In response to Microsoft's previous patent complaints about Motorola, the Libertyville, Ill. company has struck back with a suit of its own.

The cell phone manufacturer announced it has filed a lawsuit in the U.S. District Courts for the Southern District of Florida and the Western District of Wisconsin against Microsoft for several patent infringements. Motorola's patents in the PC and server software relate to Windows OS, digital video coding, email technology including Exchange, Messenger and Outlook, Windows Live instant messaging and object oriented software architecture.

Motorola's R&D and intellectual property are of great importance to the company and are renowned worldwide. We are committed to protecting the interests of our shareholders, customers and other stakeholders and are bringing this action against Microsoft in order to halt its infringement of key Motorola patents. Motorola has invested billions of dollars in R&D to create a deep and broad intellectual property portfolio and we will continue to do what is necessary to protect our proprietary technology, said Kirk Dailey, vice president of intellectual property at Motorola Mobility.

Dailey also mentioned he thought it was unfortunate Microsoft chose the litigation path rather than entering into comprehensive licensing negotiations. He said Motorola has mutually beneficial licensing relationships with the great majority of technology companies industry-wide.

We are still reviewing Motorola's filing, which we just received. This move is typical of the litigation process and we are not surprised. We remain confident in our position and will continue to move forward with the complaints we initiated against Motorola in the U.S. District Court for the Western District of Washington and with the International Trade Commission (ITC), said Horacio Gutierrez, Microsoft's deputy general counsel of intellectual property and licensing.