When BTC Mobility launches a new cellular network later this year using the Global System for Mobile Communications (GSM) standard, the carrier will not be the first to have migrated from another standard to GSM.

North American cellular operators which adopted the time division multiple access (TDMA) standard have discovered that their technology has reached the end of its lifecycle and that provisioning third-generation mobile services, like always-on wireless connections to the Internet, will require a change of technology.

So BTC Mobility is spending $12 million to adopt GSM, essentially building a new network from scratch, minus the towers and switching equipment used to direct calls. The company began building the network in March and is scheduled to finish it in time for a product launch on October 1.

Although GSM is the world's most popular standard for mobile phones, most subscribers in North America do not use it, which is why BTC decided to implement TDMA when it launched its digital cellular network in 1994.

TDMA was the dominant standard in North America, and deploying it in Bermuda allowed subscribers to take their phones with them when they travelled - or "roam" - and handle calls placed by visitors from the US and Canada.

But now even carriers in North America are switching to GSM, which is standard in most parts of the world, except Japan and Latin America. According to the GSM Association, 71 percent of the world's wireless market uses GSM.

Cingular, America's second largest cellular network, announced it would switch to from TDMA to GSM last October and will spend $3 billion to do so. AT&T Wireless is offering GSM service in major US markets and plans to deploy the technology across the country by the end of the year. Even in the Caribbean, Telecommunications Services of Trinidad and Tobago, a telecommunications monopoly owned by the islands' government and Cable & Wireless, is spending $26.4 million to supplant its TDMA network with a GSM one.

Some of the change-overs have been at the expense of North American companies which manufacture network gear for cellular operators. BTC Mobility, for instance, has bought its network equipment from Nokia of Sweden. Nortel, a Canadian company, supplied the equipment for the old TDMA network.

Once the network is operational, customers will be able to access the Internet through their telephones and personal digital assistant, according to Stanley Wright, the general manager of BTC Mobility. "Content will be a part of our offering and will be available from the outset," he said. Some carriers already offer similar services in the US. Sprint PCS's Vision allows customers to check their regular e-mail with their phones, surf the web in colour, send instant messages to America Online users and transmit photos from one phone to another.

But Sprint's network runs on code division multiple access, or CDMA, a standard which competes with GSM and is mostly found in the US. Verizon Wireless, America's largest mobile operator also uses CDMA and has no plans to switch, despite pressure from one of its major stakeholders, Vodafone of Britain.

Industry analysts say that competing standards have hindered the adoption of mobile phones in North America, where they are not as commonplace as in Europe. European mobile networks all run on GSM, making it easier for customers to switch between them and lowering costs for handset manufacturers.

A single standard has also allowed European subscribers to send each other text messages through a service known as short message service, or SMS.

(But the GSM standard itself isn't even completely global. North American GSM networks run on different frequencies from networks in Europe, meaning subscribers have to buy a dual- or tri-frequency phone if they plan to use it in both places through roaming agreements.)

Stanley Wright, BTC Mobility's General Manager, would not say how many carriers his company has signed roaming agreements with, which will allow customers to use their phone overseas. Mr. Wright also refused to say for how long his company would keep its old digital network running, although he explained that phasing it out would depend on how quickly GSM coverage spreads across the US. At the moment, GSM networks still provide relatively spotty coverage.

Kurt Eve, the president of Bermuda Digital Communications, which owns Cellular One, said his company was "currently deep in discussions" about its third generation network.

He said there was no question that the company would have to upgrade its network sooner or later, and that it is choosing between GSM and CDMA.

Mr. Eve said that while GSM has the advantage of global interoperability, CDMA has quicker data transfer rates which are faster than those of a typical modem. GSM's data transfer rates are about half the speed.

But if Cellular One chooses CDMA over GSM, it could have a hard time convincing customers of the other two networks to switch because they would have to buy a new handset.

Bermuda's newest wireless carrier, Telecom, deployed a GSM network from the very beginning. The company has promoted the standard's worldwide compatibility in its marketing - its slogan is "The international standard".