4G interference: GPS manufacturers reject all claims

Brought into interference problems between their 4G LTE frequencies and GPS systems, LightSquared has accused GPS manufacturers of overflowing into their frequency ranges.

The idea put forward by LightSquared, a consortium supervised by Harbinger Capital fund managers, is a rather audacious one: building an LTE network in the United States which can be rented to carriers that are desperately looking for additional bandwidth to be able to keep up with mobile data growth.

The fund managers have obtained the rights to use a range of frequencies, with some being very close to those used by GPS systems… which apparently have a tendency of causing interference with positioning devices. Despite such claims being made by GPS manufacturers, LightSquared has for a long time rejected such criticisms, offering that a simple modification to their LTE devices would be enough to protect them.

At the same time, the consortium has negotiated an agreement to deploy an LTE network with Sprint Nextel for 9 billion dollars which will allow the carrier to become a carrier of this technology – an improvement to their current WiMAX network which is currently installed.

The problem is that conducted tests confirm that the interference between GPS systems and LightSquared LTE equipment still exist, which puts at risk the agreement signed with Sprint which has to be validated by the end of the year if they are to obtain the FCC’s support, and in the longer term the whole LTE network lease project which on paper appears to be rather lucrative.

In an about face that has surely been brought about by the urgent situation, LightSquared has completely changed their point of view, now confirming the interference is linked to the fact that GPS system manufacturers leek into their frequencies.


What is interfering with what?
The consortium has raised some concerns with the FCC through a press released in which they state that the use of frequency ranges that are too close to GPS signals in the future LTE network is not a good idea, while at the same time stating that they are not responsible for any interference that is claimed. They have requested that the regulator takes the appropriate measures to provide the frequency ranges that they have paid the licenses for, without interference.

"The one inescapable conclusion from two rounds of independent testing is that the incompatibility problem is not caused by LightSquared’s network", states Jeff Carlysle, Executive Vice President at LightSquared. He continues that GPS devices are designed to look into LightSquared’s licensed spectrum, which is where the seen interference is from.

He puts forward that spectrum rights had been obtained over the last eight years by various organisations and agencies, with most GPS manufacturers arriving late on the scene. It is these manufacturers that should have been taking the required remediation steps for a long time.

We will now see if the FCC listens to these points, with the GPS market being difficult to change (at least in the short term) due to the number of users affected and the cost it would take to correct the issue.

If this agreement between LightSquared and Sprint is rejected, it will be difficult for the consortium to continue as they don’t have the financial resources required to install their own LTE network. Unlike what is often stated, the 4G network doesn’t generally interfere with GPS navigation systems. It is only this particular case where we have seen issues with the frequencies used by LightSquared.