REPORT of the ICAO NSP SPECTRUM SUB-GROUP MEETING (Rev1)
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ACP-WGF20/WP-19 International Civil Aviation Organization 19 March 2009
DRAFT WORKING PAPER
AERONAUTICAL COMMUNICATIONS PANEL (ACP)
TWENTIETH MEETING OF WORKING GROUP F
Montreal, Canada 24 March - 3 April 2009
Agenda Item 9: Any Other Business
REPORT OF THE ICAO NSP SPECTRUM SUB-GROUP MEETING
17th to 20th March 2009, EUROCONTROL Experimental Centre, Bretigny, France
I. Introduction
The meeting of the ICAO NSP Spectrum Sub-group (SSG) was held at the EUROCONTROL Experimental Centre in Bretigny-sur-Orge, France from 17th to 20th March 2009. Mr. Felix Butsch, the rapporteur of the SSG, chaired the meeting. The spectrum sub-group expressed its appreciation to Mr. Dave Young, the representative of the EUROCONTROL Experimental Centre for hosting the meeting. Attachment A contains a list of action items and actionees. Attachment B provides a list of participants.
The following table contains an overview of agenda items with corresponding working and infor- mation papers, which were discussed by the Spectrum Sub-group: WP/IP No. Title Presented to NSP by (Presented to SSG by) Agenda Item 6a): Signal and compatibility issues in the band 5000 to 5150 MHz WP2 “ITU-R Working Party 4C request for information on MLS” ICAO secretariat Att. 1: ITU Working Party 4C – Liaison statement to Working Party 5B (Alessandro Capretti) (Document 4C/162) Att. 2: ITU Working Party 5B – Reply liaison statement to Working Party 4C (Document 5B/138) WP11 Modelling the unwanted emission characteristics of MLS Stefan Naerlich (Felix Butsch) WP4 MLS Implementation in the Russian Federation Vladimir Korchagin (Mikhail Markelov) Flimsy 1, rev.3 “Response to WP4 request (by ITU for information on MLS)” Jules Hermens Flimsy 2 “MLS unwanted emission characteristics in the band 5010- (Alain Delrieu) 5030 MHz” (Power Point Presentation) Flimsy 3, rev.2 “Request for clarifications on WP 11 `Modelling the unwanted (Alain Delrieu) emission characteristics of MLS´ and alternate MLS DPSK Spectrum roll-off derivation” Flimsy 4 “MLS spectra measured by LVNL – Levels at 3 different offsets (Alain Delrieu) from centre frequency” Flimsy 5 MLS characteristics – extract from draft Volume 3 of ICAO Doc (Alain Delrieu) 8071” Flimsy 8 List of potential European MLS locations according to responses to a ICAO secretariat
Page 1/17 State letter by ICAO (Microsoft Excel-File) (Alessandro Capretti) Flimsy 9 Determination of expected MLS Power Flux Density at the lower (Alain Delrieu) band edge at 5030 MHz (Microsoft Excel-File) Flimsy 10 Vertical antenna pattern of MLS DPSK signals from EUROCAE (Alain Delrieu) Ground Equipment MOPS (ED-53) Flimsy 12 MLS DPSK Duty Cycle Jules Hermens Flimsy 13, Proposed Modifications to Flimsy 9 –“ Determination of expected (Robert Frazier) rev.1 MLS Power Flux Density at the lower band edge at 5030 MHz” (Microsoft Excel-File)”
Agenda Item 6b): Navigation data links in the band 108 to 117.975 MHz WP5 “Use of the band 112 – 117.975 MHz by VDL Mode 4 ICAO secretariat - Review of the comments provided by the SSG”. (Robert Witzen) WP3 “Experimental data on VHF COM – VOR/ILS Transmitter-to- Vladimir Korchagin Receiver Isolation in the 108 – 137 MHz Band for medium-sized (Mikhail Markelov) aircraft” WP8 “Work plan to establish the potential number of assignable GBAS Ken Ashton frequencies in the frequency band 117.975 – 137 MHz” (Steve Mitchell WP7 “Analysis of apparent discrepancy between the test points specified Ken Ashton in ITU-R Recommendation M.1841 and the ICAO specification for (Steve Mitchell) the GBAS DOC WP15 Comments Regarding WP 5 Tim Murphy "Use of the band 112 – 117.975 MHz by VDL Mode 4 - Review of the comments provided by the SSG (October 2008)” Flimsy 6 “VHF COM – VOR/ILS Transmitter-to-Receiver Isolation in the Vladimir Korchagin 108 – 137 MHz Band” (Mikhail Markelov, Robert Witzen)
Agenda Item 6c): GNSS signal and interference issues Note: No dedicated WPs or IPs have been presented under this agenda item.
Agenda Item 6d): Signal and compatibility issues in the band 960 to 1215 MHz Note: No dedicated WPs or IPs have been presented under this agenda item.
Agenda Item 6e): Compatibility between broadcasting systems in the 87.5 to 108 MHz band and aeronautical systems above 108 MHz No dedicated WPs or IPs have been presented under this agenda item.
Agenda Item 6f): Open actions for the SSG from the ICAO NSP Working Group 1 meetings Note: No dedicated WPs or IPs have been presented under this agenda item.
Agenda Item 6 g): Spectrum – any other business Flimsy 7 “IF-77 Propagation Software”, Power Point Presentation Bruce DeCleene (John Tepper)
Page 2/17 II. Results of the Discussions
Agenda Item 6a): Signal and compatibility issues in the band 5000 to 5150 MHz
WP2, “ITU-R Working Party 4C request for information on MLS” Att. 1: ITU Working Party 4C – Liaison statement to Working Party 5B (Document 4C/162) Att. 2: ITU Working Party 5B – Reply liaison statement to Working Party 4C (Document 5B/138)
6a1) This WP made the group aware, that the last meeting of ITU-R Working Party 4C (WP4C) (29thSep. to 8th Dec. 2008) produced a Liaison statement (Attachment 1 to WP2) to ITU-R Working Party 5B (WP5B), requesting information on unwanted MLS emission characteristics in the 5010 – 5030 MHz band and on location of operating and planned MLS transmitters. WP4C is the ITU-R group responsible for the radionavigation-satellite service (RNSS), while WP5B is the group responsible for the aeronautical radionavigation service (ARNS). The request for information was made in anticipation of the deployment of RNSS systems operating in the 5010 to 5030 MHz band, using the RNSS (space-to-Earth) allocation in that band. WP5B (29th Oct. to 7th Nov. 2008) acknowledged the request and undertook to endeavor to provide the requested information with the assistance of ICAO to WP4C.
6a2) The SSG noted that the requested information on MLS characteristics should include transmitter antenna characteristics, power levels, modulation techniques, polarization and how the signals vary with frequency and time. In addition, Working Party 4C requests information on the location of operating and planned MLS transmitters for use in determining the possibility that a RNSS receiver is affected by multiple MLS transmissions.
WP11, “Modeling the unwanted emission characteristics of MLS” 6a3) In response to WP2 this paper presented a derivation of a model for the unwanted emission characteristics of the DPSK signals transmitted by MLS. This model for the unwanted emission characteristics of MLS presented in this paper had been originally developed for the MLS ad hoc group for the ICAO EANPG Frequency Management Group in 2006. This WP presents a more detailed derivation of the emission mask than earlier papers dealing with this issue. However the derived formula for the MLS emission mask is the same as 2006.
Flimsy 3, rev.2, “Request for clarifications on WP 11 `Modeling the unwanted emission characteristics of MLS´ and alternate MLS DPSK Spectrum roll-off derivation”
6a5) During the discussion of Flimsy 3 and WP11 it turned out, that the model in WP11 was based on a spectrum measured by the Dutch ATS provider on a real MLS i.e. a pulsed DPSK signal. In contrast, the model in Flimsy 3 was tested by comparison to various spectra measured on continuous DPSK transmissions generated by an MLS signal simulator. The author of Flimsy 3 explained further, that his proposed model had the advantage to be unit-wise consistent and models better the integration of a Power Spectral Density of the DPSK signal when it is integrated over resolution bandwidths very much higher than the data-rate.
6a6) The SSG agreed, that the model for the emission characteristics of MLS presented in Flimsy 3 was suitable to determine the requested out-of-band emissions of MLS in the band 5010 to 5030 MHz requested by ITU WP4C.
Page 3/17 Flimsy 1, “Response to WP4 request (by ITU for information on MLS)” 6a7) In response to WP4 request by ITU WP4C for information on MLS characteristics Flimsy 1 contains excerpts from the relevant section 3.11.4.1.4 of ICAO Annex 10, Vol. I containing the radio frequency characteristics of MLS.
6a8) During the discussion of Flimsy 4 the SSG considered in particular the following parts of ICAO Annex10, Vol.1 as relevant to satisfy the ITU request for information: - Section 3.11.4.1.4 “Radio frequency signal spectrum” - Section 3.11.4.3 “Time-division-multiplex (TDM) organization” - Section 3.11.4.8.2 “Basic data structure and timing”. - Section 11.4.8.3 “Auxiliary data organization and timing” - Section 3.11.4.10 “Power density” - Section 3.11.5.2.1.2 “Antenna beamwidth”. - Section 3.11.5.2.2 “Coverage” as well as diagrams illustrating the coverage requirements contained in Attachment G, figures, G-5A, G5-B (azimuth coverage) and G-6 (back-azimuth coverage), G-10A “Elevation approach region coverage”, G10-B “Elevation minimum coverage”. - Table A-2, “Approach azimuth function timing” - Table A-3, “High rate approach function timing” - Figure G-3A “Transmission sequence for all MLS angle guidance functions” - Figure G-3B “Transmission sequence for MLS approach azimuth angle guidance functions” - Figure G-13 “Beam shape of the scanning beam” - Table A-6 “Basic data functioning” - Table A-7 “Basic data” - Table A-8 “Auxiliary data functioning - Table G-1 “Signal Power Budget” - The vertical antenna pattern of the azimuth scanning beam, DPSK and OCI signals from EUROCAE ED53 (Flimsy 10)
Action SSG14/1: Jules Hermens to compile and present all information on the timing schemes of the various MLS signals which contribute to the DPSK transmission duty cycle.
Note: This action has been accomplished by Flimsy 12.
6a9) In this context it was pointed out by one member of the SSG that the deadline set by ITU WP4C for the provision of the requested information is the 15th of April. Therefore, any related information needs to be ready for the next ICAO ACP WG/F meeting in March 2009.
Action SSG14/2: Alain Delrieu to compile all relevant information on MLS characteristics from ICAO Annex 10 to present it to March meeting of WG/F.
Flimsy 2, “MLS unwanted emission characteristics in the band 5010-5030 MHz” 6a10) This Flimsy contains a Power Point Presentation containing a compilation of the following information: MLS antenna characteristics: vertical pattern from the EUROCAE Ground MOPS, ED-53 MLS transmit spectrum: measured by the French DGAC in 2003 Equation modelling the MLS transmit spectrum applicable for a large resolution bandwidth in relation to the DPSK data rate Map of potential European MLS locations from ICAO NSP May 06 WG1&2/WP 39
Note: Flimsy 2 was discussed in conjunction with Flimsy 3. The discussion of this material is therefore contained in the paragraphs of the report dealing with Flimsy 3.
Flimsy 4, “MLS spectra measured by LVNL – Levels at 3 different offsets from centre frequency” 6a11) Flimsy 4 contains various MLS spectra measured by LVNL supporting the developing the model for MLS emission characteristics presented in Flimsy 3.
Page 4/17 Flimsy 5, “MLS characteristics – extract from draft Volume 3 of ICAO Doc 8071” 6a12) Flimsy 5 presents excerpts from draft Volume 3 of ICAO Doc 8071 dealing with the MLS adjacent channel measurement and the derivation of the RF-spectrum limits in the SARPs .
Flimsy 8, “List of potential European MLS locations according to responses to a state letter by ICAO” 6a13) This Flimsy contains a “List of potential European MLS locations according to responses by European States to a State letter by ICAO in 2006”.
Flimsy 9, “Determination of expected MLS Power Flux Density at the lower band edge at 5030 MHz” 6a14) This Flimsy is an Microsoft Excel Spreadsheet containing the derivation of the expected MLS maximum Power Flux Density (PFD) at the lower band edge at 5030 MHz which was discussed and agreed by the SSG. The derived PFD is applicable at the following two points: - at a height of 600 metres above the ground station (i.e. at an elevation of 15 degrees) corresponding to a slant distance of 2.318 km (section 3.11.4.1.4.1 of ICAO Annex 10. Vol.1) - on ground at a distance of 4.8 km (section 3.11.4.1.4.2 of ICAO Annex 10. Vol.1)
6a14a) The derivation of the expected MLS Power Flux Density at the lower band edge at 5030 MHz contained in Flimsy 9 was modified later in the discussion. The agreed revised version is contained in Flimsy 13 rev.1.
Flimsy 13, rev.1, Proposed Modifications to Flimsy 9 –“ Determination of expected MLS Power Flux Density at the lower band edge at 5030 MHz” (Microsoft Excel-File)”. 6a14b) This flimsy contains the agreed final version of the derivation of the expected MLS Power Flux Density at the lower band edge at 5030 MHz which was originally contained in Flimsy 9. It comes to the conclusion that, the maximum MLS pfd at RNSS band edge (5030 MHz) measured in 1 MHz bandwidth is –96 dBW/m².
Flimsy 10, “Vertical antenna pattern of MLS DPSK signals from EUROCAE Ground Equipment MOPS (ED-53)” 6a15) This Flimsy presents a diagram with the vertical antenna pattern of MLS DPSK signals from EUROCAE Ground Equipment MOPS (ED-53).
Flimsy 12, “MLS DPSK Duty Cycle” 6a15a) This flimsy contains a compilation of information on the Duty Cycle of the MLS DPSK signal. It comes to the following conclusions that the total duration of DPSK transmissions within a frame is 153.5 ms. This results in a duty cycle of 153.5/615 x 100% = 24.9%. In the other 75% of the time un-modulated carrier can be seen be a receiver due to scanning beams, OCI and clearance pulses. Members of the SSG pointed out, that it would also be important to know the worst-case dwelling time of the scanning signal a RFI victim receiver would face. It was then calculated that the beamwidth of 3 degrees scanning 0.2 degrees/s leads to a dwelling time 150 s for the scanning beam. For the Out-of-Coverage Indication (OCI) a minimum dwelling time of approx. 100 s was determined. Another SSG member added that the dwelling times could be extended by multipath reception.
6a16) After presentation of flimsies 1, 2, 3, 4, 8, 9, 10, 12 and 13 a general discussion on, how to answer the request of ITU WP4C for information on MLS characteristics took place. The SSG decided, that the response to ITU shall be prepared at the up-coming ICAO ACP WG/F meeting. For this purposes the following peaces of information shall be provided by various members of the SSG in due time: a) MLS radio frequency characteristics: A compilation of the RF characteristics and timing schemes shall be put together using the relevant sections from ICAO Annex 10 (Action SSG14/2)
Page 5/17 b) The calculated MLS power flux density at the band edge at 5030 MHz as contained in the Spreadsheet in Flimsy 13 rev.1 c) The vertical antenna pattern of MLS DPSK signals from EUROCAE Ground Equipment MOPS (ED-53) as contained in Flimsy 10 d) An azimuth antenna pattern for the DPSK signal. It is still to be clarified, whether the azimuth coverage of the DPSK signal is omni directional or is sector-shaped with a width of +/- 60 degrees). Until further clarification, an omni directional behavior with 0 dBi gain outside the required coverage of of +/- 60 degrees shall be assumed. e) A list of potential European MLS locations according to responses by European States to a State letter by ICAO in 2006 as contained in Flimsy 8 f) A map of the potential European MLS locations according to responses by European States to a State letter by ICAO in 2006 as contained on the last slide of Flimsy 2
Action SSG14/3: Jules Hermens to clarify the azimuth pattern of the MLS DPSK signal (coverage and variation wrt. azimuth angle)
Action SSG14/4: Alessandro Capretti to compile all information on MLS characteristics to be provided to ICAO ACP WG/F
WP4, “MLS Implementation in the Russian Federation” 6c17) In response to the request of information on unwanted MLS emission characteristics in the 5010 to 5030 MHz band and on location of operating and planned MLS ground facilities WP4 reported about the Russian plans on MLS deployment.
6c18) The SSG noted, that at the present time there are no operating MLS facilities and no specific plan to deploy MLS in Russia. However, in some locations where existing CAT II/III ILS cannot be maintained or where MLS operational and/or economic benefits are proven MLS ground facilities may be implemented at a later time. According to initial plan 16 MLS ground facilities should be deployed at 5 airports located in the European part of the Russian Federation (list contained in WP4).
Agenda Item 6b): Navigation data links in the band 108 to 117.975 MHz
WP3, “Experimental data on VHF COM – VOR/ILS Transmitter-to-Receiver Isolation in the 108 – 137 MHz Band for medium-sized aircraft”
6b1) WP3 presents experimental data related to isolation between onboard VHF COM transmitters and VOR/ILS receivers in connection with discussion on VDL Mode 4 frequency assignment planning criteria that took place during the last SSG meeting. Based on transmitter-to-receiver isolation data collected for the two ‘medium-sized’ aircraft types Antonov An-74 and Beriev Be- 200 operated in Russia, WP3 comes to the conclusion that for medium-sized aircraft transmitter- to-receiver isolation in the 108 – 137 MHz band for VHF COM and VOR/ILS installations can be as low as 39 – 42 dB despite the fact that these systems use cross-polarized antennas. This shows that the total transmitter-to-receiver isolation between VHF COM and VOR/ILS installations even for medium-sized aircraft can be significantly lower than the values used in WP16 of the previous SSG meeting.
6b2) WP3 concluded that taking into account very limited capability to ensure adequate spatial separation between VDL Mode 4 antenna and other NAV/COM antennas onboard of medium, small and light aircraft, it would be appropriate to obtain and assess more information regarding transmitter-to-receiver isolation typical for these categories of aircraft. Until then the authors of WP3 recommended strongly to avoid onboard transmissions in the 112 – 118 MHz band and to use this band for VDL Mode 4 up-link only.
6b3) The SSG deemed the transmitter-to-receiver isolation data on medium-sized aircraft and presented in WP3 as very useful. The group decided to request that NSP members provide
Page 6/17 additional data relevant to transmitter-to-receiver isolation between VHF COM and VOR/ILS onboard installations in particular on medium, small and light aircraft.
6b4) The SSG agreed, that until the completion of detailed compatibility studies, in particular with regard to transmitter-to-receiver isolation achievable on medium, small and light aircraft, VDL Mode 4 onboard transmissions in the 112 – 117.975 MHz are not deemed acceptable.
Action SSG14/5: SSG members to provide measurement results on transmitter-to-receiver isolation achievable on medium, small and light aircraft for VDL Mode 4 compatibility studies.
WP5, “Use of the band 112 – 117.975 MHz by VDL Mode 4 - Review of the comments provided by the SSG”. 6b5) WP5 presents a review of the comments provided by the SSG on the results of testing of VDL Mode 4 with the view to establish frequency assignment planning criteria for the use of the band 112 – 117.975 MHz by VDL Mode 4. It also contains further test plans, as requested by the SSG.
6b6) The following list of comments by the previous SSG meeting was addressed in WP5 and discussed in the SSG meeting: (1) Separation distance between an VDL Mode 4 airborne transmitter and a GBAS receiver may be less than 350 m, when the aircraft equipped with a VDL4 transmitter is on the ground: During the discussion of this issue, it was pointed out, that it is important to secure also protection to GBAS category II/III. It was mentioned by members of the group that the GBAS designated operational coverage area (DOC) would extent in the future down to 12 feet above the runway or even lower. Since it will be difficult to achieve the necessary field strength at such low heights above ground, the minimum field strength for the GBAS VDB signal shall be used in the frequency planning criteria. Furthermore, it was emphasized, that radio frequency encounter scenarios between aeronautical radionavigation receivers and VDL-4 equipment at airports needs to be further analyzed.
(2) Further analysis of the potential on-board compatibility and its impact on frequency management: Various members of the group pointed out that this issue needs to be further explored. However the group was of the opinion that on-board compatibility is not directly related to the development of frequency planning criteria. It was deemed rather to be a task for on-board integrators and airworthiness certification organizations. If the on-board compatibility cannot be achieved for a certain aircraft type, the VDL-4 equipment could not be installed on-board.
(3) Further analysis of the assumed cross-polarization isolation (ILS/VOR/GBAS is horizontally polarized and VDL Mode 4 is vertically polarized): During the discussion of this subject it was mentioned by members of the SSG that European civil aviation decided to use only the horizontal component of the GBAS signal. This would allow benefiting from the cross-pol isolation between the vertically polarized VDL-4 and the horizontally polarized GBAS VDB signal. However for medium and light aircraft it would still be hard to achieve the necessary on-board isolation.
(4) Further compatibility analysis with GBAS VDB transmitters (Measurements to be taken with GBAS CAT-1 equipment in lieu of GBAS Special CAT-1 equipment): The author of WP5 announced that further compatibility measurements will be carried out with fully ICAO compliant GBAS equipment. Also a full channel loading anticipating additional message types to be used by GBAS CAT II/III would be simulated.
(5) Results of a VDL Mode 4 compatibility analysis carried out in the Eurocontrol VDL Mode 4 Airborne Architecture Study (VMAAS 2003): It was mentioned by the author of WP5 that the Eurocontrol study did not include measurements, but was rather based on theoretical analysis.
Page 7/17 (6) Demonstration that the utilized aeronautical receiver types are representative: In this context it was pointed out by the author of WP5 that it is planned to carry out further VDL4 compatibility tests with “low-end” ILS/VOR receivers.
(7) Presentation of the intended utilization of VDL Mode 4 to allow for a better analysis of RFI encounter scenarios and channel loading scenarios: It was emphasized by the author of WP5 that the intended utilization of VDL4 is already fully described in the ICAO VDL-4 manual, ICAO Doc 9818.
(8) Assessment of the implication of the obtained proposed separation distances to be discussed by operational groups, i.e. demonstration that the necessary separation distances are achievable with the intended operation: In this context it was mentioned by various members of the SSG that airport radio frequency encounter scenarios between aeronautical radionavigation receivers and VDL 4 equipment needs to be analyzed, since at airport it is highly likely that VDL4 on-board transmitters and navigation receivers will come closer than 600 metres.
(9) Consideration of the GBAS safety assessment: During the discussion of this issue it was pointed out by the author of WP5 that safety assessments are done by air navigation service providers and accepted by States or regional organizations, - not by ICAO.
(10) The “stuck transmitter” problem: It was mentioned that ICAO Annex 10, Vol. II paragraph Annex 10, Volume III, Part I paragraph 6.9.5.1.4.3 provides for: “Automatic transmitter shutdown. A VDL Mode 4 station shall automatically shut-down power to any final stage amplifier in the event that the output power exceeds -30 dBm for more than one second. Reset to an operational Mode for the affected amplifier shall require a manual operation.”
(11) Wrong auto-tuning of the airborne transmitter: It was mentioned in WP5 that after the ground transmitter has sent an auto-tune command to an aircraft, the VDL Mode 4 system will be required to send a confirmation of the tuning to a new frequency on the new frequency. In case the aircraft station does not receive a confirmation within a certain period of time (e.g. 10 seconds), the re-tuned VDL Mode 4 transmitter will be reset to its original frequency. Alternatively, the pilot can receive a command to manually reset the VDL mode 4 transmitter.
6b6a) Another important issue that was raised in WP5 was, that current GBAS standards make provision for only one lost message in 1500 messages, which makes GBAS very vulnerable to interference. This was considered by the author of WP5 as overly restrictive. To further explore this issue, SSG deemed it desirable that the CSG sub-group of NSP should provide details on how this requirement was derived.
Action SSG14/6: Andreas Lipp to ask CSG to provide the reference document containing the derivation of the allowable GBAS VDB message error rate requirement.
6b7) The SSG could not agree, that the material presented in WP16 (results of electromagnetic compatibility testing of VDL Mode 4 equipment with existing systems in the band 112 to 117.975 MHz, which was recently undertaken in Sweden) of the previous SSG meeting and WP5 of this SSG meeting was sufficient to be the basis of frequency planning criteria for VDL Mode 4.
6b8) The following list of the main open issues were mentioned as a rational by members of the group:
Page 8/17 No test-results of the compatibility between ICAO-compliant GBAS CAT I VDB transmitters and VDL 4 receivers were available (so far only Special CAT I equipment was used for the tests) GBAS DOC specifications for all precision approach categories (CAT I, II, III) need to be taken into account Airport Radio Frequency encounter scenarios between aeronautical radionavigation receivers and VDL 4 equipment needs to be analyzed Procedures for erroneous auto-tuning of airborne VDL4 transmitters need to be developed
Action SSG14/7: Robert Witzen to provide further test results of VDL4 compatibility studies
WP15, “Comments Regarding WP 5 "Use of the band 112 – 117.975 MHz by VDL Mode 4 - Review of the comments provided by the SSG (October 2008)”
6b9) WP15 paper offers a number of comments on WP5 for consideration by the meeting as part of its review of WP5: a) Questions about the plans for implementation of VDL-4 b) A statement that “Two aircraft can most certainly be closer than 600 m when one airplane is in the final stages of a landing and another airplane is taxiing on the airport surface. Furthermore, in such a situation, polarization isolation between vertically polarized VDL Mode 4 and horizontally polarized ILS or VDB reception is likely to be unreliable, as multipath can occur from sources that change the polarization of the multipath (e.g. a chain link fence). ” c) The question whether SARPS for GBAS or for VDL-4 were introduced first WP15 concludes that the adoption of preliminary coordination criteria for VDL-4 in the near future is considered overly optimistic.
6b10) During the discussion of WP15, members of the SSG pointed out, that there is no need to have an implementation plan for a new system in order to initiate the development of frequency assignment criteria for such a system by ICAO. The SSG agreed again on the statement in WP15 that “Two aircraft can most certainly be closer than 600 m when one airplane is in the final stages of a landing and another airplane is taxiing on the airport surface.” This fact should be therefore taken into account for the further work on the establishment of frequency assignment criteria for VDL-4. It was also mentioned by the ICAO secretariat that the SARPs of VDL-4 were published at the same time as the SARPs of GBAS.
Flimsy 6, “VHF COM – VOR/ILS Transmitter-to-Receiver Isolation in the 108 – 137 MHz Band” 6b11) This Flimsy addresses the material presented in working papers 3 and 5. It was mentioned in Flimsy 6 that the information provided in WP3 is consistent with information received from Rockwell-Collins that shows that, on the basis of actual measurements for a medium size aircraft (Fokker-50), the isolation between a top and bottom mounted antenna is about 50 dB; measurements for antennas installed on the same side of the fuselage, the isolation would be slightly less, about 45 dB.
6b12) Moreover, this paper proposes that the additional measurements on VDL Mode 4 and VOR compatibility with special attention to aspects relating to the integration of VDL Mode 4 on board an aircraft with the view to develop guidance material that can be used by aircraft manufacturers and system integrators. Also, these measurements should assess compatibility in case frequencies for VDL Mode 4 and VOR are separated at a relative large frequency distance.
Page 9/17 6b13) During the discussion of Flimsy 6 various SSG members mentioned, that in the European region it is common to not assign the highest VOR channel of 117.950 in areas, where the lowest radiocommunication frequency 118.0 MHz is used to avoid on-board interference issues.
6b14) Moreover, it was pointed out by one SSG member, that VOR and ILS monitors use a wide-open front-end Such a monitor does not only receive the local VOR or ILS channel, but rather the whole VOR or ILS band. It was warned that VDL-4 transmissions in the VOR-band could therefore cause such a monitor to shut-down the VOR or ILS. The SSG agreed that this issue should be analyzed further.
Action SSG14/8: Gerhard Berz to present a WP to a future SSG meeting addressing the interference threat between VDL-4 and VOR as well as ILS monitors.
WP7, “Analysis of apparent discrepancy between the test points specifies in ITU-R Recommendation M.1841 and the ICAO specification for the GBAS DOC”
6b15) WP7 reminded the SSG, that at its last meeting in October 2008, the issue was raised regarding the apparent discrepancy between the test points specifies in ITU-R Recommendation M.1841 and the ICAO specification for the GBAS DOC contained in Annex 10. It was felt by some members of the NSP SSG that the ITU recommendation should be aligned with Annex 10 in order to avoid any conflict with national radio regulators. After reviewing the material contained in the aforementioned ITU recommendation the authors of WP7 came to the conclusion that the DOC given in M.1841 for precision approach is not the same as that quoted in Annex 10. However they were of the opinion that this is balanced out by including text such as “…a typical DOC…”, “…Details can be obtained from the appropriate national Aeronautical Information Publication …” and also including an extract from Annex 10 on GBAS coverage. It should therefore be clear to the reader that the DOC for GBAS, and hence where test points might lie, needs to be considered on a case by case basis.”
6b16) Furthermore, it was emphasized in WP7 that the history in the development of M.1841 also indicates that both aviation experts and radio regulatory administrations are happy with its content. Additionally, given the difficulty that occurred in the ITU adopting M.1841 originally, it is likely that any attempt to amend it would not necessarily be acceptable to radio regulatory administrations.
6b17) The SSG agreed with the conclusion of WP7, that there is no need to modify ITU-R Recommendation M.1841,
WP8, “Work plan to establish the potential number of assignable GBAS frequencies in the frequency band 117.975 – 137 MHz”
6b18) WP8 reminded the SSG that, at previous meetings of the NSP WGW papers dealing with the possibility of extending the current frequency range for GBAS operations to the VHF radio- communication band 117.975 – 137 MHz were presented. WP8 provided a suggested work plan in order to assess the potential number of assignable GBAS frequencies that may be available in this band. It was suggested to model the GBAS designated operational coverage as a circular broadcast DOC with a range of 23 NM. The exercise to be carried out would then be, to find frequencies for a list of European airports using the VHF communication frequency search functionality of the Eurocontrol MANIF Software.
6b19) The SSG deemed the proposed procedure as adequate. One member of the group pointed out, that a German study presented in 2000 (“Possible lack of available spectrum for the allocation of VHF NABS in the ARNS-VHF Frequency Band in the area between of the states
Page 10/17 BEL/D/F/HOL/LUX in Europe”, J. Wollweber, WP12 of ICAO GNSSP, Working Group B, June 2000, Seattle) came to the conclusion, that all the VDB needs cannot be fulfilled in the 112- 117.950 MHz band without withdrawal of conventional Navaids in some parts of Europe. It was emphasized by one SSG member that the assumptions, which were used for this study are still valid today. 6b20) Although the SSG was aware of the many issues involved with the introduction of a GBAS VHF data-link into the VHF radiocommunication band, the SSG agreed to encourage further exploration of such a solution, because of the aforementioned scarceness of available GBAS frequencies in the VOR band. For this reason, and since the task to use the existing MANIF software for the initial assessment seemed to be pretty manageable, the SSG agreed to ask the UK to carry out the proposed exercise.
Action SSG14/9: UK to carry out a simulation of the attainable GBAS frequencies in the band 118 to 137 MHz using the MANIF software and modeling GBAS as a circular broadcast service with a range of 23 NM
Agenda Item 6c): GNSS signal and interference issues
Note: No dedicated WPs or IPs have been presented under this agenda item.
6c1) The rapporteur made the SSG aware, that in this context there the issue of the proposed change of the GNSS antenna requirements in ICAO Annex 10 remains still unresolved. At the last meeting of SSG in October 2008 it was pointed out that RTCA SC-159 and EUROCAE WG62 both agreed with modifying the antenna gain specification in order to reduce the minimum gain at 5 degree elevation from -4.5 dBic to –5.5 dBic because of concerns with the achievability of a minimum gain of -4.5 dBic). However, one participant argued in favor of deferring approval of the proposed change. He pointed out that it appears, based on preliminary analysis, that such a reduction might have a negative impact on Galileo link-budget”. SSG agreed to report this issue to its parent group WG1.
Action Item SSG14/10: Eric Chatre to provide the Oct. 2009 meeting of SSG material supporting the solution of the issue of the proposed revision of the GNSS antenna specification in ICAO Annex 10.
Agenda Item 6d): Signal and compatibility issues in the band 960 to 1215 MHz
Note: No dedicated WPs or IPs have been presented under this agenda item.
Agenda Item 6e): Compatibility between broadcasting systems in the 87.5 to 108 MHz band and aeronautical systems above 108 MHz
Note: No dedicated WPs or IPs have been presented under this agenda item.
6e1) The rapporteur reminded the SSG, that there is a draft new ITU-question on the “Compatibility between digital sound-broadcasting in the band of about 87-108 MHz and both the aeronautical radionavigation service in the band 108-117.975 MHz and the aeronautical mobile (route) service in the band 117.975-137 MHz” submitted by ITU WP5B (Document 5/87 WP5 meeting, Nov. 2008). He called on the members of the group to actively participate in the development of requirements to protect the affected services.
Action SSG14/11: SSG members to carry out compatibility measurements between digital sound- broadcasting in the band of about 87-108 MHz and aeronautical services in the band 108-117.975 MHz and to contribute to the development of protection criteria.
Page 11/17 Agenda Item 6f): Open actions for the SSG from the ICAO NSP Working Group 1 meetings
6f1) The SSG’s rapporteur reminded the group there is still the following open action item from the ICAO NSP meeting in Oct. 2006: “To develop guidance material to assist States facing an environment with a high level of interference to SBAS GEO satellites operating at the minimum signal strength specified by SARPs.”
6f2) Various members of the SSG pointed out that the parent group should specify this task more detailed, before work on this issued could be started.
Action SSG14/12: NSP secretary to seek clarification from WGW about the meaning of the task “To develop guidance material to assist States facing an environment with a high level of interference to SBAS GEO satellites operating at the minimum signal strength specified by SARPs.”
Agenda Item 6g): Spectrum – any other business
Flimsy 7, “IF77 Propagation Software -Presentation”
6g1) A new implementation of the IF77 propagation model, originally developed for FAA by ITS Institute of NTIA in the 1970’s to help the FAA in estimating service coverage was presented to the SSG. The new software was developed by the FAA Technical Centre. It is programmed in the “C”-programming language and has a Microsoft Windows user interface. It allows import of user-defined antenna patterns for ground transmitters and exports of calculation results.
6g2) A test-version of the new Microsoft Windows-based IF77-software was made available to the SSG members. They were invited to provide feed-back to the FAA.
Action SSG14/13: SSG members to try-out the test-version of new IF77 software and provide feed- back to FAA
6g3) One member of the group emphasized, that it would be desirable that a dynamic link-library version of this propagation model software with a specified interface would be made available. This would allow people to integrate this model into their own software tools for frequency compatibility analysis.
III Administrative maters
An updated action item list of the SSG can be found as Attachment B of this report. The next meeting of the Spectrum Sub-group is not yet decided..
Page 12/17 ATTACHMENT A: ACTION ITEM LIST Action Action Actionee Status number Actions from the Montreal meeting October 2005 (SSG8): SSG8/2 Present results of FMG on improved DFS Ongoing coordination criteria for conventional (see SSG/10, IP2) nav aids to SSG. SSG8/5 Prepare text for the RF handbook on Secretariat Open potential interference to GNSS by commercial broadcast
Actions from the Brussels meeting May 2006 (SSG9): SSG9/14 To investigate the basis for the SSG Closed by Flimsy 5 to SSG/14 derivation of the interference limit value of -94.5 dBW/m2 as applicable to MLS- type interference. SSG9/15 To undertake measurements to France Open investigate the impact of noise-like signals (AMT, FSS, RNSS) on the performance of MLS receiver. Actions from the Montreal meeting October 2006 (SSG10): SSG10/1 Robert Frazier (US) to further clarify the US Ongoing reason for “discontinuities” in the DME propagation curves. SSG10/8 To provide results of GBAS vs. ILS Christophe Open bench tests carried out by STNA in Dehaynain 2004. (France) SSG10/9 To present bench test results to SSG Open determine the interference threshold of VHF COM and ILS against GBAS signals. SSG10/10 To develop more detailed frequency SSG Open coordination criteria between GBAS and VHF-COM as well as GBAS and ILS for publication by ICAO. SSG10/11 To explore impact of change of Joachim Open propagation model in the guidance Wollweber material for the frequency co-ordination (Germany) of GBAS (section 7.2.1.3.3 of Attachment D to Volume 1 of ICAO Annex 10, and Tables D3 and D4.) and to draft a proposed revised version. SSG10/12 To review the GBAS SARPS changes in SSG Open WP23 (GBAS Positioning Service), in order to investigate the need of necessary changes of the guidance material, taking also in to account potential decisions of CSG on WP23.
Actions from the Delhi meeting March 2007 (SSG11):
SSG11/x To present a proposal of detailed DME/VOR Open guidance material on DME coverage coverage ad-hoc volume to be included in a new volume group of the ICAO RF-handbook, ICAO DOC 9718. SSG11/2 To present a proposal of detailed DME/VOR Open guidance material on VOR coverage coverage ad-hoc volume to be included in a new volume group of the ICAO RF-handbook, ICAO DOC
Page 13/17 9718.
Actions from the Montreal meeting March 2008 (SSG12):
SSG12/a To support adequate protection of SSG members Ongoing GLONASS within an RTCA Special Committee which works on RTCA DO- 210D. SSG12/4 To present the information contained in France Ongoing WP12 to future ICAO ACP WG/F meetings and or ACP WGW meetings, to point out the need to develop an I/N protection ratio for the FRS for the discussion of the compatibility between the Future Radio System and UMTS within CEPT regional radio regulatory organisations. SSG12/6 To carry out measurements of the SSG members Open susceptibility of aeronautical receivers Partly fulfilled by IP9 of SSG13. working in the band 108 and 137 MHz (ILS, VOR, GBAS, AM) to interference by such new VHF broadcast signals, with as many aeronautical receiver types as possible. SSG12/7 To keep SSG informed about the latest SSG members Open results of discussions of the com- patibility between digital broadcast and aeronautical systems in the VHF band. Actions from the Montreal meeting October 2008 (SSG13): SSG13/1 To present a paper on “Joint use of the ICCAIA Open band 5030 to 5150 by the Microwave Landing System (MLS) and the Aeronautical Mobile Satellite (en Route) Service (AMS(R)S)” to future ICAO ACP WGW and WG/F meetings. SSG13/2 To analyse the apparent discrepancy UK Accomplished by WP7 of between the test points specified ITU-R SSG/14 Recommendation M.1841 and the ICAO specification for the GBAS DOC. SSG13/3 To present a revised version of the WP Robert Witzen Open, Partially fulfilled by WP5 “Use of the band 112 to 117.975 MHz to SSG/14 by VDL Mode 4 - Results of tests and frequency assignment planning criteria” taking into account comments by SSG/13 and information on the Eurocontrol VDL Mode 4 avionics architecture study contained in SSG13/IP24. SSG13/5 To provide measurement results of DME SSG members Open spurious emissions in the RNSS bands (GPS L5, Galileo E5, Glonass L3 band) to establish the need for a change of DME MOPS. SSG13/6 To present the Flimsy1 containing the UK Completed proposed changes of sections 2.2.9.3 and 3.6.5.3 of ICAO Annex 10, Vol. 1, Attachment C dealing with 5th order intermodulation products of FM broadcast to CN&TSG. SSG13/7 To present a work plan to establish the UK Closed by WP8 to SSG/14
Page 14/17 number of potentially achievable additional frequency assignments for GBAS, if using the VHF communication band. SSG13/8 To present at a future NSP meeting an SSG members Open analysis of the impact of the change of GNSS antenna specification for the link- budget. SSG13/9 To propose a short additional text for Germany Open ICAO Annex 10, Vol. I, Attachment C, recommending that in frequency- congested areas more refined calculation of the required separation distance for ILS based on additional parameters like transmitter power, antenna gain, antenna directivity and antenna orientation is recommended.
Actions from the Bretigny meeting March 2009 (SSG14):
SSG14/1 To compile and present all information Jules Hermens Closed (Flimsy 12) on the timing schemes of the various MLS signals which contribute to the DPSK transmission duty cycle. SSG14/2 To compile all relevant information on Alain Delrieu Open MLS characteristics from ICAO Annex 10 to present it to March meeting of WG/F. SSG14/3 To clarify the azimuth pattern of the Jules Hermens Open MLS DPSK signal (coverage and variation wrt. azimuth angle) SSG14/4 To compile all information on MLS Alessandro Open characteristics to be provided to ICAO Capretti ACP WG/F SSG14/5 To provide measurement results on SSG members Open transmitter-to-receiver isolation achievable on medium, small and light aircraft for VDL Mode 4 compatibility studies. SSG14/6 To ask CSG to provide the reference Andreas Lipp Open document containing the derivation of the allowable GBAS VDB message error rate requirement. SSG14/7 To provide further test results of VDL4 Robert Witzen Open compatibility studies SSG14/8 To present a WP to a future SSG Gerhard Berz Open meeting addressing the interference threat between VDL-4 and VOR as well as ILS monitors. SSG14/9 To carry out a simulation of the UK Open attainable GBAS frequencies in the band 118 to 137 MHz using the MANIF software and modeling GBAS as a circular broadcast service with a range of 23 NM. SSG14/10 To provide the Oct. 2009 meeting of Eric Chatre Open SSG material solution of the issue of the proposed revision of the GNSS antenna specification in ICAO Annex 10. SSG14/11 To carry out compatibility SSG members Open measurements between digital sound-
Page 15/17 broadcasting in the band of about 87-108 MHz and aeronautical services in the band 108-117.975 MHz and to contribute to the development of protection criteria. SSG14/12 To seek clarification from WGW about Secretary Open the meaning of the task “To develop guidance material to assist States facing an environment with a high level of interference to SBAS GEO satellites operating at the minimum signal strength specified by SARPs.” SSG14/13 SSG members To try-out the test- SSG members Open version of new IF77 software and provide feed-back to FAA
Page 16/17 ATTACHEMENT B: LIST OF PARTICIPANTS OF THE SSG Atten- Name Organisation Telephone Email dance
Alain Delrieu F ICCAIA (ICR) +33 6 0863 9565 [email protected]
Alessandro Capretti P ICAO Secretariat +1-514-954-5847 [email protected]
+33 (0)1 6988 Andreas Lipp F EUROCONTROL [email protected] 7618/7307
DGAC/DSNA, Benoit Roturier P [email protected] France
ICCAIA (Thales Erwan LE HO, F +33(0)5 3435 5886 [email protected] Alenia Space)
Felix Butsch F DFS, Germany +49 6103-707-1533 [email protected]
Gerhard E. BERZ P EUROCONTROL +32 2 729 3734 [email protected]
Civil Aviation Ian Mallett P Safety Authority, [email protected] Australia Airservices Jeffrey Bollard p +61-262684949 [email protected] Australia
John Tepper P FAA, USA [email protected]
Netherlands Civil Jules Hermens P +31 70 456 3268 [email protected] Aviation Authority Airnavigation State Scientific & Mikhail Markelov F +7(495)-490-95-84 [email protected] Research Institute, Russia Geyser Scientific Nikolay Shienok F & Production Co. +7(495) 784-63-30 [email protected] Russia
Robert Frazier F FAA, USA +1-202-267-9722 [email protected]
ICAO Technical Robert Witzen F +1-514-4267654 [email protected] Advisor
Steve Mitchell F NATS, UK +44-1489-444646 [email protected]
Note: P/F = Part time/Full time attendance
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