Mobile ads are expected to generate around $3.3 billion worldwide this year, more than double the $1.6 billion the industry took in last year, said Gartner today.

That number is likely to soar ever further, hitting $20.6 billion by 2015. Ads for mobile search and map sites and applications are expected to kick in the largest share of revenue, while video and audio ads will grow the fastest over the next four years, according to Gartner.

As a result, companies are expected to boost their budgets for mobile ads, growing from just half a percentage point of their overall ad budgets last year to more than 4 percent in 2014.

"As the adoption of smartphones and media tablets extends to more consumers, the audience for mobile advertising will increase and become easier to segment and target, driving the growth of mobile advertising spend for brands and advertisers," Andrew Frank, research vice president at Gartner, said in a statement.

Mobile ad budgets will grow the most across North America and Western Europe, accounting for 28 percent and 25 percent of the global market by 2015, Gartner said. But Asia/Pacific and Japan will stay the market leader over the next few years, accounting for 49 percent of all mobile ads this year and 33.6 percent in another four years.

Though mobile advertising will certainly grow in terms of revenue, Gartner also expects it to grow in terms of the overall user experience.

"In 2011, we are finally seeing some important drivers fall into place, so that we can expect the market to more than double year over year in the coming two years," said Frank. "This doesn't mean, by any stretch, that the experience delivered by mobile advertising will reach its optimum point in that time frame. We expect that targeting and contextualization, especially in social sites and applications, will carry on improving throughout the forecast period and beyond."