Marvell Semiconductor Inc v. Intellectual Ventures I LLC

1. Case Identification

• Patent #: 6,977,944
• Filed: March 27, 2014
• Petitioner(s): Marvell Semiconductor, Inc.
• Challenged Claims: 7-12, 19-24

2. Patent Overview

• Title: Transmission Protection for Communications Networks Having Stations Operating with Different Modulation Formats
• Brief Description: The ’944 patent relates to a technique for managing shared medium access in wireless networks with both legacy and enhanced stations. The invention proposes a station transmitting a Clear-to-Send (CTS) frame to itself to reserve the medium, aiming to reduce signaling overhead compared to standard Request-to-Send/CTS exchanges.

3. Grounds for Unpatentability

Ground 1: Anticipation over Sherman - Claims 7, 8, 10, 19, 22, and 23 are anticipated under 35 U.S.C. §102 over Sherman.

• Prior Art Relied Upon: Sherman (7,046,690).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Sherman explicitly discloses all elements of the challenged claims. Sherman teaches a station in a mixed-protocol network (e.g., accommodating both standard 802.11 and enhanced 802.11e stations) reserving a shared medium by sending a CTS frame addressed to itself. This self-addressed CTS frame includes a duration field set to a specific value to prevent other stations from transmitting for a defined period, thereby teaching the core limitations of independent claims 7 and 19. Sherman further discloses that this reservation is for transmitting subsequent data frames using a different protocol (e.g., an enhanced protocol not understood by legacy stations), which may use a different modulation scheme.

Ground 2: Obviousness over Chen and Choi - Claims 7, 8, 10-12, 19, 20, 22-24 are obvious over Chen in view of Choi.

• Prior Art Relied Upon: Chen (7,177,294), Choi (7,206,840).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner contended that Chen describes a collision avoidance system for co-existing WLAN and Bluetooth protocols. In Chen, a control point transmits a "jamming signal" to pause WLAN traffic to allow for an uninterrupted Bluetooth transmission. Chen explicitly discloses that this jamming signal can be a standard WLAN CTS packet that sets a reservation duration. However, Chen does not specify the destination address for this CTS packet.
  • Motivation to Combine: A POSITA, seeking to implement the CTS-based jamming signal in Chen’s system, would have been motivated to consult a reference like Choi. Choi teaches a known, predictable, and resource-efficient method to pause WLAN traffic by sending a CTS frame addressed to the sender itself. A POSITA would combine Choi’s self-addressed CTS technique with Chen's system to provide a concrete and effective implementation for the CTS jamming signal.
  • Expectation of Success: Combining Choi's self-addressed CTS with Chen's collision avoidance framework was a simple application of a known technique to solve a known problem, yielding the predictable result of efficient medium reservation.

Ground 3: Obviousness over Sugar and Choi - Claims 7, 8, 10-12, 19, 20, 22-24 are obvious over Sugar in view of Choi.

• Prior Art Relied Upon: Sugar (7,050,452), Choi (7,206,840).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted that Sugar discloses a multi-protocol device mitigating interference between 802.11 and Bluetooth networks by transmitting a "guard packet" using an 802.11 protocol to reserve the channel before a Bluetooth transmission. Sugar teaches that this guard packet includes at least one CTS packet to make other 802.11 stations refrain from transmitting, but it does not specify the addressing of the CTS frame.
  • Motivation to Combine: Similar to the Chen combination, a POSITA implementing Sugar’s system would combine it with Choi's disclosure of a self-addressed CTS frame. This would provide an efficient and established method for addressing the CTS guard packets in Sugar to reserve the medium, avoiding the need for a response from another station and reducing system complexity.
  • Expectation of Success: Applying Choi's well-understood self-addressing method to Sugar's CTS guard packets would have been a straightforward design choice for a POSITA, with a high expectation of successfully achieving efficient medium reservation in a multi-protocol environment.
• Additional Grounds: Petitioner asserted additional obviousness challenges, including combinations of Sherman with Admitted Prior Art (APA) from the ’944 patent’s specification, and combinations of Chen/Choi and Sugar/Choi with APA. These grounds were used to demonstrate that specific modulation schemes recited in dependent claims (e.g., Orthogonal Frequency Division Multiplexing and Complementary Code Keying) were well-known in the context of the primary references.

4. Key Claim Construction Positions

• "Frame indicating clear to send that is addressed to the sender...": Petitioner argued that, based on the ’944 patent’s prosecution history, this term should be construed to cover a station sending a CTS frame to itself (i.e., using its own address as the destination). This construction was central to mapping the teachings of prior art like Sherman and Choi.
• "Expected length of time required to transmit at least one data frame": Petitioner asserted this term is not limited to the exact duration of a single data frame but can be longer, for example, to also cover the time for a corresponding acknowledgement frame. This broad construction allows prior art duration fields that reserve the medium for an entire transaction to meet the limitation.
• "Modulation scheme": Petitioner argued this term should be interpreted broadly to cover entire communication protocols (e.g., 802.11b) and their associated modulation techniques (e.g., CCK), not just the modulation technique in isolation. This was used to map references discussing different 802.11 protocols.

5. Key Technical Contentions

• The petition's central technical contention was that the ’944 patent's allegedly novel feature—reserving a communications medium by transmitting a CTS frame to oneself—was not novel at the time of invention. Petitioner argued this technique was a well-known solution in the art for managing channel access in mixed-protocol environments (e.g., legacy/enhanced 802.11, or 802.11/Bluetooth), as explicitly taught by references like Sherman, Choi, and Sugar to solve the same problem addressed by the ’944 patent.

6. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 7-12 and 19-24 of Patent 6,977,944 as unpatentable.