3G/4G on US T-Mobile using ST18a or ST18iSupport


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  1. onyx

    onyx Member

    Any ideas on this phone's compatibility on 3G or even 4G on T-Mobile data? What about if phone is allowed to data roam onto other networks, any possibility of getting higher speeds?

    Which version would be ideal with roaming (ST18a?), and without roaming (ST18i?)?

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  2. Josh-SonyXperia

    Josh-SonyXperia Well-Known Member

    The "i" version should work fine with T-Mobile. The "a" version is the one we would recommend to use with AT&T and they have different 3G frequencies than T-Mobile. So for T-Mobile we do recommend the "i" variant version of our phones.
    onyx likes this.
  3. onyx

    onyx Member

    With the "i" version can I get a US warranty? And with "a" version can I not roam onto AT&T's 3G even though I'm on T-Mobile?
  4. Josh-SonyXperia

    Josh-SonyXperia Well-Known Member

    The "i" variant doesn't have warranty in the US. And if you are using T-Mobile's services you cannot roam onto AT&T's network.
  5. onyx

    onyx Member

    That's a little bit of a downside, but one that I'm willing to deal with.

    Not true: hxxp://support.t-mobile.com/thread/7721

    I'm still not sure what the real-world implications are given the frequencies available to either the i- or a-versions, and so I'm still in limbo about which version to experiment with. Or is it even worth trying, no matter how badly I want this phone?
  6. Josh-SonyXperia

    Josh-SonyXperia Well-Known Member

    If you want an Xperia ray, the "i" will give you the best experience for 3G with T-Mobile. Obviously you must take into consideration your roaming situation, but otherwise, the "i" is for you.
  7. onyx

    onyx Member

    While Josh's assertions seem definite, I think they are wrong. My final assessments (as of now) are the following -- please correct where / if I am mistaken.


    • 3G (or 4G) will not be possible on either the ST18a or ST18i. It requires 1700MHz and 2100MHz, and then T-Mobile needs to allow phone compatibility. (Ref: hxxp://en.wikipedia.org/wiki/T-Mobile_USA#3G_upgrade)
    • If the phone is allowed to roam onto AT&T (this is tower-to-tower dependent), it will only get 2G, even if the tower is capable of 3G on non-1700/2100 frequencies. The restriction on speed is based on the roaming agreement between T-Mobile and AT&T.
    • The last (and possibly only) Xperia that had 1700MHz was the X10. I do not know if that phone was able to get 3G on T-Mobile.

    Some speculation for future -- if/when AT&T acquires T-Mobile bandwidth allocation over the various frequencies may be modified. Maybe the only good news is for T-Mobile customers is for those who buy the Xperia Arc ST18a. (Ref: hxxp://en.wikipedia.org/wiki/Merger_of_AT%26T_and_T-Mobile_USA#Frequencies)
  8. esquire415

    esquire415 New Member

    The Xperia Ray will only work on T-Mobile USA's 2G network. I too want this phone so bad but I do not want to pay through the nose tied to AT&T's contract. I've been trying to find out if it will work on T-Mobile's 3G network.

    The Ray works on UK's T-Mobile (and i'm sure in other countries) and they have the i version. I looked at the specs that's being sold on Amazon and it does not say 1700Mhz so I came to a conclusion that it's pointless to get it if I can't use 3G on it. So now i'm shopping around for 2nd best :( (the Arc is too big for me).

    For about $30 a month you can get this FREE in UK on a 24 month contract with 500mb-1GB data, 300-500 minutes, and 300-unlimited text! That's damn cheap! We are really getting ripped off here in the US! :mad: It will cost me over $300 to buy it and then $75/mo on AT&T for a 2yr contract with only 200mb of data! That doesn't make sense, might as well get the iPhone 4S for $200
  9. onyx

    onyx Member

    1700MHz is only relevant for 3G on US T-Mobile. The i-version should be OK if you are traveling to Europe, where it seems they have standardized on frequencies and communication protocols. Wikipedia will tell you in more detail: hxxp://en.wikipedia.org/wiki/UMTS_frequency_bands

    FWIW, a friend is using an unlocked AT&T iPhone on T-Mobile (US) and gets 2G reliably and almost everywhere he goes. He doesn't stream video, just data for email, web, and maps, and finds it just fine for his needs.
  10. Dane123

    Dane123 New Member

    Did someone check if the ST18A is actually working on AT&T's 3G network?
  11. ply17410

    ply17410 Member

    I am using the ST18a on AT&T and getting the full benefit of HSDPA 7.2 speeds (same as iPhone 4). Wifi Hotspot and USB tether both work too.

    You can go HERE for carrier APN settings. (see very bottom of thread for correct ones).

    Here are some data speed results vs. my wife's Neo using speedtest.net app.

    34 tests to 18 servers each for Neo and Ray (same servers). Tests were performed one after the other (alternating Ray and Neo) in an AT&T HSPA+ w/enhanced backhaul coverage area between 8PM to 9PM.


    PHONE Download Upload Ping
    Xperia Ray

    1,735 868 402
    Xperia Neo 1,722 875 420


    USB TETHER
    Xperia Ray 2,382 1,084 277
    Xperia Neo 2,264 771 185

    Good luck,

    Bob H
    onyx likes this.
  12. onyx

    onyx Member

    I own the ST18a. It does not (work on AT&T 3G) if you are on T-Mobile, only 2G AT&T as a roaming client. On an AT&T SIM, it is designed for 3G. Not sure about 4G LTE.
  13. Josh-SonyXperia

    Josh-SonyXperia Well-Known Member

    To clarify your doubt the ray is not a 4G phone.

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