MDSP Tech LLC v. Apple Inc

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: MDSP Technologies LLC (Delaware)
  • Defendant: Apple Inc. (California)
  • Plaintiff’s Counsel: Warren Rhoades LLP
• Case Identification: 6:23-cv-00254, W.D. Tex., 04/06/2023
• Venue Allegations: Venue is alleged based on Defendant’s regular and established places of business within the Western District of Texas, specifically an office in Austin.
• Core Dispute: Plaintiff alleges that Defendant’s Doppler-aided navigation systems, such as those found in the Apple Watch, infringe two patents related to determining a device's position in GPS-denied environments by using ambient radio signals and on-board inertial sensors.
• Technical Context: The technology addresses the challenge of providing accurate and autonomous device positioning indoors or in other areas where satellite-based navigation is unavailable, a key capability for modern location-based services.
• Key Procedural History: A significant post-filing event impacts this case. U.S. Patent No. 9,239,376, one of the two patents-in-suit, was the subject of an ex parte re-examination. On September 19, 2024, the USPTO issued a certificate cancelling claims 1-3, 5, 8, and 9. As the complaint explicitly asserts only claim 1 of this patent, the viability of the first count of infringement is now a central question.

Case Timeline

Date	Event
2010-10-08	Priority Date for ’376 and ’806 Patents
2016-01-19	U.S. Patent No. 9,239,376 Issued
2019-08-06	U.S. Patent No. 10,371,806 Issued
2023-04-06	Complaint Filed
2024-09-19	Re-examination Certificate Cancelling Asserted Claim 1 of '376 Patent Issued

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

U.S. Patent No. 9,239,376 - "Doppler aided inertial navigation," issued Jan. 19, 2016

The Invention Explained

• Problem Addressed: The patent addresses the difficulty of providing reliable and autonomous navigation for mobile devices like smartphones in environments where GPS/GNSS signals are obstructed, such as indoors, without relying on purpose-built infrastructure (’376 Patent, col. 2:53-62).
• The Patented Solution: The invention proposes a system that determines a mobile device's speed by intercepting pre-existing radio frequency (RF) signals (i.e., "signals of opportunity") and analyzing the resulting "Doppler broadening" effect. In a multipath environment (like a building), reflections cause the signal's spectral line to widen. The patent teaches that the width of this broadening is proportional to the device's speed. The system uses a "non-linear operation" as part of a spectral compression technique to extract this information and calculate speed (’376 Patent, Abstract; col. 23:3-33).
• Technical Importance: This method provides a way to derive a critical navigation parameter (speed) using only ambient signals and on-device processing, representing a potential pathway for cost-effective indoor positioning on mass-market consumer devices (’376 Patent, col. 2:53-62).

Key Claims at a Glance

• The complaint asserts independent claim 1 and reserves the right to assert other claims (Compl. ¶¶19, 24).
• The essential elements of independent claim 1 include:
  • A receiver configured to intercept an RF emission that has traveled along multiple reflected paths.
  • A narrowband signal detector that uses a spectral compression technique including a non-linear operation to create Doppler frequency observables.
  • A signal processor that employs "Doppler broadening detection" on those observables to determine the device's speed.

U.S. Patent No. 10,371,806 - "Doppler aided inertial navigation," issued Aug. 6, 2019

The Invention Explained

• Problem Addressed: The patent recognizes that while inertial sensors (accelerometers) provide high-resolution motion data, they suffer from inherent drift that quickly leads to large positioning errors when their data is integrated over time. Correcting this drift is a primary challenge in inertial navigation (’806 Patent, col. 6:40-48).
• The Patented Solution: The invention claims a mobile device that fuses data from two distinct sources. It uses a receiver and a "spectral compression positioning sensor" to derive speed from the Doppler shift of external RF signals. Concurrently, it uses a plurality of on-board linear accelerometers to produce acceleration data. Both sets of data are fed into a "physical state estimator" (such as a Kalman filter), which uses the speed derived from the RF signals to correct the inertial drift error from the accelerometers, producing a more accurate and stable position estimate (’806 Patent, Abstract; col. 10:43-48, Fig. 1A).
• Technical Importance: This approach creates a symbiotic system where the stable, long-term accuracy of Doppler-based speed measurements is used to continuously calibrate the short-term, high-resolution but drift-prone data from inertial sensors, enabling robust navigation where neither sensor type would suffice alone (’806 Patent, col. 10:9-24).

Key Claims at a Glance

• The complaint asserts independent claim 1 and reserves the right to assert other claims (Compl. ¶¶26, 31).
• The essential elements of independent claim 1 include:
  • A receiver for creating Doppler frequency observables from external RF emissions.
  • A plurality of inertial sensors with linear accelerometers creating acceleration observables.
  • A "spectral compression positioning sensor" using a non-linear operation.
  • A "physical state estimator" that processes both the Doppler and acceleration observables to determine a physical state, converts the Doppler observables to speed, and "corrects inertial drift error... based on the speed."

III. The Accused Instrumentality

Product Identification

The complaint identifies the accused products as "Apple's Doppler aided navigation systems" (Compl. ¶17).

Functionality and Market Context

The complaint alleges that these systems are used in Apple products but provides minimal technical detail regarding their specific implementation or operation. It cites a third-party online article from 2017 about the Apple Watch providing "radionavigation information" for swimmers as an example (Compl. ¶17). The complaint makes no specific allegations regarding the commercial importance or market positioning of this functionality.

IV. Analysis of Infringement Allegations

No probative visual evidence provided in complaint.

The complaint does not provide a narrative infringement theory for either patent-in-suit. Instead, it references claim chart exhibits (Exhibits C and D) that were not included with the publicly filed document (Compl. ¶¶24, 31). Consequently, a detailed claim-by-claim analysis of the infringement allegations is not possible based on the provided complaint.

Identified Points of Contention

• ’376 Patent: A dispositive threshold issue is whether Count I is moot, given the post-filing cancellation of the asserted Claim 1 by the USPTO during re-examination. Should the claim survive, a central technical question would be whether Apple’s system performs "Doppler broadening detection"—a specific measurement of the signal's spectral width in a multipath environment—as required by the claim.
• ’806 Patent: The infringement analysis for the ’806 Patent will likely focus on several technical questions. First, does the accused system contain a "spectral compression positioning sensor" that performs a "non-linear operation" as recited in the claim? Second, does the system architecture map to the claim's structure, specifically whether a "physical state estimator" uses the speed derived from Doppler observables to explicitly "correct" the "inertial drift error," suggesting a particular corrective feedback loop.

V. Key Claim Terms for Construction

’376 Patent, Claim 1: "Doppler broadening detection"

• Context and Importance: This term is the central inventive concept of the asserted claim. The dispute will likely focus on whether this requires a specific method of measuring the width of a Doppler-shifted signal peak caused by multipath reflections, as opposed to simply measuring the frequency shift of that peak.
• Intrinsic Evidence for a Broader Interpretation: The patent describes the goal as determining speed from the "power distribution of the recovered carrier signal" (’376 Patent, col. 21:38-41), which could be argued to encompass various analysis techniques.
• Intrinsic Evidence for a Narrower Interpretation: The specification provides a specific formula for calculating velocity based on the measured width of the broadened signal ("V = (c / 4f_carrier) * Δf_width"), suggesting that "detection" entails this specific quantitative analysis (’376 Patent, col. 23:34-40).

’806 Patent, Claim 1: "spectral compression positioning sensor"

• Context and Importance: This term defines a specific hardware or software module. Practitioners may focus on this term because infringement will depend on whether Apple's system can be shown to have a corresponding component that performs the claimed "spectral compression" using a "non-linear operation."
• Intrinsic Evidence for a Broader Interpretation: The specification defines spectral compression positioning (SCP) broadly as a method using "one or more nonlinear operators" to extract physical characteristics from a signal (’806 Patent, col. 8:56-68).
• Intrinsic Evidence for a Narrower Interpretation: The detailed description and figures show specific non-linear operations like "delay and multiply" blocks within a "SCP Signal Processor" (e.g., ’806 Patent, Fig. 3, col. 7:36-44), which could be used to argue the term is limited to the disclosed structures and their equivalents.

’806 Patent, Claim 1: "corrects inertial drift error ... based on the speed"

• Context and Importance: This limitation requires a specific causal relationship between the two data types. The infringement question will be whether the Doppler-derived speed is used as a direct input to calibrate and correct errors originating from the inertial sensors, as opposed to a more general fusion where both data sets contribute to a final position estimate without a direct corrective link.
• Intrinsic Evidence for a Broader Interpretation: A party might argue that any fusion of Doppler-derived speed and inertial data in an estimator (like a Kalman filter) inherently "corrects" the inertial data by producing a more accurate output.
• Intrinsic Evidence for a Narrower Interpretation: The equations for the Kalman filter show the Doppler velocity as a distinct measurement used to update the state vector, which includes an acceleration bias term ("a_bias"), indicating a direct corrective mechanism (’806 Patent, col. 28:38-65).

VI. Other Allegations

Willful Infringement

The complaint alleges willful infringement by stating that Defendant made "no attempt to design around" the patents-in-suit and "did not have a reasonable basis for believing that the claims...were invalid" (Compl. ¶¶ 20-21, 27-28). The prayer for relief requests a judgment that the case is exceptional, which provides a basis for seeking enhanced damages and attorneys' fees (Compl. ¶C, p. 7).

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

• A central threshold issue is one of case viability: is the infringement count on the ’376 patent moot given that its only asserted claim was cancelled by the USPTO in a post-filing re-examination?
• A key technical question for the remaining ’806 patent will be one of architectural equivalence: does the accused Apple system embody the specific architecture of the claims, particularly a "spectral compression positioning sensor" and a state estimator where Doppler-derived speed is explicitly used to correct for inertial sensor drift, or does it use a different method of data fusion?
• A primary evidentiary challenge for the Plaintiff will be one of proof: stemming from the complaint's lack of technical detail, the case will depend on what evidence can be discovered to demonstrate the precise internal operations of Apple’s proprietary navigation systems and map them to the specific functional components and corrective data flows required by the claims of the ’806 patent.