The CEO of T-Mobile says that VoIP service will be far less disruptive on mobile devices than it has been on fixed line telephony:

VoIP (voice over Internet Protocol) services provided over mobile phone networks will have “far less impact” than those offered over fixed-line networks, Akhavan said Tuesday on the sidelines of a news conference at the 3GSM conference in Barcelona.

“There are all sorts of technical issues that make mobile VOIP services difficult to implement,” he said. Technical issues related to how networks pass on IP addresses of mobile users have not been completely resolved, he noted. “Take reachability, for example: How can the call come to me?”

Akhavan also said emergency phone service and “always on” connectivity are also big issues, since staying online takes up bandwidth on pricey mobile networks.

And then there’s price: “When people talk about VOIP, they think free,” Akhavan said. “With any mobile service provided over the Internet, you’re going to need to buy a data package.”

Mobile VoIP “will take a small share” of revenue generated by mobile voice services, he said.