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Which is better, VoIP or VoLTE? A reality check

By Gerald Reddig on Thu 3 July, 2014

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

A little while ago, Nokia Smart Labs tested the performance of operator Voice over LTE (VoLTE) against over-the-top (OTT) Voice over IP (VoIP) services. The results showed that OTT VoIP achieved similar call quality to VoLTE, but required higher bit rates and led to shorter device battery life. OTT VoIP also performed poorly when it came to signaling, data volume and data connections.

VoIP 1

These tests, however, were conducted under ideal radio conditions with no network load. The Smart Labs team was curious what the results would be with a more realistic scenario.

To find out, the team tested both services again – but this time placed the system under various non-Guaranteed Bit Rate (GBR) loads, including best-effort services such as file downloads, e-mail and Internet browsing, and with poor radio conditions.

It turns out that VoLTE voice quality is not affected at all by non-GBR traffic thanks to Quality of Service (QoS) configuration, so VoLTE voice quality was kept at a good level.

And what about OTT VoIP? Here the story was very different. Under low to medium load conditions, OTT VoIP degraded from 20 to 30%, giving a medium MOS* result which translates into poor to very poor quality. Under high network load, the MOS result was low which means the voice quality was completely unacceptable.

Even worse, the OTT VoIP service experienced a 100% call drop rate under very high non-GBR load and 65% under medium load. In contrast, the VoLTE drop call rate was always zero.

VoIP 2

When it came to battery consumption, OTT VoIP’s current consumption was 30 to 50% higher than VoLTE in the analyzed scenarios. In the real world, these tests show that subscribers can rely on VoLTE for their voice calls far more than they can with OTT VoIP services. We all know how frustrating dropped calls, crackly lines and dead smartphone batteries are – and who wants any of that?!

Click here for more information on Nokia’s VoLTE portfolio.

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

* The mean opinion score (MOS) scales from 1 to 5 and indicates the transmission quality of voice and video applications over a network. Here, the Perceptual Objective Listening Quality Assessment (POLQA) Super Wide Band (SWB) standard was used.

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  1. Madhup Sharma Thu 3 July, 2014

    Good learning , here one thought to check: what about reverse affect, meaning during voice call, what is affect on data rates/QOS?

    • Gerald Reddig Mon 7 July, 2014

      Hi Madhup Sharma,

      I assume you mean during voice call, what’s the impact to parallel services running on the UE?

      For LTE, it is defined GBR/MBR (max bit rate) for GBR bearers (QCI1 for VoLTE traffic). In addition, the UE-AMBR (Aggregated maximum bit rate at UE subscription level) and APN-AMBR (Aggregated maximum bit rate at APN level) are defined for non-GBR traffic (whatever other traffic the UE is carrying over default or dedicated non-GBR bearers).

      AMBR and GBR/MBR are independent, therefore running VoLTE call (GBR) should not have an effect on other non-GBR traffic carried by the UE.

      In case of OTT VoIP, all traffic is carried over default radio bearer as non-GBR traffic, so resources are shared amongst services.

      Hope that helps to understand the benefit of VoLTE in LTE networks better.

      Best regards
      Gerald Reddig

  2. Paweł W. Fri 4 July, 2014

    I think it’s quite obvious considering the fact that VoLTE is the GBR traffic (and higher QoS priority) and VoIP is non-GBR traffic with the lowest priority.

  3. Mosip Fri 11 July, 2014

    VOIP is one of the advanced technologies in communication field and the popularity of this service is increasing day by day.

  4. Vladimir Borcic Wed 6 August, 2014

    Very interesting and important analysis! Although the results could be expected, it is always needed to confirm it with field-measured values in order to understand the real impact in the end-user experience.
    I just wanted to add some other relevant issues that shall always be kept in mind when we compare VoLTE with OTT:
    1) OTT VoIP service is just another PS data service and most of the devices will just stop it if there is some incoming CS voice call. This will never happen with VoLTE established call.
    2) VoLTE has defined very reliable method for service continuity in case of loss of 4G coverage (SR-VCC). Another interesting test would be to compare VoLTE and OTT in a mixed 4G/3G area.
    3) Although OTT VoIP service is considered free-of-charge, it is really not so cheap if we consider the PS Data charging. On the contrary, any VoLTE operator will surely exclude the PS charging for VoLTE related traffic and voice/video sessions will only be charged based on contracted rates.
    4) VoLTE is really global service, while each OTT VoIP service is another community that you must belong if you want to benefit from free-of-charge services.
    5) Trusted relationship with your VoLTE operator is far much higher than it may ever be with any OTT VoIP operator.
    6) VoLTE operator provides all the regulatory services (emergency calls, number portability, fraud control, lawful interception)

    We may also talk about the advantages of security of VoLTE connection, roaming issues, integration with convergent and/or corporate solutions and other multimedia services.

    Best regards