Nexage, a Waltham-based mobile advertising exchange, said Monday that it closed an additional $5 million in funding from Hearst Interactive Media.

With that investment, Hearst joins SingTel Innov8, Relay Ventures, and GrandBanks Capital in Nexage’s Series B round, and the round now totals $15 million, Nexage said in a press release.

According to industry statistics, the mobile advertising market is expected to grow to $20.6 billion by 2015, Nexage noted.

Advertisement - Continue Reading Below

Nexage said its mobile advertising exchange helps advertisers to target and buy the audience best suited for their marketing needs.

One Nexage client is Rovio, a Finnish entertainment media company known for its Angry Birds game franchise. Rovio sells ads on some versions of Angry Birds, and Nexage helps ensure that those ads reach the relevant mobile audience.