Letters to the Editor: LightSquared Satellite Case Skimpy

July 1, 2011  - By

LightSquared Satellite Case Skimpy

Thank you for the story “LightSquared, FCC Rebuttals Distort Record.” One thing worth clarifying: you state, “It appears that the purpose of Lightsquared’s satellite service is, now, to provide ancillary service in remote areas not covered by the ubiquitous primary terrestrial network, or in the event that the terrestrial network is destroyed — exactly the opposite of what the FCC authorized and the GPS industry had understood and agreed to.”

But even this can’t work unless they are going to limit the number of subscribers in remote areas. A 4G user will expect decent wireless data throughput, but the subscriber’s connection is shared with other users within a spotbeam covering a large area. All connections must fit within the bandwidth of the single beam.

Cell networks get around this problem by frequency re-use, possible since each cell covers a small geographic region. The key characteristic of a cellular network is the ability to re-use frequencies to increase both coverage and capacity.

Admittedly, the LightSquared satellite, SkyTerra-1, is a very sophisticated space vehicle with a record 500 spotbeams. However, it provides a maximum user data rate of 300–400 Kbps, quite a bit short of what you would expect from a 4G-LTE connection. And at 400 Kbps, a 20-MHz spotbeam could still support only 50 to 100 connections.

Another problem with using the satellite link is that although they have managed to solve the problem of requiring a special user handset, the user will still have to be outdoors and in the open to communicate with the satellite. And it is a geostationary satellite, which means high latency — at least 1/4 second. Using this for voice would create user annoyance.

LightSquared should stop using the word “ancillary” and stop pretending that their network has a significant satellite component. It is going to have to be all ground-based if they are to provide 4G connectivity. It’s really starting to sound like the satellite is just a way for LightSquared to meet their FCC requirement.

— Mike Whitehead
VP Technology, Hemisphere GPS

[Ed: citations and some discussion ommitted for space; available on request.]

On Eric Gakstatter’s Survey columns:

Keep up the good work. I find your e-newsletter columns the best way to stay informed [on the LightSquared issue].

— editor, survey magazine

Sounding Off

When someone comes onto the basketball court with a hockey stick, the referees should not negotiate rule changes. Anything that allows LSQ to proceed either on the high or low ends of their allocated spectrum will in the long run be a blow to PNT users and suppliers worldwide. While this may very well end up as a compromise to the detriment of us all, now is not the time to concede any ground. He who flinches, loses, and this is not the time for engineers to give ground. It will set a precedent that lawyers will use again to decimate the spectrum in the future.

—Informed particpant

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