Yup, and which is why the iPhone won't work on T-Mobile. No support for the frequency. Maybe they have a bit of spectrum in a market or two, but there is no way they will ever get full 3G coverage in the frequency that the GSM iPhone expects.

P, or Bryan,

Would one or both of you expand on your responses. I don't quite get it yet. (Also, lots of googling finds lots of "quad band Galaxy Nexus" references.)

Thanks,

http://en.wikipedia.org/wiki/UMTS_frequency_bands#UMTS-FDD (scroll up slightly from there to see the five "major" UMTS bands identified.

NOTE: GSM/EDGE band support is different from UMTS band support. Except where explicitly stated, the rest of this is about UMTS bands.

Band IV is T-Mobile USA's high speed data band.

Bands II and V are AT&T's high speed data bands.

The Galaxy Nexus has bands I, II, IV, V, VIII http://www.phonearena.com/phones/Samsung-GALAXY-Nexus_id5595

iPhones (the GSM versions, not the Verizon versions) omit band IV, so they won't work on T-Mobile USA's UMTS data network.

T-mobile phones typically (and varyingly) omit bands II, V, and/or VIII.

I suggest searching phonearena for a handful of modern phones and comparing the supported GSM (& EDGE) bands (where most/all smartphones are quad-band) and UMTS bands (where supported bands are much more varying).

Thank you!

All of the frequencies that cellphones operate (well at least 3G and 4G, I'm not 100% sure on GSM/CDMA frequencies) on are regulated (unlike the bands that WiFi networks work on which are unregulated). Phones need to be able to deal with these frequencies. They need to have antennas that can pick up those frequencies, as well as chips that can handle them.

This is the reason that you can use a AT&T GSM phone on T-Mobile's network, but not be able to access the 3G or 4G portions of the network (basically only ever be able to use Edge). Those phones aren't built to be able to receive/transmit in the bands that T-Mobile's towers are using for 3G and/or 4G.

Talking about quad-band and penta-band phones are talking about newer generation phones that can operate on more bands than just the ones used be a specific carrier's network. Note that the bands used can vary between countries, etc. Just because a country is using GSM for all of their cell networks doesn't mean that their 3G or 4G bands are the same as the one that your phone knows how to deal with.

Someone else can probably follow up with some Wikipedia links. Specifically there is a table in Wikipedia listing carriers from a huge list of countries and the bands that they are using.