PTAB

IPR2024-01044

NPX USA, Inc. v. Bell Northern Research, LLC

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1. Case Identification

2. Patent Overview

  • Title: Modified Preamble Structure for IEEE 802.11a Extensions
  • Brief Description: The ’629 patent is directed to wireless orthogonal frequency division multiplexing (OFDM) transmissions. The technology purports to improve upon the standard 52-subcarrier long training sequence (LTS) used in the IEEE 802.11a standard by defining an extended long training sequence (ELTS) that uses exactly 56 active subcarriers with a specific, predefined encoding sequence.

3. Grounds for Unpatentability

Ground 1: Claims 1, 4, 8-23, and 27 are obvious under 35 U.S.C. §103 over the combination of Jones, 802.11a, 802.11-1999, Zelst, and Boer.

  • Prior Art Relied Upon: Jones (Patent 7,453,793), the IEEE 802.11a-1999 Standard (“802.11a”), the IEEE 802.11-1999 Standard (“802.11-1999”), Zelst (Patent 7,599,332), and Boer (Patent 8,014,267).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that the combination of references taught all limitations of the challenged claims. Jones taught the fundamental functional blocks of an 802.11a system (signal generator, Inverse Fourier Transformer) and the concept of improving it by using an ELTS over a greater number of subcarriers. Jones disclosed a 63-subcarrier sequence that contains the exact 56-subcarrier encoding sequence recited in claim 1[1f]. To address the limitation of "exactly 56 active sub-carriers" (claim 1[1e]), Petitioner relied on Zelst and Boer. Zelst explicitly taught an ELTS "carried by exactly 56 subcarriers" that used the identical encoding sequence claimed. Boer taught that 56 subcarriers fit within the 802.11a spectral mask and disclosed the 16 possible encoding schemes for the four new subcarriers, including the specific one claimed in the ’629 patent.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine the references for several predictable purposes. These included increasing data throughput as taught by Zelst and Jones, improving channel estimation by allowing interpolation instead of extrapolation of edge subcarriers as taught by Boer, and maintaining backward compatibility with legacy 802.11a devices, a goal shared by both Zelst and Jones.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success because the combination involved applying a known technique (extending an LTS) to a known system (an 802.11a transmitter) to achieve predictable results. The prior art references shared common inventors and a common goal of improving the 802.11a standard, and the ’629 patent itself described no technical hurdles that had to be overcome.

Ground 2: Claims 1, 4, 8-23, and 27 are obvious under §103 over the combination of Jones, 802.11a, 802.11-1999, and Boer.

  • Prior Art Relied Upon: Jones (Patent 7,453,793), 802.11a, 802.11-1999, and Boer (Patent 8,014,267).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground was presented as an alternative to Ground 1, excluding Zelst out of an abundance of caution due to litigation arguments by the Patent Owner questioning Zelst's status as prior art. Petitioner asserted that Jones and Boer alone were sufficient. Jones provided the underlying system architecture, the concept of an ELTS, and a 63-subcarrier sequence that included the claimed 56-value encoding. Boer provided the critical, explicit teaching to use "exactly 56" subcarriers by adding four subcarriers to the legacy 52, and disclosed the specific encoding for those four new subcarriers, which matched the claimed sequence.
    • Motivation to Combine: The motivations were identical to those in Ground 1. A POSITA would combine Jones and Boer to increase data rates and improve channel estimation while maintaining compatibility, as the combination of teachings from these references addressed all of these known goals in the art.
    • Expectation of Success: The expectation of success was similarly high, as the combination of Jones and Boer involved known modifications to a standard system to achieve the predictable benefits described in the references.

4. Key Claim Construction Positions

  • "an optimal extended long training sequence with a minimal peak-to-average power" (claim 1): Petitioner argued that the Board need not construe the outer bounds of the terms "optimal" or "minimal peak-to-average power." The rationale was that claim 1 itself explicitly defines the training sequence through the detailed encoding table in limitation [1f]. The ’629 patent specification then admits this very sequence is "optimal" and has a minimal peak-to-average power ratio (PAPR). Therefore, any sequence that matches the table in claim 1[1f], as the prior art sequences do, inherently meets this limitation.

5. Arguments Regarding Discretionary Denial

  • Petitioner argued that the Board should not exercise its discretion to deny institution under 35 U.S.C. § 325(d). The core argument was that the examiner committed clear error during the reissue prosecution that led to the ’629 patent. Specifically, Petitioner contended that the new combinations of prior art presented in the petition were never considered by the examiner. Key references like Boer and the 802.11a standard were not of record during reissue. Furthermore, references that were of record, such as Jones and Zelst, were not substantively analyzed or appreciated for their teachings that are material to the claims.

6. Relief Requested

  • Petitioner requests the institution of an inter partes review and the cancellation of claims 1, 4, 8-23, and 27 of the ’629 patent as unpatentable.