Mobile ad network Millennial Media has raised $15 million in a second round financing led by Charles River Ventures. With this funding, the company, which has offices in Baltimore and New York, has raised a total of $21.3 million. Millennial Media plans to use the funding to continue expanding its global sales force and business development initiatives.

The company recently made some upgrades to its performance-based network platform, Decktrade, including a one-click campaign management tool that helps automate the process of setting up budgets for campaigns across different carriers. Release

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• Mobile Ad Firm Millennial Media’s Total Funding: $6.3 Million First Round