TurboCode LLC v. AT&T Mobility LLC

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: TurboCode LLC (Texas)
  • Defendant: AT&T Mobility LLC (Delaware)
  • Plaintiff’s Counsel: DINOVO PRICE LLP
• Case Identification: 2:23-cv-00375, E.D. Tex., 08/21/2023
• Venue Allegations: Plaintiff alleges venue is proper in the Eastern District of Texas because AT&T maintains a "regular and established" physical presence in the district, including retail stores, cellular base stations, and an "AT&T Foundry" research and development facility. The complaint also notes that AT&T has previously admitted or not contested that this district is a proper venue for patent infringement actions.
• Core Dispute: Plaintiff alleges that Defendant's mobile devices and services that comply with 3G and 4G/LTE cellular standards infringe a patent related to a high-speed, efficient architecture for turbo code decoders.
• Technical Context: The technology involves turbo codes, a class of high-performance forward error correction codes used in modern telecommunications like 3G and 4G/LTE to ensure reliable data transmission in noisy wireless environments.
• Key Procedural History: The complaint alleges that Plaintiff provided Defendant with formal notice of infringement on October 18, 2021. It also states that Plaintiff has previously enforced its rights in the patent-in-suit against other third parties. A reexamination certificate for the patent-in-suit was issued, which amended the asserted claims.

Case Timeline

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 6,813,742 - High speed turbo codes decoder for 3G using pipelined SISO log-map decoders architecture, issued November 2, 2004

The Invention Explained

• Problem Addressed: The patent describes that prior art turbo code decoders, while effective, were often based on the MAP (Maximum a Posteriori) algorithm, which required computationally intensive multiplications and additions. This complexity made such decoders costly, power-hungry, and difficult to implement efficiently in semiconductor (ASIC) devices for mass-market mobile communications. (’742 Patent, col. 2:48-61).
• The Patented Solution: The invention discloses a decoder architecture that uses two pipelined Log-MAP (Logarithmic MAP) decoders. This approach replaces complex multiplication operations with simpler binary adders, which are more suitable for high-speed, low-power ASIC implementation. (’742 Patent, col. 2:54-58). The pipelined structure, illustrated in the patent’s Figure 4, allows for iterative decoding where one decoder can process data while the other is also active, enabling a decoded output to be produced on each clock cycle, thereby increasing data throughput. (’742 Patent, Abstract; col. 2:45-50).
• Technical Importance: The described architecture aimed to make high-performance turbo decoding practical for the emerging 3G cellular market by reducing hardware complexity, power consumption, and cost, while delivering the high data speeds required. (’742 Patent, col. 2:32-40).

Key Claims at a Glance

• The complaint asserts independent method claim 6. The language below is from the post-reexamination amended version of the claim.
• Independent Claim 6 (amended): A method of iteratively decoding a plurality of sequences of received baseband signals, comprising the steps of:
  • providing an input buffer with at least three shift registers for receiving an input signal and generating first, second, and third shifted input signals;
  • providing first and second soft decision decoders in a circular circuit, where the decoders process soft decision data from a preceding decoder, and where the decoders also receive the shifted input signals from the input buffer;
  • providing at least one memory module coupled to the output of each decoder, where the second decoder's associated memory output is fed back to the first decoder's input;
  • processing systematic and extrinsic information data using a maximum a posteriori (AP) probability algorithm and/or a logarithm approximation algorithm;
  • generating a soft decision based on the MAP or logarithm approximation algorithm;
  • weighing and storing the soft decision information into the corresponding memory module; and
  • performing iterative decoding for a predetermined number of times, where an output from the last decoder is fed back to the first decoder to propagate through the decoders in a circular circuit.
• The complaint notes that infringement of dependent claims is also being asserted (Compl. ¶41).

III. The Accused Instrumentality

Product Identification

• The complaint identifies the "Exemplary Accused Products" as the iPhone SE, Pixel 4a, Galaxy A11, and LG K4, as well as other 3G and 4G/LTE devices sold, supported, or used by AT&T (Compl. ¶23, ¶41).

Functionality and Market Context

• The accused products are mobile communication handsets that operate on 3G and/or 4G/LTE networks (Compl. ¶23). The complaint alleges that these products, by complying with the 3rd Generation Partnership Project (3GPP) standards for cellular communication, necessarily perform a method of iterative decoding to process received signals (Compl. ¶34, ¶35). The infringement allegations are based on the functionality mandated by these industry standards, which call for using a turbo decoder architecture to ensure reliable communication (Compl. ¶36, ¶38). The complaint provides screenshots of the technical specifications for the accused products, such as for the iPhone SE, to demonstrate their compliance with the relevant 3G and 4G/LTE standards (Compl. ¶25, p. 6).

IV. Analysis of Infringement Allegations

The complaint’s infringement theory centers on the allegation that compliance with the 3GPP standard for turbo decoding constitutes practice of the claimed method. The complaint includes "Figure 18: Turbo decoder," a diagram from a 3GPP technical specification, as representative of the infringing method performed by the accused products (Compl. ¶35, p. 8).

’742 Patent Infringement Allegations

• Identified Points of Contention:
  • Scope Questions: A primary question may be whether compliance with the 3GPP standard, which provides a functional block diagram for a turbo decoder, is sufficient to establish that an accused device practices every limitation of the asserted method claim. The defense may argue that the standard allows for multiple implementations, not all of which would read on the specific combination of steps in claim 6.
  • Technical Questions: The complaint relies on public standards and academic papers rather than direct technical analysis of the accused products' hardware. A central evidentiary question will be what proof demonstrates that the specific decoder implementations within the accused products' processors actually operate in the manner required by the claim, particularly concerning the specific routing of signals from an input buffer and the "weighing and storing" of soft decision information.

V. Key Claim Terms for Construction

• The Term: "soft decision decoder"

• Context and Importance: This term defines the core processing engines of the invention. The scope of this term is critical because it will determine what types of decoder architectures fall within the claim. Practitioners may focus on this term because, while the claim is not explicitly limited to a "Log-MAP" decoder, the patent specification heavily emphasizes the "Log-MAP" architecture as the key inventive improvement over the prior art.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: The claim language itself requires a decoder that implements a "maximum a posteriori (MAP) probability algorithm, and/or a logarithm approximation algorithm" (’742 Patent, col. 10:17-21, Re-exam Cert.). This language is not expressly limited to the specific "Log-MAP" embodiment.
  • Evidence for a Narrower Interpretation: The patent’s title, abstract, and detailed description repeatedly identify the invention as using "pipelined SISO Log-MAP decoders." A party could argue that the claims should be interpreted in light of this consistent disclosure, which is presented as the solution to the problems of prior art MAP decoders. (’742 Patent, Abstract; col. 2:40-42).

• The Term: "circular circuit"

• Context and Importance: This term describes the iterative feedback structure that is fundamental to turbo decoding. The definition will determine the structural and functional requirements of the feedback loop.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: The term could be interpreted to cover any arrangement where the output of a later-stage decoder is fed back as an input to an earlier-stage decoder to enable iterative processing, as is generally understood in the art and depicted in the 3GPP diagram. (Compl. ¶35).
  • Evidence for a Narrower Interpretation: The patent describes a specific "pipelined scheme" where two decoders function concurrently, with one decoding data from a de-interleaver memory while the other decodes data from an interleaver memory. (’742 Patent, Abstract; col. 2:45-50). A party could argue "circular circuit" should be construed to require this specific pipelined implementation.

VI. Other Allegations

• Indirect Infringement: The complaint alleges both induced and contributory infringement by AT&T since at least the date it received notice, October 18, 2021 (Compl. ¶42, ¶43). The inducement allegation is based on AT&T allegedly encouraging and instructing its customers to use the accused products in an infringing manner according to its specifications (Compl. ¶42). The contributory infringement allegation claims the accused products are a material component especially adapted for infringement and not a staple article of commerce (Compl. ¶43).
• Willful Infringement: Plaintiff seeks enhanced damages for willful infringement, alleging that Defendant’s infringement continued after it had knowledge of the ’742 Patent, at least as of the October 18, 2021 notice date (Compl. ¶42; p. 13, ¶c).

VII. Analyst’s Conclusion: Key Questions for the Case

• A key evidentiary issue will be one of implementation versus specification: will proof of compliance with the 3GPP standard be sufficient to demonstrate infringement of the specific method steps recited in the amended claim, or will the court require direct evidence from the accused products’ internal architecture and operation?
• The case will likely involve a core question of claim scope: can the term "soft decision decoder" be construed to cover any decoder using a MAP-type algorithm as recited in the claim, or will its meaning be narrowed by the patent’s repeated and specific disclosure of a "Log-MAP" decoder as the invention’s central contribution?
• The complaint’s theory raises a potential question of divided infringement: given that end-users operate the accused mobile devices, can the plaintiff prove that AT&T directs or controls those users' actions in a manner that satisfies the legal requirements for holding AT&T liable for the performance of the entire multi-step method claim?