In addition, greater visibility might mean new kinds of charges or caps.

"A potential downside is that every type of communication these users might have over the wireless networks might be metered," and subscribers could be charged more for using certain applications, DePuy said.

With PCRF, carriers could also give higher network priority to subscribers on a more expensive plan, analysts say. The software also allows them to give some third-party applications priority over others and charge those application providers for the privilege.

These practices may all be legal under net neutrality laws, which typically treat wireless services differently from wired. U.S. Federal Communications Commission rules adopted in 2010 prohibited "unreasonable discrimination" against third parties on wired networks but not on wireless. They also said mobile operators can't outright block services that compete with their own. Verizon Wireless those rules last year.

The IDG News Service