Messaging apps, known as "over-the-top" apps because consumers don't pay carriers directly for the services, typically go beyond plain-vanilla text messaging with features such as voice notes, camera applications, access to games and virtual stickers that are popular among teens and young adults.

WSJ: The Messaging Apps Taking on Facebook, Apple

As a result, operators can more effectively ensure a carrier-grade quality of experience for end users of High Definition voice and video, Web conferencing, instant messaging and presence, and other broadband-intensive mobile applications that go beyond the reliability of Skype, Apple FaceTime and other services suited for consumers but inadequate for the rigors of enterprise use.

FORBES: The Time Is Now For Mobile Operators To Monetize LTE