PTAB

IPR2014-01185

Ericsson Inc v. Intellectual Ventures II LLC

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Key Events
Petition

1. Case Identification

2. Patent Overview

  • Title: Preamble Structures for Single-Input, Single-Output (SISO) and Multi-Input, Multi-Output (MIMO) Communication Systems
  • Brief Description: The ’127 patent describes frame structures for wireless telecommunication systems, such as Orthogonal Frequency Division Multiplexing (OFDM) systems. The invention focuses on an efficient preamble structure, comprising specific training symbols, that precedes a data structure to facilitate time and frequency synchronization, parameter estimation, and improved system throughput.

3. Grounds for Unpatentability

Ground 1: Obviousness over Schmidl and Arslan - Claims 1-3 and 5 are obvious over Schmidl in view of Arslan.

  • Prior Art Relied Upon: Schmidl (Patent 5,732,113) and Arslan (Patent 6,411,649).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Schmidl, the primary reference, disclosed the core elements of the claimed invention. Schmidl taught an OFDM transmitter that generates a data frame structure containing a preamble (an OFDM training sequence) followed by a data structure. This preamble included a first training symbol with two identical halves (meeting the "enhanced training symbol" limitation) and a second training symbol, used for synchronization. However, Schmidl did not explicitly teach inserting pilot symbols within the data blocks. Arslan was introduced to remedy this deficiency, as it taught a frame structure where known pilot symbols are periodically inserted into the data/information portions to retrain the channel estimator and maintain synchronization.
    • Motivation to Combine (for 35 U.S.C. §103 grounds): A person of ordinary skill in the art (POSITA) would combine the teachings because both Schmidl and Arslan addressed the same problem of improving synchronization in wireless communication systems. Petitioner asserted it would have been obvious to apply Arslan’s known technique of inserting pilot symbols into the data structure of Schmidl’s frame to yield the predictable result of enhanced synchronization.

Ground 2: Obviousness over Schmidl, Arslan, and Kim - Claims 4 and 6-10 are obvious over Schmidl in view of Arslan and Kim.

  • Prior Art Relied Upon: Schmidl (Patent 5,732,113), Arslan (Patent 6,411,649), and Kim (Patent 7,012,881).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground builds upon the combination of Schmidl and Arslan to address dependent claims reciting specific structural details of the training symbols. Claims such as 4, 6, 7, and 9 required the training blocks to be divided into a specific number of sections (e.g., four) and for cyclic prefixes and training blocks to have a specific number of samples (e.g., G=N/I). Petitioner argued that while Schmidl taught dividing the enhanced training symbol into two halves, Kim explicitly disclosed a prior art OFDM system where training symbols were divided into four sections. Kim further taught that each symbol includes a guard interval (cyclic prefix) and a data block with a specific number of samples (e.g., N=64).
    • Motivation to Combine (for §103 grounds): Because both Schmidl and Kim were directed at improving synchronization in OFDM systems using structured training symbols, a POSITA would have been motivated to apply Kim's known technique of dividing training symbols into four sections with specific sample counts to the training symbols in Schmidl's system. This modification would have been a simple and predictable design choice to enhance synchronization performance.

Ground 3: Obviousness over Schmidl, Arslan, Kim, and Heiskala - Claim 17 is obvious over Schmidl in view of Arslan, Kim, and Heiskala.

  • Prior Art Relied Upon: Schmidl (Patent 5,732,113), Arslan (Patent 6,411,649), Kim (Patent 7,012,881), and Heiskala (Patent 6,298,035).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground targeted claim 17, which added the limitation that the number of modulators and transmit antennas is two (i.e., a MIMO or transmit diversity system). The base combination did not explicitly teach a two-transmitter system. Petitioner introduced Heiskala, which discussed Schmidl's transmitter and proposed an improved OFDM system using two transmitters to send training symbols over separate channels. Heiskala explicitly disclosed using a first transmitter for a first set of training symbols and a second transmitter for a second set to achieve transmit diversity and mitigate multipath fading.
    • Motivation to Combine (for §103 grounds): Heiskala explicitly proposed improving upon systems like Schmidl's by employing a two-transmitter architecture. Therefore, a POSITA would have been directly motivated to apply the known technique of using two transmitters, as taught by Heiskala, to the system derived from Schmidl, Arslan, and Kim. This combination would predictably result in a system with improved reliability through transmit diversity.

  • Additional Grounds: Petitioner asserted additional obviousness challenges based on combinations of Schmidl and Kim (for method claims 20-21) and Schmidl, Kim, and Heiskala (for method claims 23-24), which relied on analogous theories for mapping the method steps to the functions disclosed in the prior art references.

4. Key Claim Construction Positions

  • frame structure: Petitioner argued this term should be construed to mean "a unit of transmission comprising a preamble structure followed by a data structure," based on its consistent description in the ’127 patent’s specification and figures.
  • preamble structure: Petitioner proposed this term means "a portion of the frame structure located near the beginning of the frame structure, before the data structure, and comprising at least two training symbols." This construction was based on the specification’s description of preambles for providing synchronization.
  • enhanced training symbol: This term was central to patentability during prosecution. Petitioner argued it should be construed as "a training symbol comprising a plurality of sections in a single symbol." This interpretation was based on the specification's description and Figure 7, which shows the symbol subdivided into smaller sections for efficient synchronization.

5. Relief Requested

  • Petitioner requested the institution of an inter partes review and the cancellation of claims 1-10, 17, 20, 21, 23, and 24 of the ’127 patent as unpatentable.