PTAB

IPR2018-01753

AT&T Mobility LLC v. Vertical Connection Technologies LLC

Log In
Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Vertical Handoff in a Wireless Network
  • Brief Description: The ’917 patent discloses a "seamless vertical handoff method" for a mobile device to switch between different types of wireless networks, such as moving from a wireless local area network (WLAN) to a wireless wide area network (WWAN).

3. Grounds for Unpatentability

Ground 1: Claims 12-15 and 18-21 are anticipated by Ye under 35 U.S.C. §102.

  • Prior Art Relied Upon: Ye ("The Mobile IP Handoff Between Hybrid Networks," an IEEE publication from 2002).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Ye, which describes Mobile IP handoff between GPRS (a WWAN) and 802.11 (a WLAN), discloses every limitation of independent claim 12. Ye allegedly teaches monitoring a WLAN signal, initiating a handoff to a WWAN when the WLAN signal strength drops below a threshold (making it "undesirable"), tunneling the active network connection over the WWAN, and caching packets at the WWAN's foreign agent during a "pre-handoff" phase for later replay to the mobile device after the handoff is complete. Petitioner further contended that Ye discloses the additional limitations of dependent claims 13-15 and 18-21, such as establishing the WWAN connection (claim 13) and initiating a handoff back to the WLAN when its signal becomes "desirable" again (claim 18).
    • Key Aspects: The core of this ground rested on mapping Ye's "pre-handoff phase," where a mobile host begins registration with the GPRS network while still on the WLAN, to the ’917 patent’s claimed steps. Petitioner asserted Ye’s multi-tunneling of packets to both networks, with the GPRS foreign agent storing them in a buffer, directly corresponds to the claimed "caching and replaying" limitation.

Ground 2: Claims 16 and 17 are obvious over Ye in view of Guo.

  • Prior Art Relied Upon: Ye (as above) and Guo (Patent 6,982,949).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued Ye teaches the base method of claim 13 (vertical handoff from WLAN to WWAN). The additional limitation of claim 16 is determining whether a second WLAN signal is desirable before initiating the vertical handoff. While Ye implies using WLAN as long as possible, Guo explicitly teaches checking for another available WLAN cell for a horizontal handoff before resorting to a vertical handoff to a WWAN. Guo describes a mobile device detecting a cell boundary and checking for another WLAN signal above a threshold. Claim 17, which adds initiating a horizontal handoff, is also taught by Guo.
    • Motivation to Combine: A POSITA would combine Ye and Guo to improve the performance of Ye’s system. Both references address mobility challenges between different network types and recognize that WLANs offer higher quality of service than WWANs. A POSITA would be motivated to incorporate Guo's strategy of prioritizing a horizontal handoff between WLANs into Ye's system to prevent premature or unnecessary vertical handoffs to the lower-quality WWAN, thereby keeping the user on the superior network for as long as possible.
    • Expectation of Success: The combination involved applying a known technique (checking for available WLANs before vertical handoff) to improve a known system (Ye's vertical handoff method). A POSITA would have had a high expectation of success because horizontal handoffs between WLAN cells were a well-known and common technique.

Ground 3: Claim 22 is obvious over Ye in view of Magret.

  • Prior Art Relied Upon: Ye (as above) and Magret (Patent 6,988,146).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner asserted that Ye teaches most elements of claim 22, including providing a foreign agent and establishing a forwarding tunnel. However, to the extent Ye does not explicitly teach "authenticating the mobile node" and "updating a routing table of the foreign agent," Magret supplies these missing elements. Magret describes a Simple Multicast Extension for Mobile IP that explicitly requires mobile node authentication during registration with a new foreign agent. Magret also discloses that the foreign agent must maintain and update a visitor list (a routing table) with information from the mobile node’s registration request, as required by the Mobile IP standard.
    • Motivation to Combine: A POSITA implementing Ye's Mobile IP-based handoff system would have been motivated to consult the Mobile IP standard and related art like Magret to ensure proper and secure operation. Magret teaches that authentication is a necessary part of the Mobile IP registration process to improve security. A POSITA would combine Magret's explicit authentication step with Ye’s system to yield the predictable result of a more secure handoff process, which was a well-known goal in the art.
    • Expectation of Success: The combination merely involved implementing standard features of Mobile IP (authentication and routing table updates) into a Mobile IP-based system. As both Ye and Magret operate within the known framework of Mobile IP, a POSITA would have had a high expectation of success.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, including combinations of Ye and La Porta (Patent 6,654,359) for claim 22, Ye alone for claim 23, Ye and Henry (Patent 7,441,043) for claim 24, and Gwon (Application # 2003/0104814) for claims 12 and 25.

4. Key Claim Construction Positions

  • "undesirable"/"desirable": Petitioner argued these terms should be construed relative to a signal strength threshold. A WLAN signal is "undesirable" when its strength falls below a predetermined threshold, triggering a handoff, and "desirable" when it is above a threshold. This construction was central to mapping Ye's use of signal strength thresholds to initiate handoffs.
  • "caching": In the context of "caching and replaying," Petitioner argued "caching" should be construed to mean storing a copy of information in anticipation of an indication for that information to be replayed. This supported the argument that Ye's disclosure of a foreign agent buffering packets during a pre-handoff phase met the claim limitation.
  • "home agent"/"foreign agent": Petitioner contended these terms should be construed consistent with their standard definitions in the Mobile IP protocol, as the ’917 patent provides for a Mobile IP-based implementation. This framework was used to interpret the roles of various network nodes described in the prior art.

5. Relief Requested

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