InMobi, which calls itself the largest independent mobile ad network, has released its North American Mobile Insights Report for January 2012.

The reports show iOS retaking first place from Android in terms of is share of North American advertising activity on InMobi's network. 

It also reveals significant growth in mobile advertising, as InMobi's network grew by 82 percent, or 25.2 billion monthly impressions.

Share and share alike

According to activity on InMobi's ad network, in January, iPhone accounted for 35.5 percent of impressions, up from 23.2 percent in October 2011. This is attributed to iPhone 4S.

Meanwhile, Android had a 32.7 percent market share, down from 35.9 percent in October.

RIM dropped from 20.5 percent share to 11.6 percent over the same period.

Making an impression

"The iOS growth we are seeing may be attributed to the tremendous success of iPhone 4S and iPad in the ecosystem," said Anne Frisbie, InMobi's VP and MD for North America.

"Overall, we are excited to see InMobi's available impressions exceed 55 billion in North America, and look forward to continuing our rapid growth through 2012."

[source: InMobi]