DCT

6:25-cv-00112

Redwood Tech LLC v. Realtek Semiconductor Corp

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 6:25-cv-00112, W.D. Tex., 03/25/2025
  • Venue Allegations: Plaintiff alleges venue is proper because Defendant is a foreign corporation, which may be sued in any judicial district. The complaint further alleges Defendant conducts substantial business within the Western District of Texas through the sale of Wi-Fi compliant devices via intermediaries, subsidiaries, distributors, and retailers.
  • Core Dispute: Plaintiff alleges that Defendant’s Wi-Fi compliant semiconductor devices and related products infringe seven U.S. patents related to wireless communication standards, including methods for adaptive modulation, Quality of Service (QoS), and signal formatting.
  • Technical Context: The technology at issue involves fundamental techniques for efficient and reliable data transmission in wireless local area networks (WLANs), which are foundational to the operation of modern Wi-Fi devices compliant with IEEE 802.11 standards.
  • Key Procedural History: The complaint alleges that Plaintiff made multiple attempts to engage Defendant in licensing discussions prior to filing suit, beginning with a FedEx letter on November 2, 2021. Subsequent letters and emails were allegedly either refused or ignored by Defendant, which may serve as a basis for Plaintiff’s claims of pre-suit knowledge and willful infringement.

Case Timeline

Date Event
2003-09-05 Priority Date: U.S. Patent No. 7,460,485
2004-04-20 Priority Date: U.S. Patent No. 7,359,457
2004-12-06 Priority Date: U.S. Patent No. 7,983,140
2005-08-24 Priority Date: U.S. Patent Nos. 7,826,555; 9,374,209; 10,270,574
2007-11-08 Priority Date: U.S. Patent No. 7,917,102
2008-04-15 Issue Date: U.S. Patent No. 7,359,457
2008-12-02 Issue Date: U.S. Patent No. 7,460,485
2010-11-02 Issue Date: U.S. Patent No. 7,826,555
2011-03-29 Issue Date: U.S. Patent No. 7,917,102
2011-07-19 Issue Date: U.S. Patent No. 7,983,140
2016-06-21 Issue Date: U.S. Patent No. 9,374,209
2019-04-23 Issue Date: U.S. Patent No. 10,270,574
2021-11-02 Plaintiff allegedly sent first licensing letter to Defendant
2021-12-08 Plaintiff allegedly sent follow-up licensing letter to Defendant
2022-05-12 Plaintiff allegedly sent email with notice letters and infringement charts to Defendant
2022-05-22 Plaintiff allegedly sent another licensing letter to Defendant
2023-09-15 Plaintiff allegedly sent email with notice letters to Defendant
2024-07-19 Plaintiff allegedly sent email with notice letters to Defendant
2025-03-25 Complaint Filing Date

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

U.S. Patent No. 7,359,457 - "Transmission Apparatus, Reception Apparatus and Digital Radio Communication Method"

  • Patent Identification: U.S. Patent No. 7,359,457, "Transmission Apparatus, Reception Apparatus and Digital Radio Communication Method," issued April 15, 2008. (Compl. ¶62).

The Invention Explained

  • Problem Addressed: The patent describes the need for a communication method capable of "flexibly improving the data transmission efficiency and the quality of data" in wireless systems where the transmission environment changes. (’457 Patent, col. 1:59-63).
  • The Patented Solution: The invention proposes a transmission apparatus that adapts its modulation scheme based on the current "communication situation." (Compl. ¶75). It determines an appropriate modulation system from a plurality of options and then generates and transmits both a first data symbol using this adaptively selected system and a second control symbol using a separate, predetermined modulation system. ('457 Patent, Abstract; col. 3:36-48). This allows the transmitter to optimize data rate for current channel conditions while maintaining reliable control signaling.
  • Technical Importance: Adaptive modulation is a foundational technique in modern wireless communications, allowing devices to maximize data throughput under favorable conditions and maintain a stable connection under poor conditions. (Compl. ¶75).

Key Claims at a Glance

  • Independent claim 1 is asserted in the complaint. (Compl. ¶67).
  • Claim 1 requires:
    • A transmission apparatus with a determination section and a modulation section.
    • The determination section determines a modulation system from a plurality of options based on a "communication situation."
    • The modulation section generates a first symbol using the determined modulation system and a second symbol using a predetermined modulation system.
    • Both symbols comprise a quadrature baseband signal.
  • The complaint reserves the right to assert additional claims.

U.S. Patent No. 7,460,485 - "Methods for Performing Medium Dedication in Order to Ensure the Quality of Service for Delivering Real-Time Data Across Wireless Network"

  • Patent Identification: U.S. Patent No. 7,460,485, "Methods for Performing Medium Dedication in Order to Ensure the Quality of Service for Delivering Real-Time Data Across Wireless Network," issued December 2, 2008. (Compl. ¶85).

The Invention Explained

  • Problem Addressed: The patent addresses the challenge of delivering "time sensitive data, such as real-time Audio-Visual data...across an erroneous transmission medium," which requires coordination and scheduling to meet Quality of Service (QoS) guarantees. (’485 Patent, col. 1:10-15).
  • The Patented Solution: The invention provides a method for managing QoS by systematically performing "medium dedication." This involves specifying traffic requirements, transforming those requirements into a format that accounts for medium conditions and overhead, aggregating multiple specifications to reduce overhead, adjusting the specifications based on feedback, and performing transmissions according to a coordinated schedule. ('485 Patent, col. 1:29-38).
  • Technical Importance: QoS management is critical for modern wireless applications like video conferencing and online gaming, which depend on prioritized and timely data delivery to function correctly. (Compl. ¶¶91, 100).

Key Claims at a Glance

  • Independent claim 1 is asserted in the complaint. (Compl. ¶90).
  • Claim 1 requires a method for guaranteeing QoS comprising the steps of:
    • Specifying a traffic requirement for a traffic stream.
    • Transforming the requirement into a second specification based on the initial requirement, overhead, and medium conditions.
    • Adjusting the second specification based on feedback from monitoring the medium.
    • Aggregating specifications for multiple traffic streams into a single specification.
    • Performing medium dedication according to a schedule to coordinate transmission.
  • The complaint reserves the right to assert additional claims.

U.S. Patent No. 7,826,555 - "MIMO-OFDM Transmission Device and MIMO-OFDM Transmission Method"

  • Patent Identification: U.S. Patent No. 7,826,555, "MIMO-OFDM Transmission Device and MIMO-OFDM Transmission Method," issued November 2, 2010. (Compl. ¶107).
  • Technology Synopsis: The patent addresses problems in multiple-input multiple-output (MIMO) OFDM communications related to accurately estimating frequency offset and transmission path fluctuations. (’555 Patent, col. 2:19-45). The solution involves transmitting OFDM-modulated data and pilot symbols from multiple antennas, where the pilot symbols on specific carriers are assigned orthogonal sequences to simplify compensation and improve estimation accuracy. ('555 Patent, col. 2:60-3:3).
  • Asserted Claims: At least independent claim 1. (Compl. ¶112).
  • Accused Features: The accused features are the MIMO-OFDM transmission capabilities of devices compliant with IEEE 802.11n/ac/ax/be standards, which allegedly transmit data and pilot symbols from multiple antennas using orthogonal sequences for pilot carriers. (Compl. ¶¶113-118).

U.S. Patent No. 7,983,140 - "Transmitting Apparatus, Receiving Apparatus, and Communication System for Formatting Data"

  • Patent Identification: U.S. Patent No. 7,983,140, "Transmitting Apparatus, Receiving Apparatus, and Communication System for Formatting Data," issued July 19, 2011. (Compl. ¶136).
  • Technology Synopsis: The patent addresses the problem of interference in cellular networks where adjacent cells use the same frequency. (’140 Patent, col. 1:30-44). The solution is a specific data format for OFDM transmission that generates a frame including a series of time slots and an added "frame guard period" to prevent an interfering wave from affecting a subsequent frame, thereby improving spectrum efficiency. ('140 Patent, col. 18:63-19:2).
  • Asserted Claims: At least independent claim 1. (Compl. ¶141).
  • Accused Features: The accused features are the frame generation functionalities of IEEE 802.11 compliant devices, which allegedly generate a PPDU frame comprising a series of time slots (OFDM symbols) and guard periods. (Compl. ¶¶142-143).

U.S. Patent No. 9,374,209 - "Transmission Signal Generation Apparatus, Transmission Signal Generation Method, Reception Signal Apparatus, and Reception Signal Method"

  • Patent Identification: U.S. Patent No. 9,374,209, "Transmission Signal Generation Apparatus, Transmission Signal Generation Method, Reception Signal Apparatus, and Reception Signal Method," issued June 21, 2016. (Compl. ¶159).
  • Technology Synopsis: The patent describes a transmission apparatus for MIMO-OFDM communications that generates transmission signals containing preamble, pilot, and data information. (’209 Patent, col. 68:1-69:1). A key aspect is the use of an Inverse Fourier transformer to arrange plural pilot symbol sequences, which are all orthogonal to each other, in corresponding pilot carriers to improve signal estimation. ('209 Patent, col. 67:168-170).
  • Asserted Claims: At least independent claim 1. (Compl. ¶164).
  • Accused Features: The accused features are the transmission signal generation capabilities of devices compliant with IEEE 802.11n/ac/ax/be, which allegedly generate HT-mixed format transmission signals where pilot sequences corresponding to different spatial streams are orthogonal. (Compl. ¶¶164, 170).

U.S. Patent No. 10,270,574 - "Transmission Signal Generation Apparatus, Transmission Signal Generation Method, Reception Signal Apparatus, and Reception Signal Method"

  • Patent Identification: U.S. Patent No. 10,270,574, "Transmission Signal Generation Apparatus, Transmission Signal Generation Method, Reception Signal Apparatus, and Reception Signal Method," issued April 23, 2019. (Compl. ¶187).
  • Technology Synopsis: The patent describes a transmission apparatus that maps streams of input data to complex symbols and uses an inverse Fourier transform to create OFDM signals for transmission over multiple subcarriers. (’574 Patent, Abstract). The invention specifies transmitting different pilot information on different pilot subcarriers within the same set of time slots to improve signal integrity and estimation in a multi-antenna system.
  • Asserted Claims: At least independent claim 1. (Compl. ¶192).
  • Accused Features: The accused features are the electronic circuitry in IEEE 802.11 compliant devices that map data to complex symbols, perform inverse Fourier transforms to generate OFDM signals, and transmit different pilot values on different pilot subcarriers within the same OFDM symbol. (Compl. ¶¶193-198).

U.S. Patent No. 7,917,102 - "Radio Transmitting Apparatus and Radio Transmission Method"

  • Patent Identification: U.S. Patent No. 7,917,102, "Radio Transmitting Apparatus and Radio Transmission Method," issued March 29, 2011. (Compl. ¶222).
  • Technology Synopsis: The patent addresses improving reception quality in systems where the number of simultaneously transmitted signals changes. (’102 Patent, col. 2:12-18). The solution involves forming a transmission frame that includes distinct signals for frequency offset estimation, channel fluctuation estimation, and gain control, with a specific arrangement where two gain control signals are placed before and after the frequency offset estimation signal. ('102 Patent, Abstract; Claim 3).
  • Asserted Claims: At least independent claim 3. (Compl. ¶227).
  • Accused Features: The accused features are the mandatory HT-mixed format PPDU frame structure in IEEE 802.11 compliant devices, which allegedly includes L-LTF (frequency offset estimation), HT-LTF (channel fluctuation), L-STF (first gain control), and HT-STF (second gain control) subframes in the claimed arrangement. (Compl. ¶¶228-230).

III. The Accused Instrumentality

Product Identification

  • The Accused Products are identified as "Realtek Wi-Fi compliant devices," which include components compliant with IEEE 802.11 standards (e.g., 802.11n, 802.11ac, 802.11ax, 802.11be), as well as devices compliant with the Wi-Fi Multimedia ("WMM") standard. (Compl. ¶3, ¶60, ¶90). The complaint identifies the Realtek RTL8812BU as a representative accused product. (Compl. ¶67).

Functionality and Market Context

  • The accused products are semiconductor components, such as WLAN MACs, basebands, and RF chips, that provide Wi-Fi functionality. (Compl. ¶22, ¶67). These components are allegedly incorporated into a wide range of downstream consumer electronics, including routers, laptops, and IoT devices from manufacturers like Asus and Lenovo. (Compl. ¶23, ¶32-33). The complaint alleges these products are sold in the United States and specifically in Texas, forming a substantial market. (Compl. ¶31, ¶36). A screenshot provided in the complaint shows the Wi-Fi Alliance certification for the RTL8812BU, confirming its compliance with standards including WMM. (Compl. p. 36).

IV. Analysis of Infringement Allegations

’457 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
a determination section that determines a modulation system from a plurality of modulation systems based on a communication situation The accused devices utilize a Modulation and Coding Scheme (MCS) value to determine the modulation, coding, and number of spatial channels based on a channel quality assessment. ¶68 col. 3:36-41
a modulation section that modulates a digital transmission signal to generate a first symbol ... according to the modulation system determined by the determination section The accused devices generate a first data symbol (e.g., the data portion of a packet) that is modulated according to the selected MCS value (e.g., 16-QAM). ¶69 col. 3:41-45
[the modulation section generates] a second symbol ... according to a predetermined modulation system The accused devices generate a second control symbol (e.g., the HT-SIG field) that is modulated according to a predetermined system (e.g., QBPSK), independent of the channel conditions. ¶71 col. 3:45-48
the first symbol and the second symbol each comprise a quadrature baseband signal Both the data symbol and the control symbol are quadrature baseband signals (e.g., an OFDM signal before up-conversion). A constellation diagram in the complaint illustrates the in-phase (I) and quadrature (Q) components for a 16-QAM signal. ¶69, ¶71, p. 24 col. 3:48-48
  • Identified Points of Contention:
    • Scope Questions: A central question may be whether the term "communication situation" is met by the "channel quality assessment" used for MCS selection in the IEEE 802.11 standard. The defense may argue the patent contemplates a different or more complex type of input than what the standard mandates.
    • Technical Questions: The complaint's theory relies on mapping patent claim elements to distinct functional blocks and signals within the IEEE 802.11 standard (e.g., mapping "first symbol" to the data payload and "second symbol" to the HT-SIG field). The court will need to determine if this mapping accurately reflects the technical operation of the accused devices and the scope of the patent's claims.

’485 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
specifying a traffic requirement for a traffic stream in accordance with a generic first specification The accused devices utilize the Traffic Specification ("TSPEC") element, compliant with the WMM standard, to define QoS parameters for a Wi-Fi station. ¶92 col. 2:6-14
transforming the specified traffic requirement in accordance with a generic second specification based on the specified traffic requirement, an overhead requirement for the traffic stream and a condition of the transmission medium The accused devices transform the TSPEC into "medium time," a metric that accounts for the TSPEC parameters, overhead, and expected error performance on the wireless medium. ¶93 col. 2:15-21
adjusting the generic second specification based on feedback obtained from monitoring the condition of the transmission medium The accused devices adjust the "medium time" upon receipt of each new TSPEC from a station. ¶94 col. 2:27-31
aggregating a plurality of specifications for a plurality of traffic steams into a single specification The accused devices aggregate the mean data rate and burst size for multiple traffic streams to generate a single "token bucket specification" for more efficient management. ¶95 col. 2:22-26
performing medium dedication in accordance with the medium dedication schedule to coordinate transmission of the plurality of traffic streams The accused devices perform medium dedication according to a schedule to coordinate transmission between multiple stations with admitted traffic streams. ¶96 col. 2:32-35
  • Identified Points of Contention:
    • Scope Questions: The infringement theory depends on mapping the generic claim terms (e.g., "generic first specification") to specific elements of the WMM standard (e.g., "TSPEC"). A potential dispute is whether the standard's implementation falls within the patent's claimed scope or constitutes a distinct, non-infringing approach.
    • Technical Questions: A key question will be whether adjusting "medium time" upon receipt of a new TSPEC, as the accused products allegedly do, meets the limitation of "adjusting...based on feedback obtained from monitoring the condition of the transmission medium." The defense could argue this is a pre-negotiated change rather than an adaptive adjustment based on real-time monitoring as taught by the patent.

V. Key Claim Terms for Construction

’457 Patent - "communication situation"

  • The Term: "communication situation"
  • Context and Importance: This term defines the input that triggers the claimed adaptive modulation. The infringement case turns on whether the "channel quality assessment" used in the IEEE 802.11 standard is a "communication situation." Practitioners may focus on this term because its breadth will determine if the patent reads on standard-compliant behavior.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The patent specification describes the determination section as one that "judges the communication situation based on transmission path information." ('457 Patent, col. 3:37-38). This language may support a broad construction that includes any metric related to channel quality.
    • Evidence for a Narrower Interpretation: The patent does not appear to explicitly define or limit the term, but a defendant may argue that the overall context of the invention implies a specific type of situational judgment beyond a simple, standardized quality score.

’485 Patent - "feedback obtained from monitoring the condition of the transmission medium"

  • The Term: "feedback obtained from monitoring the condition of the transmission medium"
  • Context and Importance: This limitation requires the system to be adaptive. The complaint alleges that adjusting medium time upon receipt of a new TSPEC satisfies this element. The dispute will likely center on whether a TSPEC update constitutes "feedback from monitoring" or is merely a renegotiation of parameters.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The specification describes performing "adaptation in order to tune the specification to be more reliable, and by performing monitoring and reporting of medium condition." ('485 Patent, col. 1:35-38). This could be interpreted to encompass any mechanism that updates the system's operating parameters in response to changing needs or conditions, including a new TSPEC.
    • Evidence for a Narrower Interpretation: The language suggests an active, ongoing "monitoring" process that generates "feedback." A defendant could argue this implies a closed-loop system that measures real-time channel conditions and adjusts parameters automatically, which may differ from the process of a station initiating a new TSPEC request.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges that Defendant induces infringement by designing, manufacturing, and selling the Accused Products with knowledge that its customers (e.g., device manufacturers) and end-users will combine and use them in an infringing manner. (Compl. ¶¶77, 102). Affirmative acts of inducement are alleged to include creating products that conform to IEEE 802.11 standards, providing user manuals, and offering technical support. (Compl. ¶77).
  • Willful Infringement: The complaint alleges willful infringement based on Defendant's alleged pre-suit knowledge of the Asserted Patents. (Compl. ¶82). This knowledge is based on a series of notice letters and emails allegedly sent by Plaintiff to Defendant starting in November 2021, which Defendant is said to have refused to accept or to which it refused to respond. (Compl. ¶¶76, 101).

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

  • A core issue will be one of scope and standards-compliance: do the asserted patents, which were filed before or during the development of later 802.11 standards, use terminology that can be properly construed to cover the mandatory, standardized functions of Wi-Fi devices? The resolution will likely determine whether these patents are effectively essential to the 802.11 standards.
  • A second key question will be one of technical mapping: does the operational logic of the accused IEEE 802.11 and WMM functions (e.g., MCS selection, TSPEC processing) align with the specific steps and structures required by the patent claims, or is there a functional mismatch that precludes a finding of infringement?
  • For damages, a central question will be one of willfulness and intent: given the detailed allegations of multiple pre-suit communications that were allegedly ignored, can Plaintiff establish that Defendant's conduct was egregious and characteristic of a "pirate," as alleged, thereby justifying an award of enhanced damages?