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NG9-1-1: The Changing Face of Emergency Calling

Author: Jim Machi, Dialogic Corporation

Copyright: 9-1-1 Magazine, Feature Content

Date: 2011-10-03
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What public safety leaders need to know about how to make the move to Next Generation 9-1-1 services, and how best to take advantage of the benefits these services provide.

The FCC estimates that 70% of 9-1-1 calls are placed by wireless callers. Couple that with the increase in Voice Over IP (VoIP) phone services and you can quickly see that being able to fix a phone number with a specific location is nowhere near the majority of these calls anymore. Furthermore, the increased capabilities associated with these wireless and VoIP networks has led to the idea that we should use data, images and video to improve the effectiveness of transmitting a 9-1-1 “call” to a Public Safety Answering Point (PSAP).

That idea has been driven into fruition by the National Highway Traffic Safety Administration (NHTSA), under the U.S. Department of Transportation (DOT), who has developed the Next Generation 9-1-1 initiative (NG9-1-1). Through the initiative, the NHTSA is looking to incorporate these new technical capabilities and drive the marriage of them with existing PSAPs.  Yet being able to tie Emergency Services IP Networks (ESInets) to legacy networks, and ensuring that PSAPs can handle video, streaming, data, texting and voice, plus obtain the location of a mobile phone and/or a VoIP phone, is a potentially daunting task.  But with the right tools, it is possible. 

So what do public safety leaders need to know about how to make the move to next-generation 9-1-1 services?  And how can they best take advantage of the benefits these services provide?

Setting the Stage for the Future of Emergency Calling

9-1-1 services are not something to be taken lightly.  Channeling important calls through the network is critical to ensuring the safety of lives across the U.S.  With today’s emergency services, or E9-1-1 services, the public can only make emergency voice calls and Teletype calls. This means that only minimal data is delivered, including the Automatic Number Identification, which enables subscribers to display or capture the billing telephone number of a calling party, subscriber name and Automatic Location Identification, if available.

However, in the NG9-1-1 environment, the public will be able to make a wide range of emergency “calls,” including voice, text and video from any device – wired or wireless – over Internet Protocol (IP) networks.  In addition, PSAPs will be able to obtain data from personal safety devices like medical alert systems and sensors.    Not only do these services support a constantly increasing mobile user base, but they also support the deaf and hearing impaired, who frequently communicate via text message, as well as non-English speaking callers.

The National Emergency Number Association (NENA) understands the importance of emergency calling and is tracking the progression of 9-1-1 services within the U.S., and is setting the stage for the future of emergency calling. In fact, on June 16 NENA announced the approval of the i3 standard which explains, “how networks and devices will eventually work together to enable voice, text, picture, and data exchange between citizens and first responders.”  It is essentially a long-term plan to ensure that all public safety networks are successfully transitioned from legacy networks to next-generation IP networks to allow for the more advanced services like video, streaming, data, texting and voice communications. The protocol for delivering these “calls” across the ESInet will be the Session Initiation Protocol (SIP), or IP Multimedia Subsystem (IMS, which incorporates SIP).  The functional and interface standards developed by NENA describe general SIP and IMS-based architectures that allow responsible agencies flexibility in developing an infrastructure to support the envisioned features of NG9-1-1 calling.

As a result of the i3 standard, and NENA’s emphasis on the importance of transitioning legacy networks to IP, public safety agencies are on the move to make this transition. 

But with more than 6,000 PSAPs in the U.S., it goes without saying that transitioning every single PSAP from TDM to IP comes with its challenges.  Just how to make this transition has been an ongoing topic of debate, and budget is a primary concern.

However, if done correctly, the operational and fiscal advantages of NG9-1-1 networks will be significant.  In addition to offering new ways of communication for PSAPs and the general public, the new environment provides for much easier, much more effective call routing and transfers.

The goal for many PSAPs is to become part of a larger regional network, including other PSAPs, thereby reducing the cost and maintenance burden. This could take place in a physical or virtual manner – where several counties work together to consolidate their physical networks, or via virtual IP networks, counties could leverage resources to connect various emergency call centers.  This would lift the budget concerns, creating a more efficient and effective architecture – and reducing operational expenses. 


Making the Transition

There are two options for making the migration from TDM to IP.  Public safety agencies can choose to run two networks in parallel – a TDM and an IP network – until they do the final switchover.  However, this requires an extensive amount of hardware and as a result this option tends to be extremely expensive and less efficient. 

That being said, it is important that as public safety leaders make the transition, that they consider not just the replication of what their networks can accomplish today, but what their networks can accomplish in the future.  That way, as innovative, new services are introduced they can essentially build on their network rather than having to recreate it again in the future.  The key to this option is to implement the right network equipment that can support both TDM and IP services, so that they can complete today’s E9-1-1 services, while transitioning to new NG9-1-1 services – without having to rip and replace their network.

When PSAPs are looking at building on top of their existing network, there are a few key elements that they should look at within their network – those that can support both TDM and IP as they make the migration so that PSAPs can support emergency services now and in the future. 

Legacy Network Gateway (LNG)
The Legacy Network Gateway is a media gateway solution with additional 9-1-1 specific features that allows legacy, TDM-based carrier networks to access the emergency services available in the ESInet. 

Legacy PSAP Gateway (LPG)
The Legacy PSAP Gateway is a media gateway solution which provides similar features to the LNG, and is critical in providing protocol conversion from the NG9-1-1 ESInet to the E9-1-1 PSAP equipment. 

Emergency Services Routing Proxy (ESRP)
The ESRP is the base routing of function for emergency calls for NG9-1-1.  As needed, the ESRP queries the Emergency Call Routing Function (ECRF) for routing instructions and queries the PRF for applicable policy.  The ESRP forwards the modified SIP signaling to the appropriate node.  The ESRP is also used for calls originating in the PSAP that are bound for responders.  It is important to select equipment that supports the necessary recording and media anchoring requirements for the ESRP and the ability to deliver video services, as this will be key in the future of NG9-1-1 communications.

Border Control Function (BCF)
The Border Control Function provides a secure entry into the ESInet for emergency calls presented to the network.  It incorporates firewall and admission control, and may include anchoring of sessions and media as well as other security mechanisms to prevent deliberate or malicious attacks on PSAPs or other entities connected to the ESInet. 

Each of the functions described above are key to making the migration from E9-1-1 to NG9-1-1 without having to rip and replace an entire network.  They make it possible to tie ESInets to legacy networks to ensure PSAPs can handle video, streaming, data, texting and voice, obtaining the location of a mobile phone and/or a VoIP phone – taking the public safety industry to the next level. 


Summing it Up

While NG9-1-1 has been talked about for quite a long time, the passing of NENA’s i3 standard represented a significant step forward for the public safety industry.  Now more than ever, public safety leaders must be aware of the various ways to make the transition from E9-1-1 to NG9-1-1.  From incident notification to mass reporting and coordinating response, NG9-1-1 will only enhance the public safety of citizens throughout the U.S. and it is important that public safety leaders understand which core components of the network will enable them to do so – without breaking the bank.  Building on their existing network with equipment that supports both TDM and IP and therefore existing and future services, is clearly the best way to do so. 


Jim Machi is Senior Vice President of Marketing for Dialogic Corporation, responsible for developing marketing strategy and driving marketing communications for Dialogic.  He is also responsible for long term product planning and strategy for all Dialogic products.  Dialogic develops open systems based voice, video and signaling products targeted for both the enterprise and service provider market segments.  For more information see






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