So-called global roaming is virtually impossible today because wireless carriers use different types of phone networks that can't communicate with one another and require their own specially made phones. Business people traveling overseas often carry different cell phones because carriers on each continent use different networks.

Satellite phones offer service closest to global access, but they're more expensive than cell phones--sometimes three times as much--and the phones themselves only work on their own network of satellites.

On Tuesday, Bell Labs announced a software language called "Common Operations," or COPS, which wireless service providers would put on their networks and which would allow a wireless user's identifications and passwords to be read by the different network types. The product will eventually be sold through communications-gear maker Lucent Technologies to telecommunications carriers, but it won't be on the market for years, according to a Lucent spokesman.

There are still several hurdles to overcome, said Jack Kozik, director of enhanced services architecture at Lucent's mobility solutions group.

The handsets that would work with COPS must be created, for example. Wireless chipmaker Qualcomm said it is developing a chip so handsets could work on the CDMA (code division multiple access) standard, which powers about 15 percent of the world's telephone networks, and the standard known as GSM (global system for mobile communications), which powers about 75 percent of the world's cell phone networks.

Plus, the carriers would have to cooperate with one another to implement the global roaming software, an obstacle some analysts think could be more difficult to overcome than creating the actual technology.

"The technology solution is the easy part," said Shiv Bhakshi, a wireless analyst with IDC. "It's not easy what Lucent is doing, but that's essentially the easy part. Finding agreement on business principals, that's the difficult part."

But Jim Gerace, a spokesman for Verizon Wireless, said he thought the carriers would likely work together if the technology was developed. "We'll see," he said. "That's far in the future."

There are other problems for carriers as well, since adding the COPS gear to the networks will increase costs. Most already are spending billions to build new telephone networks that would make possible high-speed, always-on connections at speeds similar to what broadband Internet connections offer. Japanese carrier NTT DoCoMo launched the world's first high-speed network earlier this month. AT&T has launched a portion of its network. Most other U.S. carriers expect to do the same by year's end.

Some carriers, especially in Europe, are already financially teetering and are working to share the same networks they are building in order to trim costs.

Leading U.S. wireless carrier Verizon is working with Lucent to create a way for Verizon's 28 million U.S. subscribers, which use a CDMA network, to make calls on the networks of its parent company, Vodafone, which uses a GSM network, Gerace said.

The two companies combined have about 210 million wireless subscribers, more than a fifth of the cell phone customers in the world.