Microsoft has filed a complaint against Motorola for nine alledged patent infringements in its Android phones.
In US law, it is permissible to go after companies implementing the phones rather than trying to work things out with the operating system developer, in this case Google.
The claims relate to patents covering the synchronising emails, contacts and calendars, and systems for notifying applications of signal strength fluctuations and battery power status.
"The key value proposition of smartphones has moved from the radio stack to the software stack, as people buy smartphones because they are fully functional computers that fit in the palm of your hand," said Horacio Gutierrez, corporate vice president and deputy general counsel for Microsoft, in a blog post.
"With this shift, it is imperative that companies address IP [intellectual property] issues related to the software that makes possible this new class of devices."
Motorola makes use of Microsoft Exchange ActiveSync to synchronise calendar tasks and email in its Droid handsets. How far Microsoft will push other Android franchise phone makers depends on implementation and the nature of the patents that Microsoft is holding.
This is the third attack on Android this year. Oracle wanted its piece of Android action for alleged infringements of Java patents and both Apple and Microsoft had a go at HTC over patents.
The fear for the open source operating system is its low-cost status is now in peril as licensing costs resulting from patents compliance mount up before it can be rolled out into a phone.
In its press release about the Motorola case, Gutierrez wrote: "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."
He added: "Motorola needs to stop its infringement of our patented inventions in its Android smartphones."
