1
ACP-WGF22/WP-/
International Civil Aviation Organization
INFORMATION PAPER / ACP-WGF25/IP-01
25th Meeting of THE
AERONAUTICAL COMMUNICATIONS PANEL WORKING GROUP F (WG-F/25)
(Dakar, 6 – 14 October 2011)
Agenda Item 6: / Any other businessREPORTOF THE
ICAO NSP SPECTRUM SUB-GROUP (SSG) MEETING
16th to 18thMay, 2011, ICAO Headquarters, Montreal, Canada
(Presented by SSG rapporteur Felix Butsch)
SUMMARYThis document contains the report of the meeting of the ICAO NSP Spectrum Sub-group (SSG) was held at ICAO Headquarters, Montreal from 16th to 18th May 2011.
I. Introduction
The meeting of the ICAO NSP Spectrum Sub-group (SSG) was held at ICAO Headquarters, Montreal from 16th to 18th May 2011. Mr. Felix Butsch, the rapporteur of the SSG, chaired the meeting. The Spectrum Sub-group expressed its appreciation to the ICAO secretariat for hosting the meeting.
Attachment A of this report 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 information 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 in the band 108 to 117.975 MHz
WP16 / Compatibility study between GBAS VDB link and ILS/VHF COM / S. Naerlich, B. Roturier
(P. Ladoux)
IP08 / Measurement results of the compatibility between GBAS VDB with ILS and VHF COM / S. Naerlich, B. Roturier
(P. Ladoux)
WP05 / Interference into ILS-Localizer and VOR monitor systems / Secretary
(Robert Witzen)
WP06 / Assessment of built-in system mitigations against erroneous tuning in VDL Mode 4 / Secretary
(Robert Witzen)
IP04 / VDL Mode 4 channel loading / Secretary
(Robert Witzen)
WP04 / Measurement of antenna isolation on a small aircraft / Secretary
(Robert Witzen)
WP09 / SUKHOI RRJ-95 transmitter-to-receiver isolation between VHF COM and VOR/ILS(LOC) equipment / V.Korchagin
(Mikhail Markelov)
Agenda Item 6b): Signal and compatibility issues in the band 960 to 1215 MHz
WP27 / L-Band Compatibility Issues
- Questions on DME/TACAN Characteristics / StefanNaerlich
(Joachim Wollweber)
IP20 / L-Band Compatibility Issues
- Update of the DME/TACAN RFI compatibility characteristics / Stefan Naerlich
(Joachim Wollweber)
WP28 / L-Band Compatibility Issues
- Characteristics of the Identification Signal of DME/TACAN / StefanNaerlich
(Joachim Wollweber)
WP29 / L-Band Compatibility Issues
- DME/TACAN Interrogation Repetition Frequency (IRF) / StefanNaerlich
(Joachim Wollweber)
WP30 / L-Band Compatibility Issues
- DME/TACAN Interrogator Accuracy
vs. Up-date Rate in Memory Mode / StefanNaerlich
(Joachim Wollweber)
WP31 / L-Band Compatibility Issues
- Reply efficiency with On Board Suppression Bus Loading / StefanNaerlich
(Joachim Wollweber)
WP32 / L-Band Compatibility Issues
- DME/TACAN Receiver Bandwidth / StefanNaerlich
(Joachim Wollweber)
WP33 / L-Band Compatibility Issues
- DME/TACAN Receiver sensitivity / StefanNaerlich
(Joachim Wollweber)
WP34 / L-Band Compatibility Issues
- DME/TACAN transponder monitor interference susceptibility / StefanNaerlich
(Joachim Wollweber)
WP35 / L-Band Compatibility Issues
- Transponder Performance with Echo-Suppression / StefanNaerlich
(Joachim Wollweber)
IP19 / L-Band Compatibility Issues
- Time to Acquire of DME/TACAN / Stefan Naerlich
(Joachim Wollweber)
Agenda Item 6c): Signal and compatibility issues in the band 5000 to 5150 MHz
WP15 / Coordination threshold to protect MLS from AMS(R)S transmitting space stations in the band 5 030-5 091 MHz / Stefan Naerlich
(Hugues de Bailliencourt)
Flimsy 17 / Draft ICAO input to ITU WP5B on protection of MLS from AMS(R)S transmitting space stations in the band 5 030-5 091 MHz / (Hugues de Bailliencourt)
Agenda Item 6d): GNSS signal and interference issues
WP18 / On-board mitigation of GNSS interference / Stefan Naerlich
(Winfried Dunkel)
IP24 / GNSS Repeaters / Ken Ashton
(Steve Mitchell)
IP29 / Excessive Interference at Newark Liberty International airport (EWR) / Leo Eldredge
WP12 / Terrestrial GNSS radiator issues
-Draft letter to States concerning terrestrial GNSS radiator issues / Stefan Naerlich
(Winfried Dunkel)
IP38 / Presentation on LightSquared / Leo Eldredge
(Robert Frazier)
Flimsy3 / Updated letter on GNSS interference issue / Stefan Naerlich
(Winfried Dunkel)
Flimsy3, rev. 1 / Updated letter on GNSS interference issue
– proposed revisions by on SSG member / (Robert Witzen)
Flimsy3, rev. 2 / Updated letter on GNSS interference issue
– proposed revisions agreed by SSG / (SSG rapporteur)
Agenda Item 6e): 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
WP44, rev.1 / Review of GNSS Manual – Sections for Review by SSG / Secretary
(Ross Bowie)
Flimsy 13 / Proposed modifications related to GLONASS spectrum in the GNSS Manual / Vladimir Korchakin
(Vladimir Kurshin)
WP07 / Sub-group on RF planning criteria in the Aeronautical Communications Panel / Secretary
(Robert Witzen)
WP08 / Typical RF characteristics of Radio Altimeters manufactured in Russia and used on civil aircraft / Vladimir Korchakin
(Mikhail Markelov)
IP39 / Study of Radar Altimeter Susceptibility to RFI in the band 4.2 to 4.4GHz / Leo Eldredge
(Robert Frazier)
IP27 / The new DEMETER software for PBN infrastructure assessment / P. Salabert
(Gerhard Berz)
II. Results of the Discussions
Agenda Item 6a): Signal and compatibility issues in the in the band 108 to 117.975 MHz
WP16,”Compatibility study between GBAS VDB link and ILS/VHF COM”
6a1) WP16 presents preliminary results of frequency compatibility measurements conducted in the frame of task T024 of the SESAR 15.3.6 project. The goal of this task is to provide frequency coordination criteria for GBAS-to-ILS and GBAS-to-VHF Com to be included in ICAO Annex10. Laboratory measurements with certified ILS and VHF COM receiver interfered by GBAS VDB transmitter as well as GBAS VDB receiver interfered by ILS and VHF COM transmission were performed. Furthermore the SSG was informed that the goal is to complete the ongoing measurements in the coming months and to present a final proposal of such criteria taking into account feed-back by the SSG for the subsequent meeting of ICAO NSP.
IP08, “Measurement results of the compatibility between GBAS VDB with ILS and VHF COM”
6a1) In support of WP16, IP08 presents more details on the test methodology, the measurement setup the pass/fail criteria as well as the obtained results. The contents of WP16 and IP08 were discussed in combination. The SSG agreed on the following feed-back:
· The appropriateness of the applied SINAD degradation threshold of 1 dB for VHF COM should be discussed with the suitableICAO ACP group
· The applicability of a cross-polar isolation value of 10 dB was considered questionable. The SSG agreed that (until further evidence is presented what other value is appropriate) the cross-polar isolation value shall be set to 0 dB in the calculation of the separation distance. A note shall be inserted into the GBAS VDB protection criteria requirements section in ICAO Annex 10 explaining that the value may change in the future if further evidence is available.
· The term “safety margin” used in WP16 and IP08 shall be renamed to “equipment variation margin” and should be explained as “margin to account for the variation of equipment characteristics with respect to the limited number of tested equipment typed in the context of the derivation of the frequency coordination criteria”.
· A common value of 6 dB shall be used in lieu of the proposed values for the safety margin which was 10 dB for the co-channel and 6 dB for adjacent channel case.
· Until further evidence supporting the need of a change of the propagation model is presented the model proposed in WP16 and IP08 was deemed appropriate.
Action SSG18/1: SSG rapporteur to arrange with ICAO ACP secretary the review of the appropriate SINAD degradation threshold to derive the protection criterion of VHF com against interference by GBAS
WP05, “Interference into ILS-Localizer and VOR monitor systems”
6a3) WP05 has been prepared in response to requests from the ICAO NSP to analyze the interference susceptibility of broadband VOR and ILS monitor systems and addresses such interference that can be cause by transmissions from VDL Mode 4. The paper concludes that the worst case separation distance based on a channel loading of 20 % required between a VDL Mode 4 transmitter and an ILS monitor antenna is 175 metres. Since this is approximately equal to the distance between the runway end and the ILS near field monitor antenna for normal siting of the ILS localizer no impact to the ILS localizer monitors is expected. For VOR monitors the worst case separation distance based on a channel loading of 20 % between a VDL Mode 4 transmitter and aVOR monitor antenna is 150 metres. Since there is no protection area standardised by ICAO this may require special measures on a national basis.
6a4) The SSG agreed with the findings presented in WP05. During the discussion it was emphasised that the attention of States should be drawn to the potential of interference by into ILS or VOR monitor systems and, when assigning radio frequencies within or nearby the band 108 – 117.975 secure that no harmful interference is caused to ILS or VOR monitor systems. The SSG agreed that the appropriate means for this is a note to be inserted into the ICAO document to be developed containing the frequency coordination criteria for aeronautical systems in Vol. II of the ICAO RF Handbook, Doc 9718.
Action SSG18/2: Robert Witzen to insert a note into Vol. II of the ICAO RF Handbook, Doc 9718.
to make States aware on the potential of interference into ILS or VOR monitor systems
WP06, “Assessment of built-in system mitigations against erroneous tuning in VDL Mode 4”
6a5) WP06 has been prepared in response to queries raised by the NSP on the presentation of frequency planning parameters covering the operation of VDL Mode 4 equipment in the frequency band 112-117.975 MHz. The goal of the paper is to investigate the failure modes leading to the potential of erroneous tuning.
6a6) The failure mode analysis presented herein shows that the level of resilience built into the current specification provides sufficient mitigation to prevent for erroneous tuning of VDL Mode 4 to avoid harmful interference into navigation systems operating in the frequency band 112 to 117.975 MHz. This paper therefore identifies each possible cause of erroneous mistuning under normal operation and assesses the ability of the inbuilt functions to mitigate cases of erroneous tuning. These functions are (described in details in Appendix B of WP06):
- Periodic repeat transmissions
- Quarantining of ground tuning instructions
- Error detection algorithm
- Channel sensing
- System timers
- Autotune (detection of missed transmissions by the ground station on the expected frequency)
6a7) These functions a standardised in the ICAO Manual on VHF Digital Link (VDL) Mode 4, ICAO Doc 9816, AN/448, 1st Ed. 2004 and in the ETSI European Norms for VDL Mode 4 ground and airborne equipment (EN 301 and EN302)
6a8) The SSG agreed that the current provisions for VDL Mode 4 related to potential erroneous tuning of the (airborne) VDL Mode 4 transmitter are adequate to prevent harmful interference to navigation systems operating in the frequency band 112 – 117.975 MHz.
IP04, “VDL Mode 4 channel loading”
6a9) IP04 was presented in response to a request by ICAO NSP / SSG on channel loading values for VDL Mode 4. The material in this paper provides channel loading values that are to be considered in the testing of VDL Mode 4 for developing frequency assignment planning criteria when VDL Mode 4 is to be considered as interferer station. This material was agreed at ACP WG B 17 in 2004 and was based on input provided by Eurocontrol. The full paper “Updated plan for frequency testing of VDL Mode 4 for the development of frequency planning criteria is available as Appendix G to the ICAO ACP WG B17 report and can be downloaded from
WP04, “Measurement of antenna isolation on a small aircraft”
6a10) WP04 has been prepared in response to requests for additional information on the achievable antenna isolation on small aircraft Such information was requested to assess, in general, the feasibility of implementing VDL Mode 4 on smaller aircraft.
6a11) The SSG was reminded that an antenna isolation of at least 45 dB would be required to install VDL Mode 4 on an aircraft, which may be hard to achieve on small aircraft. The value of 45 dB is based on the measurement results that were presented to ICAO in 2008 and 2009. These measurements were taking place with a VDL Mode 4 channel loading of 20% in order to present a stable level of interference into the measured ILS and VOR receivers. In practice, VDL Mode 4 cannot operate with a channel loading more than 2.7% which would require a higher level of interference from VDL Mode 4 into ILS or VOR before it can become harmful.
6a12) The data presented is related to the isolation between on-board VHF COM antennas and NAV antennas used for the reception of ILS and VOR signals. The measurement results show that in all cases the achieved isolation is better than 45 dB and antenna isolation of between 50 and 60dB can be achieved, in particular when the VDL Mode 4 antennas are installed on the opposite side of the aircraft where the NAV antennas are installed. According to WP04 the implementation of VDL Mode 4 on a small aircraft can be considered to be feasible. It is expected that on larger aircraft, better isolation factors are achievable.
6a13) The SSG noted the information presented in this paper in addition to the considerations that were given in working paper NSP Nov 09 WGW/WP13.
WP09, “SUKHOI RRJ-95 transmitter-to-receiver isolation between VHF COM and VOR/ILS(LOC) equipment
6a14) WP09 was presented in response to action item 5 of SSG meeting in March 2009 which requested measurement results on transmitter-to-receiver isolation achievable on medium, small and light aircraft for VDL Mode 4 compatibility studies. This Working Paper presents such data collected recently during certification testing of medium-sized Sukhoi RRJ-95 regional airplane.
6a15) WP09 concludes that the minimal value of transmitter-to-receiver isolation on medium-sized Sukhoi RRJ-95 aircraft may run as low as 50 dB for VHF COM – ILS(LOC) equipment. These values can be compared with isolation valuesof 60 dB for large aircraft and 40 dB for small and light aircraft. Furthermore it was pointed out in this WP that the Airworthiness Requirements now in force in the Russian Federation requires the isolation shall be greater than 35 dB regardless of aircraft category.
6a16) During the discussion of WP04 and WP09 it was clarified that the results of isolation measurements contained in both papers include aircraft cable losses.
Agenda Item 6b): Signal and compatibility issues in the band 960 to 1215 MHz
WP27,“L-Band Compatibility Issues - Questions on DME/TACAN Characteristics”
6b1) WP27 made the SSG aware, that during work in the European ICAO Frequency Management Group (FMG) on refining DME/TACAN frequency coordination criteria and in the context of developing sharing criteria between TACAN and LDACS in ITU WP5B a number of unclear or missing definitions in ICAO-Annex 10 were identified. Although some of the missing definitions may be found in RTCA/EUROCAE MOPS, these identified items may require clarification and standardization by ICAO to ensure identical performance of equipment, independent of the MOPS or Organization that maintains it. WP27 contains the index to the items identified which will are covered in a number of separate papers WP28 to WP35 as well as IP19 and IP20.
6b2) In the discussion of the aforementioned set of papers on L-band compatibility issues members of the group emphasized that the standardisation of LDACS by ICAO and the development of frequency coordination criteria for LDACS has not yet started. However, the SSG considered the presented material as useful for the future analysis of the compatibility of DME/TACAN with LDACS in case that LDACS is proposed to ICAO as a communication system to be incorporated into Annex 10.
6b3) It was also pointed out that some of the presented issues are already adequately addressed in standards by RTCA and EUROCAE which may be used as reference documents in ITU studies. It was additionally mentioned that ICAO focuses on the interoperability of aviation equipment and does not necessarily provided detailed guidance to equipment manufacturers.
IP20, “L-Band Compatibility Issues - Update of the DME/TACAN RFI compatibility characteristics”
6b4) IP20 contains a paper dealing with the compatibility between LDACS and DME/TACAN which had been presented to the ECC CPG PTC- 10 meeting in Vilnius (Lithuania) in April 2011.It is pointed out in this paper that TACAN transponders and interrogators differ very much in design, receiver sensitivity, RF-selectivity and components required (interrogator provide bearing processing circuits while transponder requires a monitor receiver, Short and Long Distance Echo Suppression).
6b5) Furthermore, it was emphasized that to date no prototype model of LDACS transmitter are available to prove the spectrum assumptions currently discussed in ITU WP5B are achievable, and to be able to conduct measurements on a sufficient number of representative number of TACAN interrogator and transponder for the various designs still in use after 2016 no conclusive estimation is possible. Furthermore no specification of the operational use of LDACS is available.
6b6) Recent studies in Germany seem to prove that the sharing studies currently discussed in ITU WP5B do not account for many characteristics of real DME/TACAN receivers which may make them more susceptible to interference by LDACS.
WP28,“L-Band Compatibility Issues - Characteristics of the Identification Signal of DME/TACAN”
6b7) WP28 addresses the characteristics of the Identification Signal of DME/TACAN. It made the SSG aware, that while interrogator originally provided the received identification of transponder as audible Morse-code, newer interrogators detect the Morse code automatically and provide the information also via ARINC-429 Bus to the FMS. While FAA TSO-66 specifies that the audible ID shall be readable in the presence of interfering signals, no guidance specifies the interference susceptibility of the digitally decoded ID. The SSG considered this as an operational issue and could therefore not agree to develop a change proposal to ICAO Annex 10 based on the observed shortcoming of existing regulations.
WP29,“L-Band Compatibility Issues - DME/TACAN Interrogation Repetition Frequency (IRF)”
6b8) WP29 addresses the dependence of Interrogation Repetition Frequency (IRF) on various DME interrogator designs. It made the SSG aware, that most interrogators show a much higher sensitivity than specified in ICAO Annex 10 (4 to 18 dB were measured during a first set of tests). As a consequence the transponder interrogation load (pp/s) generated by a larger number of such interrogators is much higher than accounted for in the 5% search at 150 pp/s and 95% track with 30 pp/s, if interrogator that initiate interrogations well below the defined signal levels are unsuccessfully initiated and not successfully conclude.