Ericsson v. Micromax: A Closer Look at the Speech Codec Patents
Background Ericsson initiated patent infringement proceedings against Micromax Informatics Ltd. and Mercury Electronics Ltd., alleging infringement of patents relating to speech codec technology — the combined use of a speech coder and speech decoder to compress a caller's voice signal, transmit it as coded speech frames over a radio link, and decode it at the receiving end. A notable feature of this technology is discontinuous transmission: during periods when the speaker is inactive, no coded speech frames are sent; instead, the transmitter periodically sends speech parameters sufficient for the decoder to generate "comfort noise" in place of silence. According to Ericsson's own patent specifications, speech coders and decoders are conventionally built into radio transmitters and receivers respectively, working together to enable voice communication over a radio link. A mobile phone, in this framing, is simply a conventional radio communication device — a radi...