that terminals may operate from any location and may receive on any frequency within the band 1525-1559 MHz (excluding 1544-1545 MHz), that naturally means that there is no apparent means to ensure that interference would not be caused to MSS operations.

We note that in para 4.49 of the consultation document, Ofcom describes the current use of the band 1517-1525 MHz, which, apart from the lower 1 MHz, is shared with the MSS. Ofcom highlights that there have been no known cases of interference to MSS operations. It should be noted that

3 As described in the Cambridge Consultants report: “Technology Evolution in the PMSE Sector”, referred to by Ofcom in para 3.25 of the consultation document.

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there is currently very little use of this part of the spectrum by Inmarsat in the UK, partly due to constraints on the corresponding uplink band in some other European countries and partly due to the smaller number of terminals that are capable of operating in this band. Hence, the apparent lack of reported interference in this band is not indicative of the situation in the band 1525-1559 MHz and does not indicate that use of this band by PMSE would not cause interference to the MSS. We are not aware of any country other than UK deploying PMSE applications in the band 1518-1525 MHz, and several European countries have taken steps to limit use of this band by terrestrial applications so that it may be used for MSS operations.

We are concerned with the suggestion in para 4.52, that Ofcom might encourage other countries to also introduce PMSE operations into the band 1525-1559 MHz. Although we believe that sharing is not practicable in the UK, the situation is even more difficult in some other European countries where PMSE operations are licence exempt. In those countries, the regulator has no control over the location where PMSE is used and little control over frequencies of use or other technical parameters.

4.3 Practical testing

Regarding the practical testing carried out by Ofcom (described in paras 4.55 – 4.60), we believe that this is unreliable as a means to assess the interference criterion for MSS operations for several reasons:

• Firstly, we do not believe that the testing carried out accurately measured the failure point of the MSS terminals when subject to interference. Our own testing, which has tried to reproduce the results obtained by Ofcom for BGAN, has shown that the minimum operating point (using the same definition as used by Ofcom) is -116.6 dBm, between 2 and 6 dB lower than the values recorded by Ofcom. Although we have not tried to replicate the results obtained by Ofcom for the GSPS terminal, the negative C/I value reported by Ofcom (see Annex 1) leads us to also doubt the validity of those results.

• Secondly, the Ofcom testing did not assess the susceptibility of MESs to multiple interferers, as could be a typical scenario when multiple PMSE channels are used at the same location. The Ofcom testing examined the sensitivity of the terminals to interfering signals on frequencies adjacent to the wanted signal, but did not consider the additional impact from having two or more interfering signals at the receiver. Intermodulation products from the interfering signals could coincide with the MES desired signal, causing disruption to the terminal operation at much lower interference levels than for a single interfering signal on adjacent frequencies. There is some publicly available information on the susceptibility of terminals to two interfering signals, such as work conducted by the FCC4, which shows that the acceptable level of interference from two signals on adjacent frequencies is about 15 dB lower than the equivalent level of interference from a single interfering signal.

• Thirdly, the Ofcom testing did not take into account the variability in MSS operations that exists in practice. The testing was carried out for a terminal with an unobstructed view of the satellite, located close to the centre of the beam, with no apparent co-channel interference from other sources. This means that the terminal was operating with very high carrier power and very little external interference. While such conditions will sometimes exist, the particular conditions used are quite optimistic and more pessimistic conditions will apply in other cases. Many Inmarsat terminals, including the BGAN terminals used by

4 available at https://apps.fcc.gov/edocs_public/attachmatch/FCC-05-30A1.pdf

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Ofcom, use a system of adaptive coding and modulation to ensure the maximum throughput under the link conditions existing at the time of use. When the terminal is operating under optimum conditions (similar to those during the Ofcom testing), the impact of interference is initially to reduce the throughput and therefore performance is degraded long before the terminal is rendered totally non-functional by interference. The degradation to performance of Inmarsat users is not assessed by Ofcom’s analysis.

We provide more detail on these aspects in Annex 1.

It should also be noted that the measured failure points of the terminals would be different for different terminal types. For other services which do not use the adaptive coding and modulation system used by BGAN, the level of interference that would cause the terminal to cease to function is likely to be much lower.

4.4 Coexistence modelling

In paras 4.61 to 4.66 of the consultation document, Ofcom provides an analysis of the potential co-existence issues.

Considering potential interference to land based MESs, the analysis suggests that the required separation distances are around 100 – 180 m for GSPS (Table 7) and around 110 – 260 m for BGAN (Table 8). The use of the term “separation distance” is potentially misleading, since there is in fact no means to ensure separation between MESs and PMSE devices. The calculated distances give an indication of the geographic areas within which MSS users can expect to suffer interference. We believe that these distances suggested by Ofcom underestimate the actually required separation distances for several reasons, as explained below.

When assessing the impact of co-channel interference to MSS operations, we believe that a more relevant criterion should be developed on the basis of a theoretical analysis, which is quite typical for this type of compatibility analysis. In Annex 1, we derive the maximum level of interference based on a 1 dB loss of margin to the MES. The interference levels, using the same reference point as used by Ofcom are -134.6 dBm for BGAN and -123.8 dBm for GSPS. These values are 11.1 dB lower than the criterion used by Ofcom for the BGAN terminal, and is 6.5 dB lower than the criterion used by Ofcom for the GSPS terminal, even after taking account of the 6 dB “additional margin” included in the calculations by Ofcom.

The criteria proposed by Inmarsat could also be used for other Inmarsat services such as the M2M terminals. which do not use the highly resilient adaptive coding and modulation system used by the BGAN services and are therefore more susceptible to interference. Although the receiver noise power and bandwidth varies from one terminal type to another, the difference is relatively small and so a criterion of 1 dB loss of margin for BGAN and GSPS is suitable for the majority of Inmarsat terminals.

These criteria are useful reference values as they indicate the level at which Inmarsat users will suffer at least degraded performance, and in some cases a loss of service. As is shown in the analysis in Annex 2 and Annex 3 of this response, the predicted level of interference from audio PMSE devices could in fact significantly exceed these criteria. For example Figure A2-1 shows that the level of interference could exceed an I/N value of 14 dB.

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The co-existence analysis in the consultation document has also included other optimistic assumptions. In the case of interference to land based terminals, the propagation model given by Recommendation P.1411 has been used. This model is intended for coverage prediction for the planning of short range radiocommuncation systems, rather than for the purpose of interference analysis between two systems. As a consequence, the model tends to overpredict the loss for a given distance and therefore may lead to results suggesting separation distances shorter than actually required. In addition, the propagation model in Recommendation P. 1411 as used by Ofcom applies to an urban environment and furthermore has been applied with a low level of certainty. We have tried to replicate the results indicated in the consultation document and believe that the site-general model was used for the Ofcom analysis with a location variability of 50%. It should be noted that for a location variability of 10%, for instance, the separation distances in Table 7 and Table 8 would almost triple.

In Annex 2, we provide some example separation distances using the criteria we propose above and using the ITU-R Recommendation P.452 propagation model, more applicable to this scenario. The required separation distances are much larger – at least several kilometres - with these assumptions.

The co-existence analysis has also assumed “body loss” values of 6 dB and 11 dB for hand-held devices and body-worn devices respectively. Inmarsat has participated in recent work within CEPT project team SE7 which has included consideration of body loss from wireless microphones. From the information provided to that group, including information provided on tests provided by some microphone manufacturers, it is apparent that there is no common understanding on how body loss is defined and further, that a wide range of values are possible. It is clear that in some cases, no body loss can be assumed. In the case of safety related services in particular it is important to be cautious about the assumptions and therefore in our analysis in Annex 2, we have also examined the impact of if the body loss is assumed to be 0 dB.

When considering PMSE devices used indoors, Ofcom has considered 15 dB of building loss. It is very difficult to predict the loss caused by building materials and there is a very wide range of values that can be measured, for example as shown in Recommendation ITU-R P.2040-0. The values measured range from about 0 dB to more than 50 dB. Although it is clear that some building would provide 15 dB loss or higher values, it is not clear how any assurance of the building loss could be provided. The only way to predict building loss with any accuracy is through measurements, and it would probably not be practical to conduct measurements at every potential location for PMSE devices. When considering the impact on safety applications in particular, it is important that assumptions such as 15 dB building loss occur in practice. Furthermore, we note that about half of the “Hotspot Venues” for PMSE use, according to Annex 2 of Annex 5 of the consultation document, are at race courses and motor race circuits – i.e. outdoor venues, where no building loss would be applicable. Notwithstanding the lack of clarity concerning how values of building loss of 15 dB or more could be assured in practice, in our analysis in Annex 2 and Annex 3, we also consider 15 dB building loss (in addition to 0 dB), to allow for a comparison with Ofcom’s results.

In para 4.65 and 4.66, the consultation document includes an analysis of interference to airborne MSS terminals or AESs (aircraft earth stations). Some of the detail of Ofcom’s analysis is not clear, in particular the assumed AES antenna patterns. Based on Ofcom’s own analysis, it is apparent that excessive interference would be caused to aircraft earth stations at an altitude of 1000m, 3000m or 10,000m from outdoor PMSE devices. Ofcom states, in para 4.66 that: “Our understanding is that

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aeronautical MSS is typically used above 3000 m (10,000 feet).” Airborne terminals may be used at any altitude and are used when the aircraft is on the ground at the airport. Typically, if operators cannot receive load calculations from their Operations Centres by terrestrial datalink then they will make satcom voice calls to the Centre to retrieve the information whilst on the ground or taxiing. This is critical information required for operation of the aircraft and if not received in a timely manner could cause delay to the flight.

Globally, if there are any special oceanic flight routing dispensations/Master Minimum Equipment List (MMEL) relief with the use of satcom, operators are reported as having to test that the Inmarsat service is working whilst the aircraft is on the ground prior to departure. Hence denial of service must be avoided.

There is a collaborative European programme involving ESA and Inmarsat to develop an enhancement to SwiftBroadband Safety, the “Iris” service. This involves 16 companies from 8 ESA member states and the airframers, Airbus and Boeing. The objective of the programme is to meet or exceed the performance requirements set for terrestrial datalink communication (VHF Datalink) and standardised for “initial 4D trajectory management” a key component of the future Air Traffic Management (ATM) system in Europe. As a result, for trials and eventual use of the system in the terrestrial airspace, protection of the available spectrum will be necessary.

It should be noted that aircraft routinely fly over central London at an altitude of around 1000m on approach to Heathrow airport. Therefore even a single, indoor PMSE device in London could cause excessive interference to an AES.

Even though Ofcom’s analysis suggests that excessive interference would be caused, in Annex 3, we provide our own analysis of potential interference to AESs, using the interference criterion applicable for BGAN as proposed by Inmarsat, as well as a different airborne MSS antenna radiation pattern. We would like to note that the results of the Ofcom analysis seem too optimistic, as the radiation pattern used in the study appears to overestimate antenna discrimination towards the PMSE terminal. In addition, Ofcom has not considered that the orbital location of the satellite, used to provide the service, can change in the future as alternative orbital locations or satellites may be used. The orbital location of Inmarsat satellites serving the UK has changed in the past and may change again in the future. Ofcom’s assumption of the airborne MSS terminal’s elevation angle of 20° towards the Inmarsat Alphasat satellite can therefore change, which can reduce the MSS antenna discrimination towards the PMSE and thereby increase the risk of interference. Since the airborne MSS terminals are used for safety services, we consider the minimum operation angle of the MSS terminal of 5° as an appropriate value for the analysis, which is consistent with the minimum value for which aeronautical MSS systems are designed.

The results of our analysis indicate that the operation of PMSE stations, whether indoor or outdoor, can pose serious interference risks to the airborne MSS terminal. A single PMSE terminal with EIRP of 20 dBm is capable of exceeding the interference criterion of the airborne MSS terminal at all aircraft heights, even when the PMSE terminal is operated indoors and 11 dB of body loss is considered. As mentioned above, the values for body loss and building loss can vary significantly in operational circumstances, which increases the risk for harmful interference to the MSS satellite terminals. Further, while aggregate interference from multiple PMSE terminals has not been considered in our study or in Ofcom’s analysis, it can be assumed that this would have a notable

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impact on overall interference to the MSS terminals. This is especially true for airborne MSS terminals, due to the wide radio-horizon of such operation.

It is notable that the analysis in the consultation document has not made any specific assessment for MESs located on ships. If PMSE devices are used near to the coastline, it is apparent that there is potential to cause interference to ship earth stations. For an oversea propagation path, there is naturally no ground clutter that can be assumed, and hence the required separation distances would be much larger than those suggested by the use of the P.1411 propagation model. One of the example locations we use in Annex 2 is the Millennium Stadium in Cardiff, which is about 2km from Cardiff Harbour. The analysis of this location suggests that ships in and close to Cardiff bay would suffer excessive interference. A similar situation would apply in other coastal areas if PMSE devices were permitted to be used near the coast.

5 Conclusions

We believe that the coexistence analysis provided by Ofcom has significantly underestimated the risk of interference to MSS operations due to the use of a number of incorrect or overoptimistic assumptions. In reality, all types of MSS user - land, maritime and aeronautical - could suffer interference from PMSE devices. Bearing in mind that some MSS applications are for safety services and other applications are high value and are designed to operate from any location, we don’t believe that the analysis presented by Ofcom has provided adequate assurance that the MSS users in the UK would not suffer excessive interference.

As a consequence, we oppose the introduction of PMSE devices in the band 1525-1559 MHz, and for that reason we support Ofcom’s proposal to make the band 960-1164 MHz available for PMSE.

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Annex 1

Review of the Test Report in Annex 7 of the Consultation Document

Annex 7 of the consultation document contains the results of tests taken with two MSS terminals which operate within the Inmarsat network: a BGAN terminal and a GSPS terminal. We believe that the “Minimum Operating Levels” (MOL) which are developed based on the measured results may be in error, as the values are much higher than expected from a theoretical analysis, and are higher than the values obtained by Inmarsat from our own testing.

It is useful to examine the MOL in terms of I/N ratio and C/I ratio, as shown in table A1-1 (for narrow beam operations only), using the figures provided by Ofcom.

Table A1-1 Analysis of maximum interference proposed by Ofcom

parameter unit BGAN GSPS Comment receiver channel bandwidth kHz 200 200 typical receiver noise temperature K 250 300 referenced to output of receiving

antenna Noise power dBm -121.61 -120.82 referenced to output of receiving

antenna terminal antenna gain in direction of PMSE interferer

dBi 10 0

terminal antenna gain in direction of satellite

dBi 10 3

wanted signal level (C) in the narrow beam

dBm -113.60 -125.05 Ofcom figures, from Tables 3 and 5 of Annex 7, at the Ofcom reference point, measured with linear polarised antenna.

Carrier power (C) dBm -100.60 -119.05 referenced to output of receiving antenna (circular polarised)

Minimum operating level (= max level of interference, I)

dBm -114.56 -108.29 Table 4 and Table 6 of Annex 7. At the Ofcom reference point, measured with linear polarised antenna.

terminal antenna polarisation discrimination

dB 3 3 Linear to circular

Interference power (I) dBm -107.56 -111.29 referenced to output of receiving antenna

C/I ratio dB 7.0 -7.8 I/N ratio dB 14.1 9.5

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Loss of link margin due to interference

dB 14.2 10.0 calculated from I/N ratio

The minimum operating levels proposed by Ofcom would cause a loss of margin to the link of 14.2 dB in the case of BGAN and 10 dB in the case of GSPS. These are extraordinarily high levels of interference for any service to tolerate and would certainly render the terminals inoperable. Our own testing of the BGAN terminal, using the same value of carrier power, has shown that the minimum operating level (1 dB below failure point) is -116.6 dBm. Based on our own testing and the analysis of Ofcom’s results above, we believe that there may have been errors made during Ofcom’s tests and therefore that these results are not reliable.

Inmarsat proposes that for the purposes of this consultation, a more realistic criterion would be based on a 1 dB loss of margin, equivalent to -6 dB I/N value. This level of interference would cause significant degradation to the performance of our services and in some cases would prevent the operation of the desired service.

Table A1-2 Derivation of criterion proposed by Inmarsat

parameter unit BGAN GSPS Comment receiver channel bandwidth kHz 200 200 typical receiver noise temperature K 250 300 referenced to output of receiving

antenna Noise power dBm -121.6 -120.8 referenced to output of receiving

antenna I/N ratio dBi -6 -6 terminal antenna gain in direction of PMSE interferer

dBi 10 0

Maximum interference dBm -127.6 -126.8 referenced to output of receiving antenna

Maximum interference dBm -134.6 -123.8 using Ofcom's reference point, for linearly polarised interfering signal

Inmarsat suggests that the values derived above, -134.6 dBm for BGAN and -123.8 dB for GSPS are more appropriate interference criteria for this analysis. These values are respectively 11.1 dB and 6.5 dB lower than the interference threshold values proposed by Ofcom for BGAN and GSPS, even after taking into account the additional 6 dB margin proposed by Ofcom in Table 6 of the consultation document.

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Annex 2

Example interference zone calculations for land and maritime MSS terminals

As explained in section 3 of our response, we believe that several of the assumptions used by Ofcom in its analysis are overly optimistic, meaning that the risk of interference to MSS operations is underestimated. There is a large variability in many of the important parameters, e.g. body loss, building loss, propagation model assumptions). Considering that MSS operations in the band 1525-1559 MHz include many safety and high value operations, we believe that more conservative assumptions should have been taken.

We provide below some examples of calculations with more realistic assumptions, which demonstrate a much more significant risk of interference.

The following assumptions are made in all cases

PMSE Single device, used outdoors, 20 dBm eirp (the maximum power proposed by Ofcom), body loss = 0 dB and 11 dB, 5 m agl

MSS Maximum interference = -134.6 dBm (for BGAN), using Ofcom’s reference point (see Annex 1 for derivation), 1 m agl.

Propagation model P.452, and using terrain data base. Percentage of time p = 20%. Assumes 20 dB clutter loss.

Analysis is made for the following locations of PMSE use, which have been identified as locations likely to require additional spectrum beyond that in the UHF band. Cardiff is shown as a hotspot area in Figure 6 of Annex 5 of the consultation document, and is an important location to consider because it is close to the coast. The Glastonbury Festival site is used as a test location by Ofcom in Table 5 of the consultation document, and is an important case to consider since this is a rural area, where most PMSE use is outdoors. The Silverstone Circuit is identified in Annex 5 as having “the highest use out of all PMSE use throughout the UK” and is therefore also a useful test case.

Case Audio PMSE location 1 Millenium Stadium, Cardiff

(51°28'41.55"N, 3°10'57.48"W) 2 Glastonbury Festival site, Pyramid Stage

(51° 9'19.83"N, 2°35'10.82"W) 3 Silverstone Circuit, Towchester (52°

4'44.80"N, 1° 0'54.71"W)

The results of the analysis have been presented in Figures A2-1 to A2-6 below. The light yellow to red colouring on the figures indicates the locations where the interference criterion of -134.6 dBm is predicted to be exceeded by the PMSE terminal. The different levels of interference-to-noise ratio that correspond to the colouring have been indicated on the images below.

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Case 1 - Millennium Stadium, Cardiff

FIGURE A2-1 Interference from Millennium Stadium into a BGAN terminal (0 dB body loss)

Inmarsat’s analysis shows that the interference criterion can be exceeded as far as 64 km away from the Millennium Stadium, when PMSE body loss is not considered. It can also be seen that the interference criterion is expected to be exceeded for the majority of locations within a 15 km radius around the PMSE, which includes offshore locations where Inmarsat’s maritime terminal can be expected to be operating.

FIGURE A2-2 Interference from Millennium Stadium into a BGAN terminal (11 dB body loss)

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When 11 dB PMSE body loss is considered for transmissions from the Millennium Stadium, the interference criterion can be exceeded as far as 29 km away. In addition, interference is expected to be exceeded for the majority of locations within a 9 km radius around the PMSE station, which can also have an impact on Inmarsat’s maritime terminals, when operating close to Cardiff Harbour.

Case 2 - Glastonbury Festival site

FIGURE A2-3 Interference from Glastonbury festival site into a BGAN terminal (0 dB body loss)

The analysis shows that the interference criterion can be exceeded as far as 77 km away from the Glastonbury festival site, when PMSE body loss is not considered. It can also be seen that the interference criterion is expected to be exceeded in a passage that is roughly 5 km wide and extends for around 17 km west from the PMSE terminal at the Glastonbury festival site.

FIGURE A2-4 Interference from Glastonbury festival site into a BGAN terminal (11 dB body loss)

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When 11 dB of PMSE body loss is considered, the interference criterion is expected to be exceeded as far as 17 km away from the Glastonbury festival site and for roughly 9 km in an continuous area West from the festival site.

Case 3 - Silverstone Circuit

FIGURE A2-5 Interference from Silverstone Circuit site into a BGAN terminal (0 dB body loss)

The results show that the interference criterion can be exceeded as far as 44 km away from the Silverstone Circuit, when PMSE body loss is not considered. It can also be seen that the interference criteria is expected to be exceeded for majority of the locations within a 15 km radius around the PMSE terminal.

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FIGURE A2-6 Interference from Silverstone Circuit site into a BGAN terminal (11 dB body loss)

When PMSE body loss in considered for transmissions from the Silverstone Circuit, the interference criterion can be exceeded as far as 23 km away. In addition, interference is expected to be exceeded for most of the area within a 10 km radius around the PMSE station.

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Annex 3

Separation distance calculations for airborne MSS terminals

Inmarsat has studied the separation distances required between airborne MSS terminals and PMSE terminals. The analysis has been conducted similarly to Ofcom, by considering the free space loss between the MSS station on-board the aircraft and the PMSE station on the ground, while also factoring in the antenna discrimination of the MSS station towards the PMSE station. However, we have used the airborne MSS antenna radiation pattern from one terminal manufacturer that was provided to CEPT project team SE7 instead of the one used by Ofcom. We believe that the results obtained with the radiation pattern used by Ofcom are somewhat optimistic and thereby underestimate the risk of interference. The airborne MSS antenna radiation pattern used in our analysis is shown below.

In addition, our analysis assumes a 5° elevation angle of the airborne MSS terminal. We note that the elevation angle of 20° is assumed in Ofcom’s calculation, which corresponds to the pointing of MSS terminals operated in the United Kingdom towards the Inmarsat’s Alphasat satellite at 25° E. Such assumptions however, do not consider that the location of satellites may change in the future or other satellites with different orbital locations can be used for the service. Changes to satellite orbital locations can reduce the antenna discrimination in the direction of the PMSE and therefore increase interference to the airborne MSS terminal. Since the frequency range is used for safety applications, we believe that a conservative assumption is more appropriate. Therefore, the minimum operational elevation angle of 5° for satellite terminals is used instead.

Figure A3-1 Airborne satellite terminal antenna pattern

Based on the interference criterion of -127.6 dBm suggested by Inmarsat (see Table A1-2 ) and the EIRP of the PMSE, we can calculate that the required path loss for each case. We have only considered the body worn microphone with an EIRP of 20 dBm in both indoor and outdoor scenarios while considering cases with and without body loss. The required path loss between the PMSE terminal and the airborne MSS terminal for these cases is shown in the table below.

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Body worn mic (indoor) Body worn mic (outdoor) PMSE EIRP (dBm) 20 20 20 20 Building loss (dB) 15 15 0 0

Body loss (dB) 11 0 11 0 Polarization loss (dB) 3 3 3 3

Interference threshold (dBm) -127.6 -127.6 -127.6 -127.6 Required path loss (dB) 118.6 129.6 133.6 144.6

The results of our path loss calculations are indicated in the table below for aircraft at the height of 1-10 km and for PMSE stations placed 5-40 km from the location on the ground directly underneath the aircraft. The path loss is given by the free-space-loss (dB) minus the airborne terminal antenna gain (dBi).

PATH LOSS BETWEEN PMSE AND AIRBORNE MSS STATIONS (dB)

Ground range (km)

Aircraft height

(km)

5 10 15 20 25 30 35 40

1 99.3 104.3 107.5 110.0 112.0 113.5 114.8 116.0

3 106.4 107.0 108.8 110.7 112.3 113.8 115.0 116.1

10 122.1 120.1 117.2 116.6 116.7 117.1 117.7 117.9

The results of the study indicate that the required path loss is not achieved when the operation of the body worn microphone with 20 dBm EIRP is considered, even when the terminal is operated indoors while considering body loss. In that optimistic case, the required loss is 118.6 dB whereas the actual loss is less than 118.6 dB for an aircraft at an altitude of 10km (32,800 feet) and lower. Therefore, there is a serious risk for interference to the MSS terminals operated on board aircraft, irrespective of the aircraft altitude.

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