WiFi calling to 911: Testing Results and Implications

December 15, 2015

Todd Piett

Recently, mobile carriers began enabling Voice over Internet Protocol (VoIP) calling on specific devices, where the device is connected to a Wi-Fi access point. Such VoIP calls are placed from the phone’s native dialer, yet are completed over Wi-Fi rather than the carrier’s traditional mobile phone network. Of the “Big 4” TMobile was an early adopter, followed quickly by Sprint and then ATT and Verizon. Each of the carriers has taken a slightly different route to enabling devices on their networks, turning it on different operating systems and specific handsets, but the net results is the same: an increasing portion of calls are being off-loaded from the carriers networks to VoIP. This obviously has benefits to the carriers in reducing costs and load on their networks, but also has significant implications (and benefits) to public safety especially as the number of devices supporting WiFi calling rapidly increases.

Rave Mobile Safety recently worked with select clients to determine what affect mobile VoIP calling to 9-1-1 has on the experience of the 9-1-1 caller and Public Safety Answering Point (PSAP) staff. While not exhaustive, and we continue to refine the testing scenarios, the initial results and some potential implications are listed below.

Initial Findings

• This limited testing demonstrated mobile VoIP 9-1-1 calls to be similar to 9-1-1 calls placed over the carrier’s traditional mobile network. While some variances were identified, none of the variances appear to have impeded the 9-1-1 caller’s ability to communicate with PSAP personnel, nor did the variances appear to degrade the information available to the PSAP.
• Devices seamlessly move to WiFi/Voip without any action from the caller when the connection to the carrier network is degraded (the exact definition of “degraded” seems to vary per carrier but in each instance was seamless). Once enabled on a device, Wi-Fi calls are placed through the phone’s native phone dialer; no additional “apps” need to be installed, nor is the end-user actively involved in selecting which network (carrier mobile or local Wi-Fi) is used to complete a given call. There was no additional call set up time or manually processes required.
• On some carriers, calls are routed as a wireless class of service and on others they are routed as VOIP class of service
• When completed to the PSAP, all calls were accompanied by ANI data which correctly identified the device placing the 9-1-1 call and provided call back information and the caller location. On some calls, the ALI was accompanied by the address pre-registered with the mobile Wi-Fi service, in addition to an estimated location.
• Where attempted, the 9-1-1 call did not interfere with the calling device’s ability to receive an SMS message sent through one of Rave Mobile Safety’s SMS Short Codes
• The location information provided by the caller was accurate, although more testing needs to be done in adverse indoor locations or areas where caller location information is known to be poor.

The implications

From the perspective of public safety, the benefit of Wi-Fi calling includes support for mobile 9-1-1 calls from locations where there has traditionally been poor carrier mobile network coverage (including indoors). This works natively without any change to user behavior (e.g. use of a special app) and does not require any change to existing PSAP operations or training.

Because the class of service was handled differently than traditional wireless calls in some cases, there is a significant potential impact on secondary PSAPs. In some regions, staffing is designed around a primary PSAP triaging mobile calls and then transferring as need be to local or secondary PSAP (e.g. most of the state of Massachusetts operates under this model). Because more wireless calls will be routed as VOIP, they will go directly to the secondary PSAPs, increasing their call volumes (potentially significantly).

Because the phones did not go into “emergency mode”, the devices were actually able to perform data functions that are some times locked out when a caller is dialing over the usual mobile networks.  For example, call takers can communicate via text with the callers (this is a feature of Smart911) and even share photos or videos back and forth (e.g. picture of patients wound or nearby landmark).

While most calls are handled effectively by the existing mobile networks, it is fantastic to see the carriers improve the ability for callers to communicate with 911 even in places where poor mobile network coverage may exist. WiFi calling also works exactly the way consumers expect it to – they simply dial 9-1-1 and the call is answered by the nearest PSAP, without any need for special steps or a custom app. Where Smart911 is installed, the additional features enabled by Smart911 also work seamlessly with WiFi calling – providing call takers additional information on the caller and enabling text based communications with callers who are unable to verbally communicate. We applaud the carriers for what seems to be a well thought out and beneficial implementation!

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