April 2002

From University of California - Los Angeles

UCLA researchers develop novel approach to finding lost 911 callers

UCLA engineers are working on something that may someday save your life. Electrical engineering professor Ali H. Sayed and his research group are creating technology that will enable medical personnel to use the nation's wireless phone network to pinpoint the location of someone in distress. Today, more than a third of the nation's 911 calls are made on mobile phones.

When someone uses a cell phone to call 911, it is often difficult for police to locate that person without help from the caller. Prompted in part by a Federal Communications Commission (FCC) demand to address this growing public safety problem, researchers nationwide, including engineers at UCLA's Henry Samueli School of Engineering and Applied Science, are looking at how location-based technology can help create a nationwide emergency service called "enhanced 911," or E911.

Sayed agrees with the FCC that cellular phones are becoming indispensable safety devices. "They are important tools for calling for help," Sayed said. "I think we should push to move this technology further and faster, of course keeping in mind issues of privacy."

Unlike fixed-line phones, which are tied to a house address, a mobile phone can use any one of thousands of towers in the country. Today, phone carriers can pinpoint calls based on the location of a tower, but the towers might be up to 20 miles apart.

Some telephone companies have responded by equipping some of their phones with location-finding technology, but no nationwide system is yet in place to protect all Americans, no matter where they get into trouble. That is not good enough for Sayed.

So Sayed's research team at the UCLA Adaptive Systems Laboratory has found a way to solve many of the problems delaying the widespread use of location-finding technology. They have developed a set of algorithms that manufacturers could use when building such networks.

"At the Adaptive Systems Lab, we are experts at understanding the constantly changing conditions in a communications environment, including wireless communication," said Sayed, who established the lab when he joined the faculty in 1996. "By exploiting what we know about the caller's environment, we can make our receivers more adaptive and accurate."

Sayed became excited about how adaptive systems could address the E911 problem after one of his graduate students returned from a summer internship spent with a colleague and high school friend of Sayed's, Dr. Louay M.A. Jalloul, then a scientist at Motorola and an expert on wireless communications.

In the world of adaptive systems, devices learn by interacting with the environment, continually improving their performance. For example, an adaptive phone receiver would respond to obstructions that may block a signal -- like a tall building -- and plan ahead for similar situations. Adaptive systems are used to enhance everyday communications in a number of ways, like removing the echoes from cellular phones and boosting the performance of hearing aids.

In lab tests involving the UCLA algorithms, Sayed has located a caller to within 30 to 40 feet 67 percent of the time, an even higher standard than the FCC's order of 328 feet. In a few years Sayed expects to locate callers within a slightly larger radius, but far more reliably -- 985 feet 95 percent of the time, which will be the FCC standard starting in 2006.

Similar to traditional means of electronic navigation, Sayed uses triangulation to determine the location of a caller. "If I can tell how long it took a signal to arrive from one place to me, I can tell the distance, because the signals are traveling at the speed of light," Sayed said. "If I do the same thing at other base stations, I can create intersections to determine where you are."

The trick is estimating the time for a specific phone signal among thousands of similar signals being transmitted and received by other callers. This is where Sayed's expertise in adaptive systems becomes important. Signals bounce off of buildings, causing the signals to fade, or become overpowered by signals from phones closer to the tower. In some cases, the caller is in a moving car, which also makes it difficult to pinpoint location. Sayed's algorithms are meant to counteract all these environmental hurdles and exploit certain characteristics about the communications channel in ways not studied before.

Some people are pursuing the use of global positioning system (GPS) hardware and software to implement E911, since the technology already exists. Though using GPS in a handset would be one way to solve the problem, there are disadvantages to the GPS solution. "You'd have to employ GPS technology in your handset," Sayed said, "which adds weight to your phone, robs the phone of power and it would be expensive to install. It would also be slow to pinpoint locations."

Sayed pointed out another problem with a GPS approach. "It cannot accommodate the millions of handsets that are already on the market. An ideal solution would perhaps involve a combination of GPS technology and infrastructure-based technology."

The research team at UCLA's Adaptive Systems Laboratory has been testing their location-finding algorithms for more than three years. To learn more about the Adaptive Systems Laboratory visit www.ee.ucla.edu/~asl/index.html.

This article comes from Science Blog. Copyright 2004

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