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Why operator VoLTE beats OTT VoIP

This blog is by Gerald Reddig from Nokia Solutions and Networks.Twitter: @GeraldReddig

Tests by NSN Smart Labs show that some over-the-top (OTT) Voice over IP (VoIP) services eat up 40% more smartphone battery power than Voice over LTE (VoLTE) from mobile operators.


Many OTT players are becoming increasingly active in the mobile voice service market. WhatsApp, for example, recently announced that its application will soon be providing a VoIP service. Meanwhile, many mobile operators are preparing for their networks and tariff plans to move from circuit switched voice to VoIP, to benefit from the growing number of VoLTE clients.


What are the differences and who comes out top?

NSN Smart Labs recently tested both client groups, OTT VoIP and VoLTE, against four defined Key Performance Indicators (KPIs). The following KPIs were based on specific traffic profiles to reveal a clear picture of how the applications and services affect the customer experience and network performance for mobile operators:

1.Smartphone battery consumption

2.Data connections

3.Data volume / throughput

4.Signaling load

Voice quality was measured using standardized Mean Opinion Score (MOS) methodology, which gives a numerical indication of the perceived quality of the media received after compression and transmission.

The tests showed that VoLTE clients and OTT VoIP applications achieved a similar MOS*, but OTT VoIP consumed significantly more smartphone battery power to achieve this level of quality and required higher bit rates in general. All the measured MOS values were significantly better than a reference 3G circuit switched voice call. Another important factor in terms of customer experience was the mouth-to-ear delay. The VoLTE client exhibited up to 94% lower mouth- to-ear delay compared to OTT VoIP.

And the winner is …

The KPIs demonstrated that the best measurement results came from the VoLTE clients.


1.Smartphone battery use

VoLTE clients consumed approximately 40% less than OTT VoIP clients.

2.Data connections

OTT VoIP clients generated up to 10x more data connections in the mobile network than a VoLTE client during a call.

3.Data volume/throughput

Most OTT VoIP applications required between 20% and 40% more throughput than VoLTE clients during active calls to achieve this quality level, although one OTT VoIP application showed exceptional performance and came close to VoLTE. Overall data volume consumed over a period of time, including a mix of active and stand-by periods, resulted in at least 50% lower consumption for VoLTE thanks to its more efficient behavior during stand-by.

4.Signaling load

Typical default OTT VoIP keep-alive patterns activated during standby created between 100% and 200% higher signaling load on LTE networks compared with VoLTE. In one case, an un-optimized OTT VoIP client caused up to 3,000% more signaling in the network during stand-by with default settings.


The tests reveal a clear winner –VoLTE clients are more network friendly than OTT VoIP, and provide a superior customer experience with respect to power efficiency.  Furthermore, VoLTE features that ensure Quality of Service (QoS) bring even greater benefits for users, especially in highly loaded networks, where voice quality is likely to break down for VoIP services.

With VoLTE, mobile operators have a powerful tool to compete with the OTT players.

Click here for more information about NSN’s VoLTE portfolio.

To share your thoughts on the topic, join the discussion with @NSNtweets using #NSNperformance #VoLTE #LTE #NSNSmartLabs #Signaling.

*Mean Opinion Score (MOS) – Perceptual Objective Listening Quality Assessment (POLQA) Super Wide Band (SWB) standard was used

Gerald Reddig

About Gerald Reddig

Gerald leads the global portfolio marketing efforts for Nokia’s security solutions. He is a member of the broadband forum, directs Nokia´s membership in the IoT Cybersecurity Alliance and steers Nokia´s Security center in Finland. Gerald is on the speaker’s circuit at international conferences and a recognized author on the topics he’s passionate about: cybersecurity technology, data privacy and finding the right solutions to prevent vulnerabilities, hacker trojans or man-in-the-middle attacks.

Tweet me at @geraldreddig

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