Cell Phone Network Threatens GPS Signals

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GPS service providers are going up against 4G network providers as they contest issues such as bandwidth and satellite signals. More specifically, Garmin and the US military are facing off against LightSquared, which intends to set up 40 000 ground transmitters that have the potential to disrupt vital GPS signals.

According to an article by Andrew Wood on AIN Online, the transmitter network proposed by LightSquared would effectively cause widespread GPS jamming and disrupt services over huge swathes of the US. Garmin conducted laboratory tests which demonstrated that each transmitter would disrupt GPS signals within a 13.8 mile radius and completely jam signals within 5.6 miles.

Meanwhile, an article on Flight Global cites General William Shelton who said that the network would disrupt signals up to 12 miles in the air (with similar findings to Garmin in the ground). The potential for havoc in the air is frightening to contemplate.

According to a provisional permit issued to LightSquared by the Federal Communications Commission (FCC), it is LightSquared's responsibility to ensure that its network doesn't interfere with other signals. The company has effectively been ordered to work with the federal government and the GPS industry to ensure that vital signals are not jammed.

Scott Canon breaks the problem down into layman terms: LightSquared's network would use both cell phone towers and satellites to ensure that its customers are always in range of cell a phone signal. Basically, when towers are out of the reach the phones would switch to satellite signals to keep conversations and online browsing going. The problem is that the satellite signal concerned uses a band that is adjacent to the one used to provide GPS signals. The risk is that cell phone users will overcrowd their band and will flow into the GPS band and, according to Dale Hatfield, jostle it out of position. Hatfield, who is an ex-chief engineer and FCC technologist, says it's a matter of elbow room - in other words, a certain amount of pushing and shoving is inevitable.

Canon reports that despite the lab tests conducted by Garmin, LightSquared maintains that its network can operate side-by-side with the GPS band. The company's executive vice-president for regulatory affairs, Jeff Carlisle says that it has already invested $9 million to make sure that interference is not an issue and claims that if a problem exists it is only with highly sensitive GPS receivers. Like the kind used by the military and air force perhaps?

The problem is an interesting one with serious consequences for both sides. One thing is for sure, it'll require a lot more testing and a lot more money to settle it.

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