Wireless calls create emergency services challenge

Wireless calls create emergency services challenge

Dispatchers, swamped with 911 calls from cell phone users, try new ways to locate the callers

By George V. Hulme
Special to GCN






Capt. Joe Hanna and dispatcher Monica Graham monitor 911 calls in Richardson, Texas.



More than 100,000 times a day, emergency personnel answering 911 calls spend precious minutes determining the exact location of distressed callers who are using mobile phones. New technology could help public safety officials pinpoint callers' locations more quickly and accurately.

'The whole face of emergency calls is changing very rapidly with wireless phones. I'd estimate that 30 percent of all calls to 911 are now coming from a wireless connection,' said Capt. Joe Hanna, manager of the public safety communications center for the city of Richardson, Texas, and president-elect of the Association of Public Safety Communication Officials.

The number of wireless subscribers is growing, straining the nation's 3,700 public safety answering points (PSAPs).

Too far away

'More and more wireless calls are coming in and widening this problem. Sometimes the cell site information that is sent is all the way across the county, and the caller ends up reaching a PSAP that is not closest to the caller,' said Buddy Shaffer, 911 director in Sumner County, Tenn.

In December 1997, in an attempt to alleviate this problem, the Federal Communications Commission mandated that wireless operators transmit all wireless 911 calls from both subscribers and nonsubscribers to all of the nation's PSAPs.

The mandate is in two parts: Phase I, completed in April last year, required carriers to provide automatic number identification and cell site information to all PSAPs. Under Phase II, carriers must install technology by Oct. 1, 2001, that will let them pinpoint mobile 911 callers within a range of at least 125 meters. But despite the FCC mandate, wireless 911 service still remains spotty.

There are several competing technologies that carriers can choose to transfer location information to a PSAP. Network technology requires carriers to place transceivers within each cell location of their network. When an emergency call is placed, the signal from the phone must be received by three cell sites. The location is calculated by determining the signal strength to each cell and comparing the calculated time of arrival, and time distance of arrival or the angle of arrival of the signals.

This method works well in urban areas with a high concentration of cell sites, but in rural areas with a single cell the method won't work at all. And costs range from $20,000 to $50,000 per cell.

An alternative requires a fully functional Global Positioning System receiver to be built into each wireless phone. When a call is placed, the phone already knows its location and sends this information to the PSAP. The drawbacks to this system are increased battery drain and the phones' higher cost and weight.

The third approach is a hybrid of those two. GPS units track the 24 orbiting GPS satellites and pass critical information such as time, altitude, velocity and location to the handset. When a 911 call is made, the handset passes the location data to the PSAP.

Lucent Technologies Inc. of Murray Hill, N.J., and Qualcomm Inc. of San Diego recently announced a partnership to develop GPS-based wireless location technology that is accurate down to 15 feet outdoors and 100 feet indoors.

Both companies expect to have the technology ready by the 2001 deadline.

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