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911 Access

NextGen 911 webinar Q&A responses

Thomas Ginter Thomas Ginter
Thomas Ginter

On December 12, we hosted a webinar on NextGen 911 – What Every Service Provider Needs to Know.  Watch the webinar recording here.  Please find below the answers to the questions asked during the webinar.

Question 1: Can I use LAT/LONG or IP based geo location to send that through in real-time?

Answer: The current NENA i3 specification supports both Latitude/Longitude and address location objects.

Question 2: If the VoIP subscriber has changed locations from the information data filled in the LIS and VPC how is the key and location determined?

Answer: If the implementation is NENA i2, then the existing address populated in the LIS is utilized. To use a different address requires an updated provisioning transaction to take place with the LIS. For a NENA i3 implementation; however, any valid location object can be used dynamically at call time.

Question 3: Do these VoIP treatments apply to Fixed Wireless?

Answer: Fixed Wireless does not use the VOIP i2 technique. Rather, the call is placed as a Wireless Phase II call where latitude and longitude are provided to public safety. Some wireless carriers are implementing an enhancement where a civic address is also retained for the subscriber and if the latitude and longitude of the fixed wireless call is in the vicinity of the civic address location, then the civic address information may be sent to public safety.

Question 4: When does i3 take affect and how will the plethora of call centers transition to all VoIP?

Answer: Next Gen 911 network deployment decisions rest principally at the state or county level. This means that there is no clearly established national schedule for deployment and each state and county manages its own time-table.

Question 5: How will the geo data get into the call? Will there be software on a mobile phone that takes the phone’s GPS data and adds to the SIP INVITE headers?

Answer: There will be many implementations and you have described one. As long as the Location Object is added to the SIP INVITE prior to the SIP INVITE being sent to the public safety network, it will be treated as “i3” by the public safety network.

Question 6: It’s been said that NG911 would have video capability, for example for the PSAP operator to see something if they need/the caller to show something if they need, etc.  Can you explain how that is supposed to work?  And secondly, how that is expected to work with Deaf/HoH callers.  I’m from the Video Relay Service industry, and it’s not clear how the SIP/RTP “plumbing” is supposed to connect to the PSAP.

Answer: There are several aspects to this question:

  • In a fully end-to-end i3 deployment, video will be possible. The SIP protocol is used to establish an end-to-end session followed by the exchange of any media that the users of the session can support. Today, the only media sent from the session originator (for example: a CLEC or Wireless Carrier) is voice or text. For video to work, the CLEC must support the sending of video as content in a 911 call, also the PSAP that receives the call will have to have i3 compliant equipment that can display video. Lastly, the intervening network must not have any constraint (such as an intervening legacy (TDM) Selective Router that limits the media (video) being exchanged.
  • For clarity, the “SIP/RTP plumbing” between the Originating Service Provider (for example: a CLEC or Wireless Carrier) and the PSAP is referred to as an Emergency Services Intranet (ESInet) and could be the subject of an entire webinar in itself.
  • For the Deaf/HoH caller, if all end-to-end devices and systems were i3 enabled, then 911 video should flow as simply as in other commercial video communications products. However, the industry is far from that ability in its current state of deployment. The use of Video Relay services are not likely to be replaced except on a very local basis where enterprising collaborations between communications providers, innovators, Deaf/HoH advocates and goal-driven public safety officials are made.

Question 7:How long is the process for adding address ranges?

Answer: The MSAG Address Directory for any address-range belongs to a state or municipal authority. They are responsible for updating the MSAG Directory and making it available for use.  Thus, this question really needs to be directed to the particular state or municipal authority.

Question 8: What is the difference between LIS and ALI

Answer: The ALI and LIS are both defined by separate and functionally different NENA specifications and data format definitions.  At a high level, an ALI is a “reverse white pages” database where a telephone number can be looked up to identify the associated subscriber name and their address in legacy “tabular” formats with rigid field sizes. A LIS can be thought of as a more modern database containing all the ALI information, and more in a flexible format.  The NENA i2 description of a LIS is:

“A Location Information Server (LIS) is a functional entity that provides locations of endpoints. A LIS can provide Location-by-Reference, or Location-by-Value, and, if the latter, in geo or civic forms. A LIS can be queried by an endpoint for its own location, or by another entity for the location of an endpoint. In either case, the LIS receives a unique identifier that represents the endpoint, for example an IP address, circuit-ID or Media Access Control (MAC) address, and returns the location (value or reference) associated with that identifier. The LIS is also the entity that provides the dereferencing service. “

Question 9:   Locating a wireless device may take several seconds – for example, GPS-based techniques can take up to 15 seconds for satellite acquisition and position determination. Would this not affect the latency of the call setup procedure?

Answer: Yes, and for this reason wireless mobile 911 has utilized the location of the serving cell tower’s location for determining the PSAP to which to initially route the call. The drawback is that a cell tower can serve across PSAP jurisdiction lines so mis-routes are not possible, but frequent on such towers. There are many location determination technologies, not just GPS, that are utilized within both Wireless 911 and VOIP 911.