Google's Android mobile operating system will power nearly half of the smartphones worldwide by the end of next year, technology research company Gartner said Thursday.

Worldwide sales will reach 468 million units this year, up 57.7 percent from 2010, increase to 630 million units next year and to 1.1 billion units in 2015, Gartner said.

Gartner said software, which Internet giant makes available to handset makers such as Samsung, HTC and Motorola for free, will be the most popular smartphone operating system (OS) worldwide by the end of 2011 with a 38.5 percent , rising to 49.2 percent next year and 48.8 percent in 2015.

Apple's iOS for the will hold a 19.4 percent share of the smartphone operating system market by the end of 2011 followed by Nokia's Symbian with 19.2 percent and Blackberry maker with 13.4 percent, Gartner said.

Microsoft's Windows mobile operating system will account for 5.6 percent of the smartphone market at the end of 2011 but will rise to 10.8 percent in 2012 and 19.5 percent in 2015, Gartner said.

The iPhone's market share was forecast to remain relatively stable at 18.9 percent in 2012 and 17.2 percent in 2015.

Symbian's smartphone share will decline to 5.2 percent next year and virtually nothing by 2015 as the Finnish telecom giant replaces the current operating system with Microsoft's platform.

Gartner said the rise of Android will bring lower smartphone prices.

"By 2015, 67 percent of all open OS devices will have an average selling price of $300 or below, proving that smartphones have been finally truly democratized," Gartner principal analyst Roberta Cozza said.

"As vendors delivering Android-based devices continue to fight for market share, price will decrease to further benefit consumers," Cozza said.

"Android's position at the high end of the market will remain strong, but its greatest volume opportunity in the longer term will be in the mid- to low-cost smartphones, above all in emerging markets," she said.