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California’s wireless / VoIP deployments

The state of California wants to enable public safety answering points (PSAPs) to provide the fastest, most reliable, cost-effective, and secure access to emergency services, from any device, anywhere in California. It is a lofty goal, for certain, but one that is attainable, according to James M. Thompson, California’s Wireless E9-1-1 project coordinator ( gov).

He was a featured speaker at the annual COPSWest meeting, sponsored by the California Peace Officers’ Association, and held at the Ontario, CA Convention Center.

Thompson said wireless is the focus of the future as more individuals and households abandon their home telephone landlines in favor of wireless communications. He explained that U.S. wireless subscribers grew from 55 million in 1997 to 253.4 million in 2007. Worldwide, there are 2.3 billion wireless subscribers. More than 80% of the U.S. population uses cell phones, translating to 2 trillion wireless minutes in 2007. At present, more than 12% of U.S. households are wireless-only, having given up their traditional landline phones. It is anticipated that the trend to wireless will only continue, he said. It is already predicted that one out of five households will be wireless-only in 2009.

Of the 23.3 million E9-1-1 calls in California during 2007, 11.6 million (50%) were wireless calls. Current figures say that over 35,580 E9-1-1 wireless calls are made every day in California. Taking those wireless 9-1-1 calls directly will allow emergency services to respond quicker to their communities’ needs, he said—something vital to handling medical emergencies, fire response, and crime in progress response.

Under FCC Order 94-102, wireless service providers (WSPs) need to deliver Phase I callback number cell site and sector information, and Phase II latitude and longitude coordinates, Thompson said. California Public Utilities Code Section 2892 allows PSAPs to receive wireless E9-1-1 calls when certain requirements are met and an agreement is made between the PSAP, the California High Patrol (CHP), and the Telecommunica-tions Division.

Phase I data indicates that all wireless service providers (WSPs), except Sprint PCS, display the address and latitude / longitude of the cell site as Phase I data. Sprint PCS displays the address of the cell tower and the latitude / longitude of the cell sector centroid. “This difference is important for mapping applications,” said Thompson. Improved locating of the caller’s site will lead to quicker handling of the emergency.

WSPs have two solutions for providing Phase II data—a network-based solution and a handset-based / GPS solution. AT&T, Cingular, and T Mobile are using the network-based solution. The FCC requires that the accuracy of the latitude / longitude provided be within a radius of 100 meters 67% of the time, and within a radius of 300 meters 95% of the time, Thompson said. Nextel, Sprint, Metro, Verizon, and a few others use the handset-based solution. For those, the FCC accuracy requirements are latitude / longitude accuracy within 50 meters 67% of the time, and 150 meters 95% of the time.

Thompson explained that the handset-based / GPS system relies on a wireless phone chip that receives signals from three or more of the 24 Earth-orbiting satellites. The chip measures the amount of time for a satellite’s radio signal to reach the phone, and, by calculating the speed of the radio signal, the distance from the satellite can determined. The phone then measures the time for a second satellite’s signal, and the phone can be determined to be at one of the two points where the first and second calculations overlap. When the phone receives a signal from three or more satellites, the location becomes even more precise. It is then transmitted to the 9-1-1 center, to be displayed on a map so a dispatcher can determine the proper responders.

Of course, most callers will know their location and can merely tell the 9-1-1 center, but for those callers who don’t know, or who are lost, or under duress from a crime or medical emergency, Phase II data for locating the caller is critical. Independent CMRS providers are deploying a new class of wireless service utilizing a dual band (800 mHz / IDEN) handset. The use of omni-directional antennae for IDEN allows simultaneously covering several hundred square miles, and independent CMRS calls will be routed only to the CHP, due to the large geographic area being covered. The first such project is being deployed in central Riverside County, with some overlap into San Bernardino and Imperial Counties—a vast, desert area with few cities or towns and much farm, ranch, range, and wilderness land.

The California “wireless team” involves PSAPs, the CHP, wireless coordinators in each of the state’s counties, WSPs, database providers, incumbent local exchange carriers, vendors, and the state’s 9-1-1 office. The current wireless deployment stands at 383 PSAPs and 24 CHP dispatch centers. He added that all 24 CHP dispatch centers are taking Phase II calls, and 32 PSAPs have not requested to deploy. The 2007 figures for funded 9-1-1 positions and workstations see the local PSAPs at 1,776 or 91% and the CHP at 167 or 9%. But the CHP received 50,930 calls per workstation, and local PSAPs received 8,354 calls per workstation. The disparity is food for thought, Thompson pointed out, adding, “The more we get the calls spread, the faster we’ll be able to handle them.” From September 2007 to August 2008, the average number of wireless E9-1-1 calls per month was more than 1,082,400.

Voice over Internet Protocol (VoIP) or computer-accessed phone service over the Internet is a trend that will also affect E9-1-1, said Thompson. There were about 4.2 million subscribers to such services in 2005, but that number is expected to increase to 18 million in 2009. FCC Order 05-116 requires VoIP providers to provide callback numbers and location information. Thompson explained that the E9-1-1 call path begins as a caller makes a 9-1-1 call (the caller must register the address with the provider), and the call goes to a selected VoIP positioning center where the address is validated and geo-coded to convert the address to latitude / longitude and to determine where to route the call. The call is sent to the appropriate emergency services gateway, which uses the information to determine to which PSAP the call should be delivered. Thompson added that in 2006, there was a total of 14,801 such VoIP E9-1-1 PSAP calls, and in 2007, the total was 40,937. Although that is not much in the total of E9-1-1 calls, he pointed out, it is an increase that might be pointing to future growth, and the need for better solutions for VoIP users of E9-1-1.

For more information on the California wireless E9-1-1 Project, visit 911/we911.

Stephenie Slahor, Ph.D., J.D., writes in the fields of law enforcement and security. She can be reached at

Published in Public Safety IT, Jan/Feb 2009

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