So there we go, first mobile network operators in the US and Korea have officially announced that they will start VoLTE (Voice over LTE) service with the Samsung Galaxy III shortly. Sounds interesting, but I've been using Skype on 3G for years now which is also Voice over IP and it has worked quite well. So what's so special when mobile network operators are doing it, too now? Some thoughts:
The QoS question: For Skype calls Quality of Service mechanisms in the radio network can't be used because Skype has way of interacting with the RAN. Network operator deployed VoLTE on the other hand can instruct the radio network to prioritize those packets and to not repeat data packets over the air interface for the voice data flow because the repeated packets would come too late anyway. This is all not necessary when radio conditions are good but could enhance the experience in border areas between cells where capacity is at a premium.
But that's pretty much it. Perhaps the client is more fully integrated into the overall phone functionality of the phone compared to Skype but that remains to be seen once the phone is launched.
And here are some thoughts on things that might not be so well early on: I wonder how call drop rates and call setup success rates will compare to the current voice service. Both values are extremely good in well designed networks and I wonder if VoLTE in early years with networks still in deployment and likely being deployed without fallback to a 2G network will come anywhere close.
Higher power consumption? Current voice telephony is handled entirely in the baseband and is optimized for power. VoLTE will likely use both the baseband and the application processor and includes the overhead for the full IP stack. In other words, it's likely that the phone will get warm and the battery empty quite quickly. Perhaps I'm the pessimist here, but that remains to be seen as well.
And finally it's going to be interesting to hear how good the sound quality is, but please not only tests while the mobile is stationary to compare the soft client's voice optimization to hardware background noise cancellation and other tricks today performed for circuit switched calls. The other really interesting thing to observe is what happens with voice quality during handovers between cells when the data flow is interrupted for a short while. Again, current circuit switched voice technology has been optimized for years to make this experience as seamless as possible, e.g. with soft handovers in 3G that totally eliminate delays and interruptions.
I hope some serious tests will follow these announcements soon to see where we really are with VoLTE and how that compares to other mobile voice solutions available for a while now.
And a final non-technical thought: I wonder what kind of discussions VoLTE will bring about when network operators that block other VoIP services on their mobile network today will launch their own service. Will that be the end of third party VoIP blocking?
2 thoughts on “US and Korean Operators Launch VoLTE – Some Thoughts”
As far as I know Korean operator KT is planning to switch off their 2G network and use their 1800 spectrum for LTE. This could be the reason why they push forward with VoLTE.
A note about handovers reminded me the presentation of Telefonica UK’s LTE trial which I saw here. http://3g4g.blogspot.co.uk/2012/07/telefonica-uks-lte-small-cell-trials.html
On page 24 the report states that downlink interruption time was in the region of 45ms. It’s not VoLTE, but I think it gives some insight of what can be achieved.
It’s not just QoS via RAN management, it’s also about broader user experience. VoLTE is not an app you launch or need to know user names in a walled garden. VoLTE is phone number based and universally reachable
VoLTE will be supported at chip level in phones in future and aim to reduce power draw, helping with battery life.
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