TAKEAWAY: Referencing a software protocol name may be sufficient structure for means-plus-function algorithm claim limitations.

Means-plus-function limitations in claims recite a function without structure for performing that function in the claim itself. Rather, 35 U.S.C. 112(f) permits means-plus-function claim limitations to be interpreted in view of corresponding structure described in the specification of the patent. Such claims run afoul of the requirements of Section 112 if the specification lack sufficient structure for performing the claimed function.

The question of sufficient structure in a patent specification was discussed in the Federal Circuit case Sisvel Int’l S.A. v. Sierra Wireless. et al. (Oct. 6, 2023). In this case, the Court considered the limitation, “means for detecting a need for retransmission of [a] received coded data block” recited in claim 5 of Sisvel’s U.S. Patent No. 6,529,561.

The USPTO Patent Trial and Appeal Board had determined there was insufficient algorithmic structure in the patent specification to determine the structure encompassed by the claim. The Board acknowledged that the “means for detecting” term corresponded to various protocols mentioned in the ‘561 patent but concluded that the specification itself did not contain an algorithm for performing any of the protocols. The Board further disregarded expert testimony provided as evidence that a skilled artisan would be familiar with “well-known and commonly used error detection codes” such as those described in the specification.

On appeal, the Federal Circuit disagreed with the Board’s conclusion and found that the specification disclosed some arguable algorithm. The Court held that reference to the software protocols required that the specification be evaluated in light of the knowledge of a skilled artisan and that the Board erred in not considering the expert testimony. The case was remanded to the Board on the question of the “means for detecting” limitation in the ’561 patent.

Sisvel Int’l may provide some clarity on how means-plus-function limitations are interpreted by courts. When using these types of claim limitations, patent practitioners should carefully consider the structural description provided in the specification and whether it may be appropriate to refer to software protocols (and which ones) for a claimed algorithm.