AT&T Wireless switches E911 technology

The wireless carrier planned on deploying a technique called enhanced observed time difference (EOTD), which uses up to four cellular base stations to pinpoint a cell phone's location by measuring the arrival times of the call at various cellular antennas.

But the technology has trouble meeting the accuracy standards set by the Federal Communications Commission (FCC), according to FCC records filed by AT&T Wireless and various other wireless carriers.

AT&T Wireless will instead begin using another technique, called time difference of arrival (TDOA), an AT&T representative said. EOTD relies on software packed into cell phones. TDOA uses software on a carriers' network to determine a cell phone's position.

"The (latest phase) of E911 has been a tremendous challenge for the entire wireless industry," said Rochelle Cohen, AT&T Wireless representative. "It's a fundamentally different and far more difficult task to locate mobile phones than it is to locate stationary phones."

Part of the same agreement calls for AT&T Wireless to pay $2 million to the FCC to end an inquiry into why the carrier missed an Oct. 1, 2001, deadline to begin installing the EOTD equipment. The payment is not an admission of guilt.

All carriers have until 2005 to make it possible to locate a cell phone dialing 911. That's currently possible only for landline phones. The task has proven much more difficult than the FCC imagined in 1996 when it crafted the mandate. Every U.S. carrier missed an Oct. 1, 2001, deadline to begin installing the equipment in their networks.

AT&T Wireless is the second wireless carrier to begin making moves to switch away from using EOTD. Last week, Cingular Wireless halted shipments of EOTD gear. It has also begun a trial with a different technology from TruePosition.

A third U.S. carrier, T-Mobile, still plans on using EOTD. A representative at the Seattle-based carrier couldn't be reached for comment Wednesday on whether it plans to switch.