Will U.S. enter DoCoMo's walled garden?

At first glance, NTT DoCoMo's deal to buy 16 percent of AT&T Wireless Group this week might seem like a major win for U.S. mobile communications. The U.S. mobile market is about two years behind that in Europe, with basic features such as text messaging and wireless data access only now emerging.

DoCoMo's i-mode system, on the other hand, is the world's most successful implementation of the mobile Internet. Though it is a "walled garden," offering access only to selected online services, the system has grown to 14 million users and has become a mainstream phenomenon. In Europe, carriers such as British Telecommunications and Deutsche Telekom have met with little demand for their WAP (Wireless Application Protocol) services.

But American wireless systems are unlikely to catch up to Europe's any time soon, said analyst Carsten Schmidt, with Forrester Research. For one thing, the United States is still hampered by infrastructure issues, such as vast geographical areas to be covered and competing network protocols, Schmidt says.

DoCoMo may have difficulty getting Americans to accept its view of the mobile Internet as a closed system.

"There are a huge number of applications, but it is a very restricted environment," Schmidt said. "If you look at U.S. users, they are much more Internet-savvy than in Japan, and they don't like the walled-garden environment that much."

It may also be difficult for U.S. companies to get in on i-mode when it is launched in America, for the simple reason that the system will already be full of existing applications provided by DoCoMo's Japanese partners.

"They want to open up new markets for companies that had success with i-mode in Japan," Schmidt said. "That could lead to an environment where you have … limited possibilities for U.S. players to take advantage of it."

There's also the fact that DoCoMo, through a deal with KPN, is also planning to launch i-mode in Europe.