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From LTE to Wi-Fi and back: Call Continuity brings the next generation of calling

Jan 5, 2015

Qualcomm products mentioned within this post are offered by Qualcomm Technologies, Inc. and/or its subsidiaries.

The telephone call is experiencing a revival of sorts, and it’s all happening in the realm of mobile technology. Phone calls are getting clearer thanks to HD Voice, which is available on >100 3G and 4G LTE mobile networks. They are increasingly transported using Internet Protocol (IP) packets, instead of the good old circuit-switched approach. And some mobile networks and smartphones are even offering video calling — from one mobile phone number to another, no extra apps required.

And then there’s Wi-Fi calling. Traditionally, phone calls were possible only over a 2G, 3G, or 4G LTE cellular network (the latter using VoLTE technology). More recently, some mobile operators have begun enabling calling over Wi-Fi networks as well.

But Wi-Fi calling came with two caveats. First, callers had to stay within range of the Wi-Fi network where their call started — otherwise the call would drop. Second, a call that started on the cellular network could not be switched to Wi-Fi mid-call. This created a dichotomy of user experience between Wi-Fi and cellular technologies like LTE, where the smartphone and the mobile network are designed to seamlessly hand-off a call from one cell tower to the next one, without dropping it, while the caller is on the move.

At Qualcomm® Technologies, we are setting out to bring LTE and Wi-Fi technologies together, to create better mobile experiences, and build stronger mobile networks. One feature that puts us on the path to realizing this vision is Call Continuity. It bridges over the dichotomy between the calling experiences on LTE and Wi-Fi.

The video above demonstrates Call Continuity in action. It demonstrates a real video call taking place over the Verizon Wireless XLTE network, using two Droid Maxx by Motorola smartphones, powered by Qualcomm® Snapdragon™ processors with integrated 4G LTE connectivity. Verizon Wireless, Motorola Mobility, and Qualcomm have recently worked together to update the Droid Maxx with support for Voice over LTE (VoLTE), HD Voice, and video calling with Call Continuity between LTE and Wi-Fi.

As the video shows, when connected to a mobile network that supports Call Continuity and if implemented by an OEM, a smartphone powered by an LTE capable Snapdragon processor is capable of  handling off the call from the LTE cell tower to a known Wi-Fi access point, or vice versa, without dropping it. To decide when to execute the switch, the LTE capable Snapdragon processor is designed to check the strength of the Wi-Fi signal — switching the call to Wi-Fi when it’s strong, and switching to LTE when it weakens. This addresses the two caveats of Wi-Fi calling discussed earlier.

Think about how useful this would be: you get the added coverage and convenience of Wi-Fi calling, with the freedom of mobility that you have come to associate with LTE. And while the demo showed Call Continuity for a video call, the technology applies to voice calls too.

Call Continuity is great for mobile network operators as well. It extends LTE calling coverage to known Wi-Fi access points. It allows mobile operators to offer new bandwidth-intensive video calling services, while offloading some of the added traffic to Wi-Fi. An additional benefit of Qualcomm’s implementation of Call Continuity is that it lets operators decide whether to offload voice calls, video calls, or both, to Wi-Fi networks — allowing operators to optimize for business and/or service quality objectives.

Call Continuity is just one way Snapdragon processors are bringing LTE and Wi-Fi together. As a leader in both LTE and Wi-Fi, Qualcomm will continue working on new ways to combine the strengths of LTE and Wi-Fi to give users a unified, superior wireless experience, and operators a new way of strengthening and extending the capabilities of their LTE networks.

Call Continuity feature depends on OEM and carrier selection.

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