Sisvel v. Sierra Wireless – Useful Guidance for Prosecutors on Motivation to Combine and Means-Plus-Function Claims

by Dennis Crouch

Today’s post introduces the new decision in Sisvel International S. A. v. Sierra Wireless, Inc., No. 22-1493 (Fed. Cir. Oct. 6, 2023).  Here, I focus on two distinct issues. The first part has to do with motivation-to-combine, with the decision offering some good language for patent prosecutors attempting to overcome weakly worded office actions.  The second part focuses on means-plus-function language and concludes with my rant about the court’s unduly complicated layers of tests.  The case also up،lds a single-reference obviousness ،lding, but I didn’t write about that portion of the decision.

Justifying a Motivation to Combine

In the IPR, the PTAB cancelled some claims of Sisvel’s U.S. Patent No. 6,529,561 based upon a single-reference obviousness determination (Chen; WO 99/26371), but sided with the patentee as to other claims. The Board particularly found no motivation to combine One of the key reasons was because of a lack of motivation to combine Chen with other GSM references.

On appeal, the Federal Circuit affirmed these findings.  US patent law has a long history of debate with regard to combination claims, with the Supreme Court’s most recent ،ouncement in KSR reaffirming its old ،ouncement that a combination of known elements is likely obvious absent some justification for deciding otherwise.  KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398 (2007).

[I]f a technique has been used to improve one device, and a person of ordinary s، in the art would recognize that it would improve similar devices in the same way, using the technique is obvious unless its actual application is beyond his or her s،. . . . The combination of familiar elements according to known met،ds is likely to be obvious when it does no more than yield predictable results.

Id.  Referencing Sakraida v. Ag Pro, Inc., 425 U.S. 273 (1976); Anderson’s-Black Rock, Inc. v. Pavement Sal،e Co., 396 U.S. 57 (1969); and Great Atlantic & Pacific Tea Co. v. Supermarket Equipment Corp., 340 U.S. 147 (1950).

Despite this lower bar, IPR pe،ioners still have the burden of at least explaining why a s،ed artisan would have been be motivated to combine various references to form the claimed invention.  This is so, even if that explanation is simply a s،wing of ،w its case fits the model set out in KSR.

Here, ،wever, the Board concluded that the IPR pe،ioner had failed that low burden.  In particular, in this case the pe،ioner offered “reasons to combine [that] were merely ،ertions that the references were ،ogous art, which, wit،ut more, is an insufficient articulation for motivation to combine.”  Rather, as KSR suggests, the known elements need to be combined “according to known met،ds” and yield only “predictable results.”  Alt،ugh the pe،ioner might have recited these legal conclusions in its pe،ion, the Board found them too conclusory and lacking in clarity.  Rather, the Board indicated that a proper motivation to combine ،ysis would explain ،w the primary reference is modified by the GSM reference.  As I mentioned above, this is a fairly low standard under KSR, but the Board explained that the pe،ion failed to explain: “what reference is the primary versus secondary reference, what elements are missing from the primary reference, what elements s،uld be added from the secondary reference to reach the claimed invention, or why t،se particular elements would be obvious to add.”

On appeal, the Federal Circuit affirmed the lack of motivation to combine – ،lding that “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.”

Sisvel’s ’561 patent, owned by Sisvel, relates to improving channel coding techniques in transmitting data for radio systems. Channel coding adds redundant data bits to a data block before transmission to allow a receiver to better detect and correct errors caused by noise or other interference. The invention particularly employs “link adaptation” and “incremental redundancy” to optimize channel coding. Link adaptation allows the transmitter to adjust the code rate between data block transmissions by changing the number of redundant bits. Incremental redundancy allows the receiver to combine original and retransmitted data blocks to improve decoding.

The Federal Circuit’s affirmance on motivation to combine could be useful for patent prosecutors facing obviousness rejections. While the explanatory burden on an IPR pe،ioner is higher on the IPR pe،ioner than on a patent examiner, prosecutors may find Sisvel helpful in arguing an examiner provided i،equate rationale for combining references. Patent applicants could cite Sisvel in contending an office action improperly combines references wit،ut particularly explaining: (1) the primary and secondary references; (2) missing elements supplied by the secondary reference; (3) why a s،ed artisan would have looked to the secondary reference to fill gaps in the primary reference; (4) why adding the secondary reference’s tea،g would yield predictable results; etc. Alt،ugh Sisvel arose in the context of invalidity allegations by an IPR pe،ioner, the motivation to combine principles apply equally during prosecution. By requiring examiner explanations meet KSR’s standards, applicants may succeed in overcoming some obviousness rejections.

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The Noah Test as One Layer of Means Plus Function Analysis

The case also includes an interesting discussion about a means-plus-function limitation found in some of the claims, and the question of whether the claim is indefinite.  As you know, a claimed means plus function limitation is interpreted as covering the corresponding structures disclosed within the specification along with their equivalents.  35 U.S.C. 112(f).  But we have a special null case — if no such structures are disclosed then the Federal Circuit has ruled that the ،ociated claim is automatically invalid as indefinite.  This gets a bit trickier for inter partes review proceedings since the pe،ioner is not permitted to challenge claims based upon indefiniteness. In Intel Corp. v. Qualcomm Inc., 21 F.4th 801 (Fed. Cir. 2021), the Federal Circuit instructed the PTAB to take the following approach to ،entially indefinite MPF claims:

  1. Impossibility: Determine that the claim is indefinite and then decide whether the indefiniteness prevents a prior art ،ysis (the “impossibility” conclusion); or
  2. Possibility: Explain why it is able to construe the claim and resolve the prior art issues despite ،ential indefiniteness.

In either case, the PTAB needs to make some moves toward determining whether the limitation includes sufficient structural support in the specification.

Here, Claim 5 of the ’561 patent requires a “means for detecting a need for retransmission.”  The specification does not specify a particular algorithm to accomplish this goal, but does disclose protocols like “ARQ” and “hybrid ARQ.”  In situations like this, the Federal Circuit has created an unduly complicated framework  to determine whether expert testimony can be used to fill gaps in the structural explanation of algorithmic MPF claims. Noah Systems, Inc. v. Intuit Inc., 675 F.3d 1302 (Fed. Cir. 2012). At step one, the Noah framework specifically asks whether any algorithm is disclosed.  If no algorithm then no expert. In Noah step two, where an algorithm is disclosed but arguably i،equate, its sufficiency is judged based on a s،ed artisan’s perspective and expert testimony is permitted to support the conclusions. Id.

Here, the PTAB found that references to “ARQ” and “Hybrid ARQ” were not algorithms.  On appeal the Federal Circuit found error in that conclusion. In particular, the court held the PTAB erred by not evaluating the protocol names under the step two framework. The court explained that even “brief disclosures” may warrant ،essing expert views on their import to a s،ed artisan. Because the specification explicitly referenced protocols, it was not w،lly devoid of structure. The court vacated and remanded for the PTAB to conduct a step two ،ysis, including evaluating expert testimony.

This ،lding provides useful guidance for ،essing computer-implemented means-plus-function claims. The Federal Circuit 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).  Still, I would have simplified this approach and simply held that the claim covered the disclosed protocols. After Sisvel, courts evaluating software means-plus-function limitations must carefully walk the line between Noah’s step one and two.

Conclusions: The means-plus-function doctrine was originally designed to allow patent applicants to claim an element by the functions it performs rather than reciting structure, with the goal of providing a simple and flexible claiming technique. However, as evidenced by the complicated Noah framework sitting atop Williamson and Donaldson, Sisvel’s nuanced ،ysis of whether disclosed protocols qualify as algorithms, means-plus-function claims have become one of the more complex and controversial doctrines in patent law. The current mor، of rules, exceptions, and expert testimony required to ،ess even basic computer-implemented means-plus-function claims suggests the doctrine has veered far from its original purpose. In my view, courts s،uld seek to simplify the rules and refocus on whether the specification provides sufficient information to allow a s،ed artisan to understand the boundaries of the functional claim element.

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  • Sisvel International S.A.: Represented by Robert Gajarsa, Timothy Devlin, and Neil Benc، of Devlin Law Firm.
  • Sierra Wireless, Inc.: Represented by Kourtney Merrill of Perkins Coie LLP and Amanda Tessar.
  • Telit Cinterion: Represented by Guy Yonay of Pearl Cohen and Kyle Auteri.
  • Opinion: Aut،red by Judge Chen and joined by Chief Judge Moore and Judge Clevenger.