The relationship between two former wireless service partners just got frostier.

Cox Communications Inc. filed a countersuit against Sprint Corp. (NYSE: S) on Tuesday alleging that the wireless operator is infringing on two MSO patents while also seeking to invalidate 12 Sprint patents that are the subject of a separate lawsuit that Sprint has brought against Cox and other cable operators.

Cox's suit, filed with the District Court of Delaware, claims that Sprint is infringing on two MSO patents: No. 7,992,172 ("Method and System for Multicast Using Multiple Transport Streams") and No. 7,836,474 ("Method and Apparatus for Preprocessing and Postprocessing Content in an Interactive Information Distribution System"). Cox obtained the '172 patent in August 2011, and the '474 patent in November 2010, according to court documents obtained by Light Reading Cable.

In plainer English, Cox says the patents detail new ways to deliver broadcast and cached video to customers across a network. The MSO claims Sprint is using the MSO's intellectual property for services like Sprint TV, the carrier's subscription-based mobile TV service that it delivers, in part, via MobiTV Inc. 's converged media platform.

Why this matters
It's another example of fallout that occurs when business partners are on the outs. Sprint and Cox began to back away from their mobile partnership last year, and Cox is now bound to Verizon Wireless via a services bundling deal and a proposed sale of Cox's Advanced Wireless Services (AWS) spectrum to Verizon Wireless.

Cox's countersuit follows a lawsuit from Sprint claiming that Cox, along with Comcast Corp. (Nasdaq: CMCSA, CMCSK), Time Warner Cable Inc. (NYSE: TWC) and Cable One Inc. , is infringing on 12 Sprint patents related to VoIP technology. Comcast, another former Sprint partner, has filed a separate against Sprint over patents tied to mobile messaging apps.

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— Jeff Baumgartner, Site Editor, Light Reading Cable