This guest blog post was written by Kai Ojala, CTO, Anite Network Testing

The requirement for VoLTE is to offer high-quality voice calls and video calls, which as a baseline requires wide LTE coverage. LTE networks fulfill this aspect – especially lower carrier frequencies are deployed globally (e.g. 700 and 800 MHz frequency bands). Operators will benefit from customers switching to VoLTE services by harmonizing voice services and getting better capacity out of the spectrum.
Voice calls in LTE networks can be handled using Circuit Switched Fallback (CSFB) and Voice over LTE (VoLTE). CSFB provides a mechanism to transfer an initiated voice call to legacy circuit-switched networks. VoLTE, on the other hand, is a fully packet switched technology which uses Voice over IP (VoIP) technologies. With the SR-VCC functionality voice calls made with VoLTE can be switched over to legacy networks when the user moves out of the LTE network coverage.

VoLTE is expected to offer operators a chance to produce better service quality compared to OTT (Over-the-Top, such as Skype, GTalk) competitors. For the operators, the advantage of VoLTE is that OTT services cannot secure the quality of the service (QoS). The quality of the OTT service depends solely on the quality of the packet data services the operators offer. On the other hand, OTT services are challenging VoLTE, as these services are usually free of charge for the end-user. They require a good and reliable packet data connection to function which will be available when good coverage and quality with LTE is offered (also enabling VoLTE services).
There are two sides to the VoLTE service, the implementations in the device and the implementations in the network. In the Note4 volte02radio network side we have the IMS core that has to work with the IMS client on the device. Complexity is brought by the existence of several vendors both on the network and the device side. This brings us to a state where various IMS vendors have their own specific implementation of the IMS client. Qualcomm, Samsung, and LG each of them have their own IMS client in the terminal.
What can we measure of VoLTE

Note4 volte01Anite Nemo tools can track a number of different VoLTE parameters. Customers can record SIP signaling in real-time and RTP data statistics, such as RTP jitter and Packet loss. The VoLTE measurements products further support call statistics, such as call set up time, call success rates, call failures, and SRVCC statistics. These KPIs reflect how fluently end-users can use and how reliably services are offered. For voice quality measurements the products support POLQA which reflects directly the quality of the end-user experience of audio during a VoLTE call.
While testing VoLTE, it is good to understand that IMS and VoLTE configurations on devices and networks vary.  VoLTE trials, testing, and optimization have been ongoing for a while now, and still VoLTE services are in the early stages of commercialization.
Anite Network Testing has successfully tested VoLTE on multiple devices

We at Anite Network Testing are able to provide the needed field test, benchmarking, and in-building measurement tools as well as data analysis platforms to successfully test VoLTE and thus help our customers to successfully launch the service and speed up their time-to-market for their latest network investment. Currently we support VoLTE testing with all our products (e.g. Nemo Outdoor, Nemo Invex II, Nemo Handy, and Nemo Walker Air) and VoLTE analysis in our post processing tools Nemo Analyze, Nemo WindCatcher, and Nemo Xynergy.

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