PTAB

IPR2018-01739

Ruckus Wireless, Inc. v. HERA WIRELESS S.A.

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1. Case Identification

2. Patent Overview

  • Title: Transmitting Apparatus for an Orthogonal Frequency-Division Multiplexing (OFDM) Signal
  • Brief Description: The ’400 patent describes a method and apparatus for wireless communication systems that support both Multiple-Input Multiple-Output (MIMO) devices and legacy non-MIMO devices (termed "target systems," e.g., 802.11a compliant). The invention claims a specific burst signal format that includes both non-MIMO and MIMO portions, allowing a legacy device to identify and disregard a MIMO transmission early, thereby conserving power.

3. Grounds for Unpatentability

Ground 1: Claims 1-2 are obvious over WWiSE in view of 802.11a.

  • Prior Art Relied Upon: WWiSE (a proposal for the IEEE 802.11n standard, document IEEE 802.11-04/0886r0) and the IEEE 802.11a standard (IEEE Std 802.11a-1999).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that WWiSE, a proposal to enhance the 802.11a standard, taught a "mixed-mode" frame format for MIMO-OFDM systems. This frame format included a non-MIMO training signal (legacy short and long training sequences), a non-MIMO signal field (SIGNAL-MM), a MIMO-specific signal field (SIGNAL-N), and a MIMO training signal, arranged in the order required by the claims. WWiSE also disclosed using different pilot signal patterns for different antennas and cyclically shifting the signals transmitted from multiple antennas to achieve diversity. The 802.11a standard provided the foundational teachings for the non-MIMO "target system" frame format, pilot signal modulation (BPSK), and pilot patterns, which WWiSE built upon.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine WWiSE and 802.11a because WWiSE was an official proposal explicitly designed to be an improvement on, and backward compatible with, the 802.11a standard. WWiSE directly referenced and incorporated functionalities from 802.11a.
    • Expectation of Success: A POSITA would have a high expectation of success, as the references were written to be combined to ensure interoperability between new MIMO systems and legacy 802.11a devices.

Ground 2: Claims 1-2 are obvious over TGn-Sync in view of 802.11a.

  • Prior Art Relied Upon: TGn-Sync (a proposal for the IEEE 802.11n standard, document IEEE 802.11-04/0889r0) and the IEEE 802.11a standard (IEEE Std 802.11a-1999).
  • Core Argument for this Ground:
    • Prior Art Mapping: Similar to WWiSE, the TGn-Sync proposal taught an enhanced preamble design to ensure "seamless interoperability" with legacy 802.11 devices. Petitioner asserted that TGn-Sync disclosed a packet format with a legacy preamble (L-STF, L-LTF) serving as the non-MIMO training signal, a legacy signal field (L-SIG) as the non-MIMO signal, a high-throughput signal field (HT-SIG) as the MIMO signal, and high-throughput training fields (HT-STF, HT-LTF) as the MIMO training signal, followed by data. TGn-Sync also explicitly taught using cyclic delay diversity, which cyclically shifts transmissions across antennas. Furthermore, it defined different pilot patterns for high-throughput (MIMO) transmissions compared to legacy 802.11a transmissions while maintaining the same BPSK modulation scheme.
    • Motivation to Combine: A POSITA would combine TGn-Sync and 802.11a because TGn-Sync was a direct response to a call for proposals to improve 802.11a and was designed for backward compatibility. TGn-Sync cited and relied on multiple sections of the 802.11a standard for its definitions of legacy signals and modulation behavior.
    • Expectation of Success: Success was predictable and expected, as the explicit purpose of the TGn-Sync proposal was to integrate its new MIMO features with the existing 802.11a framework.

Ground 3: Claims 1-2 are obvious over Narasimhan in view of Van Zelst.

  • Prior Art Relied Upon: Narasimhan (Patent 7,995,455) and Van Zelst (Patent 7,372,913).
  • Core Argument for this Ground:
    • Prior Art Mapping: Narasimhan disclosed a MIMO-OFDM system designed to be backward compatible with 802.11a. It taught a frame format containing non-MIMO training signals, a non-MIMO signal (SIGNAL), a MIMO-specific signal (SIGNAL2), and MIMO training signals, thereby teaching the claimed burst format structure. Narasimhan also taught using cyclic delay diversity. However, Narasimhan taught using the standard 802.11a pilot signal scheme for all transmissions. Van Zelst addressed the problem of signal fading in multi-stream systems by teaching the use of distinguishable, varying pilot signal sequences for each spatial stream.
    • Motivation to Combine: A POSITA would have been motivated to modify the pilot signal insertion process of Narasimhan with the teachings of Van Zelst to improve system performance. Van Zelst’s technique of using different pilot patterns for each antenna/stream would allow a receiver in Narasimhan's system to better separate the multiple spatial streams, combat fading, and improve diversity reception, a known benefit for a known problem.
    • Expectation of Success: A POSITA would have had a high expectation of success because combining the two was a matter of applying a known technique (Van Zelst's pilot diversity) to a conventional system (Narasimhan's) to achieve a predictable improvement. The modification was considered a trivial implementation, as it involved multiplying the base 802.11a pilot sequence used by Narasimhan with a known matrix from Van Zelst.

4. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial under §325(d) was not warranted. Grounds 1 and 3 rely on prior art (WWiSE, 802.11a, Narasimhan, and Van Zelst) and arguments that were not before the U.S. Patent and Trademark Office during the original prosecution. While TGn-Sync (used in Ground 2) was submitted in an Information Disclosure Statement (IDS), the combination with 802.11a was never considered by the Examiner, nor was TGn-Sync ever the basis for a rejection. Therefore, Petitioner contended the arguments were not the same or substantially the same as those previously presented.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-2 of Patent 8,295,400 as unpatentable.