9-1-1 Access

NextGen 9-1-1 webinar Q&A responses

Thomas Ginter
Thomas Ginter
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On December 12, we hosted a webinar on NextGen 9-1-1 – 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 9-1-1 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:


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 9-1-1 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 9-1-1 and VOIP 9-1-1.