United States Court of Appeals 

for the Federal Circuit ______________________ 

ZYXEL COMMUNICATIONS CORP.,

Appellant

v.

UNM RAINFOREST INNOVATIONS,

Cross-Appellant

______________________ 

2022-2220, 2022-2250

______________________ 

Appeals from the United States Patent and Trademark 

Office, Patent Trial and Appeal Board in Nos. IPR2021-

00375, IPR2021-00734.

______________________ 

Decided: July 22, 2024 

______________________ 

JONATHAN IAIN MAX DETRIXHE, Reed Smith LLP, San 

Francisco, CA, argued for appellant. Also represented by 

PETER J. CHASSMAN, MICHAEL JOHN FORBES, Houston, TX.

 JAY P. KESAN, DiMuroGinsberg, P.C., Tysons Corner, 

VA, argued for cross-appellant. Also represented by CECIL 

E. KEY; HENNING SCHMIDT, Stradling Yocca Carlson & 

Rauth LLP, Austin, TX; MICHAEL W. SHORE, The Shore 

Firm, Dallas, TX.

______________________ 

Before DYK, PROST, and STARK, Circuit Judges.

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DYK, Circuit Judge.

In this inter partes review proceeding, the Patent Trial 

and Appeal Board (the “Board”) found claims 1–4, 6, and 7 

of U.S. Patent No. 8,265,096 (the “’096 patent”) unpatentable as obvious but declined to find claim 8 of the ’096 patent 

unpatentable as obvious. The Board also granted patentee 

UNM Rainforest Innovations’s (“UNMRI”) motion to 

amend, canceling claims 1–4, 6, and 7 and substituting in 

claims 44–47, 49, and 50. 

Petitioner ZyXEL Communications Corp. (“ZyXEL”)

appeals the Board’s determination that claim 8 was not obvious and the Board’s decision granting UNMRI’s motion 

to amend. UNMRI cross-appeals the Board’s determination that claims 1–4, 6, and 7 are unpatentable as obvious. 

We affirm the Board’s determination that claims 1–4, 

6, and 7 are unpatentable as obvious, but reverse the 

Board’s determination that claim 8 is not obvious. We affirm the Board’s decision to grant UNMRI’s motion to 

amend. However, we remand to the Board to determine if 

the substitute claims are unpatentable as obvious under 

collateral estoppel based on our holding that claims 1–4 

and 6–8 are unpatentable as obvious. We also remand to 

the Board for it to consider whether to exercise its discretion to evaluate if the substitute claims are unpatentable 

as obvious on a new ground. Thus, as to the main appeal, 

we affirm-in-part, reverse-in-part, and remand-in-part, 

and we affirm as to the cross-appeal. 

BACKGROUND

I 

UNMRI owns the ’096 patent, entitled “Method for 

Constructing Frame Structures.” J.A. 1733. The patent 

relates to methods for constructing frame structures (i.e., 

the organization of information transmitted across time 

and frequency) in orthogonal frequency-division multiple 

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access (OFDMA) systems. OFDMA “is a multiple access 

scheme for transmitting data in different subcarriers in a 

channel, wherein the data may come from different users 

and may be transmitted in disjoint subsets of sub-channels 

in a transmission bandwidth.” J.A. 1740, col. 1, ll. 21–24. 

“The orthogonality property among the subcarriers may allow simultaneous transmission of data from different users 

without interference from one [an]other.” Id., col. 1, ll. 24–

27. 

The patent describes a method for constructing a frame 

structure with two sections, each of which is configured for 

a different communication system, where the second communication system is used to support high mobility users

(i.e., faster moving users). The advantage of using this type 

of frame structure is that it can support both an older 

OFDMA system for slower moving users and a newer 

OFDMA system for faster moving users, (i.e., it uses newer 

OFDMA systems while also being compatible with older 

systems). 

The ’096 patent provides an example where the frame 

structure employs the older IEEE standard 802.16(e) system1 as the first communication system and the newer 

IEEE standard 802.16(m) system as the second communication system. See, e.g., J.A. 1740, col. 1, ll. 27–35; J.A. 

1741, col. 4, ll. 25–27. The IEEE standard 802.16(m) 

1 The IEEE standard 802.16 protocols are a set of 

wireless broadband standards developed by the Institute of 

Electrical and Electronics Engineers. The 802.16(e) protocol “aims to enhance the specifications to the 802.16 standard to support both fixed and mobile subscriber stations to 

accommodate, for example, subscriber stations moving at 

vehicular speeds.” J.A. 2383, ¶ 1. The 802.16(m) protocol 

is newer and provides enhanced spectrum efficiency and 

higher speed tolerance, among other things. 

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system better supports higher mobility users. The ’096 patent also discloses that the placement of pilot symbols (i.e.,

non-data symbols sent at known intervals to help correct

for changing channel conditions) can be transmitted more 

frequently and/or placed at higher density in the second 

communication system than the first system in order to increase the accuracy of channel estimation (a method to use 

known transmitted signals to calculate the effect of the 

wireless channel conditions on the signal). Symbol period 

refers to the amount of time between the transmission of 

successive pilot symbols. Symbol density refers to the 

number of pilot symbols transmitted during a particular 

time period across all sub-carriers. 

Independent claims 1 and 8 of the ’096 patent are at 

issue in this appeal: 

1. A method of constructing a frame structure for 

data transmission, the method comprising: 

generating a first section comprising data 

configured in a first format compatible with 

a first communication system using symbols; 

generating a second section following the 

first section, the second section comprising 

data configured in a second format compatible with a second communication system 

using symbols, wherein the first communication system’s symbols and the second 

communication system’s symbols co-exist 

in one transmission scheme and wherein: 

the second format is compatible 

with the second communication 

system configured to support 

higher mobility than the first communication system, wherein each 

symbol in the second 

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communication system has a 

shorter symbol period than that in 

the first communication system; 

generating at least one non-data section 

containing information describing an aspect of data in at least one of the first section and the second section; and 

combining the first section, the second section and the at least one non-data section 

to form the frame structure.

8. A method of constructing a frame structure for 

data transmission, the method comprising: 

generating a first section comprising data 

configured in a first format compatible with 

a first communication system using symbols; 

generating a second section following the 

first section, the second section comprising 

data configured in a second format compatible with a second communication system 

using symbols, wherein the first communication system’s symbols and the second 

communication system’s symbols co-exist 

in one transmission scheme and wherein 

the second communication system has pilot 

symbols that are denser than those in the 

first communication system; 

generating at least one non-data section 

containing information describing an aspect of data in at least one of the first section and the second section; and 

combining the first section, the second section and the at least one non-data section 

to form the frame structure.

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J.A. 1743, col. 8, ll. 32–54 (emphasis added); J.A. 1744, col. 

9, ll. 6–25 (emphasis added). 

II

Qualcomm Inc. (“Qualcomm”) filed a petition for inter 

partes review as to claims 1–4 and 6–8 of the ’096 patent

contending that they are unpatentable as obvious. The 

Board instituted review for all the challenged claims

(IPR2021-00375). ZyXEL also filed a petition for inter 

partes review (IPR2021-00734) raising the same arguments as to the same claims. The Board granted ZyXEL’s

motion for joinder, joining it as a petitioner in the IPR2021-

00375. 

Qualcomm appears to have settled with UNMRI. 

ZyXel is the only petitioner who has appealed the Board’s 

final written decision or defended the Board’s decisions 

that are adverse to UNMRI. Because Qualcomm and 

ZyXEL raised the same arguments in their petitions, we 

will refer to ZyXEL as “petitioner.”

Before the Board, ZyXEL argued that claims 1–4, 6, 

and 7 were unpatentable as obvious over a combination of 

U.S. Publication No. 2009/0067377 (“Talukdar”) and U.S. 

Publication No. 2007/0155387 (“Li”). The Board found 

claims 1–4, 6, and 7 to be unpatentable as obvious over Talukdar and Li. The Board determined that a person of ordinary skill in the art (“POSA”) would apply the teachings 

of Li to Talukdar in order to achieve the same benefits described in Li. 

ZyXEL also argued that claim 8 was unpatentable as 

obvious over a combination of Talukdar and U.S. Publication No. 2007/0104174 (“Nystrom”). The Board declined to 

find claim 8 unpatentable as obvious over Talukdar and 

Nystrom, finding that ZyXEL had not shown that a POSA

would have been motivated to combine the two prior art 

references. 

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On cross-appeal, UNMRI contends that during the proceedings the Board improperly admitted and relied upon 

the testimony of ZyXEL’s expert, Dr. Roy, to support its 

findings of unpatentability of claims 1–4, 6, and 7. On December 6, 2021, UNMRI took the deposition of Dr. Roy. On 

December 16, 2021, UNMRI filed a motion to exclude Dr. 

Roy’s expert report arguing that Dr. Roy adopted the expert report of another, Dr. Akl, as his own and gave false 

testimony as to his role as expert. UNMRI argued that this 

violated Federal Rules of Evidence 702(d), which requires 

an “expert’s opinion reflect[] a reliable application of the 

principles and methods to the facts of the case,” and Federal Rules of Evidence 703, which states an “expert may 

base an opinion on facts or data in the case that the expert 

has been made aware of or personally observed,” because 

Dr. Roy’s report was the work of another, and he failed to 

perform the analysis himself. FED. R. EVID. 702, 703. The 

Board denied the motion as untimely, but also found that 

it would have denied the motion had it considered the merits. J.A. 12–13. 

III 

During the course of the proceedings, UNMRI filed a 

contingent motion to amend. See 35 U.S.C. § 316(d)(1). In 

that motion, UNMRI requested that, if claims 1–4, 6, and 

7 were found to be unpatentable, those claims be canceled 

and that claims 44–47, 49, and 50 be substituted in their

stead. As part of its motion, UNMRI requested preliminary guidance from the Board regarding UNMRI’s motion 

to amend, pursuant to the Board’s “MTA Pilot Program.” 

See generally Notice Regarding a New Pilot Program Concerning Motion to Amend Practice and Procedures in Trial 

Proceedings under the America Invents Act Before the Patent Trial and Appeal Board (“MTA Pilot Program Notice”), 

84 Fed. Reg. 9497 (Mar. 15, 2019). 

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The MTA Pilot Program “provide[s] an improved 

amendment practice in AIA trials in a manner that is fair 

and balanced for all parties and stakeholders.” Id. at 9499

(internal quotations and citation omitted). Under the program, patent owners may request preliminary guidance 

from the Board as to whether the motion meets statutory 

and regulatory requirements. Id. at 9497. This mechanism provides useful information to the parties and allows 

issues with the motion to be addressed. 

Independent claim 44 is representative of the proposed 

substitute claims (with underscoring to distinguish differences from claim 1): 

44. A method of constructing a frame structure for 

data transmission, the method comprising: 

generating a first section comprising data 

configured in a first format compatible with 

a first communication system using symbols; 

generating a second section following the 

first section, the second section comprising 

data configured in a second format compatible with a second communication system 

using symbols, wherein the first communication system’s symbols and the second 

communication system’s symbols co-exist 

in one transmission scheme and wherein: 

the second format is compatible 

with the second communication 

system configured to support 

higher mobility than the first communication system, 

wherein each symbol in the second 

communication system has a 

shorter symbol period than that in 

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the first communication system; 

and 

wherein the second communication 

system has pilot symbols that are 

denser than those in the first communication system; 

generating at least one non-data section 

containing information describing an aspect of data in at least one of the first section and the second section; and combining 

the first section, the second section and the 

at least one [non-data] section to form the 

frame structure.

J.A. 67. 

In its opposition to UNMRI’s motion to amend, ZyXEL 

argued, inter alia, that UNMRI’s motion was deficient because it failed to show written description support for all of 

the claim limitations in the proposed substitute claims as 

required by the regulations. See 37 C.F.R. § 42.121(a)–(b). 

ZyXEL contended that UNMRI’s motion only showed support for the newly added limitations, instead of showing 

support for the proposed substitute claim as a whole. 

In its preliminary guidance, which is not binding on the 

Board, MTA Pilot Program Notice, 84 Fed. Reg. at 9500, 

the Board “agree[d] with [ZyXEL]’s contentions that ‘Patent Owner only purport[ed] to show support for the additional features added by the amendments,’ and that ‘Patent 

Owner has not even attempted to show support in the original disclosure for any other limitations of the proposed 

substitute claims.’” J.A. 940 (citations omitted). The Board 

also noted that “it appear[ed] more likely than not that 

there is adequate written description support for the proposed substitute claims . . . in the Specification, as filed, of 

U.S. Patent Application 12/168,855” (the “’855 Application”), which issued as the ’096 patent. J.A. 940–41. 

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In response to the Board’s preliminary guidance, 

UNMRI filed a revised motion to amend. In its revised motion, UNMRI proposed the same substitute claims, but supplemented the written description support for the preexisting claim limitations by citing to the ’855 Application. 

ZyXEL opposed. 

The Board rejected UNMRI’s revised motion (and 

ZyXEL’s opposition to it) because it did not include any new

substitute claims that were not already present in the original motion to amend as required by the regulations. See 

MTA Pilot Program Notice, 84 Fed. Reg. at 9499 (“A revised 

[motion to amend] includes one or more new proposed substitute claims in place of previously presented substitute 

claims to address issues identified in the preliminary guidance and/or the petitioner’s opposition.”). 

However, the Board permitted UNMRI to file a reply

in support of its original motion to amend, which the Board 

required to be “substantively identical” to UNMRI’s rejected revised motion to amend. Qualcomm Inc. v. UNM 

Rainforest Innov., Case IPR2021-00375, Paper No. 63 at 5 

(PTAB May 19, 2022). The Board waived the usual page

limit requirement for replies and permitted UNMRI’s reply 

to be 25 pages. Likewise, the Board waived the page limit 

requirement for ZyXEL’s sur-reply and authorized it to file 

a 25-page sur-reply. In its reply, UNMRI included written 

description support for the remaining claim limitations by 

citing to the ’855 Application.2 ZyXEL filed a sur-reply

2 ZyXEL argues that the Board erred in granting the 

motion to amend because UNMRI did not show written description support to U.S. Provisional App. No. 60/929,798

(the “’798 Application”). UNMRI had originally sought a 

priority date for its application going back to the ’798 Application. By the time of the motion to amend, it had 

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arguing the procedural point but not disputing that there 

was sufficient written description support in the ’855 Application for all the limitations in the substitute claims. 

ZyXEL also reiterated its argument that the proposed substitute claims were unpatentable as obvious over the combination of Talukdar and Li. 

The Board granted UNMRI’s motion to amend, substituting claims 44–47, 49, and 50, and determined those 

claims to be nonobvious over Talukdar and Li (rejecting 

ZyXEL’s argument as to obviousness). Specifically, the 

Board found the limitation “wherein the second communication system has pilot symbols that are denser than those 

in the first communication system” (similar to claim 8), 

which was not present in the original claims, was neither 

disclosed nor taught by the combination of Talukdar and 

Li. 

ZyXEL appeals the Board’s decision to grant UNMRI’s 

motion to amend and the Board’s decision finding claim 8 

nonobvious over Talukdar and Li. UNMRI cross-appeals 

the Board’s finding that claims 1–4, 6, and 7 are unpatentable as obvious over Talukdar and Li.

We have jurisdiction under 28 U.S.C. § 1295(a)(4)(A). 

abandoned that contention. There was no need under 

these circumstances to provide written description support 

to the ’798 Application. See 37 C.F.R. § 42.121(b) (“A motion to amend claims must . . . set forth: . . . (2) The support in an earlier-filed disclosure for each claim for which 

benefit of the filing date of the earlier filed disclosure is 

sought.”). 

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DISCUSSION

I. Obviousness of Claims 1–4, 6, and 7

A. Dr. Roy’s Testimony

UNMRI contends that the Board’s finding that claims 

1–4, 6, and 7 are unpatentable as obvious should be set 

aside because the Board erroneously refused to exclude, 

and relied on, Dr. Roy’s expert testimony (his expert report)

on obviousness. In moving to exclude Dr. Roy’s expert report, UNMRI argued that Dr. Roy’s report was actually an 

expert report prepared by another expert, Dr. Akl, in an 

earlier proceeding and that Dr. Roy “simply signed his 

name to” it. Cross-Appellant Opening Br. 59. UNMRI argued that Dr. Roy did not disclose that Dr. Akl’s report was 

the basis for his report until he was asked about it during 

his deposition. UNMRI also contended that Dr. Roy misrepresented under oath the contributions he made to the 

report. Specifically, UNMRI cited to Dr. Roy’s deposition 

testimony where he stated that he contributed (i.e., provided corrections and edits) to various sections of the expert report. UNMRI argued that the differences between 

Dr. Akl’s report and Dr. Roy’s report were de minimis, and 

thus Dr. Roy misrepresented his contributions to the report. 

The Board first denied UNMRI’s motion as untimely. 

Under 37 C.F.R. § 42.64(b)(1), the Board’s regulations provide:

Any objection to evidence submitted during a preliminary proceeding must be filed within ten business days of the institution of the trial. Once a trial 

has been instituted, any objection must be filed 

within five business days of service of evidence to 

which the objection is directed. 

Dr. Roy’s expert report was submitted with the petition, and trial was instituted (began) on July 19, 2021. The 

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Board concluded that the objection to Dr. Roy’s expert report, filed on December 16, 2021, was untimely because it 

was not filed within 10 business days of the institution of

trial. 

UNMRI contended that it only became aware of Dr. 

Roy’s alleged misrepresentation on December 6, 2021, the 

date of his deposition, and therefore could not object earlier. The Board, however, found that even if the first sentence of the rule was inapplicable, under the second 

sentence of the regulation, the filing was still untimely because UNMRI was objecting to evidence presented during 

trial and UNMRI filed its objection eight business days after the deposition date, while the regulation requires any 

objection to be filed within five business days of service of 

the evidence. 

“Decisions related to compliance with the Board’s procedures are reviewed for an abuse of discretion.” Intelligent Bio-Sys., Inc. v. Illumina Cambridge Ltd., 821 F.3d 

1359, 1367 (Fed. Cir. 2016) (citing Bilstad v. Wakalopulos, 

386 F.3d 1116, 1121 (Fed. Cir. 2004)). We see no abuse in 

discretion by the Board’s interpretation of its own rules to 

require a filing within five business days of service of evidence to which the objection is directed. 

The Board also concluded that it would have denied the 

motion on the merits even if it had been timely because it 

viewed UNMRI’s challenges to Dr. Roy’s testimony as going to the weight that should be given to his testimony, not 

its admissibility. We conclude that the Board did not err 

in concluding that the objection did not merit exclusion of 

the report even if the objection had been timely. We see no 

abuse of discretion by the Board in determining that the 

issues with Dr. Roy’s report go to the credibility and weight 

attributed to the report and not to its admissibility. Unlike 

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the cases UNMRI relies on,3 there was evidence here that 

Dr. Roy analyzed the prior art references, the patent, and 

Dr. Akl’s expert report, and reached the same conclusions 

as Dr. Akl. While Dr. Roy may have overstated his contributions in revising Dr. Akl’s report, he admitted that Dr. 

Akl’s report served as the basis for his report and stated 

that his own report reflected his own opinion, and the 

Board was free to accept the report and to consider any erroneous testimony by Dr. Roy in deciding to attribute 

weight to his testimony. 

B. Substantial Evidence for the Board’s Findings

“In reviewing the Board’s determination on the question of obviousness, we review the Board’s legal conclusions 

de novo and its factual findings for substantial evidence.” 

Becton, Dickinson & Co. v. Baxter Corp. Englewood, 998 

3 In all of the cases on which UNMRI relies, an expert’s testimony was excluded because the expert did not 

actually perform the analysis or falsified the content of the 

analysis. See, e.g., Rembrandt Vision Techs., L.P. v. Johnson & Johnson Vision Care, Inc., 818 F.3d 1320, 1325 (Fed. 

Cir. 2016) (ordering a new trial when expert falsely testified about his involvement and experience, withheld documents, and withheld contradictory test results); Puppolo v. 

Welch, 771 F. App’x 64, 65 (2d Cir. 2019) (finding no abuse 

of discretion by the district court excluding expert’s testimony when the expert acknowledged “he performed none 

of the legal research”); United States v. Tomasian, 784 F.2d 

782, 786 (7th Cir. 1986) (excluding expert opinion where 

the expert “had no opinion of his own” and “could only relay 

another’s opinion”); Crowley v. Chait, 322 F. Supp. 2d 530, 

554 (D.N.J. 2004) (precluding expert from testifying when 

it constituted “simply summariz[ing] the facts and the depositions of others,” but declining to exclude expert testimony in its entirety). 

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F.3d 1337, 1339 (Fed. Cir. 2021) (internal quotation marks, 

citation, and alterations omitted). “What a reference 

teaches and the differences between the claimed invention 

and the prior art are questions of fact which we review for 

substantial evidence.” In re Cuozzo Speed Techs., LLC, 793 

F.3d 1268, 1280 (Fed. Cir. 2015). 

UNMRI contends that a POSA would not know how to 

combine Talukdar and Li in order to render obvious the 

limitation “wherein each symbol in the second communication system has a shorter symbol period than that in the 

first communication system.” J.A. 1743, col. 8, ll. 47–49. 

We conclude that the Board’s decision is supported by substantial evidence. 

Talukdar discloses a frame structure that includes first 

and second sections, each corresponding to a first and second communication system. See, e.g., J.A. 38–40; 2131–32, 

¶¶ 27–30. Talukdar discloses using the IEEE standard 

802.16(e) system as an older legacy system and the IEEE 

standard 802.16(m) as a newer system, which are the same 

systems used in the ’096 patent. Li in the context of a legacy system teaches “using shorter symbol periods for faster 

moving remote units.” Cross-Appellant Opening Br. 53; see 

also J.A. 2386, ¶ 37. UNMRI does not dispute any of these 

facts. 

The Board determined that it would have been obvious 

to apply Li’s teachings to the second communication system 

in Talukdar (i.e., the newer system) because “it would improve Talukdar’s method in the same way as Li by reducing 

inter-subcarrier interference experienced by the faster 

moving mobile remote users.” J.A. 48. The Board’s conclusion is supported by substantial evidence. Li teaches that 

using shorter pilot symbol periods for faster mobile users 

has the benefit of reducing inter-subcarrier interference 

that faster mobile users may experience. Faster mobile users would be using the second communication system in 

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Talukdar (the 802.16(m) system), the same system in the 

’096 patent. Dr. Roy’s expert report supports the argument 

that it would be obvious to a POSA to apply Li’s teachings 

to the second system in Talukdar.4 This is substantial evidence that supports the Board’s obviousness determination. 

Therefore, we affirm the Board’s decision finding 

claims 1–4, 6 and 7 unpatentable as obvious over Talukdar 

and Li. 

II. Obviousness of Claim 8

ZyXEL argues that the Board erred in finding that 

claim 8 was not obvious because there was no motivation 

to combine Talukdar and Nystrom. As the Board noted, 

claim 8 is nearly identical to claim 1, except that claim 8 

recites “wherein the second communication system has pilot symbols that are denser than those in the first communication system,” in place of claim 1’s recitation of “wherein 

each symbol in the second communication system has a 

shorter symbol period than that in the first communication 

system.” J.A. 55. The difference between these two limitations is subtle, as noted earlier. Symbol period refers to 

the amount of time between the transmission of pilot symbols, whereas symbol density refers to the number of pilot 

symbols transmitted during a particular time period. 

Before the Board, ZyXEL argued a POSA would have 

been motivated to combine Talukdar and Nystrom to 

achieve the pilot density limitation. ZyXEL contended a 

4 On appeal, UNMRI argues that there is no evidentiary support for a motivation to combine. We disagree as 

the Board pointed to Li, Talukdar, and Dr. Roy’s testimony

for support that Li would improve Talukdar’s method in 

the same way as in Li. Thus, there is substantial evidence 

for the Board’s finding of a motivation to combine. 

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POSA would be motivated to apply the teachings in Nystrom about using denser pilot symbols to improve Talukdar 

because Nystrom teaches that denser pilot symbols (1) 

counteract the effects of Doppler shift and fading experienced by faster-moving remote units and (2) enhance a 

faster-moving unit’s ability to perform channel estimation. 

It is undisputed that the limitation pertaining to symbol density is present in Nystrom. The Board found that 

“Nystrom discloses that it is beneficial to assign resources 

for mobile stations with certain fast varying channel or 

Doppler conditions in the dense parts of the pilot pattern 

and users with more slowly varying conditions in the less 

dense parts.” J.A. 54–55. The Board, however, found that 

Nystrom did not teach that higher density pilot symbols 

are used to counteract high doppler conditions or improve 

channel estimation. We disagree. The Board’s determination is not supported by substantial evidence, and the record supports only a conclusion of obviousness.5 

5 UNMRI argues that the Board found ZyXEL’s arguments about claim 8 to be forfeited and ZyXEL has not 

challenged the Board’s finding of waiver. Cross-Appellant 

Opening Br. 17, 21. It is true that the Board found ZyXEL 

had forfeited certain arguments by only raising them in its 

reply brief. J.A. 60, 63–64. However, the Board did not 

find ZyXEL to have waived all arguments regarding claim 

8. J.A. 55–58 (citing petition and discussing non-forfeited 

arguments). It is these original arguments that ZyXEL 

raises on appeal. UNMRI indeed concedes that these arguments were not forfeited as the heading for its discussion 

of these issues is titled “ZyXEL’s Original Motivation To 

Combine Arguments Are Unsupported.” Cross-Appellant 

Opening Br. 22. These issues were not forfeited and are 

properly before us here on appeal. 

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Nystrom extensively teaches that denser pilot symbols 

should be used in situations when users encounter large 

Doppler shifts, such as moving at high velocity. Nystrom 

recognizes that “different users travel at different speeds 

and thus experience different Doppler shifts.” J.A. 2401, 

¶ 4. Recognizing users may face different conditions, Nystrom discloses that different pilot symbol patterns (i.e., different densities) can be used to accommodate these 

different conditions. For example, in Figure 5A, reproduced below, Nystrom discloses four different combinations 

of pilot symbol densities varied in frequency and time: 

J.A. 2394. In describing Fig. 5A, Nystrom explains how 

these different pilot symbol densities should be used for different conditions, including higher density pilot symbols 

for higher Doppler conditions and lower pilot symbol densities for lower Doppler conditions. See, e.g., J.A. 2404, 

¶ 42. Nystrom further teaches “[i]t is beneficial, e.g. to assign resources for mobiles with certain fast varying channel or Doppler conditions in the dense parts of the pilot 

pattern and uses with more slowly varying conditions in 

the less dense parts.” J.A. 2404, ¶ 43. Thus, Nystrom 

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plainly teaches that it is beneficial to use higher pilot symbol densities for higher Doppler conditions. 

While Nystrom may not explicitly state that denser pilot 

symbols counteract the effect of high Doppler shifts or improve channel estimation, this is not necessary to show obviousness. A prior art reference does not need to explicitly 

articulate or express why its teachings are beneficial so 

long as its teachings are beneficial and a POSA would recognize that their application was beneficial. Intel Corp. v. 

PACT XPP Schweiz AG, 61 F.4th 1373, 1380–81 (Fed. Cir. 

2023) (“There is a motivation to combine when a known 

technique ‘has been used to improve one device, and a person of ordinary skill in the art would recognize that it 

would improve similar devices in the same way,’ using the 

‘prior art elements according to their established functions.’” (first quoting KSR Int’l Co. v. Teleflex Inc., 550 U.S. 

398, 417 (2007); and then quoting Intel Corp. v. Qualcomm 

Inc., 21 F.4th 784, 800 (Fed. Cir. 2021)). Here, Nystrom 

discloses that it is beneficial to use denser pilot symbol patterns for higher Doppler conditions, conditions common to 

high mobility users. Indeed, UNMRI seems to concede this 

point as, on appeal, it characterized Nystrom as “disclos[ing] the use of denser pilots for high mobility users: 

Users with ‘radio conditions demanding a high density of 

pilots’—such as fast-moving users—could be allocated resource space with increased pilot density in the time dimension, frequency dimension, or both.” Cross-Appellant 

Opening Br. 16 (quoting J.A. 2404, ¶ 43). Furthermore, Dr. 

Roy testified that a POSA would have been motivated to 

combine Nystrom and Talukdar and cited to these portions 

of Nystrom for support. See J.A. 1854–56. 

There is no contrary evidence. While UNMRI’s expert, 

Dr. Vojcic, opined that a POSA would not be motivated to 

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combine Talukdar and Nystrom,6 his opinion offers no support for the Board’s reasoning and is not relevant to 

whether Nystrom discloses that high pilot symbol densities 

are beneficial for high Doppler shifts. Indeed, Dr. Vojcic 

acknowledged that Nystrom discloses using a higher density of pilot symbols in the time dimension for users moving 

at higher speeds, and that such users may encounter 

higher Doppler shifts. Dr. Vojcic stated “[a] POS[A] would 

also understand that small/larger Doppler spread (or 

equivalently velocity) corresponds to low/high time selectivity, requiring low/high pilot density over time.” J.A. 

3028. Dr. Vojcic does not state or opine that a POSA would 

not recognize the benefits of using higher pilot symbol densities for faster mobile users who experience high Doppler 

conditions. 

The Board’s conclusion as to claim 8 lacks substantial 

evidence. We determine that claim 8 is unpatentable as 

obvious and reverse the Board’s contrary decision. 

III. Substitute Claims 

A. Motion to Amend

ZyXEL argues that the Board erred in granting 

UNMRI’s motion to amend because UNMRI did not satisfy 

the requirement that the motion itself contain written description support for all of the claim limitations of the 

6 On appeal, UNMRI suggests that the Board 

adopted Dr. Vojcic’s testimony that “a significant non-obvious redesign of the Talukdar system would be required to 

incorporate Nystrom’s disclosure” and that the two would 

otherwise be incompatible with each other. Cross-Appellant Opening Br. 29. The Board did not find that applying 

Nystrom’s teachings to Talukdar would require such a redesign and made no reference to these portions of Dr. 

Vojcic’s report. 

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substitute claims. See 37 C.F.R. § 42.121(b) (“A motion to 

amend claims must include a claim listing . . . and set 

forth: (1) The support in the original disclosure of the patent for each claim that is added or amended; and (2) The 

support in an earlier-filed disclosure for each claim for 

which benefit of the filing date of the earlier filed disclosure 

is sought.”); Lectrosonics, Inc. v. Zaxcom, Inc., IPR2018-

01129, Paper 15 at 8 (PTAB Feb. 25, 2019) (“In addition, 

the motion must set forth written description support for 

each proposed substitute claim as a whole, and not just the 

features added by the amendment.”). Even though it is undisputed on appeal that UNMRI provided the missing written description in its reply brief, ZyXEL argues that this 

could not cure the procedural defect. ZyXEL points out 

that the regulations require “[a]ll arguments and evidence 

in support of the motion to amend shall be in the motion 

itself” and cites to a number of Board decisions that held 

supplementing a motion to amend through a reply brief 

was improper.7 Lectrosonics, IPR2018-01129, Paper 15 at 

8; 37 C.F.R. § 42.121(b). There is nothing in the MTA Pilot 

Program Notice eliminating this requirement. To the contrary, the MTA Pilot Program Notice references Lectrosonics as governing law. MTA Pilot Program Notice, 84 Fed. 

Reg. at 9500. 

But these arguments as to the requirements of the reply 

fail to take into account the MTA Pilot Program’s purpose. 

The MTA Pilot Program introduced the option for patent 

owners to receive preliminary guidance from the Board 

with respect to motions to amend. MTA Pilot Program Notice, 84 Fed. Reg. at 9497 (noting the option to receive preliminary guidance was “not previously available”). To be 

sure, the MTA Pilot Program did not eliminate

7 See also Lippert Components, Inc. v. Days Corp., 

IPR2018-00777, Paper 28 (PTAB Sept. 24, 2019). 

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requirements as to the contents of the original motion or 

the limitations on reply briefs. See MTA Pilot Program Notice, 84 Fed. Reg. at 9500 (citing Lectrosonics, IPR2018-

01129, Paper 15). But the core purpose of the MTA Pilot 

Program is to allow for the correction of errors in the original motion. The MTA Pilot Program Notice describes the

purpose of preliminary guidance as “provid[ing] an initial 

discussion about whether there is a reasonable likelihood 

that the [motion to amend] meets statutory and regulatory 

requirements for a [motion to amend.]” Id. at 9497. The

MTA Pilot Program Notice further explains “the guidance 

may be helpful to patent owner as it determines whether 

and/or how to revise its [motion to amend] or . . . how to 

respond to information discussed in the preliminary guidance.” Id. at 9500. Thus, a key purpose of issuing preliminary guidance, and the MTA Pilot Program in general, is 

to provide feedback as to whether the motion to amend satisfies the statutory and regulatory requirements so the parties may respond and address any such errors. The MTA 

Pilot Program also permits a patent owner to “respond to 

the Board’s preliminary guidance (if requested) and to the 

petitioner’s opposition,” as well as “file new evidence, including declarations, with its reply.” Id. at 9501. It thus 

appears that the MTA Pilot Program is designed to allow 

reply briefs to address and correct errors. We do not think

the Board erred in permitting UNMRI to use its reply brief 

to supplement the written description support that should 

have been, but was not, included in its original motion to 

amend. 

Even if allowing the reply brief to supply the missing 

information had been inconsistent with the regulations, we 

conclude that any error was harmless error. “We review 

Board decisions pursuant to the standards of the Administrative Procedure Act (‘APA’), 5 U.S.C. § 550 et seq.” Corephotonics, Ltd. v. Apple Inc., 84 F.4th 990, 1001 (Fed. Cir. 

2023). “The judicial review provision of the APA includes 

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a harmless error rule.” In re Chapman, 595 F.3d 1330, 

1338 (Fed. Cir. 2010) (citing 5 U.S.C. § 706); see 5 U.S.C. 

§ 706 (“[D]ue account shall be taken of the rule of prejudicial error.”); see also Shinseki v. Sanders, 556 U.S. 396, 406 

(2009) (“[W]e have previously described § 706 as an ‘administrative law . . . harmless error rule.’” (citations omitted));

In re Watts, 354 F.3d 1362, 1369 (Fed. Cir. 2004) (“We have 

previously made clear that the harmless error rule applies 

to appeals from the Board just as it does in cases originating from district courts.”). 

Any error that was committed by the Board was harmless error because ZyXEL was not prejudiced by the 

Board’s decision to allow the reply brief to supplement the 

initial motion. ZyXEL was on notice of the written description arguments and had ample opportunity to respond in 

its sur-reply.8 The Board waived the page limits on the 

sur-reply and allowed ZyXEL to respond with a 25-page 

brief in order to ensure it had a proper opportunity to respond. Qualcomm Inc. v. UNM Rainforest Innov., Case 

IPR2021-00375, Paper No. 63 at 5–6 (PTAB May 19, 2022). 

ZyXEL asserts, however, that it had no opportunity to 

present any expert declarations to refute UNMRI’s new arguments about written description that were raised in the

reply brief because under the Board’s rules such evidence 

cannot be raised in a sur-reply. Oral Arg. 13:24–13:32; see 

MTA Pilot Program Notice, 84 Fed. Reg. at 9500 (“[N]ew

evidence (including declarations) may be submitted with 

every paper in the [motion to amend] process, except a surreply.”). There are two answers to this. First, ZyXEL never 

made any request to the Board to waive its rules and 

8 In addition to UNMRI’s reply brief, the Board also 

identified where written description support could be located in its preliminary guidance, which ZyXEL received. 

J.A. 940–41. 

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permit it to file an expert declaration. Oral Arg. 12:46–

13:20; see, e.g., Axonics, Inc. v. Medtronic, Inc., 75 F.4th 

1374, 1384 (Fed. Cir. 2023) (noting that the Board may allow new evidence and expert declarations to be submitted 

with sur-replies if requested by the parties to avoid prejudice); Belden Inc. v. Berk-Tek LLC, 805 F.3d 1064, 1081 

(Fed. Cir. 2015) (“Thus, if the petitioner submits a new expert declaration with its Reply, the patent owner can respond in multiple ways. . . . [I]t can request the Board 

waive or suspend a regulation that the patent owner believes impairs its opportunity to respond to the declaration.”); Parkervision, Inc. v. Vidal, 88 F.4th 969, 981 (Fed. 

Cir. 2023) (concluding that because patent owner “failed to 

partake in available procedural mechanisms” such as “request[ing] that its [s]ur-reply be permitted to include arguments and evidence that would otherwise be impermissible 

in a sur-reply,” it could not “fault the Board” for excluding 

new arguments in the sur-reply). Second, ZyXEL does not 

to point to any relevant evidence that it would have presented if the opportunity had been available. ZyXEL did 

not raise any substantive argument regarding the ’855 Application in its opposition to UNMRI’s revised motion to 

amend or in its sur-reply. Under these circumstances, 

ZyXEL has failed to establish prejudice. We affirm the 

Board’s decision to grant the motion to amend. 

B. Further Proceedings

In its opening brief on appeal, ZyXEL only raised two 

arguments regarding the Board’s decision to grant

UNMRI’s motion to amend. ZyXEL first identified the alleged procedural deficiencies discussed in the previous section and second argued the amended claims were obvious 

over the Talukdar and Li combination. We think the 

Board’s decision finding the amended claims not to be obvious over the Talukdar and Li combination was supported 

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by substantial evidence.9 However, at oral argument, 

ZyXEL argued that if claim 8 were held to be unpatentable 

(as we now hold), we should remand to the Board to consider whether the substitute claims are unpatentable. The 

substitute claims are entirely a combination of the limitations of claims 1–4 and 6–8, all of which we have now held 

unpatentable as obvious. It follows from the invalidation 

of claim 8 and the other claims, says ZyXEL, that the substitute claims are unpatentable as a matter of collateral estoppel.10 

“[A]n IPR decision does not have collateral estoppel effect until that decision is affirmed . . . .” United Therapeutics Corp. v. Liquidia Techs., Inc., 74 F.4th 1360, 1372 (Fed. 

Cir. 2023), cert. denied, 144 S. Ct. 873 (2024) (citing XY, 

9 ZyXEL contended that Li discloses the limitation 

“wherein the second communication system has pilot symbols that are denser than those in the first communication 

system.” J.A. 67 (emphasis omitted). The Board determined that while Li discloses using shorter symbol periods, 

it does not disclose denser pilot symbols as required by the 

amended claims. The testimony of ZyXEL’s own expert

(Dr. Roy) supports the Board’s conclusion. 10 See, e.g., Finjan LLC v. SonicWall, Inc., 84 F.4th 

963, 969 (Fed. Cir. 2023) (“For patent claims, collateral estoppel applies where the ‘issues of patentability’ are identical, i.e., where ‘the differences between the unadjudicated 

patent claims and adjudicated patent claims do not materially alter the question of invalidity.’” (citation omitted)); 

Nestle USA, Inc. v. Steuben Foods, Inc., 884 F.3d 1350, 

1352 (Fed. Cir. 2018) (“Importantly, our precedent makes 

clear that collateral estoppel is not limited ‘to patent claims 

that are identical. Rather, it is the identity of the issues

that were litigated that determines whether collateral estoppel should apply.’” (citation omitted) (emphasis in original)).

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LLC v. Trans Ova Genetics, L.C., 890 F.3d 1282, 1294 (Fed. 

Cir. 2018)). We have held that even where the initial decision would be the basis for collateral estoppel, “failure to 

raise collateral estoppel before the appeal process in the 

preclusive case has concluded should not necessarily be a 

work of forfeiture,” and that “courts of appeals have discretion to entertain a party’s res judicata (including issue preclusion) argument when it is raised for the first time on 

appeal.” Uniloc USA, Inc. v. Motorola Mobility LLC, 52 

F.4th 1340, 1348–49 (Fed. Cir. 2022); see also Stanton v. 

D.C. Ct. of Appeals, 127 F.3d 72, 77 (D.C. Cir. 1997) (“As 

res judicata belongs to courts as well as to litigants, even a 

party’s forfeiture of the right to assert it . . . does not destroy a court’s ability to consider the issue sua sponte.” (emphasis in original)). 

Because the potential for collateral estoppel did not become available until our reversal of the Board’s finding as 

to claim 8, we conclude that ZyXEL did not forfeit the argument by failing to raise it earlier. We remand to the 

Board to determine if, in light of our conclusion that claim 

8 is unpatentable as obvious (together with the unpatentability of claims 1–4 and 6–7), collateral estoppel should apply, and the substitute claims should be deemed 

unpatentable. 

On the remand, the Board may also wish to consider if 

the substitute claims are unpatentable as obvious on a new 

ground: the combination of Talukdar, Li, and Nystrom. We 

note that before the Board ZyXEL did not argue that the 

substitute claims were obvious in light of Talukdar, Li, and 

Nystrom. However, “the Board may sua sponte identify a 

patentability issue for a proposed substitute claim based on 

the prior art of record.” Nike, Inc. v. Adidas AG, 955 F.3d 

45, 51 (Fed. Cir. 2020); see also Hunting Titan, Inc. v. 

DynaEnergetics Eur. GmbH, 28 F.4th 1371, 1382 (Fed. Cir. 

2022) (acknowledging the Board may sua sponte advance a 

ground of unpatentability of a substitute claim “where the 

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record readily and persuasively establishes that substitute 

claims are unpatentable for the same reasons that corresponding original claims are unpatentable”); see Q.I. Press 

Controls, B.V. v. Lee, 752 F.3d 1371, 1383 (Fed. Cir. 2014) 

(noting that in the context of a reexamination “the Board

[of Patent Appeals and Interferences] has the discretion to 

issue a new ground of rejection if it has knowledge of one”). 

We therefore remand to the Board to consider whether it 

should entertain an argument that the substitute claims 

are unpatentable as obvious over the combination of Talukdar, Li, and Nystrom.

We also note that “[i]f the Board sua sponte identifies 

a patentability issue for a proposed substitute claim . . . it 

must provide notice of the issue and an opportunity for the 

parties to respond before issuing a final decision under 35 

U.S.C. § 318(a).” Nike, 955 F.3d at 51. 

CONCLUSION

We affirm the Board’s determination that claims 1–4, 

6, and 7 are unpatentable as obvious, and the Board’s decision to grant UNMRI’s motion to amend. We reverse the 

Board’s determination as to claim 8 and conclude that 

claim 8 is unpatentable as obvious. We remand to the 

Board to determine, based on our determination that 

claims 1–4 and 6–8 are unpatentable as obvious, if collateral estoppel applies to substitute claims 44–47, 49, and 50, 

and to allow the Board to consider whether to exercise its 

discretion to evaluate if these claims are invalid based on 

a combination of Talukdar, Li, and Nystrom. 

AFFIRMED-IN-PART, REVERSED-IN-PART, 

REMANDED-IN-PART AS TO THE MAIN APPEAL. 

AFFIRMED AS TO THE CROSS-APPEAL.

COSTS

No costs.

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