Van Norman did say there might be a two or three second disruption for a bandwidth intense application such as streaming video when the phone switches from 4G to 3G.

Clearwire CEO William Morrow, also speaking to the CTIA crowd, urged other carriers adopting LTE to interoperate with WiMax. "We have the opportunity to converge [WiMax and LTE]," Morrow said. "Let's work together and go forward."

He noted that and Vodafone, among other companies, "all believe the time is not to integrate this and move forward."

Morrow also noted that chipmaker Beceem Communications recently announced a chip that supports both WiMax and LTE.

Verizon and AT&T representatives' responses to questions at CTIA about whether they would be willing to allow future devices to work over both LTE and WiMax were less than encouraging.