Netherlands-headquartered KPN reportedly filed a patent infringement case against Swedish vendor Ericsson, alleging violations of five patents involving wireless network functions.

Reuters reported the operator filed a complaint with a US court claiming it offered to licence the patents, but Ericsson declined to take up the option.

There were apparently no further details in the filing, other than KPN stating it was seeking monetary compensation.

The spat comes close to six months after KPN signed a major five-year deal with Ericsson for its core 5G network, a move which came at Huawei’s expense.

At the time, Ericsson highlighted a century-long working relationship with KPN, an assertion which suggests the operator did not act lightly when initiating the US legal action.

It also puts Ericsson on the flip-side of the coin in terms of patent lawsuits, with the vendor more accustomed to being the pursuer of alleged infringements.

The company is in the throes of action against Samsung in the US, over claimed violation of contractual commitments on 4G and 5G patent royalties. Ericsson estimates the delayed royalty payments and litigation costs could impact its quarterly operating income by between SEK1 billion (US$120.1 million) and SEK1.5 billion from Q1 2021