Windows Phone 7 is not even a mere six months old and already one research firm has it pegged as the future second biggest operating system in the U.S.

A report from IDC predicts by 2015 Windows Phone 7 will have 20.9 percent share of the U.S. smartphone market. This would put it in second place behind Android, which IDC predicts will have 45.4 percent share. IDC's report has iPhone's iOS and Research in Motion's Blackberry operating system in third and fourth place respectively with 15.3 percent and 13.7 percent each.

IDC says the alliance with Nokia will provide the spark Windows Phone 7 needs to become one of the more dominant operating systems in the market. If IDC's predictions are true, it will get the market share that Nokia's Symbian has for 2011, which is 20.9 percent.

The new alliance brings together Nokia's hardware capabilities and Windows Phone's differentiated platform. We expect the first devices to launch in 2012. By 2015, IDC expects Windows Phone to be number 2 operating system worldwide behind Android, said Ramon Llamas, senior research analyst, in a statement.

Meanwhile, the Framingham, Mass.-based research firm is expecting impressive growth overall for the entire smartphone market. According to IDC, the smartphone industry will grow 49.2 percent in 2011 from 2011. Furthermore, vendors will ship 450 million smartphones in 2011 compared to the 303.4 million units shipped in 2010.

Overall market growth in 2010 was exceptional, Kevin Restivo, senior research analyst with IDC's Worldwide Quarterly Mobile Phone Tracker, said in a statement. Last year's high market growth was due in part to pent-up demand from a challenging 2009, when many buyers held off on mobile phone purchases. The expected market growth for 2011, while still notable, will taper off somewhat from what we saw in 2010.