Court papers filed by Nokia claim Nokia has paid Qualcomm around $1 billion over 15 years to gain access to the chip maker’s early mobile technology patents. The papers, filed in a Delaware court, say the patents are now paid up and royalty-free, according to the terms of 1992 and 2001 agreements with Qualcomm.

A technology license pact expired on April 9, 2007, and the two companies have been fighting ever since. Analysts estimate that Nokia pays around $500 million a year for use of Qualcomm patents and it wants to reduce the sum.

Qualcomm bases its claim on the fact that Nokia continues to ship products that use Qualcomm patents, and therefore the patent lease continues on the same terms as those in the written agreements. Nokia says the cross-licensing agreement can only be extended in writing and that it has paid for the patent in full.

The companies have not disclosed the timeframe of so-called “early” patents, which stem from Qualcomm’s time as the leading developer of CDMA wireless technology.

CDMA technology, which is used in the United States and some Asian countries, failed to gain global adoption when competing against European GSM technology. But it has gained wider adoption in third-generation forms.

Nokia and Qualcomm have over a dozen legal fights pending in courts on three continents. Analysts see these cases as efforts by both companies to gain leverage over the other in an eventual license-pact renewal.