DCT

6:23-cv-00280

Redwood Tech LLC v. Acer Inc

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 6:23-cv-00280, W.D. Tex., 04/14/2023
  • Venue Allegations: Plaintiff alleges venue is proper in the Western District of Texas because Defendant Acer America Corporation maintains a place of business in Temple, Texas. For Defendant Acer Inc., a Taiwanese corporation, Plaintiff invokes the alien venue rule, which allows suit in any judicial district.
  • Core Dispute: Plaintiff alleges that Defendant’s Wi-Fi compliant electronic devices, including laptops, tablets, and smart speakers, infringe eight patents related to digital radio communication methods, such as adaptive modulation and signal processing for multi-antenna systems.
  • Technical Context: The patents relate to technologies foundational to modern wireless networking standards like IEEE 802.11n/ac/ax (Wi-Fi 4/5/6), focusing on improving data transmission efficiency, reliability, and speed in complex radio environments.
  • Key Procedural History: The complaint alleges that Plaintiff sent a letter to Acer on November 8, 2021, providing notice of the Asserted Patents and offering licensing discussions. It further alleges that after a response from Acer, Plaintiff provided Acer with access to additional materials concerning the patents and infringement on January 14, 2022. This history is presented to support allegations of willful infringement.

Case Timeline

Date Event
1999-07-28 U.S. Patent No. 7,359,457 Priority Date
2000-12-08 U.S. Patent No. 7,983,140 Priority Date
2001-11-13 U.S. Patent No. 7,688,901 & 7,974,371 Priority Date
2005-08-24 U.S. Patent No. 8,284,866, 9,374,209 & 7,826,555 Priority Date
2007-11-08 U.S. Patent No. 7,917,102 Priority Date
2008-04-15 U.S. Patent No. 7,359,457 Issues
2010-03-30 U.S. Patent No. 7,688,901 Issues
2010-11-02 U.S. Patent No. 7,826,555 Issues
2011-03-29 U.S. Patent No. 7,917,102 Issues
2011-07-05 U.S. Patent No. 7,974,371 Issues
2011-07-19 U.S. Patent No. 7,983,140 Issues
2012-10-09 U.S. Patent No. 8,284,866 Issues
2016-06-21 U.S. Patent No. 9,374,209 Issues
2021-11-08 Plaintiff sends notice letter to Acer
2022-01-14 Plaintiff provides Acer access to additional materials
2023-04-14 Complaint Filed

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

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

The Invention Explained

  • Problem Addressed: The patent’s background section describes that conventional digital modulation systems use a fixed pilot symbol insertion interval and a fixed modulation scheme for information symbols, which can be inefficient. When transmission path fluctuations are intense or reception signal levels are low, data quality deteriorates; when conditions are good, data transmission efficiency cannot be improved. (’457 Patent, col. 1:45-54).
  • The Patented Solution: The invention provides a transmission apparatus that can flexibly adapt to changing channel conditions. It features a "frame configuration determination section" that assesses the "communication situation" (e.g., transmission path fluctuations or reception signal level) and selects an appropriate modulation system from a plurality of options (e.g., 16-QAM or 8PSK) for transmitting data symbols. This section works in conjunction with symbol generators that modulate the digital signal, allowing the system to balance data transmission efficiency and quality. (’457 Patent, col. 2:59-63, Fig. 1).
  • Technical Importance: This adaptive modulation approach allows wireless devices to maximize data throughput in good signal conditions and maintain a reliable connection in poor conditions, a core principle in modern high-performance Wi-Fi standards. (’457 Patent, col. 2:59-63).

Key Claims at a Glance

  • The complaint asserts independent claim 1 (Compl. ¶36).
  • Claim 1 of the ’457 Patent requires:
    • A frame configuration determiner that determines a modulation system from a plurality of modulation systems based on a communication situation.
    • A first symbol generator that modulates a digital transmission signal according to the determined modulation system to generate a first symbol comprising a first quadrature baseband signal.
    • A second symbol generator that modulates the digital transmission signal according to a predetermined modulation system to generate a second symbol comprising a second quadrature baseband signal.
  • The complaint does not explicitly reserve the right to assert dependent claims for this patent.

U.S. Patent No. 7,688,901 - “Transmission Method, Transmission Apparatus, and Reception Apparatus”

The Invention Explained

  • Problem Addressed: In systems that transmit multiple modulation signals simultaneously from multiple antennas (multiplexing), conventional structures do not adequately address synchronization between channels or frequency offsets. This makes it difficult for a receiver to accurately estimate the channels and demultiplex the signals. (’901 Patent, col. 1:41-45).
  • The Patented Solution: The invention proposes a transmission method where "preamble symbol groups" are inserted at the same temporal points in each of the multiple modulation signals. Crucially, these symbol groups are designed to be orthogonal to each other, meaning they have zero mutual correlation. This orthogonality allows the reception apparatus to easily isolate the symbols from each channel, enabling accurate channel estimation and simplifying the demultiplexing process. (’901 Patent, col. 2:16-22).
  • Technical Importance: This method provides a robust way to perform channel estimation in multi-antenna (MIMO) systems, a technology essential for achieving the high data rates of modern Wi-Fi standards by allowing receivers to distinguish between multiple simultaneous data streams. (’901 Patent, col. 1:50-52).

Key Claims at a Glance

  • The complaint asserts independent claim 1 (Compl. ¶55).
  • Claim 1 of the ’901 Patent requires a method of:
    • Generating a plurality of modulation signals, each to be transmitted from a different antenna.
    • Each modulation signal includes one or more preamble symbol groups, each consisting of a plurality of preamble symbols for demodulation.
    • Inserting the preamble symbol groups at the same temporal point(s) in each modulation signal.
    • The preamble symbol groups at the same temporal point(s) are orthogonal to other preamble symbol groups at the same point(s) with zero mutual correlation.
    • Each preamble symbol has a non-zero amplitude.
    • Each preamble symbol group consists of a quantity of preamble symbols that is greater than the quantity of modulation signals to be transmitted.
    • Transmitting the plurality of modulation signals from the plurality of antennas in an identical frequency band.
  • The complaint does not explicitly reserve the right to assert dependent claims for this patent.

U.S. Patent No. 7,974,371 - “Communication Method and Radio Communication Apparatus”

  • Technology Synopsis: The patent describes a communication apparatus that switches between transmitting a single modulation signal from one antenna and transmitting multiple modulation signals from multiple antennas. The choice of transmission method is based on the estimated radio-wave propagation environment, allowing the system to increase the data transmission rate by multiplexing signals when conditions permit. (’371 Patent, col. 4:27-31, col. 5:4-16).
  • Asserted Claims: The complaint asserts independent claim 14 (Compl. ¶74).
  • Accused Features: The complaint alleges that the Accused Products infringe by selecting between a single spatial stream (first transmission method) and multiple spatial streams for spatial multiplexing (second transmission method) based on channel quality information received from a communication partner (Compl. ¶¶75-76).

U.S. Patent No. 8,284,866 - “OFDM Transmission Signal Generation Apparatus and Method, and OFDM Reception Data Generation Apparatus and Method”

  • Technology Synopsis: The patent addresses the problem of accurately estimating frequency offset and channel fluctuation in MIMO-OFDM systems. It proposes forming pilot carriers by assigning orthogonal sequences to corresponding subcarriers among OFDM signals transmitted simultaneously from different antennas, enabling high-accuracy estimation even when pilot symbols are multiplexed. (’866 Patent, col. 3:4-10).
  • Asserted Claims: The complaint asserts independent claim 1 (Compl. ¶92).
  • Accused Features: The complaint alleges that the Accused Products’ use of spatial mappers to form multiple OFDM signals containing pilot carriers at identical positions infringes. It is alleged that orthogonal pilot sequences are assigned to these identical time slots and carrier positions among the plurality of signals. (Compl. ¶¶93-94).

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

  • Technology Synopsis: The technology is similar to the ’866 Patent, aiming to improve frequency offset and channel estimation in MIMO-OFDM systems. The solution involves assigning orthogonal sequences to corresponding subcarriers to form pilot carriers, which simplifies compensation for frequency offset/phase noise because pilot symbols can be extracted without a channel estimator value. (’209 Patent, col. 3:9-19).
  • Asserted Claims: The complaint asserts independent claim 11 (Compl. ¶110).
  • Accused Features: The complaint alleges infringement through the generation of transmission signals that include a data frame with preamble, pilot, and data information. It further alleges these signals include plural, orthogonal pilot symbol sequences arranged in the same carrier positions in the corresponding OFDM signals. (Compl. ¶¶111, 113, 116).

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

  • Technology Synopsis: The patent describes a MIMO-OFDM transmission method for realizing an ideal symbol configuration for frequency offset and channel estimation. The solution involves a pilot symbol mapping section that assigns orthogonal sequences to the same carriers of OFDM signals transmitted at the same time, allowing for high-accuracy estimation of frequency offset/phase noise. (’555 Patent, col. 2:60-66).
  • Asserted Claims: The complaint asserts independent claims 1 and 4 (Compl. ¶132).
  • Accused Features: The complaint alleges infringement by a MIMO-OFDM apparatus that transmits OFDM-modulated data and pilot symbols from multiple antennas. Specifically, it points to a pilot symbol mapping section that allegedly assigns orthogonal sequences to the same carriers of the OFDM signals for a given time period. (Compl. ¶¶132-134).

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

  • Technology Synopsis: The patent aims to improve reception quality by reducing quantization error in systems where the number of simultaneously transmitted signals changes. The solution involves changing the transmit power of the modulated signal from each antenna according to the number of antennas that are simultaneously transmitting. (’102 Patent, col. 2:12-22).
  • Asserted Claims: The complaint asserts independent claim 3 (Compl. ¶153).
  • Accused Features: The complaint alleges infringement through the forming and transmitting of a transmission frame (e.g., HT-mixed format PPDU) that includes signals for frequency offset estimation, channel fluctuation estimation, and gain control, with specific arrangements of these signals within the frame. (Compl. ¶¶154, 156).

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

  • Technology Synopsis: The patent addresses interference in cellular networks where cells use the same frequency. The proposed solution is a specific data format for OFDM transmission that includes a "frame guard period added to the series of n time slots" to prevent an interfering wave from interfering with a subsequent frame, thereby improving spectrum efficiency. (’140 Patent, col. 18:63-19:2).
  • Asserted Claims: The complaint asserts independent claim 1 (Compl. ¶171).
  • Accused Features: The complaint alleges infringement through the generation and transmission of a frame (e.g., a PPDU frame) that includes a series of time slots and a guard period (e.g., cyclic shifts) added to the series of time slots. (Compl. ¶¶173-174).

III. The Accused Instrumentality

Product Identification

  • The complaint names a range of Acer’s Wi-Fi compliant devices, including the Acer Halo Smart Speaker, various Iconia and Enduro tablets, numerous Chromebook models (such as the Chromebook 514, Spin 513, and Tab 10), and other devices like projectors and monitors (Compl. ¶¶7, 8, 23). The Acer Chromebook 514 is used as a representative example throughout the infringement allegations (Compl. ¶36).

Functionality and Market Context

  • The accused functionality centers on the products' compliance with modern Wi-Fi standards, specifically IEEE 802.11n, 802.11ac, and/or 802.11ax (also known as Wi-Fi 6) (Compl. ¶¶23, 34). The complaint alleges these products incorporate processors and software configured to perform adaptive modulation and multi-antenna (MIMO) signal processing as defined by these standards. This includes selecting a Modulation and Coding Scheme (MCS) based on channel quality and generating and processing complex multi-stream data packets, such as High-Throughput (HT) mixed format Physical Layer Protocol Data Units (PPDUs) (Compl. ¶¶37, 56, 75). The complaint positions the defendants as one of the largest electronics manufacturers in the United States, suggesting significant market presence for the accused products (Compl. ¶4).

IV. Analysis of Infringement Allegations

U.S. Patent No. 7,359,457 Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
a frame configuration determiner that determines a modulation system from among a plurality of modulation systems based on a communication situation; The Accused Products utilize a Modulation and Coding Scheme (MCS) value, selected from a plurality of possible values based on a channel quality assessment, to determine the modulation for a transmission. ¶37 col. 3:35-44
a first symbol generator that modulates a digital transmission signal according to the modulation system determined by the frame configuration determiner... The Accused Products generate a first data symbol (the Data portion of a Wi-Fi packet) that is modulated according to the selected MCS value. This generates a first quadrature baseband signal, such as a 16-QAM modulated signal. ¶38 col. 4:15-21
a second symbol generator that modulates the digital transmission signal according to a predetermined modulation system and that generates a second symbol... The Accused Products generate a second data symbol (the HT-SIG portion of a Wi-Fi packet) that is modulated according to a predetermined modulation system, such as Quadrature Phase-Shift Keying (QBPSK), regardless of the modulation selected for the first data symbol. ¶40 col. 6:15-22

Identified Points of Contention

  • Scope Questions: A central question may be whether the functional blocks described in the complaint, which are based on the IEEE 802.11 standard, map onto the patent's distinct "determiner" and "generator" limitations. For instance, does a single, software-driven Wi-Fi chipset that performs all these functions in an integrated manner meet the claim requirement for separate "first symbol generator" and "second symbol generator" elements as potentially depicted in the patent’s block diagrams? (’457 Patent, Fig. 1).
  • Technical Questions: The complaint alleges that the HT-SIG portion of a Wi-Fi packet is modulated according to a "predetermined modulation system" (Compl. ¶40). The court may need to consider whether this modulation is truly "predetermined" in the context of the patent or if it also varies in a way not accounted for by the infringement allegations. The 16-QAM constellation diagram provided in the complaint illustrates a "quadrature signal" as alleged in the infringement theory (Compl. p. 14).

U.S. Patent No. 7,688,901 Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
generating a plurality of modulation signals each of which is to be transmitted from a different one of a plurality of antennas... The Accused Products generate multiple modulation signals (e.g., HT-mixed format PPDUs) intended for simultaneous transmission from multiple antennas to create multiple spatial streams. ¶56 col. 2:1-3
wherein each modulation signal to include one or more preamble symbol groups each consisting of a plurality of preamble symbols used for demodulation... Each OFDM symbol within the modulation signals comprises a pilot symbol sequence containing four pilot symbols which are used by the receiver for demodulation. ¶56 col. 2:16-18
wherein the one or more preamble symbol groups... are orthogonal to other preamble symbol groups... with zero mutual correlation among the plurality of modulation signals The pilot symbol sequences corresponding to different spatial streams are orthogonal to each other at the same temporal points, exhibiting zero mutual correlation. ¶57 col. 2:18-22
each preamble symbol group consisting of preamble symbols the quantity of which is greater than that of the plurality of modulation signals to be transmitted Each pilot symbol sequence contains four pilot symbols, which is greater than the two or three modulation signals (spatial streams) transmitted by the Accused Products. ¶57 col. 2:40-44
transmitting the plurality of modulation signals... in an identical frequency band The Accused Products transmit the multiple modulation signals from multiple antennas within the same channel (e.g., a 20 MHz channel width). ¶58 col. 2:47-49

Identified Points of Contention

  • Scope Questions: The claim recites "preamble symbol groups." The complaint's theory of infringement maps this term to "pilot symbol sequence[s]" that are part of each OFDM symbol in a transmission (Compl. ¶¶56-57). A point of contention may be whether these interspersed pilot symbols qualify as "preamble symbol groups" as that term is used and defined within the patent, which might imply symbols located in a distinct preamble section of a transmission frame.
  • Technical Questions: The complaint alleges that the number of pilot symbols (four) is greater than the number of modulation signals (two or three) (Compl. ¶57). An evidentiary question may arise regarding how the "plurality of modulation signals to be transmitted" is counted in all operating modes of the accused devices and whether this condition is always met.

V. Key Claim Terms for Construction

’457 Patent

  • The Term: "communication situation"
  • Context and Importance: This term defines the input that triggers the adaptive modulation claimed in claim 1. The complaint equates this term with "information associated with a channel quality assessment" from the IEEE 802.11 standard (Compl. ¶37). The scope of this term will be critical; if construed narrowly to require specific information not present in a standard channel quality assessment, the infringement allegation could be challenged.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The specification states the determiner "judges the communication situation based on transmission path information which shows the degree of fluctuations of the transmission path due to fading and data transmission speed information" (’457 Patent, col. 3:35-40). This suggests a range of possible inputs.
    • Evidence for a Narrower Interpretation: The description notes that the object is to flexibly improve efficiency and quality according to "fluctuations in the transmission path and the level of a reception signal" (’457 Patent, col. 2:1-3). A defendant might argue that the "communication situation" must encompass both of these specific factors, not just a general "channel quality" metric.

’901 Patent

  • The Term: "preamble symbol groups"
  • Context and Importance: This term is central to the invention's structure. The complaint alleges that the "pilot symbol sequence" within each OFDM symbol of an IEEE 802.11 transmission meets this limitation (Compl. ¶56). Practitioners may focus on this term because its definition will determine whether the patent's claims, which use the word "preamble," can read on pilot symbols that are interspersed throughout a data transmission rather than being confined to a dedicated preamble field at the start of a packet.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The patent abstract refers to "preamble symbols used for demodulation," which could be interpreted functionally to include any symbols used for this purpose, regardless of their location in the frame.
    • Evidence for a Narrower Interpretation: The consistent use of the word "preamble" throughout the claims may suggest an intent to limit the scope to symbols located in the formal preamble portion of a transmission frame, as distinct from the data-carrying portion where pilot symbols are also found.

VI. Other Allegations

Indirect Infringement

  • The complaint alleges that Acer actively induces infringement by its distributors, customers, and end-users. The alleged affirmative steps include "creating advertisements that promote the infringing use," providing "instructions or manuals," and "testing wireless networking features" that direct users to operate the Accused Products in an infringing manner (Compl. ¶¶46, 65, 83).

Willful Infringement

  • The complaint asserts willful infringement based on Acer’s alleged knowledge of the patents since at least November 8, 2021, the date it allegedly received a notice letter from Redwood. The allegation is further supported by the claim that Acer was given access to a data room with additional materials on January 14, 2022, but continued its allegedly infringing conduct despite an "objectively high likelihood of infringement" (Compl. ¶¶6, 45, 47, 64, 66).

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

  • A core issue will be one of definitional scope: can claim terms rooted in the patents’ specific disclosures, such as "preamble symbol group" (’901 Patent) and "second symbol generator" (’457 Patent), be construed to cover the integrated, standardized functionalities of modern Wi-Fi chipsets, such as interspersed "pilot symbol sequences" and unified packet generation processes?
  • A second key question will be one of evidentiary mapping: to what extent can Plaintiff demonstrate, through technical evidence, that the accused Acer products, by practicing the IEEE 802.11n/ac/ax standards, necessarily perform each and every step of the asserted method claims or contain each and every element of the asserted apparatus claims? The dispute may focus on subtle operational differences between the standardized implementation and the specific requirements of the patent claims.