Worldwide voice over IP services will clock up a relatively small number of subscribers compared to conventional fixed and mobile phone offerings for at least the next five years, research has predicted today.

However, the study by ABI Research added that, in terms of relative growth, VoIP remains a highly dynamic market with the most successful operators using the technology's strengths to add value to existing broadband subscriptions.

Michael Arden, principal analyst for broadband technologies at ABI Research, pointed out that consumers can get VoIP services from a variety of sources, including telcos, broadband providers using DSL, cable companies and hosted providers such as Vonage which do not own a network.

Arden believes that VoIP's greatest benefit for the consumer is consolidation. "You could have your email working with your voicemail, working with your telephone, working with your Outlook calendar. Such enhanced value services are a key drawcard," he said.

ABI Research's report also noted that one of the largest residential VoIP deployments, accounting for a sizeable percentage of the world market, has been carried out in Japan by Softbank BB, a broadband provider that is dipping a toe in the "telco TV" pool.

Such broadband operators trying to take market share from incumbent telcos have had some success, according to Arden, largely by taking an existing DSL network and adding VoIP to its data services.

"Because of the dominance of cable broadband, the battle in North America will be between hosted VoIP companies and cable companies. The cable companies will push VoIP to their existing customer base using cable modems," he said.