Microsoft has announced a lawsuit against Motorola, alleging that several of the mobile company's Android devices infringe on nine of its patents. The software giant is suing in US District Court in Washington, and is also bringing a complaint before the International Trade Commission (ITC). The patents are all related to key smartphone experiences that include syncing e-mails, calendars, and contacts, scheduling meetings, and notifying applications about changes in signal strength and battery power. Microsoft specifically names two Motorola devices, the Droid 2 and the Charm, but says these are just examples and not a comprehensive list.

The suit comes just as Microsoft readies the release of its Windows Phone 7 mobile operating system, the successor to Windows Mobile. Motorola was once a big backer of Windows Mobile, but in recent years it has shifted to Google's Android. Although manufacturers can use Android for free, Microsoft argues that phone makers should consider the potential patent infringement issues and the related costs of the mobile OS.

The nine patents in question in the ITC complaint include:

• 5,579,517: Common name space for long and short filenames
• 5,758,352: Common name space for long and short filenames
• 6,621,746: Monitoring entropic conditions of a flash memory device as an indicator for invoking erasure operations
• 6,826,762: Radio interface layer in a cell phone with a set of APIs having a hardware-independent proxy layer and a hardware-specific driver layer
• 6,909,910: Method and system for managing changes to a contact database
• 7,644,376: Flexible architecture for notifying applications of state changes
• 5,664,133: Context sensitive menu system/menu behavior
• 6,578,054: Method and system for supporting off-line mode of operation and synchronization using resource state information
• 6,370,566: Generating meeting requests and group scheduling from a mobile device

"We have a responsibility to our customers, partners, and shareholders to safeguard the billions of dollars we invest each year in bringing innovative software products and services to market," Horacio Gutierrez, Microsoft's corporate vice president and deputy general counsel of Intellectual Property and Licensing, said in a statement. "Our action today merely seeks to ensure respect for our intellectual property rights infringed by Android devices; and judging by the recent actions by Apple and Oracle, we are not alone in this respect," he added in a Microsoft on the Issues blog post.

Apple earlier this year claimed that HTC's Android (and Windows Mobile) handsets violate a number of its patents. To avoid a similar fight with Redmond, HTC paid Microsoft for patent licenses. Regardless of the outcome of the HTC vs. Apple battle-turned-war, Android incurred costs for HTC, in spite of its free licensing.

It's next to impossible to build a mobile device nowadays without extensive licensing agreements. Microsoft provides companies using Windows Mobile and Windows Phone operating systems with patent protections, while Google simply provides moral support. When Microsoft made the "Android isn't free" allegations, it was widely assumed that the software giant was referring to HTC's legal problems. With today's attack on Motorola, it's clear that Microsoft had more than just HTC on its mind.