The advantage of Android, the best operating system today

According to NPD, Android was running on 52 percent of all the smartphones sold in the U.S. last quarter, overshadowing iOS, which secured 29 percent market share. BlackBerry OS came in third in the smartphone space with 11 percent share, NPD said. Windows Phone 7, Windows Mobile, and WebOS all trailed with less than 5 percent market share each.

NPD's findings follow a similar report earlier this month from research firm Gartner. That company, which analyzed worldwide smartphone sales, said that Google's platform captured 43.4 percent of the OS market during the second quarter, up from 17.2 percent during the same period last year. Symbian came in second in Gartner's study with 22.1 percent share, followed by iOS at 18.2 percent. RIM's BlackBerry OS tallied 11.7 percent share worldwide.

Android Mobile Phone

Although NPD didn't dig into each vendor's market share on the quarter, the company did discuss Motorola Mobility. The research firm said that the handset maker's overall mobile-phone market share declined in the second quarter from 12 percent last year to 9 percent this year. In the smartphone space, Motorola Mobility's share dropped from 15 percent to 12 percent. Perhaps most concerning for the company, its Android market share hit 22 percent during the period, down from the 44 percent ownership it had during the second quarter of 2010.

That said, things might soon change for Motorola. Earlier this month, Google announced that it had agreed to acquire Motorola Mobility for $12.5 billion. The companies expect the deal to be completed by the end of this year or early next year. When that happens, NPD says, Motorola could find the reprieve it needs as it tries to keep up with a host of competitors, including Samsung and LG.

"Much as it did in the feature phone market in the RAZR era, Motorola is experiencing increased competition from Samsung and LG in the smartphone market," NPD's executive director of industry analysis, Ross Rubin, said of Motorola. "Closer ties to the heart of Android can help inspire new paths to differentiation."

However, for Google, its acquisition might have more to do with patents than anything else. The search giant and its vendor partners are being targeted from all sides by competitors that are launching lawsuits against Android, thanks to their stronger mobile patent portfolios. Google is being sued by Oracle, while Microsoft and Apple are taking aim at HTC, Samsung, Barnes & Noble, and others.

In a recent blog post, Google's chief legal officer, David Drummond, targeted those companies, saying that they are launching lawsuits based on "bogus patents." Those lawsuits, Drummond said, are only proving to stifle innovation in the mobile space.

"But Android's success has yielded something else: a hostile, organized campaign against Android by Microsoft, Oracle, Apple, and other companies, waged through bogus patents," Drummond wrote in the post. "Patents were meant to encourage innovation, but lately they are being used as a weapon to stop it."

Now, it seems, Google might soon have its own weapon to stop the patent lawsuits it takes so much issue with. Rubin said today that "Google's acquisition of Motorola shifts the balance of power in the handset-patent conflict between Google and its operating system competitors."

Google's Android mobile operating system dominated the U.S. smartphone market last quarter, research firm NPD announced today.

Aside from lawsuits, Rubin said that other Android vendors, worried that they will be hurt by Google's Motorola Mobility acquisition, shouldn't be concerned. He said that the operating system "has made for a larger pie" that allows everyone to benefit from its success.