DCT
4:25-cv-00426
Freedom Patents LLC v. Realtek Semiconductor Corp
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Freedom Patents LLC (Texas)
- Defendant: Realtek Semiconductor Corporation (Taiwan)
- Plaintiff’s Counsel: Antonelli, Harrington & Thompson LLP
- Case Identification: 4:25-cv-00426, E.D. Tex., 04/24/2025
- Venue Allegations: Venue is asserted on the basis that Defendant is a foreign corporation, which under 28 U.S.C. § 1391(c)(3) may be sued in any judicial district.
- Core Dispute: Plaintiff alleges that Defendant’s Wi-Fi semiconductor products that comply with the IEEE 802.11ax standard infringe three patents related to methods for selecting antennas in multiple-input, multiple-output (MIMO) wireless networks.
- Technical Context: The technology concerns methods to improve the performance and efficiency of MIMO Wi-Fi systems by dynamically selecting an optimal subset of available antennas, a foundational capability for high-speed wireless standards like Wi-Fi 6.
- Key Procedural History: The complaint notes the patents-in-suit originated from research at Mitsubishi Electric Research Laboratories (MERL). No prior litigation, licensing history, or post-grant proceedings are mentioned in the complaint.
Case Timeline
| Date | Event |
|---|---|
| 2005-09-30 | Earliest Priority Date for ’096 and ’815 Patents |
| 2005-11-21 | Earliest Priority Date for ’686 Patent |
| 2012-10-09 | U.S. Patent 8,284,686 Issues |
| 2013-02-12 | U.S. Patent 8,374,096 Issues |
| 2013-08-20 | U.S. Patent 8,514,815 Issues |
| 2021-01-01 | Approx. Date of IEEE 802.11ax-2021 Standard Publication |
| 2025-04-24 | Complaint Filed |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 8,284,686 - "Antenna/Beam Selection Training in MIMO Wireless LANS with Different Sounding Frames"
- Patent Identification: U.S. Patent No. 8,284,686, "Antenna/Beam Selection Training in MIMO Wireless LANS with Different Sounding Frames," issued October 9, 2012. (Compl. ¶15).
The Invention Explained
- Problem Addressed: The patent addresses the challenge of implementing antenna selection in MIMO wireless networks. While using multiple antennas increases system capacity, it also adds hardware cost and complexity. Selecting an optimal subset of antennas is a solution, but this requires estimating the complete channel state information (CSI), a process that can introduce undesirable overhead and delay with conventional methods. (’686 Patent, col. 1:20-52).
- The Patented Solution: The invention proposes a MAC-layer method where a station receives a series of consecutive "sounding packets," with each packet corresponding to a different subset of antennas. Crucially, at least one of these packets contains a high-throughput (HT) control field that both signals the initiation of the antenna selection process and specifies the number (N) of sounding packets that will follow for the training sequence. This allows the receiving station to efficiently buffer the required packets, estimate the full channel matrix, and select the optimal antenna subset. (’686 Patent, Abstract; col. 4:1-15).
- Technical Importance: This approach provides an efficient protocol for antenna selection training within the MAC layer, designed to be compatible with emerging high-throughput Wi-Fi standards (like 802.11n) while minimizing modifications to the physical (PHY) layer. (’686 Patent, col. 5:51-65).
Key Claims at a Glance
- The complaint asserts independent claims 1 (a method) and 21 (a station). (Compl. ¶18).
- Independent Claim 1 (Method) Elements:
- Receiving plural consecutive packets that include plural "sounding packets," each corresponding to a different antenna subset.
- At least one packet includes a "high throughput (HT) control field" with (i) a signal to initiate antenna selection and (ii) a number N indicating how many sounding packets will follow for the selection process.
- Estimating a channel matrix from the N received sounding packets.
- Selecting a subset of antennas based on the channel matrix.
- The complaint notes that Plaintiff reserves the right to assert additional claims, including dependent claims. (Compl. ¶47).
U.S. Patent No. 8,374,096 - "Method for Selecting Antennas and Beams in MIMO Wireless LANS"
- Patent Identification: U.S. Patent No. 8,374,096, "Method for Selecting Antennas and Beams in MIMO Wireless LANS," issued February 12, 2013. (Compl. ¶25).
The Invention Explained
- Problem Addressed: Similar to the ’686 Patent, this patent aims to solve the problem of performing antenna selection in MIMO WLANs efficiently and with low overhead, thereby reducing hardware cost and complexity. (’096 Patent, col. 1:24-43).
- The Patented Solution: The invention describes a MAC-layer training method where a station initiates antenna selection by sending a frame containing an HT control field. A key aspect is the repurposing of existing fields within the HT control structure; specifically, the method uses an Antenna Selection Indicator (ASI) bit or a specific value in the MRQ Sequence (MRS) field to signal that the MCS Feedback (MFB) field should be used for antenna selection control (ASBFC) instead of its normal function. This ASBFC field then contains command and data subfields to manage the training process, including indicating the number of sounding packets. (’096 Patent, Claim 1; col. 7:10-23).
- Technical Importance: This method provides a specific protocol for embedding antenna selection signaling within the existing MAC-layer control structures of high-throughput Wi-Fi standards, avoiding the need to define entirely new frames or fields. (’096 Patent, col. 5:44-53).
Key Claims at a Glance
- The complaint asserts independent claim 1 (a method). (Compl. ¶28).
- Independent Claim 1 (Method) Elements:
- Receiving multiple transmitted sounding packets at a station, each corresponding to a different antenna subset.
- Estimating a channel matrix for each subset.
- Sending a frame with an "high throughput (HT) control field" to initiate antenna selection.
- Selecting an antenna subset based on the channel matrices.
- The HT control field includes an MCS feedback (MFB) field, which is repurposed for antenna selection control (ASBFC) if an ASI field is set to "1" or an MRS field is set to "111".
- The ASBFC field includes a data subfield that indicates the number of sounding packets.
- The complaint reserves the right to assert additional claims. (Compl. ¶47).
U.S. Patent No. 8,514,815 - "Training Signals for Selecting Antennas and Beams in MIMO Wireless LANs"
- Patent Identification: U.S. Patent No. 8,514,815, "Training Signals for Selecting Antennas and Beams in MIMO Wireless LANs," issued August 20, 2013. (Compl. ¶35).
- Technology Synopsis: This patent also discloses a method for antenna selection in MIMO WLANs. The method involves a station receiving multiple, consecutively transmitted sounding packets, where each packet corresponds to a different antenna subset, and the number of packets is predetermined. (’815 Patent, Abstract; Claim 1 as corrected). The receiving station estimates a channel matrix from these packets and selects an antenna subset accordingly.
- Asserted Claims: Independent claim 1 is asserted. (Compl. ¶38, ¶47).
- Accused Features: The complaint alleges that Realtek's products implementing MIMO capabilities compliant with the IEEE 802.11ax-2021 standard infringe this patent by their normal operation. (Compl. ¶37).
III. The Accused Instrumentality
Product Identification
- The accused instrumentalities are Realtek's semiconductor products, such as Wi-Fi chips and combo modules, that are compliant with the IEEE 802.11ax-2021 standard (also known as Wi-Fi 6) and implement MIMO capabilities. (Compl. ¶¶17, 27, 37). The Realtek RTL8852BE is identified as an exemplary accused product. (Compl. ¶19).
Functionality and Market Context
- The accused products are integrated circuits that provide wireless network connectivity for a wide range of downstream electronic devices. (Compl. ¶3). The complaint presents a "Description of Equipment Under Test" table from an FCC test report for the exemplary RTL8852BE, which confirms its identity as an "11ax RTL8852BE Combo module" supporting modulations like OFDMA. (Compl. p. 6). Plaintiff alleges that Realtek markets these products based on the performance benefits of 802.11ax, such as increased speed and low latency. (Compl. ¶20).
IV. Analysis of Infringement Allegations
8,284,686 Patent Infringement Allegations
The complaint alleges infringement based on the accused products' compliance with the IEEE 802.11ax standard. The specific operational details are not enumerated beyond general allegations that the products perform the claimed steps.
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| receiving, via a channel, at a station in the WLAN plural consecutive packets including plural sounding packets, each sounding packet corresponding to a different subset of the set of antennas | The accused products are alleged to be configured to receive sounding packets for channel estimation as a standard part of their MIMO operation under the IEEE 802.11ax standard. | ¶17, ¶21 | col. 4:3-7 |
| at least one of the plural consecutive packets includes (i) a high throughput (HT) control field including a signal to initiate antenna selection and (ii) a number N indicative of a number of sounding packets which follow... | The complaint alleges that the accused products' operation under the 802.11ax standard includes using control fields in data packets to manage antenna selection training, including signaling the number of packets in a training sequence. | ¶17, ¶21 | col. 4:7-12 |
| estimating a channel matrix based on a characteristic of the channel as indicated by the received N sounding packets | The accused products' MIMO functionality allegedly includes estimating the channel matrix from received sounding packets to enable features like antenna selection, as required by the 802.11ax standard. | ¶17, ¶21 | col. 4:12-15 |
| selecting a subset of antennas according to the channel matrix | The accused products are alleged to perform antenna selection based on the estimated channel matrix as part of their standard-compliant MIMO operations. | ¶17, ¶21 | col. 4:14-15 |
8,374,096 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| sending, by the station, a frame including a high throughput (HT) control field to initiate a selecting of antennas after estimating the channel matrix for each subset of antennas... | The accused products, by allegedly complying with the IEEE 802.11ax standard, are accused of sending control frames to initiate antenna selection procedures based on channel estimates. | ¶27, ¶31 | col. 14:21-28 |
| ...in which the HT control field includes a MCS selection feedback (MFB) field, and if an ASI field is set to "1" or if an MRS field is set to "111", then the MFB field is used for antenna selection, beam selection, or as a transmitter beam forming control (ASBFC) field... | The complaint's theory suggests that control fields within the 802.11ax protocol, analogous to the MFB/ASI/MRS fields, are used to manage and signal antenna selection feedback and control. | ¶27, ¶31 | col. 14:31-38 |
| ...in which the data subfield indicates a number of the multiple sounding packets. | The 802.11ax standard allegedly specifies control structures where information, such as the number of sounding packets in a training sequence, is communicated. | ¶27, ¶31 | col. 14:40-43 |
Identified Points of Contention
- Scope Questions: A primary issue may be whether the term "high throughput (HT) control field," which is rooted in the context of the IEEE 802.11n standard prominent during the patents' prosecution, can be construed to cover the control field structures of the later IEEE 802.11ax standard, which uses "High Efficiency" (HE) terminology.
- Technical Questions: The complaint broadly asserts that compliance with the 802.11ax standard equates to infringement but does not provide specific evidence (e.g., packet captures or source code analysis) showing that the accused products actually perform the precise sequence of signaling, packet exchange, and estimation required by the claims. The provided SAR test report confirms the product's 802.11ax capability but offers no insight into the specific protocols it uses for antenna selection. (Compl. p. 6). This raises the evidentiary question of whether the accused products' operations technically map onto the patent claims.
V. Key Claim Terms for Construction
- The Term: "high throughput (HT) control field" (present in asserted claims of both the ’686 and ’096 patents)
- Context and Importance: This term is foundational to the asserted claims, which require specific signaling to occur within this field. Practitioners may focus on this term because the patents were developed in the context of the 802.11n ("High Throughput") standard, while the accused products operate under the 802.11ax ("High Efficiency") standard. The outcome of its construction could determine whether the claims read on the accused technology at all.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The specification describes the functionality of the field in general terms, such as a field that "controls the fast link adaptation training process" ('686 Patent, col. 2:21-23), potentially supporting an interpretation that covers any functionally similar control field in a subsequent wireless standard.
- Evidence for a Narrower Interpretation: The specification repeatedly refers to the "IEEE 802.11n standard" and its specific structures, and Figure 12 explicitly diagrams an "HT Control Field". (’686 Patent, col. 2:53-54; Fig. 12). This tight linkage to a specific standard could support a narrower construction limited to the 802.11n context.
VI. Other Allegations
- Indirect Infringement: The complaint alleges inducement by asserting that Realtek provides instructions and encourages customers and end-users to use the accused products in their normal, infringing manner. (Compl. ¶¶46-48). It also alleges contributory infringement, stating that the products contain special features for MIMO channel estimation and antenna selection that are not staple articles of commerce and have no substantial non-infringing use. (Compl. ¶¶65-67).
- Willful Infringement: Willfulness is alleged based on knowledge of the patents that Realtek will have acquired at least as of the filing of the complaint. (Compl. ¶¶69-70). The complaint further alleges willful blindness, claiming Realtek has a policy of not reviewing the patents of others. (Compl. ¶71).
VII. Analyst’s Conclusion: Key Questions for the Case
- A core issue will be one of definitional scope and inter-generational standards mapping: Can the term "high throughput (HT) control field", which is technically rooted in the IEEE 802.11n standard described in the patents, be construed to cover the corresponding "High Efficiency" (HE) control structures used in the accused IEEE 802.11ax products?
- A key evidentiary question will be one of technical proof: Beyond asserting compliance with the 802.11ax standard, what specific evidence will be presented to demonstrate that the accused Realtek chips actually execute the precise, multi-step signaling and packet exchange protocols recited in the asserted claims?
- The case may also turn on a question of functional divergence: Does the antenna selection protocol implemented in the 802.11ax standard operate in a manner that is functionally equivalent to the specific methods claimed—such as repurposing an MFB field as claimed in the ’096 patent—or is there a fundamental mismatch in technical operation between the patented methods and the accused implementation?