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: 9:25-cv-80307, S.D. Fla., 03/04/2025
• Venue Allegations: Venue is alleged to be proper based on Defendant being headquartered within the Southern District of Florida.
• Core Dispute: Plaintiff alleges that Defendant’s 4G/LTE compliant telecommunications products infringe a patent related to efficient turbo decoder architectures for wireless communications.
• Technical Context: Turbo codes are a class of high-performance error correction codes essential for reliable data transmission in modern wireless standards like 3G and 4G/LTE.
• Key Procedural History: The patent-in-suit underwent an ex parte reexamination requested in 2006, which concluded in 2009 with the issuance of a Reexamination Certificate. The sole asserted claim, Claim 6, was amended during this proceeding, a fact that may be central to arguments regarding claim scope and validity.

Case Timeline

Date	Event
2001-01-02	'742 Patent Priority Date (Filing Date)
2004-11-02	U.S. Patent No. 6,813,742 Issued
2006-07-13	Ex Parte Reexamination Request Filed
2009-02-10	Ex Parte Reexamination Certificate Issued
2025-03-04	Complaint Filed

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 describes that prior art methods for decoding turbo codes, while effective, were computationally complex, power-intensive, and costly to implement in hardware (ASICs), making them impractical for consumer-grade devices like 3G mobile phones (’742 Patent, col. 1:46-61).
• The Patented Solution: The invention proposes a more efficient and simpler decoder architecture. It utilizes two pipelined Soft-In Soft-Out (SISO) Log-MAP decoders connected serially in a feedback loop (’742 Patent, col. 2:39-44, FIG. 4). This design replaces complex multiplication operations with simpler binary adders, which is intended to reduce hardware complexity, lower power consumption, and increase data throughput, making it suitable for 3G applications (’742 Patent, col. 2:54-60).
• Technical Importance: The described approach sought to make powerful turbo decoding technology practical for the mass-market wireless devices emerging in the 3G era by simplifying the required processing hardware (’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 Claim 6 include:
  • 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 the decoders process data from each other and from the input buffer;
  • providing at least one memory module coupled to the decoders' outputs, 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 logarithm approximation algorithm;
  • generating a soft decision based on that algorithm;
  • weighing and storing the soft decision information into the corresponding memory module;
  • performing iterative decoding for a predetermined number of times, with an output from the last decoder fed back to the first in a circular circuit.

III. The Accused Instrumentality

Product Identification

• The Accused Instrumentalities are a wide range of Airspan's 4G/LTE products, including but not limited to the AirHarmony, AirSpeed, AirSynergy, AiRU, and AirSpot product families (Compl. ¶12).

Functionality and Market Context

• The complaint alleges the accused products are cellular base stations (e.g., eNodeB) and customer premises equipment (CPE) that are designed, marketed, and sold for use in 4G/LTE wireless networks (Compl. ¶¶ 12, 14). For example, a product datasheet for the AirHarmony 4400 describes it as a "Macro-class eNodeB" that "supports 3GPP LTE Broadband access technologies" (Compl. ¶14, p. 9).
• The core technical functionality at issue is the products' alleged use of turbo decoders to perform channel coding as required by the 3GPP 4G/LTE standards. The complaint asserts that compliance with these standards necessitates performing the patented method (Compl. ¶15).

IV. Analysis of Infringement Allegations

’742 Patent Infringement Allegations

Claim Element (from Independent Claim 6)	Alleged Infringing Functionality	Complaint Citation	Patent Citation
providing an input buffer comprising at least three shift registers, for receiving an input signal and generating first, second, and third shifted input signals;	The Accused Instrumentalities allegedly implement a turbo decoder with an input buffer structure and shift registers to provide time-aligned input signals needed for SISO computation, as described in technical standards and literature for LTE decoders (Compl. ¶¶16, 18).	¶16, ¶18	col. 4:55-65
providing first and second soft decision decoders serially coupled in a circular circuit, wherein each decoder processes soft decision from the preceding decoder output data...	All known 4G/LTE turbo decoders are alleged to be iterative and use two SISO decoders in a circular feedback loop. A block diagram from a technical paper illustrates two 'SISO' decoders connected in a circular, iterative loop via 'Π' (interleaver) and 'Π⁻¹' (de-interleaver) modules (Compl. ¶33, p. 33).	¶19, ¶20, ¶33	col. 4:8-26
providing at least one memory module coupled to an output of each of the first and second soft decision decoders, wherein the output of the memory module associated with the second soft decision decoder is fed back as an input of the first soft decision decoder;	The "interleaver" and "deinterleaver" blocks in standard turbo decoder architectures are alleged to be the claimed memory modules. The complaint cites diagrams showing the output of the second decoder's path being fed back to the first decoder (Compl. ¶¶22, 35).	¶22, ¶35	col. 4:10-14
processing systematic information data and extrinsic information data using the maximum a posteriori (AP) probability algorithm, and/or logarithm approximation algorithm;	The complaint alleges that LTE turbo decoders, by standard, use variants of the MAP decoding algorithm (such as Log-MAP or Max-Log-MAP) to process systematic and extrinsic data (Compl. ¶¶23, 24, 39).	¶23, ¶39	col. 9:36-40
generating soft decision based on the maximum a posteriori (MAP) probability algorithm, and/or logarithm approximation algorithm;	The generation of soft decisions (likelihood ratios) is alleged to be an inherent function of the MAP/BCJR algorithm used in the turbo decoders of the Accused Instrumentalities (Compl. ¶¶26, 42).	¶26, ¶42	col. 5:28-32
weighing and storing soft decision information into the corresponding memory module;	The complaint alleges that the process of storing a posteriori outputs from the SISO decoders into the interleaver and deinterleaver memory modules constitutes the claimed "weighing and storing" (Compl. ¶¶28, 48).	¶28, ¶48	col. 9:40-42
performing, for a predetermined number of times, iterative decoding from the first to the last of multiple decoders, wherein an output from the last soft decision decoder is fed back as an input to the first soft decision decoder...and propagate to the last decoder in a circular circuit.	The complaint alleges that iterative decoding must be performed a predetermined number of times according to a stopping rule, and cites technical literature stating a default number of iterations (e.g., 8) is common (Compl. ¶¶31, 50).	¶31, ¶50	col. 9:43-50

• Identified Points of Contention:
  • Technical Questions: The complaint's infringement theory rests on the premise that compliance with the 4G/LTE standard inherently requires practicing the claimed method. A central question for the court will be what evidence demonstrates that Airspan's proprietary product architectures, not just the general standard, practice every limitation of Claim 6. For example, does the accused products' handling of soft information constitute "weighing and storing" as required by the claim, or is there a functional distinction?
  • Scope Questions: The patent specification is heavily focused on "3G" technology. This raises the question of whether the claim terms, when interpreted in light of the 3G-centric specification, can be construed to read on the specific turbo decoder implementations used in "4G/LTE" systems, which may have evolved since the patent's priority date.

V. Key Claim Terms for Construction

• The Term: "circular circuit"

• Context and Importance: This term defines the core architectural arrangement of the decoders. Its construction is critical because infringement depends on whether the accused products' feedback loop between decoders matches this claimed structure. Practitioners may focus on this term to dispute whether a software-based or firmware-based processing loop qualifies as a "circuit," or if the specific data flow in the accused products differs from the patent’s description.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: The claim language is functional, describing a serial coupling where data is processed and fed back. The specification’s overall system diagram (FIG. 4) and state machine diagram (FIG. 22) illustrate a functional flow, which may support an interpretation not strictly limited to a specific hardware layout.
  • Evidence for a Narrower Interpretation: The detailed embodiment in Figure 4 shows a distinct, hard-wired block diagram connecting Decoder A, Interleaver Memory, Decoder B, and De-Interleaver Memory. An argument could be made that this specific embodiment narrows the scope of "circular circuit" to a similar physical or logical topology.

• The Term: "predetermined number of times"

• Context and Importance: This limitation defines the iterative nature of the decoding process. The dispute may center on whether the accused systems, which might use dynamic stopping conditions (e.g., terminating early if a CRC check passes), still perform decoding for a "predetermined" number.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: The complaint cites technical literature suggesting that even decoders with early termination capabilities are configured with a maximum number of iterations (Compl. ¶51). This could support an argument that the process is still bound by a "predetermined" upper limit.
  • Evidence for a Narrower Interpretation: The patent mentions iterative decoding for a preset number "L" of times ('742 Patent, col. 9:45-49, FIG. 23). A party could argue this implies a fixed, non-adaptive number of loops, and that a system designed to terminate based on data quality does not meet this limitation.

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

1. A central issue will be one of evidentiary sufficiency: The complaint builds its infringement case primarily on the accused products' compliance with 4G/LTE standards. A key question for the court is whether the Plaintiff can produce evidence from the accused products themselves—rather than just from public standards and academic papers—to prove that Airspan's specific, proprietary implementation of turbo decoding meets every limitation of the asserted claim.
2. The case will likely involve a significant dispute over claim scope and construction: Given that the patent was written and prosecuted in the context of "3G" technology and subsequently underwent reexamination, a core legal question will be whether the amended Claim 6 is broad enough to cover the potentially more advanced and varied turbo decoder designs used in the accused "4G/LTE" products.
3. A further point of contention may be the interpretation of functional claim language: Terms such as "weighing and storing" and "predetermined number of times" will require careful construction. The outcome may turn on whether the accused product's standard operation—such as using an adaptive stopping rule—is found to fall inside or outside the scope of these functionally-defined steps as understood in light of the patent's specification.