UMTS is operated on the 2.1 GHz band (or UMTS operating band I) pretty much everywhere around the globe. The U.S., however, is a special case. There, the band is already occupied for other uses. Thus, operators are using the 1900 MHz band both for 2G and 3G wireless (UMTS operating band II) and in addition the 850 MHz band (operating band V), again both for 2G and 3G. It looks like T-Mobile ran a bit out of luck when it came to 3G as they had to resort to a frequency band which is not used by anyone else so far.
During FCC frequency auctions last year, T-Mobile received frequencies in the what seems to be the new 1700/2100 MHz band (UMTS operating band IV). Here’s a report from Unstrung that describes this detail. The 1700 MHz part is used for the uplink while the 2100 MHz part of the spectrum is used for the downlink (network to mobile). I guess this is a bit confusing because speculations have been going on if T-Mobile will be compatible with UMTS devices sold in the rest of the world in the areas where they deploy 2100 MHz. Well no, they are not because the 2100 MHz part is just the downlink part of their spectrum. The uplink is on 1700 MHz and not on 1920-1980 MHz as for UMTS operating band I devices.
Here’s the table of UMTS operating bands from the standards (3GPP TS 25.101). Take a look on line 4. The frequency ranges match with those in the Unstrung report about the auction I linked to above.
Therefore be careful! Some people are saying that T-Mobile U.S. uses 2100 MHz but it is slightly off the European band. Well, that’s not accurate. The 2100 MHz portion is inside the frequency range used in the rest of the world. The uplink however, is totally off mark.
I am not sure if T-Mobile U.S. will be happy with these frequencies both long and short term. Not even the latest and greatest data cards supporting multiple UMTS bands like the Globtrotter from Option supports band IV today. Also, I wonder if the band will be used in other regions of the world in the future. If not, T-Mobile might have a big problem with 3G handset vendors as the market for band IV devices will be quite small. Also, the use of yet another frequency range for 3G in the U.S. will fracture the market even more.