In addition to charging per bit, Verizon plans to tackle the business of mobile VoIP the same way it's handling wired services: by making it part of a bundle that only the huge wired and wireless carrier can offer.

"The voice service will become part of something different, something larger," said Ivan Seidenberg, Chairman and CEO of Verizon Communications. "It's not that Skype's doing anything wrong, but eventually they're going to get outpaced," he said.

By contrast, AT&T suggested it ultimately will rely more heavily on selling low-priced bits.

"The way the world is going, it'll just be, 'How much data do you want to buy?' and you do whatever you want over that data," said Ralph de la Vega, president and CEO of AT&T Mobility and Consumer Markets, during a media lunch at CTIA. Though he noted it was too early to talk about rate plans for LTE, which AT&T is not expected to roll out until 2011 or later, de la Vega said the nature of the technology will reduce the operator's cost to deliver a given amount of coverage. For subscribers who aren't comfortable with the idea of buying data, AT&T may have to devise rate plans that translate bits of data into minutes of use, he added.

Clearwire, the one mobile operator that is already relying on 4G, believes quality is the key to VoIP. It plans to make money partly by delivering that quality.