Yesterday the US House of Representatives’ Committee on Transportation and Infrastructure heard concerns that LightSquared’s proposed LTE network would interfere with flight safety.
John D. Porcari, the Deputy Secretary for the US Department of Transportation, asked the committee to introduce standards that regulate the usage of GPS’ neighboring spectrum. He told the hearing that precise GPS systems like those found in aircrafts need to utilize wide-band receivers that also pickup signals outside the regulated spectrum.
When asked why LightSquared’s proposed network interferes with GPS, Porcari told the committee (pdf):
The test results showed that LightSquared’s design and filters effectively prevented “out-of-band” emissions; in other words, their powerful broadband signal was not ‘leaking’ into the adjacent GPS band. However, the powerful broadband signal operating in the upper and lower 10 MHz of the MSS band (5 billion times the signal of GPS even ½ a mile from a LightSquared transmitter) overwhelmed filters and effectively blocked GPS signals in most of the devices tested in what is referred to as “overload interference”. Also, interference caused by LightSquared’s design of a dual carrier signal (upper and lower 10 MHz channels combined) resulted in an inter-modulation product in the adjacent GPS frequency band.
LightSquared’s proposed cellular data network can’t be made compatible with GPS, and the government should set interference standards to prevent future conflicts over companies trying to establish such services, Deputy Transportation Secretary John Porcari told the House Aviation Subcommittee hearing on Wednesday.
Perhaps anticipating the testimony, LightSquared asked the FCC to regulate GPS receivers to prevent them being affected by their their use of adjacent spectrum. But new legislation won’t prevent current GPS receivers from being affected by the much stronger terrestrial signals of Lightsquared.
Airlines for America, the industry trade organization for the leading U.S. airlines, called for a government wide policy to protect the GPS spectrum in order to avoid any future threat of spectrum interference.
A bill to transform the nation’s air traffic control system with GPS, received final congressional approval Monday. The bill authorizes $63.4 billion for the Federal Aviation Administration over four years, including about $11 billion toward the new GPS-centric air traffic system.
The Next Generation Air Transportation System (NextGen) allows pilots and dispatchers to select their own, usually direct flight paths, rather than follow the existing interstate highway-like grid in the sky.
With NextGen, each airplane will transmit and receive precise information about the time at which it and others will cross key points along their paths. Pilots and air traffic managers on the ground will have the same precise information, transmitted via data communications.
A plane’s Automatic Dependent Surveillance-Broadcast (ADS-B) broadcasts precise data in real time about the plane’s location, speed, and altitude. This increased situational awareness will allow air traffic controllers to place air routes in tighter proximity to each other.
Automatic Dependent Surveillance-Broadcast consists of two different services: ADS–B Out and ADS–B In. ADS–B Out periodically broadcasts information about each aircraft, such as identification, current position, altitude, and velocity, through an onboard transmitter. ADS-B In receives data, such as direct communication from nearby aircraft. ADS–B uses a frequency around 1090 MHz.
Eventually, FAA officials want the airline industry and other aircraft operators to install onboard GPS that updates the location of planes every second instead of terrestrial radar’s every six to 12 seconds. That would enable pilots to tell not only the location of their plane, but other planes equipped with the new technology as well — something they can’t do now.
LightSquared’s woes weigh on Philip Falcone’s Hedge Fund, observes the NY Times. LightSquared now appears doomed by broad opposition.
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