Microsoft continues to invest in online advertising to be able to compete with major rivals Yahoo and Google. In the last few months, the firm has made three digital acquisitions; first it was European mobile advertising firm ScreenTonic, then big aQuantive for $6 billion (Microsoft’s biggest acquisition in history) and now online advertising exchange firm AdECN. According to Microsoft, AdECN would add the final element to its online advertising portfolio.AdECN is a real-time, auction-based, marketplace for buying and selling display advertising. It is similar to that offered by Right Media, the firm Yahoo acquired last April for more than $680 million.

“It works much like a stock exchange. A member of the AdECN Exchange buys on the exchange for its advertisers and sells on the exchange for its publishers. This guarantees members the best possible liquidity – fewer campaigns go unfilled, less inventory goes unsold – and more liquidity means higher revenues.The member’s advertisers and publishers benefit, too, from the extreme targeting and impression-based pricing in the AdECN Exchange, which helps members attract and retain the best clients.” [AdECN]

Founded in 2003, and with nearly 30 employees, AdECN brings new capabilities and expertise to Microsoft’s online advertising network AdCenter.