Transcript Radiosonde Spectrum Issues Presented by David Franc U.S. National Weather Service October 8, 2002

Radiosonde Spectrum Issues
Presented by David Franc
U.S. National Weather Service
October 8, 2002
Outline
• General Technical Information (D. Franc)
– Definitions
– Interference Protection Criteria
– Radiosonde Technology
• 400.15-406 MHz (J.Nash)
– Discussion of operations
– Proposed changes to band
• 1668.4-1700 MHz (D. Franc)
– Discussion of Operations
– Proposed changes to band
Definitions
• Radiosondes fall under the ITU radio
service of meteorological aids (metaids)
– Meteorological aids service: a
radiocommunication service used for
meteorological , including hydrological,
observations and exploration
• Dropsondes and rocketsondes are also part
of the metaids service
Metaids Frequency Bands
• Two common bands are used for metaids
– 400.15-406 MHz (primary allocation)
– 1668.4-1700 MHz (primary allocation)
• Other bands identified in ITU Radio Regulations
(not covered in this workshop)
–
–
–
–
2.025-2.045 MHz (secondary allocation, ITU Region 1)
27.5-28 MHz (primary allocation)
153-154 MHz (secondary allocation, ITU Region 1)
35.2-36 GHz (primary allocation)
Metaids Bands – Additional
Information
• The Handbook on Use of Radio Spectrum
for Meteorology has additional information
– Section 3.1: Discussion of bands that are
allocated for metaids operations
– Sections 3.6.4 – 3.6.6: Discussion of why
multiple bands are required
Working Party 7C
• Working Party 7C is the ITU-R working
Party responsible for development of
metaids protection criteria and conducting
studies regarding metaids systems
• Working Party 7C also is responsible for
passive and active remote sensing and
meteorological satellite data links
Metaids Interference Protection
Criteria
• ITU-R Recommendation SA.1263 specifies the
maximum interference level that allows
radiosonde systems to still meet performance
objectives
• Level based on margin in radio link at maximum
range
– Margin is excess receive power above minimum
receive threshold
– A small percentage of the margin is taken by
interference
Metaids Interference Protection
Criteria (cont)
• Criteria are different for the two bands, 400.15406 MHz and 1668.4-1700 MHz
• Criteria value is assumed to apply at receiver input
connector
• Criteria are specified as two types:
– Short term: less restrictive value that can only be
exceeded for a very small percentage of time
– Long term: More restrictive value that can be exceeded
for up to 20% of time – still allows reliable operation of
system
Summary of Metaids Interference
Protection Criteria (SA.1263)
400.15-406
MHz
Omni Antenna
400.15-406
MHz
Directional
Antenna
1668.4-1700
MHz
Directional
Antenna
Short Term
Criteria- no more
than 0.2 % time
-141.9 dBW
-140.6 dBW
-135.3 dBW
Short Term
Crietria- no more
than 1.25% time
-154.4 dBW
-149.6 dBW
-148.4 dBW
Long Term
Criteria- no more
tha 20% time
-156.1 dBW
-154.9 dBW
-149.4 dBW
Metaids Transmitter
Characteristics
• Metaids transmitters typically exhibit poor
characteristics for several reasons
– Expendable device - costly technology to stabilize the
transmitter is avoided
– Extreme operating conditions
• Temperature: +50 to –90 ºC
• Pressure: Surface to 36 km
• Transmitter standards of normal communications
systems should not be applied to radiosonde
transmitters
Metaids Receiver Characteristics
• Metaids users should strive for the best
receiver system design possible
– Receivers are a long term investment where
advanced technology is more applicable
– Good receiver design helps reduce the potential
for interference problems
– Good receiver design also increases link
reliability and increases data availability
Metaids Receiver Characteristics
(cont)
• Some receiver characteristics necessary to
operate with poor radiosonde transmitters
result in greater interference susceptibility
– Large receive bandwidth to receive signals that
jump quickly in frequency
– Automatic tracking loops that track strongest
signal in band
Metaids Equipment –
Additional Information
• Handbook on Use of Radio Spectrum for
Meteorology:
– Section 3.4.1- Ground based receiving equipment
– Section 3.4.2- Ground-based signal processing systems
– Section 3.4.3- Expendable sensing packages
(radiosondes)
– Section 3.6 – Discussion of national selection of
metaids technology
The Band 400.15-406 MHz
The Band 1668.4 - 1700 MHz
Operations in 1668.4-1700 MHz
• In general, metaids systems operated in this
band use radio direction finding for wind
measurement
– Winds calculated from balloon movement
– Movement determined by change in signal
azimuth and elevation, and balloon height
• GPS radiosondes have also been developed
for operation in this band
Sharing Issues in 1668.4-1700
MHz with the Metsat Service
• The band 1670-1700 MHz is currently shared with
the Metsat service
• Radiosondes cause interference to Metsat earth
stations if they are operated in close proximity
• The WMO SG-RFC recommends the band be
segmented to prevent interference
– Metsat operations: 1670-1675 MHz and 1683-1700
MHz
– Metaids operations: 1675-1683 MHz
Interference to Metsat Service
MetSat
MetSat Data
Link (GVAR
or S-VISSR)
Radiosonde
Link
Radiosonde
Receiver
Interference
MetSat
Earth Station
Sharing Issues in 1668.4-1700
MHz with the Radio Astronomy
• The Radio Astronomy service has an
allocation below 1670 MHz.
• Metaids users should ensure transmitters do
not operate below or drift in frequency to
below 1668.4 MHz
– Keep in mind the WMO recommends Metaids
operations should be conducted within 16751683 MHz.
Interference to Radioastronomy
Signals from Stars
Radiosonde
Link
Radiosonde
Receiver
Interference
Radio
Astronomy
Station
Mobile-Satellite Service
Proposals for 1670-1700 MHz
• WARC-92 allocated the band 1675-1710 MHz to
the MSS in ITU Region 2 (N. and S. America)
• Proposals were made to WRC-95, WRC-97, and
WRC-2000 to extend the allocation, in at least part
of the band, to worldwide
• Past WRCs made no additional allocations
• WRC-03 Agenda Item 1.31 calls for considering
proposals for an MSS allocation in 1683-1690
MHz or some other band (if identified)
Sharing Issues with MSSPre WRC-2000 Studies
• The ITU-R concluded that metaids and
MSS can not share spectrum on a cofrequency, co-location basis
– Metaids typically operate in 1675-1683 MHz
making that band infeasible for MSS use
– Metsat operations exist in 1670-1675 and 16831700 MHz - metaids can not be moved
MSS and MetAids
Incompatibility
Interference
MSS Service
Links
Radiosonde
Radiosonde
Link
Interference
Radiosonde
Receiver
Sharing Issues with MSSPre WRC-2000 Studies (cont)
• The conclusion that MSS cannot share with
metaids in 1675-1683 MHz combined with
the conclusion that sharing is not possible in
1690-1700 MHz due to metsat,
concentrated post-WRC-2000 efforts on the
band 1683-1690 MHz and an alternative
band of 1670-1675 MHz
Preparations for WRC-03
Agenda Item 1.31 (Res 227)
• WRC-03 agenda item 1.31 calls for
additional studies in accordance with
Resolution 227
• Resolution 227 contains a large volume of
information, but the are two key points
– Conduct studies for the band 1683-1690 MHz
– If necessary, conduct studies on alternative
bands (bands not specified)
Studies: 1683-1690 MHz
• WMO recommends metaids operate in 1675-1683
MHz to avoid interference to metsat stations
• The ITU has concluded, with WMO concurrence,
that an MSS allocation at 1683-1690 MHz will
have little impact on worldwide metaids
operations.
• The sharing issue in 1683-1690 MHz centers on
the significant sharing problems with the metsat
service. (Covered in Workshop Session B - 3.1)
Studies: 1670-1675 MHz
• Resolution 227, referenced in WRC-03
Agenda Item 1.31 requests the ITU-R study
alternative bands if the band 1683-1690
proves to be infeasible
• In response, the ITU-R has conducted
studies on the band 1670-1675 MHz, even
though the MSS has not fully agreed
1683-1690 MHz is not feasible
Studies: 1670-1675 MHz
• ITU-R studies conclude that MSS
operations in 1670-1675 MHz will have
little impact on worldwide metaids
operations
– Several countries will continue to require 16701675 MHz into the future
– MSS operations in those countries will not be
feasible
ITU-R Recommendation
SA.1264
• Recommendation SA.1264 addresses sharing
between the MSS and metaids in 1670-1700 MHz
– Sharing not feasible in 1675-1683 MHz – primary subband for radiosonde operations
– MSS operations in 1670-1675 MHz will have little
impact on metaids operations except for several
countries
– Radiosondes can not moved elsewhere in 1683-1700
MHz due to incompatibility with metsat downlinks
CPM Report Text on Agenda
Item 1.31
• Section 2.8.2 addresses sharing between
MSS and metaids
• CPM Report Text is consistent with
conclusions stated in Recommendation
SA.1264.
• CPM Text will be reviewed and possibly
edited one last time at the CPM Meeting,
November 18-29
Summary of Band 1670-1700
MHz
Metaids
Metsat
1670-1675
MHz
Band used in several countries.
MSS operations will have minimal
impact on worldwide metaids
operations.
Band used only for main metsat earth
stations. MSS operations possible if
main metsat earth stations are
protected.
1675-1683
MHz
1683-1690
MHz
1690-1700
MHz
Primary sub-band for metaids
operations (WMO recommended).
MSS operations not feasible due to
interference to metaids.
Not used for metsat operations due to
incompatibility with metaids
operations.
Generally not used for metaids
operations due to incompatibility
with metsat operations.
Used for metsat operations in ITU
Regions 2 and 3. MSS use not
feasible due to incompatibility with
metsat operations.
Not used for metaids operations.
metaids operations incompatible
with metsat operations.
Used for metsat operations. MSS not
feasible due to incompatibility with
metsat operations.
Recommended Strategy for
Agenda Item 1.31
• From the metaids perspective, the CPM text
is well balanced, so it should not be
modified at the CPM
– Text is not perfect, but also is not damaging to
metaids operations
– Opening text to modifications could lead to
introduction of unacceptable text from the MSS
• Recommend to your CPM delegation “no
change” to CPM text relating to Res 227.
Recommended Strategy for
Agenda Item 1.31 (cont)
• An allocation to the MSS in 1683-1690
MHz should be opposed, it will have a
significant impact on meteorological
operations
– ITU Regions 2 and 3: Protection of metsat
earth stations not feasible
– ITU-Region 1: Limits availability of spectrum
for future metsat growth
Recommended Strategy for
Agenda Item 1.31 (cont)
• An allocation to the MSS in 1670-1675
MHz should not be opposed
– Not the optimum solution since some metaids
stations in several countries could be impacted
– Since there is great pressure to provide the
MSS some spectrum, the band 1670-1675 MHz
offers a solution that the worldwide
meteorological community can live with
Recommended Strategy for
Agenda Item 1.31 (cont)
• Discussions of the sub-bands 1675-1683 or
1690-1700 MHz should be opposed Resolution 227 considers work on them
completed and MSS use infeasible
– The sub-band 1675-1683 is the only available
spectrum in this area of spectrum that can be
used to meet metaids operations requirements
Recommended Strategy for
Agenda Item 1.31 (cont)
• Resolution 227 should be suppressed or
modified to remove any part of 1675-1700
MHz from future consideration
– All studies have been completed - if WRC-03
cannot make a decision, no new work can occur
to help a future WRC make a decision
– Unresolved questions on protecting
meteorological services in 1670-1675 MHz
could be addressed in a resolution if necessary