A cellphone to tote abroad? These have your number

Imagine having one cellphone, one number, that would work anywhere in the world.

True international roaming is a major goal for many globetrotters. Travelers increasingly want one mobile number that works as easily in Venice, Italy, as it does in Venice, Calif. Unfortunately, most American cellphones are not compatible with foreign networks. As a result, many have found it easier (and cheaper) to buy a calling card or rent a phone while traveling overseas.

But the 2002 arrival in the US of German wireless company T-Mobile (along with AT&T's switch to the GSM network standard) has greatly simplified the "one phone, one number" concept - especially for Europe-bound travelers. Utilizing the popular and internationally dominant Global System for Mobile (GSM) communications standard, T-Mobile, AT&T, and Cingular (in selected markets) offer "global" tri-band phones to access the world's three major GSM cellphone frequencies. A fourth player, Nextel, has long offered international roaming.

It's all part of the move toward third-generation, or "3G," service whereby your phone does much more than just make domestic calls. Global roaming, text messaging - even photo transfers - are some of the fruits of the fiercely competitive marketplace. Who would have thought that you could send a text message from your portable phone in the US to a friend in Holland?

One caveat: While the GSM standard works in most of the wired world, callers using this system are still out of luck in destinations such as Japan and some Latin American countries. Canada and Mexico mostly use the current American TDMA (time division multiple access) standard, so most US callers have always been able to roam there.

Just how easy is it becoming to roam around the world with an American cellphone number? We checked out four companies.

T-Mobile carries several models of triband world phones. When used in conjunction with T-Mobile's international roaming agreements, they allow customers to immediately place calls in 90 countries, including all of Latin America. They can access their voicemail and text messages as well.

T-Mobile's edge is its aggressive pricing, especially in Europe. It costs 99 cents per minute to place or receive calls within 26 European nations - far less than the $1.24 per-minute rate AT&T charges in Western Europe. T-Mobile's rates, however, can run as high as $4.99 per minute in a few countries such as Russia and Indonesia. Customers can add international roaming at no charge by calling customer support. The service is usually activated within 24 hours.

Wondering about use of these phones stateside? T-Mobile took over Voicestream's networks and offers some of the cheapest calling plans around. The downside: Coverage is not as strong as some competitors such as AT&T or Verizon. But the firm's sharing agreements with Cingular have bolstered both companies' footprints.

For frequent international travelers, T-Mobile's combination of affordable rates in the US and abroad is a good way to use your home phone number when you travel.

For years, AT&T has provided "one phone, one number" international calling through its WorldConnect program using the TDMA network. And it's been relatively simple to use: Pay $25 for a small SIM phone identity card that contains your phone number, and then insert it into a rented GSM phone for international use. But it's not cheap. Beyond the $25 set up, you'll pay an extra $7.99 per month in access fees in addition to a 99 cent per-minute charge and long distance fees. But with so many American customers on AT&T's TDMA network, this program remains popular for occasional overseas travelers.

But that's changing over the next few years as AT&T switches its entire network to GSM, dubbing the new system "mMode." Rolling out nationally this fall in large urban markets (New York went online in October), mMode offers new and upgrading customers more options.

For example, family members can each carry a phone that works with the same number. mMode also offers cool features such high-speed Web surfing and phones equipped with digital cameras. But most important, by switching to the new service, you can use the same phone at home or abroad - at no additional cost and with no additional fees beyond the per-call charges.

Those who use a Siemens S46 phone can have the best of all worlds since it works on both the TDMA and GSM networks.

As AT&T upgrades its US networks, consumers have a choice of services and price. Old calling plans that rely on the TDMA network are less expensive and offer better coverage in rural US areas, but don't allow you to take your phone overseas.

The nation's fifth-largest cellular company, Nextel is one of the oldest providers of international roaming with its Worldwide program. Like the competition, Nextel customers can use their cellphones overseas, paying a per-minute charge in each country at rates listed on its website. Its overseas and domestic calling plans are comparable in cost to the competition.

The difference with Nextel is in the phones. World travelers can use the slightly bulky Motorola i2000 plus, which works on Nextel's US and overseas networks. Those looking to travel with a smaller and lighter phone can purchase the outstanding Motorola P280 for $149, or the popular (and svelte) aluminum- encased V60 for $249. And for those who aren't Nextel customers but want a phone for one trip, the company offers short-term rentals for $9.95 a day.

Nextel also has a wide range of phones and plans for domestic callers, all featuring the company's exclusive "Direct Connect" feature, which allows customers to connect with one another using their phones like two-way radios.

After launching in 2001, Cingular is one of the country's largest cellular providers - even though they only recently added New York City as the final cog in their national network. Cingular offers GSM service in many of its largest markets, while phasing out TDMA service. The company plans to complete the conversion by the end of 2004, providing global roaming in 68 international destinations.

In the US, Cingular entered into a cooperative network-sharing agreement with T-Mobile this year, bolstering their GSM coverage and giving both companies improved signal strength in many areas.

Cingular's pricing plans are competitive, and its phones are some of the newest. It also offers "rollover minutes," whereby unused minutes are saved to the next month.

• Ari Cheren is gear and news editor for MountainZone.com. He writes about new products and travel for publications including the New York Post and Bloomberg Financial.