Nokia and Qualcomm have entered a new round in their high-stakes fight over patent royalties, with the Finnish handset maker landing its first counter-punch.

The Finnish company has responded to the patent infringement lawsuit filed by Qualcomm in the Western District of Wisconsin on April 2 by claiming that its products aren't infringing, and filing its first patent counter-suit against the US chip company, Nokia said on Thursday. Nokia's suit seeks damages and also an injunction against certain of Qualcomm's chipsets.

"We're confident that our products don't infringe the two Qualcomm patents that are in suit and, in fact, we believe these patents are invalid," a Nokia spokeswoman said.

The initial lawsuit filed by Qualcomm in Wisconsin concerns two patents covering speech encoders used in certain GSM (Global System for Mobile Communications) mobile phones to digitise audio signals for transmission, and is part of a series Qualcomm patent claims against Nokia going back at least to 2005.

In its counter-suit, Nokia accuses Qualcomm of infringing six of its patents, relating primarily to multiband and multimode technologies that reduce handset and chipset size, cost and power consumption.

Standards bodies divide patents touching on the technologies they define into two categories: those essential to a standards-compliant product, and those that only cover a particular implementation of the standard.

The six patents Nokia accuses Qualcomm of infringing are implementation patents, the spokeswoman said.

Companies with essential patents included in a standard agree to license the technology under fair, reasonable and non-discriminatory terms, but the companies can decide whether or not to license implementation patents to others, she said. Qualcomm had no agreement to use the six Nokia implementation patents, she said.

Qualcomm has copied these innovations and made them available to its chipset customers, according to the Nokia spokeswoman.

In April, Qualcomm filed another lawsuit against Nokia in the US District Court for the Eastern District of Texas. The separate lawsuit deals with three patents related to the downloading of applications and other digital content over GPRS (General Packet Radio Service) or EDGE (Enhanced Data Rates for GSM Evolution) networks, two technologies for speeding the transmission of packet data in GSM networks.

The Nokia spokeswoman declined to comment on the Texas lawsuit.

Over the past 19 months, Qualcomm has filed 11 patent litigation cases against Nokia but in none of these cases has the company had any success, according to the spokeswoman.

Legal disputes over mobile phone patents have grown in recent years, largely because of opportunities to generate significant revenue from licensing inventions to others. Numerous patent licensing disputes have accompanied mobile phone technologies such as GSM and WCDMA (Wideband Code Division Multiple Access), and are expected to flow from 4G (fourth-generation) systems now under development.

In a interview earlier this month, Bill Davidson, senior vice president of investor relations and international marketing at Qualcomm, said the company has more than 1,000 essential patents for OFDM, OFDMA (OFDM Access) and MIMO (Multiple Input Multiple Output) technologies, all of which form the foundation of new 4G technologies, whether WiMax, LTE (Long-Term Evolution) or UMB (Ultra Mobile Broadband).