Ericsson's lawsuit follows a complaint filed by Apple on Monday, which claimed that Ericsson was demanding excessive royalties for its LTE patents. Apple also said that the patents concerns were inessential for meeting cellular industry standards for this high-speed mobile internet.
Apple denies infringing Ericsson's patents, but asked that if the court found that an infringement had occurred, that subsequent royalty payments be "reasonable". The Cupertino, CA-based technology giant's lawsuit was filed in the U.S. District Court for Northern California on Monday.
Patent infringement cases are not unusual in the mobile industry. A court ordered Chinese smartphone maker Xiaomi to stop selling phones in India last month, after Ericsson accused it of infringing patents.
And In 2011, Apple agreed to pay Finnish telecoms equipment maker Nokia an undisclosed fee over a patent dispute.
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