Symmetricom thinks it can prevent interference to GPS from LightSquared’s network
Symmetricom, a company that provides network synchronization technologies, believes it has a fix for the potential interference that LightSquared’s proposed wholesale Long-Term Evolution (LTE) network might pose to the GPS community.
LightSquared’s plan for a nationwide wholesale LTE network increasingly has come under fire because of the network’s potential to interfere with GPS signals across the United States. The company plans to launch services using L-band satellite spectrum, which sits next to GPS spectrum.
While fixes such as installing filters or moving GPS antennas have been bandied about, Symmetricom recommends the use of packet-based primary reference source (PRS) synchronization solutions such as its TimeProvider 1500, which utilizes IEEE 1588 Precision Time Protocol (PTP).
The company believes Packet PRS solutions would totally eliminate potential GPS interference from LightSquared antenna sources because GPS isn’t required at Packet PRS locations to ensure highly accurate timing, which is essential for network synchronization to occur.
But here’s some background first. Legacy mobile networks have always relied on Time Division Duplexing (TDM) to provide synchronization to base stations. But as access networks such as LTE migrate to Ethernet, the traditional synchronization distribution chain is broken. The lack of network synchronization results in dropped calls and service degradation. So packet networks require a IEEE 1588 technology to provide TDM-equivalent synchronization services to IP-enabled base stations. In short, a system of components that contain real-time clocks are all synchronized to each other within the system.
Back in April, Symmetricom announced it had worked with Nokia Siemens Networks to successfully deploy IEEE 1588 equipment in more than 50 networks globally.
Symmetricom said that the technology, which is basically becoming a requirement for packet mobile networks, can be deployed by those using GPS receivers because they can deploy standalone servers and software clients.
“Anyone can deploy this,” said Michelle Pampin, director of product and channel marketing at Symmetricom. She added that IEEE 1588 also solves several common problems that exist in the mobile infrastructure and GPS world.
“The issue right now is you have one service provider given that piece of spectrum that is rubbing closely on another piece of spectrum. So you run the risk of GPS going against GPS and knocking each other out,” she said. “LightSquared is one issue, but frequency and timing requirements are getting tighter for LTE. Jamming and spoofing (of GPS) are other known issues today.”
Manish Gupta, vice president of marketing with Symmetricom, said that IEEE 1588 also will assist in providing greater accuracy for E-911 calls and a solution for network timing for small cells, such as femtocells.
“E-911 is certainly about precise timing to base station and devices,” Gupta said. “Devices being GPS-equipped, triangulation and several layers come into play in location, but the foundation of that is precise timing for infrastructure, so 1588 brings a new level of opportunity for making more precise location fixes.”
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