The US Court of Appeals for the Federal Circuit reiterated that in the context of construing computer-implemented means-plus-function limitations, if the specification discloses some arguable algorithm, even if a party contends that the algorithm is inadequate, the sufficiency of the purportedly-adequate structure disclosed in the specification must be evaluated in light of the knowledge possessed by a skilled artisan. Sisvel International S. A. v. Sierra Wireless, Inc., Case No. 22-1493 (Fed. Cir. Oct. 6, 2023) (Moore, Clevenger, Chen, JJ.)

Sisvel owns a patent directed to methods of channel coding when transmitting data in radio systems. The patent uses techniques called “link adaptation” and “incremental redundancy,” which are alleged to provide improvement over prior channel coding techniques. Sierra filed a petition for inter partes review (IPR) challenging certain claims as obvious over the Chen reference by itself and challenging those and other claims as obvious over the combination of the Chen and Eriksson references or the combination of the Chen and GSM references. The Patent Trial & Appeal Board found that some challenged claims were obvious based on Chen alone and that other claims were patentable over the proposed combination of references. Both parties appealed.

Sisvel appealed the Board’s unpatentability finding, arguing that Chen failed to disclose a second puncturing pattern. Sisvel also argued that the Board did not provide a sufficiently detailed explanation to support its finding that Chen disclosed the claimed “combining” limitation and ignored Sisvel’s rebuttal arguments. The Federal Circuit disagreed with Sisvel on both counts and affirmed the Board’s determination. Regarding the second puncturing pattern, the Court found that the independent claim required a “first puncturing pattern” and a “second puncturing pattern,” and that Chen expressly described that its coded transmissions are “generated by using punctured codes” and that “[p]uncturing reduces the number of code symbols to be retransmitted.” Therefore, the Court found that substantial evidence supported the Board’s finding that Chen taught a second puncturing pattern. Regarding the “combining” limitation, the Court affirmed the Board’s decision and concluded that Chen’s disclosure of “accumulating the code symbols from the transmitted and retransmitted coded data blocks,” also referred to in Chen as “interleaving,” taught the “combining” limitation. Overall, the Court determined that the Board’s analysis was sufficiently detailed, adequately addressed Sisvel’s related arguments and was supported by substantial evidence.

Sierra appealed the patentability finding, arguing that the Board’s finding that a skilled artisan would not have been motivated to combine Chen and the GSM references was not supported by substantial evidence. Sierra also argued that the Board erroneously found insufficient corresponding structure in the specification for the term “means for detecting.” The Federal Circuit concluded that substantial evidence supported the Board’s finding of a lack of motivation to combine Chen and the GSM references, but that the Board erred in analyzing the “means for detecting” limitation. Regarding motivation to combine, the Court explained that although an IPR petitioner has a low burden of explaining why a skilled artisan would have been motivated to combine various references to form [...]

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