Voice over Internet protocol, or VOIP, just keeps getting bigger. The Nimbuzz mobile application integrates voice, chat and messaging from multiple providers like Skype, Microsoft and Google. The company just announced that it surpassed 3.65 billion mobile voice minutes in the last year. About half of these minutes were paid calls via Nimbuzz Out whereas the the rest were free calls between Nimbuzz users. Nimbuzz is consistently in the top 5 downloads on Getjar, an app store which serves multiple mobile platforms, and Nokia’s Ovi store.

A research report from In-stat on VOIP in 2013 predicts that more than 50% of users in 2013 will use mobile VoIP via providers like Nimbuzz, while under one-third will utilize mobileVOIPVoIP services from  mobile carriers. 11% of users will make VOIP calls with operators using WiMax or LTE, two warring standards for ultrafast, fourth-generation wireless networks. While the EMEA region currently generates more mobile VoIP revenue, Asia-Pacific is expected to be the largest regional market in revenue terms by 2013.

I talked to Nimbuzz CEO Evert-Jaap Lugt about trends he sees in VOIP services. He told me that one of the main changes in the last couple of years is in the attitude of the mobile carriers, who were previously very hostile to mobile VOIP. Now they are starting to look at partnering with providers like Nimbuzz. The alternatives are buying a VOIP startup or building their own VOIP services but according to Lugt, carriers don’t have a good track record on innovating in-house or on capitalising on acquisitions. He mentions the failure of Vodafone 360 as an example.

In Lugt’s opinion, carriers have is the ability to provide a level of quality of service which cannot be matched by VoIP on the open Internet. Capacity is running out fast in current 3G networks but a carrier can counteract this by providing the first leg of a mobile VoIP call (the mobile phone to base station link) over 3G and then route via the Internet. In upcoming all-Internet 4G networks, where capacity will be much higher, VOIP calls can be routed entirely over the carrier’s network.

However, Lugt doesn’t think higher capacity alone will solve the bandwidth problem. He suggests that carriers should start blocking data services which are not monetizable, e.g. Youtube videos, and offer multiple mobile data plans with different bandwidth rates.

Nimbuzz is based in Rotterdam in the Netherlands, has 100 employees and funding of over $25 million.