Nokia Oyj sued Apple Inc. saying the iPhone maker infringed several mobile patents, turning simmering tension between the companies into a bitter public legal battle on multiple fronts. The Espoo, Finland-based company said Apple agreed to license patented inventions in 2011 but has refused to extend those agreements that are now expiring. Nokia filed complaints with the German Regional Courts in Dusseldorf, Mannheim and Munich, and in federal court in Texas. “This is a big deal, especially for the future of licensing revenues on standard-essential patents," Bloomberg Intelligence litigation analyst Matt Larson said, referring to patents that must be used to comply with technical industry standards like Wi-Fi. “Apple has regularly fought to keep royalty rates low, whereas Nokia is interested in getting as much value from its intellectual property as possible." The dispute is rooted in Nokia’s demise as the world’s largest phone maker. Since selling its handset business, the company has focused on networking. It’s now tapping its patent portfolio as a source of income, rather than as a cross-licensing tool to protect its own products. Nokia’s intellectual property business added patents through its Alcatel-Lucent acquisition, making it a more significant profit contributor. In the third quarter, Nokia’s technology unit, which licenses its patents, generated about 40 per cent of the company’s total adjusted operating profit. (Nate Lanxon, Ian King and Joel Rosenblatt/Bloomberg)