report of 13th meeting of wg m · web viewthe ils localizer is frequency paired with the glide path...
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Report of 13th Meeting of WG M
International Civil Aviation Organization
REPORT
ACP-WG-M-13 2008-11-21
Aeronautical Communications Panel (ACP)
WORKING GROUP M
Montreal
18-21 November 2008
REPORT OF THE THIRTEENTH MEETING
The meeting was opened at 1000 on 18 November 2008 by Mr. Robert Frazier, Convener, WG-M. He welcomed the participants. Following introductions, the ACP WG M Secretariat, Mr. Vaughn Maiolla gave ICAO Hq logistics information, and working hours.
The agenda (Annex 1) was adopted. At the request of one of the participants, it was agreed to delay consideration of Agenda Item 2 until Thursday. The attribution of documents to each Agenda Item was as follows: AI 1: WP/5, 6, 7, 8, 9, and 10 and IP/1, 2, and 3. AI 2: WP/3, 4, 5, 20, and 21, IP/5. AI 3: WP/11, 12, 13, 14, 15, 16, 17, 18, and 19, IP/4. Annex 2 is list of input documents.
1.Status of on-going data communications programs
1.a.FAA data communications, program status and activities.
IP 2.Data Communication Programme Status. Peter Muraca presented IP 2. This paper highlighted the FAA program’s current state and on-going activities relative to the Final Investment Decision (FID) phase of the program. The status brief concentrated on the scope of FID activities and products, as in specification development, plans for avionics strategy, plans for prototype / test, and plans for Screening Information Request for air / ground subnetwork and automation.
1.b.Eurocontrol data communications, program status and activities
WP 5ATN Datalink Implementation in Europe. Danny Van Roosbroek presented WP05, which discusses the current status of data link deployment in Europe, noting especially the approval of a legally binding implementing rule in the framework of the Single European Sky regulations. It was highlighted that ATN/OSI implementation in the air-ground environment will soon become a legal requirement for air navigation service providers and aircraft operators in Europe. The key dates in the Data Link Implementing Rule are:
1st Jan 2011:After this date all new aircraft operating above FL 285 must be delivered with a compliant system.
7th Feb 2013:By this date all LINK Region Air Navigation Service Providers (ANSPs) must have implemented an operational compliant system.
7th Feb 2015:By this date all aircraft operating above FL285 must have been retrofitted with a compliant system.
7th Feb 2015:By this date all EU Region ANSPs must have implemented an operational compliant system.
31st Dec 2017:Aircraft which are at least 20 years old and which will cease operation in the concerned airspace before 31 December 2017 are exempt.
1st Jan 2014:Aircraft with individual airworthiness certificate before this date that are equipped with Future Air Navigation System (FANS) are exempt for the lifetime of the aircraft. Aircraft entering into service after 1 January 2014 shall comply with the rule.
1st Jan 2014:State aircraft should comply with the rule if equipped with non-military data link.
The working group was invited to note the information provided and ensure the ongoing support of the referenced ICAO SARPs and Manuals for ATN/OSI.
IP 1.LINK 2000+ UpLink 11 Newsletter. This paper contains more detailed information on the European Link2000+ program including its Link Integration Team, the Operational Focus Group, and the Test Facility at the Eurocontrol experimental centre.
1.c.Present information on VDL Mode 4 radio tests in the band 112-118 MHz
WP 6.AMENDMENTS TO VDL MODE 4 SARPS CONSEQUENTIAL TO THE ALLOCATION OF THE BAND 108-117.975 MHZ TO THE AERONAUTICAL MOBILE (R) SERVICE BY THE ITU WORLD RADIOCOMMUNICATION CONFERENCE 2007. Mr. Robert Witzen presented WP 6 which contains, in its Appendix 2, proposed changes to Annex 10 needed to align Annex 10 with frequency allocation changes adopted at WRC 07. The recommendations were approved, and the Secretary agreed to post them on the ICAO web site. The Secretariat will secure agreement by correspondence, and schedule a State Letter by June 2009.
WP 7.AMENDMENTS TO THE ICAO RF HANDBOOK ON RADIO FREQUENCY SPECTRUM REQUIREMENTS TO INCORPORATE ICAO STUDIES ON COMPATIBILITY BETWEEN VDL MODE 4 AND FM BROADCASTING. Mr. Robert Witzen presented WP 7. The meeting was invited to review the proposed amendments to the ICAO Handbook on radio frequency spectrum requirements for civil aviation (Doc. 9718) as in Appendix 1. He stated that this paper was presented to ACP WG F (WP 6, 7 to that meeting). He stated that WG F agreed that since interference to FM receivers would be transient in nature, that it would not be considered “harmful” based on the ITU definition of harmful interference. He also mentioned that (type B) interference to VDL Mode 4 would occur up to 1 Km from a 100 KW FM station. He acknowledged that type A1 (from transmitter spurious) is a problem and some form of suppression would be required. The paper was also submitted to ITU-R WP 5B and SG 6. The proposed changes were approved after some modifications proposed by the meeting were included. presented
WP 9.FREQUENCY ASSIGNMENT PLANNING CRITERIA FOR VDL MODES 2, 3 AND 4.
Mr. Robert Witzen presented WP 9. This paper presents the results of the review of the frequency assignment planning criteria for VDL Mode 4, as was agreed at ACP WGM/12 (June 2008). The material relating to VDL frequency assignment planning in this appendix is intended to be published in the ICAO Handbook on radio frequency spectrum requirements, Doc. 9718 in an appropriate format. ICAO Regions should be invited to include this material in their frequency planning process. Appendix 1 contains material for incorporation in Volume II of the Handbook. Appendix 2 contains relevant updates to the material on the band 117.975 – 137 MHz in the Handbook. Mr Witzen presented that material in some detail, and one change suggested by the meeting to Appendix 2 was incorporated. The meeting approved the modifications and the proposal to place the Appendix 1 material into a new Volume II of the Handbook.
WP 10.Use of the band 112 – 117.975 MHz by VDL Mode 4, Results of tests and frequency assignment planning criteria. Mr Robert Witzen presented WP 10. In response to a question from the group, Mr Witzen stated that no flight testing of VDL Mode 4 has been done in the navigation band. He also stated that the tests with GBAS as an interference source would have to be redone since the GBAS interference source used for the tests simulated a CAT I GBAS transmitter, not a full GBAS transmitter, which would transmit a higher pulse rate. In response to the NSP/SSG comment that ICAO is to do a safety assessment, Mr. Witzen, after further investigation, found that such an assessment is a State responsibility. The meeting was invited to review the proposed frequency assignment planning criteria in Section 7 of the report and in particular to provide comments on the frequency assignment planning criteria that will protect VDL Mode 4 from harmful interference from navigation systems. Mr Witzen stated that this paper was presented to the October 2008 meeting of the NSP Spectrum Subgroup. They did not accept the paper and made several comments and suggestions for additional work, which is reproduced in Appendix 4 of this paper. The meeting was invited to provide any comment on the observations from the SSG as in Appendix 4. The meeting was invited to note that an updated version of this paper will be submitted to the next WG M meeting. It will include a response to the critique by NSP/SSG. A request was made by Mr Witzen to schedule the next meeting of WG M to occur after the next meeting of the NSP/SSG, so that WG M could benefit from the further comments from the SSG on the (as yet unwritten) revised version of this paper
1.d.Present information on VDL Mode 4 and IPS.
WP 8.INTRODUCTION OF IPS IN VDL MODE 4 . Robin Hughes presented WP08, Introduction of IPS in VDL Mode 4. This paper presents a brief overview of ongoing activities towards the implementation of the ATN/IPS SARPs and guidance material in VDL Mode 4. The paper highlight that no amendments are foreseen to the standards as a result of introduction of IPS other than editorial changes where only the OSI protocol is mentioned today. Sweden (LFV) envisage that a validation activity will have been completed by the end of 2009. Comments regarding the SES IR for datalink services were discussed and the implication of compliance to ED120 and DO178B agreed.
IP 3.Requirements for Single European Sky Data Link Services. IP 3 contains Draft SES Implementing Rule for Data-Link Services. Danny Roosbroek highlighted the text in Annex IV, Part D which specifies the communication protocols for transmission and reception of bit frames between ground and aircraft communication systems.
2.Complete new ATN/OSI Manual, DOC 9880
2.aTransfer remaining material of global implementation relevance from DOC 9705 (to be discontinued)
WP 2.COMPLETION OF DOC 9880 Part IVA – ATN Directory. Working paper 2 discussed the detailed technical specifications for the ATN Directory and proposed some updates resulting from a detailed review of the draft material provided at the 12th meeting of ACP WG M. A small breakout group discussed some of the issues raised and agreed on updated text.
Action Item:Mr Danny Van Roosbroek and Mr Jean-Marc Vacher agreed to provide an updated revision marked document to the ICAO secretary as soon as possible. This would then be published on the ACP website as Draft Doc 9880 Part IV.
The ICAO secretary was asked to investigate the possibility of reproducing the text of Withdrawn ITU-T Recommendations X.583 and X.584 on the ACP website for reference.
WP 4.COMPLETION OF DOC 9880 Part III – ATN/OSI Internet Communication Service (ICS). Working paper 4 discussed the current state of the detailed technical specifications of the ATN/OSI Internet Communication Service (ICS) and proposed that the mature draft material provided at the 12th meeting of ACP WG M should be approved for publication on the ACP website as soon as possible. The working paper identified parts of the ICS provisions that are no longer required, and Mr Jean-Marc Vacher confirmed that a similar analysis in France had reached the same conclusions. Air-ground IDRP Security was identified as an additional candidate for removal.
Action Item:Mr Danny Van Roosbroek and Mr Tom McParland agreed to provide an updated revision marked document to the ICAO secretary as soon as possible. This would be published on the ACP website as Draft Doc 9880 Part III Chapter 3.
IP 5Status of the MESANGE AMHS Implementation Project Jean-Marc Vacher presented IP 5. This paper informed the meeting about the status of the MESANGE AMHS Implementation Project which is currently underway in France and in Switzerland. Mr Vacher urged the group to support the expeditious publication of the already approved ATSMHS detailed technical specifications in Doc 9880 Part IIB
Flimsy 1Directory schema - atn-facilityName attribute is too short. Jean-Marc Vacher presented the paper. It proposes to modify the Directory Specification Section 7.5.3.9. The meeting accepted the proposal and it is presented Annex 18.
2.b.Introduce A/G security standards into ICAO DOC 9880
WP 3COMPLETION OF DOC 9880 Part IVB – ATN Security for AMHS. Working paper 3 discussed the current state of the detailed technical specifications of ATN Security specific to the ground-ground AMHS environment, and proposed that selected material from Doc 9705 SV8 should be published as Draft Doc 9880 Part IV-B as soon as possible. This was approved by the meeting
WP 20Approach for Air-Ground Security in Doc 9880. Tom McParland presented WP 20. This paper proposes incorporating air-ground security provisions into Doc 9880 using the IETF Internet Key Exchange version 2 (IKEv2) protocol for key establishment in place of the Doc 9705 procedure using Context Management. This would be the same air-ground key establishment method specified in Doc 9896 for the ATN IPS. This paper also proposes using a “Secure Mode” application approach which adds an authentication tag to application messages in place of the Doc 9705 procedure where security is in the Upper Layer Communication Service (ULCS). Eurocontrol indicated that they want time to review this proposed method before formally accepting. However, Mr. Van Roosbroek did say that he had no opposition to this approach. Since this applies to air-ground link, he recommended that security modifications to Doc 9880 focus on the ground to ground security requirements first and leave the air to gound security to later. Mr Patel indicated that the DataComm Program will not implement air-ground security until the Program’s Segment 2 time frame, which is anticipated to be 2017.
Action Item:In response to a request from the group, Mr McParland agreed to submit a paper comparing various cryptographic security methods.
WP 21Security changes in Doc 9880. Vidyut Patel presented WP 21. There was agreement that these security provisions are desirable. A question was raised about whether incorporation of the proposed air-ground security provisions into Doc 9880 would delay its publication scheduled for late 2009. Mr Patel indicated since these provisions are needed for Segment 2, priority will be to develop the ground-ground provisions and then the air-ground provisions.
3.Maintenance activities for VDL Mode 2 (ICAO DOC 9776)
3.a.This material is a result of on-going activities within AEEC 631 DLK for VDL Mode 2 implementation characteristics
WP 19.PROPOSED AMENDMENTS TO DOC 9776. Mr Rob Morgenstern presented WP 19. This working paper, along with the proposals in WP 11-18, provides proposed amendments to Doc 9776, the Manual on VDL Mode 2 to harmonize the document with the recently approved Supplement 5 of AEEC Specification 631 that corrected a deficiency in the existing standards with respect to operating VDL Mode 2 on multiple frequencies. Mr Morgenstern invited the meeting to consider the amendment proposals to Doc 9776 that are presented in Working Papers 11 thru 18 and develop a schedule for producing an updated edition of Doc 9776 including the changes approved at AMCP/8. He recommended that the approved changes be put on the ICAO web site for all to review. This would entail minimal cost. He acknowledged that editing and printing of an updated document 9776 would be costly. He indicated that further development including flight testing may result in additional changes. The Secretariat indicated that ICAO will wait until all changes are in before modifying Doc 9776. In response to a question about how these changes affect existing equipment implementation, Mr. Morgenstern stated that existing equipment will need S/W changes only, and without those changes, they will still function but may have impact upon capacity of the system. To accommodate the unmodified aircraft, the ground system will have to keep track of all users to assure that incorrect frequency tuning is not unnoticed. In the event that the aircraft system chooses a non-working frequency, the aircraft will revert back to CSC.
WP 11 Unrecognized XIDs, WP 12 Allowed/Disallowed X25 options, WP 13 Options, WP 14 Multi-Frequency Operation, WP 15 Network Identifier, WP 16 MASPS Harmonisation, WP 17 Called Line Address Modification Notification and WP 18 Broadcast aircraft address. Mr. Morgenstern presented, in order the detailed specification changes proposed in WPs 11, 12, 13, 14, 15, 16, 17 and 18. Mr Morgenstern made a few detailed corrections during his presentations. In response to a question about WP 14, Mr Morgenstern stated that these changes have not yet been flight validated. He recommended that this proposed change not be put on the ICAO web site until validation is completed. He stated that he will report on validation results at a future meeting of WG M.
4.Any other business
IP 4.Russian Integrated Wake Vortex Flight Safety System. Robin Hughes commented on progress of VDL4. Sweden will implement a certified ADS-B solution in Sweden during March 2009 and are progressing with pre-implementation of Point to Point communication using the ATN/IPS (ICAO Doc 9896) manual as per WP8 of this meeting. Russians are currently progressing with a wake vortex application based on the air to air functionality of VDL4, a presentation of this work was submitted as IP4.
Departure of WG Rapporteur. Robert Frazier advised the group that he would be unable to continue as Rapporteur after this meeting, hence it would be necessary to appoint a new Rapporteur. The Secretary took an action item to find out the correct process of appointing a working group Rapporteur and that if it was possible to do this in advance of the next meeting of WG-M, he would take the necessary steps to ensure that a Rapporteur was appointed by that time. The meeting thanked the Rapporteur for his leadership.
Tony Kerr advised the meeting that the draft of Doc 9880, Part 1 as posted on the ACP web-site was incomplete as certain items were missing, namely the description of the CMA and CPDLC applications. The Secretary took an action item to remedy this.
Action Item: Secretary to find procedure for appointment of new Chair and act upon it.
Action Item: Secretary to remedy omissions in draft of Doc. 9880
Action Item: Secretary to take steps to ensure timely posting of documents on ICAO-NET.
5.Next meeting. The next meeting will be held from April 21 thru April 24, 2009. The venue is TBD. During the discussion on this, the Secretary advised the meeting that ICAO could not fund travel for Secretariat staff to support working group meetings. Therefore unless a sponsor was found to fund the Secretary’s travel costs, all future meetings would need to take place at ICAO HQ, Montreal.
The travel limitations were generally accepted by the group however it was pointed out that this may limit the participation by Asian states, as attendance at all meetings would involve long-haul travel. Hence there was a need to hold some meetings in the Asian Region.
Action Item: Secretary to canvas support for meetings to be held in Asia to facilitate support from that Region.
.
6.Adjourn.
Attachments
Annex 1Agenda
Annex 2Attendance list
Annex 3List of input documents
Annex 4Proposed amendments to Annex 10, Volume III, Part I, chapter 6 on VDL Mode 4 as a consequence of WRC-07 changes to the Radio Regulations from WP 6
Annex 5Relevant Updates for the ICAO Handbook on the Band 108–117.975 MHz from WP 7
Annex 6Material for Incorporation in the ICAO Handbook Volume II, on Radio Frequency Spectrum Requirements for Civil Aviation (Doc. 9718) from WP 9
Annex 7Relevant Updates for the ICAO Handbook on the Band 117.975–137 MHz from WP 9
Annex 8Proposed Frequency Assignment Planning Criteria to protect VDL Mode 4 from harmful interference from navigation systems, (For review and comment only) from WP 10
Annex 9Extract from Report NSP/SSG October 2008, (for review and comment) from WP 10
Annex 10 thru Annex 17Amendments for Doc 9776 from WPs 11 thru WP 18
Annex 18Proposed Directory Service Amendment from Flimsy 1
Annex 19List of Action Items
Annex 1
Thirteenth Meeting
ICAO ACP Working Group M (Maintenance)
18-21 November 2008
ICAO Headquarters
Montreal Canada
Agenda
Introductions
1.Status of on-going data communications programs.
WP/5, 6, 7, 8, 9, and 10 and IP/1, 2, and 3.
1.a.FAA data communications, program status and activities.
1.b.Eurocontrol data communications, program status and activities
1.c.Present information on VDL Mode 4 radio tests in the band 112-118 MHz
1.d.Present information on VDL Mode 4 and IPS.
2.Complete new ATN/OSI Manual, DOC 9880
WP/2, 3, 4, 20, and 21, IP 5, Flimsy 1.
2.aTransfer remaining material of global implementation relevance from DOC 9705 (to be discontinued)
2.b.Introduce A/G security standards into ICAO DOC 9880
3.Maintenance activities for VDL Mode 2 (ICAO DOC 9776)
WP/11, 12, 13, 14, 15, 16, 17, 18, and 19.
3.a.This material is a result of on-going activities within AEEC 631 DLK for VDL Mode 2 implementation characteristics
4.Any other business
IP/4
5.Next meeting
6.Adjourn
Annex 2
Thirteenth Meeting of
ICAO ACP Working Group M (Maintenance)
18-21 November 2008
ICAO Headquarters
Montreal Canada
Attendance
Robert Frazier
USA/FAA
Vaughn Maiolla
ICAO
Peter Muraca
USA/FAA
Rob Morgenstern
USA/MITRE
Brent Phillips
USA/FAA
Robert Witzen
Sweden/LFV
Vidyut Patel
USA/FAA
Jean-Marc Vacher**
France/DSNA
Tony Kerr
EUROCONTROL
Danny Van Roosbroek
EUROCONTROL
Robin Hughes
Sweden/LFV
Tom McParland
USA/BCI
** indicates part time
Annex 3
List of Input Documents
Working Papers
Ref
Source
Title
Agenda Item
Size
WP1
Rapporteur
ACP WG-M/13 draft Agenda (rev1)
33kB
WP2
Danny Van Roosbroek
COMPLETION OF DOC 9880 Part IVA – ATN Directory
2 (a)
194kB
WP3
Danny Van Roosbroek
COMPLETION OF DOC 9880 Part IVB – ATN Security for AMHS
2 (b)
177kB
WP4
Danny Van Roosbroek
COMPLETION OF DOC 9880 Part III – ATN/OSI Internet Communication Service (ICS)
2 (a)
299kB
WP5
Danny Van Roosbroek
ATN Datalink Implementation in Europe
1 (b)
335kB
WP6
Larry Johnsson
AMENDMENTS TO VDL MODE 4 SARPS CONSEQUENTIAL TO THE ALLOCATION OF THE BAND 108-117.975 MHZ TO THE AERONAUTICAL MOBILE (R) SERVICE BY THE ITU WORLD RADIOCOMMUNICATION CONFERENCE 2007
1 (c)
110kB
WP7
Larry Johnsson
AMENDMENTS TO THE ICAO RF HANDBOOK ON RADIO FREQUENCY SPECTRUM REQUIREMENTS TO INCORPORATE ICAO STUDIES ON COMPATIBILITY BETWEEN VDL MODE 4 AND FM BROADCASTING
1 (c)
1.02MB
WP8
Larry Johnsson
INTRODUCTION OF IPS IN VDL MODE 4
1 (d)
72kB
WP9
Larry Johnsson
FREQUENCY ASSIGNMENT PLANNING CRITERIA FOR VDL MODES 2, 3 AND 4
1 (c)
441kB
WP10
Larry Johnsson
Use of the band 112 – 117.975 MHz by VDL Mode 4 Results of tests and frequency assignment planning criteria
1 (c)
1.54MB
WP11
Robert Morgenstern
Unrecognized XIDs
3
34kB
WP12
Robert Morgenstern
Allowed/Disallowed X25 options
3
103kB
WP13
Robert Morgenstern
Options
3
283kB
WP14
Robert Morgenstern
Multi-Frequency Operation
3
138kB
WP15
Robert Morgenstern
Network Identifier
3
42kB
WP16
Robert Morgenstern
MASPS Harmonisation
3
36kB
WP17
Robert Morgenstern
Called Line Address Modification Notification
3
35kB
WP18
Robert Morgenstern
Broadcast aircraft address
3
34kB
WP19
Robert Morgenstern
PROPOSED AMENDMENTS TO DOC 9776
3
192kB
WP20
Vidyut Patel
Approach for Air-Ground Security in Doc 9880
2 (b)
WP21
Vidyut Patel
Approach for Air-Ground Security in Doc 9880
2 (b)
Information Papers
Ref
Source
Title
Agenda Item
Size
IP1
Danny Van Roosbroek
LINK 2000+ UpLink 11 Newsletter
1 (b)
810kB
IP2
Robert Frazier
Data Communication Programme Status
1 (a)
428kB
IP3
Danny Van Roosbroek
Requirements for Single European Sky Data Link Services
1 (d)
IP4
Robin Hughes
Russian Integrated Wake Vortex Flight Safety System
3
IP5
Jean-Marc Vacher
Status of the MESANGE AMHS Implementation Project
2(a)
Flimsy
Ref
Source
Title
Agenda Item
Size
F 1
Jean Marc Vacher
Directory schema - atn-facilityName attribute is too short
2 (a)
Annex 4
from WP 6
Proposed amendments to Annex 10, Volume III, Part I, chapter 6
6.9 VDL MODE 4
......
6.9.2 VDL Mode 4 radio channels
6.9.2.1 VDL Mode 4 station frequency range
6.9.2.1.1 Transmitter/receiver tuning range. A VDL Mode 4 transmitter/receiver shall be capable of tuning to any of the 25 kHz channels from 117.975 MHz through 137 MHz. The transmitter shall have a means for the tuning range to be restricted to a narrower range.
Note.— Operational conditions or certain applications may require the equipment to be operated in a narrower frequency range.
6.9.2.1.2 Recommendation.— A VDL Mode 4 transmitter/receiver should be capable of tuning to any of the 25 kHz channels from 112 to 117.975 MHz.
Note.— The band 112–117.975 MHz may be utilized in accordance with the relevant provisions of the ITU Radio Regulations.
......
6.9.5.6 FM broadcast interference immunity
performance for VDL Mode 4 receiving systems
6.9.5.6.1 A VDL Mode 4 station shall conform to the requirements defined in section 6.3.5.4 when operating in the band 117.975–137 MHz.
6.9.5.6.2 A VDL Mode 4 station shall conform to the requirements defined below when operating in the band 112‑117.975 MHz.
6.9.5.6.2.1 The VDL Mode 4 receiving system shall meet the requirements specified in 6.3.5.1 in the presence of two-signal, third-order intermodulation products caused by VHF FM broadcast signals having levels in accordance with the following:
12
232420log0
0.4
D
ìü
++-£
íý
îþ
f
NN
for VHF FM sound broadcasting signals below 108 MHz,
where the frequencies of the two VHF FM sound broadcasting signals produce, within the receiver, a two-signal, third-order intermodulation product on the desired VDL Mode 4 frequency.
N1 and N2 are the levels (dBm) of the two VHF FM sound broadcasting signals at the VDL Mode 4 receiver input. Neither level shall exceed the desensitization criteria set forth in 6.9.5.6.2.2.
(f = 112 – f1, where f1 is the frequency of N1, the VHF FM sound broadcasting signal closer to 112 MHz.
6.9.5.6.2.2 The VDL Mode 4 receiving system shall not be desensitized in the presence of VHF FM broadcast signals having levels in accordance with Table 6-6.
......
TABLES FOR CHAPTER 6
......
Table 6-6. VDL Mode 4 operating on frequencies
between 112.0–117.975 MHz
Frequency
(MHz)
Maximum level of unwanted
signal at receiver input (dBm)
88–104
+15
106
+10
107
+5
107.9
0
Note.— The relationship is linear between adjacent points designated by the above frequencies.
......
Annex 5
from WP 7
Relevant Updates for the ICAO Handbook on the Band 108–117.975 MHz MHz
SECTION 7-II. CIVIL AVIATION FREQUENCY
ALLOCATIONS — ICAO POLICIES AND
RELATED INFORMATION
Band: 108–117.975 MHz
Service: Aeronautical radionavigation and Aeronautical Mobile (R) (VOR, ILS localizer, GBAS and
VDL Mode 4)
Allocation:
MHz
108–117.975
Allocation to Services
Region 1
Region 2
Region 3
108–117.975
AERONAUTICAL RADIONAVIGATION
MOD 5.197 MOD 5.197A
Footnotes:
MOD5.197 Additional allocation: in Pakistan and the Syrian Arab Republic, the band 108–111.975 MHz is also allocated to the mobile service on a secondary basis, subject to agreement obtained under No. 9.21. In order to ensure that harmful interference is not caused to stations of the aeronautical radionavigation service, stations of the mobile service shall not be introduced in the band until it is no longer required for the aeronautical radionavigation service by any administration which may be identified in the application of the procedures invoked under No. 9.21.
5.197A Additional allocation: the band 108-117.975 MHz is also allocated on a primary basis to the aeronautical mobile (R) service, limited to systems operating in accordance with recognized international aeronautical standards. Such use shall be in accordance with Resolution 413 (Rev.WRC‑07). The use of the band 108-112 MHz by the aeronautical mobile (R) service shall be limited to systems composed of ground-based transmitters and associated receivers that provide navigational information in support of air navigation functions in accordance with recognized international aeronautical standards. (WRC-07)
ICAO POLICY
•No change to the current allocation to the aeronautical radionavigation service and the aeronautical mobile (Route) service.
•Deletion of Footnote 5.197.
•Ensure conformity with ITU-R Recommendation SM.1009 regarding compatibility with FM broadcast services in the band 87.5–108 MHz and ILS/VOR and with ITU-R M.1841 for GBAS.
Ensure compatibility with digital broadcasting services in the band 87.5-108 MHz.
AVIATION USE: ILS localizer, VOR, GBAS and VDL Mode 4.
The ground-based augmentation system (GBAS), operating in the AM(R)S under the provisions of RR 5.197A, monitors GNSS signals at an aerodrome and broadcasts locally relevant integrity messages, pseudorange corrections and approach data via a VHF data broadcast (VDB) to aircraft within the range depending upon intended operations.
The sub-band 108–111.975 MHz is shared between ILS localizer and VOR in an interleaved 50 kHz and 100 kHz spaced frequency arrangement (108.1 and 108.15 MHz for ILS, 108, 108.05, 108.2 and 108.25 MHz for VOR, etc.).
The sub-band 112–117.975 MHz is used for VOR, with 50 kHz or 100 kHz channel spacing, depending on regional agreements and requirements.
GBAS is standardized to operate in the band 108–117.975 MHz. GBAS/ILS and GBAS/VHF COM frequency planning criteria are currently under development. Until these criteria are defined and included in SARPs, GBAS frequencies should be selected from the band 112.050–117.900 MHz.
VDL Mode 4 is standardized to operate in the band 112-117.975 MHz. It will provide data link services for air-ground and air-to-air communications and ADS-broadcast. It operates with 25 kHz channel spacing. VDL Mode 4 frequency assignment planning criteria that secure protection from interference between VDL Mode 4 and ILS/Localizer, VOR and GBAS are currently under development.
The ILS localizer is frequency paired with the glide path frequencies from the band 328.6–335.4 MHz and, where possible, with the microwave landing system (MLS) from the band 5 030–5 150 MHz. DME/N or DME/P from the band 960– 1 215 MHz are also frequency paired with ILS and/or MLS, respectively (see Figure 7‑8).
VOR is normally associated with DME and is frequency paired. Short-range airport VOR frequencies are usually taken from the sub-band 108–111.975 MHz.
ILS localizer, VOR, GBAS and VDL Mode 4 receivers are vulnerable to intermodulation and saturation effects from FM broadcast transmissions from the band 87–108 MHz. Material providing guidelines for States when assessing compatibility between assignments for FM broadcasting and aeronautical radionavigation (ILS/VOR) has been agreed in the ITU‑R (ITU-R.SM 1009 refers). WRC-03 adopted Resolution 413 (which was amended at WRC-07 to reflect the additional allocation to AM(R) S as per MOD 5.179A) and invited ITU-R to
further study compatibility issues between VDL Mode 4 and FM
broadcasting. In particular compatibility criteria as for new digital sound broadcasting systems, planned to operate in the band 87–108 MHz, need to be developed. ITU-R Recommendation M.1841 on the compatibility between GBAS and FM-sound broadcasting has been adopted in 2007 in ITU-R. ICAO has concluded that no ITU Recommendation on the compatibility between FM broadcasting and VDL Mode 4 needs to be developed (see below)
Frequency congestion for ILS and VOR exists in some high-density areas, such as Western Europe and North America. This applies to ILS and VOR and arises partially, from the frequency pairing and planning constraints exercised from MLS and DME.
The band has been used by aviation since 1947. On two occasions, the channel spacing for ILS and VOR was reduced from 200 kHz to 100 kHz in 1963 and from 100 kHz to 50 kHz in 1972 (at the 7th Air Navigation Conference). SARPs for VDL Mode 4 were introduced in 2001 and for GBAS in 2002.
Footnote 5.197 was introduced at WARC-87 in anticipation that ILS would be withdrawn from international service in 1998 and the use of the ILS localizer would be terminated. At WRC-03 most countries removed their names from this footnote since ILS will continue operation for the foreseeable future.
COMMENTARY (ILS): The comprehensive discussion under Agenda Items 1 to 3 of the Special COM/OPS/95 examined the future of ILS in the context of transition to MLS and to GNSS as envisaged in the FANS scenarios. This transition has been much slower than predicted. GNSS has not yet achieved Category II and Category III Capabilities. It is difficult to predict when such capabilities will be widely available.
……………
The introduction of the (generic) mobile service, in accordance with the provision of Footnote 5.197(WRC-07), is not possible in the foreseeable future. In light of the above, it is clear that the ILS allocation will be needed until well beyond 2025.
COMMENTARY (VOR): The continuing deployment of VOR is dependent on the progress, development and implementation of GNSS; the aviation community may continue to require VOR for some time after implementing GNSS. The GNSS Panel has developed SARPs for GNSS, and ICAO will continue through the NSP developing the measures and principles necessary to evolve towards the use of GNSS as a means of en-route navigation.
Different world regions will have different emphasis on their need for GNSS in the near and medium terms, and decisions will be taken at a regional level.
No definite or tentative dates have been agreed to for the GNSS programmes. In addition, safety requires a backup means of en-route navigation if all GNSS service is temporarily lost. It is therefore necessary to maintain the allocation for VOR until, at least, the year 2030.
COMMENTARY (GBAS): ICAO has identified the band 108–117.975 MHz to support ground-based augmentation systems (GBAS) operation. WRC-03 reviewed this band and introduced an allocation to the aeronautical mobile (route) service (AM(R)S) limited to systems that transmit navigational information in support of air navigation and surveillance functions. At WRC-07, this allocation was reduced to the band 112 – 117.975 MHz. These systems (currently ICAO has SARPs for VDL Mode 4 operating in this band) shall not cause harmful interference to nor claim protection from international standardized systems operating in the aeronautical radionavigation service (RR 5.197A (WRC-07) refers), including GBAS.
COMMENTARY (VDL Mode 4): SARPs have also been developed for VDL Mode 4 which supports surveillance (e.g. ADS) applications as well as air-ground data and air-to-air data communications. This system can only operate in the band 112–117.975 MHz and 117.975 – 137 MHz. Provisions have been made for such use in Annex 10 and the Radio Regulations (RR 5.197A (WRC-07) and Resolution 413 (Rev. WRC-07) refer).
Allocations to other services
Footnote 5.197 was added by the ITU WARC-87 for mobile services. The footnote introduced the mobile service in the band 108–111.975 MHz in a number of countries. Based on present expectations for the use of the band, it is improbable that this footnote can be considered for implementation for many years (possibly post-2015) in most of the countries in the note. The footnote is not meaningful in practical terms and carries the risk that more country names will be added at future conferences. Hence it should be deleted in its entirety. Furthermore, it should be noted that no guidance exists on how Footnote 5.197 would be applied, or what essential prior agreements are necessary within aviation for mobile service operations to commence on any single frequency or within particular sub-bands. This inexactness compounds the problem, as it leaves room for undesirable interpretations that could be used to allow entry of the mobile service in the band. Many countries, initially included in this footnote, have been deleted from this footnote
WRC-07
At WRC-07 an allocation to the aeronautical mobile (R) service, on a primary basis, was introduced in the band 1`08-117.975 MHz. For the use of this allocation, the conditions of Resolution 413 (Rev. WRC-07) apply.
Important elements of this Resolution include:
-AM(R)S shall not cause harmful interference to the aeronautical radionavigation service
- AM(R)S systems operating in this band shall meet the FM broadcasting immunity criteria as per ICAO Annex 10 SARPs.
-Only GBAS can operate in the band 108-112 MHz
- Any AM(R)S operating in this band system shall meet ICAO SARPs (which implies that, in order to operate, ICAO SARPs need to be developed).
This Resolution further stipulates that “WRC-11 should consider , on the basis of results of ITU-R studies, mentioned under Invites ITU-R, any further regulatory measure to facilitate introduction of new AM(R)S systems.”. It is not clear what measures could be envisaged.
ITU-R is further invited through this Resolution to study any compatibility issue between the AM(R)S and FM broadcasting as well as the effect of the introduction of digital broadcasting systems in the band below 108 MHz. ICAO has concluded that no ITU material (e.g. in the format of an ITU-R Recommendation needs to be developed for VDL Mode 4. ITU_R Recommendations for ILS, VOR (SM.1009) and GBAS (M.1841) are already in place. New AM(R)S systems that may need to use this band would require an assessment, in ICAO as well as in ITU, of the potential interactions with FM Broadcasting systems. In this regard it is worth noting that these studies do not include the effect of digital broadcasting on ILS/VOR/GBAS/VDL Mode 4. Work on the compatibility between digital broadcasting in the band 87-108 MHz has started in ITU in 2008. Study Groups 5 and 6 are involved in this activity.
TECHNICAL AND OTHER INFORMATION
Band: 108–117.975 MHz
Service: Aeronautical radionavigation, Aeronautical Mobile (R)
Aviation use:
VOR (108–117.975 MHz)
ILS localizer (108–111.975 MHz)
GBAS (112.050–117.900 MHz) [108-117.975 MHz]
VDL Mode 4 (112 – 117.975 MHz)
Annex 10:
SARPs: Annex 10, Volume I, Chapter 3, 3.1 (ILS), 3.3 (VOR), 3.7 (GBAS) and Volume III, Chapter 6 (VDL Mode 4)
Annex 10, Volume III, Part I, Chapter 6, 6.9 (VDL Mode 4)
Frequency plan: Annex 10, Volume I, Chapter 3, 3.1.6 (ILS), 3.7.3.5.4.1. (GBAS)
Channelization: 100 kHz/50 kHz spacing for ILS, VOR and 25 kHz for GBAS
Planning criteria:
Annex 10, Volume V, Chapter 4, 4.2
Annex 10, Volume I, Attachment C, 2.6 (ILS)
Annex 10, Volume I, Attachment C, 3.5 (VOR/ILS)
Annex 10, Volume I, Appendix B, 3.6.8.2.2. and Attachment D, 7.2.1 (GBAS)
VDL Mode 4 25 kHz channel spacing (Annex 10, Volume III, Part I, Chapter 6, 6.9.2.1.1 AND 6.9.2.1.2
RTCA:
ILS: DO-195, MOPS for Airborne ILS Localizer Receiving Equipment Operating within the Radio Frequency Range of 108–112 MHz (1986)
…………………..
VDL Mode 4: ED-108, MOPS for VHF VDL Mode 4 Aircraft Transceiver for ADS-B (2001)
ARINC characteristics:
ILS: 578-4, Airborne ILS Receiver
ILS: 710-10, Mark 2 Airborne ILS Receiver
VOR: 579-2, Airborne VOR Receiver
VOR/ILS: 711-10, Airborne VOR ILS Receiver
ITU Res./Rec.: Res. 413; Use of the band 108-117.975 MHz by the aeronautical mobile (R) service
ITU‑R:
•ITU‑R M44‑1: Signal-to-interference ratios and minimum field strengths required in the aeronautical mobile (route) service above 30 MHz
•ITU‑R.SM 1009: Compatibility between the sound broadcasting service inthe band 87–108 MHz and the aeronautical services in the band 108–137 MHz
ITU-R.M 1841: Compatibility between FM sound-broadcasting in the band of about87-108 MHz and the aeronautical ground-based augmentation system in the band about 108-117.975 MHz
INTERFERENCE FROM
NON-AERONAUTICAL SOURCES
COMPATIBILITY BETWEEN ILS/VOR AND
FM BROADCASTING
……………………….
Type B2:performance degradation due to high-power overload and desensitization without any frequency relationship.
This Recommendation, with its three detailed Annexes, provides the essential requirements for the identification and analysis of interference situations and for the coordination between broadcasting and aeronautical interests within a country or between countries. The criteria and methods have been developed and reviewed by a group of experts and represent the best available information on the subject. Furthermore, the Recommendation is recognized by aeronautical and telecommunication authorities as the definitive guidance for planning and coordination purposes.
In 2007 ITU-R Recommendation M.1841 on “Compatibility between FM sound-broadcasting in the band of about 87-108 MHz and the aeronautical ground-based augmentation system in the band about 108-117.975 MHz” was approved. This Recommendation provides the necessary material for assessing compatibility between FM broadcasting and GBAS systems operating in the band 108 – 117.975 MHz. The principles for protection of GBAS from harmful interference from FM broadcasting signals are similar to those for ILS/VOR. This Recommendation is in line with the FM-immunity criteria developed for GBAS by ICAO.
In 2008 ICAO reviewed potential interference from FM broadcasting stations into VDL Mode 4, operating in the band 112-117.975 MHz. Although at relative short distances from high-powered FM broadcasting stations (less than 1 km) harmful interference could be caused in some cases to VDL Mode 4, it was concluded that no international coordination criteria between FM broadcasting assignments and VDL mode 4 assignments would be necessary. A technical analysis of compatibility between FM broadcasting and VDL Mode 4 is in Part II of this Handbook
ICAO Studies
Handbook for evaluation of electromagnetic compatibility (EMC) between ILS and FM broadcasting stations using flight tests (1997)
………………….
The FM-immunity SARPs are contained in:
(i)for ILS:Annex 10, Volume I, 3.1.4, Interference immunity performance for ILS localizer receiving systems and Annex 10, Volume I, Attachment C, 2.2.9, providing guidance material;
(ii)for VOR:Annex 10, Volume I, 3.3.8, Interference immunity performance for VOR receiving systems;
(iii)for GBAS:Annex 10, Volume I, Appendix B, 3.6.8.2.2;
(iv)for VDL:Annex 10, Volume III, Part I, 6.3.5.4 (VDL); and
(v)for VHF Com:Annex 10, Volume III, Part II, 2.3.3, Interference immunity performance and Annex 10, Volume III, Part II, Attachment A, 1.3.
(vi)for VDL Mode 4: Annex 10, Volume III, Part I, 6.9.5.6
==========================================================
Material for incorporation in Part II of the Handbook (Details on Frequency assignment planning and coordination)
NEW TEXT
1
Compatibility between FM Broadcasting stations and VDL Mode 4.
1.2
In ITU-R criteria have been established on the compatibility between FM broadcasting stations operating in the band 87-108 MHz and aeronautical radionavigation systems (ILS, VOR and GBAS) operating in the band 108-117.975 MHz. These criteria are contained in ITU-R Recommendations SM.1009 (ILS and VOR) and M.1841 (GBAS). For assessing interference between VDL Mode 4 and FM Broadcasting no specific ITU-R material (such as an ITU-R Recommendation) has been developed as the interference that can occur is a local matter that can be solved nationally.
1.3
The analysis below examines the interference mechanisms for type A1, A2, B1 and B2 interference for VDL Mode 4. Reference material is taken from ITU-R Recommendation M.1841and ICAO Annex 10. It provides guidance to ICAO Contracting States when assessing compatibility between FM broadcasting transmissions and VDL Mode 4.
2.
Type A1 interference.
2.1
Type A1 interference is (mainly) caused by spurious emissions or inter-modulation products generated by several FM broadcasting transmitters (normally operating from the same FM broadcasting transmitter site. These emissions fall within the pass-band of the aeronautical receivers and cannot be suppressed by these receivers. Suppression is only possible at the FM broadcasting site and is normally achieved through filtering of the spurious emissions.
2.2
For FM broadcasting transmitters typical suppression of spurious emissions from co-sited broadcasting transmitters in the aeronautical band 108-117.975 MHz, including intermodulation products, is as in Table 1.
Maximum e.r.p. (dBW) for FM broadcasting transmitters
Suppression relative to maximum e.r.p (dB)
≥48
85
30
76
≤30
46 + max. e.r.p (dBw)
Table 1
Note 1: linear interpolation is used between maximum e.r.p. values of 30 and 48 dBW.
Note 2: Implementation of FM broadcasting stations needs to secure that at least these values are met.
2.3
The protection ratio (D/U) that may be used to assess type A1 interference for VDL Mode 4 receivers is as in Table 2:
Frequency difference between wanted signal and spurious emission (kHz)
Protection ratio (dB)
0
14
50
7
100
-4
150
-19
200
-38
Table 2
Note: These protection ratios are the same as those for ILS, VOR and GBAS. Manufacturers need to ensure to comply with these.
2.4
Calculation of interference margin for type A1 interference
2.4.1
Paragraph 3.2.5 of Recommendation M.1841 shows that the type A1 interference margin should be calculated as:
(Re. (13) in Rec. M.1481)
where:
IM: A1 interference margin (a positive margin implies no interference)
N:number of inter-modulation components (N=2 or 3)
Ei :field strength (dB(µV/m)) of the (unwanted) FM broadcasting transmission i
Si :Type A1 suppression (dB) of broadcasting transmitter I (See Table 1)
PR:protection ratio as per Table 2 (in the analysis only the co-channel case whereby the inter-modulation product coincides with the desired aeronautical frequency was used; this was considered to present the worst case)
Ew:field strength (dB(µV/m)) of the aeronautical signal (at least 37.5 dB(µV/m) for VDL Mode 4)
2.4.2E can be calculated as follows:
E=76.9+P-20logd(Re. (1) in Rec. M.1481)
where:
E :field strength (dB(µV/m)) of the (unwanted) FM broadcasting transmission
P:maximum e.r.p (dBW) of the broadcasting station
d:distance between the broadcasting station and the aeronautical receiver
Note: Both the FM Broadcasting signal as the VDL Mode 4 signal are vertically polarized.
2.4.3Reference (13) in paragraph 2.4.1 above can be re-written as follows:
=0
2.4.3.1
In the following example:
· the radiated power of the FM broadcasting transmitter P=100 kW;
· type A1 suppression S =85 dB as per Table 1;
· the spurious emission or inter-modulation product coincides with the aeronautical frequency in use (PR=14 dB) and
· Ew is 37.5 dB(µV/m) (minimum fieldstrength for VDL Mode 4),
the interference margin of 0 dB will be reached at a minimum interference of separation distance of 8.3 km. This can be considered too large for most operational situations where VDL Mode 4 is being used.
2.4.3.2
Should the type A1 suppression be increased to 103.4 dB, the interference distance would be reduced to less than 1 km.
2.3.4.3
Mitigating factors that can be considered include the consideration of the vertical antenna diagram of the broadcasting transmitter and the efficiency of the FM broadcasting antenna to radiate signals above 112 MHz. It should also be considered that this type of interference normally occurs in cases where two broadcasting antennas are co-located (or in their near vicinity) and the radiated signal of one transmitter can be coupled into the other the antenna of the other transmitter (or when one FM-broadcasting antenna is used for two transmitters)
2.5
As a result, it was concluded that Type A1 interference is a local issue that can be solved by technical means as required, including frequency assignment planning, as an implementation measure. The attention of the possibility of Type A1 interference needs to be considered by aviation and the broadcasting community.
3.
Type A2 interference.
3.1
Type A2 interference is caused by non-negligible components of the FM signal nearby (about +/- .5 MHz) the FM broadcasting operating frequency. This type of interference from FM broadcasting transmitters will in practice only occur in the aeronautical band near the band-edge (108 MHz).
3.2
For VDL mode 4, operating above 112 MHz, type A2 interference is not expected.
4.
Type B1 interference.
4.1
Type B1 interference is interference caused by third order inter-modulation products that are generated inside an aeronautical receiver resulting from (high powered) broadcasting transmissions outside the aeronautical frequency band. (See also Rec. M.1841, paragraph 2.2.2). These inter-modulation products can involve two or three broadcasting frequencies.
4.2
For the assessment of type B1 interference (two frequencies, fintermod= 2f1-f2)
The following formula can be used:
(4)
Note: This formula is derived from formula (13) in ITU-R Recommendation M.1841
4.3
From formulas (1) and (2) in Recommendation M.1841) the value for N (which is the (dBm) of the FM-broadcasting signal at the input of the aeronautical receiver) can be calculated as follows:
(5)
In these formulas:
N (N1 or N2): broadcasting signal level (dBm) at the input of the aeronautical receiver
P:
maximum e.r.p. (dBW) of the broadcasting station
d:
distance from the broadcasting station to the aeronautical receiver
Ls:
signal splitter loss of 3.5 dB
Lf:
antenna system frequency dependent loss at broadcasting frequency f (MHz) of 1.2 dB per MHz below 112 MHz
La:
antenna system fixed loss of 9 dB
K:
78
Lc:
correction factor (dB) to account for changes in wanted signal level.
S:
3 dB
Formula (5) can be re-written when Ls =3.5 dB and La=9 dB as
When P =100 kW (or 50 (dBW))
4.3.1
The correction factor Lc in this example is assumed to be 0 (no correction as the wanted VDL Mode 4 signal is assumed to be at the minimum value).
4.3.2
Calculation of minimum separation distance between VDL Mode 4 receivers and an FM broadcasting station with the following characteristics:
f1 = 107.9 MHz
f2 = 103.8 MHz
P1=P2=100 kW (50 dBW)
In this example, the FM-Broadcasting antennas are co-located; the combination of f1 and f2 is the worst case capable of generating an inter-modulation product on the aeronautical frequency 112 MHz (ie. the FM broadcasting frequencies are the closest possible to generate an intermodulation product on the lowest assignable VDL Mode 4 frequency (112 MHz).
4.3.3
The minimum separation distance between VDL Mode 4 receivers and FM broadcasting transmitters in the above case would be about 550m. For two FM broadcasting stations, operating on the same frequencies and an e.r.p of 300 kW, this distance would increase to about 960 m.
4.4.
As this has been considered as the worst case, type B1 interference has been considered to not cause a threat that would cause harmful interference to the reception of VDL Mode 4 signals as normally the separation between an aircraft and a high-power FM broadcasting station would be more than 1 km.
5.
Type B2 interference.
5.1
Type B2 interference is characterized as desensitization of the RF section of an aeronautical receiver when it is subject to overloading by one or more high powered broadcasting transmissions. Annex 10, Volume III, Part I, paragraph 6.9.5.6.2.2 provides B2 immunity criteria for the VDL Mode 4 receiver.
5.2
In accordance with formula (10) of Recommendation M.1841, the maximum level of an FM broadcasting signal at the input of a VDL Mode 4 receiver can be established as follows:
(re. (10) in Rec. M.1481)
For f=107.9 MHz, =15-3=12 dB (correction factor Lc is not applied)
Compatibility is achieved at a distance of about 165m from the FM broadcasting transmitter.
5.3
It has been concluded that type B2 interference will not cause harmful interference from FM broadcasting stations into VDL Mode 4 receivers.
6.
Assessment of potential interference
6.1
VDL Mode 4 frequencies are used on a national, Regional or Global basis, throughout a large designated operational coverage area. It has been concluded that only type A1 interference can be identified as an interference mechanism that can potentially cause harmful interference to VDL Mode 4. Type A1interference has its maximum value at the transmitter site. For assessing potential type A1 interference into VDL Mode 4 it is therefore sufficient consider each site from which more than one FM broadcast transmitter is operating as a test point and perform the analysis as described in paragraph 2 above.
END OF NEW TEXT
Annex 6
from WP 9
Material for Incorporation in the ICAO Handbook Volume II, on Radio Frequency Spectrum Requirements for Civil Aviation (Doc. 9718)
Frequency assignment planning criteria and guidance material for the VHF Digital Link (VDL)
1. INTERFERENCE THRESHOLDS
tc \l1 "INTERFERENCE THRESHOLDS
1. The interference threshold for the VHF digital link (VDL) is specified (Annex 10, Volume III, Part I, paragraph 6.3.5.1) as follows:
a) VDL Mode 2 maximum corrected bit error rate (BER) is 1 in 104;
Note. The uncorrected BER value of 1 in 103 is to be used in the testing of equipment. The forward error correction method used in VDL Mode 2 (Annex 10, Volume III, Part I, paragraph 6.4.3.1.2.1 refers) translates an uncorrected BER of 1 in 103 into a corrected BER of 1 in 104 (See also MOPS for VDL Mode 2).
b) VDL Mode 4 maximum uncorrected bit error rate is 1 in 104.
Note.- The BER value for VDL Mode 4 corresponds to a message error rate (MER) of approximately 2 in 102 using the formula MER=1‑(1‑BER)216 and assuming a one slot message with 216 bits of data. VDL Mode 4 does not provide forward error correction of the data.
2. SIGNAL PARAMETERS
tc \l1 "SIGNAL PARAMETERS
2. The values for the radio frequency signal in Table 1 have been used are to be used in the testing of equipment and the development of separation criteria for VDL.
2.2.The VDL interference immunity criteria (D/U ratio) which are identified in these VDL frequency assignment planning criteria and developed in accordance agreed test methods in Section 4 are defined as follows:
”the protection parameter (as specified in section 3, e.g. an S/P ratio of 6 dB) shall be met with the specified minimum desired signal level (dBm) at the receiver input (as specified in Table 1) and an undesired signal with a signal level (dBm) at the receiver input causing interference not exceeding the protection parameter; the D/U* ratio is the ratio between the two signal levels as measured on their transmitted frequency (either co‑ or adjacent to the desired frequency).”
Note: full details on the testing methods are contained in the Report of ACP WG M/12 and are available at http://www.icao.int/anb/panels/acp/wgdoclist.cfm?MeetingID=242
Table 1.
Parameter
DSB‑AM
DSB‑AM
VDL‑M2
VDL‑M2
VDL‑M3
VDL‑M3
VDL‑M4
VDL‑M4
TRANSMITTER
Airborne
Ground
Airborne
Ground
Airborne
Ground
Airborne
Ground
Output power transmitter
44 dBm
(25 W)
50 dBm
(100 W)
42 dBm
(16 W)
44 dBm
(25 W)
44 dBm
(25 W)
44 dBm
(25 W)
42 dBm
(15 W)
45 dBm
(32 W)
Feeder loss (assumed)
‑3 dB
‑3 dB
‑3 dB
‑3 dB
‑3 dB
‑3 dB
‑3 dB
‑3 dB
Antenna gain (assumed)
0 dB
2 dB
0 dB
2 dB
0 dB
2 dB
0 dB
2 dB
EIRP
41 dBm
(12.5 W)
49 dBm
(80 W)
39 dBm
(8W)
43 dBm
(20 W)
41 dBm
(12.5 W)
43 dBm
(20 W)
39 dBm
(10 W)
44 dBm
(25 W)
Adjacent channel emission (Transmitter) for VDL specified in Annex 10, Vol. III, Part I, paragraph 6.3.4
1st adj ch. (16 kHz bandwidth)
Not specified in Annex 10
‑18 dBm
‑18 dBm
‑18 dBm
‑18 dBm
‑18 dBm
‑18 dBm
2nd adj ch. (25 kHz bandwidth)
Not specified in Annex 10
‑28 dBm
‑28 dBm
‑28 dBm
‑28 dBm
‑28 dBm
‑28 dBm
4th adj ch. (25 kHz bandwidth)
Not specified in Annex 10
‑38 dBm
‑38 dBm
‑38 dBm
‑38 dBm
‑38 dBm
‑38 dBm
8th adj ch. (25 kHz bandwidth)
Not specified in Annex 10
‑43 dBm
‑43 dBm
‑43 dBm
‑43 dBm
‑43 dBm
‑43 dBm
16th adj ch. (25 kHz bandwidth)
Not specified in Annex 10
‑48 dBm
‑48 dBm
‑48 dBm
‑48 dBm
‑48 dBm
‑48 dBm
32nd adj ch. (25 kHz bandwidth)
Not specified in Annex 10
‑53.dBm
‑53.dBm
‑53.dBm
‑53.dBm
‑53.dBm
‑53.dBm
RECEIVER
Min signal at receiver antenna
Annex 10, Vol. III
75 μV/m
(‑82 dBm)
part II
2.2.1.2
20 μV/m
(‑93 dBm)
part II
2.3.1.2
75 μV/m
(‑82 dBm)
part I
6.2.2.
20 μV/m
(‑93 dBm)
part I
6.3.2
75 μV/m
(‑82 dBm)
part I
6.2.2.
20 μV/m
(‑93 dBm)
part I
6.3.2
75 μV/m
(‑82 dBm)
part I
6.9.5.1.1.2
35 μV/m
(‑88 dBm)
part I
6.9.5.1.1.1
Feeder loss
‑3 dB
‑3 dB
‑3 dB
‑3 dB
‑3 dB
‑3 dB
‑3 dB
‑3 dB
Antenna gain
0 dB
2 dB
0 dB
2 dB
0 dB
2 dB
0 dB
2 dB
Min. signal at receiver input
‑85 dBm
‑94 dBm
‑85 dBm
‑94 dBm
‑85 dBm
‑94 dBm
‑85 dBm
‑89 dBm
Out‑of‑band immunity performance of receiver as per Annex 10, Volume III, Part I, paragraph 6.3.5.3.(VDL) and Volume III, Part II, paragraph 2.3.2.8 (DSB‑AM).
1st adj. Ch
‑40 dB
‑40 dB
‑40 dB
‑40 dB
‑40 dB
‑40 dB
4th adj. Ch
‑50 dB
‑50 dB
‑60 dB
‑60 dB
‑60 dB
‑60 dB
‑60 dB
‑60 dB
Conversion from input power (dBm) to field strength (μV/m and v.v.) was done on the basis of the following formula: Pr = E ‑ 20logF ‑ 167.2; where Pr is isotropically received power (dB(W)), E is the electric field strength (dB(μV/m) and F is the frequency (GHz) (ITU‑R Recommendation PN.525‑2 refers).
This formula can be converted in
10logPr = 20logE – 20logF-77.2 where Pr is signal at receiver antenna (in space) in mW, E is the field strength at the antenna in µV/m and F is the frequency f in MHz.
3
VDL ADJACENT CHANNNEL IMMUNITY CRITERIA
tc \l1 "OUT‑OF‑BAND IMMUNITY PERFORMANCE
Note.- When in this section reference is made to adjacent channels, this reference is to the actual adjacent channel with 25 kHz separation.
3.1
Annex 10, Volume III, Part II, paragraph 3.2.8.2 contains the immunity criteria for DSB‑AM receiving systems against interference from any VDL station. It has been observed, on the basis of testing results of a number of aircraft DSB‑AM receivers in accordance with the test method described in section 4.6, that the immunity performance characteristics in Annex 10 would result in overly pessimistic frequency assignment criteria to protect DSB‑AM systems when interfered with a VDL Mode 2 signal. The DSB‑AM receivers tested, which were considered to be representative for the airborne receivers currently in use (with 25 kHz characteristics), showed significantly better immunity performance characteristics than those given in Annex 10. Adjacent channel immunity criteria were developed as outlined below
3.2VDL Mode 2
tc \l2 "VDL Mode 2
VDL Mode 2 and DSB‑AM systems
tc \l3 "VDL Mode 2 and DSB‑AM systems
3.2.1
The following immunity criteria have been developed on the basis of actual equipment testing:
b) interference caused by VDL Mode 2 into DSB‑AM systems;
c) interference caused by DSB‑AM systems into VDL Mode 2; and
d) interference from VDL Mode 2 into VDL Mode 2.
3.2.2.
Considering the worst case test results for each of these receivers, the following interference immunity criteria characteristics for DSB‑AM systems when interfered with a VDL Mode 2 signal (and vice versa) were developed:
Table 2. D/U ratios for desired DSB-AM and undesired VDL Mode 2
Adjacent channel
D/U ratio (dB)
1
‑34
2
‑53
3
‑60
4
‑63
5
‑65
10
<‑65
20
<‑65
40
<‑65
Table 3. D/U ratios for desired VDL Mode 2 and undesired DSB-AM signals
Adjacent channel
D/U* ratio (dB)
1
‑33
2
‑60
3
‑60
4
‑66
5
‑69
10
<‑69
20
<‑69
40
<‑69
3.2.3
It was concluded that the D/U* ratio for VDL Mode 2 being interfered with DSB‑AM systems is better that when DSB‑AM systems are being interfered with VDL Mode 2. Therefore, the calculation of minimum geographical separation distances concentrates on the protection of DSB‑AM systems.
VDL Mode 2 systems
Table 4. D/U ratios for desired VDL Mode 2 and undesired VDL Mode 2
Adjacent channel
D/U* ratio (dB)
1
‑29
2
‑66
3
‑68
4
‑67
5
‑67
3.3.
VDL Mode 4
Note: the immunity criteria in this paragraph apply only to VDL Mode 4 operating in the band 130-137 MHz.
3.3.1
The following immunity criteria have been developed on the basis of actual equipment testing:
a)interference caused by VDL Mode 4 into DSB‑AM systems;
b)interference caused by DSB‑AM systems into VDL Mode 2; and
c)interference from VDL Mode 4 into VDL Mode 2.
d)interference from VDL Mode 2 into VDL Mode 4.
e)interference from VDL Mode 4 into VDL Mode 4.
3.2.2.
Considering the worst case test results for each of these receivers, the following interference immunity criteria characteristics for DSB-AM, VDL Mode 2 and VDL Mode 4 systems when interfered with a VDL Mode 4 signal (and vice versa) were developed:
Table 5. D/U ratios for desired DSB-AM and undesired VDL Mode 4
Adjacent channel (25 kHz)
D/U* ratio (dB)
1
-45
2
-47
3
-52
4
-53
5
-57
10
< -64
20
< -64
40
< -64
Table 6. D/U ratios for desired VDL Mode 4 and undesired DSB-AM signals
Adjacent channel (25 kHz)
D/U ratio (dB)
1
-45
2
-51
3
-58
4
-55
5
-63
10
-67
20
-68
40
-69
3.2.3
It was concluded that the D/U* ratio for VDL Mode 4 being interfered with DSB‑AM systems is less constraining than when DSB‑AM systems are being interfered with VDL Mode 4. Therefore, the calculation of minimum geographical separation distances concentrates on the protection of DSB‑AM systems.
Table 5. D/U ratios for desired VDL Mode 2 and undesired VDL Mode 4
Adjacent channel (25 kHz)
D/U ratio (dB)
1
-41
2
-57
3
-61
4
-62
5
-65
10
-70
20
-72
40
-74
Table 6. D/U ratios for desired VDL Mode 4 and undesired DSB-AM signals
Adjacent channel (25 kHz)
D/U* ratio (dB)
1
-42
2
-58
3
-59
4
-62
5
-63
10
-64
20
-62
40
-63
3.2.4
It was concluded that the D/U* ratio for VDL Mode 4 being interfered with a VDL Mode 2 signal is similar to those for VDL Mode 2 being interfered with VDL Mode 4 signals.
Table 6. D/U ratios for desired VDL Mode 4 and undesired VDL Mode 4
Adjacent channel (25 kHz)
D/U* ratio (dB)
1
-33
2
-58
3
-51
4
-58
5
-56
10
-62
20
-63
40
-62
4
FREQUENCY ASSIGNMENT PLANNING CRITERIA
tc \l1 "FREQUENCY ASSIGNMENT PLANNING CRITERIA
4.1
Propagation model
tc \l2 "Propagation model
4.2.1.1
Separation distances were calculated on the basis of free space propagation.
4.2.1.2The transmission loss (Lbf) using free space propagation characteristics can be calculated as follows:
Lbf (dB) = 20log(f) + 20 log(d) +32.4 (Re. ITU R Recommendation 525‑2)(1)
where:f = MHz
d = km
4.2
Interference model
Undesired
Transmitter
Feeder
Loss
Antenna
Gain
Transmission
Loss
Antenna
Gain
Feeder
Loss
Desired
Receiver
Desired
Signal
Co-channel or
adjacent channel with
the desired signal
TuLuGuLbf
PdPd
Pu
tc \l2 "Interference model
Pd ‑ Pu = D/U = Pd ‑ {(Tu +Lu + Gu) ‑Lbf} where: Pd, Pu and Tu are expressed in dBm (2)
Lu, Gu and Lbf are expressed in dB
From (1) and (2) the separation distance can be calculated by:
20log(d) = D/U ‑ Pd + Tu + Lu + Gu ‑ 20log(f) ‑ 32.4(3)
The EIRPu of the undesired transmitter equals Tu + Lu + Gu which converts formula (3) into
20log(d) = D/U ‑ Pd + EIRPu ‑ 20log(f) ‑ 32.4(4)
The factor 20log(f) introduces a variation of 1.24 dB in the results of calculating 20 log(d). (20log(f) is for the frequency 136 MHz 42.67 and for 118 MHz 41.43; therefore minimum separation distances are at the lower band edge slightly larger than at 136 MHz.
5
SEPARATION DISTANCES FOR VDL MODE 2 (VDL Mode 2 vs DSB-AM and VDL Mode 2 vs VDL Mode2)
5.1
Co-channel separation distance
5.2No measurements addressing the co‑channel interference from DSB‑AM into VDL Mode 2 and from VDL Mode 2 into DSB‑AM have been developed, as the same channel should not be used for VDL Mode 2 and DSB-AM. To avoid the need for interregional coordination, globally harmonized frequencies should be used for VDL Mode 2. Where possible, the band 136‑137 MHz should be reserved for VDL operations. Coordination with ICAO regional office has been conducted to ensure that the band is reserved. Coordination of specific assignments still needs to be conducted in particular regions.
5.2.1
In order to avoid co-channel interference should be based upon a D/U ratio of 20 dB (radio line of sight protection) for all interference scenarios.
5.3
Adjacent channel separation distance
Note:
The current frequency assignment planning criteria apply to VDL Mode 4 systems operating on frequencies higher than 130 MHz. No assignments to VDL Mode 4 below 130 MHz are recommended until full compatibility with DSB-AM systems operating in the frequency range 117.975 – 130 MHz is demonstrated.
5.3.1
Protection of aircraft in flight from interference from aircraft in flight.
5.3.1.1
tc \l3 "Interference to aircraft in flight(air‑to‑air interference)The minimum separation of aircraft in this scenario is 600 m (2 000 ft). This corresponds to the operational scenario where two aircraft are flying a parallel track in the same direction on flight levels separated by 600 m (2 000 ft). In this interference scenario transmissions from one aircraft may cause interference to the reception of signals on another (nearby) aircraft. In some cases flight levels are separated by less than 600 m but this is only applied for aircraft flying in opposite directions. Any interference that can be caused is transient.
5.3.1.2
Protection between DSB-AM systems and VDL Mode 2 is obtained at the 2nd adjacent (25 kHz) channel and higher.
5.3.1.3Protection between DSB-AM systems and VDL Mode 4 is obtained at the 3rd adjacent (25 kHz channel) and higher.
5.3.1.4Protection between VDL Mode 2 systems is obtained at the 2nd adjacent (25 kHz) channel and higher
5.3.1.5Protection between VDL Mode 2 and VDL Mode 4 systems is obtained at the 2nd adjacent (25 kHz) channel and higher
5.3.1.6Protection between VDL Mode 4 systems is obtained at the 2nd adjacent (25 kHz) channel and higher.
5.3.2Aircraft in flight and ground receiving station
tc \l3 "Aircraft in flight and ground stations
5.3.2.1
When VDL Mode 2 stations are situated in the vicinity of an airport, consideration needs to be given to the need to secure that this distance is met between a ground station and an aircraft station in all operational circumstances. The frequency separation and the separation distances indicated in this section are only illustrative and do not present generic frequency assignment planning criteria for VDL. Local conditions need to be taken into consideration when actually implementing VDL at or in the vicinity of airports. More information is available in the Report of ACP WG M/12 and can be accessed http://www.icao.int/anb/panels/acp/wgdoclist.cfm?MeetingID=242
5.4.3.2
Protection of a desired VDL Mode 2 ground receiving station from interference from an undesired airborne DSB-AM station at a distance of 600 m is obtained at the fourth adjacent 25 kHz channel (this is the most stringent interference mechanism).
Protection of a desired DSB-AM ground receiving station from interference from an undesired airborne VDL Mode 4 station at a distance of 600 m is obtained at the tenth adjacent 25 kHz channel.
Should this separation distance not be met, special measures need to be taken to secure protection. These measures could include to maintain larger frequency separation between the two stations or to introduce special cavity filters to further attenuate the undesired signal at the ground receiving station if these separation distances cannot be met. Additional mitigations due to the transient nature of this scenario could also be taken into account. Protection of aircraft receivers from interference from ground based transmitters requires smaller protection distances than those necessary to prevent interference from aircraft stations into ground receiver stations because of the higher wanted signal level at the aircraft.
5.3.3
Interference between aircraft on the ground
5.3.3.1
The minimum distance between aircraft on the ground at an airport can be expected to be between 50 and 100 m. However, the interference immunity performance of DSB‑AM and VDL systems, as specified in the SARPs (respectively 50 dB and 60 dB rejection at the 4th channel and beyond), is not sufficient to protect a desired signal at minimum power of ‑82 dBm at the aircraft antenna from an interfering signal at short distance. For example 72 dB (50 m) to 66 dB (100 m) would be required, using the model in Section 4 above.
5.3.3.2
In practice, protection at 50 m distance can be achieved with a desired minimum signal level of ‑70dBm at the aircraft receiver input in all cases. It was concluded from measurements on a number of representative airports that this level is achievable in most operational conditions on the ground. These factors should be considered in case VDL is being implemented at an airport. This interference mechanism does not, in general, constitutes a frequency assignment planning constraint.
5.3.4
Interference between aircraft on the ground and ground‑station
tc \l3 "Interference between aircraft onthe ground and ground‑station
5.4.5.1
VDL Mode 2 and Mode 4 can cause interference to DSB-AM up to a distance of about 1 km and when operating on the fifth adjacent (25 kHz) channel.
5.4.5.2
Special installation and filtering techniques may be applied to ground‑stations operating at a fixed frequency with a high sensitivity. In particular, large improvement in interference rejection may be obtained through the addition in the ground receiver station of a cavity filter or a quartz filter.
5.4.5.3Mitigation techniques that would eliminate interference can be implemented in the ground station. This interference mechanism does not constitute a frequency assignment planning constraint.
5.4.6
Interference between ground transmission stations and ground receiver stations
tc \l3 "Interference between ground transmissionstations and ground receiver stations
5.4.6.1
Normally, ground transmitters are geographically separated from ground receiver stations. Transmissions from ground DSB‑AM stations may interfere with the (ground) reception of VDL Mode 2 signals and transmission from ground VDL Mode 2 signals may interfere with the (ground) reception of DSB‑AM signals. This should be considered in the design of ground station characteristics. Also here, the use of special cavity filters may assist in securing proper functioning of the various communication systems. This interference mechanism would not generally constitute frequency assignment planning constraints.
Annex 7
from WP 9
Relevant Updates for the ICAO Handbook on the Band 117.975–137 MHz MHz
SECTION 7-II. CIVIL AVIATION FREQUENCY
ALLOCATIONS — ICAO POLICIES AND
RELATED INFORMATION
Band: 117.975–137 MHz
Service: Aeronautical mobile (R) service (air-ground and air-air communications, VHF voice and data)
Allocation:
MHz
117.975–137
Allocation to Services
Region 1
Region 2
Region 3
117.975–137
AERONAUTICAL MOBILE (R)
MOD 5.111 MOD5.200 5.201 5.202
Footnotes:
MOD 5.111 The carrier frequencies 2 182 kHz, 3 023 kHz, 5 680 kHz, 8 364 kHz and the frequencies 121.5 MHz, 156.525 MHz, 156.8 MHz and 243 MHz may also be used, in accordance with the procedures in force for terrestrial radiocommunication services, for search and rescue operations concerning manned space vehicles. The conditions for the use of the frequencies are prescribed in Article 31 and. (WRC-07)
The same applies to the frequencies 10 003 kHz, 14 993 kHz and 19 993 kHz, but in each of these cases emissions must be confined in a band of ±3 kHz about the frequency. (WRC-07)
SUP
SUP
MOD 5.200 In the band 117.975–137 MHz, the frequency 121.5 MHz is the aeronautical emergency frequency and, where required, the frequency 123.1 MHz is the aeronautical frequency auxiliary to 121.5 MHz. Mobile stations of the maritime mobile service may communicate on these frequencies under the conditions laid down in Article 31 for distress and safety purposes with stations of the aeronautical mobile service.(WRC-07)
5.201 Additional allocation: in Angola, Armenia, Azerbaijan, Belarus, Bulgaria, Estonia, the Russian Federation, Georgia, Hungary, Iran (Islamic Republic of), Iraq, Japan, Kazakhstan, Latvia, Moldova, Mongolia, Mozambique, Uzbekistan, Papua New Guinea, Poland, Kyrgyzstan, Slovakia, the Czech Rep., Romania, Tajikistan, Turkmenistan and Ukraine, the band 132–136 MHz is also allocated to the aeronautical mobile (OR) service on a primary basis. In assigning frequencies to stations of the aeronautical mobile (OR) service, the administration shall take account of the frequencies assigned to stations in the aeronautical mobile (R) service.
5.202 Additional allocation: in Saudi Arabia, Armenia, Azerbaijan, Belarus, Bulgaria, the United Arab Emirates, the Russian Federation, Georgia, Iran (Islamic Republic of), Jordan, Latvia, Moldova, Oman, Uzbekistan, Poland, the Syrian Arab Republic, Kyrgyzstan, Slovakia, the Czech Rep., Romania, Tajikistan, Turkmenistan and Ukraine, the band 136–137 MHz is also allocated to the aeronautical mobile (OR) service on a primary basis. In assigning frequencies to stations of the aeronautical mobile (OR) service, the administration shall take account of the frequencies assigned to stations in the aeronautical mobile (R) service.
SUP
SUP
SUP
ICAO POLICY
•No change to the allocations to the aeronautical mobile (route) service in this band.
•No changes to Footnotes and 5.200.
•No changes to the provisions relating to the use of the emergency channels 121.5 and 123.1 MHz.
•
•
•Promote measures for the deletion of Footnotes 5.201 and 5.202.
AVIATION USE: The band 117.975–137 MHz is the main communications band for line-of-sight air-ground communications and is used at all airports, for en route, approach and landing phases of flight and for a variety of short-range tasks for general aviation and recreational flying activities (e.g. gliders and balloons).
The band 118–132 MHz was first allocated to aviation in 1947. The extension of the band to 136 MHz was made in 1959, and the extension to 137 MHz was made in 1979.
To satisfy increased demand and frequency congestion in high-density traffic areas, the channel width has been reduced on four occasions (from 200 kHz to 100 kHz in the 1950s, to 50 kHz in the 1960s, to 25 kHz in 1972 (Seventh Air Navigation Conference) and finally to 8.33 kHz in 1995 (Special COM/OPS/95)). Frequency assignments and equipment standards may be chosen by regional agreement to suit local demand patterns.
Single channel simplex is the mode of operation. Double sideband amplitude modulation voice is the major modulation method. Data link communications , including air-to-air data, are being introduced in this band and are envisaged in the future to be used for routine communications. Voice capability, however, will remain to be required for non-routine communication.
ICAO has allotted the band to national and international services (see Annex 10, Volume V, Chapter 4, Table 4-1).
The aeronautical mobile (route) service is defined in 1.33 and in 43.1 of the Radio Regulations (see Attachment A) as “reserved for communications related to safety and regularity of flight between any aircraft and those aeronautical stations and aeronautical earth stations primarily concerned with flight along national or international civil air routes”. Public correspondence, as defined in RR 1.116, is prohibited under RR 43.4 in the bands allocated exclusively to the aeronautical mobile service.
Frequencies for aeronautical operational control (AOC) use are covered by the Recommendation at Annex 10, Volume V, Chapter 4, 4.1.8.1.3, which prescribes that frequencies will be selected from the band 128.825–132.05 MHz for this purpose, subject to regional agreement in areas where a scarcity exists. Control of communications content rests with the national licensing authority in accordance with Annex 10, Volume II, Chapter 5, 5.1.8.6 and 5.1.8.6.1 together with the note to 5.1.8.6. Aeronautical operational control (AOC) commuications are defined in Annex 10 as communications required for the exercise of authority over the initiation, continuation, diversion or termination of flight fot safety, regularity and efficiency reasons. AOC is part of the AM(R)S. Specifics for AOC is normally exercised by airlines; specific requirements for flight operations (including AOC) are contained in Annex 6.
Frequency 121.5 MHz is the aeronautical emergency frequency (Annex 10, Volume V, Chapter 4, 4.1.3.1) and is designated in the Radio Regulations (Chapter II and Appendix 13) for general distress and safety and emergency locator transmitter (ELT) purposes. It is used in the space system for search of vessels in distress and in the search and rescue satellite-aided tracking (COSPAS/SARSAT) system for search and rescue purposes. This use is being phased out and new COSPAS/SARSAT tracking is concentrated on 406.1 MHz.
Frequency 123.1 MHz is the frequency designated as the auxiliary to 121.5 MHz (Annex 10, Volume V, Chapter 4, 4.1.4 refers). This frequency is to be used as an auxiliary search and rescue frequency. The Radio Regulations also designate 123.1 MHz for general search and rescue purposes.
Frequency 123.450 MHz is the frequency designated for air-air communications between aircraft engaged in flights over remote and oceanic areas and while out of range of VHF ground stations.
To give low level coverage over a large area, offset carrier operation is employed in some areas (see Annex 10, Volume III, Attachment A to Part II, 1.2). Such systems, using up to five carriers in one channel, are possible with channel spacing of at least 25 kHz. Offset carrier systems can also be used with 8.33 kHz channel spacing, but are limited to two-frequency offset carrier systems.
VHF receivers are susceptible to interference from FM broadcast signals in the band 87–108 MHz. Annex 10, Volume III, Part II, specifies performance requirements to provide protection from this possibility (see Section 7-III). ITU-R.SM.1009 provides technical planning guidance.
COMMENTARY: The Special COM/OPS/95 discussed the shortage of assignable VHF channels necessary to support the growth in air traffic in the years ahead. This scarcity situation occurred in 1992 in the core area of Europe and is expected to occur in North America around 2007. [This should be updated] The Communications/Meteorology/ Operations (COM/MET/OPS) Divisional Meeting (1990) had earlier developed Recommendation 2/4 calling for a review and study of the congestion in the VHF band, and the AMCP, as tasked by the Air Navigation Commission, had examined and reported the situation in 1994 (AMCP/3 refers).
Note.— The core area in Europe includes Austria, Belgium, Denmark, France, Germany, Ireland, Luxembourg, Netherlands, Switzerland and the United Kingdom.
Channel spacing
The Special COM/OPS/95 foresaw a near-term improvement in the number of available channels VHF voice system based on 8.33 kHz channel spacing. Not all ICAO Regions would need to apply this new Standard. SARPs for 8.33 kHz channel spacing were adopted by the ICAO Council in 1996. Implementation of 8.33 kHz channel spacing is subject to regional agreement.
Implementation of 8.33 kHz channel spacing in a limited form, i.e. for upper airspace services initially, is proceeding in Europe under the aegis of ICAO, assisted by the European Organization for the Safety of Air Navigation (EUROCONTROL) in a coordination/planning role. The mandatory carriage of 8.33 kHz radio equipment was introduced above FL245 in the ICAO EUR Region in October 1999. Initially, 7 Core Area States enforced mandatory carriage. As part of the Horizontal Expansion programme, a further 23 ICAO EUR Region States enforced mandatory carriage from October 2002. In a response to increasing VHF congestion and the status of potential alternatives, the European Air Navigation Planning Group (EANPG) decided to proceed with the vertical expansion below FL245. Full implementation of en route and later airport use (approach and landing) is likely to take a number of years and may be effectively completed in the latter years of this decade. Further expansion of the use of 8.33 kHz channel spacing in lower airspace is planned in Europe.
Many other Regions can continue to meet their requirements for VHF channels using 25 kHz spacing for some years ahead without the compelling requirement to convert to other systems.
Use of data in air-ground communications
The CNS/ATM concept placed considerable reliance on the use of air-ground data for pilot/controller exchange of data to supplement the use of voice for certain categories of messages, primarily for routine communications between pilots and ATC. SARPs for VDL Mode 2 have been incorporated in Annex 10. VDL Mode 2 will become the prime data system for the immediate future. The SARPs for VDL Mode 3 and Mode 4 have also been finalized, adopted and incorporated in Annex 10.. Frequency planning guidance material for VDL Mode 2 and Mode 4 is presented in Volume II of this Handbook.
Band capacity issues
In high-density congested areas such as Europe and North America, the requirement for VHF channels continues to increase. In regular ATC use under normal circumstances, the maximum utilization of a channel dedicated to an ATC sector is around 10 to 20 per cent of the time due to other essential tasks performed by the controller. The use of air-ground data should enable an improvement in utilization of the spectrum, which should be beneficial and delay the time point of spectrum exhaustion. Further expansion of spectrum for short-range, line-of-sight communications as demand increases will meet problems due to the general shortage of frequencies in all parts of the radio frequency spectrum. The strategy and options to deal with this situation require early attention.
Use of the band by other services
The band extensions at 132–136 MHz and 136–137 MHz were agreed to many years ago in ITU but still support other services (such as the AM(OR)S) existing at that time and now operating under footnote provisions. A policy of band clearance to provide unrestricted use is now essential.
Footnote 5.202 relates to the use, for national purposes, for off-route (OR) services, which were widespread prior to the agreement in 1959 to release 132–136 MHz in most countries for exclusive use by the (route) service. In areas where the (OR) service operates on these frequencies, coordination procedures agreed to in the past have been satisfactory up to now. With increasing and intensive use of the frequencies in the band for AM(R)S purposes, it is likely that this (OR) use may become a problem, in which case it will become essential to press for a cessation of this use.
WRC-07
WRC-07 removed from tha band three footnote allocations (re. 5.203 (meteorological satellite), 5.203A (fixed and mobile, except aeronautical mobile R) and 5.203B (fixed and mobile, except aeronautical mobile) from the band 136-137 MHz. 5.198 whic