Linkplay Technology Inc v. Sonos Inc

1. Case Identification

• Case #: IPR2025-00511
• Patent #: 9,213,357
• Filed: February 4, 2025
• Petitioner(s): Linkplay Technology Inc.
• Patent Owner(s): Sonos, Inc.
• Challenged Claims: 1-20

2. Patent Overview

• Title: Method and Apparatus for Multi-Zone Digital Audio System
• Brief Description: The ’357 patent relates to a system where a first playback device obtains audio content from a source outside a local area network (LAN). The first device then transmits the audio, along with associated playback timing and device clock information, to a second playback device over the LAN for synchronous playback.

3. Grounds for Unpatentability

Ground 1: Anticipation and Obviousness of Claims 1-20 over Richenstein

• Prior Art Relied Upon: Richenstein (Application # US 2003/0083024).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Richenstein anticipates or, at a minimum, renders obvious all challenged claims. Richenstein discloses a networked audio system where an audio device (the "first playback device") can be controlled by a remote network device over a local network. This audio device obtains content, such as a voice stream, from a source outside the LAN (e.g., cellular telephone 805). It then transmits this audio information in formatted data packets to a "second playback device" (e.g., speakers or headsets) for synchronous playback. Petitioner asserted these packets explicitly contain audio data, playback timing information (e.g., calibration sections and sync signals), and device clock information (for clock recovery by the receiving device), meeting all limitations of the independent claims.
  • Motivation to Combine (for §103 grounds): To the extent any limitation is not explicitly disclosed, Petitioner argued it would have been obvious to a person of ordinary skill in the art (POSITA) to implement it. For instance, using known data packet structures to combine audio with timing and clock information for synchronized playback was a well-understood technique.
  • Expectation of Success (for §103 grounds): A POSITA would have had a high expectation of success in making any minor modifications, as the underlying principles of networked audio synchronization were well-established.

Ground 2: Obviousness of Claims 4-7 and 12-17 over Richenstein in view of MOST-2.0

• Prior Art Relied Upon: Richenstein (Application # US 2003/0083024) and MOST-2.0 (MOST Specification Rev. 2.0).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground addressed dependent claims related to a "synchrony group." Petitioner argued Richenstein explicitly teaches that its system can operate according to the Media Oriented Systems Transport (MOST) standard. MOST-2.0, a contemporaneous specification document for that standard, describes grouping devices into a synchrony group, assigning master and slave roles, and transmitting status information about the group. This status information includes the identity of each playback device and which device serves as the master, thereby teaching the limitations of the challenged dependent claims.
  • Motivation to Combine: A POSITA would combine these references because Richenstein provides the express motivation to use the MOST standard. Implementing the specific grouping, status reporting, and master/slave identification functions from the MOST-2.0 specification would be a predictable and logical way to manage the synchrony group in Richenstein’s system.
  • Expectation of Success: There was a reasonable expectation of success because the combination involved implementing a publicly available industry standard (MOST-2.0) into a system that was expressly designed to be compatible with it (Richenstein).

Ground 3: Obviousness of Claims 1-20 over Chatterton in view of RFC1889

• Prior Art Relied Upon: Chatterton (Patent 7,116,894) and RFC1889 (RTP: A Transport Protocol for Real-Time Applications).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner contended Chatterton’s Home Media Server 110 acts as a "first playback device" that receives commands from a network device (e.g., a PC) to obtain audio from an external source (e.g., internet channels). Chatterton expressly discloses using the Real-time Transport Protocol (RTP) to create and transmit data streams for synchronous playback to "second playback devices" (e.g., multimedia nodes). RFC1889, as the defining standard for RTP, provides the technical details for embedding timestamping (playback timing information) and clock data via RTCP sender reports (device clock information) within these streams to ensure proper synchronized playback.
  • Motivation to Combine: A POSITA would combine these references because Chatterton explicitly states it uses the RTP protocol. It would have been obvious and necessary for a POSITA implementing Chatterton's system to consult the RFC1889 standard to understand and apply the specific techniques for timestamping and clock synchronization required for the system to function as described.
  • Expectation of Success: A POSITA would have had a high expectation of success, as the combination merely involves applying the detailed, standard-defined techniques of RFC1889 to the system in Chatterton that expressly calls for their use.
• Additional Grounds: Petitioner asserted additional anticipation and obviousness challenges based on Chatterton alone.

4. Key Claim Construction Positions

• Petitioner argued that the claim terms do not require explicit construction and can be given their plain and ordinary meaning. However, Petitioner also considered constructions for terms such as "playback timing information" and "independently clocked" that were adopted in a prior district court litigation. Petitioner contended that even under these previous constructions, the asserted prior art discloses all challenged claim limitations.

5. Arguments Regarding Discretionary Denial

• §325(d) (Same or Substantially Same Arguments): Petitioner argued that discretionary denial under §325(d) is unwarranted because the primary references—Richenstein, Chatterton, and MOST-2.0—were never presented to or considered by the USPTO during prosecution or reexamination. While RFC1889 was previously cited, it was part of a fourteen-reference combination that was not substantively addressed, and its specific application to Chatterton is a new argument.
• §314(a) (Fintiv Factors): Petitioner asserted that the Fintiv factors strongly favor institution. The petition presented a compelling unpatentability challenge based on single-reference anticipation and obviousness grounds (Factor 6). Furthermore, the trial in the co-pending litigation is likely to occur after the Final Written Decision (FWD) deadline (Factor 2), and the parties' investment in that litigation has been minimal, with claim construction not yet underway (Factor 3).

6. Relief Requested

• Petitioner requests institution of an inter partes review (IPR) and cancellation of claims 1-20 of the ’357 patent as unpatentable.