DCT
2:21-cv-00316
Finesse Wireless LLC v. AT&T Mobility LLC
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Finesse Wireless LLC (Utah)
- Defendant: AT&T Mobility LLC (Delaware)
- Plaintiff’s Counsel: Susman Godfrey LLP
- Case Identification: 2:21-cv-00316, E.D. Tex., 08/23/2021
- Venue Allegations: Plaintiff alleges venue is proper in the Eastern District of Texas because Defendant AT&T maintains a "regular and established" physical presence in the district, including retail stores, cellular base stations, and a research facility known as the AT&T Foundry. The complaint also notes that in prior litigation, AT&T has admitted that venue is proper in the district.
- Core Dispute: Plaintiff alleges that Defendant’s 4G/LTE and 5G mobile network base stations infringe two patents related to methods for digitally cancelling passive intermodulation interference in wireless communication systems.
- Technical Context: The technology addresses passive intermodulation (PIM), a form of signal interference that arises from non-linearities in wireless system components and degrades network performance, a particularly significant challenge in the congested radio frequency spectrum used by modern 4G and 5G networks.
- Key Procedural History: The complaint references two prior, separate patent infringement cases in the same district where AT&T allegedly admitted or did not contest that the Eastern District of Texas was a proper venue for such actions.
Case Timeline
| Date | Event |
|---|---|
| 2001-05-15 | Earliest Priority Date for '134 & '775 Patents |
| 2008-03-18 | U.S. Patent No. 7,346,134 Issued |
| 2017-01-17 | U.S. Patent No. 9,548,775 Issued |
| 2021-08-23 | Complaint Filed |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 7,346,134 - "Radio Receiver," issued March 18, 2008 (’134 Patent)
The Invention Explained
- Problem Addressed: The patent addresses the problem of unwanted signals, or interference, in wireless communications, which can degrade or prevent reception of the intended information signal. Conventional filtering techniques are described as often being insufficient to eliminate this interference, particularly when it falls within the same frequency band as the desired signal. (’134 Patent, col. 1:55-67).
- The Patented Solution: The invention proposes a method for actively cancelling interference rather than merely filtering it. The system over-samples a wide passband of received signals to create a digital bitstream. Using digital filters, it isolates both the desired "signal of interest" and the "source signals" that generate the interference. The system then computes an estimate of the interference and subtracts an inverted version of this estimate from the signal of interest path, thereby cancelling the unwanted interference without degrading the desired signal. (’134 Patent, Abstract; col. 2:4-18; col. 9:40-52).
- Technical Importance: This digital cancellation approach enables the mitigation of performance-degrading interference on an ongoing basis without requiring manual, on-site technician intervention, a significant advantage as wireless systems become more complex and the radio spectrum more congested (Compl. ¶¶22, 24).
Key Claims at a Glance
- The complaint asserts one or more claims, including at least independent claim 1 (Compl. ¶30).
- The essential elements of independent claim 1 include:
- over-sampling, at a desired frequency, a passband of received signals to create a bit stream, wherein the received signals include signals of interest and interference generating signals;
- isolating signals of interest in the bit stream using one or more decimating filters;
- isolating source signals that generate one or more intermodulation products inband of the signal of interest using one or more decimating filters;
- computing an estimate of each of the one or more intermodulation products from the source signals;
- cancelling out one or more inband intermodulation products using the estimate of the intermodulation products; and
- performing phase and amplitude adjustment on estimations of the intermodulation product interfering signals in a closed loop manner, which comprises performing sub-sample phase shifts.
U.S. Patent No. 9,548,775 - "Mitigation of transmitter passive and active IMPs in real and continuous time in the transmitter and co-located receiver," issued January 17, 2017 (’775 Patent)
The Invention Explained
- Problem Addressed: This patent, a continuation of the family including the ’134 Patent, focuses specifically on mitigating intermodulation products (IMPs) in a system where a transmitter and receiver are co-located, such as a cellular base station. In such systems, the powerful signals from the transmitter can create interference in the co-located, sensitive receiver. (’775 Patent, Abstract; col. 1:19-24).
- The Patented Solution: The invention describes a method for generating Intermodulation Product Cancellation Signals (ICSs) in real-time to cancel both passive and active IMPs. The method uses copies of the transmitter's own signals and generates the ICS based on a "power series description of a non-linear process," which models how the IMPs are created. This involves digitally multiplying and filtering specific combinations of the source signals to create a precise cancellation signal that is then used to remove the IMPs from the receiver path. (’775 Patent, Abstract; Claim 1).
- Technical Importance: The technology provides a digital, real-time method to counteract self-interference in full-duplex communication systems, which can allow transmitters to operate at higher power and closer to saturation, thereby improving network efficiency and capacity (Compl. ¶47).
Key Claims at a Glance
- The complaint asserts one or more claims, including at least independent claim 1 (Compl. ¶49).
- The essential elements of independent claim 1 include:
- generating intermodulation product (IMP) cancellation signals (ICSs) to cancel passive IMPs in a receiver, continuously and near real time, using copies of transmitter signals;
- wherein the passive IMPs are generated in passive components of the transmitter and receiver after a high powered amplifier (HPA) and transmitter filter;
- wherein generating the ICSs is based on a power series description of a non-linear process for generating the IMPs; and
- includes generating an n-th order ICS by, given three signals S1, S2, and S3, digitally multiplying and filtering a specific set of signal product combinations.
III. The Accused Instrumentality
Product Identification
- The complaint identifies AT&T’s 4G/LTE and 5G mobile network, and specifically the "AT&T Base Stations" that constitute the infrastructure of that network, as the accused instrumentalities (Compl. ¶¶13, 30, 49).
Functionality and Market Context
- The AT&T Base Stations are alleged to provide telecommunication and internet services to customers by communicating with mobile devices over the 4G/LTE and 5G networks (Compl. ¶¶13-14). The complaint alleges these base stations incorporate technology that employs signal cancellation to mitigate passive intermodulation (PIM) interference (Compl. ¶13). As visual evidence of the network's operation within the judicial district, the complaint provides a coverage map from AT&T's website. This screenshot, labeled Figure 1, depicts the areas of East Texas with 4G/LTE and 5G service (Compl. ¶16, Fig. 1). The complaint asserts the network is a result of "billions of dollars" of investment and covers over 99% of the U.S. population (Compl. ¶15).
IV. Analysis of Infringement Allegations
’134 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| over-sampling, at a desired frequency, a passband of received signals to create a bit stream, wherein the received signals include signals of interest and interference generating signals, the interference generating signals capable of generating intermodulation products inband of the signals of interest | AT&T Base Stations allegedly use analog-to-digital converters (ADCs) that oversample incoming signals, producing a bit stream as output (Compl. ¶32). | ¶32 | col. 2:5-9 |
| isolating signals of interest in the bit stream using one or more decimating filters | The base stations allegedly use decimating filters to reduce the sampling rate and process the mobile traffic, which are the signals of interest (Compl. ¶33). | ¶33 | col. 2:10-12 |
| isolating source signals that generate one or more intermodulation products inband of the signal of interest using one or more decimating filters | The PIM mitigation system allegedly identifies and isolates IMPs from the uplink signal that are caused by downlink signals, which function as the source signals (Compl. ¶34). | ¶34 | col. 2:12-15 |
| computing an estimate of each of the one or more intermodulation products from the source signals that generate the one or more intermodulation products | The accused instrumentalities allegedly adaptively calculate a transfer function of the PIM signal to create an "image of the inband interferer" (Compl. ¶35). | ¶35 | col. 2:15-17 |
| cancelling out one or more inband intermodulation products using the estimate of the intermodulation products | The base stations are alleged to perform "cancelling" by creating a copy of the interferer and subtracting it from the received signal (Compl. ¶36). | ¶36 | col. 2:17-18 |
| performing phase and amplitude adjustment on estimations of the intermodulation product interfering signals in a closed loop manner... comprises performing sub-sample phase shifts to make a phase adjustment on the estimations of the intermodulation product interfering signals | The technology is described as a "closed-loop system" where cancellation is automatically carried out, performing phase and amplitude adjustments to adapt to PIM sources (Compl. ¶37). | ¶37 | col. 9:18-24 |
’775 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| generating intermodulation product (IMP) cancellation signals (ICSs) to cancel passive IMPs in the receiver, continuously and near real time, using copies of transmitter signals of the transmitter | AT&T Base Stations allegedly recognize the source transmission signal, make a copy of it, and then generate a PIM signal function to remove PIM from the received signal (Compl. ¶52). | ¶52 | col. 3:20-22 |
| wherein the passive IMPs are generated in passive transmitter components of the transmitter and receiver components of the receiver after a high powered amplifier (HPA) and transmitter filter of the transmitter, wherein the transmitter filter is coupled between the HPA and an antenna used by the transmitter | The base stations allegedly implement PIM cancellation in the digital domain based on the known baseband signal, which is generated after passing through components like the HPA and transmitter filter (Compl. ¶53). | ¶53-54 | col. 4:26-32 |
| wherein generating the ICSs is based on a power series description of a non-linear process for generating the IMPs | The base stations are alleged to calculate intermodulation intercept points, a measure of non-linearity that is derived from a power series model of device behavior (Compl. ¶55). | ¶55 | col. 4:33-36 |
| and includes generating an n-th order ICS by, given three signals S1, S2 and S3, digitally multiplying and filtering S1×S1×S2 and S1×S2×S2 and S1×S2×S3 and S1×S1×S3 and S2×S2×S3 and S1×S3×S3 and S2×S3×S3, where n is an integer | The accused instrumentalities allegedly achieve n-th order ICS generation by "digitally multiplying and filtering three signals (e.g., S1, S2, and S3) accordingly" to generate the claimed combinations (Compl. ¶55). | ¶55 | col. 4:38-42 |
- Identified Points of Contention:
- Evidentiary Questions: The complaint's infringement allegations rely heavily on citations to general industry documents, such as technical papers from 3GPP, Ericsson, and Nokia, and a job posting, to describe the functionality of AT&T's base stations (Compl. ¶¶ 32-37, 52-55). A central point of contention may be whether discovery confirms that AT&T's specific, multi-vendor base station equipment actually implements the precise methods claimed in the patents, as opposed to other PIM mitigation techniques.
- Technical Scope Questions: The patents draw a clear distinction between "cancelling" and "filtering." A potential dispute is whether the accused systems perform "cancelling" as claimed—by generating an inverted copy of the interference for subtraction—or if they employ a different form of sophisticated digital signal processing, such as adaptive equalization, that may fall outside the scope of the claims. For the ’775 patent, a question is whether calculating "intermodulation intercept points" is sufficient to meet the "based on a power series description" limitation, or if a more direct implementation of that mathematical model is required by the claim.
V. Key Claim Terms for Construction
The Term: "cancelling" ('134 Patent, Claim 1)
- Context and Importance: The complaint and the patent specification both emphasize this term, framing the invention as a "cancelling" technology rather than a "filtering" one (Compl. ¶24; ’134 Patent, col. 8:12-18). The infringement case for the ’134 Patent may depend on whether the accused functionality meets the specific meaning of this term.
- Intrinsic Evidence for a Broader Interpretation: The patent summary describes the invention as "cancel-ing out one or more inband intermodulation products using the estimate of the intermodulation products" (’134 Patent, col. 2:17-18). This could be argued to encompass any active process that uses an estimate of interference to remove it.
- Intrinsic Evidence for a Narrower Interpretation: A specific embodiment describes the process where an "estimate of the interfering signal is inverted to produce a cancellation signal" which is then added to the desired signal via an adder to "cancel interference" (’134 Patent, col. 9:40-45). This suggests a more specific "invert-and-add" (i.e., subtractive) mechanism is required.
The Term: "based on a power series description of a non-linear process" ('775 Patent, Claim 1)
- Context and Importance: This term defines the theoretical foundation for how the cancellation signal is generated. Plaintiff's infringement theory connects this claim language to the allegation that AT&T's base stations calculate "intermodulation intercept points" (Compl. ¶55), which are metrics derived from power series models of non-linearity. Practitioners may focus on this term because its construction will determine whether such indirect evidence is sufficient to prove infringement.
- Intrinsic Evidence for a Broader Interpretation: The Abstract broadly states the method generates cancellation signals "using a process based on a power series description of a non-linear process" (’775 Patent, Abstract). This language may support an interpretation that covers any method that relies on the principles of non-linear power series, even if not explicitly implemented as a series expansion.
- Intrinsic Evidence for a Narrower Interpretation: The patent itself does not appear to provide a specific, limiting definition of this term. A defendant, however, could argue that the term requires an explicit implementation of a Taylor series or similar mathematical formula to generate the cancellation signal, rather than merely using derivative metrics like intercept points which are common in RF engineering for characterizing, but not necessarily correcting, non-linearity.
VI. Other Allegations
- Indirect Infringement: The complaint alleges that AT&T induces infringement by encouraging end users to use its 4G/LTE and 5G network through advertising, selling compatible devices, and providing user manuals, knowing that use of the network will require the claimed PIM cancellation (Compl. ¶¶38-41, 56-59). The core infringement allegation appears to be direct infringement by AT&T for operating the base stations, raising a question as to the specific infringing acts performed by the induced parties (e.g., end users).
- Willful Infringement: The complaint alleges that AT&T has had notice of the asserted patents "at least as of the date of this Complaint" (Compl. ¶¶43, 61). The prayer for relief seeks enhanced damages for "willful and deliberate infringement," suggesting a willfulness claim based on post-filing conduct (Compl. ¶63; Prayer for Relief, ¶b).
VII. Analyst’s Conclusion: Key Questions for the Case
- A core issue will be one of evidentiary proof: does the technical evidence obtained in discovery show that AT&T's diverse, multi-vendor base station infrastructure actually performs PIM mitigation using the specific digital cancellation steps recited in the claims, or will there be a mismatch between the general industry documents cited in the complaint and the specific operation of the accused products?
- A key legal and technical question will be one of definitional scope: can the term "cancelling," which the '134 patent contrasts with filtering, be construed to read on the accused system's functionality, or does the accused system employ a method of interference reduction, such as adaptive equalization, that is technically distinct from the patent's "invert-and-subtract" teaching?
- The dispute over the '775 patent may hinge on a question of mathematical implementation: does an accused system's calculation and use of "intermodulation intercept points" satisfy the claim requirement of generating a cancellation signal "based on a power series description," or does this limitation require a more direct and explicit use of a mathematical power series to model and counteract the interference?