PTAB

IPR2024-01061

DirecTV LLC v. Entropic Communications LLC

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Petition
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1. Case Identification

2. Patent Overview

  • Title: Method for Determining a Common Bit-Loading Modulation Scheme
  • Brief Description: The ’759 patent describes a method for use in a broadband cable network ("BCN") where multiple nodes determine a common bit-loading modulation scheme for broadcasting messages. This involves a transmitting node sending a probe signal and receiving nodes replying with their optimal modulation schemes, from which a common scheme, viable for all receiving nodes, is determined.

3. Grounds for Unpatentability

Ground 1: Claims 1-3 are obvious over Carhart in view of Grube.

  • Prior Art Relied Upon: Carhart (Patent 6,622,304) and Grube (Patent 5,495,483).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Carhart discloses the foundational network structure—a BCN with a central computer communicating with multiple remote devices using existing coaxial cables. Grube, in turn, teaches the claimed method of determining a common modulation scheme. Grube discloses a primary site sending a "training signal" (the claimed "probe signal") to multiple secondary sites. Each secondary site analyzes the signal to create its own "bit loading table" and sends this information back to the primary site. The primary site then generates a "lowest common denominator (LCD) bit loading table" by comparing the tables from all secondary sites and selecting the lowest bit-loading value for each channel, which corresponds to the claimed "common bit-loading modulation scheme."
    • Motivation to Combine: Petitioner asserted a person of ordinary skill in the art (POSITA) would combine Carhart's network with Grube's method to improve network reliability and optimize bandwidth. Carhart provides the network but is agnostic about the specific modulation scheme. A POSITA would have sought an efficient method like Grube's Discrete Multi-Tone (DMT) modulation to ensure reliable communication among Carhart's multiple devices. Grube's technique of establishing a common scheme based on the worst-performing channel path directly addresses the problem of broadcasting to multiple nodes with varying channel characteristics, a problem inherent in Carhart's system.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success because implementing Grube's well-known DMT modulation and channel characterization techniques in Carhart's standard coaxial cable network was a straightforward application of known principles to achieve a predictable result—reliable multi-node communication.

Ground 2: Claims 1-3 are obvious over Carhart in view of Grube and Shibutani.

  • Prior Art Relied Upon: Carhart (Patent 6,622,304), Grube (Patent 5,495,483), and Shibutani (Application # 2003/0002518).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground built upon Ground 1, adding Shibutani to explicitly supply well-known metrics for measuring channel characteristics. While Grube taught determining a "spectral response" to create bit-loading tables, Shibutani explicitly disclosed using metrics like signal-to-noise ratio (SNR) and bit-error rate (BER) for the same purpose. The dependent claims require measuring transmission characteristics using SNR (claim 1), BER (claim 2), or packet-error rate ("PER") (claim 3). Petitioner argued Shibutani taught using pilot symbols (analogous to Grube's training signals) to measure channel conditions, including SNR and BER, to select an appropriate modulation scheme.
    • Motivation to Combine: A POSITA, implementing Grube's method in Carhart's network, would have understood that Grube's "spectral response" was a general concept for channel characterization. To improve performance and reduce computational complexity, a POSITA would have been motivated to substitute or supplement Grube's general method with the more specific, efficient, and well-known metrics disclosed in Shibutani. Shibutani's use of SNR and BER provides a more complete picture of channel quality, accounting for noise and other factors beyond simple signal attenuation, leading to more reliable communication.
    • Expectation of Success: A POSITA would have expected success in using Shibutani's metrics, as they were standard in the art for channel quality assessment. Applying these known measurement techniques to Grube's channel characterization step was a simple design choice that would predictably improve the robustness of the combined Carhart-Grube system.

  • Additional Grounds: Petitioner asserted additional obviousness challenges against claim 1 over Carhart, Grube, and Cai (Patent 6,205,410), and against claims 2-3 over Carhart, Grube, Shibutani and/or Cai, and further in view of Flammer (Patent 6,480,497). These grounds introduced Cai and Flammer to provide further evidence that using SNR and PER, respectively, to optimize bit-loading schemes in communication networks was conventional and well-understood.

4. Arguments Regarding Discretionary Denial

  • Discretionary Denial under Fintiv: Petitioner argued against discretionary denial under Fintiv because there is a co-pending litigation but no trial date has been set. The median time to trial in the district court significantly exceeds the statutory deadline for a Final Written Decision (FWD) in an inter partes review (IPR), meaning the IPR would conclude well before any potential trial.
  • Denial under §325(d): Petitioner contended that denial under §325(d) was unwarranted because the petition raised new combinations of prior art that were not before the Examiner during prosecution. The Examiner primarily relied on wireless networking references (Ling and Li), whereas the current petition focused on references directly pertinent to the claimed BCN environment and methods for determining common modulation schemes, arguing the Examiner erred in allowing the claims.

5. Relief Requested

  • Petitioner requested institution of an IPR and cancellation of claims 1-3 of the ’759 patent as unpatentable.