Discussions on Next Generation 9-1-1 (NG9-1-1) often include the topic of location. Many aspects must be considered to ensure we’re all on the same page with regard to what location truly means. Much has changed since a 9-1-1 location primarily referred to fixed, wireline phone located at a residence or business. The increase in multi-line phone system, mobile device and Voice over Internet Protocol (VoIP) usage has made 9-1-1 location acquisition much more complex. In this article, we’ll review the basics of Enhanced 9-1-1 (E9-1-1) location, and issues currently creating confusion, which may continue with NG9-1-1 if not addressed.

9-1-1 location is used to route calls to the appropriate PSAP and assist in determining the correct agencies to dispatch. Location is either civic or geodetic. The civic location is a specific address. The geodetic location is a latitude and longitude, often referred to as XY coordinates. Civic addresses must be validated against the master street address guide (MSAG) before they’re entered into the ALI database and used to route a 9-1-1 call.

In NG9-1-1 systems, MSAG and ALI functions will be replaced by GIS databases and new functional elements called the location validation function (LVF) and location information server (LIS).

After an E9-1-1 call is routed to and answered at the PSAP, the phone number and location are displayed on the ALI screen. The ANI/ALI information is associated with a class of service (COS), designating the type of phone service making the call. COS has been key to helping calltakers identify the meaning behind the location information being displayed. But, COS’s effectiveness diminishes for wireless and broadband phone services.

Around the country, PSAPs have trained their personnel to make every attempt to verify the caller’s location before assuming the location on their ALI screen is accurate. However, it has been challenging because the inception of Wireless Phase I and II calls means that the address on the ALI screen may not in any way represent the caller’s real location. In many cases, PSAPs rely on COS as a tool that alerts a calltaker to this disparity and assists them in understanding what information is being displayed. Is this tool still adequate? In some cases, no. COS may not definitively classify the information being displayed on the ALI screen.

VoIP
VoIP devices can be fixed (associated to a specific registered address) or nomadic. Nomadic VoIP refers to a device that can be associated with multiple locations. A common example is a VoIP service that can be registered at a primary residence and updated via the Internet if, for example, the number’s owner is staying at a vacation home. Nomadic devices aren’t mobile and cannot update their registered location during a 9-1-1 call. The VoIP COS, however, doesn’t indicate whether or not the caller is using a fixed or nomadic device to make the 9-1-1 call.

Also, callers using a nomadic device that have moved from their registered address may neglect to update their location before calling 9-1-1. In these cases, an incorrect address will be displayed on ALI, and the call itself may be routed to the wrong PSAP.

Mobile/Wireless
Mobile access refers to calling devices, such as cell phones, that can move and update geographic location during a 9-1-1 call. Cell phone calls are carried over a cellular radio network that supports mobility as the user moves between cell towers and other service providers. Wireless 9-1-1 calls are routed according to the tower and sector being used to deliver the call—not the device’s location. For cell phone calls, COS commonly indicates if the call is Phase I or II.

As with VoIP, the COS used for wireless calls may not accurately describe what the calltaker is seeing on their ALI display. Often, wireless Phase I and II calls display a civic address that doesn’t correspond to a caller’s location. The civic address is associated with the cell tower that delivers the call. Except in rare cases, the civic address provided for wireless calls isn’t useful to the PSAP.

For a Phase 1 call, the civic address displayed may or may not be accompanied by XY coordinates. But, these coordinates don’t reflect the caller’s location, and COS doesn’t provide enough detail about what X and Y represent. The coordinates may be the tower’s physical location or the cell sector centroid’s location (the nominal center of the cell sector). The calltaker has no way to discern the difference without manually comparing the civic address to where the coordinates plot on a map.

Femtocells
Femtocells are low-power wireless base stations operating in the wireless carrier’s licensed spectrum to connect standard mobile devices to the carrier’s network using customer-provided IP broadband connections. A femtocell carries voice and data traffic by providing wireless coverage in a very small geographic area via a small unit located at the customer’s premise. Depending on the service provider, femtocells must be used at the registered civic address or in an area where it can acquire geodetic coordinates that are within the carrier’s licensed area. Few regions use a COS that is specific to femtocells. COS, therefore, may appear as a wireless or VoIP call.

With femtocells and similar devices, even with a specific COS, the information displayed on the ALI screen isn’t consistent between carriers. Some carriers display the femtocell’s registered civic address, while others display the civic address of the routing cell tower. There’s also inconsistency as to when, or if, an XY coordinate is displayed and whether or not it represents the femtocell’s location or other coordinates associated with Wireless Phase I or II information.

As technologies evolve and become more sophisticated and NG9-1-1 systems are implemented, we must be vigilant and realistic in our expectation that 9-1-1 location be defined and provided in a way that is useful to PSAPs. Vague or inconsistent location information isn’t acceptable. 9-1-1 location must be provided via standardized methodologies that don’t leave room for assumption and error. PSAPs and 9-1-1 authorities must maintain an open dialogue with vendors to ensure these issues are understood.

About the Author
Kathy McMahon is technical service manager for APCO International. Contact her via e-mail at mcmahonk@apcointl.org.

Originally published in Public Safety Communications magazine, Vol. 77(5):22-23, May 2011.