T-Mobile versus AT&T Mobility 3G questions [telecom]

Some friends and I were discussing unlocked phones and this came up.

I own a quad-band GSM phone that I got through AT&T. I chose a quad-band phone for when I'm overseas. I get 3G speeds in Malaysia with it. Just for grins I popped my wife's T-Mobile SIM in and also got 3G.

My wife's T-Mobile phone is not quad-band. I put in my AT&T SIM and only had EDGE.

In my mind this makes sense if these things work like I think they work in the United States. But someone disagreed with me. He said it was impossible for me to have seen 3G speeds with anything other than an AT&T SIM. Who is correct?

Reply to
John Mayson
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T-Mobile's 3G in the USA uses 1700 MHz; AT&T's 3G in the USA, and pretty much every other 3G carrier elsewhere in the known GSM universe, uses 1900 MHz. So your at&t 3G-capable phone (using 1900 MHz) will see 3G speeds pretty much everywhere (using any SIM that is recognized locally as an active roaming partner's), while your T-Mobile 3G-capable phone (using 1700 MHz) will see 3G speeds only in the USA on the US T-Mobile 1700 MHz 3G network (using any SIM that is recognized by T-Mobile USA as an active roaming partner's).

In short: it's the radio in the phone, not the issuer of the SIM, that determines whether that phone will be able to exploit the local 3G service. At&t uses the same 1900 most of the rest of the world uses; T-Mo USA uses 1700 instead.

HTH. Cheers, -- tlvp

Reply to

T-Mobile's AWS 3G uses 1700/2100 Mhz combination for 3G. AT&T uses

850 and 1900 Mhz combined.

You don't mention which phone or device you're attempting to put on a network. If it's a device like the iPhone if you use it on T-Mobile you'll only get EDGE since its internal radio only can use 3G at 850 and 1900 Mhz combined with 2100 Mhz. It all depends on what device you're using and if the device is capable to use T-Mobile's AWS bands with combination of 1700/2100. It will revert to EDGE or if no EDGE to GPRS.

It should work fine in any area that uses GSM for voice using 850,

900, 1800 or 1900 Mhz.
Reply to
Joseph Singer

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