PTAB

IPR2024-01044

NPX USA Inc v. Bell Northern Research LLC

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Wireless OFDM Transmissions with Extended Long Training Sequences
  • Brief Description: The ’629 patent is directed to wireless orthogonal frequency division multiplexing (OFDM) transmissions. The technology purports to improve upon the prior art 52-subcarrier long training sequence (LTS) used in the 802.11a/g standards by adding four additional subcarriers to create an extended long training sequence (ELTS) with a total of 56 active subcarriers.

3. Grounds for Unpatentability

Ground 1: Claims 1, 4, 8-23, and 27 are obvious over Jones, the 802.11a and 802.11-1999 standards, Zelst, and Boer.

  • Prior Art Relied Upon: Jones (Patent 7,453,793), Zelst (Patent 7,599,332), Boer (Patent 8,014,267), IEEE 802.11a-1999 standard (“802.11a”), and IEEE 802.11-1999 standard (“802.11-1999”).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that the combination of references taught every element of the challenged claims. Jones taught the fundamental architecture for an 802.11a-compatible transmitter, including a signal generator and Inverse Fourier Transformer (IFFT), and disclosed improving 802.11a by using an ELTS with more than 52 subcarriers (disclosing a full 63-subcarrier sequence). Zelst and Boer specifically taught that an ELTS for 802.11a should use exactly 56 subcarriers because that is the number that fits within the existing 802.11a spectral mask. Critically, Petitioner asserted that Jones, Zelst, and Boer all disclosed the precise encoding sequence for the 56-subcarrier ELTS that is explicitly recited in claim 1 of the ’629 patent. For dependent claims, the combination taught using BPSK encoding (claim 8), the use of processors (claim 10), backward compatibility (claim 13), and that the specific sequence results in the claimed 3.6 dB peak-to-average power ratio (claim 4).
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine these references as they were all from the same field, shared common inventors, and were directed to the same purpose of improving the 802.11a standard. The primary motivations were to increase data throughput and improve channel estimation (by allowing interpolation instead of extrapolation of edge subcarriers, as taught by Boer) while maintaining backward compatibility with legacy 802.11a devices, a goal explicitly stated in both Jones and Zelst.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success because the combination involved applying a known technique (extending a training sequence) to a known system (802.11a architecture) to achieve predictable results. The ’629 patent itself admitted that 56-subcarrier ELTSs were under consideration for the 802.11n standard and did not describe overcoming any technical hurdles.

Ground 2: Claims 1, 4, 8-23, and 27 are obvious over Jones, the 802.11a and 802.11-1999 standards, and Boer.

  • Prior Art Relied Upon: Jones (Patent 7,453,793), Boer (Patent 8,014,267), 802.11a, and 802.11-1999.
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground was presented as duplicative of Ground 1, excluding the Zelst reference as a precaution against arguments that Zelst is not prior art. The core argument remained the same, relying on Boer’s express teaching (including its incorporated provisional application) that 56 subcarriers would fit within the 802.11a spectral mask to render obvious the implementation of Jones’s general ELTS teaching with exactly 56 subcarriers.
    • Motivation to Combine: The motivation was identical to Ground 1: to improve the performance of 802.11a systems in a predictable manner while maintaining backward compatibility.
    • Expectation of Success: The expectation of success was identical to Ground 1, as the combination still relied on applying known modifications to a well-understood system.

4. Key Claim Construction Positions

  • Petitioner argued that the term “an optimal extended long training sequence with a minimal peak-to-average power” (claim 1) did not require construction by the Board.
  • The petition asserted that the phrase is adequately and explicitly defined by the table of encodings for 56 specific subcarriers recited directly within claim 1. This position was central to the obviousness argument, as it directly equated the claimed "optimal" sequence with the specific 56-subcarrier sequence disclosed in the prior art references of Jones, Zelst, and Boer.

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. Petitioner contended that highly material prior art, specifically the provisional applications for Zelst and Boer which contained the strongest teachings on using exactly 56 subcarriers, was not of record. Furthermore, it was argued that prior art that was of record, namely Jones, was not substantively discussed or applied by the examiner, despite its teaching of the claimed encoding sequence and a range of subcarriers (53-63) that rendered 56 obvious.

6. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1, 4, 8-23, and 27 of Patent RE48,629 as unpatentable under 35 U.S.C. §103.