By Supantha Mukherjee

STOCKHOLM, (Reuters) – Sweden’s Ericsson has brought another patent infringement suit against Apple (NASDAQ) as part of a latest dispute between the companies regarding royalty payments for the use of 5G wireless Patents in iPhones.

Due to the failure of negotiations over renewal of seven-year telecom patent licensing contracts, the two companies are already suing each other in America.

Ericsson first sued Apple in October, alleging that Apple tried to inadvertently reduce royalty rates. Meanwhile, Ericsson filed a lawsuit against Apple in December accusing it of using “strong arm tactics” to renew patents.

Ericsson spokesperson said that Apple has now used its technology “since the previous agreement expired and we were unable to agree on the terms of a new licence.”

Apple didn’t immediately reply to our request for comment.

Companies that are involved in technology often file patent suits. Each dollar they save could be significant over the life of their agreement. Ericsson charges $5 to $5 per handset for 5G.

This Swedish firm invests approximately $5 billion annually in research and has more than 57,000 patents. The royalties it receives from patents account for about a third its operating profit.

Ericsson (KS:), settled patent litigations last year after several months-long court battles which temporarily affected its quarterly earnings. After settlement, any pending dues will usually be paid.