NSN: VoLTE better than OTT VoIP for carriers, customers

Over-the-top (OTT) voice over IP services are increasingly popular among mobile customers, who consider them less-expensive alternatives to standard cellular voice. But these services have significant performance shortcomings in comparison to voice over LTE (VoLTE) offerings that mobile operators can provide, according to Nokia (NYSE:NOK) Solutions and Networks.

NSN Smart Labs VoLTE/VoIP

Tests showed OTT VoIP clients consumed more battery power than VoLTE clients. (Source: NSN Smart Labs)

NSN Smart Labs, which provides technical consulting to analyze interactions between smart devices, mobile operating systems, applications and mobile networks, came to this conclusion after testing OTT VoIP and VoLTE client groups against four defined key performance indicators (KPIs): smartphone battery consumption, data connections, data volume/throughput as well as signaling load.

The vendor's findings are likely to generate debate particularly as new OTT VoIP offerings hit the marketplace. For example, OTT messaging provider WhatsApp, which is being acquired by social networking giant Facebook in a $16 billion deal, recently announced that its application will begin providing VoIP this quarter.

In fact, Windows Phone Central reported that volunteers who handle Hindi language translation of WhatsApp for Windows Phone have already received new translation requests related to upcoming voice calling functionality. Those new strings address functions for hang up, incoming call and outgoing call.

According to a blog entry posted by Gerald Reddig, whose Twitter bio describes him as being in portfolio marketing management for NSN's mobile broadband business, NSN Smart Labs initially tested the voice quality of VoLTE and VoIP clients. Experiments revealed that VoLTE clients and OTT VoIP applications achieved a similar mean opinion score (MOS), which gives a numerical indication of the perceived quality of the media received after compression and transmission.

However, the VoLTE client exhibited up to 94 percent lower mouth-to-ear delay vs. OTT VoIP. Further, VoLTE consumed 40 percent less smartphone battery power to achieve this level of quality and required lower bit rates in general, Reddig said.

Overall data volume consumed over a period of time also impacted battery use. Including a mix of active and standby periods, VoLTE showed at least 50 percent lower consumption than OTT VoIP "thanks to its more efficient behavior during standby," Reddig said.

According to Reddig, NSN's testing also revealed that "typical default OTT VoIP keep-alive patterns activated during standby created between 100 percent and 200 percent higher signaling load on LTE networks compared with VoLTE."

The vendor noted that in one case, an OTT VoIP client caused up to 3,000 percent more signaling in the network during standby with default settings.

VoLTE clients also outperformed their OTT VoIP counterparts on the other measured KPIs. For example, OTT VoIP clients generated up to 10 times more data connections in the mobile network than a VoLTE client during a call. In addition, NSN found that OTT VoIP applications required between 20 percent and 40 percent more throughput than VoLTE clients during active calls.

However, that does not mean it is impossible for OTT VoIP providers to do better. One OTT VoIP application, which Reddig did not identify, "showed exceptional performance and came close to VoLTE" on the throughput KPI.

NSN Smart Labs concluded that not only are VoLTE clients are more "network friendly" than OTT VoIP, the power efficiency they provide enable a superior customer experience.

"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," Reddig said.

For more:
- see this NSN blog post
- see this Windows Phone Central article

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