Home > Articles

  • Print
  • + Share This
This chapter is from the book

A Cry for Help

With more than 118,000 calls a day made in the United States to 911 and other emergency numbers from wireless phones, the Federal Communications Commission thought it might be a good idea to make it easier to determine the location of people making an emergency call—even if they don't have a clue where they are. From this, Enhanced 911, or E-911, was born.

The media picked up on this early with a story of a New Jersey family that ran off the road in the middle of Nebraska late at night without knowing where they were. They called E-911 and the system tracked them to within a few hundred meters and sent help. Technology to the rescue . . . again.

But what technology? Nearly every major U.S. carrier has filed a request for an extension with the FCC, claiming the technology wasn't up to the task. At least not under the tight location restrictions required by the commission.

The current E-911 rules were adopted in 1996 and reflected the technology available at the time, which anticipated only a network-based approach called automatic location identification (ALI). Now, with the FCC's E-911 plan fully envisioned, emergency response centers can locate the caller by using the nearest cellular towers to triangulate the call and determine which tower is generating the strongest signal from the emergency call. But then the FCC revised its rules to make room for other options.

Under the new rules, wireless carriers who employ a location technology with new, modified, or upgraded cellphones were required to begin activating and selling them no later than March 1, 2001. At least half of these handsets were to be ALI-capable no later than October 1, 2001. Also, at least 95% of all new digital phones were to be ALI-enabled and activated for this service no later than October 1, 2002.

For network-based E-911 to work, the revised FCC rules call for carriers to achieve 100-meter accuracy for 67% of mobile emergency calls and 300-meter accuracy for 95% of all of these calls. Carriers going the handset route, which means they will use the satellite-based Global Positioning System (GPS), which is more accurate and more reliable, must demonstrate an accuracy of 50 meters for 67% of its emergency calls and 150 meters for 95% of these calls.

Several carriers, including ALLTEL, U.S. Cellular, and Nextel Communications, informed the FCC early on in the process that they were opting for a handset-based E-911 system. Others, including Verizon Wireless and Western Wireless, for example, opted for the network-based system. But they have other technology choices. Most of the carriers selecting the network option favored a combination of something called time difference of arrival (TDOA), which calculates a phone's position based on the speed the signal reaches multiple nearby antennas, and angle of arrival (AOA). With AOA, cellular towers identify the direction from which a signal is coming and then pilots the direction of the incoming call based on a reading from two towers. AT&T Wireless and VoiceStream announced plans early to adopt another hybrid system known as enhanced observed time difference (EOTD). The major supplier of EOTD technology, which works only with cellphones or other wireless devices based on the European-developed digital Global System for Mobile Communications (GSM) system, is U.K.-based Cambridge Positioning Systems. CPS's Cursor software does not require any hardware modification to the handset, only some low-level reprogramming and sufficient memory.

The advantage of using GPS-equipped cellphones is that it gives carriers a running start on providing its customers with a wide array of location-based services. These include navigation data (including directions and information on nearby restaurants and retail outlets), traffic and weather reports, and a wide range of regional entertainment options.

As far as the law enforcement and other emergency services agencies are concerned, the carriers aren't moving fast enough. The Association of Public-Safety Communications Officials (APCO) punched out news releases for months on vehicular deaths across the country that it said might have been avoided if the caller's location could have been determined by E-911 technology.

At this point, it's just a matter of time. Eventually, everyone will have a portable phone with access to some kind of E-911 capability. The fear is that with wireless carriers pushing for new revenue-generating, location-based services, someone responding to an accident might be sent to a drug store on the next block.

  • + Share This
  • 🔖 Save To Your Account