1. AC Question's Avatar
    Hi everybody,

    Okay so I need a new cell phone. I switched from Verizon to T-Mobile, and even though they assured me that my Galaxy S4 would work fine on their network, it doesn't at all. This is where I'm stuck... I'm going to be moving to South Korea in the next few months, so I want to get an unlocked Samsung Galaxy S6 that will work on T-Mobile while I'm here, and then work on the Korean cellular networks when I move over there. I'm seeing lots of conflicting info though. Every other site I find literally says the exact opposite: "You can ONLY use GSM in Korea..." then "You can ONLY use CDMA in Korea." And I can't figure out the LTE capabilities either. I don't actually know how to get a definitive answer on this and figure out which version of the unlocked phone to get. Anyone who has any experience with this or any guidance would be VERY much appreciated!

    TLR. I need a fully functional unlocked Samsung Galaxy S6 that I can use in the US, and that will be fully functional in South Korea. Help?

    P.S. I was looking at the Samsung Galaxy S6 SM-G920i, but upon further investigation it looks like it says it may only work in North and South America.
    02-07-2016 05:40 PM
  2. B. Diddy's Avatar
    Welcome to Android Central! South Korea does not use CDMA (i.e., the network technology that Verizon and Sprint have used, and are currently phasing out). They use UMTS for 3G, which is a GSM technology that uses WCDMA (which is different from CDMA--confused yet?). So what you might have seen was that South Korea uses only WCDMA for 3G, which is the same as saying they use only GSM.

    These are the bands that South Korean carriers use in general: Network coverage in KOREA - 2G/3G/4G mobile networks. For a few more details, see here: GSM World Coverage Map- GSM Country List by frequency bands. What you need to do is look at the specs for various S6's, and find one that has overlap with both T-Mobile (see here: https://support.t-mobile.com/docs/DOC-4988) and with the Korean carriers.

    From what I can tell here (Samsung Galaxy S6 - Full phone specifications), the variants noted in the band listing should work for both, because they all have the 2100 band for 3G (UMTS means that you can't get the HSPA+ speeds, but it should still be able to connect), and they also cover the LTE bands for both T-Mobile and the major Korean carriers.
    02-07-2016 10:23 PM
  3. SirSavage's Avatar
    Whoa, thank you so much for the detailed answer!! I really appreciate you going out of your way to get that information for me! Honestly, it is very much appreciated!! Could I just ask for clarification about this part:

    "UMTS means that you can't get the HSPA+ speeds, but it should still be able to connect"

    I'm tech savvy with some things, but not cell phone tech. Thanks for the help!
    B. Diddy likes this.
    02-08-2016 03:08 PM
  4. B. Diddy's Avatar
    This is where I'm not 100% sure:

    UMTS and HSDPA are two separate 3G technologies. HSDPA (or HSPA) can achieve higher speeds than UMTS, but is still technically 3G (and not 4G, which would be LTE). The GSMArena link above mentioned that South Korea uses the 2100 MHz band on UMTS for 3G. The phone specs say that the phone supports 2100 MHz on HSDPA for 3G. Now, I think the phone that supports 2100 MHz on HSDPA can still be used on a South Korean network that uses 2100 MHz on UMTS, and I think it just means you won't be able to get the faster HSDPA speeds--but I'm not sure. Let me ask around.
    02-08-2016 10:04 PM
  5. dpham00's Avatar
    There's no s6 that is fully compatible with all USA and Korean networks. You would need to pick and choose. In South Korea, cdma, gsm, umts, and lte is used. Depends on the network.

    Umts encompasses hspa+ and hsdpa and is referred to as 3g worldwide except for 2 networks (att and tmobile) which refer to hspa+ as 4g. If it supports the bands that you need then you are good. Don't worry about whether it is called hspa, hdspa, hspa+, or wcdma.

    Worldwide, lte is referred to as 4g, except in the usa which refers to it as lte or 4GLTE. This is important that you get the bands that are used by your carrier.
    B. Diddy likes this.
    02-08-2016 10:45 PM
  6. B. Diddy's Avatar
    Hey dpham00, do you have any site that definitively shows Korean carriers using CDMA? It's confusing when I search. The sources that mention Korea using CDMA are pretty old, and this article seems to imply that most carriers are on GSM/UMTS/LTE now: Will My Phone Work in Korea? | The Expat Lounge
    02-09-2016 12:32 AM
  7. Rukbat's Avatar
    02-09-2016 05:48 PM

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