With Sprint's legal battle against AT&T's merger with T-Mobile effectively at an end, the operator is turning its attention to cable operators.
Sprint is suing Comcast, Time Warner Cable, Cox Communications and Cable One for violating its patents on technology that routes voice calls over a packet-based network instead of expensive public landline networks.
The complaints were filed separately Monday in the U.S. District Court in Kansas City, Kan., Sprint's home state.
The suits allege that the four cable operators are infringing on 12 of Sprint's patents on its voice-over-packet technology. Sprint says late employee Joe Christie developed a way to leverage packet-based networks for voice calls in the 1990s, helping to build a portfolio of more than 120 issued U.S. patents on the technology.
"Unfortunately, many companies in the industry … have realized the great value in this technology and have misappropriated it without Sprint’s permission," Sprint said in its complaint.
Sprint is asking for unspecified damages and wants the court to ban the cable companies from selling services it says violate its intellectual property rights, including Time Warner's Digital Home Phone and Comcast's Xfinity Voice.
The cable companies named in the complaint could not be immediately reached for comment.
The patents at question in Sprint's latest suit were the subject of a 2007 complaint against Vonage. Sprint won that case after the jury found that Vonage had violated six of its patents on the voice technology and awarded Sprint $69.5 million in damages. Vonage later paid Sprint $80 million to license its portfolio of voice-over-packet patents.
Sprint has successfully sued a number of other companies over the patents and has reached settlements with Paetec, Broadvox, Big River Telephone and Nuvox. A number of other unnamed companies also license Sprint's voice-over-packet patents.