TurboCode LLC v. Airspan Networks Inc

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: TurboCode LLC (Texas)
  • Defendant: Airspan Networks Inc. (Delaware)
  • Plaintiff’s Counsel: Beusse Sanks, PLLC
• Case Identification: 0:25-cv-60418, S.D. Fla., 03/04/2025
• Venue Allegations: Venue is alleged to be proper based on Defendant's headquarters and principal place of business being located within the Southern District of Florida.
• Core Dispute: Plaintiff alleges that Defendant’s 4G/LTE wireless communication products infringe a patent related to high-speed turbo code decoder architecture.
• Technical Context: The technology concerns turbo codes, a class of forward error correction codes used in digital communications to achieve reliable data transfer over noisy channels, particularly in 3G and 4G/LTE cellular networks.
• Key Procedural History: The patent-in-suit was the subject of an Ex Parte Reexamination, with a Reexamination Certificate issued on February 10, 2009. The asserted claim, claim 6, was amended during this proceeding, which will focus the infringement and validity analyses on the post-reexamination claim language.

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 decoders, while effective, were computationally complex, requiring many multiplications and additions. This complexity made them costly, power-intensive, and difficult to implement efficiently in semiconductor (ASIC) designs for consumer wireless devices like 3G mobile phones (’742 Patent, col. 2:15-29).
• The Patented Solution: The invention proposes a decoder architecture using two pipelined and serially connected "SISO Log-MAP" (Soft-In/Soft-Out Logarithmic-Maximum A Posteriori) decoders. In this scheme, one decoder processes data from a memory module (the de-interleaver) while the other simultaneously processes data from another memory (the interleaver), creating a feedback loop for iterative decoding (’742 Patent, col. 2:40-54). This pipelined structure, which uses simpler binary adder circuits instead of complex multipliers, is designed to achieve high-speed data throughput—one decoded output per clock cycle—with lower power consumption and simplified hardware implementation (’742 Patent, Abstract; col. 2:56-61).
• Technical Importance: This architectural approach aimed to make powerful turbo decoding technology practical for mass-market, power-limited devices by reducing implementation complexity and cost, a key challenge in the development of 3G and subsequent wireless standards (’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 reexamined claim 6 include:
  • A method of iteratively decoding received baseband signals.
  • Providing an input buffer with at least three shift registers for generating 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 decision data from the preceding one.
  • The first decoder receives the first and second shifted input signals; the second decoder receives the third shifted input signal.
  • Providing at least one memory module coupled to the output of each decoder, where the output of the memory associated with the second decoder is fed back as an input to the first.
  • Processing systematic and extrinsic information data using a maximum a posteriori (MAP) probability algorithm and/or a logarithm approximation algorithm.
  • Generating a soft decision based on the MAP and/or logarithm approximation algorithm.
  • Weighing and storing the soft decision information into the corresponding memory module.
  • Performing iterative decoding for a predetermined number of times, with the output from the last decoder fed back to the first in a circular circuit.
• The complaint does not explicitly reserve the right to assert dependent claims.

III. The Accused Instrumentality

Product Identification

The complaint identifies a wide range of Airspan 4G/LTE products, including the AirHarmony, AirSpeed, AirSynergy, AiRU, AirSpot, and AirVelocity series, collectively termed the "Accused Instrumentalities" (Compl. ¶12).

Functionality and Market Context

• The Accused Instrumentalities are described as cellular wireless communication devices, such as eNodeBs (base stations) and CPEs (Customer Premises Equipment), that comply with 4G/LTE standards as defined by the 3rd Generation Partnership Project (3GPP) (Compl. ¶12). The complaint provides numerous product datasheets as evidence. For instance, the datasheet for the "AirHarmony 1000" describes it as an "Outdoor 4G LTE eNodeB" that "Supports the latest 3GPP LTE broadband access technologies" (Compl. p. 5). The infringement theory is premised on the fact that compliance with these 3GPP standards for 4G/LTE necessarily requires performing turbo decoding (Compl. ¶15, ¶25).
• The complaint alleges these products are commercially significant, citing Airspan's deployment of over 700,000 4G radios, which "set the standard for coverage and capacity for public and private networks" (Compl. p. 15).

IV. Analysis of Infringement Allegations

’742 Patent Infringement Allegations

Identified Points of Contention

• Scope Questions: The patent was filed in 2001 and is directed to "3G" technology. The accused products are "4G/LTE." A central dispute may be whether the term "soft decision decoder" and the specific "SISO Log-MAP" architecture described in the patent can be construed to cover the turbo decoder implementations mandated by the later 4G/LTE standards, which the complaint alleges are functionally equivalent (Compl. ¶20, ¶25).
• Technical Questions: The complaint's infringement theory relies heavily on the argument that compliance with 3GPP standards for 4G/LTE inherently practices the claimed method (Compl. ¶15). A key question for the court will be whether the standards documents and academic papers cited provide sufficient factual specificity to plausibly allege that the accused products' actual implementation of a turbo decoder meets every limitation of claim 6, particularly the "weighing and storing" and "circular circuit" elements.

V. Key Claim Terms for Construction

Term: "soft decision decoder"

• Context and Importance: This term is at the core of the invention. The infringement case depends on this term being construed broadly enough to encompass the decoders used in Defendant's 4G/LTE products. Practitioners may focus on this term because while the patent specification repeatedly refers to a "SISO Log-MAP decoder" (’742 Patent, Abstract; col. 2:41), the claim uses the more general term "soft decision decoder."
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The claim itself uses the general term "soft decision decoder" without expressly limiting it to a "Log-MAP" implementation. The reexamination history, which confirmed the patentability of the amended claims, may be argued to endorse this broader scope.
  • Evidence for a Narrower Interpretation: The specification consistently describes the invention as using "SISO Log-MAP Decoders" to achieve its stated advantages of simplicity and low power consumption (’742 Patent, Abstract; col. 2:31-37). A party could argue that the claims should be limited to this specific type of decoder, which is the only one described and enabled in the patent.

Term: "weighing and storing soft decision information"

• Context and Importance: This is an active step in the claimed method. The complaint alleges this is an inherent part of any MAP algorithm implementation (Compl. ¶49). The viability of this infringement allegation may depend on whether "weighing" is found to be a distinct step or simply an inherent property of the algorithm's calculations.
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The claim language is functional. A party could argue that any normalization, scaling, or probability calculation that is part of the MAP algorithm and whose result is stored meets this limitation. The reexamination certificate added the word "weighing," suggesting it has meaning independent of just "storing."
  • Evidence for a Narrower Interpretation: The patent does not appear to explicitly define "weighing" or describe a separate hardware component for it. A party could argue this term is indefinite or should be narrowly construed to require a specific, explicit weighting/scaling step distinct from the standard calculations of a MAP decoder.

VI. Other Allegations

The complaint contains a single count for direct infringement of the ’742 patent (Compl. p. 2). It does not explicitly plead indirect infringement (inducement or contributory) or willful infringement, nor does it allege facts to support the knowledge and intent elements required for such claims. The complaint notes that Defendant had at least constructive notice of the patent (Compl. ¶34).

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

1. Definitional Scope and Inter-Generational Technology: A central issue will be whether the claims, drafted with "3G" systems as the primary context, can be construed to cover the turbo decoder implementations in Defendant's "4G/LTE" products. The case may turn on if the term "soft decision decoder" is limited to the specific "Log-MAP" architecture detailed in the patent or if it is broad enough to read on the functionally similar, but potentially different, decoders used in the accused 4G/LTE systems.
2. Sufficiency of Standards-Based Pleading: The infringement theory is built on the premise that compliance with 3GPP standards for 4G/LTE necessitates use of the patented method. A key question is whether the complaint's reliance on standards, academic papers, and general product datasheets provides sufficient factual detail to plausibly allege that Airspan's specific products practice every element of the asserted claim, or if it will be challenged as an insufficient "infringement by standard" pleading.
3. Evidentiary Proof of Functionality: A key evidentiary question will be one of functional operation. Does the accused products' implementation of the MAP/BCJR algorithm, as dictated by the LTE standard, perform the specific step of "weighing and storing" information in the manner required by claim 6, or is there a technical mismatch between the claim language and the actual operation of the accused decoders?