Resolution 606

1

• Resolution 606
• Interference from RNSS to radars in the 1215
  1300 MHz band
• Philippe GERARD
• Agence Nationale des Fréquences
• Gerard_at_anfr.fr
• Mars 2001
• AMCP WGF/6-WP/39

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Resolution 606 protection of radars in 1215
1300 MHz band
Protection of radiolocation resolution 606
Protection of MLS resolution 603
Compatibility with MSS
Sharing with MIDS
OOB emissions from radars
L2
L1
L5/E5
E6
C
L2
L1
L5/E5
C
1215 MHz
1260 MHz
1559 MHz
1610 MHz
1300 MHz
5010 MHz
5030 MHz
1164 MHz
Protection of radiolocation resolution 607
Sharing between RNSS and ARNS resolution 605
Protection of radioastronomy resolution 604
3
RES 606 COM5/20

• considering
• a) that this conference has decided to introduce
  a new allocation for the radionavigation-satellite
  service (space-to-Earth) in the frequency band 1
  260-1 300 MHz
• b) that in the band 1 215-1 260 MHz
  radionavigation-satellite service
  (space-to-Earth) systems have been successfully
  operated for a considerable time in a band used
  by radars
• c) the importance of the radionavigation service
  authorized in certain countries in accordance
  with No. S5.331 and of the radiolocation service,
  and the need for adequate protection and
  continued operation of these services throughout
  the band 1 215-1 300 MHz,

4
RES 606 COM5/20

• resolves
• 1 that no additional constraints shall be placed
  on radionavigation-satellite service
  (space-to-Earth) systems operating in the band 1
  215-1 260 MHz
• 2 to recommend that WRC-03 review the results of
  the studies in invites ITU-R and take appropriate
  action,

5
RES 606 COM5/20

• invites ITU-Rto conduct, as a matter of urgency
  and in time for WRC-03, the appropriate
  technical, operational and regulatory studies,
  including an assessment of the need for a power
  flux-density limit concerning the operation of
  radionavigation-satellite service
  (space-to-Earth) systems in thefrequency band 1
  215-1 300 MHz in order to ensure that the
  radionavigation-satellite service
  (space-to-Earth) will not cause harmful
  interference to the radionavigation and the
  radiolocationservices,
• instructs the Secretary-General
• to communicate the contents of this resolution to
  ICAO for such actions as it may consider
  appropriate and to invite ICAO to participate
  actively in the study activity identified under
  invites ITU-R.

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Resolution 606

• ITU-R
• Last WP 8D October 2000
• Next WP 8D end of May 2001
• CEPT
• Last SE 28 January 2001
• Next SE 28 2 May 2001 (to prepare next WP 8D)

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Resolution 606 last WP 8D calculation of
pfd for GPS and GLONASS(doc 8D/18 E)CEPT
proposed Pfd limit of -133 dBW/m2/1MHz(GALIL
EO E6,40 MHz, -155 dBW ?-134 dBW/ m2 /1MHz)
8
SE 28 worst case pfd
Calulated from rec. ITU- R M 1463 Pfd limit
-161 !!!
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objectives of a statistical approach

• - The worst case scenario uses the gain of the
  main beam of the radars
• - Satellites are not always in the main beam
• Objective of further works
• to present a statistical view of harmful
  interference
• to propose a pfd limit acceptable for everybody

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Resolution 606 statistical approach

• Assumptions
• Radar model
• Models of satellites constellations
• GPS
• GALILEO
• Harmful interference criteria to radars
• recommendation ITU-R M 1461
• general consideration

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Resolution 606 statistical approach

• Radar model
• Rec ITU-R M 1463 does not give enough information
  on radiation pattern of radars
• ?Measured radiation pattern of a civil aviation
  radar
• - Calculated PFD for
• no harmful interference
• -154 dBW/m2/1MHz

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Methodology

• Modelisation of a satellite constellation
• GALILEO
• 27 satellites 3 orbital plans
• Angle of orbital plans 55
• right ascension 0 120 240
• Anomalies every 40 from 0 13.33 26.66
• Altitude 23600 km
• GPS
• 24 satellites, 6 orbital plans
• Angles of orbital plans 55
• Right ascension 0 k 60
• Anomalies every 90
• Altitude 20 200 km

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Methodology

• Calculation of satellite elevation
• - For one satellite
• - For all satellites of an orbit
• - For all satellites of the constellation
• (here for a latitude of 47 N)

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Maximal gain

• Gain for one satellite
• Max gain for the whole constellation

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Methodology

• Distribution of Gain
• prob (gainltg)
• period (gainltg)/total period

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Methodology harmful interference criteria

• Rec. ITU-R M 1461 threshold I/N -6 dB
• From simulations
• Elevation, azimuth function of time
• ?Several minutes per degree.
• - Between several antenna rotations, the
  satellite azimuth and elevation can be considered
  as fix elements
• - from the operator point of view, when there is
  jamming in a direction, this direction is jammed
  all the time and not only the percentage of tim
  the radar scans in this direction
• - The harmful interference period is the total
  period in which I/N superseded the threshold for
  at least one direction results from the
  vertical radiation pattern
• - The horizontal radiation pattern gives the
  width of the jammed area.

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Methodology

• Harmful interference ?I/N -6dB (rec ITU-R M
  1461)
• For a given PFD
• Prob (interference) prob (Gain gtPFDwcGmax -
  PFD)
• With
• PFDwc PFD worst case -154 dBW/m2/1MHz for our
  radar

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Resolution 606 statistical approach

• First results
• For pfd as proposed, probability of harmful
  interference is above 20 for one satellite !!!

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Resolution 606 statistical approach

• First results
• For pfd as proposed, probability of harmful
  interference is almost 100 for the
  constellation !!!

20
Resolution 606 statistical approach
Three orbital plans
4 periods One orbital plan

• Attempts of explanations
• Most of the time, there are one or more satellite
  with a low elevation
• ?high gain of radiation pattern

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Resolution 606 statistical approach

• But
• This approach gives similar results with GPS
  today
• No interference seen until now
• So, WHY ???
• Bad assumptions ?
• Harmful interference criterias ?
• Radar signal processing
• Wrong models ?

22
Resolution 606 statistical approach

• But
• This approach gives similar results with GPS
  today
• No interference seen until now
• So, WHY ???
• Bad assumptions ?
• Harmful interference criteria ?
• Radar signal processing
• Wrong models ?

23
Resolution 606 Present problem

• WHY are there no interference declared today
  between GPS and radars in L2 band ?
• Wrong assumptions ?, false calculations ?
• ? more studies must be made
• Not enough data about radars ?
• Radiation patterns
• Interference measurement
• Interference criteria not adequate ?

24
Resolution 606 more information from NATO

• US Same approach
• Calculations with ITU-R M 1461 and M 1463
  recommendations predicts interferences from
  current GPS, but no interference to date
• Need to examine other methodologies
• Study with 8 US radars
• Statistical approach, study of different
  criterias
• Operational tests
• To configure a GPS satellite to transmit C/A
  signal on L2 (1227 MHz)