02 Aug 2005

Global Roaming & World Phones - A Primer

For decades, cell phone users around the world, except in North America, have been able to use their mobile phones elsewhere around the globe. Why don't all U.S. cell phones work worldwide?

There are two answers to this question. First, there are different types of radio frequencies and equipment used by cell phone companies. If your phone doesn't operate on the available frequency or receive the encoding of the local service, it doesn't function.

The second problem with global roaming is a commercial problem. The reason Americans can travel all over the country and still use their cell phones even in areas where their provider doesn't have coverage is that U.S. providers have cross-billing (or roaming) agreements with each other. This allows you to connect to another cell phone carrier's service if yours isn't available. Roaming agreements are common within the U.S., but become more problematic internationally.

Compatibility Issues

Generally speaking, the rest of the world adopted the GSM cell phones standard when building out their cell phone infrastructures. This service was originally at a frequency of 900 MHz and now increasingly is being upgraded to an 1800 MHz service. Anyone with a GSM phone can, in theory, access cell phone service in the hundreds of countries that support that system.

On the other hand, U.S. and Canadian companies originally went with a different digital cell phone technology standard -- CDMA or TDMA, or, in Nextel's case, iDEN -- as well as a different radio frequency to transmit cell phone signals.

T-Mobile and Cingular (and previously AT&T Wireless) have since brought GSM to U.S. cell phone consumers; unfortunately, their GSM service operates in the 1900 MHz band, which is incompatible with the more common 900 MHz and 1800 MHz frequencies. That means that even these GSM phones won't work in Europe or most of Asia. (More about GSM frequencies.)

What are "World Phones" or Multi-band Phones?

Some phone manufacturers have started making multi-band phones that will receive 1900 MHz (and sometimes 850 MHz) in the U.S. and either or both of the international frequencies as well. Multi-band phones are ideal for frequent travelers who can't afford to be without cell phone service abroad and don't want the hassle of having to own a second cell phone (with a different number) or rent one for this purpose whenever they travel.

For true global roaming, multiband phones need to support at least three frequencies -- a U.S. band and both international bands: 900 MHz, 1800 MHz, and 1900 MHz. Don't be confused by tri-band phones which operate at both U.S. frequencies but only at one of the international frequencies -- that won't be as useful. On the other hand, if you have the option of a quad-band cell phone, one that supports 850, 900, 1800, and 1900 MHz, you'll have all your bases covered.

All that's said, here's what's important to remember: most consumers have no need for global roaming. If you don't travel internationally on business, this feature shouldn't make or break your cell phone choice. Pick your phone according to features that matter to you on a day-to-day basis.

Also see: Going Overseas With Your Cell Phone

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