Another day, another lawsuit. Nokia has announced the filing of yet another lawsuit against Apple, in Federal District Court in Wisconsin, regarding five of Nokia’s patents. Nokia says those patents are infringed by the iPhone and iPad 3G and involve technology that improves speech and data transmission with new antenna configurations and positioning of data in applications.

“Nokia has been the leading developer of many key technologies in mobile devices” Nokia’s Patent Licensing General Manager Paul Melin said in a statement. "We have taken this step to protect the results of our pioneering development and to put an end to continued unlawful use of Nokia’s innovation.”

But this is merely the latest shot in the legal battle between Apple and Nokia. Here's the background (take notes; there'll be a test later): in February it was announced that Apple's patent-infringement complaint seeking to block Nokia Oyj’s phone imports into the U.S. will be investigated by a U.S. trade agency.

In January Nokia filed yet a patent lawsuit against Apple, alleging that the company violates 10 of its US patents related mostly to smartphone technology. Also in January, Nokia filed a complaint with the United States International Trade Commission (ITC) alleging that Apple infringes Nokia patents in virtually all of its mobile phones, portable music players, and computers.

This followed -- are you paying attention? -- an Nokia complaint filed in October Nokia against Apple with the Federal District Court in Delaware, alleging that Apple's iPhone infringes Nokia patents for GSM, UMTS and wireless LAN (WLAN) standards. Basically, Nokia claimed that Apple wasn't paying licensing fees for the wireless technologies it uses in the iPhone, iPhone 3G and iPhone 3GS.

On Dec. 11, Apple filed a countersuit claiming that Nokia is infringing 13 Apple patents. “Other companies must compete with us by inventing their own technologies, not just by stealing ours,” said Bruce Sewell, Apple’s General Counsel and senior vice president.