AT&T plans to buy online ad company Ingenio for an undisclosed sum, a move to vie against Google and other online advertisement leaders.

Ingenio's technology is meant to evaluate the effectiveness of advertisements by tracking phone calls made to businesses based on phone numbers in ads, including online, on mobile phone Web sites, and in print. The technology provides the phone numbers and tracks the calls, and advertisers pay based on the volume of calls generated by the ads.

AT&T said it will integrate the technology into its yellowpages.com Web site, where the technology would help take advantage of the trend toward performance-based advertising.

AOL uses Ingenio's technology for pay-per-call ads, and MSN uses it for display ads to mobile users, Info World reported.

According to AT&T, it plans to keep Ingenio's management team. The deal is expected to close in January 2008.

Online ad platforms operators such as Google and Yahoo are searching for ways to display more targeted ads and improve the usage of ads, according to Info World.