Android is the fastest growing OS in terms of US internet activity

There's now so much data produced about the number of mobile devices, their online activity, and their interactions with ad networks that even the companies producing this stuff are having to split out the categories.

That's why mobile advertising outfit Millennial Media is separating its SMART ad performance report.

The new Mobile Mix report will cover track device, OS and carrier data.

In terms of the basic breakdown of the US market during March 2010, smartphones account for 45 percent of the traffic on its ad network, feature phones 34 percent, and connected devices, such as iPod touch, iPad, PSP and DSi, 21 percent.

As expected, the smartphone segment is dominated by iPhone (70 percent of activity), followed by RIM at 14 percent, Android at 6 percent and Windows Mobile at 4 percent.

All OSes apart from Windows are growing fast. Apple was up 20 percent month-on-month, RIM 25 percent, and Android an impressive 72 percent.

In terms of device manufacturer, following Apple on 70 percent, Samsung was second at 19 percent, RIM third at 8.6 percent and LG and Motorola fourth with 7.2 percent.

Thanks to the strength of connected devices as a category, 27 percent of people access the mobile internet via wi-fi, while Verizon and AT&T both have 15 percent of the market.

According to IDC, Millennial has the largest mobile media audience in the US, reaching 83 percent of mobile users.

[source: Millennial Media]