PTAB

IPR2021-00492

Corning Optical Communications LLC v. Dali Wireless Inc

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Method and System for Soft Frequency Reuse in a Distributed Antenna System
  • Brief Description: The ’358 patent discloses methods and systems for implementing frequency reuse techniques, such as fractional frequency reuse (FFR) and soft frequency reuse (SFR), in distributed antenna systems (DAS) to mitigate inter-cell interference in wireless communication networks.

3. Grounds for Unpatentability

Ground 1: Obviousness over Fujii and Cannon - Claims 1-21 are obvious over Fujii alone or in combination with Cannon.

  • Prior Art Relied Upon: Fujii (a 2010 journal article on user scheduling in DAS) and Cannon (Application # 2010/0177760).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Fujii discloses the core concept of the ’358 patent: using a DAS with FFR to reduce inter-cell interference by partitioning cells into inner and boundary zones that utilize different frequency reuse factors. Fujii teaches that inner-cell zones can reuse the same frequencies (FRF=1), while adjacent cell-boundary zones use different, cell-specific frequencies (FRF=3). Cannon was asserted to disclose a known, practical implementation of a DAS architecture that a person of ordinary skill in the art (POSITA) would use to build Fujii’s system. Cannon’s DAS includes a host unit (analogous to the claimed Digital Access Unit, or DAU) and a plurality of remote units (analogous to the claimed Digital Remote Units, or DRUs). Petitioner contended the combination of Fujii’s frequency scheme and Cannon’s architecture meets the limitations of independent claims 1, 7, and 15, including providing DRUs that communicate using a first set of frequencies over an inner-cell footprint and a second, different set of frequencies over a larger, surrounding footprint.
    • Motivation to Combine: A POSITA implementing Fujii’s FFR scheduling scheme would be motivated to use a known DAS architecture like that in Cannon. Cannon describes an efficient method for transporting multiple non-adjacent communication bands by segregating relevant spectral regions and discarding unused portions. Petitioner argued this is precisely what is needed to efficiently implement Fujii’s FFR scheme, where different remote units in different cells use distinct, non-overlapping portions of the spectrum. Using Cannon's architecture would result in a more efficient use of fiber bandwidth between the host and remote units.
    • Expectation of Success: The combination required applying Cannon’s well-understood DAS hardware to Fujii’s frequency reuse concept. As both references relate to improving DAS performance and involve conventional RF signal transport, a POSITA would have had a reasonable expectation of success in combining them.

Ground 2: Obviousness of Dependent Claim 4 - Claim 4 is obvious over Fujii in combination with Cannon and in view of Oren.

  • Prior Art Relied Upon: Fujii (a 2010 journal article), Cannon (Application # 2010/0177760), and Oren (Application # 2008/0232305).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground builds upon the combination of Fujii and Cannon asserted in Ground 1 to address the additional limitation of dependent claim 4: coupling the Base Transceiver Stations (BTSs) to the DAU using "BTS sector RF connections." While Fujii and Cannon provide the underlying DAS with FFR, Petitioner argued that Oren explicitly discloses a DAS where the inputs are connected to the sectorized RF ports of a base station. Oren teaches that in high-capacity environments, multiple sectors from a single base station can be used to "feed" a DAS, with its Radio Interface Unit (RIU) having multiple, separate interfaces for each base station sector.
    • Motivation to Combine: A POSITA would combine Oren with the teachings of Fujii and Cannon because using sectorized base stations was a standard and well-known configuration for increasing capacity in cellular deployments, including for LTE systems. Oren provides an explicit suggestion to use sectorized RF connections from a base station as inputs to a DAS. Therefore, it would have been a natural and obvious design choice to use sectorized inputs for the DAS described in the primary combination of Fujii and Cannon.
    • Expectation of Success: Because sectorized base stations were common and Oren provides a clear roadmap for integrating them with a DAS, a POSITA would have a high expectation of success in making this modification.

4. Key Claim Construction Positions

  • Petitioner argued that several terms should be given their plain and ordinary meaning, defining "Digital Remote Unit (DRU)" as a DAS unit supporting signal transport between users and a central facility/DAU, and a "Digital Access Unit (DAU)" as a DAS unit supporting signal transport between a signal source and one or more DRUs.
  • Critically, Petitioner contended that limitation [1.1] of claim 1 is drafted incorrectly and is inconsistent with the patent’s specification. The claim recites a DRU "configured to receive one or more downlink radio frequencies and to transmit one or more uplink radio frequencies." Petitioner argued that in a DAS, DRUs transmit downlink signals and receive uplink signals. Petitioner therefore proposed that the claim should be interpreted as if the words "transmit" and "receive" were transposed to align with the specification's disclosure.

5. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial under the Fintiv factors would be inappropriate. The petition asserted that the co-pending district court litigation was in its very early stages, with no trial date set and minimal discovery completed. Petitioner stated its intent to file a motion to stay the litigation pending the outcome of the inter partes review (IPR), noting the judge in the case has previously granted such stays. Furthermore, Petitioner argued that the IPR would simplify issues for the district court, as the petition challenges all claims (1-21), whereas the litigation asserted only a subset of those claims (7-13, 15, and 17-21).

6. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-21 of Patent 9,197,358 as unpatentable.