The Nortel patents cover technologies related to 4G, data networking, optical, voice, Internet and semiconductors, Nortel has said.

Nortel has been selling off assets since it filed for bankruptcy protection in January 2009. It has sold its CDMA (Code-Division Multiple Access) wireless division to Ericsson for more than $1 billion and its enterprise networking business to Avaya for just under $1 billion.

The DOJ, which often does not comment on investigations, did not immediately reply to questions on Friday. Neither Google nor Apple replied to requests for comment.

The IDG News Service