Final Report of FCC Working Group: Lose LightSquared from L-Band

Final Report of FCC Working Group: Lose LightSquared from L-Band
http://www.gpsworld.com/gnss-system/...d-l-band-11848
July 6, 2011

“Based on the analysis performed, LightSquared should not be permitted
to use the L-Band spectrum for a densely-deployed, non-integrated
terrestrial-only network. Such a network would cause unacceptable
interference to GPS operations, wiping out an installed base of over 500
million units used in a wide array of public safety, aviation,
industrial and consumer applications. While mitigation techniques
utilizing filters were discussed in theory, they could not be tested as
part of the WG effort because filters do not exist, even in prototypes.
No information considered by the WG demonstrated that any mitigation
techniques — other than relocation of the proposed terrestrial network
to an alternative band — would be successful.” (From the U.S. GPS
Industry Council's overview of the WG report)

The final report to the Federal Communications Commission (FCC) on three
months of research by the technical working group (TWG) tasked to
investigate and analyze effects of powerful terrestrial L-band
transmitters on the GPS signal and services finally appeared on June 30,
nearly two weeks after its assigned date. LightSquared had requested an
extension, and apparently the lawyers on its staff used the extra time
to write many pages of self-justification and further argumentation of
the company’s case. But the facts are clear: the LightSquared signal
would devastate services for users of all GPS receivers tested.

The final report is not easy to find on the FCC's labyrinthine website.
Read the full "final report of the Working Group (WG) that was formed to
study the GPS overload/desensitization issue as described by the Federal
Communications Commission (FCC) in DA 11-133" here.

See also four appendices:
one, "Appendix A.1: MOPS Based Procedure for Minimum Recommended Testing
of LightSquared RFI to GPS Aviation Receivers"
two, "Appendix G.2: from Alcatel-Lucent Labs, LightSquared L-Band GPS
Receiver Equipment Impact Evaluation Testing"
three, "Appendix H.1.1: JPL/NASA Report on Laboratory Testing of
Receivers for the Space-Based Sub-Team and the High Precision Sub-Team"
and four, "Appendix H.1.10: High Precision Receivers - NAVAIR Anechoic
Chamber Test Results."

Full data for all device tests conducted by the Working Group is
available for download at: ftp://twg:(E-Mail Removed)

GPS World readers may also be interested in the thoughtful and
intelligible analyses provided by the U.S. GPS Industry Council
("Overview of the Final Report of the Working Group") and the Coalition
to Save Our GPS ("FCC-Mandated Working Group Report Documents Pervasive
Harmful Interference with GPS").

The TWG conclusions of widespread disruption and harm to GPS services
are consistent with those reached by third parties that have reported
independent analyses: RTCA, Inc., a Federal Advisory Committee that
evaluates aviation, and the National Public Safety Telecommunications
Council (NPSTC).

“The TWG faced an extraordinary challenge of trying to determine if the
laws of physics would allow the high-power LightSquared signals to
co-exist in adjacent radio spectrum with the low-power satellite signals
of GPS over and above the complex regulatory challenges of managing
spectrum sharing,” said Charles Trimble, chairman of the U.S. GPS
Industry Council. “In the end, the laws of physics won out.”

Trimble, who co-chaired the TWG, added, “There is no single, simple
solution that can eliminate interference for all classes of GPS
receivers in the near term. GPS touches every aspect of our lives. It
goes beyond the most widely known navigation applications such as car
navigation and cell phones to hugely important applications such as
agriculture, electric power grids, communications networks,
infrastructure monitoring and construction.”

Regarding possible effective solutions, he offered the view that
“greater separation of the LightSquared signals and those of GPS are
necessary if the value of GPS is to be protected and broadband
communications can grow to its potential over the long term.”

In the area of high-precision receivers used for precision agriculture,
survey, construction, machine control, mining, geographic information
systems (GIS), structural deformation monitoring, and science, the group
found that damaging interference existed at times at very long distances
for the LightSquared transmitters. NovAtel president and CEO Michael
Ritter said, “Allowing LightSquared to interfere with the utilization of
these high precision receivers would eliminate the productivity
improvements provided to these industries and applications during the
past 20 years and will result in significantly higher prices for goods
and services from these industries to the consumer."

Key Results and Findings from the WG Report:

1. The LightSquared Terrestrial Broadband Service Will Cause Harmful
Interference to Nearly All GPS Receivers and GPS-Dependent Applications

2. Limited Testing of LightSquared Terrestrial Broadband Operations in
the “Lower” 4G LTE Channel Does Not Eliminate Harmful Interference to
GPS Receivers and GPS-Dependent Applications.

3. Increasing Filtering on GPS Receivers Is Not an Available Mitigation
Technique.
No Suitable Filters Exist;
Even if Filters Were Available, They Have Undesirable Performance
Impacts on GPS Receivers That Have Not Been Evaluated.
Increased Filtering Does Not Mitigate Interference to Hundreds of
Millions of GPS Users in the Installed Base.

4. The Only Feasible Solution to the Harmful Interference Effects
LightSquared’s Proposed 4G LTE Terrestrial Broadband Service Will Cause
to GPS Receivers and GPS-Dependent Applications Is to Relocate the
LightSquared Service to Spectrum that is Not Adjacent to GPS/RNSS,
outside of the L-Band.