LightSquared to magic away GPS interference in 2 weeks
US Space Commander begs to differ
LightSquared has signed a deal with Javad GNSS that will see GPS filters capable of resolving interference issues, within two weeks.
That's remarkable, not least because US Air Force Space Commander William Shelton recently claimed that such filters would cost billions and take decades to install, if they could be made to work at all. So clearly there's a disparity of views here which need more attention.
Javad Ashjaee, CEO of Javad GNSS, is already a proponent of LightSquared, despite being in the GPS industry which is generally opposed to LightSquared's plan to put high-powered transmitters in frequencies neighbouring GPS. He's gone on record welcoming LightSquared's box 'o frogs plan as drawing attention to the problem of GPS interference.
LightSquared has a licence, from the FCC, to transmit at frequencies formerly reserved for satellite phones. The problem is that GPS kit, particularly highly-accurate GPS kit, has a tendency to pick up neighbouring signals in its search for satellites, which is why Shelton reportedly said the two "cannot coexist".
But LightSquared reckons better filters are all that's needed, and now claims it will have 25 working prototypes of such filters within the next couple of weeks.
That puts them in time for the FCC's latest round of testing, so if they work then LightSquared could get the go ahead for network construction next year, but there are plenty of people who don't believe they will.
Objective testing is to be welcomed, as the situation shows no signs of getting any less political. Yesterday a group of House Republicans asked for copies of all communication between the White House and Harbinger/LightSquared, and its founder Philip Falcone, following accusations that the Obama administration had intervened on behalf of the company.
But the FCC is planning proper empirical tests, using the new filters, hopefully establishing whether LightSquared can deploy without knocking out GPS across the USA. Sadly even that isn't a long-term solution: LightSquared has already dialled down the power and shifted frequencies to avoid GPS, but with a view to ramping up and shifting again as soon as the technology allows it, which will need even better filters.
GPS can't be allowed to fail, so the FCC, LightSquared and most of the industry will be hoping the filters work as promised, though for some nothing less than abandoning the scheme entirely will ever be acceptable. ®
US Air Force Space Commander William Shelton
Best. Job title. Ever.
Follow the money
Man who stands to make a ton of money making filters to allow GPS and LightSquared to cooperate says he approves of LightSquared. What a surprise! And how do they propose to address all the GPS units in current existence? Unless the filters are fitted to the phone and not the GPS?
So what magic filters are these? Lightsquared could filter their signals so the out-of-band power that leaks into the GNSS band is 'negligible', but that's not easy or cheap, especially if band-edge phase performance is important. However there is still lots of power in their own band which cheap GPS receivers won't necessarily filter effectively, and will get aliased by the digital sampling process into the signals the GPS software has to sort out.
Now that GPS has had augmentation and integrity features added by SBAS services such as WAAS & EGNOS, it can be used as a primary navigation aid by aircraft, so that's going to have a severe impact on the aviation industry if GPS can be randomly unreliable due to interference, continent-wide in the US.