Swirlate IP LLC v. ResMed Inc

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Swirlate IP LLC (Texas)
  • Defendant: ResMed, Inc. (Delaware)
  • Plaintiff’s Counsel: Chong Law Firm
• Case Identification: 1:20-cv-00556, D. Del., 04/23/2020
• Venue Allegations: Venue is alleged to be proper in the District of Delaware because the Defendant is a Delaware corporation.
• Core Dispute: Plaintiff alleges that Defendant’s Lumis series of medical devices, which incorporate wireless data transmission capabilities, infringe patents related to improving data reliability in wireless systems using Automatic Repeat reQuest (ARQ) techniques.
• Technical Context: The patents address methods for improving the reliability of data sent over noisy wireless channels using high-order modulation by systematically altering the mapping of data bits to transmission symbols between an initial transmission and subsequent re-transmissions.
• Key Procedural History: The '622' Patent is a continuation of the application that led to the '961' Patent, and both patents share an identical specification. The complaint references the '622 Patent's prosecution history, where the applicant distinguished the invention from prior art by highlighting its ability to reduce overall data traffic by only requiring retransmission when an error occurs, as opposed to schemes that always transmit redundant data over parallel paths.

Case Timeline

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

U.S. Patent No. 7,154,961 - "Constellation Rearrangement for ARQ Transmit Diversity Schemes," issued December 26, 2006

The Invention Explained

• Problem Addressed: In wireless communication systems that use higher-order modulation (where more than two bits are mapped to a single transmission symbol, e.g., 16-QAM), the individual bits within that symbol inherently have different levels of transmission reliability. Conventional systems often fail to account for these variations, which can lead to "degraded decoder performance" when signals are combined at the receiver, particularly over unreliable channels ('961 Patent, col. 2:5-11).
• The Patented Solution: The invention proposes to "improve the performance at the receiver by applying different signal constellation mappings" for transmissions sent over different diversity branches or for retransmissions requested due to an error ('961 Patent, col. 2:18-23). By using a different bit-to-symbol mapping for the retransmitted data, the system averages the reliability levels across all bits over the course of multiple transmissions. This prevents any single bit from being consistently less reliable, thereby improving the overall probability of correctly decoding the data.
• Technical Importance: This method provides a way to enhance data throughput and reliability in advanced wireless networks that depend on both high-order modulation and error-correction schemes like Hybrid ARQ (HARQ) to function efficiently.

Key Claims at a Glance

• The complaint asserts at least independent claim 1 (Compl. ¶16).
• Essential elements of claim 1 include:
  • An ARQ re-transmission method involving a first transmission and at least a second transmission based on a repeat request.
  • Modulating data packets with a "first modulation scheme" to get "first data symbols".
  • Transmitting the "first data symbols" over a "first diversity branch".
  • Modulating the data packets with a "second modulation scheme" to get "second data symbols".
  • Transmitting the "second data symbols" over a "second diversity branch".
  • Demodulating the received symbols at the receiver.
  • Diversity combining the demodulated data from the first and second branches.
  • Wherein the modulation schemes are 16-QAM and a number of log₂(M) modulation schemes are used.
• The complaint does not explicitly reserve the right to assert dependent claims.

U.S. Patent No. 7,567,622 - "Constellation Rearrangement for ARQ Transmit Diversity Schemes," issued July 28, 2009

The Invention Explained

• Problem Addressed: As the '622 Patent shares its specification with the '961 Patent, it addresses the same technical problem: the unequal bit reliabilities in higher-order modulation schemes that can degrade decoder performance in conventional wireless systems ('622 Patent, col. 2:3-11; Compl. ¶28).
• The Patented Solution: The solution is also consistent with the '961 Patent, involving the use of different bit-to-symbol mappings for initial transmissions and subsequent re-transmissions to average out bit reliabilities and improve performance ('622 Patent, col. 2:15-23). The claims of the '622 Patent, however, frame the method with different specific limitations.
• Technical Importance: As with the '961 Patent, this technology is significant for its role in improving the robustness of high-speed wireless data communication.

Key Claims at a Glance

• The complaint asserts at least independent claim 1 (Compl. ¶31).
• Essential elements of claim 1 include:
  • An ARQ re-transmission method using a higher-order modulation scheme where more than two bits are mapped to one symbol.
  • Modulating data packets using a "first mapping" to get "first data symbols".
  • Transmitting the "first data symbols" over a "first diversity branch".
  • Receiving a "repeat request" at the transmitter if the first transmission was not successfully decoded.
  • In response to the request, modulating the data packets using a "second mapping" to get "second data symbols".
  • In response to the request, transmitting the "second data symbols" over a "second diversity branch".
  • Demodulating and diversity combining the data at the receiver.
  • Wherein the "first and second mapping" schemes are "pre-stored in a memory table".
• The complaint does not explicitly reserve the right to assert dependent claims.

III. The Accused Instrumentality

Product Identification

The "ResMed Lumis Service products," which the complaint identifies as the "Accused Instrumentality" (Compl. ¶16, 31). The complaint provides a URL to a user guide for a "Lumis" series device.

Functionality and Market Context

The complaint alleges the Accused Instrumentality is a medical device that "uses an ARQ retransmission method in a wireless communication system" to transmit data, operating within an LTE network (Compl. ¶17, 32). The allegedly infringing functionality involves using HARQ, where a repeat request (e.g., a Negative Acknowledgement or NAK) triggers a re-transmission of data (Compl. ¶17, 35). The complaint claims the device uses higher-order modulation schemes like 16-QAM and 64-QAM and that it employs a different Modulation Coding Scheme (MCS) for a re-transmission than was used for the initial transmission (Compl. ¶18, 20, 36). The complaint qualifies many of its allegations by stating the functionality occurs "at least in its internal testing and usage" (e.g., Compl. ¶17, 32). No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

'961 Patent Infringement Allegations

• Identified Points of Contention:
  • Technical Question: Claim 1 requires transmission over a "first diversity branch" and a "second diversity branch". The complaint alleges multi-antenna processing for both. This raises the evidentiary question of whether the initial HARQ transmission and the re-transmission actually utilize separate diversity branches (e.g., different antennas, frequencies, or time slots configured for diversity) as defined in the patent, or if the re-transmission simply occurs over the same channel at a later time.
  • Evidentiary Question: The complaint consistently qualifies its allegations by stating the accused functionality occurs "at least in its internal testing and usage" (Compl. ¶17, 18, 19, etc.). This raises a question about what evidence Plaintiff has of infringing activity in commercially available products operating in real-world networks versus in a controlled test environment.

'622 Patent Infringement Allegations

• Identified Points of Contention:
  • Scope Question: Does the accused device's alleged use of standard adaptive modulation as part of the LTE protocol constitute infringement of the claimed method? A central issue may be whether the change in MCS for re-transmission is an implementation of the patent's specific teaching of constellation rearrangement for reliability averaging, or if it is simply a standard feature of LTE's HARQ process that operates for different technical reasons.
  • Technical Question: Claim 1 requires the mappings to be "pre-stored in a memory table". The complaint's allegation that this is "such as those schemes used by a MAC scheduler" (Compl. ¶40) suggests this may be an inference based on general LTE architecture. A point of contention will be whether the accused device actually retrieves distinct, pre-stored mappings from a memory table as claimed, or if the modulation schemes are implemented in another way (e.g., hard-coded in logic or generated algorithmically).

V. Key Claim Terms for Construction

For the '961 Patent

• The Term: "diversity branch"
• Context and Importance: This term is critical because Claim 1 of the '961 Patent requires the first and second transmissions to occur over a "first diversity branch" and a "second diversity branch," respectively. The interpretation of what constitutes two distinct branches will be central to the infringement analysis, especially in the context of a HARQ re-transmission.
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The specification states that time diversity involves mapping a signal onto "different interleaving sequences," which could be interpreted broadly to include any transmission at a different point in time, such as a HARQ re-transmission ('961 Patent, col. 1:39-40).
  • Evidence for a Narrower Interpretation: The specification provides a list of distinct diversity types, including site, antenna, polarization, frequency, and code diversity, suggesting that a "diversity branch" is a specifically configured, distinguishable communication path, not merely a later re-transmission over the same physical channel ('961 Patent, col. 1:25-42).

For the '622 Patent

• The Term: "pre-stored in a memory table"
• Context and Importance: This limitation in Claim 1 of the '622 Patent is highly specific and appears outcome-determinative. Whether the accused device's architecture meets this limitation will be a primary focus. Practitioners may focus on this term because it appears to have been added to distinguish the invention from systems that might generate modulation schemes dynamically.
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The term could be construed to cover any form of non-volatile memory or firmware where the parameters for generating standard modulation schemes like 16-QAM and 64-QAM are stored before use.
  • Evidence for a Narrower Interpretation: The specification explicitly shows a "table 15" that "stores a plurality of signal constellation patterns #0 . . . #n" that are selected for use ('622 Patent, Fig. 5; col. 8:25-28). This suggests a specific lookup table (LUT) architecture, supporting a narrower construction that requires the system to select from a set of fully-formed, pre-stored mapping patterns.

VI. Other Allegations

The complaint does not contain allegations of indirect or willful infringement.

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

1. Evidentiary Sufficiency: A foundational issue will be evidentiary. Can the Plaintiff substantiate its "information and belief" allegations—particularly the repeated qualification that the accused functionality occurs "at least in its internal testing and usage"—with evidence of infringement in commercially sold products?
2. Definitional Scope: The case will likely involve key claim construction disputes. For the '961 Patent, can a standard HARQ re-transmission, which is separated in time, satisfy the "second diversity branch" limitation, or is a more distinct, spatially or spectrally separate channel required? For the '622 Patent, is the use of standard LTE modulation schemes stored in firmware sufficient to meet the "pre-stored in a memory table" limitation?
3. Inventive Concept vs. Standard Practice: A central question will be whether the accused system's use of adaptive modulation within the LTE standard is merely an implementation of a common industry practice, or if it specifically performs the inventive concept taught by the patents—namely, using different constellation mappings for the explicit purpose of averaging bit reliabilities across transmissions.