United States Court of Appeals 

for the Federal Circuit ______________________

UNILOC 2017 LLC,

Appellant

v.

FACEBOOK INC., WHATSAPP, INC.,

Appellees

______________________

2019-1688

______________________

Appeal from the United States Patent and Trademark 

Office, Patent Trial and Appeal Board in Nos. IPR2017-

01427, IPR2017-02087.

-------------------------------------------------

UNILOC 2017 LLC,

Appellant

v.

FACEBOOK INC., WHATSAPP, INC.,

Appellees

______________________

2019-1689

______________________

Case: 19-1688 Document: 72 Page: 1 Filed: 03/09/2021
2 UNILOC 2017 LLC v. FACEBOOK INC.

Appeal from the United States Patent and Trademark 

Office, Patent Trial and Appeal Board in Nos. IPR2017-

01428, IPR2017-02088.

______________________

Decided: March 9, 2021

______________________

JEFFREY A. STEPHENS, Etheridge Law Group, Southlake, TX, argued for appellant. Also represented by JAMES 

ETHERIDGE, RYAN S. LOVELESS, BRETT MANGRUM.

 PHILLIP EDWARD MORTON, Cooley LLP, Washington, 

DC, argued for appellees. Also represented by HEIDI LYN 

KEEFE, ANDREW CARTER MACE, LOWELL D. MEAD, MARK R.

WEINSTEIN, Palo Alto, CA.

 ______________________

Before LOURIE, WALLACH, and CHEN, Circuit Judges.

CHEN, Circuit Judge.

Uniloc 2017 LLC (Uniloc) appeals from two consolidated inter partes review (IPR) decisions of the Patent Trial 

and Appeal Board (Board) finding unpatentable claims 1–

8 and claims 9–12, 14–17, 25 and 26 of U.S. Patent No. 

8,995,433 (’433 patent) as obvious. 

Foremost at issue in this case is whether 35 U.S.C. 

§ 314(d)’s “No Appeal” provision bars this court’s review of

the Board’s conclusion that under § 315(e)(1) a petitioner 

is not estopped from maintaining the IPR proceeding before it. Under the circumstances of this case, we hold that 

§ 314(d) does not preclude this court from reviewing the 

Board’s § 315(e)(1) estoppel decision. We further conclude 

that the Board did not err in finding that LG Electronics 

Inc. (LG) is not estopped from maintaining its IPR challenge to claims 1–8 and that Facebook and WhatsApp (collectively, Facebook) are not estopped from challenging 

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UNILOC 2017 LLC v. FACEBOOK INC. 3

claim 7. As to the Board’s obviousness conclusions, we see 

no error in the Board’s unpatentability findings. Accordingly, we affirm. 

BACKGROUND

A

Uniloc is the owner of the ’433 patent, which is directed 

to “a system and method for enabling local and global instant [Voice over Internet Protocol (VoIP)] messaging over 

an IP network.” ’433 patent col. 1 ll. 21–23. The patent 

describes the implementation of two modes: “record mode” 

and “intercom mode.” Id. at col. 7 ll. 61–65. In record 

mode, the user’s speech is recorded into an audio file, and 

upon finalization, the user sends a signal to the server that 

the message is ready to be sent. Id. at col. 8 ll. 9–22. The 

message is then sent to the server and the server delivers 

the message to the selected recipient. Id. at col. 8 ll. 25–

43. However, if the recipient is not currently available, i.e., 

disconnected, the server temporarily saves the instant 

voice message and delivers it to the recipient when the recipient connects to its local server, i.e., becomes available. 

Id. The intercom mode operates similarly, but it allows for 

the instant voice message to be transmitted in real-time to 

the selected recipient by storing the message on buffers until the buffers fill and the message is then sent to the server 

to be transmitted to the recipient. Id. at col. 11 ll. 37–60. 

The instant voice message can also contain various attachments. Id. at col. 13 ll. 5–6. 

Claims 1 and 9 are the independent claims at issue 

here.1 They state, in pertinent part, as follows:

1. A system comprising:

1 Although independent claim 6 of the ’433 patent is 

also on appeal, appellant makes no materially different arguments as to claim 6.

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4 UNILOC 2017 LLC v. FACEBOOK INC.

an instant voice messaging application including a 

client platform system for generating an instant 

voice message and a messaging system for transmitting the instant voice message over a packetswitched network via network interface;

. . .

wherein the instant voice messaging application includes a message database storing the instant voice 

message, wherein the instant voice message is represented by a database record including a unique 

identifier; and

wherein the instant voice messaging application includes a file manager system performing at least 

one of storing, deleting and retrieving the instant 

voice messages from the message database in response to a user request.

9. A system, comprising: 

an instant voice messaging application comprising:

a client platform system . . . ;

a messaging system . . . , and

wherein the instant voice message application attaches one or more files to the instant voice message.

’433 patent at claims 1, 9 (emphases added).

B

Facebook filed two petitions for inter partes review of 

the ’433 patent on May 11, 2017. In the first petition (’1427 

IPR Pet.), Facebook challenged claims 1–8 as obvious under 35 U.S.C. § 103 with Zydney2 and Clark3 as references 

2 PCT App. Pub. No. WO 01/11824 A2. 

3 U.S. Patent No. 6,725,228.

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UNILOC 2017 LLC v. FACEBOOK INC. 5

for claims 1–6 and 8 and Zydney, Clark, and Appelman4 as 

references for claim 7. In the second petition (’1428 IPR 

Pet.), Facebook alleged that claims 9, 12, 14, 17, 25, and 26 

would have been obvious under § 103 in view of Zydney, 

claims 11, 15, and 16 would have been obvious in view of 

Zydney and Greenlaw5, and claim 10 would have been obvious in view of Zydney and Newton6.

Meanwhile, a different IPR proceeding challenging 

claims of the ’433 patent, IPR2017-00225, was already 

pending at the Board, petitioned for by Apple Inc. (Apple). 

On June 16, 2017, after it had filed the ’1427 IPR Pet. and 

’1428 IPR Pet., Facebook filed a new petition, identical in 

substance to Apple’s IPR petition, challenging claims 1–6 

and 8 of the ’433 patent and a motion to join the Apple IPR. 

In response, the Board instituted this IPR and granted Facebook’s motion to join Apple’s IPR on October 3, 2017. 

Aside from Apple and Facebook, yet another party was 

interested in invalidating certain claims of the ’433 patent—LG. Before a decision issued on whether to institute 

Facebook’s IPR petitions, on September 11, 2017, LG filed 

IPR petitions identical in substance to Facebook’s ’1427 

and ’1428 IPR petitions and motions to join both of Facebook’s IPRs. 

The Board then, on December 4, 2017, instituted inter 

partes review for Facebook’s ’1427 and ’1428 IPR petitions.7 

Given that Facebook was now a party to multiple different 

4 U.S. Patent No. 6,750,881. 

5 RAYMOND GREENLAW & ELLEN HEPP,

INTRODUCTION TO THE INTERNET FOR ENGINEERS, 1–25 

(1999).

6 HARRY NEWTON, NEWTON’S TELECOM DICTIONARY 

(18th ed. 2002).

7 The Board consolidated the ’1427 IPR and ’1428 

IPR for the final written decision.

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6 UNILOC 2017 LLC v. FACEBOOK INC.

IPR proceedings challenging claims of the ’433 patent, the 

Board foresaw the possibility of a statutory estoppel issue 

arising under 35 U.S.C. § 315(e)(1). At the end of its institution decision in the ’1427 IPR, the Board ordered the parties to “brief the applicability, if any, of 

35 U.S.C. § 315(e)(1)” against Facebook, in light of the anticipated, soon-to-be-issued final written decision for the 

Apple IPR, to which Facebook was a joined party. Facebook, Inc. v. Uniloc USA, Inc., No. IPR2017-01427, 2017 

WL 6034153, at *10 (P.T.A.B. Dec. 4, 2017) (Institution Decision). The Board did not issue a similar request for briefing in its institution decision for the ’1428 IPR. Notably, at 

the time of this supplemental briefing, LG’s petition and 

motion to join remained pending.

In its § 315 supplemental brief, Facebook argued that 

it should not be estopped from challenging the patentability of any claim upon the issuance of a final written decision in the Apple IPR, but even if the Board found it 

estopped, Facebook should at least continue as a petitioner 

here against claim 7, which was never challenged in the 

Apple IPR. See J.A. 606–07. Further, Facebook contended

that, if LG’s IPR petition was granted and LG was joined 

as a party to the ’1427 IPR, then the ’1427 IPR should proceed as to all challenged claims regardless of whether Facebook was found estopped because LG was not a party in 

the Apple IPR. Id. at 610. In response, Uniloc contended 

that, once the Board issued a final written decision in the 

Apple IPR, Facebook would be estopped as to all claims

challenged in the ’1427 IPR, requiring the Board to then 

terminate that proceeding. J.A. 617. In addition, Uniloc 

averred that “[a]llowing LG Electronics to join this IPR will 

create inefficiency and confusion. This IPR should be terminated and LG Electronics can, if it chooses to, file its own 

IPR.” Id.

The Board subsequently instituted IPRs based on LG’s 

petitions and then granted LG’s motion to join the ’1427

IPR and ’1428 IPR on March 6, 2018. J.A. 655. Uniloc then 

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UNILOC 2017 LLC v. FACEBOOK INC. 7

filed its Patent Owner Responses to the original Facebook 

IPR petitions on March 23, 2018. In its ’1427 IPR response, 

inter alia, Uniloc contended that LG should be barred from 

maintaining the ’1427 IPR once the Board issues a final 

written decision in the Apple IPR because LG is estopped 

as a real party in interest (RPI) or privy to Facebook. See,

e.g., J.A. 685. 

Two months later, on May 23, 2018, the Board issued a 

final written decision in the Apple IPR upholding the patentability of all challenged claims. Six days later, on May 

29, 2018, the Board issued a decision in the ’1427 IPR dismissing-in-part Facebook from the IPR, finding that Facebook was “estopped from maintaining the instant 

proceeding under § 315(e)(1)” as to the claims challenged 

in the Apple IPR, i.e., claims 1–6 and 8 of the ’433 patent. 

J.A. 756. As to claim 7, the Board reasoned that Facebook 

was not estopped from maintaining the proceeding for that 

claim because § 315(e)(1)’s estoppel provisions apply only 

to grounds that the petitioner raised or reasonably could 

have raised “with respect to that claim.” Id. at 756–57. 

Lastly, the Board concluded that “[t]he dismissal of Facebook . . . does not limit LG’s participation in any way,” id.

at 758, and therefore, LG was “to assume the role of challenger as to all claims, with Facebook[’s] . . . participation 

limited as to issues concerning solely claim 7,” id. at 759 

(emphasis omitted).

C

The Board issued its final written decision in the consolidated IPRs on November 20, 2018. The Board concluded that all of the challenged claims are unpatentable. 

Facebook, Inc. v. Uniloc 2017 LLC, Nos. IPR2017-01427, 

IPR2017-01428, 2018 WL 6271687, at *33 (P.T.A.B. Nov. 

30, 2018). The Board found that claims 1–6 and 8 of the 

’433 patent would have been obvious over Zydney in view 

of Clark, with Zydney teaching all but the “message database” and Clark supplying this missing limitation. Id. at 

Case: 19-1688 Document: 72 Page: 7 Filed: 03/09/2021
8 UNILOC 2017 LLC v. FACEBOOK INC.

*14, *22, *24. Likewise, the Board concluded that claim 7 

is unpatentable as obvious under a similar combination of 

Zydney, Clark, and Appelman. Id. at *24. The Board also 

concluded that claims 9–12, 14–17, 25, and 26 are unpatentable as obvious, with Zydney again as the primary 

reference. Id. at *27, *29, *31–33. Relevant to this appeal, 

the Board explained that Zydney teaches the “attaches one 

or more files to the instant voice message” limitation of the 

challenged claims. Id. at *25. In reaching this conclusion, 

the Board reasoned that “attach” as used in the claims referred to creating an association between the files and the 

instant voice message, id. at *7, the instant voice message 

in this phrase construed as “data content including a representation of an audio message,” id.

Uniloc sought rehearing before the Board following this 

final written decision. Uniloc’s principal contention in 

seeking rehearing in the ’1427 IPR was that the proceeding 

as a whole should have been terminated once the original 

petitioner, Facebook, was deemed estopped, because 

“[j]oined parties are privy to a petitioner.” J.A. 907. Uniloc 

argued that rehearing was warranted in the ’1428 IPR because it was denied proper notice in violation of due process. This was because, Uniloc contended, “[t]he Board sua 

sponte provided a definition of the term ‘attaches’ that was 

not advanced by” the parties or supported by the record. 

J.A. 2313. The Board denied both rehearing requests. J.A. 

105, 210.

Uniloc appeals both final decisions to our court.8 We 

have jurisdiction pursuant to 28 U.S.C. § 1295(a)(4)(A).

8 Though LG participated in this appeal through the 

briefing stage, LG is no longer a party to the case. See Appellant’s Unopposed Mot. to Withdraw LG Electronics, Inc. 

as a Party, ECF No. 56; ECF No. 57 (granting motion).

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UNILOC 2017 LLC v. FACEBOOK INC. 9

DISCUSSION

Uniloc raises four main disputes on appeal: (1) the 

Board erred in finding that LG is not estopped from challenging claims 1–8 in view of its purported relationship 

with Facebook as an RPI or privy; (2) the Board erred in 

finding that Facebook is not estopped from challenging 

claim 7; (3) the Board erred in its unpatentability determination of claims 1–8 because the cited references do not 

teach the “instant voice message application” of the claims; 

and (4) the Board erred in its unpatentability determination of claims 9–12, 14–17, 25, and 26 because the cited references do not teach the claimed “attaches . . . to” 

limitation. We address each argument in turn.

A

Before we address the merits of Uniloc’s estoppel argument against LG, we consider as an initial matter whether 

we may review this particular challenge. As we have seen

since the onset of IPRs, questions can arise as to whether 

we have the authority to review certain matters addressed 

in an IPR that are not directly related to the ultimate patentability decisions the Board renders in a final written 

decision. See, e.g., Thryv, Inc. v. Click-To-Call Techs., LP, 

–––U.S.–––, 140 S. Ct. 1367 (2020); SAS Institute Inc. v. 

Iancu, –––U.S.–––, 138 S. Ct. 1348 (2018); Cuozzo Speed 

Techs., LLC v. Lee, –––U.S.–––, 136 S. Ct. 2131 (2016). 

Uniloc’s challenge attacks the Board’s finding that LG 

is not an RPI or privy of Facebook and thus not estopped 

from challenging claims 1–6 and 89 of the ’433 patent under 

9 Because the Board found that Facebook is not estopped from challenging claim 7 of the ’433 patent, the potential scope of estoppel for LG extends only to those claims 

for which Facebook was found estopped, i.e., claims 1–6 

and 8. Uniloc argues on appeal that the Board’s conclusion 

that Facebook is not estopped for claim 7 is incorrect and 

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10 UNILOC 2017 LLC v. FACEBOOK INC.

§ 315(e)(1).10 In other words, Uniloc contends that because 

Facebook is estopped by the Apple IPR final written decision from maintaining a challenge to those claims in this 

proceeding (a ruling Facebook does not contest), LG, as an 

alleged “real party in interest or privy of the petitioner” 

likewise is estopped from maintaining this same challenge 

per § 315(e)(1). As to the issue of reviewability, we consider 

the question before us to be whether 35 U.S.C. § 314(d)

statutorily precludes judicial review, following a final written decision in an inter partes review proceeding, of a challenge to the Board’s conclusion that under § 315(e)(1) a 

petitioner is not estopped from maintaining the proceeding 

before it. We conclude, under the circumstances here, we 

are not statutorily precluded from reviewing such a challenge.

Subsection 314(d) dictates that “[t]he determination by 

the Director [of the Patent Office] whether to institute an 

that LG should too be found estopped for claim 7. But as 

we conclude infra, the Board did not err in finding that Facebook is not estopped as to claim 7. Accordingly, no potential estoppel for claim 7 can extend to LG as an alleged 

RPI or privy of Facebook.

10 The text of 35 U.S.C. § 315(e)(1) is as follows:

(e) Estoppel.—

(1) Proceedings before the Office.—

The petitioner in an inter partes review of a claim 

in a patent under this chapter that results in a final 

written decision under section 318(a), or the real 

party in interest or privy of the petitioner, may not 

request or maintain a proceeding before the Office 

with respect to that claim on any ground that the 

petitioner raised or reasonably could have raised 

during that inter partes review.

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UNILOC 2017 LLC v. FACEBOOK INC. 11

inter partes review under this section shall be final and 

nonappealable.” The Supreme Court in Cuozzo interpreted

this provision as overcoming the strong presumption in favor of judicial review “where the grounds for attacking the 

decision to institute inter partes review consist of questions 

that are closely tied to the application and interpretation 

of statutes related to the Patent Office’s decision to initiate 

inter partes review.” Cuozzo, 136 S. Ct. at 2141. In Cuozzo, 

the Court held that judicial review was precluded by 

§ 314(d) for a challenge to the Board’s determinations under § 312(a)(3), which mandates that a petitioner identify 

the grounds of the challenge with particularity, because 

this is “little more than a challenge to the Patent Office’s 

conclusion, under § 314(a), that the information presented 

in the petition warranted review.” Cuozzo, 136 S. Ct. at 

2142 (internal quotation marks omitted).

The Supreme Court has since addressed the judicial review bar under § 314(d) for other challenges stemming 

from decisions of the Patent Office in inter partes review 

proceedings. For example, the Court concluded in SAS Institute that § 314(d) does not preclude judicial review of a 

claim that the agency “exceeded its statutory authority” in 

limiting an inter partes review to fewer than all the claims 

challenged in the petition. 138 S. Ct. at 1359. The Court 

reached the opposite conclusion for reviewability with respect to § 315(b) in Thryv, however, explaining that the petition time bar of § 315(b) “expressly governs institution 

and nothing more,” such that “a contention that a petition 

fails under § 315(b) is a contention that the agency should 

have refused ‘to institute an inter partes review.’” 140 S. 

Ct. at 1373 (quoting § 314(d)). The Court explained that 

review was therefore precluded despite the presumption of 

judicial review. Id. at 1374. 

This court has considered additional types of Board decisions in which the statutory bar of § 314(d) (and similar 

provisions) against judicial review may (or may not) apply. 

In Medtronic, we reasoned that the Board’s decision to 

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12 UNILOC 2017 LLC v. FACEBOOK INC.

terminate proceedings in view of a party’s failure to name 

all RPIs under § 312(a)(2) is not reviewable because “[t]he 

Board’s reconsideration . . . is fairly characterized as a decision whether to institute proceedings, the review of which 

is barred by § 314(d).” Medtronic, Inc. v. Robert Bosch 

Healthcare Sys., Inc., 839 F.3d 1382, 1385 (Fed. Cir. 2016). 

On the other hand, in Credit Acceptance Corp. v. 

Westlake Services, we held that judicial review of a challenge to the Board’s application of the estoppel provision of 

§ 325(e)(1) is not precluded by § 324(e)11 because this provision “is not limited to the institution stage” and “could 

operate to terminate a proceeding even where there existed 

no cause for termination at the time a petition was instituted . . . .” 859 F.3d 1044, 1050 (Fed. Cir. 2017). In that 

case, the alleged estoppel-triggering event did not occur until after the institution of the covered business method

(CBM) patent review proceeding, and thus could not have 

affected the decision to initiate the administrative proceeding. We thus explained that “the estoppel dispute in this 

case is neither a challenge to the Board’s institution decision, nor is it ‘closely tied’ to any ‘statute[] related to the 

Patent Office’s decision to initiate [CBM] review.’” Id. at 

1051 (quoting Cuozzo, 136 S. Ct. at 2141).

More recently, we held the inverse scenario of that in 

Medtronic is likewise not reviewable. That is, a challenge 

“that the Board failed to comply with [the RPI requirement 

of] § 312(a)(2)” and should have terminated the proceeding

is merely “‘a contention that the agency should have refused to institute an inter partes review,’” and therefore not 

reviewable by this court in view of § 314(d). ESIP Series 2, 

11 Subsection 324(e) is nearly identical in language to 

§ 314(d) but applies to other post-grant proceedings. It 

states: “The determination by the Director whether to institute a post-grant review under this section shall be final 

and nonappealable.” § 324(e).

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UNILOC 2017 LLC v. FACEBOOK INC. 13

LLC v. Puzhen Life USA, LLC, 958 F.3d 1378, 1386 (Fed. 

Cir. 2020) (quoting Thryv, 140 S. Ct. at 1373–74). Additionally, we determined, in Facebook, Inc. v. Windy City Innovations, LLC, that judicial review is not precluded by 

§ 314(d) for challenges to “whether the Board’s joinder decisions exceeded the statutory authority provided by 

§ 315(c),” because this challenge was not related to the institution decision but rather concerned “whether the PTO 

had exceeded its statutory authority as to the manner in 

which the already-instituted IPR proceeded.” 973 F.3d 

1321, 1332 (Fed. Cir. 2020).

With that background, we turn now to the question in 

this case of whether we may review the Board’s decision 

that LG is not estopped from maintaining its challenge 

against claims 1–6 and 8. Considering the strong presumption of reviewability of agency action, we see no indication 

that § 314(d) precludes judicial review of the Board’s application of § 315(e)(1)’s estoppel provision in this case, in 

which the alleged estoppel-triggering event occurred after 

institution. Such a holding is a natural consequence of our 

reasoning in Credit Acceptance. We concluded there that 

we could review the patent owner’s challenge to the Board’s 

decision that the petitioner was not estopped from maintaining a patentability challenge under a nearly identical 

statutory estoppel provision, albeit as applied to the CBM

scheme. See Credit Acceptance, 859 F.3d at 1050–51.

As the Supreme Court elucidated in Northcross v. 

Board of Education of Memphis City Schools, when one 

statute “tracks the wording of” another, this is a “strong

indication that the two statutes should be interpreted pari 

passu,” particularly if the two provisions share a common 

purpose. 412 U.S. 427, 428 (1973) (per curiam) (interpreting the language of the Emergency School Aid Act of 1972 

to allow for the ordinary award of attorneys’ fees because 

the relevant provision of the Act “tracks the wording” of the 

similarly focused Civil Rights Act of 1964, which the Court 

had previously interpreted as providing for such ordinary 

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14 UNILOC 2017 LLC v. FACEBOOK INC.

award). Thus, just as we concluded for the CBM estoppel 

provision of § 325(e)(1) in Credit Acceptance, we likewise 

interpret the similarly worded and focused IPR estoppel 

provision of § 315(e)(1) as not so closely tied to institution 

to render judicial review precluded when the estoppel-triggering event arises after institution. See 859 F.3d at 1049–

52 (considering the Supreme Court’s caselaw on reviewability under § 314(d) and concluding that the appellant’s 

challenge under § 325(e)(1) “is neither a challenge to the 

Board’s institution decision, nor is it ‘closely tied’ to any 

‘statute[] related to the Patent Office’s decision to initiate 

[CBM] review.’” (quoting Cuozzo, 136 S. Ct. at 2141) (modifications in original))). Section 315(e)(1)’s use of “maintain” contemplates that the estoppel provision “governs at 

any stage of a subsequent proceeding before the PTO—its 

application is not limited to the institution stage.” Credit 

Acceptance, 859 F.3d at 1050.

Critically, the particular circumstances in Credit Acceptance, i.e., one in which no cause for termination at the 

time of petition existed and the basis for termination developed while the proceeding was ongoing, is exactly that 

which happened here. When the Board instituted review 

in the ’1427 IPR, no estoppel could apply because no final 

written decision had been reached in the Apple IPR. 

Though the Board’s institution decision ordered supplemental briefing regarding the potential, future applicability of § 315(e)(1)’s estoppel provision, due to its awareness 

of the advanced state of the Apple IPR, the Apple IPR final 

written decision did not issue until months after institution 

in this proceeding. The Board’s “no estoppel” decision thus 

was later than and separate from its earlier institution decision, and, consistent with the facts and reasoning of 

Credit Acceptance, is a decision we may review. See Credit 

Acceptance, 859 F.3d at 1049–52; see also Windy City, 973 

F.3d at 1332 (explaining that § 315(c) joinder challenges 

are reviewable by this court despite § 314(d) because “the 

joinder decision is made after a determination that a 

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UNILOC 2017 LLC v. FACEBOOK INC. 15

petition warrants institution, thereby affecting the manner 

in which an IPR will proceed”) (citation omitted)).

Finding Uniloc’s estoppel challenge as to LG reviewable, we now consider the merits of that challenge. “Determining whether a []party is a[n] [RPI] demands a flexible 

approach that takes into account both equitable and practical considerations,” with the heart of the inquiry focused 

on “whether a petition has been filed at a []party’s behest.” 

Applications in Internet Time, LLC v. RPX Corp., 897 F.3d 

1336, 1351 (Fed. Cir. 2018) (citation and internal quotation 

marks omitted). This determination has no bright-line 

test—relevant considerations, however, may include, 

“whether a []party exercises [or could exercise] control over 

a petitioner’s participation in a proceeding, or whether a 

[]party is funding the proceeding or directing the proceeding.” Id. at 1342–43 (citing Office Patent Trial Practice 

Guide, 77 Fed. Reg. 48,756, 48,759 (Aug. 14, 2012)). Privity 

is also a highly fact-based inquiry, similarly “focus[ing] on 

the relationship between the named IPR petitioner and the 

party in the prior lawsuit.” WesternGeco LLC v. Ion Geophysical Corp., 889 F.3d 1308, 1319 (Fed. Cir. 2018) (emphasis added). That is, whether a party is in privity with 

another depends on the nature of the relationship between 

the two; “it is important to determine whether the petitioner and the prior litigant’s relationship—as it relates to 

the lawsuit—is sufficiently close that it can be fairly said 

that the petitioner [already] had a full and fair opportunity 

to litigate” the issues it now seeks to assert. See id. This 

inquiry is grounded in due process concerns for both the 

petitioner (here, LG) and the opposing party (here, Uniloc). 

See id. (citing Taylor v. Sturgell, 553 U.S. 880 (2008)). In 

other words, the inquiry has a dual-focus on preventing the 

petitioner from now lodging a successive attack for which 

it already had a first bite, thus, protecting the defending 

party from an unwarranted second attack, while also ensuring that the petitioner is not unfairly limited in its ability to lodge its challenges if it has not had a full and fair 

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16 UNILOC 2017 LLC v. FACEBOOK INC.

opportunity to do so already. Whether a party is an RPI or 

privy is a question of fact we review for substantial evidence. See Applications in Internet Time, 897 F.3d at 1356.

Uniloc asserts that LG is an RPI or privy of Facebook 

because it “agreed to be bound by the determination of issues in the [’1427 IPR] proceeding below” and “exerted control over substantive filings and oral argument in the 

[’1427 IPR] proceeding below.” Appellant’s Br. at 20. The 

Board agreed with LG that the evidence was simply insufficient to establish a key consideration of the RPI analysis—control. The Board further considered the nature of 

the relationship between the parties for privity based on 

the prior inter partes proceeding, i.e., the Apple IPR, and 

found that nothing in the record supported the conclusion 

that the two parties are “sufficiently close such that both 

should be bound by the trial outcome and related estoppels.” J.A. 104 (quoting WesternGeco, 889 F.3d at 1317–

22). 

The Board’s determination that LG is not an RPI or 

privy of Facebook is supported by substantial evidence. 

Uniloc’s somewhat conclusory arguments never attempt to 

differentiate its position as to RPI and privy, instead 

simply asserting that LG must be one or the other. But 

just because LG expressed an interest in challenging the 

’433 patent’s patentability, through its filing of its own IPR 

petition and joinder motion, does not by itself make LG an 

RPI to Facebook’s IPR. The record lacks any evidence that 

LG exercised any control over Facebook’s decision to file for 

inter partes review (either in the Apple IPR and in this IPR)

or Facebook’s arguments made during the proceedings, and 

vice versa. Moreover, nothing in the record suggests that 

Facebook recruited LG to join as a party to the Facebook 

IPR, thereby making LG an agent advancing Facebook’s 

interests. That is, we see no evidence in the record to suggest that LG is acting “as a proxy [in the ’1427 IPR] for 

[Facebook] to relitigate the same issues” Facebook already 

presented in the Apple IPR. WesternGeco, 889 F.3d at 1319 

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UNILOC 2017 LLC v. FACEBOOK INC. 17

(citing Taylor, 553 U.S. at 894–95). Instead, the record 

shows that LG, through its own counsel, filed its own IPR 

petitions in an effort to be recognized as an additional party 

to the proceeding here, seeking to assert its own interests.12 

The record likewise does not present evidence that LG 

and Facebook, beyond their relationship as joined parties 

in this proceeding, have any sort of “preexisting, established relationship” that indicates coordination amongst 

the two regarding the Apple IPR. See Applications in Internet Time, 897 F.3d at 1351. Without such evidence of

control, in addition to no evidence of joint funding, or even 

any evidence of substantial coordination between the parties as to their respective decisions to bring these proceedings, a finding that LG is an RPI of or in privity with 

Facebook here would be improper. See WesternGeco, 889 

F.3d at 1320–21 (explaining, in finding no privity, that the 

evidence demonstrated the parties were represented by different counsel, had no control over each other, had no collective funding, and lacked substantive involvement with 

12 Uniloc’s estoppel theory for LG relies in part on its 

assertion that LG “unequivocally represent[ed] that it 

would be bound by the Board’s decisions as to the original 

petitioners and that it would not advance any separate arguments from those advanced by [Facebook].” Appellant’s 

Br. at 24. But that argument misunderstands LG’s position, as LG’s joinder motion in the ’1427 IPR makes clear 

that LG had its own interests in challenging the ’433 patent and that it would continue to pursue the IPR even if 

Facebook, for any reason, was no longer a petitioner. See 

J.A. 3345; see also J.A. 3340 (“[LG’s] interests may not be 

adequately protected in the Facebook IPR proceedings,

particularly[, for example,] if the Facebook Petitioner settles with the Patent Owner. [LG] should be allowed to join 

in a proceeding affecting a patent asserted against it.”).

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18 UNILOC 2017 LLC v. FACEBOOK INC.

each other). The mere fact that the Board procedurally required LG and Facebook to consolidate their arguments 

and evidence in combined filings in this proceeding does 

not, without more, make them privies of each other such 

that one petitioner automatically loses its rights to assert 

its challenge once the other petitioner loses its rights 

through estoppel.

We decline, as the Board too did, to conclude that LG 

is estopped as result of Facebook’s participation in the Apple IPR, merely by way of its joinder as a party in this later

proceeding. Uniloc suggests that the Board, in reaching 

this conclusion, failed to address its arguments regarding 

Kofax, Inc. v. Uniloc USA, Inc., No. IPR2015-01207, 2016 

WL 8944779 (P.T.A.B. July 20, 2016).13 Appellant’s Br. at 

21–23. Uniloc asserts that Kofax held that “co-petitioners” 

are automatically RPIs or privies of one another, but this

misunderstands that decision. Kofax, which is non-binding 

on this court, determined that co-petitioners Ubisoft and 

Zebra in an IPR proceeding were RPIs of one another because Ubisoft had named Zebra as an RPI in its filings to 

the Board, due to a preexisting relationship between them. 

2016 WL 8944779, at *1–2. Thus, once Ubisoft was estopped from maintaining the IPR by its role as a petitioner 

in an earlier, different IPR, Zebra, as an undisputed RPI, 

was also estopped. Id. This situation is not the same as 

that here because Facebook did not list LG as an RPI in the 

’1427 IPR making LG unlike Zebra. 

In view of the foregoing, substantial evidence supports 

the finding that LG acted of its own accord in the ’1427 IPR

13 Uniloc suggests, without pointing to any specific instance, that the Board also erred in “misplac[ing] the burden of proof” in its RPI and privity analysis. This 

accusation is not supported by record.

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UNILOC 2017 LLC v. FACEBOOK INC. 19

for claims 1–6 and 8 and is not estopped from maintaining 

its patentability challenge in this proceeding.

B

Uniloc, second, challenges the Board’s estoppel determination for Facebook. Specifically, Uniloc asserts that 

Facebook is estopped from challenging claim 7 of the ’433 

patent because the Board found Facebook estopped from 

challenging the same claims the Board adjudicated in the 

Apple IPR, claims 1–6 and 8. Appellant’s Br. at 25–26. 

This estoppel should also apply to claim 7 because, Uniloc 

argues, claim 7 depends from claim 1 and the Board, by 

allowing such a challenge on claim 7, essentially allowed 

Facebook to continue to attack claim 1, which is broader in 

scope than claim 7. Id. at 26–27. Uniloc notes, moreover, 

that “[t]he Board’s partial dismissal [of Facebook for estoppel on claims 1–6 and 8] essentially resulted in an impermissible partial institution” in violation of SAS Institute. 

Id. at 25.

As a threshold matter, for the reasons set forth above, 

the Board’s determination that Facebook was not estopped 

here from maintaining its challenge to claim 7 is subject to 

judicial review because it was a separate and later determination not closely tied to institution and therefore not 

barred by § 314(d). Facebook argues, nonetheless, that we 

should decline to entertain this challenge because LG was 

also a petitioner for claim 7 and the petition could stand on 

that basis alone. Appellees’ Br. at 43. We decline, however, 

to speculate as to what this proceeding would have looked 

like absent Facebook’s participation for claim 7—we take 

the facts as they are, i.e., Facebook was a named petitioner 

for claim 7, remains a party to this appeal solely because 

its now-lone challenge to claim 7, and Uniloc may challenge 

whether this role was appropriate in view of § 315(e)(1). 

Despite Uniloc’s contentions, we see no error in the 

Board’s determination that the Apple IPR final written decision, which did not address claim 7, does not estop

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20 UNILOC 2017 LLC v. FACEBOOK INC.

Facebook from maintaining its challenge in this proceeding

to claim 7. Section 315 explicitly limits the estoppel to the 

claims previously challenged and for those proceedings 

that resulted in a final written decision:

The petitioner in an inter partes review of a claim

in a patent under this chapter that results in a final 

written decision under section 318(a) . . . may not 

request or maintain a proceeding before the Office 

with respect to that claim on any ground that the 

petitioner raised or reasonably could have raised 

during that inter partes review.

§ 315(e)(1) (emphases added). Because claim 7 was not at 

issue in the Apple IPR, the plain language of the statute

supports the conclusion that Facebook is not estopped from 

challenging this claim in this proceeding, regardless of its 

dependency on claim 1. Moreover, as a joined party in the 

Apple IPR, Facebook could not have raised any grounds for 

the patentability of claim 7 because claim 7 was not already 

challenged in the proceeding. See Windy City, 973 F.3d at 

1338 (“We conclude that the clear and unambiguous language of § 315(c) . . . does not authorize joinder of new issues . . . .”); see also Network-1 Techs., Inc. v. HewlettPackard Co., 981 F.3d 1015, 1027 (Fed. Cir. 2020) (“Thus, 

according to the statute, [§ 315(e),] a party is only estopped 

from challenging claims in the final written decision based 

on grounds that it ‘raised or reasonably could have raised’

during the IPR. Because a joining party cannot bring with 

it grounds other than those already instituted, that party 

is not statutorily estopped from raising other invalidity 

grounds.”). Accordingly, that claim 7 was not at issue in 

the Apple IPR is enough to conclude that Facebook may 

challenge it here.

Uniloc relies on SAS Institute as suggesting that the 

Board’s partial dismissal of Facebook results in an improper partial institution. Appellant’s Br. at 25. We disagree. SAS Institute rejected the Board’s decision there to 

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UNILOC 2017 LLC v. FACEBOOK INC. 21

grant only “partial institution” of a petition for inter partes 

review because such a practice was inconsistent with 35 

U.S.C. § 318(a)’s mandate that “the Patent Trial and Appeal Board shall issue a final written decision with respect 

to the patentability of any patent claim challenged by the 

petitioner.” See 138 S. Ct. at 1354 (internal quotation 

marks omitted) (quoting § 318(a)). Unlike SAS Institute, 

the Board here reached a final written decision on all the 

petitioned claims, due to LG’s status as a petitioner. That 

fact alone is enough to dismiss Uniloc’s argument and render irrelevant Facebook’s partial dismissal from the ’1427 

IPR. 

C

Uniloc’s third and fourth challenges on appeal both relate to the Board’s obviousness determinations. “Whether 

a claimed invention is unpatentable as obvious under § 103 

is a question of law based on underlying findings of fact.” 

In re Gartside, 203 F.3d 1305, 1316 (Fed. Cir. 2000). “The 

Board’s legal conclusion of obviousness is reviewed de 

novo.” Id. This court reviews the Board’s factual determinations in an obviousness analysis for substantial evidence. Id. 

As to claims 1–8, Uniloc argues that the combination of 

Zydney and Clark does not teach the claimed “instant voice 

messaging application” because the claims require that the 

“message database” be embedded into the software agent 

itself, i.e., Clark’s message database must be embedded 

into Zydney’s software agent, not just Zydney’s system. 

Appellant’s Br. at 32.

The Board’s finding in this respect is supported by substantial evidence. Uniloc suggests that the Board impermissibly strayed from the petition in reaching its finding, 

but the petition noted that Clark explicitly teaches incorporating its message database into messaging client software, which corresponds to Zydney’s software agent, see 

J.A. 478–81. Specifically, Clark explains that its 

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22 UNILOC 2017 LLC v. FACEBOOK INC.

“invention can advantageously be integrated with messaging client software and/or messaging server software, such 

as e-mail software, to facilitate the organization of electronic messages.” Clark col. 4 ll. 36–39 (emphases added). 

Clark also teaches elsewhere that its message database 

would be incorporated into the client computer in its software. See id. at col. 10 ll. 27–33, 47–52 and figs. 4A, 4B, 

and 4C. Furthermore, the Board credited the testimony of 

petitioner’s expert, Dr. Lavian, who testified that Clark’s 

stated goal of organization of electronic messages would 

have provided motivation for a skilled artisan to combine 

the message database of Clark into Zydney’s software. See 

Facebook, 2018 WL 6271687, at *15 (citing Dr. Lavian’s 

declaration). We conclude therefore that Uniloc’s argument is without merit and that substantial evidence supports the Board’s finding that the references teach the 

“instant voice messaging application” limitation of the 

challenged claims. 

D

Uniloc’s final argument is that the Board erred in concluding that claims 9–12, 14–17, 25, and 26 are unpatentable because Zydney does not disclose the “attaches one or 

more files to the instant voice message” (“attaches to”) limitation recited in claim 9. Claims 10–12, 14–17, 25, and 26 

all depend from claim 9. Uniloc lodges several challenges. 

First, Uniloc argues that the Board’s adoption of its proposed construction of the “instant voice message” term is 

dispositive. Appellant’s Br. at 32. Second, Uniloc contends 

that the Board improperly shifted the burden of proof. Id.

at 39. Third, Uniloc claims that the Board violated its due 

process in sua sponte construing the “attaches to” limitation in its final written decision. Id. at 40–41. Fourth, 

Uniloc attacks the Board’s determination that Zydney discloses the “attaches to” limitation as not supported by substantial evidence. Id. at 43–51. We are unpersuaded.

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UNILOC 2017 LLC v. FACEBOOK INC. 23

Uniloc’s broader argument appears largely to hinge on 

the construction of the “attaches one or more files to the 

instant voice message” and “instant voice message” terms. 

Claim construction is a legal issue reviewed de novo, based 

on underlying factual findings that are reviewed for substantial evidence. Personal Web Techs., LLC v. Apple, Inc., 

848 F.3d 987, 990 (Fed. Cir. 2017). The Board adopted 

Uniloc’s proposed construction, construing “instant voice 

message” to mean “data content including representation 

of an audio message.” Facebook, 2018 WL 6271687, at *5. 

Neither party disputes this construction on appeal.

Uniloc does, however, take issue with the Board’s construction of “attaches one or more files to the [data content 

including representation of an audio message]” limitation, 

suggesting that the Board’s interpretation of the “attaches 

to” limitation is inconsistent with its interpretation of “instant voice message.” The Board construed this “attaches 

to” limitation to mean “indicating that another file (or files) 

is associated with the ‘instant voice message.’” Id. at *8.14 

Uniloc contends that the “attaches to” term requires more 

than a mere association with the audio file; it requires that 

the attachments be directly appended to the audio file itself, not just to the container for this file. Appellant’s Br. 

at 42. This is because, it argues, the instant voice message, 

as construed by the Board, is equivalent to the audio file, 

14 Per recent regulation, the Board applies the Phillips claim construction standard to IPR petitions filed on or 

after November 13, 2018. See Changes to the Claim Construction Standard for Interpreting Claims in Trial Proceedings Before the Patent Trial and Appeal Board, 83 Fed. 

Reg. 51,340 (Oct. 11, 2018) (codified at 37 C.F.R.

§ 42.100(b)). Because Facebook filed the petitions before 

November 13, 2018, the broadest reasonable interpretation

standard applies to the IPR decisions on appeal.

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24 UNILOC 2017 LLC v. FACEBOOK INC.

not a container including the audio file. We agree with the 

Board.

The claims and written description support the Board’s 

construction of the “attaches to” limitation as requiring association with the instant voice message container. The 

written description explains that the attachment of a file 

can be completed through a “drag-and-drop” method creating “linkages” between the files and the instant voice message. See ’433 patent col. 13 ll. 35–40. Further, claim 14, 

which depends from claim 9, similarly recites that the attaching function is accomplished through a “link” between 

the instant voice message and the files. Considering the 

intrinsic evidence and the broadest reasonable interpretation standard, the Board’s broader construction of “attaching to” is the best reading of the limitation as used in the 

’433 patent. Uniloc fails to point to specific teachings in the 

’433 patent that demonstrate that a narrower construction

is warranted. Moreover, we disagree with Uniloc that the 

Board improperly shifted the burden onto Uniloc in construing the claims. Based on our review of the entirety of 

the Board’s reasoning, the Board fairly weighed the arguments of each side and properly reached its conclusion. 

As to Uniloc’s argument that it was denied proper notice of the construction of this term, we, again, respectfully 

disagree. Filings from as early as the ’1428 IPR Pet. included assertions that Zydney disclosed the “attaches to” 

limitation by attaching the files to the “voice container,” 

see, e.g., J.A. 1902–06. During the IPR, Uniloc itself made 

assertions that the “attaches to” claim language required 

the attaching to be directly to the audio file. See J.A. 883. 

This term was also discussed in detail at the hearing before 

the Board. See, e.g., J.A. 2231–32 (Hearing Transcript). 

We determine, consequently, that Uniloc was afforded sufficient opportunity and notice to address the construction 

of this term. 

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UNILOC 2017 LLC v. FACEBOOK INC. 25

Given the construction of the “attaches to” term, the 

Board’s finding that Zydney discloses this limitation is supported by substantial evidence. Just as the Board noted, 

“Zydney . . . accomplishes ‘attachments’ in the same manner as the ’433 patent, by making an association between 

the instant voice message and the file attachment.” Facebook, 2018 WL 6271687, at *25. The Board pointed to Figure 6 of Zydney as disclosing this associating between the 

attachment and the voice container. Id. The Board also 

credited the testimony of the petitioner’s expert “that a person of ordinary skill in the art would have found it obvious 

that attaching files to a voice container would have been 

part of the process [in Zydney] of packing the message into 

a voice container.” Id. Facebook explains, and Uniloc 

agrees, see Appellant’s Br. at 50 (citing its expert’s testimony about Zydney), that the attaching method disclosed 

by Zydney is a standard technique—Multipurpose Internet 

Mail Extension (MIME) format, Appellees’ Br. at 49–50. 

The Board relied on Zydney’s teachings of the MIME format, which allows attachment of files to be specified in a 

message header, to demonstrate that Zydney discloses attaching the files to the voice container. In view of this evidence, we find the Board’s conclusion to be substantially 

supported.

CONCLUSION

We have considered Uniloc’s remaining arguments and 

are unpersuaded. We affirm the Board’s findings of unpatentability for claims 1–12, 14–17, 25, and 26 of the ’433 

patent. 

AFFIRMED

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