**Document IWG-4/007**

#### April 11, 2001

***WRC-2003 Advisory Committee***

##### Informal Working Group-4

**IWG-4 preliminary Views**

**on WRC-03 Agenda Item 1.32**

**WRC-2003 Agenda Item 1.32b:** to consider technical and regulatory
provisions concerning the band 37.5 - 43.5 GHz, in accordance with
Resolutions **128 (Rev. WRC-2000)** and **84 (WRC-2000)**.

**ISSUES:** 1. How to achieve the successful co-existence of the fixed
service ("FS") (including high-density applications in the FS), the
fixed-satellite service ("FSS") (including high-density applications in
the FSS), the mobile-satellite service ("MSS") and the
broadcasting-satellite service ("BSS") within the 37.5 - 42.5 GHz
frequency range.

2\. How to ensure that FSS satellites that operate in clear sky
conditions in the 37.5 -- 40.0 GHz and 42.0 - 42.5 GHz bands at reduced
power flux-density ("PFD") levels use downlink fade compensation to
overcome fading conditions in the least intrusive way practicable.

3\. How to ensure that ubiquitously-deployed FSS terminals in the 40.0
-- 42.0 GHz band will be protected from interference caused by
co-frequency FS transmitters.

**BACKGROUND:** Various segments of the 37.5 - 43.5 GHz band are
allocated to the FS, FSS, BSS and MSS on a co-primary basis. Segments of
this band are being used or planned for high-density applications in the
FS ("HDFS"), and other segments of the band are planned for deployment
of high-density applications in the FSS ("HDFSS"). Co-frequency sharing
is not feasible between HDFS and HDFSS systems, but sharing situations
where only one of the services operates with ubiquitously-deployed small
terminals may be practicable.

Significant actions were taken at WRC-2000 with respect to the 37.5 --
43.5 GHz band:

1.  A framework for a comprehensive sharing arrangement for terrestrial
    and satellite services in the 37.5 - 43.5 GHz band was established,
    based on each service using some portions of the band more
    intensively than others.

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(a) The 40.5 - 42.5 GHz band allocation for FSS was harmonized across
    all three ITU Regions.

(b) The 37.5 - 40.0 GHz and the 40.5 - 43.5 GHz bands, among others,
    were identified for HDFS applications in footnote **S5.547**, noting
    the potential deployment of HDFSS applications in the bands 39.5 -
    40.0 GHz and 40.5 - 42.0 GHz and the constraints such deployments
    may impose on use by HDFS.

(c) PFD limits were established in Article **S21** (Table **S21-4**) for
    the FSS (space-to-Earth) in the bands 37.5 - 40.0 GHz and 42.0 -
    42.5 GHz, and for the MSS (space-to-Earth) in the band 39.5 - 40.0
    GHz, which are favorable to high-density applications in the FS, but
    which also permit "gateway"-type FSS operations. The PFD limits in
    the bands 40.0 - 40.5 GHz and 40.5 -- 42.0 GHz are favorable for
    high density applications in the FSS.

(d) In the bands 37.5 -- 40.0 GHz and 42.0 - 42.5 GHz, footnote
    **S5.551AA** provides that non-GSO FSS systems should employ power
    control or other methods of downlink fade compensation, on the order
    of 10 dB, to reduce the level of interference to the FS while
    ensuring that the satellite systems are at power levels required to
    meet the desired link performance.

(e) With regard to the consideration of regulatory provisions for the
    band 40.0 - 40.5 GHz, Administrations were urged to take into
    account that WRC-2000 received a number of proposals to identify the
    band 40.0 - 40.5 GHz for high-density applications in the FSS.

(f) ITU-R is to study criteria and techniques to address interference
    from transmitters of FS into earth station receivers in high-density
    applications in the FSS in the bands 39.5 -- 40.0 GHz and 40.5 --
    42.0 GHz intended to operate in the same geographic area.

(g) WRC-2000 established provisional PFD limits on BSS satellites in the
    band 40.5 - 42.5 GHz and requested the ITU-R to study technical and
    operational characteristics of BSS and to review the provisional PFD
    limits.

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2.  HDFS deployments in the 37.0 - 40.0 GHz band in ITU Region 2 were
    provisionally afforded greater protection from interference from FSS
    systems than they are in ITU Regions 1 and 3. In Region 2, prior to
    WRC-03, before an Administration brings into use a frequency
    assignment for a GSO FSS network in the 37.5 -- 40.0 GHz band, it
    shall seek the agreement of any Administration in Region 2 on whose
    territory the PFD produced exceeds the values in Table **S21-4**
    minus 12 dB.

3.  ITU-R is to conduct studies to determine whether the PFDs in Article
    **S21** in the bands 37.5 -- 40.0 GHz and 42.0 -- 42.5 GHz will
    adequately protect the FS from FSS and MSS transmissions (39.5 --
    40.0 GHz only), taking into account the need to ensure a proper
    balance in terms of the impact on both the FS and space services
    sharing the same band.

4.  ITU-R is to conduct studies to determine whether the PFDs in Article
    **S21** in the band 40.5 -- 42.0 GHz band will adequately protect
    systems in the FS, taking into account the requirements of the FSS
    and recognizing that some Administrations plan to deploy FSS systems
    using ubiquitous very small aperture terminals in the 39.5 -- 42.0
    GHz band.

5.  In the bands 37.5 -- 40.0 GHz and 42.0 -- 42.5 GHz, ITU-R is to
    study the nominal clear sky PFD levels, and the percentage of time
    during which they may be exceeded to overcome fading conditions for
    FSS, in order to protect the FS while permitting operation of FSS
    using coordinated large antennas.

6.  ITU-R is to study the use of mitigation techniques to improve
    sharing conditions between the space services and FS systems, taking
    account of the impact on systems of all affected services.

**PRELIMINARY VIEWS:**

The U.S. continues to fully support the comprehensive sharing
arrangement that the CITEL countries took into WRC-2000. This approach
is equitable, and allows the competing needs of the FS and the FSS in
the 37.5 -- 43.5 GHz band to be satisfied.

The unique characteristics of some HDFS networks in the 37.5 -- 40.0 GHz
band, which include links across a very wide range of elevation angles,
makes them much more sensitive to satellite downlink interference than
more traditional FS networks or HDFS networks with smaller
concentrations of high elevation angle links. The PFD limits established
in Article **S21** (Table **S21-4**) for the FSS (space-to-Earth) in the
bands 37.5 - 40.0 GHz and 42.0 - 42.5 GHz, and for the MSS
(space-to-Earth) in the band 39.5 - 40.0 GHz should be maintained, and
should be used for validation purposes. When GSO and non-GSO satellites
operate in these bands under clear-sky conditions, their operational PFD
levels should be reduced to the levels in Table **S21-4** minus 12 dB.

The U.S. supports a policy that allows FSS satellites operating at the
nominal clear-sky levels (Table **S21-4** minus 12 dB) under clear-sky
conditions in the bands 37.5 -- 40.0 GHz and 42.0 - 42.5 GHz to increase
PFD by up to 12 dB to compensate for fading conditions between the
satellite and one or more geographically separated Earth stations. The
U.S. is currently participating in ITU-R studies that will determine the
appropriate percentage(s) of time during which satellite networks and
systems will need to use downlink fade compensation, and any associated
conditions that are appropriate to minimize the impact of such use on
affected HDFS links.

The PFD limits in the bands 37.5 - 40.0 GHz and 42.0 - 42.5 GHz should
still be adequate to permit "gateway"-type FSS operations. FS operations
in the 40.0 - 42.0 GHz band should be able to be accommodated subject to
constraints that would be imposed due to deployment of high-density
applications in the FSS.

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