AOL has struck a deal to acquire Millennial Media, a provider of mobile-advertising technology and services, for a net $238 million in cash.

AOL — which Verizon Communications acquired this year for $4.4 billion — is offering $1.75 per share of Millennial Media common stock, a 31% premium over Millennial’s closing stock price Wednesday.

The deal for Millennial Media bolsters AOL’s mobile-ad capabilities, as it fights rivals like Facebook and Google for share of marketing spending as consumers spend more time on smartphones and tablets.

Millennial Media operates a mobile-advertising network with more than 65,000 apps. For publishers, in-app ads have the benefit of being immune to content-blocking software. All told, AOL said it now has access to about 1 billion global active unique users.

Separately, Verizon is gearing up to launch a wireless video service, dubbed Go90, which will incorporate AOL content and ad-serving tech. The telco has announced content pacts for the service with partners including Viacom, AwesomenessTV, Vice, Scripps Networks Interactive and ESPN.

“AOL is well positioned as consumers spend more and more time on mobile devices, and as advertisers, agencies and publishers become more reliant on programmatic monetization tools,” AOL president Bob Lord said in announcing the pact.

Millennial Media, founded in 2006, has about 575 employees. The company is based in Baltimore with additional U.S. offices in Atlanta, Boston, New York and San Francisco, and international offices in Hamburg, London, Paris, Singapore and Tokyo. Millennial Media’s portfolio of assets includes acquisitions of TapMetrics, Condaptive, Metaresolver, Jumptap and Nexage.

For 2014, Millennial Media reported $296 million in revenue (up 14% year over year) and a net loss of $149 million versus a net loss of $15 million a year earlier.

AOL said the deal, subject to customary regulatory approvals and other closing conditions, is expected to close this fall.

In 2013, AOL acquired programmatic video-ad platform provider Adap.TV for $405 million.