Marketing guru Larry Weber's W2 Group Inc. has led a $6 million round of venture funding in Ringleader Digital, a mobile ad serving company formerly known as MoPhap that serves campaigns for Absolut, Best Western and Blu-Ray.

The investment from W2 Group's W2 Innovations, which is part of a Series A funding round, is designed to help Ringleader strengthen its mobile ad network. It will also help with branding and corporate development initiatives.

"The whole rebranding is focused on the next stage, which is a deep sales focus and growing our footprint in the marketplace," said Bob Walczak, CEO of Ringleader, New York.

With this deal, Ringleader becomes part of W2 Group, a Waltham, MA-based company whose portfolio includes social media firm Digital Influence Group, ad agency Partners + Simons and public relations specialist Racepoint Group.

Ringleader offers third-party ad serving, doing for mobile media what DoubleClick and Avenue A/Razorfish's Atlas do for online media. The company works with publishers, carriers and ad agencies to extend online advertising experiences to mobile.

Also, Ringleader can be integrated into customers' current online campaign management systems, according to Mr. Walczak.

Another key strength of Ringleader is its creation of a device-agnostic network to deliver ads by device functionality.

In essence, Ringleader claims it can deliver ads on any available mobile network and serve ads that work best with the appropriate mobile phone. So, the company will only serve a video ad to a mobile phone that can play it.

"What really made online advertising mature into a sustainable market was the third-party advertising," Mr. Walczak said. "Third-party advertising gives the control back to publishers to manage their inventory and optimize their inventory across multiple ad networks."

The Ringleader investment comes less than a month after a spate of similar announcements in the mobile space.

The marketplace fundings include $25 million for mobile monitoring service Integrated Media Measurement Inc.; $12 million for mobile ad network Ad Infuse; $8 million for retail and mobile media delivery firm Modiv Media; $6.2 million for mobile real estate listing firm Smarter Agent; and $3 million for mobile ad serving firm GoldSpot Media.

This increased confidence from venture capital firms is indicative of mobile marketing's growing acceptance as a viable channel.

"I think the market's starting to mature," Mr. Walczak said.

"We're going to see larger and larger ad buys and the reason for that is that the mobile market is maturing -- faster networks, more advanced devices -- and new technologies like third-party ad serving are really going to validate the market and take it to the next level," he said.