In its monthly report, mobile ad network Millennial Media (http://www.millennialmedia.com/) says iOS ad impressions remained relatively flat for August. The report looks at how each OS, device and manufacturer is performing the independent ad network.

In August, Millennial combined connected devices and smartphones when breaking out the OS impression share. That’s significant because iOS and Android share can include tablets into factoring presence on the network, notes “TechCrunch” (http://macte.ch/RPTqy).

In August, Android was in the top spot with a 54% share, while iOS was in second with a 28% share. Rim followed with 13% share.

In terms of growth, Android impressions (including both phones and tablets) grew 48% month-over-month globally. iOS impressions were relatively flat month-over-month. Windows Phone 7 impressions increased 48% month-over-month.