DCT
6:22-cv-01280
Redwood Tech LLC v. Askey Computer Corp
Key Events
Complaint
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Redwood Technologies, LLC (Texas)
- Defendant: Askey Computer Corporation (Taiwan)
- Plaintiff’s Counsel: Nelson Bumgardner Conroy PC
- Case Identification: 6:22-cv-01280, W.D. Tex., 12/15/2022
- Venue Allegations: Plaintiff alleges venue is proper because Defendant is a foreign entity, which may be sued in any judicial district.
- Core Dispute: Plaintiff alleges that Defendant’s Wi-Fi compliant devices, including mesh networking products, infringe four patents related to wireless communication frame structures, power management, and signal processing.
- Technical Context: The patents relate to foundational technologies for wireless local area networking (WLAN) systems, such as those compliant with the IEEE 802.11 (Wi-Fi) standard.
- Key Procedural History: The complaint alleges that Plaintiff provided Defendant with notice of infringement via a letter received on May 17, 2022, followed by several emails with additional information, which may form the basis for allegations of willful infringement.
Case Timeline
| Date | Event |
|---|---|
| 2000-12-08 | U.S. Patent No. 7,983,140 Priority Date |
| 2003-08-07 | U.S. Patent No. 7,917,102 Priority Date |
| 2004-03-01 | U.S. Patent No. 8,111,671 Priority Date |
| 2004-03-01 | U.S. Patent No. 9,462,536 Priority Date |
| 2011-03-29 | U.S. Patent No. 7,917,102 Issued |
| 2011-07-19 | U.S. Patent No. 7,983,140 Issued |
| 2012-02-07 | U.S. Patent No. 8,111,671 Issued |
| 2016-10-04 | U.S. Patent No. 9,462,536 Issued |
| 2022-05-17 | Defendant allegedly received letter providing notice of infringement |
| 2022-06-27 | Defendant allegedly received follow-up email regarding infringement |
| 2022-07-12 | Defendant allegedly received follow-up email regarding infringement |
| 2022-07-27 | Defendant allegedly received follow-up email regarding infringement |
| 2022-08-11 | Defendant allegedly received follow-up email regarding infringement |
| 2022-12-15 | Complaint Filing Date |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 7,917,102 - Radio Transmitting Apparatus and Radio Transmission Method (Issued Mar. 29, 2011)
The Invention Explained
- Problem Addressed: In multiple-input multiple-output (MIMO) wireless systems, the number of transmitting antennas may change to adapt to the radio environment. The patent's background explains that this change in the number of transmitted signals causes the received signal level to fluctuate, which can lead to quantization errors at the receiver's analog-to-digital converter and degrade reception quality (’102 Patent, col. 2:1-11).
- The Patented Solution: The patent proposes a radio transmitting apparatus that arranges different types of pilot and control signals within a transmission frame in a specific order to improve reception. The asserted claim requires a "first gain control signal" to be placed before a "frequency offset estimation signal," and a "second gain control signal" to be placed after the frequency offset signal but before a "channel fluctuation estimation signal" (’102 Patent, cl. 3). This structure is intended to improve the accuracy of receiver-side functions like gain control and frequency synchronization (’102 Patent, col. 49:15-26).
- Technical Importance: Precise gain control and frequency synchronization are fundamental for reliable high-speed data reception in complex wireless environments, and optimizing the preamble structure of a transmission frame can directly impact the performance of these functions (’102 Patent, col. 2:6-11).
Key Claims at a Glance
- The complaint asserts independent claim 3 (Compl. ¶34).
- The essential elements of apparatus claim 3 are:
- A transmission frame forming section that creates a frame including a frequency offset estimation signal, a channel fluctuation estimation signal, and a gain control signal.
- A transmitting section to transmit the frame.
- The frame includes a first gain control signal and a second gain control signal.
- The first gain control signal is arranged before the frequency offset estimation signal.
- The second gain control signal is arranged after the frequency offset estimation signal and before the channel fluctuation estimation signal.
- The complaint does not explicitly reserve the right to assert dependent claims.
U.S. Patent No. 7,983,140 - Transmitting Apparatus, Receiving Apparatus, and Communication System for Formatting Data (Issued Jul. 19, 2011)
The Invention Explained
- Problem Addressed: The patent describes a problem in wireless systems where an interfering signal from a distant base station using the same channel can arrive slightly after a desired signal. This delay can cause the interfering signal to corrupt the end of one data frame and the beginning of the next, potentially leading to the loss of two consecutive frames (’140 Patent, col. 3:1-12).
- The Patented Solution: The invention proposes inserting a "frame guard period," described as a non-signal period, at the end of a series of data-carrying "time slots" that constitute a transmission frame (’140 Patent, Abstract; col. 4:15-18). This guard period acts as a buffer, absorbing the end of a delayed interfering signal so that it does not corrupt the subsequent data frame, thereby limiting data loss to a single frame (’140 Patent, col. 4:8-14).
- Technical Importance: This frame formatting technique enhances a communication system's resilience to co-channel interference, which allows for more aggressive frequency reuse in cellular network planning and improves overall spectrum efficiency (’140 Patent, col. 3:32-44).
Key Claims at a Glance
- The complaint asserts independent claim 1 (Compl. ¶47).
- The essential elements of apparatus claim 1 are:
- In an OFDM system, a front-end unit for converting a signal into a time slot.
- A frame generator that creates a frame with a series of "n" (more than 1) time slots and adds a "frame guard period" to that series.
- Each time slot contains an effective symbol period and its own guard period.
- The length of the series of "n" time slots is less than the total length of the frame.
- A back-end unit for transmitting the generated frame as a radio signal.
- The complaint does not explicitly reserve the right to assert dependent claims.
U.S. Patent No. 8,111,671 - Wireless Communication System, Wireless Communication Apparatus, Wireless Communication Method and Computer Program (Issued Feb. 7, 2012)
- Technology Synopsis: This patent addresses power management in a wireless network. The invention describes a communication station that transmits a beacon containing timing information indicating specific time periods during which a receiving station "cannot receive a transmission," thereby allowing the receiving station to enter a power-saving sleep mode during those defined periods to conserve energy without losing network synchronization (’671 Patent, Abstract; cl. 4).
- Asserted Claims: Claim 4 (Compl. ¶61).
- Accused Features: The complaint alleges that Defendant's mesh devices infringe by transmitting beacons with a "Mesh Awake Window element" and "Mesh Power Save Level field," which allegedly function to inform other stations of periods when they can and cannot receive transmissions (Compl. ¶62).
U.S. Patent No. 9,462,536 - Wireless Communication System, Wireless Communication Apparatus, Wireless Communication Method, and Computer Program (Issued Oct. 4, 2016)
- Technology Synopsis: This patent relates to coordinating transmission opportunities in a wireless network. The invention describes a method where a device outputs a modulated signal based on information specifying the "duration" and "periodicity" of transmission windows. The method also involves setting an "offset" that defines the beginning of the transmission opportunity relative to a larger transmission interval, enabling synchronized communication and power-saving schedules (’536 Patent, Abstract; cl. 3).
- Asserted Claims: Claim 3 (Compl. ¶74).
- Accused Features: The accused mesh devices allegedly infringe by using a "Mesh Beacon" that contains a "Mesh Awake Window" to specify duration and a "Beacon Timing element" to specify periodicity, and by performing a "TBTT adjustment procedure" to set an offset (Compl. ¶76, ¶77).
III. The Accused Instrumentality
- Product Identification: The complaint identifies two categories of accused products. The first includes a wide range of devices supporting IEEE 802.11n, 802.11ac, and/or 802.11ax Wi-Fi standards (Compl. ¶22). The second is a subset of those devices that operate as mesh networking devices compliant with the IEEE 802.11 standard (Compl. ¶22). A non-exhaustive list of over 80 specific product models is provided (Compl. ¶22).
- Functionality and Market Context: The complaint alleges the accused products are Wi-Fi compliant devices that incorporate the patented technologies by virtue of implementing the IEEE 802.11-2016 standard (Compl. ¶35, ¶48, ¶62, ¶74). Plaintiff asserts that Defendant markets and sells these products throughout the United States via distributors and customers including Verizon, T-Mobile, and Amazon (Compl. ¶21, ¶26). No probative visual evidence provided in complaint.
IV. Analysis of Infringement Allegations
The infringement allegations for all asserted patents are based on the theory that the accused products, by complying with designated sections of the IEEE 802.11-2016 standard, necessarily practice the claimed inventions (Compl. ¶35, ¶49, ¶62, ¶76).
7,917,102 Infringement Allegations
| Claim Element (from Independent Claim 3) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a transmission frame forming section that forms a transmission frame which includes a frequency offset estimation signal . . . a channel fluctuation estimation signal . . . and a gain control signal | The Accused Products comprise circuitry that forms an HT-mixed format PPDU frame, which includes subframes that serve as the required signals. | ¶35 | col. 10:47-51 |
| said transmission frame includes a first gain control signal and a second gain control signal | The HT-mixed format PPDU allegedly comprises a first gain control signal in its L-STF subframe and a second gain control signal in its HT-STF subframe. | ¶36 | col. 49:17-19 |
| the first gain control signal is arranged prior to the frequency offset estimation signal | The L-STF subframe is allegedly arranged prior to the L-LTF subframe (the alleged frequency offset estimation signal). | ¶36 | col. 49:20-22 |
| the second gain control signal is arranged subsequent to the frequency offset estimation signal and prior to the channel fluctuation estimation signal | The HT-STF subframe is allegedly arranged subsequent to the L-LTF subframe and prior to the HT-LTF subframe (the alleged channel fluctuation estimation signal). | ¶36 | col. 49:23-26 |
- Identified Points of Contention:
- Technical Questions: A primary question will be whether the subframes of the IEEE 802.11 standard (L-STF, HT-STF) function as "gain control signals" in the manner claimed by the patent. A defendant may argue these subframes have other primary purposes (e.g., signal detection, synchronization) and that mapping them to the "gain control signal" limitation is a mischaracterization of their technical operation.
- Scope Questions: The analysis may focus on whether mere compliance with the IEEE 802.11 standard is sufficient to prove infringement of this apparatus claim, or if Plaintiff must provide evidence of the specific circuitry and operational modes of the accused products that perform the claimed functions.
7,983,140 Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a frame generator for generating a frame that includes a series of n (greater than 1) time slots and a frame guard period added to the series of n time slots | The Accused Products allegedly generate a PPDU frame comprising a series of time slots (OFDM symbols) and add "cyclic shifts" to this series, which are alleged to be the claimed "frame guard period." | ¶49 | col. 12:26-34 |
| each time slot including an effective symbol period and guard period added to the effective symbol period | Each time slot in the PPDU frame allegedly comprises an effective symbol period and has a guard period added at its start. | ¶49 | col. 2:1-4 |
| where the length of the series of n time slots is less than the length of the frame | The complaint alleges the length of the series of time slots is less than the total length of the PPDU frame. | ¶49 | col. 4:15-18 |
- Identified Points of Contention:
- Scope Questions: A central dispute may arise over the definition of "frame guard period." The complaint alleges that "cyclic shifts" meet this limitation (Compl. ¶49). However, the patent specification describes the "frame guard period" as a single, non-signal period added to the end of a series of time slots to prevent inter-frame interference (’140 Patent, Abstract; Fig. 5). In contrast, "cyclic shifts" (or cyclic prefixes) in OFDM are typically copies of the end of a symbol added to the beginning of that same symbol to prevent inter-symbol interference. This suggests a potential mismatch in the structure, location, and technical purpose of the claimed feature versus the accused functionality.
V. Key Claim Terms for Construction
For the ’102 Patent:
- The Term: "gain control signal"
- Context and Importance: The infringement theory depends on mapping two separate subframes from the IEEE 802.11 standard preamble (L-STF and HT-STF) to the two "gain control signal" limitations in the claim. The definition of this term will be critical to determining if this mapping is technically and legally sound.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: Claim 1 provides a functional definition: "a gain control signal for performing gain control of the modulated signal at the receiving apparatus" (’102 Patent, cl. 1). Plaintiff may argue that any signal portion used by the receiver for gain control meets this definition.
- Evidence for a Narrower Interpretation: The patent specification illustrates a "gain control symbol" as a distinct, dedicated component of the frame structure (e.g., ’102 Patent, Fig. 29D, item 2702). Defendant may argue that the term should be construed as a dedicated signal for that purpose, not a multi-purpose preamble field.
For the ’140 Patent:
- The Term: "frame guard period"
- Context and Importance: The viability of the infringement allegation for the ’140 patent hinges on whether this term can be construed to read on the "cyclic shifts" (cyclic prefixes) used in the accused products' OFDM signals.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The stated purpose of the invention is to mitigate interference and prevent frame loss (’140 Patent, Abstract). Plaintiff may argue that any structural element that serves this general purpose, including a cyclic prefix, should be covered.
- Evidence for a Narrower Interpretation: The specification consistently describes and depicts the "frame guard period" as a singular, non-signal period "added to the series of n time slots" at the end of a frame (’140 Patent, Abstract; cl. 1; Fig. 5). This language suggests a structure that is distinct from a cyclic prefix, which is a portion of a symbol prepended to that same symbol and repeated for every symbol in the frame.
VI. Other Allegations
- Indirect Infringement: The complaint alleges induced infringement for all asserted patents. It claims Defendant had knowledge of the patents at least as of May 17, 2022, and encourages infringement by providing instructions, user manuals, and marketing materials that direct customers to use the accused Wi-Fi devices in their infringing, standard-compliant manner (e.g., Compl. ¶39, ¶53, ¶66, ¶80).
- Willful Infringement: Willfulness is alleged for all asserted patents, based on Defendant's alleged knowledge from the pre-suit notice letter and subsequent emails. The complaint alleges that Defendant continued its infringing conduct despite an objectively high likelihood that its actions constituted infringement (e.g., Compl. ¶40, ¶54, ¶67, ¶81).
VII. Analyst’s Conclusion: Key Questions for the Case
This litigation will likely depend on the resolution of several core technical and legal questions concerning the relationship between the patent claims and the IEEE 802.11 standard.
- A central issue will be one of claim scope vs. standard implementation: does compliance with the IEEE 802.11 standard, as alleged, necessarily equate to infringement of the asserted claims? The court will need to determine whether the functions and structures described in the standard are coextensive with those recited in the claims, or if there are material differences that place standard-compliant products outside the patents' scope.
- A key question for the ’140 patent will be one of definitional scope: can the term "frame guard period," described and depicted in the patent as a single non-signal buffer at the end of a frame, be construed to cover the "cyclic shifts" (cyclic prefixes) that are added to the beginning of each OFDM symbol in the accused products?
- For the ’102 patent, a critical evidentiary question will be one of functional equivalence: do the preamble subframes of the 802.11 standard perform the specific function of a "gain control signal" as claimed, or is this an improper mapping of a multi-purpose signal element onto a specific claim limitation?