NavList:

   

Reply

�Based on the test results and analysis to date, the LightSquared  
network would effectively jam vital GPS receivers,� General William L.  
Shelton, commander of U.S. Air Force Space Command, told the members  
of the House Subcommittee on Strategic Forces [yesterday]. �And to our  
knowledge thus far, there are no mitigation options that would be  
effective in eliminating interference to essential GPS services in the  
United States.�

More: http://www.insidegnss.com/node/2779

-- Richard Langley


On 16-Sep-11, at 1:47 AM, Frank Reed wrote:

> Gary,
>
> There is still a fair amount of controversy over the technical  
> aspects here as well as the bureaucratic machinations at the FCC and  
> elsewhere. I don't think there's any evidence that the Obama  
> Administration cheated or engaged in corruption, but they do  
> consider national wireless broadband a major policy objective so  
> they have asked the FCC to fast-track the approvals process. The  
> LightSquared system uses frequencies which are outside but adjacent  
> to the GPS signal band. The exceedingly weak GPS satellite signals  
> are susceptible to the slightest overlap from the "tails" of other  
> signals. LightSquared claimed a couple of months ago in their report  
> that the vast majority of GPS receivers including, according to  
> them, one-hundred percent of the GPS circuitry in smartphones (by  
> far the largest commercial users of GPS) are not affected by this  
> interference. They also claim that very cheap filtering circuitry  
> could have made all GPS hardware immune to this interference if it  
> had been designed and built according to specs. That latter claim is  
> nice in theory, but seems rather weak in practice. Then again, if  
> they're right, then the makers of those devices should perhaps have  
> to pay to retrofit or replace them any which depended on empty  
> spectrum outside the standard GPS range.
>
> It is worth noting that LightSquared received licensing to use that  
> spectrum adjacent to the GPS band in 2004. Note the year. That's  
> smack in the middle of the Bush Administration, not the Obama  
> Administration. This tends to dilute the argument that there is some  
> sort of political corruption at work here. Of course, their plans  
> are a work in progress, and the usages envisioned in 2004 are very  
> different from the current plans. There have been many modifications  
> to the licensing in the past two years. Those can legitimately be  
> questioned for political influence.
>
> Incidentally, the primary interference concern at this point  
> apparently applies almost exclusively to high-precision GPS which  
> yields positions accurate to some few centimeters.
>
> -FER
>
>
> ----------------------------------------------------------------
> NavList message boards and member settings: www.fer3.com/NavList
> Members may optionally receive posts by email.
> To cancel email delivery, send a message to NoMail[at]fer3.com
> ----------------------------------------------------------------
>

-----------------------------------------------------------------------------
| Richard B. Langley                            E-mail:  
lang@unb.ca         |
| Geodetic Research Laboratory                  Web: http://www.unb.ca/GGE/ 
  |
| Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506  
453-5142   |
| University of New Brunswick                   Fax:      +1 506  
453-4943   |
| Fredericton, N.B., Canada  E3B  
5A3                                        |
|        Fredericton?  Where's that?  See: http:// 
www.fredericton.ca/       |
-----------------------------------------------------------------------------

   

Reply