November 2, 2011 Wednesday 8:38 PM EST, Targeted News Service

WASHINGTON–Changing call patterns including increased traffic on wireless networks have led to higher risks of overloading 911 systems during weather or other emergencies, resulting in abandoned or unanswered calls, according to a new ATIS report. The association’s Network Reliability Steering Committee (NRSC) made several recommendations to both telecommunications service providers and Public Safety Answering Points (PSAPs) for improvements to reduce 911 outages.

The Federal Communications Commission asked ATIS in May to review why certain trunk lines serving PSAPs were being removed from service during heavy calling volumes. The NRSC completed its analysis with the publication of the 911 CAMA Trunk Throughput Optimization Analysis (ATIS-0100034) report.

“We appreciate the hard work of the NRSC on the 911 CAMA trunk overload issue,” said John Healy, Chief Statistician of the FCC’s Public Safety and Homeland Security Bureau. “Our collaboration should help prevent major 911 outages in the future and is a major step in improving the overall reliability of 911 networks.”

PSAPs receive emergency calls and, at times of heavy volumes, “wink” failures can occur between service providers’ selective routers and PSAPs that temporarily disrupt trunk lines. A wink is a short signal carried over the network at the beginning and end of calls. During a high call volume overload to 911, the time needed for the PSAP’s customer premise equipment to be ready for the next 911 call can exceed the maximum call setup time resulting in the PSAP’s equipment not providing a wink.

If all the other trunks remain busy, as is often the case during a heavy call volume event, the same call will again be offered to the same trunk. If this second offering results in a no-wink condition, the selective router trunk will be taken out of service in what’s known as a double wink failure. This could lead to a cascading effect that takes several or all trunk lines connected to local PSAPs out of service, which happened during an East Coast blizzard in January 2011.

“911 communications links are vital, particularly during emergencies,” said Susan Miller, ATIS’ President and CEO. “There are important steps that service providers and PSAPs can take to prevent emergency communications networks from becoming overloaded and failing. ATIS’ report outlines such steps, and I hope they can be put into place quickly to facilitate the flow of emergency communications.”

ATIS’ report developed multiple recommendations to prevent these types of outages, including:

Service providers modifying their selective routers to prevent complete trunk groups from going out of service due to double wink failures.

PSAPs and service providers working together to develop overflow routing to backup PSAPs during high call volumes.

Increased communications between service providers and PSAPs during high volume periods to minimize impact.

Updated procedures that would allow PSAPs to handle more calls during high volume periods. This could include employing more call-takers during expected weather emergencies or shifting focus to handling as many calls as possible rather than returning calls during these volume periods.

“NRSC member companies’ quick and diligent response to this industry-wide 911 issue was commendable,” said Robin Howard, Director – National Network Operations at Verizon Communications, and NRSC Co-Chair and Team Lead for the project. “This ATIS Standard will provide guidance for all service providers and public service answering points in maximizing 911 calls reaching emergency call takers during periods of high call volume.”

ATIS will hold a webinar entitled “Optimizing 911 CAMA Trunk Throughput” on November 3rd at 1:00 p.m. to discuss the report. Speakers will include John Healy, Chief Statistician of the FCC’s Public Safety and Homeland Security Bureau, and ATIS members Stacy Hartman, Director, Federal Policy at CenturyLink, and Robin Howard, Director, National Network Operations at Verizon Communications. The 911 CAMA Trunk Throughput Optimization Analysis (ATIS-0100034) report is available at the ATIS Document Store via the following link: http://www.atis.org/docstore/default.aspx.

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