Symmetricom: LightSquared is not the only risk to mobile network GPS systems

Concerns that the 4G network LightSquared plans to build could interfere with global positioning systems hit the mainstream media this week, with the Wall Street Journal reporting yesterday that public safety officials near a LightSquared test location experienced GPS outages. In telecom, GPS systems are often used to synchronize timing between cellular base stations to help ensure smooth hand-off of mobile communications as end users travel from coverage area to coverage area.

A LightSquared exec told the WSJ that the company has developed a fix that could solve the problem.

GPS systems vulnerable to jamming
But LightSquared isn’t the only potential risk to mobile operators’ GPS systems, said Manish Gupta, vice president of marketing for the communications business unit at Symmetricom, in an interview. Symmetricom manufactures synchronization equipment and components, including GPS-based and other options.

GPS systems are vulnerable to jamming and spoofing from devices costing as little as thirty or forty dollars, Gupta said. “It’s easy to jam [a system] in a localized manner,” Gupta said. “It happens frequently but not on a widespread basis.”

To guard against GPS outages caused by jamming or, potentially, by LightSquared, Gupta said mobile operators have at least two options.

One option is to use a high-performance oscillator that can hold precise timing from the GPS system for several hours until the GPS system becomes operational again. Another alternative, he said, is to implement synchronization and timing based on the IEEE 1588 standard as a backup to GPS.
Many operators are already looking closely at implementing 1588 as a method of providing timing and synchronization for 4G networks so that voice calls can be carried in IP format over Ethernet backhaul networks, thereby minimizing backhaul costs and simplifying network management.

Another timing and synchronization option that mobile operators are considering for that purpose is Synch-E. But Gupta said that option is not likely to be implemented for several years because it does not yet support phase synchronization and it requires substantial network equipment upgrades.