View from the Top

There is an optimistic future for 911 wireless location accuracy

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By George Rice, iCERT. By leveraging readily available technologies like Wi-Fi and Bluetooth, carriers can provide public-safety answering points (PSAPs) with better accuracy and dispatchable addresses that can be conveyed quickly to first responders when 911 emergency calls are made, even if the communication is initiated from a wireless device from inside a building.

By George Rice, iCERT

It used to be so simple. When someone made an emergency call from their wireline phone—the only kind of phone at the time—the phone company would immediately provide the address, which was based on the billing information they had for that phone line. In a matter of seconds, the address would be displayed on the 911 telecommunicator’s screen, and moments later, first responders were on their way to the exact location of the emergency.

Everything has changed with the emergence and rapid growth of wireless phones. Today, locating 911 callers is more challenging, because wireless phones allow them to make an emergency call from almost anywhere. This was not, and still is not, a problem for calls in which the victim is conscious and knows where they are; in such circumstances, telecommunicators generally have no trouble getting the caller to provide the location needed to quickly make the appropriate dispatch decisions. Things become more problematic when emergency callers are unable to provide such information, such as when the caller is disoriented, is speech or hearing impaired, does not speak English, or is unable to speak, because doing so would place the caller in danger.

In 1997, technology emerged that provided the caller’s telephone number and the location of the cellular tower that transmitted the call, referred to as “Phase I” wireless location accuracy. Phase I represented a quantum leap forward—having the callback number for the cellphone was a huge benefit for telecommunicators, because it meant that they could call the victim back if the call was terminated for some reason—something that happened quite often in the early days of cellular communications. However, knowing the location of the cell tower was only marginally helpful, as the coverage area of a tower can be quite large. The public-safety sector clamored for something better—and rightfully so, as quickly and efficiently locating victims is a critical factor in emergency response.

So, wireless location technology continued to evolve. With the emergence of “Phase II” technology, 911 call takers were provided with information about the caller’s location, and advances in Phase II technologies now enable location information that is accurate within 50 meters or less for many calls. The use of Global Positioning System (GPS) technology—common in many commercial applications—helped advance the deployment of Phase II technology. However, while GPS works consistently when a caller is outdoors, it does not work as well when the caller is indoors, because the satellite typically cannot get a signal from the caller’s device.

Today, wireless phones have replaced wireline phones as the communications device of choice. From 2003 to 2013, industry estimates show almost a three-fold increase in annual wireless 911 calls, from 50 million to more than 146 million. With this growth in wireless has come an increase in the number of 911 calls made from indoors. As this trend will most assuredly continue to rise, we clearly need a more effective solution for wireless location indoors.

So, if a “good, better, best” label was to be applied to current wireless location technology, Phase I would be “good” and Phase II would be “better.” But the public-safety sector—again, rightfully so—wants “best,” which means the ability to generate a dispatchable location—addresses that include apartment and office suite numbers—for wireless 911 calls, regardless of whether the caller is indoors or outdoors. The good news is that technologies are emerging that could potentially give public safety exactly what it wants.

In recent years, there has been significant advancement in the development of wireless location technologies that do a better job of locating wireless 911 callers, including calls made from indoors. These include new satellite constellations (e.g., GLONASS) that will enhance the accuracy of GPS-based solutions, new Observed Time Difference of Arrival (OTDOA) technology that works in concert with advanced LTE wireless networks, and new location beacon systems that would blanket a city with high-power beacons that could be sensed by wireless phones. 

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