Interference Report Leaked to Bloomberg Indicates High Interference Levels
An NTIA Report leaked to Bloomberg Press stated that LighSquared’s basestations continue to disrupt GPS receivers. The Bloomberg article specifically stated, “The results from testing conducted Oct. 31 to
Nov. 4 show that “millions of fielded GPS units are not compatible” with the planned nationwide wholesale service, according to the draft seen by Bloomberg News. “LightSquared signals caused harmful interference to majority of GPS receivers tested,” according to the draft prepared for a meeting next week of U.S. officials reviewing the LightSquared proposal. “No additional testing is required to confirm harmful
interference exists.”” The article went on to say that, “It [the Report] found that 69 of 92, or 75 percent, of receivers tested “experienced harmful interference” at the equivalent of 100 meters (109 yards) from a
LightSquared base station.” Without a copy of the report and access to the test data, Questiny cannot comment on the validity of the claims. However, our previous analysis shows that even the single carrier LightSquared spectrum plan would degrade the performance of GPS receivers that did not have sufficient attenuation at the LightSquared’s frequencies (1526-1536 MHz). It appears that the NTIA’s direct testing has confirmed this situation — but this is not new news.
LightSquared stated at the conclusion of the FCC testing in June of 2011 that additional filtering would be needed, and contracted with the Javed corporation to construct external filters for such GPS units. There has never been any dougt in our minds that such filters could be developed, and that they would provide sufficient filtering of the LightSquared signal to permit operation of the GPS units. The issue has always been the conditions under which EXISTING GPS receivers would work WITHOUT MODIFICATION. Thus it is also no surprise to to us that GPS users would frequently find themselves in such conditions. The report states taht 75% of the receivers would be impacted when within 100m (328 feet) of the base station. This is fairly close to the basestation, and such close range only provides 76 dBm of attenuation (free-space) due to propagation leading to a received power at the GPS unit of (62 dBm-76 dB) -14 dBm — a strong signal level. The GPS units must then filter that signal by more that 100 dB to minimize the effect of the LightSquared signal on its performance. It is not surprising that standard commercial units have such filtering when they were likely designed assuming adjacent signal levels of -120 dBm not -14 dBm!
All of this is the backdrop to the FCC’s decision that it has to address the fact that even if LightSquared operates well within the technical limits of their license, such operation will still degrade the operation of existing GPS receivers not designed to accommodate such signals. As for our prediction as to how this will turn out…as there are more voters with GPS units than voters with LightSquared units, Questiny has always believed that the FCC will eventually side with the GPS community, and revoke LightSquared’s license. From there, LightSquared will likely sue the FCC for damages, and the FCC will find other spectrum for LightSquared. All of this will likely be too late for LightSquared to achieve sufficient revenue to remain solvent, and once again, LightSquared will find itself at the brink of bankruptcy.