Solid Inc v. CommScope Technologies LLC

1. Case Identification

• Case #: IPR2021-01390
• Patent #: 7,639,982
• Filed: August 12, 2021
• Petitioner(s): SOLiD, Inc.
• Patent Owner(s): CommScope Technologies LLC
• Challenged Claims: 1-10, 25-32, 34, 35, 37-51, and 75-81

2. Patent Overview

• Title: Point-To-Multipoint Digital Radio Frequency Transport
• Brief Description: The ’982 patent discloses a digital distributed antenna system for extending radio frequency (RF) signal coverage. The system includes a digital host unit that communicates with a base station and multiple remote units, converting analog RF signals to digital signals for transport and vice-versa. A key feature is the host unit's ability to digitally sum uplink digital signals received from multiple remote units before converting the summed signal back to analog for the base station.

3. Grounds for Unpatentability

Ground 1a: Obviousness over Oh - Claims 1-10, 25-32, 34, 35, 37-51, and 81 are obvious over Oh.

• Prior Art Relied Upon: Oh (Korean Laid-Open Disclosure No. KR1999-0064537).
• Core Argument for this Ground: Petitioner argued that Oh, a Korean patent application published before the ’982 patent’s priority date, discloses a digital optical repeater system that teaches every element of the challenged claims. The central argument focused on the digital summing feature, which was a key basis for allowance of the ’982 patent. Petitioner contended that Oh's disclosure of a "digital combiner" that "aggregates" and "combines" four 12-bit digital signals to create a 14-bit signal is equivalent to the claimed "digitally summing" operation. Because the Examiner did not have Oh during prosecution, these features were not previously considered.
  • Prior Art Mapping: Petitioner mapped the elements of Oh’s system to the claims. Oh’s “master unit 20” was argued to be a “digital host unit,” and its multiple “slave units 30” correspond to the claimed “digital remote units.” For the key limitation of independent claim 1 ("the digital host unit digitally sums the digitized radio frequency signals"), Petitioner pointed to Oh’s reverse master unit (Fig. 5), which includes a “digital combiner unit 430.” This unit receives four separate 12-bit digital signals from the slave units and combines them into a single 14-bit signal. Petitioner asserted this operation constitutes a digital sum. For claims requiring resolution of the summed signal to be greater than the input signals (e.g., claim 37), Petitioner argued Oh’s creation of a 14-bit output from 12-bit inputs meets this limitation.
  • Motivation to Combine (for §103 grounds): As this is a single-reference ground, the argument was that Oh itself renders the claims obvious by disclosing a complete system with all claimed features.

Ground 1b: Obviousness over Oh in view of Wala - Claims 75-80 are obvious over Oh in view of Wala.

• Prior Art Relied Upon: Oh (Korean Laid-Open Disclosure No. KR1999-0064537) and Wala ("A New Microcell Architecture Using Digital Optical Transport," IEEE, 1993).
• Core Argument for this Ground: This ground built upon the teachings of Oh by adding Wala to address a specific limitation in claims 75 and 78: that the "sample rates used by the host unit and the other units are locked together." Petitioner argued that while Oh does not explicitly disclose locked sampling rates, Wala, which describes a highly similar digital RF transport system, expressly teaches performing A/D sampling at both the host and remote units at a common, locked rate (30.72 MHz). A person of ordinary skill in the art (POSITA) would have been motivated to combine the teachings to ensure system integrity.
  • Prior Art Mapping: Oh was asserted to teach the base system of a host unit digitally summing signals from remote units, as argued in Ground 1a. Wala was introduced to supply the teaching of locking the sample rates between the host and remote units. Wala's disclosure of a common 30.72 MHz sampling rate was mapped directly to the "locked together" limitation.
  • Motivation to Combine (for §103 grounds): Petitioner argued a POSITA would combine Oh and Wala because both references address the same problem of extending RF coverage using digital optical transport and are highly compatible. A POSITA would look to a system like Wala to find specific implementation details, such as optimal sampling frequencies and the need for synchronization, and apply them to Oh’s system architecture to create a more robust and complete design.
  • Expectation of Success (for §103 grounds): A POSITA would have a reasonable expectation of success in locking the sample rates in Oh's system as taught by Wala, as this is a known technique to ensure coherent signal processing and prevent frequency shifts in distributed communication systems.

4. Key Claim Construction Positions

• Petitioner argued that other than the means-plus-function terms in claim 81, claim terms should be given their ordinary and customary meaning.
• For claim 81, Petitioner identified the functions and corresponding structures for several means-plus-function limitations. Crucially, the "means for digitally summing" was identified as performing the function of "digitally summing respective upstream digital RF samples" with the corresponding structure in the ’982 patent specification being "Summer 498." This construction was central to Petitioner's argument that Oh's digital combiners (432, 434, 436, 438) are structural equivalents.

5. Arguments Regarding Discretionary Denial

• Petitioner argued against discretionary denial under 35 U.S.C. §314(a) by noting that it filed two separate petitions to challenge the 81 claims of the ’982 patent, with no more than one ground presented for any given claim across the petitions. Petitioner asserted that both petitions should be instituted due to the large number of claims being challenged.

6. Relief Requested

• Petitioner requested institution of an inter partes review and cancellation of claims 1-10, 25-32, 34, 35, 37-51, and 75-81 of the ’982 patent as unpatentable.