United States Court of Appeals 

for the Federal Circuit ______________________ 

AZURE NETWORKS, LLC AND

TRI-COUNTY EXCELSIOR FOUNDATION,

Plaintiffs-Appellants,

v.

CSR PLC AND CAMBRIDGE SILICON RADIO 

INTERNATIONAL, LLC,

Defendants-Appellees,

AND

ATHEROS COMMUNICATIONS, INC. AND

QUALCOMM INCORPORATED,

Defendants-Appellees,

AND

BROADCOM CORPORATION,

Defendant-Appellee,

AND

MARVELL SEMICONDUCTOR, INC.,

RALINK TECHNOLOGY CORPORATION (Taiwan) 

AND RALINK TECHNOLOGY CORPORATION 

(USA),

Defendants-Appellees.

______________________ 

2013-1459

______________________ 
2 AZURE NETWORKS, LLC v. CSR PLC

Appeal from the United States District Court for the 

Eastern District of Texas in No. 11-CV-0139, Judge 

Michael H. Schneider.

______________________ 

Decided: November 6, 2014

______________________ 

MICHAEL E. JOFFRE, Kellogg, Huber, Hansen, Todd, 

Evans & Figel, P.L.L.C., of Washington, DC, argued for 

plaintiffs-appellants. With him on the brief was ANNA D.

MAYERGOYZ. Of counsel on the brief were ERIC M.

ALBRITTON and MICHAEL BENEFIELD, Albritton Law Firm, 

of Longview, Texas; and DANNY L. WILLIAMS and 

CHRISTOPHER N. CRAVEY, Williams, Morgan & Amerson, 

P.C., of Houston, Texas. 

DOMINIC E. MASSA, Wilmer Cutler Pickering Hale and 

Dorr LLP, of Boston, Massachusetts, argued for all defendants-appellees. With him on the brief for defendantappellee Broadcom Corporation were LOUIS W. TOMPROS,

JASON H. LISS and DANA O. BURWELL. On the brief for

defendants-appellees Atheros Communications, Inc., et 

al., were TIMOTHY TETER, LORI R. MASON and MATTHEW J.

BRIGHAM, Cooley LLP, of Palo Alto, California. On the 

brief for defendants-appellees CSR PLC, et al., were

JEFFREY E. OSTROW and JONATHAN C. SANDERS, Simpson 

Thacher & Bartlett LLP, of Palo Alto, California; and 

KERRY L. KONRAD, of New York, New York. 

______________________ 

Before REYNA, MAYER, AND CHEN, Circuit Judges. 

Opinion for the court filed by Circuit Judge Chen. 

Dissenting-in-part opinion filed by Circuit Judge Mayer.
AZURE NETWORKS, LLC v. CSR PLC 3

CHEN, Circuit Judge.

Plaintiffs Azure Networks, LLC (Azure) and TriCounty Excelsior Foundation (Tri-County) sued CSR PLC, 

Cambridge Silicon Radio International, LLC, Atheros 

Communications, Inc., Qualcomm Inc., Broadcom Corp., 

Marvell Semiconductor, Inc., Ralink Technology Corp. 

(Taiwan), and Ralink Technology Corp. (USA) (collectively, Appellees) for alleged infringement of U.S. Patent No. 

7,756,129 (the ’129 patent). The district court granted the 

Appellees’ motion to dismiss Tri-County for lack of standing, finding that Tri-County had effectively assigned 

Azure the ’129 patent. Because we agree that the agreement between Tri-County and Azure constituted an 

effective assignment for purposes of standing, we affirm 

the dismissal of Tri-County. 

The district court also construed the term “MAC address” in the ’129 patent as “a device identifier generated 

by the hub device” and not, as Azure and Tri-County 

suggested, “an address that uniquely identifies a device or 

group of devices on a shared communication medium.” 

Azure stipulated to a judgment of noninfringement under 

the district court’s construction of “MAC address.” Because the district court improperly construed the term, we 

vacate the judgment of noninfringement and remand.

BACKGROUND

A. The ’129 Patent

The ’129 patent, entitled “Personal Area Network 

with Automatic Attachment and Detachment,” describes a 

network for wireless communications between a central 

hub device and a number of surrounding peripheral 

devices in close proximity with the hub device. The 

specification details the use of “a wireless personal area 

network [PAN] that permits a host device to communicate 

with a varying number of peripheral devices with minimal interference from neighboring networks.” ’129 pa-
4 AZURE NETWORKS, LLC v. CSR PLC

tent, 2:66–3:3. To do so, the hub device “orchestrates all 

communication in the PAN,” including managing the 

timing of the network, allocating available bandwidth 

among the peripheral devices, and supporting the attachment, detachment, and reattachment of peripheral 

devices. Id. at 3:33–39. The hub and the peripheral 

devices communicate with one another over a predefined 

set of streams, or one-way communication links. Id. at 

3:53–56.

Claim 14 is representative of the accused claims to a 

hub device:

14. A hub device for use within a personal area 

network, comprising:

circuitry, and

a transceiver in communication with the circuitry, 

the hub device configured to cause the transceiver 

to

i) send a message to indicate the availability of the hub device for peripheral device 

attachment,

ii) receive, from a first peripheral device, a 

message indicating the availability of the 

first peripheral device for communication 

with the hub device,

iii) send, to the first peripheral device, a 

signal including a first peripheral device 

identifier, 

iv) receive, from the first peripheral device, a response,

v) send a hub response to the first peripheral device, and
AZURE NETWORKS, LLC v. CSR PLC 5

vi) receive, from the first peripheral device, a second peripheral response including the first peripheral device identifier.

Id. at claim 14 (emphasis added).

The parties agree that “peripheral device identifier” in 

the asserted claims means “an element that identifies the 

peripheral device.” Joint Appendix (J.A.) 1446. Claim 43 

depends from claim 14 and introduces the disputed “MAC

address” term: 

43. The hub device according to claim 14, wherein 

the hub device is configured such that a plurality 

of MAC addresses is capable of being used for 

identification in association with the first peripheral device.

’129 patent, claim 43.

At the time of invention, the conventional meaning of 

“MAC address,” i.e., a Media or Medium Access Control 

address, was that it operated to uniquely identify a wireless device and could be generated in two ways—by the 

manufacturer of the device or by the local network. The 

district court concluded that the patentee acted as his 

own lexicographer by redefining the claimed “MAC address.” In so doing, the district court relied on the specification in two ways. First, a statement in the specification 

allegedly coined a new “MAC address” term that differs 

from the traditional MAC address as known to a person of 

ordinary skill in the art. That statement provided: “Each 

device is identified by a Media Access (MAC) address.” 

’129 patent, 3:31–32. And second, various statements in 

the specification discussed the generation and assignment 

of the MAC address by the hub device. See Azure Networks, LLC v. CSR PLC, No. 6:11CV139 LED-JDL, 2013 

WL 173788, at *4 (E.D. Tex. Jan. 15, 2013). Based on 

these passages, it construed “MAC address” as “a device 

identifier generated by the hub device.” Id. at *5.
6 AZURE NETWORKS, LLC v. CSR PLC

B. Tri-County’s License to Azure

The ’129 patent has passed through many hands of 

ownership, but it was eventually acquired by Azure, a 

Texas limited liability company located in the Eastern 

District of Texas. Azure then sought local charities to join 

in its patent enforcement activities. Ultimately, it partnered with Court Appointed Special Advocates (CASA) of 

Harrison County,1 which formed Tri-County, a Texas nonprofit corporation with its principal place of business in 

the Eastern District of Texas. In 2010, Azure donated 

multiple patents and patent applications, including the 

application that would issue as the ’129 patent, to TriCounty.2 

A few weeks after the donation, Tri-County and Azure 

entered into an “Exclusive Patent License Agreement” 

(hereinafter, Agreement), which transferred back to Azure 

a number of rights in the ’129 patent. In particular, the 

Agreement granted Azure the exclusive, worldwide, 

transferable right to (i) make, have made, use, sell, offer 

to sell, import, and lease any products, (ii) use and perform any method, process, and/or services, and (iii) otherwise practice any invention in any manner under the ’129 

patent. It also granted Azure the “full right to enforce or 

and/or sublicense” the ’129 patent, J.A. 1201 § 1.2, includ1 CASA of Harrison County is a member of the National Court Appointed Special Advocate Association and 

provides court-appointed advocacy for neglected and 

abused children in Harrison County. J.A. 454. 

2 The Appellees allege that Azure was motivated to 

donate the patents and patent applications to Tri-County 

in order in order to further establish venue in the Eastern 

District of Texas and to deduct from Azure’s tax liability 

the value of its donation and portions of litigation proceeds owed to Tri-County. Appellees’ Br. 8, 19; see also 26 

U.S.C. § 170(m).

 
AZURE NETWORKS, LLC v. CSR PLC 7

ing the authority to reach settlements without TriCounty’s consent. Specifically, the Agreement provided 

that “Azure will have the exclusive right, but not the 

obligation, to maintain, enforce, or defend” the ’129 patent, but has the “obligation to exercise good faith business judgment to monetize” the ’129 patent, “including

but not limited to licensing [it] to third parties.” J.A. 1204 

§ 4.4. Azure also received the right to assign the entire 

Agreement or any of Azure’s rights under the Agreement, 

without Tri-County’s consent, to any Azure affiliate in 

connection with the sale of a material portion of any 

Azure business unit. And, finally, the Agreement gave

Azure, not Tri-County, the exclusive right, but not the 

obligation, to control future prosecution or pay maintenance fees related to the ’129 patent family. 

In exchange, Tri-County retained the right to receive 

33% of the proceeds from Azure’s litigation or licensing 

activities for the first five years and 5% thereafter. Azure 

must pay Tri-County the respective percentages within 

thirty days after each calendar quarter in which Azure 

receives the proceeds. Tri-County also reserved “a royalty-free, personal, non-transferable, non-exclusive right” to 

practice the ’129 patent and make Tri-County branded 

products. J.A. 1201–02 § 2.3. Additionally, Tri-County 

retained a right to terminate the Agreement if Azure 

breached its obligations or if Tri-County’s obligations 

under the Agreement placed Tri-County’s tax-exempt 

status at risk. Tri-County also reserved reversionary 

rights in the ’129 patent once the Agreement expires. In 

particular, the Agreement automatically expires on March 

27, 2018, with two years remaining on the patent term, 

but Tri-County has the option to renew in one-year increments if it notifies Azure at least thirty days in advance. In addition, Tri-County is obligated not to 

encumber the ’129 patent in any way and to participate in 

litigation at Azure’s request and in Azure’s sole discretion.
8 AZURE NETWORKS, LLC v. CSR PLC

Tri-County and Azure filed suit together against the 

Appellees, who thereafter sought to dismiss Tri-County

from the case. They argued that the significant rights 

transferred to Azure under the Agreement constituted an 

effective assignment for purposes of standing, leaving TriCounty with no rights to sue as co-plaintiff. The district 

court agreed, finding that Tri-County’s title in the patent 

and financial and reversionary interests therein were not 

sufficient to confer standing upon Tri-County. J.A. 34–35. 

On the district court’s dismissal of Tri-County, Azure and 

Tri-County appealed, and we have jurisdiction under 28 

U.S.C. § 1295(a)(1). 

DISCUSSION

I. Standing

Standing is a matter of law that we review de novo. 

Evident Corp. v. Church & Dwight Co., Inc., 399 F.3d 

1310, 1313 (Fed. Cir. 2005). The Patent Act governs 

standing to sue for infringement, and it provides that only 

the patentee and his successors in title are entitled to 

bring a civil action for infringement. Propat Int’l Corp. v. 

RPost, Inc., 473 F.3d 1187, 1189 (Fed. Cir. 2007) (citing 35 

U.S.C. § 281); Speedplay, Inc. v. Bebop, Inc., 211 F.3d 

1245, 1249–50 (Fed. Cir. 2000); Prima Tek II, L.L.C. v. ARoo Co., 222 F.3d 1372, 1376–77 (Fed. Cir. 2000). A party 

is a patentee if it holds legal title to the patent, either by 

issuance or assignment. Propat, 473 F.3d at 1189; 

Speedplay, 211 F.3d at 1249–50.

Even if a patentee does not transfer legal title, it may 

transfer significant rights to the patent. When the patentee transfers rights, the “party that has been granted 

all substantial rights under the patent is considered the 

owner regardless of how the parties characterize the 

transaction that conveyed those rights.” Speedplay, 211 

F.3d at 1250. “In that event, the transferee is treated as 

the patentee and has standing to sue in its own name.” 

Propat, 473 F.3d at 1189. And whichever party has all, or 
AZURE NETWORKS, LLC v. CSR PLC 9

substantially all, rights in the patent “alone has standing 

to sue for infringement.” Morrow v. Microsoft Corp., 499 

F.3d 1332, 1340 (Fed. Cir. 2007); see also Alfred E. Mann 

Found. for Scientific Research v. Cochlear Corp., 604 F.3d 

1354, 1358–59 (Fed. Cir. 2010) (“A patent owner may 

transfer all substantial rights in the patents-in-suit, in 

which case the transfer is tantamount to an assignment of 

those patents to the exclusive licensee, conferring standing to sue solely on the licensee.”). Therefore, when all 

rights or all substantial rights have been transferred, the 

transferee—and not the transferor—is the effective owner 

for purposes of standing. See Speedplay, 211 F.3d at 

1250.

In patent licensor-licensee standing cases, we are typically confronted with one of two scenarios: (1) cases in 

which the exclusive licensee brings suit alone, requiring 

us to decide whether the license agreement conferred 

sufficient rights on the licensee for standing; or (2) cases 

in which the licensor brings suit alone, and we decide 

whether the licensor has transferred away enough rights 

to divest it of the right to sue. This is not the typical case. 

Here, both the licensor and the licensee have brought the 

suit together, and the accused infringer seeks dismissal of 

the licensor. Therefore, our inquiry in this case is twofold: (1) whether Tri-County transferred all substantial 

rights under the ’129 patent to Azure, making Azure the 

effective owner; and if so, (2) whether Tri-County may 

nevertheless join in an infringement suit brought by the 

licensee, but now effective owner, Azure. 

A 

“To determine whether an exclusive license is tantamount to an assignment, we ‘must ascertain the intention 

of the parties [to the license agreement] and examine the 

substance of what was granted.’” Mann, 604 F.3d at 1359

(quoting Mentor H/S, Inc. v. Med. Device Alliance, Inc., 

240 F.3d 1016, 1017 (Fed. Cir. 2001)). The parties’ intent 
10 AZURE NETWORKS, LLC v. CSR PLC

alone is not dispositive. See Vaupel Textilmaschinen KG 

v. Meccanica Euro Italia S.P.A., 944 F.2d 870, 876 (Fed. 

Cir. 1991) (finding agreement amounted to an assignment, even though entitled “exclusive license,” because it 

transferred substantial rights to licensee); see also 

Speedplay, 211 F.3d at 1250. 

We must also consider a non-exhaustive list of rights 

for determining whether a licensor has transferred “all 

substantial rights” to the licensee, including: (1) the 

nature and scope of the right to bring suit; (2) the exclusive right to make, use, and sell products or services 

under the patent; (3) the scope of the licensee’s right to 

sublicense; (4) the reversionary rights to the licensor 

following termination or expiration of the license; (5) the 

right of the licensor to receive a portion of the proceeds 

from litigating or licensing the patent; (6) the duration of 

the license rights; (7) the ability of the licensor to supervise and control the licensee’s activities; (8) the obligation 

of the licensor to continue paying maintenance fees; and 

(9) any limits on the licensee’s right to assign its interests 

in the patent. Mann, 604 F.3d at 1360–61.

The parties do not dispute that the Agreement transferred to Azure an exclusive license to practice the ’129 

patent. “[T]ransfer of the exclusive right to make, use, 

and sell products or services under the patent is vitally 

important to an assignment.” Id. at 1360. Also critical to 

our inquiry is that the Agreement granted Azure the 

exclusive right to enforce and defend the ’129 patent. In 

determining the nature of a transfer of rights, we have 

repeatedly recognized that a “key factor has often been 

where the right to sue for infringement lies.” Aspex 

Eyewear, Inc. v. Miracle Optics, Inc., 434 F.3d 1336, 1342

(Fed. Cir. 2006); see also Mann, 604 F.3d at 1361 (recognizing that the “the most important consideration” in the 

analysis is “the nature and scope of the exclusive licensee’s purported right to bring suit, together with the 
AZURE NETWORKS, LLC v. CSR PLC 11

nature and scope of any right to sue purportedly retained 

by the licensor”). 

It is not uncommon for a licensor to transfer to its licensee the exclusive right to enforce the patent. But 

significant to this case, Tri-County reserved no right to 

have control over, to veto, or to be notified of any of Azure’s licensing or litigation activities. Retaining control of 

these activities is also critical to demonstrating that the 

patent has not been effectively assigned to the licensee. 

See, e.g., Propat, 473 F.3d at 1192 (noting that retention 

of right to veto, be consulted about, or give consent to 

litigation decisions weighs in favor of finding agreement a 

license, not an assignment); Mann, 604 F.3d at 1362–63 

(noting that right to have joint control over litigation or 

right to bring suit against alleged infringer if licensee 

refuses to bring suit would also indicate that licensor 

retained substantial rights); Vaupel, 944 F.2d at 875 

(patentee retained only right to be informed about litigation and no right to control litigation decisions, suggesting 

an assignment of the patent); Speedplay, 211 F.3d at 1251

(holding that licensor retained no veto rights over licensee’s litigation activities and licensee’s complete control 

over litigation suggested that licensee obtained substantial rights).

Rather than retaining any control over litigation activities, Tri-County has a strict duty under the Agreement 

to “join Azure as a party and cooperate with Azure in any 

patent infringement suit, if, desirable to address a legal 

issue,” such as standing. J.A. 1204 § 4.4. Tri-County 

must join “at Azure’s request,” and after joinder, “Azure 

would maintain full and absolute control over any such 

patent infringement suit, including settlement of any 

related claims or causes of action.” Id. Tri-County’s 

joinder “would be limited solely to cooperation and that 

which is necessary to address the legal issue.” Id. As the 

district court recognized, nothing about this relationship 

structure indicates that Tri-County has control over any 
12 AZURE NETWORKS, LLC v. CSR PLC

aspect of litigation involving the ’129 patent. Rather, it is 

clear that Azure is holding all the strings. In sum, Azure’s exclusive right to sue, exclusive license, and freedom 

to sublicense are factors that strongly suggest that the 

Agreement constitutes an effective assignment.

Tri-County argues that other factors demonstrate that 

it retained enough rights such that whatever was transferred to Azure was something less than “all substantial 

rights.” First, it points out that it has a right to receive a 

portion of the proceeds from the enforcement of the ’129 

patent. But that economic interest alone does not defeat a 

transfer of substantial rights in the face of the factors 

above that strongly indicate Azure’s ownership. See

Propat, 473 F.3d at 1191 (“To be sure, the fact that a 

patent owner has retained a right to a portion of the 

proceeds of the commercial exploitation of the patent . . . does not necessarily defeat what would otherwise 

be a transfer of all substantial rights in the patent.”)

(citing Rude v. Westcott, 130 U.S. 152, 162–63 (1889)). 

Second, it argues that it retained the right to practice 

the ’129 patent, including the right to make, sell, and use 

Tri-County-branded products covered by the patent. See 

Fieldturf, Inc. v. Sw. Recreational Indus., Inc., 357 F.3d 

1266, 1269 (Fed. Cir. 2004) (“[L]icensor’s retention of a 

limited right to develop and market the patented invention indicates that the licensee failed to acquire all substantial rights.”). But in this case, this factor has little 

force as Tri-County does not make or sell any products, 

J.A. 8976–81, and the evidence on record suggests that 

Tri-County will not make or sell any products in the 

future. While Tri-County continues to retain this right 

under the Agreement, its right is nonexclusive. We have 

held that a nonexclusive license confers no standing on 

the licensee because the licensee does not have a legally 

protected interest conferred by the Patent Act. See 

Propat, 473 F.3d at 1193–94 (holding that party has 

standing to sue if it “has a legally protected interest in the 
AZURE NETWORKS, LLC v. CSR PLC 13

patent created by the Patent Act,” and that bare licensee 

has no standing). That same logic applies even if it is the 

patent owner holding the nonexclusive right and the 

licensee holds the exclusionary rights. It is the licensee, 

Azure, who may freely sublicense other parties or, instead, tolerate infringement. So while infringement may 

cause Tri-County pecuniary loss, the Patent Act confers 

Azure, not Tri-County, with standing to bring suit for the 

infringement. See Ortho Pharm. Corp. v. Genetics Inst., 

Inc., 52 F.3d 1026, 1031 (Fed. Cir. 1995) (holding that 

“[p]ractice of the invention by others may indeed cause 

[the nonexclusive licensee] pecuniary loss,” but “economic 

injury alone does not provide standing to sue under the 

patent statute”) (internal citations omitted).

Third, Tri-County contends that it has termination 

rights that limit whatever rights Azure has received 

under the Agreement. In particular, each party has the 

right to terminate the Agreement if the other party “substantially fails to perform or otherwise materially breaches any of the material terms, covenants or provisions of 

[the] Agreement.” J.A. 1207 § 7.8. Tri-County maintains 

that Azure must exercise good-faith judgment in monetizing the patents and report its efforts to Tri-County annually. Appellants’ Br. 27. Tri-County argues that it can 

then exercise its right to terminate the Agreement, and 

regain all rights conferred to Azure, if it determines that 

Azure’s performance under this “good faith” provision is 

unsatisfactory. Because Azure must enforce and license 

the ’129 patent and share any proceeds with Tri-County, 

Tri-County contends that its termination right enables it 

to monitor—and, thus, control—Azure’s fulfillment of its 

obligations. Reply Br. 6–7. According to Tri-County, this

termination right indicates that it retained significant 

ownership interests in the ’129 patent. We do not agree.

We have held that termination rights conditioned upon the licensee’s “failure to perform up to the specified 

benchmarks” provide some indication that the licensor 
14 AZURE NETWORKS, LLC v. CSR PLC

retained ownership in the patent. See Propat, 473 F.3d at 

1191–92. But the discussion of the termination right in 

Propat must be read in context. We explained that the 

Propat termination right, by itself, was not sufficient to 

show ownership; rather, we were persuaded by the showing of additional rights retained by the licensor, including 

one of the most crucial ones—the right to control the 

litigation and licensing decisions:

In addition, [the licensor] retains an economic interest in the patent and a substantial measure of 

control over decisions affecting the patent rights. 

It enjoys an equity interest in the proceeds of licensing and litigation activities, a right to notice 

of licensing and litigation decisions and the right 

to veto such decisions as long as the veto power 

was not exercised unreasonably, and the unrestricted power to bar [the licensee] from transferring its interest in the patent to a third party. In 

no case has this court held that a patentee who retains such broad and wide-ranging powers with 

respect to a patent has nonetheless transferred 

“all substantial rights” in the patent. 

Id. at 1191. In Propat, the licensor retained the responsibility to maintain the patent, the right to notice of the 

licensee’s decision-making, the right to veto licensing and 

litigation decisions, the right to veto any transfer of the 

licensee’s rights, in addition to the right to terminate the 

license if the licensee failed to meet certain benchmarks. 

Id. at 1190–91. That is not the case here.

Tri-County’s right to monitor whether Azure breaches 

any of its obligations does not amount to the type of 

control that we have found indicative of ownership in 

prior cases. Tri-County does not have the right to veto 

any of Azure’s decisions, and Azure is not obligated to 

obtain Tri-County’s consent before acting. In fact, TriCounty does not even have the right to receive notice 
AZURE NETWORKS, LLC v. CSR PLC 15

before Azure acts. Nor does Tri-County have the obligation to maintain the patent; maintenance lies with Azure, 

at Azure’s option. It is true that Tri-County may terminate the Agreement if Azure breaches its obligations, but 

Tri-County does not explain—nor can we envision—how a 

general good-faith requirement that inures to the financial benefit of both parties, with nothing more, would 

allow Tri-County to trump Azure’s express and unilateral 

rights and exert control over Azure’s licensing or litigation 

decisions. 

As an additional argument, Tri-County points to its 

right to terminate the Agreement if it incurs unwanted 

tax liabilities as a basis for demonstrating that it retained 

ownership. But if Tri-County terminates the Agreement 

for this reason, Azure has the option to re-acquire the ’129 

patent for $305,000. J.A. 1207–08. Therefore, TriCounty’s termination under this provision does not outright deprive Azure of controlling the patent. TriCounty’s termination right under this provision loses 

force as a factor suggesting it has substantial rights over 

the ’129 patent. 

Fourth, Tri-County contends that, in addition to its 

termination rights, the Agreement automatically terminates on March 27, 2018—two years before the patent 

expires—leaving Tri-County a two-year reversionary 

interest in the patent. Although Tri-County may optionally extend the Agreement in one-year increments, it 

argues that, in general, agreements that terminate before 

patent expiration leave the licensor with a substantial 

interest in the patent. 

In Aspex Eyewear, we addressed the effect of a hard 

termination date, i.e., a date beyond which the license 

cannot be renewed and all rights revert back to the licen-
16 AZURE NETWORKS, LLC v. CSR PLC

sor.3 The termination clause in that case provided that 

the license would expire in 2003, but it gave the licensee 

one option to extend the term another three years. 434 

F.3d at 1338 n.2. The license would finally terminate in 

2006, still leaving eleven more years remaining on the 

patent term, which was to expire in 2017. Id. at 1338 & 

n.4. 

The rights distributed between the licensee and licensor in Aspex Eyewear were similar to the distribution of 

rights between Tri-County and Azure. Like Azure, the 

licensee in Aspex Eyewear held the exclusive right to 

practice the invention, the right to bring suit for infringement, and the unrestricted right to sublicense, 

while the licensor, like Tri-County, retained no right to 

make litigation or licensing decisions. We acknowledged 

that this distribution strongly suggested the license was 

an effective assignment for purposes of standing. Id. at 

1342. Yet the hard termination date confirmed to us that 

the licensor retained ownership of the patent because the 

licensor would regain all the rights transferred to the 

licensee with a majority of the patent term remaining: 

It was not a situation in which [the licensee] had 

an exclusive license with all substantial rights 

that was only defeasible in the event of a default 

3 Tri-County and the Appellees dispute whether the 

discussion of a hard termination date in Prima Tek II

should guide the analysis. In that case, however, we 

declined to express any opinion on the significance of hard 

termination dates. See 222 F.3d at 1378 (“Significantly, 

the agreement does not specify a ‘hard’ termination date 

beyond which the license cannot be renewed, and we 

express no opinion as to the effect of such a provision on a 

licensee’s standing to sue.”) (emphasis added) (internal 

citation omitted). Prima Tek II’s discussion of reversionary rights therefore is inapplicable. 

 
AZURE NETWORKS, LLC v. CSR PLC 17

or bankruptcy, or some other condition subsequent. By having rights for only a limited portion 

of the patent term, it simply did not own the patent. It was merely an exclusive licensee without 

all substantial rights. The ‘747 patent was never 

assigned; it was exclusively licensed for only a 

fixed period of years, which does not meet the all 

substantial rights standard. Thus, we hold that 

the Contour/Chic agreement was a license, not an 

assignment, and [the licensor] was the owner of 

the patent when the complaint was filed and entitled to sue.

Id. at 1342–43 (footnote omitted). We distinguished 

clauses, like the one in Prima Tek II, that lacked a definite termination date because “the term of the agreement 

existed potentially for the life of the respective patents, 

and it was presumable that the transferred patent would 

never return to the assignor.” Id. at 1343.

The termination clause in Tri-County’s Agreement 

does not have the same kind of hard termination date as 

in Aspex Eyewear. Instead, the Agreement states that it 

“shall end . . . on the termination date of 03/27/2018 or at 

the end of each year thereafter, unless [Tri-County] 

notifies Azure at least 30 days in advance of its intent to 

renew the agreement for an additional year.” J.A. 1207 

§ 7.8. We expressly noted in Aspex Eyewear that this type 

of renewal cycle presumes that the patent “would never 

return to the assignor.” 434 F.3d at 1343. We also note 

that eleven years remained on the patent’s term in Aspex 

Eyewear following the expiration date of the agreement 

with no indication of the likelihood of extending or renewing the license after the first option to extend. In contrast, only two years remain on the ’129 patent term 

following the March 27, 2018 termination date. Such 

short patent term life following expiration, coupled with 

the rolling renewal cycle that can extend to the end of the 

patent’s term, provides another indicator that Tri-County 
18 AZURE NETWORKS, LLC v. CSR PLC

transferred all substantial rights to the patent. Therefore, the district court was correct in concluding that the 

reversionary right in the Agreement does not suggest, as 

Tri-County contends, that Tri-County retained ownership 

of the patent. 

After weighing all the factors, we agree with the district court that Azure acquired significant rights under 

the ’129 patent, including the right to enforce, to license, 

to control the licensing and litigation, to sublicense, to 

practice exclusively, and to maintain the patent. TriCounty’s economic interests, limited termination rights,

and unfixed reversionary interest with only a very limited 

amount of time remaining on the patent do not demonstrate that it retained ownership. As the district court 

found, the balance of factors establishes that Tri-County 

transferred all substantial rights in the ’129 patent to 

Azure, making Azure the effective owner for purposes of 

standing. 

B 

Azure and Tri-County argue that even if the Agreement constitutes an assignment for purposes of standing, 

Tri-County would still be able to join suit with Azure. 

They maintain that Tri-County still has interests in the 

’129 patent that are in jeopardy, including its reversionary interest and its interest in receiving proceeds from 

enforcing the patent. Appellants’ Br. 35–36. Having an 

interest in the litigation, however, does not confer standing. To bring or join suit, Tri-County must have “exclusionary rights and interests created by the patent 

statutes.” Morrow, 499 F.3d at 1340 (emphasis added). 

Parties who “hold less than all substantial rights to 

the patent and lack exclusionary rights under the patent 

statute” do not have standing. Id. at 1340–41 (emphasis 

added). This lack of standing “cannot be cured by adding 

the patent title owner to the suit.” Id. at 1341; Propat, 

473 F.3d at 1193–94 (“By contrast, a bare licen-
AZURE NETWORKS, LLC v. CSR PLC 19

see . . . lacks standing to sue third parties for infringement . . . . A bare licensee cannot cure its lack of standing 

by joining the patentee as a party.”). 

As discussed above, Tri-County transferred all substantial rights in the ’129 patent to Azure, including all 

exclusionary rights. Tri-County serves effectively as a 

nonexclusive licensee. The district court properly concluded that Tri-County lacks standing to bring suit, but 

more importantly, to even join the suit. Because TriCounty does not have any exclusionary rights under the 

’129 patent, it lacks standing to join the suit as a coplaintiff. Tri-County’s standing deficiency cannot be 

cured by adding Azure to the suit. See Morrow, 499 F.3d

at 1343 (“To demonstrate entitlement to join as a coplaintiff [a party] must have the right to exclude others 

from making, using or selling the invention in the United 

States.”). We therefore affirm the district court’s dismissal of Tri-County.

II. “MAC Address”

Claim construction is a matter of law that we review

de novo. Lighting Ballast Control LLC v. Philips Elecs. N. 

Am. Corp., 744 F.3d 1272 (Fed. Cir. 2014) (en banc). 

There is a “heavy presumption” that claim terms “carry 

their accustomed meaning in the relevant community at 

the relevant time.” Home Diagnostics, Inc. v. LifeScan, 

Inc., 381 F.3d 1352, 1355 (Fed. Cir. 2004). The district 

court, however, construed “MAC address” narrowly as a 

local address generated by the hub, even though the 

ordinary and customary meaning included either local or 

universal MAC addresses. Departure from the ordinary 

and customary meaning is permissible only when the 

patentee has acted as his own lexicographer or disavowed 

claim scope in the specification or during the prosecution 

history. Phillips v. AWH Corp., 415 F.3d 1303, 1316 (Fed. 

Cir. 2005) (en banc). The heavy presumption that “MAC 
20 AZURE NETWORKS, LLC v. CSR PLC

address” carries its well-established meaning in the 

relevant industry has not been overcome here. 

The parties do not meaningfully dispute the ordinary 

and customary meaning of a “Media Access Control” or 

“Medium Access Control” address (commonly referred to 

as a MAC address) to the relevant community at the time 

of invention. MAC addresses have long been used to 

identify various wireless devices. Industry literature and 

dictionaries at the time of invention, which are not disputed, consistently define MAC addresses as unique 

identifiers. For example, the dictionary of the Institute of 

Electrical and Electronic Engineers (IEEE) defined “MAC 

address” as “[a]n address that identifies a particular 

medium access control (MAC) sublayer service access 

point (SAP).” THE NEW IEEE STANDARD DICTIONARY OF 

ELECTRICAL AND ELECTRONICS TERMS 755 (5th ed. 1993); 

STEVEN M. KAPLAN, WILEY ELECTRICAL & ELECTRONICS 

ENGINEERING DICTIONARY 459 (John Wiley & Sons 2004) 

(defining MAC address as “Media Access Control address,” that is, “a hardware address which uniquely

identifies each physical connection”). The Appellees’ own 

construction acknowledges that MAC addresses are 

“device identifiers.”

The claims use “MAC address” consistently with the 

well-understood industry meaning: to identify a unique 

device. Claim 2 recites that the “first peripheral device 

identifier is based at least in part on a MAC address of 

the first peripheral device.” Claim 43 recites that the 

“plurality of MAC addresses [are] capable of being used 

for identification in association with the first peripheral 

device.” Nothing in the claims displaces the customary 

meaning of “MAC address.” The specification also refers 

to the term as an identifier for a device. ’129 patent, 

3:60–64 (“The Hub 110 uses MAC addresses to identify 

itself and the PEAs [Personal Electronic Accessory] 120. 

The Hub 110 uses its own MAC address to broadcast to 

all PEAs 120. The Hub 110 might also use MAC address-
AZURE NETWORKS, LLC v. CSR PLC 21

es to identify virtual PEAs within any one physical PEA 

120.”). 

At the time of invention, MAC addresses could be assigned either universally, i.e., the manufacturer of the 

device creates the unique identifier for the device, or 

locally, i.e., a network device, like the hub device of the 

’129 patent, creates the unique identifier for a given 

device, like the peripheral devices in the ’129 patent. J.A. 

1605, IEEE Standard for Local and Metropolitan Area 

Networks: Overview and Architecture 21 (IEEE Mar. 8, 

2002) (within the 48-bit MAC address there is a “Universally or Locally administered (U/L) address bit . . . [which] 

indicates whether the address has been assigned by a local 

or universal administrator”) (emphasis added).4 The 

4 See, e.g., FRANK HARGRAVE, HARGRAVE’S 

COMMC’NS DICTIONARY 313 (IEEE Press 2001) (defining 

MAC as an “acronym for Medium Access Control” and 

MAC address as a “48 bit number unique to each network 

interface card (NIC). Generally, the number is programmed into the NIC at the time of manufacture; hence, 

it is LAN and location independent. . . . Also called a 

hardware address, MAC name, physical address, or 

universal address.”) (emphasis added); NEWTON’S 

TELECOM DICTIONARY 450 (CMP Books Feb. 2002) (equating MAC address with Medium Access Control Address

and defining as “a 48-bit number, formally known as an 

EUI-48 (Extended Unique Identifier-48) . . . . The MAC 

Address is programmed into the card, usually at the time 

of manufacture”) (emphasis added). From these references, the dissent gleans inconsistent definitions, which 

do not exist. See Dissenting Op. 5–6. That MAC addresses were usually programmed into a device at the time of 

manufacture means that sometimes they were not. The 

IEEE Standard for Local and Metropolitan Area Networks specification simply buttresses that point. The 

 
22 AZURE NETWORKS, LLC v. CSR PLC

relevant dispute here is whether the claimed “MAC 

address” should be read narrowly, as a device identifier 

that can only be generated locally by the hub device, 

thereby excluding the “universal” type MAC address 

created by the manufacturer of the device. We see no 

reason to limit this established term of art to only hubgenerated addresses. The claims of the ’129 patent do not 

specify whether the “MAC address” is generated locally or 

universally. The specification refers to the phrase “Media 

Access (MAC) address,” and not “Media Access Control

(MAC) address.” Based on this single reference, the 

district court concluded that the patentee “coin[ed] a new 

term” distinct from a standard MAC address, which in 

turn was limited to hub-generated addresses. Azure, 2013 

WL 173788, at *4. We disagree. For a patentee to act as 

his own lexicographer and give a term something other 

than its well-established meaning, he must “clearly set 

forth a definition of the disputed term.” CCS Fitness, Inc. 

v. Brunswick Corp., 288 F.3d 1359, 1366 (Fed. Cir. 2002). 

The lexicography must appear with “reasonable clarity, 

deliberateness, and precision sufficient to narrow the 

definition of the claim term in the manner urged.” Abbott 

Labs. v. Syntron Bioresearch, Inc., 334 F.3d 1343, 1355 

(Fed. Cir. 2003). 

Through the single, cursory use of “Media Access 

(MAC) address”—dropping the word “Control”—the 

specification did not re-coin an established term of art by 

redefining it to have a narrower definition than the traditional MAC address. Dropping the word “Control” was 

prior art cited on the face of the ’129 patent uses MAC 

addresses consistently with the IEEE specification, as 

either universal or local addresses. See, e.g., PCT Application WO 00/68811, 5:7–10 (published Nov. 16, 2000) 

(describing a universal MAC address); U.S. Patent No. 

6,570,857, 4:30–35 (describing a local MAC address).

 
AZURE NETWORKS, LLC v. CSR PLC 23

not unknown to those of ordinary skill in the art, based on 

other technical literature. See, e.g., J.A. 1970–71, SUSAN 

YOUNG & DAVE AITEL, THE HACKER’S HANDBOOK, THE 

STRATEGY BEHIND BREAKING INTO AND DEFENDING 

NETWORKS (CRC Press 2004) (referring to “Media Access 

(MAC) address” as a “unique address assigned to a networking device upon its creation by the manufacturer”); 

J.A. 1978, Implementing QoS, available at

http://vonage.nmhoy.net/qos.html (last visited Oct. 7, 

2014) (“MAC Address prioritizes network devices by their 

Media ACcess Address (MAC Address).”). This one indicium therefore is simply not a strong enough suggestion 

that the inventor intended to displace a well-established 

term of art. See Ancora Techs., Inc. v. Apple, Inc., 744 

F.3d 732, 738 (Fed. Cir. 2014) (holding that specification 

does not set out redefinition for “volatile memory” term 

and its clear ordinary meaning cannot be overcome “by a 

few passing references that do not amount to a redefinition or disclaimer”). This is especially so because “MAC 

address” has a “clear, settled, and objective” meaning to a 

person of ordinary skill in the art. See id. at 737 (finding 

that term “volatile memory” has a “clear, settled, and 

objective” meaning that leaves relevant public with firm 

understanding of scope “unless something exceptional 

sufficiently supplants that understanding”). And when 

read in context, it becomes clear that that “Media Access 

(MAC) address” in the specification has the same meaning 

as that of a traditional MAC address: it is a device identifier. ’129 patent, 3:31–32 (“Each device is identified by a 

Media Access (MAC) address.”) (emphasis added). 

In reading the hub-generation-only limitation into the 

claims, the district court also pointed to the parts of the 

specification referring to the hub device generating and 

assigning the newly coined “MAC address” to the peripheral devices. Azure, 2013 WL 173788, at *4–5; see, e.g.,

’129 patent, 11:2–3 (“The Hub 110 then assigns a MAC 

address to the PEA . . . .”). Failing to find a reference in 
24 AZURE NETWORKS, LLC v. CSR PLC

the specification to manufacturer-generated MAC addresses, it concluded that the claimed “MAC address” 

must be hub-generated. 

Although there is no specific reference to universally 

generated MAC addresses in the specification, using a 

term the same way in all disclosed embodiments is not by 

itself sufficient to redefine a term of art. See Aventis 

Pharma S.A. v. Hospira, Inc., 675 F.3d 1324, 1330 (Fed. 

Cir. 2012); CCS Fitness, 288 F.3d at 1366. The specification “must have sufficient clarity to put one reasonably 

skilled in the art on notice that the inventor intended to 

redefine the claim term.” Merck & Co. v. Teva Pharms. 

USA, Inc., 395 F.3d 1364, 1370 (Fed. Cir. 2005); see also 

Innova/Pure Water, Inc. v. Safari Water Filtration Sys., 

381 F.3d 1111, 1117 (Fed. Cir. 2004) (“[E]ven where a 

patent describes only a single embodiment, claims will not 

be read restrictively unless the patentee has demonstrated a clear intention to limit the claim scope.”) (internal 

quotation omitted). 

The statements in the specification relied upon by the 

district court neither define “MAC address” nor exclude 

universal addresses. The specification does not state that 

a hub-generated MAC address is the actual invention 

itself or that hub-generation is a critical feature. See 

SunRace Roots Enter. Co. v. SRAM Corp., 336 F.3d 1298, 

1305 (Fed. Cir. 2003) (discussing cases limiting claim 

language because feature “described as essential to the 

invention” but declining to do so when the specification 

“does not state that the cam is the actual invention itself”). 

Moreover, nothing in the specification or the prosecution history shows an attempt to distinguish over prior art 

for lacking a hub-generated MAC address. See SciMed 

Life Sys., Inc. v. Advanced Cardiovascular Sys., Inc., 242 
AZURE NETWORKS, LLC v. CSR PLC 25

F.3d 1337, 1343–44 (Fed. Cir. 2001); Alloc, Inc. v. Int’l 

Trade Comm’n, 342 F.3d 1361, 1371 (Fed. Cir. 2003).5

For these reasons, we adopt Azure’s proposed construction of “MAC address” as “an address that uniquely 

identifies a device or group of devices on a shared communication medium.” Accordingly, we vacate the judgment of noninfringement and remand for further 

proceedings, consistent with this opinion.

AFFIRMED-IN-PART, VACATED-IN-PART, AND 

REMANDED

COSTS

Each party shall bear their own costs. 

5 The district court’s construction would also result 

in the hub device generating its own MAC address, in 

addition to generating the MAC addresses for the peripheral devices. Although the specification discusses embodiments where the hub generates the MAC address for 

each peripheral device, it is entirely silent on the source of 

the hub device’s own MAC address. 

 
United States Court of Appeals 

for the Federal Circuit ______________________ 

AZURE NETWORKS, LLC AND

TRI-COUNTY EXCELSIOR FOUNDATION,

Plaintiffs-Appellants,

v.

CSR PLC AND CAMBRIDGE SILICON RADIO 

INTERNATIONAL, LLC,

Defendants-Appellees,

AND

ATHEROS COMMUNICATIONS, INC. AND

QUALCOMM INCORPORATED,

Defendants-Appellees,

AND

BROADCOM CORPORATION,

Defendant-Appellee,

AND

MARVELL SEMICONDUCTOR, INC.,

RALINK TECHNOLOGY CORPORATION (Taiwan) 

AND RALINK TECHNOLOGY CORPORATION 

(USA),

Defendants-Appellees.

_____________________ 

2013-1459

______________________ 
2 AZURE NETWORKS, LLC v. CSR PLC

MAYER, Circuit Judge, dissenting-in-part.

I agree with the court’s thorough and well-reasoned 

analysis of the standing question, but respectfully dissent 

from Section II of the court’s opinion. The specification of 

U.S. Patent No. 7,756,129 (the “’129 patent”) repeatedly 

and unambiguously indicates that the term “Media Access 

(MAC) address” refers to an address that is assigned to a 

peripheral device by a hub device. The patent neither 

contemplates nor enables any other method of network 

communication. The court offers no plausible justification 

for disregarding the unequivocal disclosure in the specification and dramatically expanding the definition of 

“Media Access address” to cover any address that uniquely identifies a device on a shared communication system. 

The decision to jettison the trial court’s claim construction 

is predicated almost exclusively on a purported industry 

definition of the term “Media Access Control address,” but 

that term is found nowhere in the ’129 patent.

I.

Over and over again, the ’129 patent makes clear that 

a “Media Access (MAC) address” is an address assigned to 

a peripheral device by a hub device. The patent explains 

that “a single [h]ub device” communicates with multiple 

peripheral devices, id. col.3 l.28, and “orchestrates all 

communication in the [Personal Area Network],” id. col.3 

l.33. Each peripheral device is assigned a “Media Access 

(MAC) address,” id. col.3 l.32, by the hub device when it 

becomes part of the communications network, id. col.11 

ll.50-52. The Summary of the Invention describes a single 

method by which peripheral devices are attached to the 

network, a method that requires that the hub device 

assign a Media Access address to each peripheral device. 

Id. col.1 ll.57-61 (explaining that “[t]he unattached peripheral device . . . receives a new address from the hub 

device . . . and communicates with the hub device using 

the new address”); id. col.2 ll.8-14 (explaining that the 
AZURE NETWORKS, LLC v. CSR PLC 3

unattached peripheral device “receiv[es] a new address 

from the hub device” and is “attach[ed] to the network 

using the new address”). The specification goes on to 

repeatedly describe a system in which the hub device 

assigns an address to each peripheral device. Id. col.11 

ll.2-4 (“[T]he [h]ub . . . assigns a MAC address to the 

[peripheral device].”); id. col.11 ll.50-54 (“When the [h]ub 

successfully receives the attach-request from the [peripheral device], it assigns a MAC address to the [peripheral 

device].”); id. col.11 ll.55-60 (“The [h]ub sends the new 

MAC address in an attach-assignment message to the 

now-identified [peripheral device].” (diagram reference 

numbers omitted)); id. col.12 ll.31-34 (“The [peripheral 

device] waits for an attach confirmation from the [h]ub 

using the new MAC address . . . and, upon receiving it, 

sends a final acknowledgement to the [h]ub.” (diagram 

reference numbers omitted)). Without exception, the ’129 

patent uses the term “MAC address” to refer to an address that is generated by the hub device. Nothing in the 

specification contemplates that a Media Access address 

will be assigned to a peripheral device at the time it is 

manufactured. Instead, as the district court correctly 

concluded, “what is defined and consistently disclosed” in 

the ’129 patent “is a MAC address that originates with 

the hub device.” Azure Networks, LLC v. CSR PLC, No. 

11-CV-0139, slip op. at 2 (E.D. Tex. May 17, 2013).

The specification typically provides “the primary 

guide to claim interpretation.” ArcelorMittal France v. AK 

Steel Corp., 700 F.3d 1314, 1320 (Fed. Cir. 2012); see also 

Retractable Techs., Inc. v. Becton, Dickinson & Co., 653 

F.3d 1296, 1305 (Fed. Cir. 2011) (“It is axiomatic that the 

claim construction process entails more than viewing the 

claim language in isolation. Claim language must always 

be read in view of the written description.”). Here, because the specification repeatedly makes clear that the 

term “Media Access (MAC) address” refers to an address 

assigned by a hub device—and discloses no other method 
4 AZURE NETWORKS, LLC v. CSR PLC

for network communication—the court has no warrant to 

vastly expand the term to cover any address that uniquely 

identifies a device on a network. See Saffran v. Johnson 

& Johnson, 712 F.3d 549, 560 (Fed. Cir. 2013) (explaining 

that a claim term should be construed in accordance with 

its “[e]xtensive, consistent usage in the specification”); 

Kinetic Concepts, Inc. v. Blue Sky Med. Grp., Inc., 554 

F.3d 1010, 1019 (Fed. Cir. 2009) (refusing to construe the 

term “wound” to cover fistulae because such a construction would “expand the scope of the claims far beyond 

anything described in the specification”). “Although the 

specification need not present every embodiment or 

permutation of the invention and the claims are not 

limited to the preferred embodiment of the invention, 

neither do the claims enlarge what is patented beyond 

what the inventor has described as the invention.” Netword, LLC v. Centraal Corp., 242 F.3d 1347, 1352 (Fed. 

Cir. 2001) (citation omitted).

II.

Three fundamental errors infect the court’s decision to 

expand the ’129 patent to cover an invention that the 

patentees neither claimed nor described. First, the court 

states that “[t]he parties do not meaningfully dispute the 

ordinary and customary meaning of a ‘Media Access 

Control’ or ‘Medium Access Control’ address (commonly 

referred to as a MAC address) to the relevant community 

at the time of the invention.” Ante at 20. This is incorrect. The Defendants-Appellees vigorously—and persuasively—contend that Azure Networks, LLC (“Azure”) 

never established that, at the time of the claimed invention, there was a standard industry definition of the term 

“MAC address” which necessarily encompassed both 

addresses assigned locally and at the time of manufacture. To the contrary, Azure, in its opening claim construction brief, “cited and quoted two references that 

make clear that one of ordinary skill would understand 

MAC addresses as pre-programmed identifiers, not locally 
AZURE NETWORKS, LLC v. CSR PLC 5

assigned addresses.” Br. of Defendants-Appellees at 39-

40.

Azure’s problem is one of proof. If it wanted to enlarge its claims far beyond anything described in the 

specification, it had the burden of coming forward with 

evidence demonstrating not only that there was a common industry definition of the term “MAC address,” but 

that that definition necessarily encompassed both addresses assigned at the time of manufacture and by a 

local network. The simple fact, however, is that Azure 

failed to adduce any such evidence. Indeed, its references 

provide divergent definitions of the term. Azure relies 

heavily on an Institute of Electrical and Electronics 

Engineers (“IEEE”) specification which indicates that 

MAC addresses can be assigned either locally or at the 

time of manufacture. See J.A. 1604-07. Other references 

Azure provided to the trial court, however, indicate that a 

MAC address is typically a 48-bit number assigned to a 

network interface card at the time of manufacture, not an 

address assigned to a peripheral device by a local hub 

device as described in the ’129 patent. See HARGRAVE’S 

COMMC’NS DICTIONARY 313 (2001) (A “MAC address” is

“[a] 48-bit number unique to each network interface card 

(NIC). Generally, the number is programmed into the 

NIC at the time of manufacture; hence, it is LAN and 

location independent.” (emphasis added)); NEWTON’S 

TELECOM DICTIONARY 450 (2002) (A “MAC address” is a 

“Medium Access Control Address” or a “MAC name” that 

“traditionally is in the form of a 48-bit number, formerly 

known as an EUI-48 (Extended Unique Indentifier-48), 

which is unique to each LAN (Local Area Network) NIC 

(Network Interface Card). The MAC address is programmed into the card, usually at the time of manufacture.” (emphasis added)). The fact that Azure’s own 

references provide inconsistent definitions of the term 

“MAC address” belies its contention that there was a 

“standard industry definition,” Br. of Plaintiffs-Appellants 
6 AZURE NETWORKS, LLC v. CSR PLC

at 43, of the term sufficient to overcome its “[e]xtensive, 

consistent usage,” Saffran, 712 F.3d at 560, in the specification. See Renishaw PLC v. Marposs Societa’ Per Azioni, 

158 F.3d 1243, 1250 (Fed. Cir. 1998) (emphasizing that “a 

common meaning, such as one expressed in a relevant 

dictionary, that flies in the face of the patent disclosure is 

undeserving of fealty”).

Apparently recognizing that Azure’s claim construction argument rests on a very feeble evidentiary foundation, the court creates out of whole cloth its own definition 

of “Media Access address.” In the court’s view, a Media 

Access address is anything that identifies a device on a 

network, and it has ferreted out two dictionary definitions 

that it believes support its definition of the term. See ante 

at 20. These dictionary definitions are not part of the 

record, however, and the Defendants-Appellees have had 

no opportunity to challenge them. Even more fundamentally, the one cited definition that could even arguably 

support this court’s exceedingly broad claim construction—the one stating that a “Media Access Control address” is “a hardware address which uniquely identifies 

each physical connection,” ante at 20—pertains to a term 

found nowhere in the ’129 patent.

Language matters. The definition upon which the 

court’s claim construction is predicated is a definition of a 

“Media Access Control address,” not a “Media Access 

address,” the term used in the ’129 patent. See ’129 

patent col.3 ll.31-32 (“Each device is identified by a Media 

Access (MAC) address.”). The fact that the patentees 

dropped the word “control” from their definition of the 

acronym “MAC” is highly significant. It indicates that 

they were not relying on any purported industry definition of the acronym, but were instead using the term 

“Media Access (MAC) address” consistently with the 

disclosure in the specification to refer to an address 

assigned to a peripheral device by a hub device.
AZURE NETWORKS, LLC v. CSR PLC 7

Indeed, any doubt as to whether the meaning of the 

term “MAC address” as used in the ’129 patent was 

intended to be different from any purported industry 

understanding of the term is resolved by reference to 

documents the inventors themselves provided. The ’129 

patent was developed in the course of the inventors’ work 

on a project known as “BodyLAN.” On six separate occasions, the BodyLAN specification uses the phrase “Media 

ACcess,” capitalizing both the “A” and the first “C” in 

“Access.” See J.A. 1664, 1686, 1691, 1701. The fact that 

the inventors capitalized the “M,” the “A,” and the “C,” in 

the term “Media ACcess” indicates that the letter “C” in 

the acronym “MAC” refers to the second letter in the word 

“access” and not to the word “control” in a media access

control address. See Computer Docking Station Corp. v. 

Dell, Inc., 519 F.3d 1366, 1374 (Fed. Cir. 2008) (emphasizing that “repeated and definitive remarks in the written 

description” can restrict a particular claim term); Renishaw, 158 F.3d at 1250 (“[W]here there are several 

common meanings for a claim term, the patent disclosure 

serves to point away from the improper meanings and 

toward the proper meaning.”). Significantly, the 

BodyLAN specification, just like the specification of the 

’129 patent, makes clear that a “Media ACcess” address 

originates with the hub device. See J.A. 1701. 

Finally, even assuming arguendo that the term “MAC 

address” is ambiguous and could potentially be construed 

to cover addresses assigned to a device at the time of 

manufacture, such a construction would render the asserted claims invalid. See Free Motion Fitness, Inc. v. 

Cybex Int’l, Inc., 423 F.3d 1343, 1349 n.4 (Fed. Cir. 2005) 

(explaining that a court can “construe claims to preserve 

their validity when after applying all the available tools of 

claim construction . . . the claim is still ambiguous” (citations and internal quotation marks omitted)). The ’129 

patent describes a system in which a hub “orchestrates all 

communication” in the network, ’129 patent col.3 l.33, by 
8 AZURE NETWORKS, LLC v. CSR PLC

creating MAC addresses and assigning them to peripheral 

devices, id. col.11 ll.2-4. The patent does not describe any 

other way for the hub device to perform the attachment 

and communication steps required by the asserted claims. 

It contains no disclosure of how the claimed network 

would function if the hub had to communicate with peripheral devices using unspecified and potentially proprietary addresses which had been assigned to those devices 

at the time of manufacture. To expand the definition of 

MAC address to include addresses assigned at the time of 

manufacture would permit the ’129 patent to encompass a 

network that the inventors neither contemplated nor 

adequately described. See Nautilus, Inc. v. Biosig Instruments, Inc., 134 S. Ct. 2120, 2124 (2014) (“[A] patent 

is invalid for indefiniteness if its claims, read in light of 

the specification delineating the patent, and the prosecution history, fail to inform, with reasonable certainty, 

those skilled in the art about the scope of the invention.”); 

MagSil Corp. v. Hitachi Global Storage Techs., Inc., 687 

F.3d 1377, 1381 (Fed. Cir. 2012) (“The specification must 

contain sufficient disclosure to enable an ordinarily 

skilled artisan to make and use the entire scope of the 

claimed invention at the time of filing.”).

Azure cannot have it both ways. If the term “MAC 

address” is properly construed to refer only to addresses 

assigned to peripheral devices by a hub device, then the 

accused products do not infringe. If, on the other hand, 

the term is broadly and unreasonably expanded to cover 

addresses assigned at the time of manufacture, then the 

asserted claims are invalid. See MagSil, 687 F.3d at 1381

(“[A] patentee chooses broad claim language at the peril of 

losing any claim that cannot be enabled across its full 

scope of coverage.”); Liebel–Flarsheim Co. v. Medrad, Inc.,

481 F.3d 1371, 1380 (Fed. Cir. 2007) (“The irony of this 

situation is that [the patentee] successfully pressed to 

have its claims include a jacketless system, but, having 
AZURE NETWORKS, LLC v. CSR PLC 9

won that battle, it then had to show that such a claim was 

fully enabled, a challenge it could not meet.”).