ACP-WGF20/WP-19
19 March 2009
International Civil Aviation Organization
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 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 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)
WP11
Modelling the unwanted emission characteristics of MLS
WP4
MLS Implementation in the Russian Federation
Flimsy 1, rev.3
Flimsy 2
“Response to WP4 request (by ITU for information on MLS)”
“MLS unwanted emission characteristics in the band 50105030 MHz” (Power Point Presentation)
“Request for clarifications on WP 11 `Modelling the unwanted
emission characteristics of MLS´ and alternate MLS DPSK
Spectrum roll-off derivation”
“MLS spectra measured by LVNL – Levels at 3 different offsets
from centre frequency”
MLS characteristics – extract from draft Volume 3 of ICAO Doc
8071”
List of potential European MLS locations according to responses to a
State letter by ICAO (Microsoft Excel-File)
Flimsy 3, rev.2
Flimsy 4
Flimsy 5
Flimsy 8
Page 1/17
ICAO secretariat
(Alessandro Capretti)
Stefan Naerlich
(Felix Butsch)
Vladimir Korchagin
(Mikhail Markelov)
Jules Hermens
(Alain Delrieu)
(Alain Delrieu)
(Alain Delrieu)
(Alain Delrieu)
ICAO secretariat
(Alessandro Capretti)
Flimsy 9
Flimsy 10
Flimsy 12
Flimsy 13,
rev.1
Determination of expected MLS Power Flux Density at the lower
band edge at 5030 MHz (Microsoft Excel-File)
Vertical antenna pattern of MLS DPSK signals from EUROCAE
Ground Equipment MOPS (ED-53)
MLS DPSK Duty Cycle
Proposed Modifications to Flimsy 9 –“ Determination of expected
MLS Power Flux Density at the lower band edge at 5030 MHz”
(Microsoft Excel-File)”
(Alain Delrieu)
(Alain Delrieu)
Jules Hermens
(Robert Frazier)
Agenda Item 6b): Navigation data links in the band 108 to 117.975 MHz
WP5
WP3
WP8
WP7
WP15
Flimsy 6
“Use of the band 112 – 117.975 MHz by VDL Mode 4
- Review of the comments provided by the SSG”.
“Experimental data on VHF COM – VOR/ILS Transmitter-toReceiver Isolation in the 108 – 137 MHz Band for medium-sized
aircraft”
“Work plan to establish the potential number of assignable GBAS
frequencies in the frequency band 117.975 – 137 MHz”
“Analysis of apparent discrepancy between the test points specified
in ITU-R Recommendation M.1841 and the ICAO specification for
the GBAS DOC
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)”
“VHF COM – VOR/ILS Transmitter-to-Receiver Isolation in the
108 – 137 MHz Band”
ICAO secretariat
(Robert Witzen)
Vladimir Korchagin
(Mikhail Markelov)
Ken Ashton
(Steve Mitchell
Ken Ashton
(Steve Mitchell)
Tim Murphy
Vladimir Korchagin
(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
Page 2/17
Bruce DeCleene
(John Tepper)
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” <Alain Delrieu>
6a4) Flimsy 3 discussed shortcomings of the model for the emission characteristics of MLS presented
in WP 11. Furthermore, Flimsy 3 presented the derivation of an alternative model. A table
containing a comparison of measured MLS emission levels at various offsets from the centre
frequency (150 kHz to 1.5 MHz) with the models in WP11 and Flimsy 3 proves that the model in
Flimsy 3 fits well with the measured spectra of LNVL (see Flimsy 4) and the spectrum
specification Draft Vol.3 of ICAO Doc 8071 (see Flimsy 5).
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)
b) The calculated MLS power flux density at the band edge at 5030 MHz as contained in the
Spreadsheet in Flimsy 13 rev.1
Page 5/17
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 Be200 operated in Russia, WP3 comes to the conclusion that for medium-sized aircraft transmitterto-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
additional data relevant to transmitter-to-receiver isolation between VHF COM and VOR/ILS
onboard installations in particular on medium, small and light aircraft.
Page 6/17
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.
(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.
Page 7/17
(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:
 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
Page 8/17


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.
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.
Page 9/17
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 radiocommunication 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
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 112117.950 MHz band without withdrawal of conventional Navaids in some parts of Europe. It was
Page 10/17
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 soundbroadcasting 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.
Agenda Item 6f): Open actions for the SSG from the ICAO NSP Working Group 1 meetings
Page 11/17
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 feedback 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
number
Actions from the Montreal meeting October 2005 (SSG8):
SSG8/2
Present results of FMG on improved
DFS
coordination criteria for conventional
nav aids to SSG.
SSG8/5
Prepare text for the RF handbook on
Secretariat
potential interference to GNSS by
commercial broadcast
Actions from the Brussels meeting May 2006 (SSG9):
SSG9/14
To investigate the basis for the
SSG
derivation of the interference limit value
of -94.5 dBW/m2 as applicable to MLStype interference.
SSG9/15
To undertake measurements to
France
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
reason for “discontinuities” in the DME
propagation curves.
SSG10/8
To provide results of GBAS vs. ILS
Christophe
bench tests carried out by STNA in
Dehaynain
2004.
(France)
SSG10/9
To present bench test results to
SSG
determine the interference threshold of
VHF COM and ILS against GBAS
signals.
SSG10/10
To develop more detailed frequency
SSG
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
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
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.
Status
Ongoing
(see SSG/10, IP2)
Open
Closed by Flimsy 5 to SSG/14
Open
Ongoing
Open
Open
Open
Open
Open
Actions from the Delhi meeting March 2007 (SSG11):
SSG11/x
SSG11/2
To present a proposal of detailed
guidance material on DME coverage
volume to be included in a new volume
of the ICAO RF-handbook, ICAO DOC
9718.
To present a proposal of detailed
guidance material on VOR coverage
volume to be included in a new volume
of the ICAO RF-handbook, ICAO DOC
9718.
DME/VOR
coverage ad-hoc
group
Open
DME/VOR
coverage ad-hoc
group
Open
Page 13/17
Actions from the Montreal meeting March 2008 (SSG12):
SSG12/a
SSG12/4
SSG12/6
SSG12/7
To support adequate protection of
GLONASS within an RTCA Special
Committee which works on RTCA DO210D.
To present the information contained in
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.
To carry out measurements of the
susceptibility of aeronautical receivers
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.
To keep SSG informed about the latest
results of discussions of the compatibility between digital broadcast and
aeronautical systems in the VHF band.
SSG members
Ongoing
France
Ongoing
SSG members
Open
Partly fulfilled by IP9 of SSG13.
SSG members
Open
Actions from the Montreal meeting October 2008 (SSG13):
SSG13/1
SSG13/2
SSG13/3
SSG13/5
SSG13/6
SSG13/7
To present a paper on “Joint use of the
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.
To analyse the apparent discrepancy
between the test points specified ITU-R
Recommendation M.1841 and the ICAO
specification for the GBAS DOC.
To present a revised version of the WP
“Use of the band 112 to 117.975 MHz
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.
To provide measurement results of DME
spurious emissions in the RNSS bands
(GPS L5, Galileo E5, Glonass L3 band)
to establish the need for a change of
DME MOPS.
To present the Flimsy1 containing the
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.
To present a work plan to establish the
number of potentially achievable
ICCAIA
Open
UK
Accomplished by WP7 of
SSG/14
Robert Witzen
Open, Partially fulfilled by WP5
to SSG/14
SSG members
Open
UK
Completed
UK
Closed by WP8 to SSG/14
Page 14/17
SSG13/8
SSG13/9
additional frequency assignments for
GBAS, if using the VHF communication
band.
To present at a future NSP meeting an
analysis of the impact of the change of
GNSS antenna specification for the linkbudget.
To propose a short additional text for
ICAO Annex 10, Vol. I, Attachment C,
recommending that in frequencycongested 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.
SSG members
Open
Germany
Open
Actions from the Bretigny meeting March 2009 (SSG14):
SSG14/1
SSG14/2
SSG14/3
SSG14/4
SSG14/5
SSG14/6
SSG14/7
SSG14/8
SSG14/9
SSG14/10
SSG14/11
To compile and present all information
on the timing schemes of the various
MLS signals which contribute to the
DPSK transmission duty cycle.
To compile all relevant information on
MLS characteristics from ICAO Annex
10 to present it to March meeting of
WG/F.
To clarify the azimuth pattern of the
MLS DPSK signal (coverage and
variation wrt. azimuth angle)
To compile all information on MLS
characteristics to be provided to ICAO
ACP WG/F
To provide measurement results on
transmitter-to-receiver isolation
achievable on medium, small and light
aircraft for VDL Mode 4 compatibility
studies.
To ask CSG to provide the reference
document containing the derivation of
the allowable GBAS VDB message error
rate requirement.
To provide further test results of VDL4
compatibility studies
To present a WP to a future SSG
meeting addressing the interference
threat between VDL-4 and VOR as well
as ILS monitors.
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.
To provide the Oct. 2009 meeting of
SSG material solution of the issue of the
proposed revision of the GNSS antenna
specification in ICAO Annex 10.
To carry out compatibility
measurements between digital soundbroadcasting in the band of about 87-108
Jules Hermens
Closed (Flimsy 12)
Alain Delrieu
Open
Jules Hermens
Open
Alessandro
Capretti
Open
SSG members
Open
Andreas Lipp
Open
Robert Witzen
Open
Gerhard Berz
Open
UK
Open
Eric Chatre
Open
SSG members
Open
Page 15/17
SSG14/12
SSG14/13
MHz and aeronautical services in the
band 108-117.975 MHz and to
contribute to the development of
protection criteria.
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.”
SSG members To try-out the test-version
of new IF77 software and provide feedback to FAA
Secretary
Open
SSG members
Open
Page 16/17
ATTACHEMENT B: LIST OF PARTICIPANTS OF THE SSG
Name
Attendance
Organisation
Telephone
Email
Alain Delrieu
F
ICCAIA (ICR)
+33 6 0863 9565
adedel@yahoo.fr
Alessandro Capretti
P
ICAO Secretariat
+1-514-954-5847
acapretti@icao.int
Andreas Lipp
F
EUROCONTROL
+33 (0)1 6988
7618/7307
andreas.lipp@eurocontrol.int
Benoit Roturier
P
DGAC/DSNA,
France
Erwan LE HO,
F
ICCAIA (Thales
Alenia Space)
+33(0)5 3435 5886
erwan.le-ho@thalesaleniaspace.com
Felix Butsch
F
DFS, Germany
+49 6103-707-1533
Felix.Butsch@dfs.de
Gerhard E. BERZ
P
EUROCONTROL
+32 2 729 3734
gerhard.berz@eurocontrol.int
Ian Mallett
P
Civil Aviation
Safety Authority,
Australia
Jeffrey Bollard
p
Airservices
Australia
John Tepper
P
FAA, USA
Jules Hermens
P
Netherlands Civil
Aviation Authority
Airnavigation
State Scientific &
Research Institute,
Russia
Geyser Scientific
& Production Co.
Russia
Benoit.roturier@aviation-civile.gouv.fr
Ian.mallet@casa.gov.au
+61-262684949
Jeffrey.Bollard@airsevicesaustralia.com
John.Tepper@faa.gov
+31 70 456 3268
Jules.Hermens@ivw.nl
+7(495)-490-95-84
Markelov@atminst.ru
+7(495) 784-63-30
Shienok@geyser.ru
Mikhail Markelov
F
Nikolay Shienok
F
Robert Frazier
F
FAA, USA
+1-202-267-9722
Robert.Frazier@FAA.GOV
Robert Witzen
F
ICAO Technical
Advisor
+1-514-4267654
r.witzen@videotron.ca
Steve Mitchell
F
NATS, UK
+44-1489-444646
Steve.mitchell@nats.co.uk
Note: P/F = Part time/Full time attendance
Page 17/17