The number of mobile VoIP minutes carried annually on 3G and 4G networks will rise from 15 billion minutes in 2010 to 470.6 billion by 2015, finds a new report from Juniper Research.

Mobile VoIP traffic will see steady rises in all regions over the forecast period, but particularly in developed markets, due to the increasing ubiquity of 3G networks.

"There are several flavours of mobile VoIP," says Anthony Cox, Senior Analyst at Juniper Research, noting that operators fear losing traffic to WiFi networks most: "WiFi mobile VoIP is potentially the most damaging of all VoIP traffic as it bypasses the mobile networks altogether," he says. "We forecast that mobile VoIP over WiFi will cost operators $5 billion globally by 2015," says Cox.

Other options for mobile VoIP carriage are via carrier alliances with mobile VoIP providers, or though an app downloaded to the handset or smartphone.

Further findings include:

• Competitive and regulatory pressure will mean that traditional operators in developed markets will increasingly "bury the hatchet" and forge partnerships with VoIP providers.
• Operator revenues from circuit switched voice will continue to diminish over the next five years, though the rate of decline will not accelerate.
• The market opportunity for high definition voice and advertising-based mobile voice services will be limited for the foreseeable future.

That Mobile VoIP is reaching the top of the agenda for mobile operators is borne out by the recent launch of Skype over 3G networks and its deal earlier this year with US operator Verizon. Operator sentiment varies however: "Even though a major operator, 3UK, touts the benefits of mobile VoIP, it will take some time for many operators, particularly in emerging markets, to accept it, since it represents loss of control over their own networks," says Cox.