International Civil Aviation Organization
WORKING PAPER / ACP-WGF/16/WP-19
07/06/05
AERONAUTICAL COMMUNICATIONS PANEL (ACP)
16th MEETING OF ACP WORKING GROUP F
Montreal, Canada 11-15 December 2006
Agenda Item 4: / Interference from non-aeronautical sourcesInterference levels for MLS receivers
(Presented by the Secretary)
SUMMARYThis paper presents some considerations concerning the interference levels into MLS receivers
ACTION
Action proposed is in paragraph 6
1. Results from NSP/SSG meetings 2006
1.1At the NSP/SSG meeting held from 9-11 May 2006 it was agreed that the aggregate interference that could be allowed into an MLS receiver is -130 dBm in a 150 kHz band (-124.5 dBW/m2), until additional evidence is made available to justify the revision of this value. The meeting further agreed to its action item SSG9/15, indicating that France would undertake measurements to investigate the impact of noise-like signals on the performance of MLS receivers.
1.2At the NSP/SSG meeting held from 10-13 October 2006, the SSG noted a proposal to relax this value to -120 dBm/150kHz, but the group agreed that bench tests need to be carried out before the SSG can conclude on any relaxation of the value for aggregate interference which was agreed at its meeting in May 2006 (i.e. -130 dBm in a 150 kHz band). At the earliest, results from actual measurements, if any, are expected to be available by March 2007.
1.3For the third time, a paper has been presented, requesting the ACP/WGF-NSP/SSG to revise its earlier findings and to increase the maximum permissible aggregate interference into an MLS receiver from -130 dBm to -120 dBm. And, again, no test results have been presented.
1.4In ICAO’s view, significant further work needs to be done substantiating this proposal. Also, the views of MLS industry need to be available for consideration. This will require the time necessary for developing a balanced and view that would secure protection of all MLS receivers. The current value of -130 dBm for aggregate interference would protect MLS adequately. The Secretariat is of the view that, until further work is completed, this value needs to be retained as the basis for further work, in particular in ITU in preparation for the World Radiocommunication Conference 2007. Therefore, ICAO needs to express the need for retaining the value of -130dBm/150 kHz, until further review of this value in the NSP on amending this value has been concluded.
1.4Further work in ICAO regarding the protection and use of the 5 GHz band need to take this into consideration.
2.The current value of -130 dBm/150 kHz was established in 1997 and is contained in ITU-R Recommendation S.1342. This completing work on the protection of MLS from interference from the Fixed Satellite Service to which the band 5091-5150 MHz was allocated in 1995 (Re. Radio Regulations, provision 5.444A).
2.1At that time, the only interferer considered were ground stations operating in the Fixed Satellite Service; due to the low number of ground stations, only one station was considered to interfere with an MLS frequency assignment.
3. In 2002, ITU-R Recommendation M.1582 was approved. This Recommendation addresses coordination distances to secure protection of MLS receivers from interference that can be caused by ground stations operating in the Radionavigation Satellite Service (RNSS), operating in the band 5000-5010 MHz. The same methodology as was approved in ITU-R Rec. S.1342 was agreed. At that time, no consideration was given to the fact that, MLS receivers could be interfered by transmissions from BOTH FSS Ground stations and RNSS ground stations.
4At WRC-2003, footnote 5.433B as follows was added to the Regulations addressing the interference from space stations in the Aeronautical Radionavigation Service (MLS).
Note. — 5.443BIn order not to cause harmful interference to the microwave landing system operating above 5030MHz, the aggregate power flux-density produced at the Earth’s surface in the band 5030-5150 MHz by all the space stations within any radionavigation-satellite service system (space-to-Earth) operating in the band 5010-5030MHz shall not exceed –124.5dB(W/m2) in a 150 kHz band. In order not to cause harmful interference to theradio astronomy service in the band 4990-5000 MHz, radionavigation-satellite service systems operating in theband 5010-5030MHz shall comply with the limits in the band 4990-5000 MHz defined in Resolution741 (WRC03).(WRC-03)
4.2ICAO considers this footnote to refer to the aggregate level of interference from all satellites within a single system and as such can not be understood as a single entry limit..
5.In the three cases of protection required to be given to MLS, no consideration was given to the simultaneous occurrence of these sources of interference.
6.The proposed addition of (aeronautical) mobile services in the MLS band, requires to consider the interference levels (-130dBm or -124.5 dBW/m2) as agreed in these ITU-R Recommendations as well as in RR 5.443B as aggregate to all possible interferences. Further work, including measurement results and involving industry, needsto be undertaken before any increase in interference level can be agreed
6.1Should the current text of ITU-R Recommendations S.1342 and M.1582 require further clarification, relevant proposals should be developed for consideration by ITU-R Study Group 8. Similarly, footnote 5.443B should be amended to clarify.
RECOMMENDATION ITU-R S.1342[*],[**]
Method for determining coordination distances, in the 5 GHz band,
between the international standard microwave landing system
stations operating in the aeronautical radionavigation service
and non-geostationary mobilesatellite service stations
providing feeder uplink services
(Question ITU-R 244/4)
(1997)
The ITU Radiocommunication Assembly,
considering
a)that the aeronautical radionavigation service is allocated on a primary basis in the band 5000-5250 MHz;
b)that the band 5000 to 5150 MHz is to be used for the operation of the international standard MLS for precision approach and landing. The requirements for this system shall take precedence over other uses of this band as per No. S5.444 of the Radio Regulations (RR). For the use of this band, RR No. S5.444A and Resolution 114 (WRC-95) from the World Radiocommunication Conference (Geneva, 1995) apply;
c)that the WRC-95, added a co-primary allocation for the fixed-satellite service (FSS) (Earth-to-space) in the 5091-5250 MHz band, limited to feeder links of non-geostationary-satellite (nonGSO) systems in the mobile-satellite service (MSS), and subject to coordination under Resolution46 (Rev.WRC-95) (No. S9.11A);
d)Resolution 114 (WRC-95), which, inter alia:
–“urges administrations to take all practicable steps to avoid mutual interference between stations of the ARNS and stations of the fixed-satellite service (FSS)”, and
–“instructs the ITU-R to study the technical and operational issues relating to sharing of this band between the ARNS and the FSS providing feeder links of the non-geostationary-satellite mobile-satellite service (Earthtospace)”;
e)that RR No. S4.10 provides recognition that special measures are required for the protection of radionavigation and safety services,
recognizing
a)that the FSS providing feeder links for non-GSO MSS has been allocated to the frequency band 51505250MHz, as well as the frequency band 5091-5150 MHz in the short term, in order to accommodate already identified requirements;
b)that the methods contained herein are based on current specifications for international standard MLS receiving equipment;
c)that ICAO is currently considering the need for protecting international standard MLS and other ARNS systems operating in the band 5000-5150MHz from interference caused by unwanted emissions from feeder link earth stations operating in the band 5150-5250MHz (related to MLS) and in the band 5091-5250MHz (related to ARNS other than MLS) (see Note 1).
NOTE1–Current internationally-standardized specifications are based on spectrum allocations in existence prior to WRC-95. Current and future MLS hardware may offer additional rejection of out-of-band emissions with respect to existing specifications. Additional rejection, if present and standardized in all MLS avionics, may affect Roob,
recommends
1that the method for determining coordination distances between international standard MLS stations operating in the band 5030-5091MHz and FSS earth stations providing Earth-to-space feeder links in the 5091-5150 MHz band, described in Annex 1, should be used.
ANNEX 1
Method for determining coordination distances
This Annex sets forth a method for determining coordination distances relative to current and planned MLS stations that may be used to enable implementation of MSS feeder link earth stations. Provisionally, coordination will not be required between MSS feeder link earth stations and MLS transmitter sites at the same altitude and which are separated by more than 450 km (243 nmi). Beyond 450km, MLS airborne stations are expected to be sufficiently beyond the radio lineofsight of the MSS feeder link earth station to protect the MLS. This coordination distance is subject to further review.
For separation distances provisionally less than 450 km, the need for coordination is identified and dependant on the mitigation factors a) to e), as identified below. Range separation triggers for coordination may be defined as a result of internationally-standardized specifications for MLS out-of-band and inband interference susceptibility criteria (seeNote1, § c) of recognizing). For the
purpose of this method, the terms “out-of-band” and “inband” are relative to the MLS band 50305091 MHz (see also item e) below). These triggers may be denoted Roob for the out-of-band range separation trigger, and Rin for the inband range separation trigger, as defined below:
Roob (km) (4.775 10–6) 10((P191)/20) 43 (1)
where P1 is the total e.i.r.p. (dBW) of non-GSO feeder link earth station assignments and proposed assignments in the band 5091-5150 MHz
Rin (km) (4.775 10–6) 10((P2160)/20) 43 (2)
where P2 is the peak non-GSO MSS feeder link earth station e.i.r.p. density (dB(W/150kHz)) in the band 50305091MHz at assigned MLS frequencies
where the e.i.r.p. density P2 is referred to as an interference evaluation bandwidth, a value not exceeding 150 kHz (seeNote1). If both Roob and Rin are less than the planned range based on the candidate MSS feeder link earth station location and current or planned MLS transmitter location(s), MLS operations will be unaffected and further analysis and coordination is not required. If either Roob or Rin exceeds the planned range based on the candidate MSS feeder link earth station location and current or planned MLS transmitter location(s), further analysis and coordination is required. Some factors identified below may be considered in a more detailed analysis:
a)site-specific signal attenuation factors such as terrain blocking and radio horizon;
b)increased filtering of the transmitted MSS feeder link earth station uplink signal;
c)antenna orientation and directive gain characteristics of MSS feeder link earth station transmit antenna;
d)alternative locations for the MSS feeder link earth station;
e)in regions where current and projected MLS deployments are expected to be limited, consideration may optionally be given to the additional frequency separation afforded by MLS operation in the lower channels of the MLS channel plan extending from 5030 MHz to 5091 MHz. This option should be at the discretion of the affected national authorities.
Items a) through d) may affect the power level of MSS feeder link earth station emissions in the direction of MLS service volumes. Item e) may affect the operating frequency(ies) of MLS. This, in turn, may reduce the level of relevant MSS spurious emissions in the 2.4 MHz band centred on the MLS frequency assignment, which affects Rin. Additional factors may be considered on an individual basis; however, the need to maintain the reliability and integrity requirements of MLS, consistent with the safety of flight service it provides, needs to be addressed.
NOTE1–ICAO has indicated that on the basis of the current design specifications for the MLS receiver, a 150kHz receiver IF bandwidth is to be used when determining coordination distances. ICAO is requested to urgently determine if adjustments to this specification can be made that would facilitate improved FSS feeder link earth station coordination, if practicable, while preserving the integrity of the MLS system.
1
ACP-WGW01/WP-01RECOMMENDATION ITU-R M.1582[*]
Method for determining coordination distances[**], in the 5 GHz band, between the international standard microwave landing system stations operating in the
aeronautical radionavigation service and stations of the
radionavigation-satellite service (Earth-to-space)
(2002)
The ITU Radiocommunication Assembly,
considering
a)that the band 5000-5250 MHz is allocated to the aeronautical radionavigation service on a primary basis;
b)that the band 5030-5150 MHz is intended for the operation of the international standard microwave landing system (MLS) for precision approach and landing; the requirements for this system shall take precedence over other uses of this band in accordance with No. 5.444 of the Radio Regulations (RR);
c)that the World Radiocommunication Conference (Istanbul, 2000) (WRC2000) added a coprimary allocation for the radionavigation-satellite service (RNSS) (Earth-to-space) in the 50005010 MHz band;
d)that emissions from RNSS stations may cause interference to aeronautical MLS receivers during approach and landing;
e)that the MLS can be well protected through the implementation of an adequate separation distance between RNSS (Earth-to-space) transmitters and MLS receivers, and other mitigation techniques;
f)that RR No. 4.10 provides recognition that special measures are required for the protection of radionavigation and safety services,
recognizing
a)that the methods contained herein are based on current specifications for international standard MLS receiving equipment,
recommends
1that the method for determining coordination distances between international standard MLS stations operating in the band 5030-5150MHz and RNSS (Earth-to-space) stations in the 50005010MHz band, described in Annex 1, should be used.
Annex 1
Method for determining coordination distances
This Annex sets forth a method for determining coordination distances relative to current and planned MLS stations that may be used to enable implementation of stations of the RNSS (Earth-to-space). Coordination will not be required between RNSS (Earth-to-space) and MLS transmitter sites at the same altitude and which are separated by more than 450km. Beyond 450km, MLS airborne stations are expected to be sufficiently beyond the radio line-of-sight of the RNSS (Earth-to-space) earth station to protect the MLS. This coordination distance is subject to further review.
For separation distances provisionally less than 450km, the need for coordination is identified and dependent on the mitigation factors a) to e), as identified below. Range separation triggers for coordination may be defined as a result of internationally standardized specifications for MLS outof-band and inband interference susceptibility criteria. For the purpose of this method, the terms “out-of-band” and “inband” are relative to the MLS band 5030-5150 MHz (see also item e) below). These triggers may be denoted Roob for the out-of-band range separation trigger, and Rin for the inband range separation trigger, as defined below:
(1)
where P1 is the total e.i.r.p. (dBW) of RNSS (Earth-to-space) earth station in the band 50005010MHz, based on free space propagation from the RNSS station to an MLS equipped aircraft within the MLS service volume.
(2)
where P2 is the peak RNSS (Earth-to-space) earth station e.i.r.p. density (dB(W/150kHz)) in the band 50305150MHz, based on free space propagation from the RNSS station to an MLS equipped aircraft within the MLS service volume, and an MLS inband interference threshold of dBW.
When performing this initial calculation care must be taken to ensure that no fixed-satellite service earth stations, which have been coordinated using Recommendation ITU-R S.1342 or other RNSS (Earth-to-space) earth stations, lie within the coordination distance of the MLS. If such an earth station exists, then the potential aggregate effect must be taken into account.
The MLS service volume is 43 km in radius with the MLS transmitter at the centre. If both Roob and Rin are less than the planned range based on the candidate RNSS (Earth-to-space) earth station location and current or planned MLS transmitter location(s), MLS operations will be unaffected and further analysis and coordination is not required. If either Roob or Rin exceeds the planned range based on the candidate RNSS (Earth-to-space) earth station location and current or planned MLS transmitter location(s), further analysis and coordination is required. Some factors identified below may be considered in a more detailed analysis:
a)site-specific signal attenuation factors such as terrain blocking and radio horizon;
b)increased filtering of the transmitted RNSS earth station uplink signal;
c)antenna orientation and directive gain characteristics of RNSS (Earth-to-space) earth station transmit antenna;
d)alternative locations for the RNSS (Earth-to-space) earth station;
e)in regions where current and projected MLS deployments are expected to be limited, consideration may optionally be given to the additional frequency separation afforded by MLS operation in the upper channels of the MLS channel plan extending from 5030MHz to 5150 MHz. This option should be at the discretion of the affected national authorities.
Items a) through d) may affect the power level of RNSS (Earth-to-space) earth station emissions in the direction of MLS service volumes. Item e) may affect the operating frequency(ies) of MLS. This, in turn, may reduce the level of relevant RNSS spurious emissions in the 2.4 MHz band centred on the MLS frequency assignment, which affects Rin. Additional factors may be considered on an individual basis; however, the need to maintain the reliability and integrity requirements of MLS, consistent with the safety of flight service it provides, needs to be addressed.
[*]The Administrations of France, United Kingdom of Great Britain and Northern Ireland, and South Africa (Republic of) reserve their opinion on this Recommendation.
This Recommendation may require updating if new information regarding MLS receiver specifications, or other information regarding protection of MLS or ARNS systems, becomes available.
This Recommendation should be brought to the attention of Radiocommunication Study Group8 and the International Civil Aviation Organization (ICAO).