Leveraging the respective strengths of two traditional mobile location solutions could improve the accuracy of location information associated with emergency 911 calls from cellular phones, according to TruePosition, a provider of location technology.

Currently, the two primary technologies used to estimate the location of wireless 911 callers are assisted GPS (A-GPS) via satellite and uplink-time difference of arrival (U-TDOA), which uses triangulation via base stations in a wireless network. Historically, A-GPS has proven effective in rural locations, while U-TDOA has been more effective in more populous environments, where more base stations typically are located.

While carriers are migrating to A-GPS, TruePosition — a provider of U-TDOA solutions — believes the FCC should consider mandating a hybrid technology approach in future regulations to ensure more reliable and more accurate location information.

"Combining A-GPS in unobstructed environments with the complementary high accuracy of U-TDOA in urban and suburban indoor environments will provide 'best of both worlds solution,'" TruePosition stated in a presentation company officials made to the FCC.

The need for U-TDOA is especially apparent in urban environments, where A-GPS often is ineffective because tall buildings block the ability for a satellite to locate an emergency caller. This same problem exists when an emergency caller is located indoors — something that is becoming increasingly common, according to Brian Varano, TruePosition's director of marketing.

"People are making 911 calls from their cell phones, and the problem is increasing, because a lot of people are stopping their fixed-line service and are moving to a cell-phone-only lifestyle," Varano said.

Under the hybrid scenario, an emergency caller's location would be estimated by A-GPS and U-TDOA. If a satellite has a clear link to the caller, the A-GPS result would be used; if no such link can be made, U-TDOA would be used, Varano said. In cases where both technologies have effective links, combining the results can provide more reliable and better accuracy, he said.

And implementing a hybrid solution is realistic, as TruePosition has shown in a Delaware test program earlier this year that was the subject of a recent Ovum white paper.

"So, to all those naysayers out there that say that A-GPS and U-TDOA is just stuff on PowerPoint slides, it exists today — we've proven that it works," Varano said. "They're saying that it would be way too expensive to deploy, and that's not the case. They're also saying that it would be way too expensive to do this indoor-location testing. That's not the case, because we just did and can teach people how to replicate that across the nation."