Seybold's Take: The fallacy of unlocked phones November 10, 2010 By Andrew M. Seybold
able to purchase unlocked phones that can be moved from the networks they were intended for to other networks. It seems many people believe that if a phone is unlocked it can simply be moved from one network to another. This became a rallying point for many when AT&T Mobility and Apple teamed up for the iPhone on a five-year exclusivity deal.
Unlocked phones are readily available in Europe where all of the network operators share the same three portions of the spectrum and by law, each network can only run GSM and/or UMTS/HSPA and now LTE. They are not permitted to deploy CDMA. So unlocked phones in Europe function exactly like people expect them to: You buy a phone and then obtain a SIM card from the network you have chosen, insert the SIM and the phone registers on that network (assuming you have an account). If you want to change networks, you simply obtain a SIM from another network and swap it out with the SIM you have been using. End of story.
However, this does not work nearly as well in the United States and now Canada for a number of reasons. First, AT&T, T-Mobile USA, and other smaller network operators follow the European standards for GSM and UMTS/HSPA but Sprint Nextel, Verizon Wireless and a number of smaller operators have chosen to deploy CDMA2000 1X and EV-DO Rev A in this country. So it should be safe to assume that at the very least you could buy a GSM/HSPA-capable phone and move it from T-Mobile to AT&T or the other way around. But this is not really the case.
AT&T uses spectrum on 850 MHz and 1900 MHz today, and tomorrow it will be building out LTE on the 700 MHz spectrum it recently purchased at auction. T-Mobile, on the other hand, has no spectrum at 850 MHz. It does have spectrum at
1900 MHz and uses the AWS-1 spectrum located between 1710-1755 MHz and between 2110-2155 MHz for its HSPA network. Thus a phone designed for the AT&T network won't work on the T-Mobile network unless it specifically includes the AWS-1 spectrum.{ article continues at the following URL and brings up new caveats with LTE }