In Sisvel International S. A. v. Sierra Wireless, Inc., No. 22-1493, — F.3d — (Fed. Cir. Oct. 6, 2023), the Federal Circuit addressed computer-implemented means-plus-function claims, and the need for clarity in articulating a motivation to combine references for obviousness.

The patent-in-suit (U.S. Pat. No. 6,529,561) was direct to methods of channel coding when transmitting data in radio systems. Channel coding is a technique that adds redundant information to a data block, thereby creating a coded data block. To account for problems from noise and interference during data transmission, the redundant data allows a receiver to more accurately detect and correct errors in the transmitted data.

In the channel coding technique of link adaptation, a data block is first coded to add redundant data bits, and then “punctured” to remove a certain number of coded data bits.

When a receiver receives a punctured, coded data block with too many errors to accurately decode, it will store that coded data block in memory and request retransmission of the data block for incremental redundancy.

Protocols for Means-Plus-Function

A means plus function claim limitation is interpreted as covering the corresponding structures disclosed within the specification along with their equivalents. 35 U.S.C. § 112(f). But if no such structures are disclosed then the claim is invalid as indefinite. Ergo Licensing, LLC v. CareFusion 303, Inc., 673 F.3d 1361, 1363 (Fed. Cir. 2012) (“If an applicant does not disclose structure for a means-plus-function term, the claim is indefinite.”).

The patent claim in Sisval recited a “means for detecting a need for retransmission.” The specification disclosed computer-implemented protocols such as Automatic Repeat Request (“ARQ”) and “hybrid ARQ.” The patentee submitted expert testimony that a skilled artisan would be familiar with “well-known and commonly used error detection codes, such as the” cyclic redundancy check (CRC) and “[ARQ] protocol and hybrid ARQ,” and “would have known from the '561 specification how to program a processor or hardware to achieve the claimed function of ‘detecting a need for retransmission of the received coded data block.'”

Noah Algorithm Framework

Under Noah Systems, Inc. v. Intuit Inc., 675 F.3d 1302, 1313 (Fed. Cir. 2012), there are two distinct groups of cases for “special purpose computer-implemented means-plus-functions claims.”

First, cases in which the specification discloses no algorithm.

Second, cases in which the specification does disclose an algorithm but a party contends that disclosure is inadequate.

Where the specification discloses no algorithm, the knowledge of a skilled artisan is irrelevant. Noah, 675 F.3d at 1313 (citing Aristocrat Techs. Austl. Pty Ltd. v. Int'l Game Tech., 521 F.3d 1328, 1337 (Fed. Cir. 2008)). In other words, no expert is required.

But where the specification discloses some arguable algorithm, even if a party contends that the algorithm is inadequate, the sufficiency of purportedly adequate structure disclosed in the specification must be evaluated in light of the knowledge possessed by a skilled artisan. Noah, 675 F.3d at 1313 (citing Aristocrat, 521 F.3d at 1337; and then AllVoice Computing PLC v. Nuance Commc'ns, Inc., 504 F.3d 1236, 1245 (Fed. Cir. 2007)). In other words, expert testimony is permitted.

The Federal Circuit held that the PTAB erred in finding that references to “ARQ” and “Hybrid ARQ” were not algorithms. Instead, those protocols should have been evaluated under the step two framework of Noah.

The Federal Circuit held that even “brief” disclosures could be adequate such that expert testimony can “shed light on” the meaning of a specification's disclosure when some actual disclosure exists in the specification. For example, the Court compared Typhoon Touch Technologies, Inc. v. Dell, Inc., 659 F.3d 1376, 1385 (Fed. Cir. 2011) (brief-but-adequately-disclosed algorithm) with Function Media L.L.C. v. Google, Inc., 708 F.3d 1310, 1319 (Fed. Cir. 2013) (no disclosure whatsoever).

Professor Crouch noted that this result “appropriately avoided rigid formalism, recognizing algorithm disclosures need not detail every step and by recognizing that reference to commercially available tools can satisfy the structural requirement of 112(f).”

Lack of Clarity in Motivation to Combine Rationales

IPR petitioners have the burden of explaining why a skilled artisan would have been be motivated to combine various references to form the claimed invention. See KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007).

The PTAB had found that each of Sierra's ten reasons for combining the references “[did] not suffice as an articulated reason with a rational underpinning to combine the respective teachings of the references.”

The Federal Circuit agreed, noting that the “proposed combinations and rationales were expressed at such a nonspecific, high level of generality, they never made clear to the Board what portions of the references were being combined and why a skilled artisan would identify those particular elements for a combination.” For example, a mere assertion that the references were “analogous art,” without more, is an insufficient articulation for motivation to combine. Also, the IPR petition did not explain what reference is the primary versus the secondary reference, what elements are missing from the primary reference, what elements should be added from the secondary reference to reach the claimed invention, or why those particular elements would be obvious to add.

Under the circumstances, we cannot fault the Board for being at a loss in trying to decipher Cross-Appellants kitchen-sink of unclear and confusing motivation-to-combine arguments.

Professor Crouch noted that patent applicants could cite Sisvel in contending an office action improperly combines references without particularly explaining: “(1) the primary and secondary references; (2) missing elements supplied by the secondary reference; (3) why a skilled artisan would have looked to the secondary reference to fill gaps in the primary reference; (4) why adding the secondary reference's teaching would yield predictable results; etc.”

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