TurboCode LLC v. Coolpad Group Ltd

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: TurboCode LLC (Texas)
  • Defendant: Coolpad Group Limited (Cayman Islands)
  • Plaintiff’s Counsel: Direction IP Law
• Case Identification: 2:25-cv-00174, E.D. Tex., Filed 02/13/2025
• Venue Allegations: Venue is alleged to be proper in the Eastern District of Texas on the basis that Defendant has committed acts of patent infringement within the district.
• Core Dispute: Plaintiff alleges that Defendant’s 4G/LTE-compliant mobile devices and related cellular equipment infringe a patent related to high-speed, efficient architectures for Turbo Code decoders.
• Technical Context: The technology at issue is error correction coding, a fundamental process for ensuring data integrity and transmission speed in modern wireless communication standards like 4G/LTE.
• Key Procedural History: The sole patent-in-suit was the subject of an ex parte reexamination requested in 2006. An Ex Parte Reexamination Certificate was issued in 2009, which amended the asserted claim and may influence its interpretation and scope.

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

• Patent Identification: 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’s background section states that prior art Turbo Code decoders, while effective, were computationally intensive, requiring complex multiplications and additions that made them costly, slow, and power-hungry for implementation in consumer wireless devices (’742 Patent, col. 2:6-22).
• The Patented Solution: The invention proposes a more efficient decoder architecture that uses two pipelined Soft-In/Soft-Out (SISO) Log-MAP decoders operating in a feedback loop. This architecture aims to increase data throughput by allowing one decoder to process data while the other handles input/output tasks. By performing calculations in the logarithmic domain ("Log-MAP"), the design replaces complex multipliers with simpler binary adder circuits, reducing hardware complexity and power consumption (’742 Patent, Abstract; col. 2:39-52; FIG. 4).
• Technical Importance: This type of architectural simplification was aimed at making powerful Turbo Code error correction practical and economical for mass-market 3G wireless devices, which have strict cost and power constraints (’742 Patent, col. 2:23-29).

Key Claims at a Glance

• The complaint asserts independent claim 6, as amended by the Ex Parte Reexamination Certificate (Compl. ¶12).
• The essential elements of independent claim 6 are:
  • A method of iteratively decoding a plurality of sequences of received baseband signals.
  • Providing an input buffer with at least three shift registers to generate first, second, and third shifted input signals.
  • Providing first and second soft decision decoders serially coupled in a circular circuit, where each decoder processes soft decisions from the preceding decoder, with specific inputs from the input buffer.
  • Providing at least one memory module coupled to the output of each decoder, where the output from the second decoder’s memory module is fed back as an input to the first decoder.
  • Processing systematic and extrinsic information data using a maximum a posteriori (MAP) or equivalent logarithm approximation algorithm.
  • Generating a soft decision based on the MAP or equivalent algorithm.
  • Weighing and storing soft decision information into the corresponding memory module.
  • Performing iterative decoding for a predetermined number of times, where an output from the last decoder is fed back as an input to the first.
• The complaint does not explicitly reserve the right to assert dependent claims.

III. The Accused Instrumentality

Product Identification

• The Accused Instrumentalities include a broad list of Coolpad-branded smartphones (e.g., Coolpad Cool 1 Dual, Coolpad Legacy, Coolpad Defiant) and other cellular communication equipment that are designed to be compliant with 4G/LTE standards (Compl. ¶12).

Functionality and Market Context

• The complaint alleges that the accused products, by virtue of their compliance with 3GPP standards for 4G/LTE, necessarily incorporate and use Turbo coding for channel error correction (Compl. ¶12, ¶15). This functionality is fundamental to their operation as cellular devices, enabling the reliable decoding of received data streams. The complaint provides numerous screenshots of product specifications to support the allegation that the devices are 4G/LTE capable. For example, a specification sheet for the "Coolpad Cool 1 Dual" is included to show its support for various 4G LTE frequency bands (Compl. ¶14, p. 5).

IV. Analysis of Infringement Allegations

Claim Chart Summary

• The complaint's infringement theory is based on mapping the elements of claim 6 to the functionalities mandated by the 3GPP standards for 4G/LTE, which the Accused Instrumentalities are alleged to practice.

’742 Patent Infringement Allegations

Identified Points of Contention

• Scope Questions: A primary issue will be whether the architecture for Turbo decoding described in the 3GPP LTE standards, which the complaint alleges the products follow, falls within the scope of the term "circular circuit" as used in the patent. The defense may argue that the standard's implementation, while iterative, is structurally different from the specific circuit configuration disclosed in the ’742 patent's embodiments (e.g., FIG. 4).
• Technical Questions: The complaint equates the system-level iterative process of HARQ with the claimed feedback loop inside the decoder (Compl. ¶16, ¶24). This raises the technical question of whether the re-transmission of data blocks under HARQ is the same as the claimed method element where the output from the second decoder's memory module is fed back as an input to the first decoder as part of a single, continuous decoding operation.

V. Key Claim Terms for Construction

• The Term: "circular circuit"

  • Context and Importance: This term is the architectural centerpiece of the asserted claim. The infringement case hinges on whether the arrangement of decoders in the accused LTE-compliant products constitutes such a circuit. Practitioners may focus on this term because its construction will likely determine whether the structure mandated by the 3GPP standard reads on the claim.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The patent specification refers to the decoders being "connected in a feedback loop" (’742 Patent, col. 4:10-11), which could support a functional interpretation that covers any architecture where decoders iteratively exchange information to refine a result.
    • Evidence for a Narrower Interpretation: The detailed description and figures, particularly FIG. 4, depict a specific structural arrangement where a "De-Interleaver Memory" (45) explicitly connects the output of the second decoder ("Decoder B") back to the input of the first decoder ("Decoder A"). This could support a narrower definition requiring this specific hardware path.

• The Term: "weighing and storing soft decision information"

  • Context and Importance: This step is crucial to the iterative decoding process. The dispute may focus on whether the standard processing of Log-Likelihood Ratios (LLRs) in an LTE decoder constitutes "weighing" as claimed.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The patent does not appear to define "weighing" in a special way, which may support an interpretation that it simply refers to the standard generation and handling of soft probabilistic values (like LLRs) inherent to any soft-decision decoder.
    • Evidence for a Narrower Interpretation: The reexamination history added the term "weighing" to the claim (Reexam. Cert., col. 2:48-49). A defendant may argue this amendment was made to overcome prior art and thus imparts a specific meaning beyond the mere calculation of soft-decision values, potentially requiring a distinct, separate step not present in the accused devices.

VI. Other Allegations

• Indirect Infringement: The complaint does not plead a separate count for indirect infringement.
• Willful Infringement: The complaint does not plead a separate count for willful infringement. It makes a conclusory allegation of constructive notice but does not allege pre-suit knowledge or other facts typically used to support a willfulness claim (Compl. ¶26).

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

• A core issue will be one of architectural mapping: Can Plaintiff successfully demonstrate that the Turbo decoder structure as defined and implemented in the 3GPP LTE standard is coextensive with the specific "circular circuit" and memory feedback loop required by claim 6, or will the court find a dispositive structural difference between the patented invention and the industry standard?
• The case will also likely involve a key question of claim construction: Will the court interpret the term "circular circuit" functionally, to cover the broad, iterative nature of Turbo decoding in modern cellular systems, or will it adopt a narrower, structural interpretation based on the specific embodiments shown in the patent, potentially placing the standard-compliant accused products outside the claim's scope?