by Dennis Crouch
In this case, the Federal Circuit has vacated and remanded, holding that the PTAB (1) improperly construed the claims and (2) abused its discretion by relying on testimony from an expert witness who did not meet the Board’s defined standard for ordinary skill in the art. Both of these holdings will be housed within patent law’s extensive closet full of “tricks-and-traps” for the unwary.
Sisvel’s US7869396 involves data retransmission in wireless communication –particularly claiming a variation of automatic repeat request (ARQ). The improved method has the message receiver start a timer as soon as it notices that a data package is missing. It will only report the failure back to the transmitter if the timer expires before the missing PDU is received. This approach improves efficiency by reducing unnecessary retransmission requests, reporting missing data only when genuinely needed.
Sierra Wireless, Honeywell International, and Telit Cinterion Deutschland (collectively, “Appellants”) successfully petitioned for IPR, with the PTAB ultimately splitting its decision: Finding claims 1, 2, and 6-8 unpatentable as anticipated by and obvious in view of International Patent Application Publication No. WO 02/091659 (“Sachs”), but finding claims 3-5, 9, and 10 not unpatentable. Both sides appealed appealed.
Conditional Element and Method Claims: The Federal Circuit first addressed Sisvel’s cross-appeal regarding claims 1, 2, and 6-8. The court found that the Board erroneously construed two of the limitations of claim 1 as conditional rather than required elements. Here is the particular claim language, with the underlying portions of steps [c] and [d] at issue in the appeal:
1. A method of performing automatic repeat request (ARQ) in a wireless communication system, the method performed by a receiver and comprising:
[a] detecting whether at least one data block to be received from a transmitter is missed;
[b] starting a timer when the at least one data block is detected as missed;
[c] stopping the timer when the at least one data block is received from the transmitter while the timer is running, in order to prevent a triggering of a status report before the timer expires; and
[d] transmitting the status report to the transmitter after the timer expires, wherein the status report comprises a positive acknowledgement indicating receipt of at least one received data block.
You’ll notice here that [c] and [d] are not going to both happen – if the timer is stopped at [c], then it will never expire as required by [d]. The PTAB resolved this internal conflict by recognizing that these are conditional elements – either one or the other. And, the PTAB went on to conclude that the prior art anticipates if it performs either branch of the method. But on appeal the Federal Circuit rejected this reasoning, holding that “the plain and unambiguous language of claim 1 requires that a method, to come within the claim, must perform both limitations 1[c] and 1[d] where their preconditions apply.”
The court explained that while limitations 1[c] and 1[d] might not both occur in response to the same set of stimuli (since the timer either stops upon receipt of the missing PDU or expires without having received it), the claim language clearly requires both capabilities in the claimed method.
The court’s implicit definition of a “method” is important. For the court, a claimed “method” or “process” allows for a fully branched process flow, encompassing alternative operational pathways triggered by conditional events. This interpretation emphasizes that a patented method must encompass all expressly stated conditional branches, ensuring that the method covers a full scope of potential operational scenarios. For infringement purposes, this means the accused method would need to have functionality for every conditional step recited in the claims. Likewise, to establish anticipation, prior art references must also disclose each conditional path of the claimed method, not merely one of several alternatives.
The patentee was fortunate with this outcome, as the claim language does not explicitly clarify whether [c] and [d] were intended to be complementary. The Federal Circuit could have instead interpreted the claim as requiring that both steps occur within a single execution of the method, which would have rendered the claim internally inconsistent and at least uninfringeable. Instead, the court’s reading preserves the claim’s validity and its potential for being infringed.
Expert Witness Qualification Requirements: The Federal Circuit also addressed the Appellants’ argument that the PTAB abused its discretion by relying on the testimony of Sisvel’s expert, Mr. Regis (“Bud”) Bates, who did not meet the Board’s own definition of a person of ordinary skill in the art. Mr. Bates has been doing telecom work for the past 50 years, including authoring a dozen books about packet switching communication systems. BUT, the PTAB defined PHOSITA as someone with “a degree in electrical engineering or a similar discipline, with at least three years of relevant industry or research experience, including experience designing or implementing wireless radio systems for data transmission and retransmission.” Mr. Bates lacks an EE degree and, although he has done extensive consulting work, he has not been focused the design side. Citing Kyocera Senco Indus. Tools Inc. v. Int’l Trade Comm’n, 22 F.4th 1369, 1376-77 (Fed. Cir. 2022), the court emphasized that “to offer expert testimony from the perspective of a skilled artisan in a patent case—like for claim construction, validity, or infringement—a witness must at least have ordinary skill in the art.” As a consequence, the Board abused its discretion — especially because it failed to provide any reasoning for its decision to credit Mr. Bates’ testimony despite his lack of qualifications under the Board’s own definition.
On remand, the PTAB will need to apply the new claim construction — likely finding additional claims are valid. In addition, the PTAB will review its consideration of Mr. Bates – either justifying its reliance on his testimony or else rejecting the testimony. If it does reject the testimony, that may tank the entire case for the patentee.
Perkins Coie attorney Kourtney Mueller Merrill argued for the patent challenger appellants; Robert Gajarsa (Devlin Law) argued for cross-appellant patentee. Chief Judge Moore authored the opinion, joined by Judges Schall and Taranto.