Apple announced dozens of new features in iOS 8 and with the new iPhone 6 and 6 Plus at their media event on September 9th, but many of the smaller features were overlooked. Two of those features are Wi-Fi calling and VoLTE (Voice over LTE).

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VoLTE (Voice over LTE)

Voice over LTE in the simplest terms is a network technology that makes your calls clearer. It works similarly to VoIP (Voice over Internet Protocol) services like Skype, FaceTime, and Vonage. One of the main advantages to VoLTE is the dramatically improved call quality. The other main advantage is simultaneous voice and data. This isn’t a new feature to GSM customers (AT&T and T-Mobile in the U.S.), but it is for most CDMA customers (Verizon and Sprint in the U.S.). This technology allows you to be on a phone call, and continue using cellular data. For example, you can check the weather or post a photo to Facebook while you’re on the phone with someone. This was impossible with most CDMA phones in the past (including past Verizon and Sprint iPhones).

Not all carriers support VoLTE, and if they do, you might not know it since they all have different names for it. AT&T and T-Mobile call it HD Voice, Verizon calls it Advanced Calling 1.0, and Sprint doesn’t offer VoLTE at all.

T-Mobile was the first U.S. carrier to roll out VoLTE, starting in Seattle. They now offer it in 15 markets (Atlanta, Austin, Boston, Chicago, Dallas, Houston, Long Island, Los Angeles, Minneapolis, New Jersey, New York, Philadelphia, San Francisco, Seattle, and Washington DC.

Yesterday (September 16th), Verizon launched VoLTE on their network nationwide, which means, with a compatible device, VoLTE is available anywhere Verizon has LTE coverage.

AT&T currently offers VoLTE in four markets: Chicago, Milwaukee, Minneapolis, and St. Paul.

Sprint does not currently offer VoLTE, but they’ve announced they have plans to offer it sometime next year.

Below is a demonstration comparing AT&T’s HD Voice (VoLTE) to a standard voice call:

Advantages

  • Much clearer call quality compared to standard voice calls
  • Simultaneous voice and data (a new feature for CDMA customers)

Disadvantages

  • Requires phone and network support. Very few phones support VoLTE, and only Verizon offers VoLTE across their entire network
  • Requires you and the person you’re calling to have VoLTE capable phones
  • Both callers must be in VoLTE enabled areas (for Verizon, this is nationwide)
  • VoLTE calls do not work between carriers. If you have an AT&T VoLTE phone, you can’t make a VoLTE call to a Verizon customer with a VoLTE phone.
  • Reliability (at first) may be less than standard cell networks. When moving in between cell towers, the call may be more likely to drop in some cases. When moving from an LTE area to a 3G area, VoLTE calls may drop depending on the carrier.

 

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Wi-Fi Calling (GAN/UMA)

Wi-Fi Calling (Technically called Generic Access Network or Unlicensed Mobile Access), is a feature that allows you to make standard phone calls over Wi-Fi. This is done by routing the call traffic through your Wi-Fi connection, instead of over the air to a cell tower. This is useful in situations where you don’t have cell signal (a basement, subway station, or rural area) but you have Wi-Fi. You dial the number, and place the call just like you normally would. The only difference is, the call connects over Wi-Fi, and sounds much clearer.

T-Mobile was the first carrier to offer Wi-Fi calling, starting in 2007. They are the only carrier at launch to support Wi-Fi calling on the iPhone 6 and 6 Plus.

AT&T announced only a day after Apple’s September 9th event that they will be supporting Wi-Fi calling next year.

Sprint started offering Wi-Fi calling earlier this year on select Android phones. It is unclear if they plan to support the iPhone.

Verizon announced that they have no current plans to support Wi-Fi calling, saying their standard network coverage should be sufficient.  UPDATE: Verizon has now stated that they will support Wi-Fi calling sometime next year, but it has never been a top priority for them.

Advantages

  • Much clearer call quality compared to standard voice calls
  • Since the call is connected over Wi-Fi instead of the cell network, the load on the cell network is lightened as more people make Wi-Fi calls instead of using the cell towers.
  • When moving away from the Wi-Fi source (such as leaving your house and getting in the car), the call will switch automatically to a VoLTE call (if available).
  • Calls can now be made in areas with no cell towers, such as rural mountainous or desert areas, as long as there is Wi-Fi.
  • Calls can be made even over a slow, public Wi-Fi network.

Disadvantages

  • Requires phone and network support. Not all phones and carriers support Wi-Fi calling.
  • If no VoLTE is available, and you leave a Wi-Fi area, the Wi-Fi call won’t be able to transfer to the cell network, and the call will drop. Wi-Fi calls will only transfer to a VoLTE call if it’s available.
  • For the clearest quality call, both you and the other caller need to have a phone that supports Wi-Fi calling, and the phones need to be connected to Wi-Fi.