Wesley's Tool-Box

Cellular communications have traditionally used separate voice and data channels. But with the advent of smartphones, bulk of the communications now happen on the data channel. It's no coincidence that only the data channel remained by the 4th generation (4G) technology. To carry voice, though, a fallback to 3G or older technology's voice channel was initially needed. But VoLTE (Voice over LTE) came onto the scene to do away with this by letting the data channel handle voice as well.

As with many technologies, Korea was a forerunner in adopting VoLTE. World's first commercial VoLTE service was launched more than two years ago by two of the three major Korean carriers, SK Telecom and LG U+. The remaining one, KT, joined mere two months later. Worldwide adoption didn't really take off until earlier this year, however. About a dozen carriers around the globe now have it. Noting this trend, Apple has decided to enable the capability in the iPhone 6 series.

So naturally, I wanted to see VoLTE on my iPhone 6 Plus in action. It can be enabled in the Settings app by going to Cellular and selecting "Voice and Data" option for LTE. The previous 5/5C/5S models simply have toggle switch for LTE instead, even with iOS 8.0 update. After that, I made voice calls to a lot of different lines, including a VoLTE-enabled phone on the same carrier. But every time, the connection indicator turned from LTE to 3G, showing that VoLTE wasn't working.


I checked to see how the network recognized my iPhone 6 Plus. It was being listed as an OMD Default Handset, the same name that my iPhone 5S was given when it was brought in from the US. In other words, a generic device that it doesn't recognize. Perhaps the network couldn't tell whether the device had a VoLTE capability, so it simply ignored its attempts. It was time to visit my carrier's branch office to get to the bottom of this.

LTE frequencies tend to be quite varied because it has to be either laid alongside or replace the existing 2G and 3G networks. Even so, Apple tries to support as much frequencies as possible because it will reduce the number of region-specific models. Unfortunately, iPhone 5S and 5C each sprawled to five different models, so people asked around whether their iPhones would work on another country's LTE network. I even wrote about iPhone 5S's LTE network compatibility last year, and it has the longest comment thread in this website.

This time around, though, the number of models were reduced to a much more manageable two for both iPhone 6 and 6 Plus. The massive 20-band support did the trick. The good news here is that, if you bought an unlocked iPhone 6 or 6 Plus anywhere in the world and come to Korea, the LTE will work with all three local carriers. Korea should get A1586 / A1524 models on sale in a couple of months, but A1549 / A1522 models often found in United States or Canada should work, too.

After I brought the A1524 iPhone 6 Plus from Japan to Korea, I put the SIM card from my 5S and turned it on. The device had no problems connecting to SK Telecom's LTE network right away. I've confirmed that the situation is the same when you're on KT's network, as well. It seems that the network no longer goes into 3G mode when it sees an unrecognized LTE device, which used to be the case when I brought the iPhone 5S from United States last year.


Meanwhile, the top speed for LTE data on iPhone 6 series was pushed to 150Mbps from 100Mbps of 5/5C/5S. The bleeding edge phones in Korea are always a step ahead - 150Mbps was possible when iPhone 5 came out and the recent models can do 225Mbps - but with low monthly data caps, they are little more than technology show-off right now.

In any case, I wanted to see how fast the iPhone 6 Plus can do LTE data in real life, so I ran a speed test app. As you can see here, it can go almost up to 100Mbps. Pretty good, but that's how fast an iPhone 5S could supposedly do, as well. Obviously, a side-by-side test was needed.

These screenshots tell you about the reality of SKT (Korea's #1 mobile carrier by subscriber count) LTE network working on iPhone 5S.

First of all, the so-called "wide band" LTE does work on it. In the "Serving Cell Info" within Field Test app, "Download Bandwidth" shows 20MHz, which is twice as wide as the regular LTE service. "Freq Band Indicator" says 3, which means it's operating at Band 3 (1800MHz). This is SKT's secondary LTE frequency, as well as where the wide band service is provided.

SKT's cell towers with Band 3 support, let alone being wide band, is currently limited largely to Seoul metropolitan area. In fact, these screenshots were shot at Samseong subway station in Gangnam district (yes, THAT Gangnam), the area which can arguably be called the central business center of Korea.

SKT has just started bringing wide band support to Band 3 towers last month, with 10 districts (out of 25) in Seoul getting the treatment as of today. Nationwide deployment is said to be done by mid-2014. So while SKT is blasting away advertisement about how it has both LTE-A and wide band LTE, the people who can enjoy them is pretty limited, to say the least. KT (#2 carrier) is said to be slightly ahead, as it claims full deployment in all of Seoul at the end of last month.

The screenshot on the right shows the speed measurement, showing 33.1Mbps down and 5.30Mbps up. iPhone 5S can do 100Mbps downstream given the wide band support, but it only gets 1/3 of that. Of course, getting this much speed in the bustling commute of a large business zone is not unimpressive. But unless conditions are perfectly met, you won't see anything like the speeds that the ads are so proud to show you. Of course, you knew that already.

What it also means is that the maximum speeds that wide band LTE can supposedly provide, 150Mbps, isn't really going to be missed by iPhone 5S supporting "only" 100Mbps max. So prepare to enjoy your iPhone 5S - Apple says it'll be coming to Korea on October 25th.

Over the past four years, I have bought all the iPhones that had been officially released in Korea on the first day of domestic availability, starting with iPhone 3GS. iPhone 5S is the first one that I didn't wait. Of all those phones, iPhone 4 is currently on leave (dad is using it), so I have 3GS, 4S, 5, and 5S for simultaneous performance testing.

This may be something a lot of people would be curious about and I hope to give you a good basis in considering an upgrade for your previous generation iPhones. Read on and let's get started.

UPDATE (Sept. 25, 2014): There has been some changes in activating LTE devices from overseas in Korea. [Read the related iPhone 6 Plus review.]

When my friend Andy lined up to get the new iPhone 5S, the Apple Store had specific supplies of the phone for each of the four major U.S. carriers. If three of the carriers supposedly use the same model as seen in Apple's website, it might seem strange that this division existed. It turns out that each of the phones have a SIM card for the designated carrier, as well as some specific device status configured (SIM lock, CDMA enable). As you can see, Andy got me an AT&T version of the iPhone 5S with model number A1533, with the AT&T NanoSIM as a proof.

Now, Apple mentions that the model number of the iPhone 5S planned to be released in Korea is A1530, which forgoes the AWS and 700MHz bands used in North America and instead supports TD-LTE bands used in places like China. Interestingly, both models (as a matter of fact, all models) support LTE bands currently active in Korea, so it seemed likely that A1533 iPhone 5S would be able to hop onto LTE networks in Korea. This was the reason I risked buying A1533 outright instead of trying to get A1530 from Hong Kong or wait for official Korean release. It turns out my hunch was correct, but it's not completely plug-and-play. Read on to minimize the chances of bumping into problems.