WRC –03 Agenda Item 1.24
To review the usage of the band 13.75-14 GHz, in accordance with Resolution 733
(WRC-2000), with a view to addressing sharing conditions.
Issues
Resolution 733 resolves: "to invite ITU-R
1.
to conduct studies, as a matter of urgency and in time for consideration by WRC-03,
on the sharing conditions indicated in Nos. S5.502 and S5.503, with a view to
reviewing the constraints in No. S5.502 regarding the minimum antenna diameter of
GSO FSS earth stations and the constraints on the e.i.r.p. of the radiolocation
service;
2.
to identify and study, in time for consideration by WRC-03, possible alternative
sharing conditions to those indicated in Nos. S5.502 and S5.503."
Background
The band 13.75-14 GHz is allocated on a co-primary basis to FSS (fixed satellite service) and
RLS (radiolocation service). It is also allocated, in some countries, to FS (fixed service) and
MS (mobile service)(Nos. S5.499 and S5.500) and to RNS (radionavigation service) (No.
S5.501). GSO systems in the SRS (space research service) use this band in accordance with
No. S5.503. Additionally, non-GSO SRS and EESS (Earth exploration satellite service)
operate with protection from the FSS (No. S5.503A) until 1 January 2000. After 2001 the only
space research system that will remain in the band on a co-primary basis with the FSS is the
DRS system. For the sharing between FSS, RLS, RNS and SRS, the 13.75-14 GHz band can
be split as follows:

13.75-13.8 GHz: FSS uplinks, RNS, radiolocation emissions and GSO-DRS links to
both earth stations and LEO spacecraft (e.g. Shuttle);

13.8-14 GHz: FSS uplinks, RNS, radiolocation emissions.
During the 1997-2000 ITU-R study period, some studies have addressed the sharing
conditions between GSO FSS services and radiolocation in the band 13.75-14 GHz and
between GSO FSS services and space research in the band 13.772-13.778 GHz. These
studies related to the possible relaxation of the minimum antenna diameter of 4.5 m contained
in footnote S5.502. WRC-2000 decided that the Agenda of WRC-2003 will include the review
of these limits and that this issue be studied by the ITU-R.
Joint Task group 4-7-8 is responsible for Agenda Item 1.24.
The first meeting of JTG 4-7-8 took place in Geneva from 16 to 18 October 2000. This
meeting allowed to define the input parameters needed for the review of the sharing
environment in the band 13.75-14 GHz. Some were already available and for those missing
two circular letters have been drafted to be sent to Administrations and Sector Members
(CA/89 for the characteristics of radiolocation and radionavigation systems and CA/90 for
those of GSO FSS earth stations). The meeting also identified the calculation approaches that
have been used in the past or could be used in making assessments of the impact of
modifying some of the current sharing conditions on the interference received by each service
involved.
At its second meeting (Geneva, 28 May – 1 June 2001), JTG 4-7-8 completed the
identification of the system parameters and further developed the calculation approaches by
defining simulation models. The group also agreed that there was a need to develop the
parameters of Table 7 of Appendix S7 for the protection of radiolocation and radionavigation
in the 13.75-14 GHz band.
JTG 4-7-8 received a request from NASA for a contiguous 10 MHz protection (13.770 to
13.780 GHz) from FSS, rather than the current 6 MHz identified in No. S5.503 (13.772-13.778
GHz) to fully achieve the objective of the International Space Station's mission. The group
identified further studies that need to be carried out to consider this requirement at the next
meeting (February 2002).
JTG 4-7-8 noted that the band 13.75-14 GHz was also allocated on a secondary basis to nongeostationary systems in the Earth exploration-satellite service (see footnote S5.503A) and
agreed to consider the impact of any modification to the current sharing conditions on this
secondary service.
During the CEPT preparation for the third JTG 4-7-8 meeting, a contribution (UK) addressing
the protection of radar receivers from interference caused by FSS earth stations has been
approved by the SE16 project team (Paris, 21-22 January 2002). This contribution shows that
consideration should be given to replacing the limitation on the minimum diameter of 4.5m for
FSS earth stations using the band 13.75-14 GHz by constraints on the location of the earth
stations and on the aggregate pfd from all the earth stations in a country, possibly
supplemented by limiting the off-axis EIRP densities of FSS earth stations. Other
contributions made directly to the JTG 4-7-8 from CEPT members proposed the removal of
the antenna size constraint on earth stations and only if necessary the introduction of an offaxis EIRP density constraint.
At its third meeting (Geneva, 4-7 February 2002), JTG 4-7-8 reached the following
conclusions:
1. Coordination of transmit FSS earth stations with radiolocation stations
Application of S9.17 would be possible only in respect of radiolocation stations located at
fixed, pre-determined, geographical points, which excludes both maritime and
aeronautical radiolocation stations. Other regulatory measures would be needed for these
latter stations. System parameters to be included in Table 7 of Appendix S7 in order to
protect ground based radiolocation stations at fixed geographical locations have been
suggested to WP 1A and will be considered in the framework of updating Appendix S7.
2. Sharing between FSS and radiolocation service
It was agreed that other ways of protecting the radiolocation service would be needed if
the dish size constraint of S5.502 was to be relaxed or removed. Possibilities in this
regard, which might be employed individually or in combination, were identified as: zones
where FSS earth stations would not normally be deployed, the imposition of pfd limits, or
the imposition of off-axis e.i.r.p. density limits more stringent than those of
Recommendations ITU-R S.524 and S.728. It was also recognized that technical
characteristics of airborne radiolocation stations create a unique sharing situation which
limits the available mitigation techniques.
The required protection criterion for radiolocation service was expressed as: "An
aggregate interference level of -133 dBW in a bandwidth of 10 MHz, at the receive output
flange of a radar antenna located at 36m above sea level at any point Y km distant from
the shore, not to be exceeded for more than X % of the time".
3. Sharing between FSS and SRS
It was agreed that an e.i.r.p. density mask was the appropriate solution to protect the
SRS from interference caused by the FSS. A mask for FSS earth stations of 4.5 meter or
larger was agreed as:
63.2 + 20 log (antenna diameter / 4.5) dBW/MHz
with a maximum e.i.r.p. of 80.2 dBW/MHz (the reference bandwidth still to be agreed).
JTG 4-7-8 decided to continue the work on the e.i.r.p. density mask for antenna
diameters below 4.5 metre in a joint correspondence group.
Significant Recent Developments
At the February 02 JTG 4-7-8 meeting, the required protection criterion for radiolocation
service was expressed as: "An aggregate interference level of -133 dBW in a bandwidth of
10 MHz, at the receive output flange of a radar antenna located at 36m above sea level at
any point Y km distant from the shore, not to be exceeded for more than X % of the time".The
combined solution was not reached within JTG4-7-8 especially the values for X and Y.
At the May 2002 meeting, the JTG4-7-8 produced CPM text and proposed a sharing criterion
to satisfy the above radiolocation protection level from FSS earth stations with a diameter less
than 4.5m as a single entry interfering PFD level of;

For maritime radar, - [X dBW/m²/10MHz not to be exceeded for more than Y% of the
time] produced at 36 m above sea level at the baseline (low water mark) as defined in UN
Convention on Law Of the Sea 1982.

For land mobile radar, - [X dBW/m²/10MHz not to be exceeded for more than Y% of the
time] produced 3 m above ground at the border.
The meeting did not agree on the values of X and Y and decided to form a joint
correspondence group to carry on the work.
In the CPM text two methods were proposed as follows to satisfy this agenda item;
a) Method A – No change to the current regulations and associated sharing criteria in
Nos. 5.502 and 5.503
Advantages


The delicate balance between the services in the band 13.75-14 GHz, as established by
WARC-92 modified by WRC-95 and WRC-2000, in Nos. 5.502 and 5.503, would be
maintained. Since these footnotes indirectly limit the number of FSS earth stations
deployed in the band, the protection they provide to Radiolocation and Space Research
would be adequate.
No additional regulatory burden is placed upon Administrations.
Disadvantages


No protection is afforded to Radiolocation other than limiting the number of interference
sources.
FSS development would continue to be unduly constrained by the minimum size of 4.5 m
in diameter in this band.
b) Method B – Relaxation of the current limit on the FSS antenna size, with additional
regulatory provisions and increase in the protected bandwidth of SRS
In order to maintain the delicate balance between the services involved, this method is based
on reducing the current limit on the minimum antenna size to 1.2 m and by adding technical
conditions which would adequately manage the interference caused by FSS earth stations
into Radiolocation and SRS stations:

Off-axis eirp density limits to manage the interference into airborne radars, based on a 4
dB tightening of Recommendation ITU-R S.728, and specified in the Radio Regulations
on a mandatory basis.
A single entry pfd limit (specified in the RR on a mandatory basis but not subject to
compliance verification by the BR):
 For maritime radar, - [X dBW/m²/10MHz not to be exceeded for more than Y% of the
time] produced at 36 m above sea level at the baseline (low water mark as defined in UN
Convention on Law Of the Sea 1982).
 For land mobile radar, - [X dBW/m²/10MHz not to be exceeded for more than Y% of the
time] produced 3 m above ground at the border.



Table 7 of Appendix 7 of the RR, would be updated in order to determine the need for
coordination of an FSS earth station with radiolocation stations at specified fixed points,
as part of the procedure of No. 9.17.
To maintain the current protection of SRS operations, the on-axis eirp limit in the 6 MHz
bandwidth contained in No. 5.503 would be made a function of the FSS antenna
diameter, f(D) where D is the FSS earth station antenna diameter. In addition the
protected bandwidth would be extended to 10 MHz centred on 13.775 GHz .
6 dB Relaxation of the limit on the e.i.r.p. level averaged over 1s on radiolocation
emission at elevation angles below 2°
Advantages




FSS development would no longer be constrained to use only earth station antennas
larger than 4.5 m. This would grant relaxation of the current limit to 1.2 m with the addition
of appropriate limits to ensure the protection of the other services, thus leaving greater
flexibility.
A quantified protection from each individual FSS earth station is afforded to Radiolocation
systems.
Relaxation of the constraints on the radiolocation emission
SRS is assured a managed interference environment in the protected bandwidth.
Disadvantages



Administrations wishing to deploy FSS earth stations will have to ensure that the pfd limits
are met, which is likely to include some territorial constraints;
Regulatory implementation of these limits may be difficult;
SRS will have to accept a higher interference level as a result of the relaxed sharing
criterion used to derive the e.i.r.p. mask.
On the FSS/SRS issue the meeting agreed that on axis e.i.r.p density mask is the correct way
to protect the the SRS and finalised the mask for FSS earth stations  4.5m as;
49.2 + 20 log (antenna diameter / 4.5) dBW/40kHz with a maximum e.i.r.p. of 66.2
dBW/40kHz
For antenna diameters below 4.5 metres no compromise was reached between FSS/SRS
and the JTG 4-7-8 joint correspondence group decided to continue the work on the e.i.r.p.
density mask.
Preliminary UK View

The UK recognises that the current constraint on the FSS to employ earth station
antennas no smaller than 4.5m in diameter limits the number of sources of interference to
radar receivers, but also recognises that it restricts the FSS use of the band.

The UK believes that in order for the adequate protection for shipborne and land-based
radar receivers alternative constraints on the FSS would be required if the 4.5m minimum
earth station diameter was removed. Therefore, the UK will support Method B in the Draft
CPM Report provided that acceptable values of X and Y can be agreed within ITU-R.
The UK is proposing the following values for X and Y for discussions;
-111.5 dBW/m2/10 MHz for more than 0.5% of the time at 36m above sea level [at the
baseline as defined in United Nations Convention on the Law of the Sea,
1982].
-111.5 dBW/m2/10 MHz for more than 0.5% of the time at 3 m above ground at the
border.

Regarding the sharing between FSS and SRS the UK agrees with JTG4-7-8 that an onaxis e.i.r.p. density mask to be applied to FSS earth station emissions in the sub-band
concerned (13.770-13.780GHz) is an appropriate way to protect the SRS uplink. As the
actual mask for earth stations with antennas of diameter less than 4.5m is not yet agreed
within ITU-R, the UK will propose and support the following mask;
4.7D + 42.0 dBW/MHz for 1.2  D < 4.5, and 63.2 + 20Log(D/4.5) dBW/MHz for 4.5
 D < 31.9, where D is the fixed-satellite service earth station antenna diameter (m)
from 13.770 to 13.780 GHz;
If necessary to achieve a consensus the alternative of expressing of the mask in a 1 Hz
reference bandwidth would be acceptable to the UK, in which case the two expressions
would be 4.7D – 18.0 dBW/Hz and 3.2 + 20Log(D/4.5) dBW/Hz respectively.

The UK would only support the above masks if the current minimum FSS earth station
antenna diameter (4.5m) restriction is relaxed as described in Method B of the Draft CPM
report.