From time to time there is talk in the press about being 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.
Here are two examples. Looking at the specifications for the iPhone 4, you will see that it provides service in the 850 and 1900 MHz band for U.S. coverage and in the 900, 1800, and 2100 MHz bands for the rest of the world. It does not support AWS-1 spectrum, so moving to T-Mobile means you will not have any 3G service. Further, when AT&T and Apple got together, AT&T made changes to its network to support some of the iPhone's more advanced features. Again, moving it to another network means some of this functionality will be lost. The other example is the new BlackBerry Torch that AT&T recently launched. Again, it provides both 2G and 3G support for both the 850 and 1900 MHz bands in the United States as well as the four European and world portions of the spectrum at 900, 1800, and 2100 MHz (UMTS), but it does not support the U.S. AWS-1 band so moving it to T-Mobile would mean giving up access to 3G services.
This works almost the same between Sprint and Verizon but most of the phones on these networks do support both 850 and 1900 MHz even though Sprint has no spectrum on the 850 MHz band. If the Sprint phone includes 4G or WiMAX, moving it to the Verizon network means you will give up your 4G service unless you contract with Clearwire (if that is even possible).
Does LTE solve the problem?
LTE will make use of an improved SIM card and most phones for use in the United States will be built to support the 700 MHz LTE service and either GSM/HSPA or CDMA 1X and EV-DO Rev A. Again, if you swap networks you will lose your 3G coverage and, for the next few years, any voice capability. When LTE becomes ubiquitous, you will still have a problem with some phones. The 700 MHz band is very wide and I expect to see some AT&T-only and Verizon-only LTE phones that will also support the corresponding 2G and 3G technologies.
The bottom line is that the concept of unlocked phones seems reasonable, but in practice, even with an unlocked phone, your options are limited when moving to another network. If, as rumored, Verizon does begin to carry the iPhone in 2011, no one is sure whether it will be 2G and 3G compatible only or if it will support LTE as well. And if Verizon makes the same types of additions to its network that AT&T has made, the best way to enjoy the Verizon iPhone is the same as the best way to make full use of the AT&T iPhone, which is to stay on the network for which it was intended.
One final comment: LTE will become the new world standard for 4G services around the world. Every existing network, at some time or another, will implement LTE. However, this does not mean any LTE phone will work worldwide. LTE is being deployed on 11 different portions of the spectrum--not a single slice as was hoped--and building 11 different frequency bands into a mobile device, in addition to 2G and 3G support, will be almost impossible. As good as the design engineers are, there is only so much RF you can put into a device and have it resemble the small, sleek phones we have today, with the extended battery life we enjoy today.
The bottom line is that you must do your homework if you are thinking about purchasing a phone with the intention of moving it to another network. Chances are that you will sacrifice some of the functionality of the phone if you move it to another network. It is difficult enough for the great design engineers to build everything into a device today. It will become more complex in the future and we will see more, not fewer devices that are network-centric.
Andrew M. Seybold is an authority on technology and trends shaping the world of wireless mobility. A respected analyst, consultant, commentator, author and active participant in industry trade organizations, his views have influenced strategies and shaped initiatives for telecom, mobile computing and wireless industry leaders worldwide. On Oct. 5, 2010 at the CTIA Enterprise & Applications conference, Seybold will lead the Andrew Seybold Wireless University seminar examining the elements of wireless now and into the future: technologies, devices, applications and content. For more information click here.