2:23-cv-00135
Redwood Tech LLC v. Texas Instruments Inc
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Redwood Technologies, LLC (Texas)
- Defendant: Texas Instruments Incorporated (Delaware)
- Plaintiff’s Counsel: Nelson Bumgardner Conroy PC
- Case Identification: 2:23-cv-00135, E.D. Tex., 03/29/2023
- Venue Allegations: Plaintiff alleges venue is proper because Defendant Texas Instruments maintains regular and established places of business within the Eastern District of Texas.
- Core Dispute: Plaintiff alleges that Defendant’s Wi-Fi compliant semiconductor devices infringe five patents related to adaptive modulation, MIMO signal processing, and channel estimation in wireless communications.
- Technical Context: The patents relate to techniques for improving the speed and reliability of wireless data transfer, such as those used in modern Wi-Fi (IEEE 802.11) standards, by dynamically adapting to changing channel conditions and managing transmissions from multiple antennas.
- Key Procedural History: The complaint alleges that Defendant had pre-suit knowledge of the asserted patents via notice letters sent in November 2021 and May 2022. It further alleges Defendant was aware of two of the patents as a result of forward citations made during the prosecution of its own patents.
Case Timeline
| Date | Event |
|---|---|
| 1999-07-28 | Priority Date for U.S. Patent No. 7,359,457 |
| 2001-11-13 | Priority Date for U.S. Patent No. 7,688,901 |
| 2001-11-13 | Priority Date for U.S. Patent No. 7,974,371 |
| 2005-08-24 | Priority Date for U.S. Patent No. 8,284,866 |
| 2005-08-24 | Priority Date for U.S. Patent No. 9,374,209 |
| 2008-04-15 | U.S. Patent No. 7,359,457 Issues |
| 2010-03-30 | U.S. Patent No. 7,688,901 Issues |
| 2011-07-05 | U.S. Patent No. 7,974,371 Issues |
| 2012-10-09 | U.S. Patent No. 8,284,866 Issues |
| 2016-06-21 | U.S. Patent No. 9,374,209 Issues |
| 2021-11-04 | Plaintiff alleges first notice letter received by Defendant |
| 2022-05-23 | Plaintiff alleges second notice letter received by Defendant |
| 2023-03-29 | 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," issued April 15, 2008 (’457 Patent)
The Invention Explained
- Problem Addressed: The patent describes conventional digital radio systems as inefficient because they use a fixed modulation scheme and a fixed interval for inserting known 'pilot symbols' for channel estimation (’457 Patent, col. 1:45-56). This approach performs poorly when channel conditions fluctuate intensely and is inefficiently robust when channel conditions are good, preventing an increase in data transmission speed (’457 Patent, col. 1:50-56).
- The Patented Solution: The invention proposes a transmission apparatus that flexibly adapts to the 'communication situation' by changing the modulation system for data symbols and/or the insertion interval of known pilot symbols (’457 Patent, col. 2:58-63). A 'frame configuration determination section' analyzes information about the transmission path and required data speed to select an optimal configuration, thereby improving both data transmission efficiency and quality (’457 Patent, col. 3:36-48).
- Technical Importance: Adaptive modulation is a foundational technique for modern high-speed wireless systems, allowing devices to maximize data throughput in good channel conditions and maintain a reliable link in poor conditions.
Key Claims at a Glance
- The complaint asserts independent claim 1 (Compl. ¶21).
- Claim 1 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 reserves the right to assert additional claims, including dependent claims (Compl. ¶19).
U.S. Patent No. 7,688,901 - "Transmission Method, Transmission Apparatus, and Reception Apparatus," issued March 30, 2010 (’901 Patent)
The Invention Explained
- Problem Addressed: The patent identifies a difficulty in accurately estimating communication channels in systems that multiplex signals, such as Multiple-Input Multiple-Output (MIMO) systems (’901 Patent, col. 1:45-49). Without proper channel estimation, a receiver cannot effectively separate the multiplexed signals, which degrades performance (’901 Patent, col. 1:41-45).
- The Patented Solution: The invention describes a method where multiple modulation signals, intended for different antennas, include 'preamble symbol groups' used for demodulation. These groups are inserted at the same time across all signals and are mathematically 'orthogonal' to each other (’901 Patent, col. 2:16-18). This orthogonality allows a receiver to easily isolate the symbols from each channel, which in turn facilitates an accurate channel estimation and successful demultiplexing of the data streams (’901 Patent, col. 2:18-22).
- Technical Importance: Robust channel estimation is critical to the functioning of MIMO systems, which rely on separating multiple spatial data streams to achieve significant increases in wireless data rates.
Key Claims at a Glance
- The complaint asserts independent claim 1 (Compl. ¶39).
- Claim 1 requires:
- Generating a plurality of modulation signals for different antennas, each signal including one or more preamble symbol groups used for demodulation.
- Inserting the preamble symbol groups at the same temporal points in each signal, where the groups are orthogonal to each other with zero mutual correlation.
- Each preamble symbol having a non-zero amplitude, and the quantity of symbols in each group being greater than the number of modulation signals.
- Transmitting the plurality of modulation signals from the antennas in an identical frequency band.
- The complaint reserves the right to assert additional claims (Compl. ¶37).
U.S. Patent No. 7,974,371 - "Communication Method and Radio Communication Apparatus," issued July 5, 2011 (’371 Patent)
Technology Synopsis
The patent addresses a communication method that switches between transmitting a single modulation signal from one antenna and transmitting a plurality of multiplexed modulation signals from a plurality of antennas (’371 Patent, col. 4:27-31). The selection between these two methods is based on the estimated radio-wave propagation environment, allowing a transmitter to choose between a single-stream mode and a multi-stream MIMO mode to optimize the data transmission rate and reliability (’371 Patent, col. 5:4-16).
Asserted Claims
The complaint asserts independent claim 14 (Compl. ¶57).
Accused Features
The complaint alleges that the Accused Products' circuitry for selecting a Modulation and Coding Scheme (MCS), which determines whether to use a single spatial stream or multiple spatial streams for transmission based on channel quality, infringes the ’371 patent (Compl. ¶¶ 58-59).
U.S. Patent No. 8,284,866 - "OFDM Transmission Signal Generation Apparatus and Method, and OFDM Reception Data Generation Apparatus and Method," issued October 9, 2012 (’866 Patent)
Technology Synopsis
The patent describes a technical solution for improving the accuracy of frequency offset and transmission path estimation in MIMO-OFDM communication systems (’866 Patent, col. 1:18-24). The invention proposes assigning orthogonal sequences to pilot carriers located at the same subcarrier positions across the different OFDM signals transmitted from multiple antennas. This assignment of orthogonal sequences in the time domain allows for high-accuracy estimation even when pilot symbols from different antennas are multiplexed together (’866 Patent, col. 3:4-10).
Asserted Claims
The complaint asserts independent claim 1 (Compl. ¶74).
Accused Features
The complaint accuses the products' spatial mapper, which forms multiple OFDM signals with pilot carriers at identical positions, and their Inverse Fourier transform section, which prepares these signals for simultaneous transmission. The use of orthogonal pilot sequences for different spatial streams is alleged to meet the claim limitations (Compl. ¶¶ 75-76).
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 (’209 Patent)
Technology Synopsis
The patent discloses a transmission apparatus that generates signals containing preamble, pilot, and data information. A key aspect is the use of orthogonal sequences for pilot symbol sequences assigned to pilot carriers to enable high-accuracy frequency offset estimation (’209 Patent, col. 3:9-15). Additionally, the invention involves multiplying the preamble by a factor so that its average reception power corresponds to the average reception power of the data, which can improve signal processing at the receiver (’209 Patent, col. 29:90-93).
Asserted Claims
The complaint asserts independent claim 11 (Compl. ¶91).
Accused Features
Infringement is alleged based on the generation of transmission signals that include a PHY preamble, pilot symbols, and data information. The complaint points to the use of normalization factors to achieve consistent average power and the arrangement of orthogonal pilot sequences for different space-time streams (Compl. ¶¶ 92-97).
III. The Accused Instrumentality
Product Identification
The complaint identifies Defendant’s devices that are compliant with the IEEE 802.11n, 802.11ac, and/or 802.11ax Wi-Fi standards (Compl. ¶15). The WL1807MOD WiLink 8 industrial dual band combo module is named as an exemplary Accused Product for all infringement counts (Compl. ¶¶ 21, 39, 57, 74, 91).
Functionality and Market Context
The accused products are Wi-Fi modules that provide wireless connectivity. The complaint alleges their infringing functionality is tied to their compliance with the IEEE 802.11 standards. This includes selecting a Modulation and Coding Scheme (MCS) based on channel quality assessments to determine the modulation type (e.g., QAM), coding rate, and number of spatial streams (MIMO) for data transmission (Compl. ¶22). The products are alleged to generate packets containing distinct fields, such as data symbols and signaling fields (e.g., HT-SIG), using different, specified modulation schemes (Compl. ¶¶ 23, 25). For MIMO operations, they are alleged to use orthogonal pilot symbol sequences to enable demodulation of multiple spatial streams (Compl. ¶41). The complaint includes a block diagram from a Texas Instruments datasheet illustrating the architecture of the WL1807MOD, showing its MAC/PHY, radio frequency, and antenna components (Compl. p. 6).
IV. Analysis of Infringement Allegations
’457 Patent 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, determined based on a channel quality assessment, to select the modulation system for data transmission. | ¶22 | col. 3:36-48 |
| a first symbol generator that modulates a digital transmission signal according to the modulation system determined by the frame configuration determiner and that generates a first symbol, the first symbol comprising a first quadrature baseband signal; and | The products generate data symbols that are modulated according to the selected MCS value (e.g., 16-QAM). This modulated symbol is a first quadrature baseband signal, as illustrated in the complaint's constellation diagram. | ¶23 | col. 4:16-24 |
| a second symbol generator that modulates the digital transmission signal according to a predetermined modulation system and that generates a second symbol, the second symbol comprising a second quadrature baseband signal. | The products generate a second symbol, such as the HT-SIG field in a Wi-Fi packet, which is modulated according to a predetermined system (e.g., QBPSK) and is a second quadrature baseband signal. | ¶25 | col. 15:16-23 |
Identified Points of Contention
- Scope Questions: The dispute may center on whether the accused product's standard-compliant selection of an MCS constitutes determining a modulation system based on a 'communication situation' as the term is used in the patent. A further question is whether the modulation scheme for the accused HT-SIG field (e.g., QBPSK) qualifies as 'predetermined' within the meaning of the claim, as the patent specification often describes this second symbol as a known pilot symbol or a simple BPSK symbol (’457 Patent, Abstract, col. 6:43-51).
- Technical Questions: A key question for the court will be how the complaint maps the functional blocks of the IEEE 802.11 standard (e.g., MAC/PHY procedures for rate selection) onto the claimed 'frame configuration determiner' and 'symbol generator' elements.
’901 Patent 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, where each modulation signal is to include one or more preamble symbol groups each consisting of a plurality of preamble symbols used for demodulation; | The Accused Products generate multiple modulation signals (e.g., HT-mixed format PPDUs) for transmission from multiple antennas in a MIMO configuration. These signals contain OFDM symbols which include pilot symbol sequences used by the receiver for demodulation. | ¶40 | col. 2:38-46 |
| inserting the one or more preamble symbol groups at the same one or more temporal points in each modulation signal, wherein the one or more preamble symbol groups at the one or more temporal points are orthogonal to other preamble symbol groups at the same one or more temporal points with zero mutual correlation...; | The products insert pilot symbol sequences corresponding to different spatial streams at the same temporal points, and these sequences are alleged to be orthogonal with zero mutual correlation per the IEEE 802.11 standard. | ¶41 | col. 2:16-18 |
| each preamble symbol having a non-zero amplitude, and 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; and | The pilot symbols are BPSK modulated, giving them a non-zero amplitude. Each pilot sequence allegedly contains four symbols, a quantity greater than the two or three modulation signals (spatial streams) transmitted by the Accused Products. | ¶41 | col. 2:8-15 |
| transmitting the plurality of modulation signals...from the plurality of antennas, respectively, in an identical frequency band. | The products transmit the multiple modulation signals from their respective antennas simultaneously within the same frequency channel (e.g., a 20 MHz Wi-Fi channel). | ¶42 | col. 2:4-7 |
Identified Points of Contention
- Scope Questions: A central issue may be the construction of 'preamble symbol group.' The defendant may argue that this term is limited to symbols in the packet preamble, whereas the plaintiff's theory reads it on pilot sequences embedded within the data-carrying OFDM symbols of a packet.
- Technical Questions: The infringement allegation appears to hinge on a direct mapping of the IEEE 802.11n standard's MIMO pilot structure to the claim language. The factual question will be whether the operation of the accused product's pilot symbol sequences fully aligns with all limitations of the asserted claim, including the orthogonality and quantity requirements.
V. Key Claim Terms for Construction
For the ’457 Patent
- The Term: 'communication situation'
- Context and Importance: This term defines the trigger for the claimed adaptive modulation. The scope of this term will be critical in determining whether the accused products' reliance on standardized channel quality metrics falls within the claim. Practitioners may focus on this term because its definition will control whether compliance with the IEEE 802.11 standard constitutes infringement.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The patent states the object is to improve efficiency and quality by adapting to 'fluctuations in the transmission path and the level of a reception signal,' suggesting any form of channel quality information could suffice (’457 Patent, col. 2:1-3).
- Evidence for a Narrower Interpretation: The detailed description specifies that the determination is based on 'transmission path information which shows the degree of fluctuations...due to fading and data transmission speed information,' which could be argued to require specific types of input not explicitly detailed in the complaint's allegations concerning the IEEE standard (’457 Patent, col. 3:39-43).
For the ’901 Patent
- The Term: 'preamble symbol group'
- Context and Importance: The plaintiff's infringement theory equates this term with the 'pilot symbol sequence' found within data-carrying OFDM symbols under the IEEE 802.11 standard. The viability of the infringement case for the ’901 patent may depend heavily on this construction.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The claim language itself defines the group's purpose as comprising 'symbols used for demodulation,' a functional definition that could arguably encompass pilot symbols regardless of their location in a packet (’901 Patent, cl. 1). The abstract likewise refers to a 'symbol for demodulation' (’901 Patent, Abstract).
- Evidence for a Narrower Interpretation: The term 'preamble' has a well-understood meaning in communications as the initial part of a data frame. A defendant may argue that the term's plain meaning limits the claim scope to symbols located in the packet's preamble, not those interleaved with data symbols.
VI. Other Allegations
Indirect Infringement
The complaint alleges that Defendant induces infringement by providing its customers with the accused Wi-Fi modules along with instructions, user manuals, advertisements, and technical support that encourage and facilitate the use of the infringing functionality (Compl. ¶¶ 31, 49). Knowledge is alleged based on pre-suit notice letters.
Willful Infringement
The complaint alleges willful infringement based on Defendant's continued infringing conduct after receiving notice of the asserted patents. This knowledge is alleged to stem from letters sent in November 2021 and May 2022, as well as from forward citations to the ’866 and ’209 patents during the prosecution of Defendant's own unrelated patents (Compl. ¶¶ 32, 50, 82, 103).
VII. Analyst’s Conclusion: Key Questions for the Case
- A core issue will be one of mapping standards to claims: to what extent do the specific, standardized implementations of adaptive modulation (MCS selection) and MIMO pilot structures in the IEEE 802.11 standard read on the particular claim limitations of the asserted patents? The case will likely involve a detailed comparison between the standard's operation and the patents' descriptions of a 'communication situation' (’457 Patent) and 'preamble symbol groups' (’901 Patent).
- A key legal question will be one of definitional scope: can the term 'preamble symbol group,' as used in the ’901 patent, be construed to cover pilot sequences embedded within data-carrying OFDM symbols, or is its meaning confined to the initial preamble of a packet? The outcome of this construction could be dispositive for that patent.
- A central evidentiary question will concern knowledge and willfulness: what evidence can Plaintiff produce to show that Defendant had the requisite knowledge and intent for inducement and willfulness, particularly for the patents where knowledge is alleged based on forward citations during patent prosecution rather than direct notice?