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The Final Report of the Technical Working Group mandated by the Federal Communications Commission and conducted jointly by LightSquared and the GPS community of manufacturers and users has been filed with the FCC. It shows that LightSquared's proposed network would cause devastating interference to all kinds of GPS receivers tested including those used in Aviation, Cellular phones, General Location and Navigation (including Automotive, Public Safety, Personal and Marine Navigation), High Precision and Networks (including Agriculture, Surveying, Construction and Monitoring of Dams, Structures, Earthquakes and Volcanoes), and GPS Timing. The results show that the network would also jam LightSquared's own satellite transmissions and those of others in the same Mobile Satellite Services (MSS) band, being used in many important land and marine based industrial and safety applications.
Summaries of The Technical Working Group Final Report into LightSquared Interference with GPS can be downloaded here:
 Executive Summary
Summary and Technical Explanations
The full report and appendices can be downloaded here:
OTHER 06/30/2011 LightSquared Subsidiary LLC
TWG Final Report - Part 1 - Report
OTHER 06/30/2011 LightSquared Subsidiary LLC
TWG Final Report - Part 2 - Appendices 1 of 4
OTHER 06/30/2011 LightSquared Subsidiary LLC
TWG Final Report - Part 3 - Appendices 2 of 4
OTHER 06/30/2011 LightSquared Subsidiary LLC
TWG Final Report - Part 4 - Appendices 3 of 4
OTHER 06/30/2011 LightSquared Subsidiary LLC
TWG Final Report - Part 5 - Appendices 4 of 4
In light of the devastating interference results observed in its proposed network design, LightSquared has subsequently proposed a modified plan that uses the same frequencies and same power levels as those tested in the study, except the deployment of channels within the band adjacent to GPS would be in a different order than originally proposed, deploying the lower 10MHz channel first, claiming that this would solve the problem for "99%" of GPS receivers. This "99%" number will not be found anywhere in the official Technical Working Group Final Report, due to the fact that the data and conclusions do not support it. These statements have been made by LightSquared outside of the official Technical Working Group Final Report, without any explanation or justification.
In fact, these official Technical Working Group documents show something quite different. The Aviation sub-group reported that operation in this lower 10MHz channel could not be conclusively proven to be compatible or safe for aviation GPS users without further study, due to the potential inability of GPS receivers to acquire satellites in flight in the presence of interference from this lower 10 MHz channel. The General Location and Navigation and High Precision/Networks sub-groups report that 20 of 29 and 31 of 33 receivers tested, respectively, still experienced harmful interference in the presence of signals in this lower 10MHz channel. Power levels measured in the 'live sky' tests in Las Vegas showed the interfering signal at a distance of 500 feet from the tower to be up to 800 billion (eight hundred billion) times more powerful than the distant GPS signals being received from space. Even a mile from a tower, power levels 400 million times those of the GPS signals were recorded. The Cellular sub-group report contains data showing that 6 of 39 devices tested failed the defined test at power levels that were observed in the Las Vegas 'live sky' tests within a mile of the tower. Together, these results suggest that over half of all GPS receivers tested still suffered harmful interference in the presence of these very high powered interference signals in the lower 10MHz channel in the band adjacent to GPS, in addition to 100% of the MSS band satellite communications receivers with integrated GPS that were tested.
The GPS community has offered major concessions to LightSquared to try to accommodate their ambitions in the neighboring band and has spent a lot of time and money in a good faith study of the interference and potential mitigation. LightSquared has already been given the ability to increase the noise within the GPS band by 20% due to the high powered cell sites 'bleeding' into the GPS spectrum, based on agreed out of band emissions limits. In addition, the threshold of interference adopted by many sub-groups would allow LightSquared to cause another 20% loss of GPS signal power to GPS users within range of its towers. LightSquared's response was to suggest a further 75% of loss in GPS signal power instead.
Given that the satellite component of LightSquared's network - providing communications to rural areas and public safety users outside of cellular coverage - operates in the band adjacent to GPS without interference, a number of sub-groups suggested that the new, high powered ground based component of the network would best be deployed in a completely different band away from GPS, while continuing satellite operations to rural and unserved areas in the adjacent MSS band, which is internationally allocated to space communications. LightSquared rejected the suggestion that this option should be studied.
The potential damage to the U.S economy from interference to commercial GPS - even in the lower 10MHz channel - is estimated to be in the order of many tens of billions of dollars each year. For more details, read the report here: http://saveourgps.trimble.com/pdf/Economic_Study_News_Release_June_22.pdf
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