PTAB

IPR2018-01388

RPX Corp v. Vertical Connection Technologies LLC

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1. Case Identification

2. Patent Overview

  • Title: System and Method for IP Handoff
  • Brief Description: The ’917 patent describes a method for vertical handoff of a mobile device's active network connection between heterogeneous wireless networks, such as from a wireless local area network (WLAN) to a wireless wide area network (WWAN). The patent purports to solve the problem of providing a seamless vertical handoff, which it alleged no known system previously offered.

3. Grounds for Unpatentability

Ground 1: Claims 12-15, 18-21, 23, and 25 are obvious over Sanmateu in view of Taylor.

  • Prior Art Relied Upon: Sanmateu (a 2002 journal article on seamless mobility across IP networks) and Taylor (a 1999 journal article on seamless handover in mobile networks).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Sanmateu, which describes a Mobile IP (MIP) framework for vertical handoffs between WLAN and General Packet Radio Service (GPRS) networks, discloses the core elements of independent claim 12. Sanmateu allegedly teaches monitoring a WLAN signal level, initiating a vertical handoff to GPRS when the signal drops below a pre-defined threshold (i.e., becomes "undesirable"), and tunneling the active connection over the GPRS network to the mobile node. For the "caching and replaying" limitation, Petitioner asserted it was inherently disclosed by Sanmateu's use of the TCP protocol, which requires storing (caching) packets to enable retransmission (replaying) of lost packets. Taylor was cited to explicitly teach various cache-and-replay techniques to improve TCP performance.
    • Motivation to Combine: Petitioner contended that Sanmateu identifies TCP performance issues arising during inter-access handoffs. Taylor directly addresses these known issues by describing several methods (e.g., Snoop TCP, SACK TCP) to improve TCP performance over wireless links by mitigating packet loss. A person of ordinary skill in the art (POSITA) would combine Taylor’s solutions with Sanmateu’s framework to improve the reliability and efficiency of TCP data transfers during the described WLAN-to-GPRS handoff.
    • Expectation of Success: A POSITA would have a high expectation of success, as Taylor’s techniques were well-known improvements fully compatible with the standard TCP protocol and MIP architecture described by Sanmateu.

Ground 2: Claims 12-15, 18-22, and 25 are obvious over Ye in view of the ’005 patent.

  • Prior Art Relied Upon: Ye (a 2002 journal article on Mobile IP handoff between hybrid networks) and the ’005 patent (Patent 6,907,005).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued Ye provides an alternative primary reference that also describes MIP-based vertical handoffs between WLAN and GPRS networks. Ye allegedly teaches monitoring WLAN signal strength (RSS) and initiating a handoff when the signal persists below a threshold value for a set time. Ye further discloses tunneling packets from a home agent to a foreign agent over the GPRS network. Critically, Petitioner argued Ye explicitly discloses the "caching and replaying" limitation through its pre-handoff scheme, where the GPRS foreign agent receives and buffers (caches) IP packets intended for the mobile host and only sends (replays) them over the air interface after the handoff is formally confirmed.
    • Motivation to Combine: The ’005 patent, which teaches a flexible Automatic Repeat reQuest (ARQ) scheme for reliable data delivery, was presented as an alternative basis for the caching and replaying limitation. Petitioner asserted that GPRS networks commonly used ARQ at the link layer to minimize packet loss. A POSITA implementing Ye's system would have been motivated to incorporate a known, advantageous ARQ scheme like that in the ’005 patent to enhance data delivery reliability at the link layer, complementing Ye's higher-level buffering scheme.
    • Expectation of Success: Success was expected because ARQ was a fundamental error-control technique for wireless systems like GPRS. The ’005 patent described a flexible scheme designed to be employed in any communications system where data packets are passed between nodes, making it directly applicable to Ye's architecture.

Ground 3: Claims 16-17 are obvious over Sanmateu and Taylor in view of Pahlavan.

  • Prior Art Relied Upon: Sanmateu, Taylor, and Pahlavan (a 2000 journal article on handoff in hybrid mobile data networks).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground builds on Ground 1 to address claims 16-17, which add limitations for first determining if a second WLAN signal is desirable and initiating a horizontal handoff (WLAN-to-WLAN) before attempting a vertical handoff. While Sanmateu focuses on vertical handoffs, Pahlavan explicitly teaches horizontal handoff procedures in a hybrid WLAN/GPRS network, wherein a mobile device scans for and connects to the WLAN access point with the strongest beacon.
    • Motivation to Combine: Petitioner argued that Pahlavan teaches it is "almost always preferable" to use a high-bandwidth WLAN over a WWAN network, which can be "two orders of magnitude" slower. A POSITA would thus be motivated to implement a handoff prioritization scheme, modifying Sanmateu’s system to first attempt a horizontal handoff to another available WLAN (per Pahlavan) before resorting to the less desirable vertical handoff to GPRS. This common-sense approach would optimize for network speed and cost.
    • Expectation of Success: A POSITA would expect success because combining horizontal and vertical handoff strategies was a well-understood and compatible approach in Mobile IP architectures designed for heterogeneous networks.

  • Additional Grounds: Petitioner asserted additional obviousness challenges for specific dependent claims, combining the primary references (Sanmateu or Ye) with secondary art such as La Porta (for a foreign agent at a base station controller), Sanmateu (for a co-located care-of-address), and Aust (for tunneling through a Network Address Translation gateway).

4. Key Claim Construction Positions

  • Petitioner proposed construing "home agent" and "foreign agent" as comprising a Mobile IP (MIP) home agent and foreign agent, respectively, as defined by the RFC-2002 standard. This construction is central to the argument that the ’917 patent claims known elements of the open MIP standard and that its functionality would have been obvious from prior art implementing that standard.

5. Relief Requested

  • Petitioner requests institution of inter partes review and cancellation of claims 12-25 of the ’917 patent as unpatentable.