Overall worldwide mobile phone sales will increase 16 percent this year to 779 million this year and will reach the one billion unit milestone in 2009, according to a market study released Wednesday by market research firm Gartner.

In addition to sales of one billion mobile phones in 2009, the research firm predicted that there will be 2.6 billion units in operation that year.

"The world's appetite for mobile phones has exceeded even the most optimistic expectations," Ben Wood, Gartner's research vice president for mobile terminals, said in a statement. "Mobile phones could go on to be the most common consumer electronics devices on the planet."

The study said that sales of next-generation phones are starting to accelerate. It predicted that more than 100 million 3G phones will be sold next year and more than 200 million smartphones will be sold in 2008.

Part of the reason for the increase is that, while users in mature markets like the U.S. and Western Europe are busy buying replacement devices, use in emerging countries is growing rapidly in emerging nations, the study notes. The Chinese and Indian markets are growing particularly quickly, the study said.