Making ‘911’ Calls in California

Posted by: AT&T Blog Team on September 9, 2013 at 4:23 pm

By Joe Marx, AT&T Assistant Vice President of Federal Regulatory

Last month, the California chapter of the National Emergency Number Association (CalNENA) sent a letter to the FCC intending to highlight an industry issue regarding ‘911’ wireless location accuracy. The letter says that a high percentage of wireless calls are being delivered to several public safety answering points (PSAPs) in California without enhanced 911 (E911) Phase II location Information. CalNENA included several charts that purportedly illustrate the frequency upon which 911 calls lack this information. However, the real lack of information is in the letter itself.

AT&T takes public safety issues very seriously and we are continuing to work closely with CalNENA and the FCC on this issue. Our goal is to ensure that public safety can take advantage of accurate location estimates that we provide. Despite some of CalNENA’s assertions, there is no public safety crisis in California – 911 wireless service works and California’s residents and visitors are being protected by PSAPs and first responders across the state. What CalNENA’s letter actually demonstrates is that many PSAPs fail to request Phase II location information from wireless carriers for 911 calls.

Previously, AT&T 911 location estimates were derived using a network-based location technology. While this technology rapidly provided location estimates, it was criticized by public safety as less accurate than estimates produced by Assisted Global Positioning Systems (AGPS) technology. In part based on this constructive criticism from the public safety community, AT&T decided to deploy AGPS in its 3G and 4G networks.

The adoption of AGPS technology for improved 911 accuracy meant that the time needed to calculate and provide the initial location estimate would increase significantly when compared to network location technology. This delay is similar in nature to the delay that users of personal GPS navigational devices experience when turning on their device. GPS receivers in the navigation device or in a smartphone require time to achieve a satellite “lock” with the GPS satellites. In the case of network versus AGPS 911 location estimates, this delay means that the location data, while more accurate, is no longer delivered to the PSAP concurrently with 911 call delivery as it formerly was with network-based location technology.

As a result of moving to AGPS, location information may not be available to the PSAP for 911 calls when the call is initially received at the PSAP, or may not be available at all for very short calls. This is one of the flaws of the CalNENA data collection efforts, as they did not filter out short calls of less than 30 seconds, which significantly skewed the results. For most 911 calls made with AGPS location technology, PSAPs will likely need to rebid, or request the system to provide updated location information, since location data often is not available when the 911 call first arrives. If the PSAP doesn’t rebid, then the more accurate AGPS location information may not be reviewed by the PSAP during or by the end of the 911 call, even though it is available to the PSAP in the 911 system.

For its part, AT&T not only uses accuracy drive test results to measure compliance with the FCC’s location accuracy rules, but it also keeps track of how often our systems can determine a location for all live 911 calls. This data is called Location Success Rate (or yield), and for the counties referred to in the CalNENA letter, our Location Success Rate is greater than 99%. So, for more than 99% of 911 calls made in these counties, there is location information available for PSAPs to retrieve and review.

The situation in California is an important one and we need to work together to identify and address the correct problem. We believe that current AGPS technology can’t produce location estimates much faster than it does today. Additional work therefore is needed to make sure that this location data, which is available to the PSAP, is actually retrieved and reviewed (if needed) during a 911 call. As an active participant in the FCC’s Communications Security, Reliability, and Interoperability Council (CSRIC) working groups on 911 location accuracy, we think that the FCC should use the CSRIC, or a separate workshop, to begin analyzing the issue.

Working together with the public safety community and the industry, we can optimize today’s technology and strive for improved performance in the future.

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