DCT

6:20-cv-00496

WSOU Investments LLC v. ZTE Corp

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Key Events
Amended Complaint

I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 6:20-cv-00496, W.D. Tex., 11/06/2020
  • Venue Allegations: Plaintiff alleges venue is proper in the Western District of Texas because Defendants ZTE (USA) and ZTE (TX) maintain places of business in Austin, and Defendant ZTE Corp. has described a research-and-development center in Austin.
  • Core Dispute: Plaintiff alleges that Defendant’s Long Term Evolution (LTE) capable telecommunications equipment, including base stations and smartphones, infringes a patent related to efficiently selecting frequency sub-carriers for wireless data transmission.
  • Technical Context: The technology addresses methods for optimizing resource allocation in multi-carrier wireless systems (e.g., LTE) by reducing the signaling overhead required to inform a user device which radio frequencies to use for data reception.
  • Key Procedural History: The complaint was filed on November 6, 2020. Subsequently, an Inter Partes Review (IPR) proceeding, IPR2021-00699, was filed against the asserted patent on March 31, 2021. The U.S. Patent and Trademark Office issued a certificate for this IPR on April 11, 2023, confirming that all claims of the patent (1-18) were cancelled. This post-complaint event is dispositive of the patent's validity and, by extension, the infringement claims.

Case Timeline

Date Event
2005-08-01 ’534 Patent Priority Date
2009-10-20 ZTE announces opening of LTE testing laboratory in Richardson, TX
2010-06-22 ’534 Patent Issue Date
2019-10-15 ZTE announces Blade Vantage 2 smartphone
2019-11-20 ZTE advertises Blade 10 and Axon 10 Pro smartphones
2020-11-06 Complaint Filing Date
2021-03-31 Inter Partes Review (IPR2021-00699) filed against the ’534 Patent
2023-04-11 IPR Certificate issues, cancelling all claims of the ’534 Patent

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

  • Patent Identification: U.S. Patent No. 7,742,534, METHOD FOR TRANSMITTING USER DATA IN A MULTI-CARRIER RADIO COMMUNICATION SYSTEM, AND CORRESPONDING RECEIVER, issued June 22, 2010.

The Invention Explained

  • Problem Addressed: In multi-carrier wireless systems like Orthogonal Frequency Division Multiplexing (OFDM), a base station must tell a mobile device which specific frequency sub-carriers to use for data transmission. The patent’s background notes that explicitly communicating the full list of sub-carriers consumes significant signaling bandwidth, which reduces the effective data rate available to the user (’534 Patent, col. 4:54-63).
  • The Patented Solution: To solve this, the patent proposes a more efficient signaling method. Instead of sending the entire list of sub-carriers, the transmitter sends a more compact "indication related to a threshold." The receiver, which independently determines the quality of all available sub-carriers (e.g., by measuring the signal-to-interference ratio), uses this simple indication to deduce which sub-carriers it should listen to for data. For example, the indication could be a number representing how many of the best-quality sub-carriers to use, or a quality value that sub-carriers must exceed to be selected (’534 Patent, Abstract; col. 3:6-14).
  • Technical Importance: This approach was intended to improve the efficiency of resource allocation in emerging 4G/LTE systems by reducing control channel overhead, thereby freeing up more bandwidth for user data transmission (’534 Patent, col. 4:2-7).

Key Claims at a Glance

  • The complaint asserts at least independent claim 1.
  • Independent Claim 1 of the ’534 Patent recites the key elements of a method:
    • A receiver determining quality levels for a plurality of sub-carriers.
    • The receiver sending these quality levels to a transmitter.
    • Selecting a set of sub-carriers for data transmission based on those quality levels.
    • The transmitter sending an "indication related to a threshold" to the receiver before data transmission.
    • This indication, combined with the receiver's known quality levels, enables the receiver to "deduce" the set of sub-carriers.
    • The receiver selecting the set of sub-carriers as a function of the indication and the quality levels.
  • The complaint’s prayer for relief references infringement of "one or more claims," preserving the right to assert other claims.

III. The Accused Instrumentality

Product Identification

The complaint identifies two categories of accused products: ZTE network elements, such as Base Stations (ZXSDR BS8700, BS8800, and BS8906), and ZTE LTE smartphones, including the ZTE Blade 10 and ZTE Axon 10 Pro (Compl. ¶¶26-27).

Functionality and Market Context

The accused products are components of an LTE wireless communication system. The complaint alleges these products operate according to the LTE standard, which uses OFDM for downlink transmissions (Compl. ¶32). The infringement theory centers on the standardized process for Channel Quality Indicator (CQI) reporting. In this process, a user equipment (UE), like a smartphone, measures the quality of various sub-carriers and sends a CQI report to the base station (eNodeB) (Compl. ¶33). The eNodeB can then trigger an "aperiodic" CQI report by sending a request on a control channel (PDCCH), which the complaint alleges constitutes the patented "indication" (Compl. ¶¶33, 35). The complaint notes ZTE's deployment of commercial LTE networks and testing facilities in North America as evidence of the products' use and market presence (Compl. ¶¶28-29). The complaint provides a table from an ETSI standard, 'Table 7.2.1-1: CQI and PMI Feedback Types for PUSCH CSI reporting Modes,' which illustrates different reporting modes, including 'UE Selected (subband CQI)' modes alleged to be the patented invention (Compl. p. 12).

IV. Analysis of Infringement Allegations

’534 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
at the receiver, determining quality levels for said sub-carriers; The user equipment (UE) measures the quality level of sub-carriers to generate a Channel Quality Indicator (CQI) report. ¶33 col. 5:60-64
sending said quality levels from said receiver to said transmitter; The UE sends the CQI report, containing the quality information, to the eNodeB (transmitter) on the Physical Uplink Shared Channel (PUSCH). ¶33 col. 5:19-22
selecting, based on said quality levels, a set of sub-carriers on which said user data is to be transmitted... The complaint alleges the UE selects a set of preferred sub-bands based on high CQI as part of the "UE-selected (sub-band CQI) CSI reporting mode." ¶36 col. 3:4-10
from said transmitter, before transmission of said user data, sending an indication related to a threshold... The eNodeB (transmitter) sends a CSI request bit in the Downlink Control Information (DCI) format on the PDCCH, which triggers an aperiodic CQI report. The complaint alleges this request and the configured CSI reporting mode (e.g., Mode 2-0) is the "indication." ¶¶35, 40 col. 5:49-54
...said indication and said quality levels enabling said receiver to deduce said set of sub-carriers on which said user data is to be transmitted; and Based on the CSI reporting mode indicated by the eNodeB, the UE is able to select the 'M' preferred sub-bands that have high CQI. ¶41 col. 6:4-10
at said receiver, selecting said set of sub-carriers on which said user data is to be transmitted as a function of said indication and of said quality levels. The UE selects a set of 'M' preferred sub-bands of a certain size 'k' with high CQI, in accordance with the reporting mode configured by the eNodeB. ¶¶36, 41 col. 5:2-10

Identified Points of Contention

  • Scope Questions: A central issue may be whether the LTE standard's mechanism for configuring a "CSI reporting mode" and triggering it with a "CSI request bit" falls within the scope of the patent's term "indication related to a threshold." The patent's examples describe a simple numerical threshold (a count or a quality value), whereas the accused functionality involves a more complex, multi-modal reporting framework.
  • Technical Questions: Claim 1 requires that the receiver performs the final step of "selecting said set of sub-carriers on which said user data is to be transmitted." The complaint alleges the UE (receiver) selects a set of preferred sub-bands for the purpose of reporting them back to the eNodeB. In the LTE standard, the eNodeB (transmitter) typically makes the final scheduling decision for where to transmit data. This raises the question of whether the UE's selection of preferred candidates for reporting is legally equivalent to selecting the sub-carriers for actual data transmission as required by the claim.

V. Key Claim Terms for Construction

The Term: "indication related to a threshold"

  • Context and Importance: This term is the inventive core of the patent. The viability of the infringement case depends on construing this term broadly enough to encompass the accused LTE signaling mechanisms (i.e., the CSI request bit and reporting mode configuration). Practitioners may focus on this term because the defendant will likely argue for a narrow construction limited to the patent's specific examples.
  • Intrinsic Evidence for a Broader Interpretation: The patent states that "Only an indication related to a threshold is sent on the feed forward carrier" (’534 Patent, col. 3:8-9), and the subsequent descriptions of a number count or a quality value are presented as alternative examples, which may suggest the term is not limited to those specific forms.
  • Intrinsic Evidence for a Narrower Interpretation: The detailed embodiments exclusively describe the threshold as either "a number of sub carrier to select" or a "quality threshold" (’534 Patent, col. 3:11-17; col. 4:56-col. 5:26). A court could find these examples define the outer bounds of the term, excluding the more complex CSI mode configuration alleged to infringe.

The Term: "selecting said set of sub-carriers on which said user data is to be transmitted"

  • Context and Importance: This phrase defines the crucial action performed by the receiver. The dispute will likely turn on whether the UE's selection of preferred sub-bands to report to the base station constitutes the operative "selection" for data transmission, or if that selection is truly made later by the base station.
  • Intrinsic Evidence for a Broader Interpretation: The claim language does not explicitly state that the receiver's selection must be final and binding. A plaintiff could argue that by identifying the only set of high-quality channels, the receiver is performing the essential act of "selecting" them for potential use.
  • Intrinsic Evidence for a Narrower Interpretation: The patent describes the receiver's action as "determining at the mobile terminal the sub-carriers to be listened to" (’534 Patent, col. 5:2-5), which suggests a direct link between the selection and data reception. A defendant may argue that because the eNodeB makes the ultimate scheduling choice, the true "selection" for transmission occurs at the transmitter, which would not align with the claim's requirement that this step occurs "at said receiver."

VI. Other Allegations

Indirect Infringement

The complaint alleges that ZTE induces infringement by providing product descriptions, manuals, and other instructions that guide end users and network operators to configure and use the accused products in an infringing manner (Compl. ¶48). It also alleges contributory infringement, stating the products are "especially made or adapted for infringing" and lack substantial non-infringing uses (Compl. ¶49).

Willful Infringement

Willfulness is alleged based on ZTE having notice of the ’534 Patent "since at least the date of service of this Complaint" (Compl. ¶47). The claim is therefore based on alleged post-suit knowledge, with no facts alleged to support pre-suit knowledge.

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

Given the complaint and the patent, the litigation, if it had proceeded, would likely have focused on several key questions. However, the subsequent cancellation of all patent claims in an IPR proceeding supersedes these issues.

  • 1. Claim Validity (Dispositive Issue): The foremost question is the validity of the asserted patent. The cancellation of all claims of the ’534 Patent in IPR2021-00699 renders the patent unenforceable and the infringement allegations moot.

  • 2. Definitional Scope: A central issue would have been one of claim construction: can the LTE standard's complex, multi-modal Channel State Information (CSI) reporting framework be properly construed as the patent’s more simply described "indication related to a threshold"?

  • 3. Locus of Selection: A key factual question would have been one of operational control: does the accused system's user equipment (receiver), which selects preferred sub-bands for reporting, perform the claimed step of "selecting said set of sub-carriers on which said user data is to be transmitted," or does that legally operative selection occur at the base station (transmitter)?