Sprint Corp. (NYSE: S) says it wants to keep its unlimited data plans for smartphones as it moves to 4G Long Term Evolution (LTE) in the coming years.

The carrier hopes to launch its first LTE markets on 1900MHz PCS spectrum by the middle of this year. Then it will offer the faster mobile downloads over the 800MHz spectrum it currently uses for the Nextel network in 2014. (See Sprint Sets Due Date for iDEN's LTE Rebirth .)

One thing that probably won't change, however, is Sprint's allegiance to unlimited data on smartphones. The third-ranked CDMA carrier is the last of the big four U.S. operators not to cap or throttle its smartphone data plans, although it does charge $10 for the "premium" service. (See Time for a 4G Price War Already?)

"We would like to maintain unlimited indefinitely," said Sprint Chief Sales Officer Paget Alves at the company's Network Vision event Friday. "It's a serious differentiator for consumers." (See Photos: Inside Sprint's Network Vision .)

This means the operator will launch LTE devices with the same rate plans as it has on 3G. Sprint has to make sure that unlimited remains "economically practical," Alves added, by educating comsumers, off-loading data and managing "outliers" who abuse the system by Sprint's standards. [Ed note: Alves said that "video-based home systems" over the network would be an example of that.]

"Needless to say, we're walking a fine line," Alves noted.

Nonetheless, for now, Sprint's smartphone plans will remain unlimited, even as it caps tablet and mobile hotspot plans at 5GB. (See Sprint's Move to Advance Its Network Vision.)

— Dan Jones, Site Editor, Light Reading Mobile