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Korean smartphones unable to connect to US 4G networks?

 
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RLib



Joined: 17 Apr 2012

PostPosted: Fri Oct 04, 2013 6:10 am    Post subject: Korean smartphones unable to connect to US 4G networks? Reply with quote

Curious if anyone knows more about this, and if there is anyway to resolve it.

The SO and I both bought used smartphones while living in Korea-- Samsung Galaxy II and LG Optimus. 4G worked great with our phones while in Korea, naturally.

We brought both of our phones back to the states, and are unable to connect to the US 4G network with TMobile. Or 3G. Or 2G. We are basically just stuck with 1G. Everything else with our phones work-- we can use it as actual phones, connect to wifi, etc. We simply cannot get anything better than 1G data.

We took our phones into T-Mobile and the store rep spent some time trying to resolve it. He said he's had a handful of other customers with Korean phones who have the same issue. After doing some more research, he discovered that Korean phones are not on the same frequency as American phones, which is why they are not able to connect to anything other than 1G.

Can anyone confirm this or have more info about it? Or know more about the difference in frequency (does it only vary by country? By service provider? In other words, if I switch to Verizon or Sprint, could I connect to their 4G network?) I've been searching myself, but w/o much luck.
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Deja



Joined: 18 Mar 2011

PostPosted: Fri Oct 04, 2013 2:13 pm    Post subject: Reply with quote

Most importantly: T-Mobile uses a completely different 3G frequency from other networks (it uses 1700MHz), which I think absolutely no non-US T-Mobile phone supports Sad They do have 1900MHz band in SOME cities, but it is like 20 locations, in the entire US, total.

More importantly, US does not have 4G really Smile 3G/4G in the US are both 3G really, with 4G being H+ (better variant of 3G). So in both those cases, T-Mobile requires 1700MHz band.

I don't even know what 1G is, and didn't think it is used Very Happy If you mean EDGE for 1G and GSM for 2G .... K.
GSM on T-Mobile is on 1900MHz (in places where it does not use it for 3G/4G) band, which your phone probably does not support.
Korea uses only 2100MHz band for 3G/3G+ (what US carriers call 4G), and the phones are not likely to support other bands. S3/S4 are a bit different, but S2 was quite different.
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RLib



Joined: 17 Apr 2012

PostPosted: Fri Oct 04, 2013 5:00 pm    Post subject: Reply with quote

Deja wrote:
Most importantly: T-Mobile uses a completely different 3G frequency from other networks (it uses 1700MHz), which I think absolutely no non-US T-Mobile phone supports Sad They do have 1900MHz band in SOME cities, but it is like 20 locations, in the entire US, total.

More importantly, US does not have 4G really Smile 3G/4G in the US are both 3G really, with 4G being H+ (better variant of 3G). So in both those cases, T-Mobile requires 1700MHz band.

I don't even know what 1G is, and didn't think it is used Very Happy If you mean EDGE for 1G and GSM for 2G .... K.
GSM on T-Mobile is on 1900MHz (in places where it does not use it for 3G/4G) band, which your phone probably does not support.
Korea uses only 2100MHz band for 3G/3G+ (what US carriers call 4G), and the phones are not likely to support other bands. S3/S4 are a bit different, but S2 was quite different.


Ah, thank you for this, Deja! This explains a lot. And you're right, it must be EDGE that it is connecting to-- my phone simply shows it as "G," which is why I assumed it was a 1G network.

So AT&T supposedly uses 1700MHz-2100MHz (not too sure if it's a range, or either/or type of thing), and Verizon is supposedly in the process of changing theirs to the same. Does that mean, in theory, our phones would work on one of these networks?
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Deja



Joined: 18 Mar 2011

PostPosted: Fri Oct 04, 2013 8:11 pm    Post subject: Reply with quote

I don't think ATT is using 1700 - 1900 and 2100 for 3G, but 1700 is for LTE - S2 has no LTE Smile
LTE = actual 4G.

http://en.wikipedia.org/wiki/AT%26T_Mobility#Radio_frequency_summary

I have no idea about Verizon however, they are on CDMA, and I have no idea how that works KO-US-KO.
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RLib



Joined: 17 Apr 2012

PostPosted: Fri Oct 04, 2013 9:16 pm    Post subject: Reply with quote

My phone actually says LTE. Not too sure if there is a way for me confirm it in the settings/"about phone" section, but when I turn my phone on it says "Samsung Galaxy SII HD LTE." If that's correct, does that mean that, in theory, I could connect to AT&T's 4G network where available, but in areas where 4G is not available, I would receive no data since everything else is below 2100MHz?

And sorry for all my questions and ignorance about this.-- and if I'm just grasping at straws. I really appreciate your help, though.
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Jake_Kim



Joined: 27 Aug 2005
Location: Seoul

PostPosted: Sat Oct 05, 2013 2:38 am    Post subject: Reply with quote

See the full breakdown of LTE bands in use first:
http://en.wikipedia.org/wiki/List_of_LTE_networks

Samsung Galaxy SII HD LTE must be one of SHV-E120, variant S or K or L.
Now, S variant for SKT supports LTE frequencies of TX: 824 ~ 839 MHz, RX: 869 ~ 884 MHz
K variant for KT supports TX: 1735 ~ 1740 / 1745 ~ 1755 MHz, RX: 1830 ~ 1850 MHz
L variant for LGU+ supports TX: 839 ~ 849 MHz, RX: 884 ~ 894 MHz
The terms TX and RX are otherwise known as uplink and downlink, the frequencies above have been extracted from official manuals of respective variants.

AT&T US LTE operates within 700MHz frequency, or 'Band 17'. They are known to have recently filed with FCC for Band 12 usage in the future, but this is no other than an expansion into the lower spectrum within the 700MHz frequency band, and won't be implemented for another couple of years.

Wikipedia link by Deja, which mentions the use of '1700/2100 MHz AWS' (Band 4) with LTE protocol, is not necessarily incorrect but could be misleading since AT&T's utilization of this band is limited to certain geographic areas within the US, not nationwide. To verify, one can read through tech articles published last year with regard to Nexus 4 on AT&T.
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RLib



Joined: 17 Apr 2012

PostPosted: Sat Oct 05, 2013 10:19 am    Post subject: Reply with quote

Drats. I was really hoping there was some way for me to make this work, but it's obviously unlikely. We will just suffer through EDGE until we can get new phones.

Thank you both, Jake & Deja. You guys have been extremely helpful!
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Deja



Joined: 18 Mar 2011

PostPosted: Sun Oct 06, 2013 5:15 pm    Post subject: Reply with quote

http://www.gsmarena.com/samsung_galaxy_s_ii_hd_lte-4198.php
800/1600/2600 LTE bands on that S2, none of which are supported by AT&T. I didn't know they released an LTE version of S2!

S3 was probably the best we will get in regards of supported countries/frequencies, since Samsung is starting a region lock with S4 Sad
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