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| **U.S. RADIOCOMMUNICATION        |   |                               |
| SECTOR**                         |   |                               |
|                                  |   |                               |
| **FACT SHEET**                   |   |                               |
+----------------------------------+---+-------------------------------+
| **Study Group:** ITU-R Working   | * |                               |
| Party 8D                         | * |                               |
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| **Ref.:** Resolution 220         | * |                               |
| (WRC-97)                         | * |                               |
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| **Document Title:** Working      |   |                               |
| Document on Potential            |   |                               |
| Interference to Aeronautical     |   |                               |
| Radionavigation Service          |   |                               |
| Pseudolite Receivers from        |   |                               |
| Potential Mobile-Satellite       |   |                               |
| Service (Space-to-Earth) Links   |   |                               |
| in a Portion of the Band         |   |                               |
| 1559-1567 MHz                    |   |                               |
+----------------------------------+---+-------------------------------+
| **Authors/Org:**                 |   | **Phone/Fax:**                |
|                                  |   |                               |
| Stephen D. Baruch/Leventhal,     |   | 202-416-6782/202-293-7783     |
| Senter & Lerman                  |   |                               |
|                                  |   | 202-416-6760/202-293-7783     |
| Raul R. Rodriguez/Leventhal,     |   |                               |
| Senter & Lerman                  |   | 408-481-2096/408-481-7728     |
|                                  |   |                               |
| Ann Ciganer/U.S. GPS Industry    |   | 650-723-2853/650-725-5517     |
| Council                          |   |                               |
|                                  |   | 301-229-0204/301-320-2421     |
| Per Enge/Stanford University     |   |                               |
|                                  |   | **E-Mail:**                   |
| Stephen D. McNeil/Telecomm.      |   |                               |
| Strategies                       |   | Sbaruch@LSL-Law.com           |
|                                  |   |                               |
|                                  |   | Rrodriguez@LSL-Law.com        |
|                                  |   |                               |
|                                  |   | Ann_Ciganer@Trimble.com       |
|                                  |   |                               |
|                                  |   | Per@relgyro.standford.edu     |
|                                  |   |                               |
|                                  |   | Steve_McNeil@email.msn.com    |
+----------------------------------+---+-------------------------------+
| **Purpose/Objective:** To        |   |                               |
| progress the work reflected in   |   |                               |
| PDNR ITU-R M.\[RNSS.CHAR\] to a  |   |                               |
| Draft New Recommendation.        |   |                               |
+----------------------------------+---+-------------------------------+
| **Abstract:** This document      |   |                               |
| provides supporting material     |   |                               |
| concerning the feasibility of    |   |                               |
| the coexistence of aeronautical  |   |                               |
| radionavigation service          |   |                               |
| pseudolites and mobile-satellite |   |                               |
| service (space-to-Earth) links   |   |                               |
| in the band 1559-1567 MHz        |   |                               |
+----------------------------------+---+-------------------------------+
| **Fact Sheet Preparer:** Stephen |   |                               |
| D. Baruch                        |   |                               |
+----------------------------------+---+-------------------------------+

**United States of America**

**WORKING DOCUMENT ON POTENTIAL INTERFERENCE TO AERONAUTICAL
RADIONAVIGATION SERVICE PSEUDOLITE RECEIVERS FROM POTENTIAL
MOBILE-SATELLITE SERVICE (SPACE-TO-EARTH) LINKS IN A PORTION OF THE BAND
1559-1567 MHZ**

This document updates work that was done at the Eighth Meeting of
Working Party 8D on the subject of aeronautical radionavigation service
("ARNS") pseudolites. It addresses, in particular, the impact of
interference from an mobile-satellite service ("MSS") space-to-Earth
link on the operation and utility of ARNS pseudolites in the lower
portion of the 1559-1567 MHz band.

An MSS downlink in 1559-1563 MHz would sharply reduce the coverage area
of an individual ARNS pseudolite. The power flux densities of an MSS
system of the type described by Inmarsat in its contributions to the
Seventh Meeting of Working Party 8D are some 15 dB higher than the
Global Navigation Satellite Service ("GNSS") noise floor. If received
power is inversely proportional to distance squared, then the coverage
radius would be reduced by a factor of approximately 5 and the coverage
area would be reduced by a factor of 25. Needless to say, such a
reduction would have a dramatic negative effect on the economy and
utility of pseudolites.

This reduction in coverage radius and coverage area occurs because the
power transmitted from the pseudolite cannot be arbitrarily increased to
compensate for the increase in the interference background caused by the
proposed MSS space-to-earth link. GNSS receivers that are not tracking
the pseudolite signals are called non-participating and these can
tolerate wide variations in the amplitude of the pseudolite signal. In
contrast, GNSS receivers that are tracking the pseudolite signals are
called participating receivers. While these are also tolerant of wide
amplitude variations, they would be negatively affected by the increase
necessary to overcome the 15 dB increase in the noise floor. The effect
would occur when the participating receiver was near to the pseudolite.
The minimum operating range is set by performance degradation in the
pseudolite tracking when the high amplitude of the nearby transmitter
introduces non-linear effects in the front end of the participating
receiver.

In short, an MSS (space-to-Earth) presence in the lower portion of the
1559-1610 MHz ARNS/RNSS band would cause a sharp decrease in the maximum
operating range of ARNS pseudolite systems, and would have a
corresponding negative impact on the economy and operational utility of
such systems. Needless to say, such a constraint would also impact the
feasibility of such systems for mines and agriculture.