It used to be quite simple: In order to use a mobile phone in the US and the rest of the world you needed GSM service and a phone with "tri-band" capability: 900MHz and 1800MHz for most of the world and 1900MHz for the US. Then two things happened: First, the two major GSM carriers in the US started using 850MHz in addition to, or instead of, the 1900MHz band.

Second, the so-called "next generation" of GSM services became defined and partially deployed. Known as "3G" (WCDMA and UMTS are phrases often used) this new technology allows faster data rates and services such as video calls. A lot more could be said about 3G, but let's focus on the frequency. In most of the world, 3G is being offered on 2100MHz. The good news is that this includes some places that previously had no GSM service at all, notably Japan. The bad news is that (rumor has it), US carriers will be offering 3G service on 1900MHz instead.

So, where does this leave the global traveler? Well, to ensure maximum coverage you need at least a "quad-band" phone to cover 850/900/1800/1900MHz for traditional GSM service. There is some debate about the need for 850MHz in the US. Some experts claim that 1900MHz is usually ALSO available in places that has 850MHz, so 850MHz may not be required. Other experts point to a few remote areas that allegedly only offers 850MHz GSM service. If you travel a great deal in the US, you'll probably want a phone that is capable of operating at 850MHz. For International travel, make sure that your phone has both 900 *and* 1800MHz. Several US carriers now offer another kind of tri-band phone which has 850/1800/1900MHz. These phones are completely USELESS in many countries in the world (ones which only have 900MHz GSM service) and should be avoided at all cost.

Next you'll want to consider the 3G option. Most travelers are probably happy to just have the phone WORK in a foreign country and aren't that interested in video calls or other next-generation features. But if you want to use your phone in Japan, 3G (2100MHz) is the way to go. Cingular, for example, allows me to roam on both DoCoMo and Vodaphone Japan and it works very well.

There are currently VERY few phones that have the "3G plus quad-band" (850/900/1800/1900/2100) option. The Nokia N73 and E61 are candidates, but one features a high-quality camera and the other a full-featured PDA, making both quite expensive devices.

Trying to actually buy a "world" phone is quite frustrating. The phone makers insists on knowing where you live and offer only phones that are designed for your part of the world. The carriers are similarly focused on solutions for their particular country. This is a great shame. A truly "world capable" phone would be a big seller and would make tons of money for the carriers in roaming charges. (For extra measure I would want such a phone to be unlocked so that it can accept pay-as-you-go SIM cards which are readily available in foreign countries. If you spend a lot of time making local calls when you travel, such as SIM card can save you money).

Your only purchasing option appears to be the many online resellers, but buyer beware: these outfits often sell you "import" versions which come with documentation in a language you can't read and charging accessories with plugs that requires adapter plugs.

Wouldn't it be great if your actual phone carrier could help?

(Contributed by Ole Jacobsen)