IP networks deployed by fixed and mobile operators will lead to an explosion of mainstream VoIP and SIP services worth $150bn by 2012, experts predict.

ABI Research forecasts a huge increase in SIP services driven by the increasing popularity of 'smart' devices such as PDAs and smartphones.

"New affordable price points and ease of use will allow consumers to benefit from SIP services such as instant messaging, video sharing and conferencing, which will join VoIP as it takes over from circuit-switched voice," said ABI Research principal analyst Ian Cox.

"We have seen the start of a revolution, as mobile handsets become the product of choice not just for voice and simple text messaging, but for any task that users can perform on a PC.

"And as networks are replaced by 'flat architecture' all-IP with SIP application servers in the core, all forms of communications become possible."

Cox added that SIP services will develop into "the norm" after 2010 and rapidly begin to dominate the world's telecoms markets.

Almost half of all telecoms users will be using at least one SIP service by 2012, but will have many services from multiple devices able to communicate with other users and services across the web and between enterprise and public networks.

This market will generate over $150bn in service revenue annually with cumulative infrastructure capital expenditure of over $10bn by that date.

"Using SIP, telephony becomes another web application which can be integrated into other internet services," said Cox. "It enables service providers to build converged voice and multimedia services."

ABI Research expects that almost 1.2 billion VoIP users will be active by 2012, with most users also subscribing to several forms of messaging and video sharing driven by interest in user-generated content.

Additional services supported by SIP will include presence, click-to-dial, buddy lists, email and web access, which are assumed to be "core" services and included as standard in any service offering and bundled with broadband access.

A portion of the VoIP users will also be connected to a fixed-mobile convergence service.