Mobile operators are set to generate revenues of nearly $20 billion by 2018 through Over-The-Top (OTT)-based voice services, according to a new study by Juniper Research.

This revenue stream will come from new service propositions created by operators as well as partnerships with standalone OTT players.

A growing number of operators have already made alliances with OTT players, for instance China Unicom joined forces last year with Tencent and its popular WeChat messaging app.

OTT providers have built up impressive customer bases but have a problem in monetising their millions of mobile VoIP users, which is what operators can offer though their billing relationship with users and established quality of service (QoS).

The study also touches on some intriguing new propositions that could generate revenue in the future, including the ability to port a single number across multiple devices.

Separately, the study forecasts that VoLTE services will prove popular among operators because of increased network efficiency rather than any future revenues.