SKtAt the second day of yesterday’s LTE Voice conference, which took place in London, the presentation by Changsoon Choi of SK Telecom attracted a positive responses from the audience, and really brought home how ahead of the game the South Koreans are in LTE and with particular relevance to the conference, in terms of VoLTE.

Choi started with a simple list of SKT’s achievements in LTE so far. As of 2012 it had 99 per cent population coverage based on a dual layer 850MHz and 1800MHz multi-band network and currently has 89 cities running dual-carrier LTE Advanced, all of which means it’s no surprise is enjoys 48 per cent market share for LTE in the country.

As would expect for the conference, Choi focused on its implementation of VoLTE, which is fully deployed across its network and fully supported by 13 devices of the smartphones it offers on its network.

SKT has branded VoLTE as HD Voice as it used the Adaptive Multi-Rate Wide-Band codec, giving it much great quality than voice over 3G. It can also offer much higher quality video (VGA H.264, vs. QCIF H.263) and users can easily switch between a voice and video call.

Choi also said call set-up time was on average halved from five seconds to 2.5 seconds, though it can be much faster than that.

SKT also looked to offer unique services over its network such as group video calling for up to four people at a time and large scale audio conference calling.

The strategy behind this was to keep its users hooked on using SKT’s network and happy to pay for a higher tariff, thanks to unique services and carrier grade QoS, as opposed to the best effort approach of the OTTs.

Choi revealed that SK Telecom has also commercialised SRVCC, meaning that it the small areas where there is no LTE coverage voice calls fall back gracefully to 3G, moving from the IMS core back to the GSM core.

It has implemented new technologies in house to support its IMS service such as a Telephony Application Server (TAS), and a Media Gateway Control Function (MGCF), while on the RAN side it employs RoHC – Robust Header Compression, which is able to compress voice packets due to the similarity in most voice header packets.

According to Choi, the reason for SK Telecom’s dedication to implementing the most cutting edge voice services is that it seems South Korean users really, really care about voice quality. “If there’s one dropped call users call up to complain hundreds of times!” he said, rather exaggeratedly.

Choi finished off by saying that now it was at the cutting edge for LTE voice services it was now looking to implement VoLTE roaming in the near future, though he didn’t give any details as to partners.

All in all it was a pretty exciting look at what the rest of the world can look forward to for VoLTE. From a user perspective the prospect of higher quality voice calls as standard is appealing – as I’ve experienced it, and if you’re an iOS7 user, you can too.

There might be no VoLTE on EE’s 4G network here in the UK, I have experienced HD Voice. As I mentioned earlier, in Apple’s iOS7 update it introduced FaceTime Audio calls, which means iPhone iOS7 users call each other, routing the call as data via Apple’s servers.


It was possible before, by making a FaceTime Video call and switching away, but Apple has now implemented it as an easy to use option in the OS, making it much more likely to be used.

There are reports that in the US it is blocked by the carriers, but I can confirm that on EE it works between an iPhone 5 on EE’s LTE and an iPhone 4S on O2’s network (MVNO GiffGaff to be precise).

Why is it cool? Because it’s great. The iPhone may not officially support VoLTE, but FaceTime Audio is a voice call carried as data packets that uses the same AMR-WB codec as VoLTE, so for all intents and purposes it’s the same thing.

My better half noticed the improved call quality without prompting, which from a non tech enthusiast was a very positive sign that’s it’s worthwhile. From now on I’ll be making an effort to use it to call people who I know have an iPhone. If use does become widespread amongst iPhone users, it’s another step on the road of removing the relevance of the carrier in the mind of the consumer.

If the operators want to hold off the inevitable, at least for a little while, they should be looking at the SK Telecom model and getting their VoLTE act together as soon as possible. And then shouting about it from the rooftops.

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