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IPR2021-01391

Solid Inc v. CommScope Technologies LLC

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Point-to-Multipoint Digital Radio Frequency Transport
  • Brief Description: The ’982 patent describes a digital distributed antenna system for extending radio frequency (RF) coverage into areas with poor signal reception. The system uses a digital host unit that communicates with multiple remote units, converting analog RF signals to digital for transmission on a forward path and, on a reverse path, digitally summing signals received from multiple remote units before converting them back to analog.

3. Grounds for Unpatentability

Ground 1: Obviousness over Oh - Claims 65-69 and 74 are obvious over Oh.

  • Prior Art Relied Upon: Oh (Korean Laid-Open Disclosure No. KR1999-0064537).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Oh, a Korean patent application publication, discloses all limitations of the challenged claims. Oh describes a digital optical repeater system with a "master unit" (analogous to the claimed "first unit") and multiple "slave units" (the claimed "second units") for extending RF signals into shadow areas. Petitioner asserted that the key limitation of digitally summing upstream signals at the host unit is taught by Oh's master unit, which includes a "digital combiner unit" (430) that aggregates digital samples received from multiple slave units. This digital combiner receives four 12-bit signals and combines them to create a 14-bit signal, which Petitioner contended is a digital summing operation. The resulting summed digital signal is then converted to an analog signal by a digital-to-analog converter unit for transmission to a base station, meeting the core limitations of independent claims 65 and 74.
    • Motivation to Combine (for §103 grounds): Not applicable as this ground relies on a single reference. Petitioner asserted Oh alone renders the claims obvious.
    • Expectation of Success (for §103 grounds): Not applicable.
    • Key Aspects: The central argument was that Oh, a reference not considered during prosecution, teaches the key inventive concept articulated by the patent owner: performing digital summing of RF signals at a central host unit.

Ground 2: Obviousness over Oh in view of Schwartz - Claims 11-24, 33, and 36 are obvious over Oh in view of Schwartz.

  • Prior Art Relied Upon: Oh (Korean Laid-Open Disclosure No. KR1999-0064537) and Schwartz (Patent 5,883,882).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued this combination renders obvious claims requiring a "digital expansion unit." Oh was asserted to teach the base digital RF transport system with a host ("master unit") and remote units ("slave units"), including the digital summing feature. Schwartz, which describes an analog RF distribution system, was cited for its teaching of using "intermediate stations" to expand a network's topology. These intermediate stations act as repeaters, allowing for a greater number of remote units than can be connected directly to the host's physical ports. The combination proposed implementing Schwartz's expandable topology of intermediate stations into Oh's digital system, where Schwartz's "intermediate station" functions as the claimed "digital expansion unit."
    • Motivation to Combine (for §103 grounds): A person of ordinary skill in the art (POSITA) would combine Oh and Schwartz to overcome an inherent limitation in Oh's system. Oh's master unit has a fixed number of optical ports, limiting the number of slave units it can support. Schwartz directly addresses this problem by teaching the use of intermediate stations to create a daisy-chained, expandable network. A POSITA would have been motivated to apply Schwartz's well-known topology solution to Oh's digital system to create a more scalable and flexible network.
    • Expectation of Success (for §103 grounds): A POSITA would have a reasonable expectation of success because combining the references involved applying a known network expansion technique (Schwartz) to a known digital transport system (Oh) to achieve the predictable result of increased network capacity.

Ground 3: Obviousness over Oh in view of Koschek - Claims 52-64 and 70-73 are obvious over Oh in view of Koschek.

  • Prior Art Relied Upon: Oh (Korean Laid-Open Disclosure No. KR1999-0064537) and Koschek (Patent 5,379,455).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground addressed claims requiring remote powering of units and specific signal resolution features. Petitioner again relied on Oh for the fundamental digital transport system. The first key feature, a "power distribution interface," was argued to be taught by Koschek. Koschek discloses an RF transport system where remote amplifiers can be powered from a central location via power transmitted "down the signal or other cables." The combination involved adding Koschek's remote powering method to Oh's system. The second key feature, digitally summing upstream samples with a resolution greater than the individual samples, was argued to be taught by Oh alone. Oh's system samples upstream signals at 12-bit resolution and its digital combiners create a 14-bit signal from four such 12-bit signals, directly meeting this limitation.
    • Motivation to Combine (for §103 grounds): A POSITA would combine Oh and Koschek for practical reasons. Oh is silent on how its remote slave units are powered. Koschek provides a known and advantageous solution for powering remote units, especially those in locations without accessible power outlets, by routing power from a central point. An installer of a system like Oh's would find it efficient to run power along with the necessary signal cables, making the combination a logical and predictable design choice.
    • Expectation of Success (for §103 grounds): Success was expected because adding a conventional remote powering scheme (Koschek) to a digital distribution system (Oh) was a straightforward integration of known technologies to solve a common logistical problem.

4. Relief Requested

  • Petitioner requested the institution of an inter partes review and the cancellation of claims 11-24, 33, 36, and 52-74 of Patent 7,639,982 as unpatentable.