The number of VoLTE connections will grow to 3.33 billion by 2021, according to the latest research from Ovum.
VoLTE currently stands at just 324 million connections, but by 2021 the technology will have penetrated 53% of total cellular subscriptions worldwide.
Ovum has found that operators are strengthening their commitment to roll-out VoLTE services in the efforts to reduce costs and are being encouraged by a growing number of compatible devices and successful VoLTE service launches by competitors.
According to Ovum, the main reason driving growth of VoLTE services will be the need for operators to reduce costs, moving services from voice to mobile broadband.
In the near term, the rapidly-increasing availability of standardised VoLTE devices will drive growth, while successful VoLTE service launches, such as by EE in summer this year, are already demonstrating clear operator benefits that that are encouraging other mobile operators to commit and launch their own services.
"The main reason operators are strengthening their commitment to roll-out VoLTE today is for cost reduction," says Craig Skinner, Principal Analyst at Ovum.
"The better spectral efficiency of moving voice to VoLTE allows spectrum to be re-purposed for mobile broadband. Longer-term, there is the potential to shut down legacy 2G/3G networks and simplify the network."