**Document IWG-2/009**

**Author: D. Weinreich**

**17 April 2001**

**WRC-2003 ADVISORY COMMITTEE**

**DRAFT PRELIMINARY VIEWS ON WRC-03**

**WRC-2003 Agenda Item: 1.4** - to consider the results of studies
related to Resolution **114 (WRC-95)**, dealing with the use of the band
5091-5150 MHz by the fixed satellite service (Earth-to-space) (limited
to non-GSO MSS feeder links), and review the allocation to the
aeronautical radio- navigation service and the fixed satellite service
in the band 5091-5150 MHz;

**ISSUES:** WRC-2003 will review the results of studies on the technical
and operational issues related to sharing of the band 5 091-5 150 MHz
between the aeronautical radionavigation service and the fixed-satellite
service providing feeder links of the non-geostationary mobile-satellite
service (Earth-to-space). Of primary concern is whether or not revisions
are required to the current regulatory provisions (footnotes **S5.444**
and **S5.444A** and Resolution **114 (WRC-95)** and if so, what
revisions? In addition, consideration must be given to the following:
Are there requirements for MLS to use spectrum above 5 091 MHz, if yes,
in what time frame? To what extent have MSS feeder links used spectrum
to-date in the range 5 091-5 150 MHz? Would the MSS feeder links coexist
with ARNS on a secondary basis or is there transition of feeder link use
expected to frequencies above 5 150 MHz? What is the experience with
coordination between the Fixed Satellite Service and microwave landing
system stations and the subsequent operation of FSS stations in the
5091-5150 MHz band?

**BACKGROUND**: As a result of WRC-95, the Fixed Satellite Service (FSS)
was granted co-primary status along with the Aeronautical
Radionavigation Service in the band 5150 -- 5250 MHz for the use of
feeder uplinks for Non-Geostationary Mobile Satellite Service systems
(**RR S5.447A**). In addition, the band 5091-5150 MHz was allocated, on
a co-primary basis, to the FSS for NGSO MSS feeder uplinks under
**S5.444A** and Resolution 114 (WRC-95). Resolution **114 (WRC-95)**
requested ITU-R to study issues concerning sharing between Aeronautical
Radionavigation Service (ARNS) and feeder links to Mobile Satellite
Service (MSS) (Earth-to-space) in the band 5 091-5 150 MHz and to report
results of the studies to WRC-2003. The use of this band by Microwave
Landing Systems (MLS) and MSS feeder links is subject to footnotes
**S5.444** and **S5.444A,** in particular the following conditions
apply:

1)  prior to 1 January 2010, the use of the band 5 091-5 150 MHz by
    feeder links of non-geostationary-satellite systems in the
    mobile-satellite service shall be made in accordance with
    **Resolution 114 (WRC-95)**;

2)  prior to 1 January 2010, the requirements of existing and planned
    international standard systems for the ARNS which cannot be met in
    the 5 000-5 091 MHz band, shall take precedence over other uses of
    this band;

3)  after 1 January 2008, no new assignments shall be made to stations
    providing feeder links of non-geostationary mobile-satellite
    systems;

4)  after 1 January 2010, the fixed-satellite service will become
    secondary to the ARNS.

In fulfillment of this allocation, three NGSO MSS systems announced
plans to operate feeder uplinks in this band. Of the three systems
planning use of this band, two systems have implemented spacecraft
Tracking and Control operations and one system has begun commercial
service using the 5091-5250 MHz band for transmitting communications
traffic from Gateway earth stations to the NGSO spacecraft.

Sharing studies between NGSO/MSS feeder links and microwave landing
systems resulted in ITU-R Recommendation S.1342 \"Method for determining
coordination distances, in the 5 GHz band, between the international
standard microwave landing system in the aeronautical radionavigation
service and non-geostationary mobile satellite service stations
providing feeder uplink services.\" These studies showed that
compatibility between MLS receivers and MSS feeder links
(Earth-to-space) could exist if sufficient geographical separation
exists between the two stations. As a result, Recommendation S.1342 was
adopted to trigger coordination between the two operators to determine
the acceptability of an MSS site, possibly with or without restrictions.

In the United States and several other countries, coordination of the
gateway station with MLS stations has been accomplished using the
methodology contained in Recommendation ITU-R S.1342.

Spacecraft Command and Control operations began in the 5091-5250 MHz
band with the launch of the first Globalstar (or LEO-D, in ITU-R
terminology) satellite on 14 February 1998. Six gateway stations in
Argentina, Australia, France, Korea, South Africa and the USA also
participated in these Command and Control operations. The ICO (or LEO-F
system in ITU terminology) uses the 5150-5250 MHz band to support launch
and service operations.

Revenue communications service for the LEO-D began on 6 January 2000. In
addition to the gateway earth stations mentioned for Tracking and
Control operations 13 other gateway stations have been added to the
network as of the current date.

It is expected that if the two MSS systems currently operating gateway
stations develop as planned that the number of gateway stations
implemented worldwide will be approximately 65.

As of writing this document, no interference has yet been encountered by
MLS stations. Based upon coordination using the methods contained in
Recommendation ITU-R S.1342 it is expected that this situation will
continue.

ITU-R Working Party 8B is the lead group responsible for developing CPM
text on WRC-03 Agenda Item 1.4. WP 8B is currently studying the use of
the 5091-5150 MHz band by the Aeronautical Radionavigation Service
(ARNS) and the Fixed Satellite Service (FSS) for NGSO Mobile Satellite
Service (MSS) feeder uplinks. These studies are expected to conclude no
later than May 2002.

**PRELIMINARY VIEW:** Based upon the application of the coordination
procedures in Recommendation ITU-R S.1342 and the operating experience
gained to date, existing microwave landing system (MLS) and NGSO MSS
feeder link stations are able to function without interference. Future
deployment of both MLS and NGSO MSS facilities should be possible
through coordination under ITU-R S.1342. Continued common use of the
5091-5150 MHz band by both MLS and NGSO MSS stations is dependent upon
the extent of future deployment of these systems and the characteristics
of new Aeronautical Radionavigation Service (ARNS) systems, if any.
Further studies are needed to investigate and evaluate the continuing
usage of the 5091-5150 MHz band by the ARNS and the FSS for NGSO MSS
feeder uplinks to determine if changes in the existing Radio Regulations
covering this band are necessary. (17 April 2001)