17-19 feb 2004nairobi aeronautical spectrum seminar 1 itu activities on interference itu and related...

17-19 Feb 2004 Nairobi Aeronautical spectrum Seminar

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ITU activities on interference

ITU and related organization working groups involved Work accomplished in the form of ITU-R

recommendations dealing with the protection of aeronautical services

On-going work:Ultra Wide Band Systems (UWB) potential threatsWRC-03 initiated study on FM broadcasting and

GBAS and VDL M4 compatibility ITU-R 8B initiated feasibility study on the use of

statistical and operational aspects related to radar protection criteria

Presented by Alain DELRIEU, French [email protected]


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WORKING GROUPS INVOLVED on INTERFERENCE THREATS TO AVIATION

SYTEMS and PREVENTION Mainly:

ITU-R 8B : Maritime, GMDSS, Aeronautical Mobile Service and radiodetermination (radiolocation & radionav.) service

ITU-R 8D : All mobile services and radiodetermination satellite services

But also : ITU-R 8F : IMT-2000 and beyond ITU-R 4B : Fixed satellite service and performances, satellite news

gathering CEPT , e.g. SE and FM groups

Study work-items usually result in Recommendations , approved by Radio Assemblies

Usually initiated by WRCs , but also directly triggered by ITU-R study groups


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ACCOMPLISHED work : ITU-R Rec. SM 1535

Object: The protection of safety services from unwanted emissions

Recognizing Safety services need special attention:States are obligated under R.R. 4.10, to take

measures to insure freedom of harmful interferenceProtect the reception of weak signals against out-of-

band and spurious emissions from other systemsNeed to Complement general R.R emission limits by

standards or applicable ITU-R RecommendationsRelevant to Aviation are ITU-R M.441, 960,1234,

1317,1318,1463,1464,1342 S.1342 and SM 1009


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ITU-R Rec. SM 1535 re “safety services protection”

Recommends:1.Appropriate spectrum management techniques2. Increased consultation btwn all concerned services

and operators (safety services and others, non-safety)3.Use of interference mitigation techniques by other

(non safety) services4. Use of interference mitigation techniques by safety

services5.Use of Out of band limitations by other services6.Safety analyses on a case by case basis :

To achieve a required integrity level under all operational conditions


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ITU-R Rec. SM 1535 re “safety services protection” (cont’d)

General safety criteria for the protection of aeronautical services Need for quantitative harmful interference threshold specific to ea.

system based on appropriate safety criteria Technical planning criteria to provide interference protection:

• Usually available within aviation to prevent interference between aeronautical systems, but,

• Generally absent for non-aviation services and systems• Consequently ea. potential non-aeronautical interfering system needs

individual attention

Well known sources of man-made emissions and interference include:• LF/MF AM broadcasting• Video-cable distribution system• Industrial, scientific and medical equipment• Power(utility) line distribution


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5 GHZ band sharing between ARNS/MLS and FSS feeder links to for non GSO

Rec. ITU-R S.1342 : set coordination trigger distance for MLS vs FSS/feederlink, in the 5 Ghz band (5091-5150 MHz)

MSS is co-primary in the 5091-5150 Mhz since WRC-95

distance trigger for mandatory coordination is 243 NM (450 km) or less

• Also MLS range triggers for o-o-b and in-band interference susceptibility, Roob and Rin

Consider mitigation factors :• look for site-specific blocking and FSS filtering


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Electronic news gathering/outside broadcasting sharing with the 2.7-2.9 GHz ARNS Radar band

CEPT/ECC developed an ad-hoc Recommendation, which is not yet at ITU-R level

Background: ENG/OB in Europe has been forced out of bands now allocated to land mobile services (IMT-2000) and is being digitized

Two potentially interfering mechanisms Overloadd Rcvr’s front-end causing saturation/gain loss Generated 3rd order intermod products falling within radar IF band

Work study reported in CEPT/ECC Report 006 and ECC REC (02)09, allowing band-sharing on conditions: Nationally, with exclusion zones, 10 Km radar-centered Required coordination in case ENG/OB exceeds a specific threshold of

– 2dBµV/m, within or at a country borders Note : in co-channel case, the threshold trigger distance exceeds radio-

horizon Only a few European countries are proposing this band sharing


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Feasibility study of MSS terminal sharing with GPS/L1 and GLONASS

WRC-97 considered an MSS co-primary allocation: To Mobile Satellite Service (INMARSAT-proposed Horizon) With RNSS in the band 1559-1567 MHZ

That conference adopted Res 220 to study: Technical criteria Operational and safety requirements in order to determine if sharing btwn RNSS, GPS/L1 and GLONASS ,

in 1559-1610 MHz, and MSS , in 1559-1567 was feasible

WRC-2000, on the basis of a.m. study concluded : The required PFD level to protect RNSS cannot be met by the proposed

MSS system terminals Conclusion: sharing not possible to protect present and future GNSS


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RNSS/GNSS and ARNS/DME Band sharing decided at WRC-03

WRC-2000 introduced a co-primary allocation to RNSS: In the DME sub-band 1164-1215 MHz With a provisional PFD limit : -115 dBW/m2 in any 1 Mhz

Invited ITU-R , under Res 605 to study, for WRC-03: appropriate technical, operational and regulatory matters to confirm compatibility btwn RNSS and ARNS(DME) Including the determination of an aggregate PFD limit

WRC-03 endorsed ITU-R studies done since WRC-00, in particular The principle and value of an aggregate (several RNSSs)

equivalent PFD at -121.5 dBW/m2/MHz Radio-Comm. Assembly-03 approved Rec M.1642, giving:

Methodology to assess max aggregate ePFD for all contemplated RNSS systems (GPS/L5 + GALILEO + 3 others)


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LINK MARGIN FOR SAFETY OF LIFE SERVICES

Need to set aside adequate transmission link margin has long been recognized within ITU: For radio navigation service, typically 6 to 10 dBs Critical for SOL applications to mitigate RF interference easily not quantifiable

but real Rec M. 1318 deals with RNSS protection in the band 1559-1610:

” extra margin of protection” against factors like multipath ARNS: A prior Rec. IS .1009 recalls :

ICAO adopted 8 dB safety margin for ILS =>to verify system performance with RFI and ILS carrier reduced by safety

margin RNSS/GNSS uses wideband modulation, ARNS/ILS and MLS narrowband:

Critical factor is C/N and the Satellite carrier is relatively fixed contrary to LIS and MLS

If RFI is reduced by 6 dB , the C/N is up by only 2.5 dB vs 6dB for ILS & MLS Rec M. 1343 defines a 5.6 dB margin for RNSS protection against non-

aeronautical RFI


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CONSIDERATIONS ON SAFETY MARGIN SIZING : REC ITU-R M.1477

Allowable aggregate RFI from non-aeronautical : must be significantly below the design interference theshold 6 DB value for aeronautical services is in line with other safety services Needed to account for all aeronautical design uncertainties

-140 dB(W/MHz) design threshold for SBAS Receiver for CAT I precision approaches

Hence a Threshold of -146 dB(W/MHz) for all non-aeronautical aggregate interference

Note : a GNSS RCVR in acquisition mode it is 6 dB less immune Additionnal margins may be required, depending on:

Operational requirements including accuracy, availability of service, continuity and integrity

Configuration of RNSS including augmentations Future source of RFI


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INTERFERENCE RISK ALLOCATION AND SAFETY COMPLIANCE

Interference allocation : the methodology employed for communication networks design is not acceptable as based on service unavailability (in the few % range)

Aeronautical systems must be designed to handle very rare events ,of the order of 1x10^-6 / hour

Any ARNS/RNSS proposal must include failure modes analysis

And must address how to maintain overall safety performance despite ageing


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The UWB challenge : compatibility with existing radiocommunication services

Ultra Wideband System: Transmist low power radio signal with Very short duration (order of few ns even less)

ITU groups involved in the UWB studies:

Question ITU-R 226/1: Spectrum management framework related to the introduction of ultra-wideband devices;

- Question ITU-R 227/1: Compatibility between ultra-wideband devices and radiocommunication services

4 Working groups have been set-up: WG 1 collects and documents key features, - WG 2 is addressees UWB compatibility issues; - WG 3 prepares a spectrum management framework as guidance to

Administrations; - WG 4 develops appropriate measurement techniques for UWB emissions


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Compatibility study between FM broadcasting and aeronautical systems,

GBAS and VDL Mode 4 WRC-03 permitted the use of the band

108-117.975 by ARNS GBAS and aeronautical VDL Mode 4

It restricted the use of the band to the upper sub-band 112-118 Mhe

The “opening” of the lower sub-band is dependant upon study results:Compatibility of a.m. systems with FM

broadcasting, analog and digital format


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NEW STUDY ITEM : Feasibility of using statistical and operational aspects to define

radar protection criteria At its November 2003 meeting ITU-R Working Party 8 B

discussed the feasability of the use of statistical and operational aspects in the protection criteria for radio-determination radar systems.

During the ITU-R study period 2000-2003, WP 8B conducted several studies related to the compatibility between radio-determination radar systems and other services/systems

The objective of this work programme is to identify protection criteria for radar systems taking into account statistical and operational aspects of radar systems and other relevant parameters


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CONCLUSIONS

The Aviation community benefits from ITU-R work aiming at establishing protection criteria for safety-related services

And should participate fully to the work of ITU groups By bringing in “real” operational experience A value of 6 dB margin of safety is the minimum widely

accepted within ITU-R and ICAO fora. The study-item on feasibility of a statistical approach to

set radar protection ratios should receive full attention and participation from ICAO members

17-19 feb 2004nairobi aeronautical spectrum seminar 1 itu activities on interference itu and related...

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