VoLTE Plus Wi-FiVoLTE Plus Wi-Fi

Calling over Wi-Fi delivers better call quality and reduced cell phone charges when using mobile devices.

Many employees use mobile phones to make and receive business calls even when they are working inside company offices. Inside many commercial buildings and in certain remote offices, cell network coverage is uneven, thereby producing poor call quality. It is much cheaper if those calls can be carried over Wi-Fi rather than paying for cellular minutes. Calling over Wi-Fi delivers better call quality and reduced cell phone charges.

Voice over Wi-Fi calling is a technology that allows cellular packets from the cell phone to be transferred to a carrier over the Internet. The call is injected back into the cellular network as if the call has been transmitted over the air. The proliferation of public Wi-Fi access points from libraries, coffee shops, airports, restaurants and many more, stimulates the use of voice calls over Wi-Fi networks connecting over the Internet.

An Interview with Curtis Peterson
Curtis Peterson has more than 20 years' experience managing information technology and carrier-scale data and packet voice communication networks. He has been a pioneer in VoIP services and has been developing, launching and operating Class 4 VoIP and customer-facing hosted PBX systems since 2002. Currently, he serves as the VP of Operations at RingCentral. RingCentral provides a cloud-based Enterprise class communications solution for voice, fax, text, Web meetings, and HD video conferencing without the need for a physical PBX in the office. It provides high quality reliable business communication services.

In a recent interview with Peterson, he replied to a series of questions relating to the combination of cell phones, VoLTE, and Wi-Fi networks:

What is VoLTE?
Voice over Long Term Evolution (VoLTE) helps carriers around the world to deliver a next-generation service architecture based on IP multimedia subsystem (IMS). All the communications are IP-based (packetized voice and data) which allows the carrier to offer the same services over mobile and fixed broadband.

How does VoLTE relate to the Wi-Fi networks?
Wi-Fi can be one of the access mechanisms using the VoLTE services. Calls over Wi-Fi do not use the carrier's cell network for access but use the local Wi-Fi network for access. The same set of services can be accessed by the user using Wi-Fi or a 4G/LTE access. The user does not encounter any differences whether on Wi-Fi or cell network access.

What is driving the adoption of VoLTE over Wi-Fi networks?
The ability accesses the same set of communication services through different transport technologies such as 4G/LTE and Wi-Fi. For VoLTE, the voice is completely packetized and IP-based. It uses latest sideband codecs such as Adaptive Multi-Rate Wideband (AMR-WB). AMR-WB delivers improved speech quality due to a wider speech bandwidth of 50 to 7000 Hz, about twice the bandwidth of a PSTN call.

Do you need an application for this?
VoLTE is based on 3GPP standard. As long as the voice client is based on the standard, it can use VoLTE. But most VoLTE providers may have specialized handsets such as iPhone and Android devices that they sell through distribution channels such as AT&T and Verizon.

What Device OSs are supported?
Android, iOS, and Windows phones are the leading devices that support VoLTE. VoLTE is an application running on these phones connecting to the carrier's IMS network.

Take me through a call passing through VoLTE and the Internet.
First the VoLTE phone connects to the wireless data network (Wi-Fi) through 4G/LTE. This assigns the device an IP address. After that, it uses SIP/RTP protocols to establish a call through the carrier's IMS network.

The call flow can be the same once the IP address is assigned to the device either through Wi-Fi or some other access mechanism. The main difference is that the voice packets flow through the public Internet infrastructure without any Quality of Service applied to it.

For VoLTE, it is dedicated network with QoS applied for voice traffic so that the user can expect better call quality end-to-end.

What are the business benefits?
For the carrier, compared to the existing mobile voice network where carriers use dedicated radio resources per call, using packetized voice helps them share the channel with other users. So the bandwidth usage is more effective and reduces the cost. There can be new services that can integrate packetized voice and data. For the users, it provides greater coverage for the services and also access to broader and richer set of services.

What are the consumer benefits?
Since VoLTE uses some of the latest codecs such as AMR-WB, customers get much better quality voice in addition to the general benefits of VoIP.

What are the barriers to broad implementation?
This is a big investment for the carrier, and it cannibalizes the existing GSM/CDMA-based voice infrastructure. It also involves huge initial capital investment to provide a scalable IMS solution.

There is no doubt that voice calls accessing the Internet and carrier networks will grow. The use of Wi-Fi access actually helps the existing cell carriers because the call does not cause congestion over the cell networks when placing a call.