Editor’s Note: Welcome to our weekly Reality Check column. We’ve gathered a group of visionaries and veterans in the mobile industry to give their insights into the marketplace.
Many people are unaware of the location-based services that underpin the provision of essential public safety services in the United States. The chief example is Enhanced 9-1-1 (E911) calls, which enables wireless carriers to quickly and accurately locate the ever-growing number of 911 calls coming from cell phones. Given the frequent life-and-death nature of E911 calls, calculating a caller’s location as accurately as possible is vitally important.
In the 1990s, the Federal Communications Commission mandated that all E911 calls from cell phones be located by wireless carriers with specific location accuracy and reliability requirements. The accuracy and reliability of the location information was – at that time and still today – dependent on the type of location technique that the wireless carrier used.
To meet these strict E9-1-1 location regulations, wireless carriers have deployed two different technologies:
–Network-based technologies, where equipment installed in the wireless carrier’s network calculates the location of the phone.
–Handset-based technologies, where the location information is generated by a GPS chip installed in the phone.
Current FCC rules require that wireless carriers that use network-based technologies must locate 67% of 911 calls within 100 meters and 95% of calls within 300 meters. Wireless carriers that selected to use a handset-based technology were required to locate 67% of 911 calls within 50 meters and 95% of calls within 150 meters.
U-TDOA (Uplink Time Difference of Arrival) is a network-based technology that determines a cell phone’s location by comparing the times at which its signal reaches multiple cell towers, a process called multilateration. Since U-TDOA is network-based, no additional hardware or software needs to be installed into a cell phone, so it can accurately locate any mobile phone in any environment. In addition, U-TDOA is very accurate and extremely reliable.
A-GPS (Assisted GPS) is a handset-based technology, which uses the orbiting GPS satellites to locate cell phones. The assistance data speeds up the calculations and improves the time-to-first-fix of a GPS calculation. Although highly accurate, in order to provide a location, GPS requires a clear line-of-sight with the orbiting GPS satellites. This means that GPS is susceptible to failure in situations when a cell phone is indoors, particularly within building constructed of concrete and steel. In fact, even when a cell phone is outdoors, but it is surrounded by tall buildings, an “urban canyon” effect is created, and the signals are blocked by the concrete and steel. In summary, A-GPS has limited performance indoors and in cities with tall buildings.
New FCC proposed rules
Recently, the FCC became aware that A-GPS was experiencing difficulty locating E911 calls in indoors and dense-urban areas due to line-of-sight issues. Since the majority of 911 calls originate indoors and in major metropolitan areas with tall buildings, this is a major issue.
The FCC also came to the realization that the location performance being measured was not providing a clear picture. So, in July 2011, it released a Notice of Proposed Rulemaking addressing three areas.
The first tackled the issue of country-wide averaging, which is how the location performance was being calculated. Such a wide area of averaging masked how A-GPS was truly performing. For instance, A-GPS could be performing well in suburban or remote areas, but could be failing to locate any 911 calls originating in dense urban areas with tall buildings, which as stated, is where the majority of 911 calls are made. Using country-wide averaging, the wireless carriers using A-GPS as their 911 location solution were seen as being compliant. The FCC hopes that, by shrinking the geographic size of the sample that is being averaged, a more complete picture will be visible.
The second portion of the proposed rules covered simplifying the actual location performance requirements. As stated, there are currently two sets of accuracy requirements: one for network-based location techniques and one for handset-based location techniques. The FCC decided to drive toward one set of accuracy requirements, and selected the stricter requirement of 50 meters for 67% of the time and 150 meters for 95% of the time.
The third portion of the NPRM has to do with an indoor location requirement, which would mean that all wireless carriers would have to develop some way of locating wireless 911 calls originating indoors. To further examine the requirement for an indoor location rule, in September 2011, the FCC commissioned a special working group called CSRIC (Communications Security, Reliability, and Interoperability Council) to “review the existing set of CSRIC/NRIC 911 best practices and recommend ways to improve them, accounting for the passage of time, technology changes, and operational factors.” Assessing A-GPS functionality is one part of this working group’s nine-month-long review project, which is set to provide a final report and recommendations later in 2012.
A hybrid approach
Because U-TDOA can accurately and reliably locate mobile phones indoors, one option that is gaining momentum with wireless carriers is a hybrid approach that incorporates both technologies to increase overall effectiveness.
By combining A-GPS and U-TDOA technologies, wireless carriers can provide the most exact location possible. The protocol is that A-GPS would attempt first to get an accurate location fix, then fall back to U-TDOA if it is unsuccessful. That way, the caller would still be accurately located using U-TDOA.
Hybrid (A-GPS/U TDOA) location solutions currently exist that can accurately locate phones in any environment or under any condition. In fact, it is remarkable how complementary the two technologies are, since A-GPS works well in rural and remote areas, and U-TDOA excels in suburban and urban environments.
What is next?
Everyone is awaiting the results and recommendations from the CSRIC research. In the meantime, the need to locate 911 calls in places such indoors or in cities with tall buildings will not dissipate, and this need cannot be satisfied by A GPS alone. As a result, there could be a new FCC ruling in 2012 that could potentially pave the way for more better-performing hybrid location solutions, which combine A-GPS and U-TDOA technologies for locating wireless 911 calls.
In the end, all 911 callers in the United States should be able to expect to be located regardless of their environment, the type of phone they are using, or which wireless carrier they have selected. A hybrid A-GPS/U-TDOA location solution is the only way to ensure that first fix occurs in a timely manner, which – for some – could potentially be the difference between life and death.
With nearly 20 years in wireless and information technology, Brian Varano brings substantial management and marketing experience to TruePosition. Prior to joining TruePosition, Varano served as the head of marketing for Advanced Management Group. He has also served as the head of analyst relations for the Commerce Internet Division of Sterling Commerce, an IBM Company. Varano is a graduate of Villanova University, where he earned a Bachelor of Science degree in Marketing.
