According to Reuters sources, AT&T Wireless is planning to introduce a high-speed Internet service for cell phones in certain U.S. markets this summer.

As early as mid to late July its third-generation, or "3G," mobile phone service that is capable of transmitting not just voice and simple text messages but also pictures, video and hefty e-mail attachments will be available to AT&T Wireless customers.

The network upgrade is designed to replace its older network that was largely used for digital voice calling and pits the company against U.S. mobile leader Verizon Wireless.