Tag Archives: E911 deployment

T-Mobile’s VoIP 9-1-1 Strategy

Yesterday, my T-Mobile home page included a link to their page titled Wi-Fi Calling and 9-1-1 Address. This describes their method of providing 911 caller geo-location information when using a T-Mobile phone that’s connected via a Wi-Fi access point. [“Wi-Fi Calling” is their tradename for VoIP (Voice over Internet Protocol).]

Like their cellular phone 9-1-1 location strategy, it doesn’t rely on the caller phone’s GPS receiver. Also like their cellular geo-location strategy, it tries the most precise method first, and falls back to progressively less precise methods. I guess that the other U.S. cellular companies employ a similar VoIP 9-1-1 strategy.

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© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

Mobile phone E-911 deployment

On their mobile homepage, T-Mobile recently linked to T-Mobile’s 911 geolocation commitment document. Locating landline phones during a 911 call is easy: each landline phone number is associated with a geographic location, so the 911 operator can quickly dispatch help to the correct location.

Landline or not, you should ensure that the correct location is associated with your phone number. Check with your phone service provider. Most provide a private webpage with street address form that’s accessible from your account. Having the correct location on file could save your life.

Click to enlarge

9-1-1 System (click to enlarge) · illustration by Evan Mason

Mobile phones complicate this system, because they’re, well, mobile. Enhanced 9-1-1 Phase I service identifies the caller’s cell-site and sector, which provides a general location to the 911 operator. Enhanced 9-1-1 Phase II service provides more precise location information to the 911 operator. T-Mobile explains,

Since early 2004, T-Mobile has been deploying a network-based Phase II solution. . . T-Mobile’s solution is referred to as U-TDOA, Uplink-Time Difference of Arrival. U-TDOA does not require customers to purchase a new handset. [It also does not require that the phone contain a GPS receiver and is accurate to within about 150 feet. -RB].

VoIP (Voice over Internet Protocol) phones, because of their mobility, present similar geo-location obstacles during a 911 call.

Next Generation 9-1-1

The next generation 9-1-1 system (NG9-1-1) will allow “calls” to be initiated by any Internet-connected device. Calls for help may contain text, pictures, or video. Crashed vehicles will initiate “calls” and send crash data to 9-1-1 centers [also known as Public Safety Answering Points (PSAPs)] without human intervention.

Visit my website: http://russbellew.com
© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695