DCT
1:13-cv-00056
Brandywine Communications Tech LLC v. Precision Communiciatons Inc
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Brandywine Communications Technologies, LLC (Delaware)
- Defendant: Precision Communications, Inc., d/b/a, PCI Systems, Inc. (Colorado)
- Plaintiff’s Counsel: Sheridan Ross P.C.
- Case Identification: 1:13-cv-00056, D. Colo., 01/10/2013
- Venue Allegations: Venue is alleged to be proper in the District of Colorado because the Defendant is a Colorado corporation.
- Core Dispute: Plaintiff alleges that Defendant’s Digital Subscriber Line (DSL) business, including its services and equipment, infringes six patents related to echo cancellation, signal predistortion, and automatic modem configuration technologies.
- Technical Context: The patents address technical challenges in data communications, such as mitigating signal echo and distortion, to improve the speed and reliability of data transmission over physical lines like the copper pairs used for DSL services.
- Key Procedural History: The complaint alleges that Plaintiff sent a notice of infringement letter to the Defendant on December 10, 2012, which may serve as the basis for allegations of willful infringement for any infringing conduct after that date.
Case Timeline
| Date | Event |
|---|---|
| 1990-12-20 | Priority Date for '328 Patent |
| 1991-09-24 | Priority Date for '854 Patent |
| 1993-04-27 | Issue Date for U.S. Patent No. 5,206,854 |
| 1993-10-05 | Issue Date for U.S. Patent No. 5,251,328 |
| 1995-09-29 | Priority Date for '537 and '657 Patents |
| 1998-09-22 | Issue Date for U.S. Patent No. 5,812,537 |
| 1998-10-27 | Issue Date for U.S. Patent No. 5,828,657 |
| 1999-05-17 | Priority Date for '501 and '472 Patents |
| 2005-11-29 | Issue Date for U.S. Patent No. 6,970,501 |
| 2011-02-22 | Issue Date for U.S. Patent No. 7,894,472 |
| 2012-12-10 | Plaintiff sends notice of infringement letter to Defendant |
| 2013-01-10 | Complaint Filing Date |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 5,206,854 - "Detecting Loss of Echo Cancellation," issued April 27, 1993
The Invention Explained
- Problem Addressed: The patent describes a problem in full-duplex modems where, if the connection to the remote modem is abruptly dropped, the modem's echo canceler may fail. A conventional energy detector might then misinterpret the resulting high level of residual echo as a valid incoming signal, preventing the modem from recognizing the disconnect ('854 Patent, col. 1:36-57).
- The Patented Solution: The invention proposes a more reliable method for detecting a disconnect. Instead of merely measuring signal energy, the system correlates the echo estimate signal with the echo-canceled signal (the signal remaining after echo subtraction). A high degree of correlation indicates that the residual signal is primarily composed of the modem's own echo, signifying a loss of echo cancellation, rather than the presence of a valid remote signal ('854 Patent, Abstract; col. 4:40-52). This process is illustrated in the block diagram of Figure 3, which depicts correlators (450, 460) analyzing the signals.
- Technical Importance: This technique offered a more robust way for high-speed modems to detect line drops compared to simple energy detection, preventing a state where a modem could remain "locked on" to its own echo after the remote connection was lost ('854 Patent, col. 1:46-57).
Key Claims at a Glance
- The complaint asserts "one or more claims" of the patent (Compl. ¶16). Independent claims 1 (method), 3 (apparatus), and 5 (modem apparatus) are available for assertion.
- Independent Claim 1 requires the steps of:
- receiving a signal,
- subtracting an echo estimate signal from the received signal to provide an echo-canceled signal,
- correlating the echo estimate signal with the echo-canceled signal to provide a degree of correlation, and
- determining the absence of a remote signal by detecting the degree of correlation of the echo estimate signal with the echo-canceled signal.
U.S. Patent No. 5,251,328 - "Predistortion Technique for Communications Systems," issued October 5, 1993
The Invention Explained
- Problem Addressed: In systems like dial-up modems, the communication channel consists of multiple segments (e.g., subscriber loops at each end and a central four-wire path). Most signal distortion occurs in the subscriber loops, while most noise is introduced in the central path. A conventional equalizer that corrects for the total end-to-end distortion will invariably amplify the noise, a problem known as "noise enhancement" ('328 Patent, col. 1:20-37).
- The Patented Solution: The invention teaches a "predistortion" method to counteract this. A transceiver first determines the distortion characteristics of only the subscriber loop adjacent to the receiving transceiver by analyzing a known training sequence. The transmitting transceiver then pre-distorts its outgoing signal with the inverse of that specific distortion. This targeted compensation avoids amplifying noise introduced elsewhere in the channel ('328 Patent, Abstract; col. 4:21-44).
- Technical Importance: By minimizing noise enhancement, this technique enabled higher and more reliable data rates over communication channels, such as the public telephone network, that have distinct segments with different noise and distortion properties ('328 Patent, col. 1:38-44).
Key Claims at a Glance
- The complaint asserts "one or more claims" of the patent (Compl. ¶21). Independent claims include 1 (transceiver apparatus), 2 (method), and 3 (system apparatus).
- Independent Claim 1 requires:
- means responsive to a received signal from said communications channel for determining substantially less than all of the amplitude distortion introduced within said communications channel,
- said determining means being designed for determining substantially less than all of the amplitude distortion introduced within said communications channel, and
- means responsive to said determined amplitude distortion for predistorting a transmitted signal from said transceiver.
U.S. Patent No. 5,812,537 - "Echo Canceling Method and Apparatus for Data Over Cellular," issued September 22, 1998
- Technology Synopsis: The patent addresses incorrect echo canceler training in cellular modems caused by non-linear components in the cellular network that distort the echo signal during half-duplex training. The invention monitors an equalizer's error signal during a subsequent full-duplex phase; an error level above a threshold is presumed to be residual echo, triggering a predefined adjustment to the echo canceler's tap coefficients to improve its performance ('537 Patent, Abstract; col. 2:9-18).
- Asserted Claims: "one or more claims" (Compl. ¶26).
- Accused Features: Defendant's "DSL service, modems, and equipment" (Compl. ¶27).
U.S. Patent No. 5,828,657 - "Half-Duplex Echo Canceler Training Using a Pilot Signal," issued October 27, 1998
- Technology Synopsis: This patent also targets improper echo canceler training due to non-linear network components. The solution is for the far-end modem to transmit a "pilot tone" while the near-end modem is training its echo canceler. This tone forces the non-linear components into a linear operating range, ensuring the echo signal is not distorted. The near-end modem then filters out the pilot tone from the received signal before using it to train its echo canceler correctly ('657 Patent, Abstract; col. 2:1-12).
- Asserted Claims: "one or more claims" (Compl. ¶36).
- Accused Features: Defendant's "DSL service, modems, and equipment" (Compl. ¶37).
U.S. Patent No. 6,970,501 - "Method and Apparatus For Automatic Selection and Operation of a Subscriber Line Spectrum Class Technology," issued November 29, 2005
- Technology Synopsis: The patent describes a communication device, such as a DSL modem, that must comply with various "Spectrum Management Classes" which govern power and frequency usage to prevent interference. The invention is a modem that can automatically detect which classes are permissible for a given subscriber line (e.g., by measuring loop length), and then select an operational mode that is compliant, potentially prohibiting operation if no compliant mode is available ('501 Patent, Abstract; col. 3:20-38).
- Asserted Claims: "one or more claims" (Compl. ¶46).
- Accused Features: Defendant's "DSL service, modems, and equipment" (Compl. ¶47).
U.S. Patent No. 7,894,472 - "Method and Apparatus For Automatic Selection and Operation of a Subscriber Line Spectrum Class Technology," issued February 22, 2011
- Technology Synopsis: As a continuation of the '501 Patent, this patent covers the same technological concept. It describes an apparatus with multiple transceivers corresponding to different Spectrum Management Classes and a selector that automatically connects the appropriate transceiver to the line based on a determination of which classes are compatible with the subscriber loop's characteristics ('472 Patent, Abstract; col. 4:39-56).
- Asserted Claims: "one or more claims" (Compl. ¶54).
- Accused Features: Defendant's "DSL service, modems, and equipment" (Compl. ¶55).
III. The Accused Instrumentality
- Product Identification: The complaint broadly accuses Defendant's "Digital Subscriber Line ('DSL') business," which includes "DSL service and equipment" and "DSL service, modems, and equipment" (Compl. ¶14, ¶17, ¶22).
- Functionality and Market Context: The complaint alleges that the accused instrumentalities provide broadband data communication services over telephone lines (Compl. ¶14, ¶17). It does not provide specific technical details about the operation of the accused DSL equipment or its underlying protocols. The complaint makes no allegations regarding the Defendant's market position or the commercial success of its DSL business, other than to state that Plaintiff has suffered damages from the alleged infringement (Compl. ¶19). No probative visual evidence provided in complaint.
IV. Analysis of Infringement Allegations
The complaint does not provide a detailed mapping of claim elements to the features of the accused products. The following charts summarize the infringement theory based on the asserted claims and the general allegation that the Defendant's "DSL service and equipment" perform the claimed functions.
'854 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| receiving a signal | The accused DSL equipment receives electrical signals over a communications line. | ¶17 | col. 6:21 |
| subtracting an echo estimate signal from the received signal to provide an echo-canceled signal | The accused DSL equipment uses an echo canceler to generate and subtract an echo estimate from the received signal. | ¶17 | col. 6:22-24 |
| correlating the echo estimate signal with the echo-canceled signal to provide a degree of correlation | The accused DSL equipment performs a correlation between the echo estimate and the post-cancellation signal. | ¶17 | col. 6:25-27 |
| determining the absence of a remote signal by detecting the degree of correlation of the echo estimate signal with the... | The accused DSL equipment uses the result of the correlation to determine when a remote connection has been lost. | ¶17 | col. 6:28-31 |
- Identified Points of Contention: A central question will be factual: do the accused DSL products use a correlation-based method as claimed to detect line disconnects, or do they employ a different technique, such as the simple energy detection method described as prior art in the patent ('854 Patent, col. 1:40-54)? The complaint provides no specific evidence to show that the accused equipment performs the claimed correlation step.
'328 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| means responsive to a received signal from said communications channel for determining substantially less than all of the amplitude distortion... | The accused DSL equipment is alleged to have a mechanism that determines the distortion characteristics of only a portion of the communication channel. | ¶22 | col. 6:1-5 |
| means responsive to said determined amplitude distortion for predistorting a transmitted signal from said transceiver | Based on the determined partial distortion, the accused DSL equipment's transmitter pre-distorts its outgoing signals before transmission. | ¶22 | col. 6:6-8 |
- Identified Points of Contention: The infringement analysis may turn on whether the accused DSL equipment's signal compensation scheme performs the specific two-part process of the claims: first, isolating and "determining substantially less than all" of the channel distortion (e.g., only the subscriber loop portion), and second, using that specific determination to "predistort" the transmitted signal. This contrasts with conventional end-to-end equalization, which the patent sought to improve upon.
V. Key Claim Terms for Construction
'854 Patent
- The Term: "correlating"
- Context and Importance: This term defines the central inventive step. The case may depend on whether the defendant's method for detecting a disconnect falls within the scope of "correlating," as opposed to merely measuring signal energy. Practitioners may focus on this term because it distinguishes the invention from the prior art described in the patent's own background section.
- Intrinsic Evidence for a Broader Interpretation: The specification refers generally to determining a "degree of correlation," which could be argued to encompass any method that assesses the relationship between the echo estimate and the echo-canceled signal ('854 Patent, col. 2:13, col. 6:26-27).
- Intrinsic Evidence for a Narrower Interpretation: The specification discloses specific embodiments for the correlator, such as a multiplier followed by an integrator (Fig. 3) or a sign-based correlator that analyzes the polarity of the signals (Fig. 4). A party could argue the term should be limited to these or similar mathematical operations ('854 Patent, col. 5:8-19, col. 5:30-44).
'328 Patent
- The Term: "determining substantially less than all of the amplitude distortion"
- Context and Importance: This limitation is critical for distinguishing the invention from conventional equalizers that compensate for all distortion. Infringement hinges on whether the accused system isolates and measures a specific subset of the total channel distortion.
- Intrinsic Evidence for a Broader Interpretation: The use of "substantially" suggests the term does not require perfect isolation of one distortion source. A plaintiff could argue it covers any system that is designed to primarily compensate for a specific, dominant portion of the total distortion rather than the entire end-to-end channel.
- Intrinsic Evidence for a Narrower Interpretation: The specification describes a specific technical implementation where an adaptive filter's error signal is used to represent the distortion from only the adjacent subscriber loop and noise from the four-wire path ('328 Patent, col. 4:33-38). A defendant could argue this limits the claim to systems that physically or algorithmically isolate and measure the distortion of a specific channel segment.
VI. Other Allegations
- Indirect Infringement: For the '537, '657, '501, and '472 patents, the complaint alleges both induced and contributory infringement. The allegations are based on Defendant providing DSL modems and equipment to customers and partners, allegedly knowing these products are especially adapted for infringement and have no substantial non-infringing uses. The provision of "instruction materials, training, and consulting services" is cited as evidence of intent to induce (Compl. ¶29-32, ¶39-42, ¶49-50, ¶57-58).
- Willful Infringement: The complaint alleges willful infringement for all six asserted patents. This allegation is based on the defendant's alleged continued infringement after receiving actual knowledge of the patents via an infringement notice letter dated December 10, 2012 (Compl. ¶18, ¶23, ¶28, ¶38, ¶48, ¶56).
VII. Analyst’s Conclusion: Key Questions for the Case
- A central issue will be one of evidentiary proof: The complaint makes broad allegations without specific factual support. A key question for the litigation will be whether Plaintiff can, through discovery, produce evidence that Defendant's DSL systems perform the specific, nuanced technical steps recited in the claims (e.g., correlation-based disconnect detection, segmented distortion analysis, or automatic spectrum class selection), as opposed to more conventional or alternative techniques.
- The case may also turn on a question of technical scope and applicability: The earlier patents in the suit were filed in the 1990s and address problems in the context of dial-up, cellular, and early data communications. A core question will be whether the claims, construed in light of their original technical context, can be read to cover the architectures and standardized protocols of the accused DSL systems.
- For the '501 and '472 patents, a key point of dispute will likely be one of functional operation: Does the accused DSL equipment perform the claimed function of actively and automatically measuring line characteristics to select from a plurality of "Spectrum Management Classes," or is its operational mode pre-configured by a service provider, potentially falling outside the scope of the claims?