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`UNITED STATES PATENT AND TRADEMARK OFFICE
`____________
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`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
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`____________
`
`APPLE INC.,
`Petitioner,
`
`v.
`
`SPEIR TECHNOLOGIES LTD.,
`Patent Owner
`______________
`
`IPR2022-01512
`Patent No. 7,321,777
`____________
`
`
`DECLARATION OF DR. MARK P. MAHON IN SUPPORT OF PATENT
`OWNER’S RESPONSE
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`Speir Technologies Ltd.
`Ex. 2014 - Page 1
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`TABLE OF CONTENTS
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`I.
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`II.
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`INTRODUCTION ......................................................................................... 1
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`BACKGROUND AND QUALIFICATIONS ............................................... 2
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`LEGAL PRINCIPLES ................................................................................... 7
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`III.
`A. Claim construction ......................................................................................... 7
`B. Burden of Proof ............................................................................................. 8
`C. Anticipation ................................................................................................... 8
`D. Obviousness ................................................................................................... 9
`PERSON OF ORDINARY SKILL IN THE ART ...................................... 10
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`IV.
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`V.
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`THE PETITION’S PROPOSED COMBINATION OF MCCRADY
`AND RAPHAELI ........................................................................................ 11
`A. First Combination Theory ............................................................................ 12
`B. Second Combination Theory ....................................................................... 27
`THE PETITION’S PROPOSED COMBINATION OF ROFHEART
`AND RAPHAELI ........................................................................................ 33
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`VI.
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`Speir Technologies Ltd.
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`I, Mark P. Mahon, Ph.D, hereby declare as follows:
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`I.
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`Introduction
`1.
`I am over the age of eighteen (18) years and otherwise competent to
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`make this declaration.
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`2.
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`I have been retained as an expert witness on behalf of Speir
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`Technologies Ltd. (“Speir”) for the above-captioned inter partes review (“IPR”). I
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`understand that the petition for inter partes review involves U.S. Patent No.
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`7,321,777 (“the ’777 Patent”).
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`3.
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`I make this declaration based on my personal knowledge, educational
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`background and training, consideration of the materials I discuss herein, and my
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`expert opinions.
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`4.
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`I am being compensated at a rate of $475 per hour for my time in this
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`matter. My compensation does not depend on the outcome of this proceeding, and I
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`have no financial interest in its outcome.
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`5.
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`I have been asked to consider whether the claims of the ’777 Patent
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`would have been obvious based on certain prior art references. I have also been
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`asked to consider the state of the art and prior art available as of January 29, 2004,
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`the priority date of the ’777 Patent. Based on the combination of prior art
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`references discussed in the Petition and declaration, it is my opinion that one of
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`ordinary skill in the art would not have found claims 1-25 of the ’777 Patent to
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`have been obvious. My opinions are provided below.
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`6.
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`In preparing this Declaration, I have reviewed and considered the ’777
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`Patent, the ’777 Patent’s prosecution history, the Petition, the declaration of Dr.
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`Zhi Ding submitted in this proceeding, the deposition testimony of Dr. Ding, and
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`each document cited in my declaration.
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`II. Background And Qualifications
`7. My qualifications for forming the opinions given in this declaration
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`are summarized here and are addressed more fully in my curriculum vitae, which is
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`submitted as Exhibit 2014. That exhibit also includes a list of my publications.
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`8.
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`I am a Teaching Professor in the School of Electrical Engineering and
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`Computer Science at Pennsylvania State University, University Park, PA (“Penn
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`State” or “PSU”). I have worked on communication networks (including AMPS,
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`IS-95, CDMA2000, GSM, EDGE, UMTS/WCDMA, LTE, and 5G cellular),
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`distributed sensor networks (distributed governed and autonomous), and computer
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`networks in general since 1988.
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`9.
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`I received my B.S. in Electronics Engineering from the University of
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`Scranton in 1987. I received my M.S. in Electrical Engineering and Ph.D. in
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`Acoustics from Penn State in 1991 and 2001, respectively.
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`10.
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`In 1988, after I received my bachelor’s degree, I joined the Central
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`Intelligence Agency (CIA) while pursuing my M.S. degree at Penn State part-time.
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`My first job at the CIA involved designing and testing systems to automatically
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`capture and characterize telecommunication signals and emissions from various
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`computer networking devices.
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`11.
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`I returned to Penn State in early 1990 to pursue graduate research full-
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`time and complete my M.S. degree. My graduate research work focused on
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`wideband beamforming and adaptive signal processing. After completing my M.S.
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`degree in EE in 1991, I accepted a full-time faculty research position at the
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`Applied Research Lab at PSU, primarily working on classified programs, and
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`began working on diverse radio frequency and acoustic sensor systems including
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`wireless communications and radio frequency (RF) wireless sensor networks for
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`atmospheric sensing, acoustic propagation prediction, acoustic tracking, source
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`localization, and feature extraction. The acoustic tracking and source localization
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`research focused on integrating distributed sensor reports into common track
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`reports of wheeled and tracked vehicles and performing automatic target
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`recognition.
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`12.
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`I began pursuing my Ph.D. part-time in 1993 while continuing my
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`faculty research position. In 1997, as part of my faculty research position, I began
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`working on classified programs focused on mathematical analytical modeling of
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`communication networks and the development of hardware and software systems
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`to test against cellular networks. My role was to develop the algorithms and write
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`the code running on a specially developed embedded system. For this work, I
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`received a letter of recognition as the “genius behind the VELA software
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`algorithms” from the Director of National Reconnaissance Office (NRO) Systems
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`Engineering and Technology Office. As part of this same work, I was extensively
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`involved in protocol and signaling analysis as well as researching model-specific
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`performance and unique functional characteristics associated with individual
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`mobile devices. The work involved testing dozens of handsets from many
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`manufacturers in controlled and real-world environments against network
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`simulators and live operational networks for each research project..
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`13.
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`In 2000 my research extended into utilizing non-orthogonal wavelets
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`for improving detection and localization of cellular handsets from high altitude
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`sensor systems. In 2001, I completed my Ph.D. and my research focused on the
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`utilization of advanced communication signals for wideband characterization and
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`remote sensing of propagation channels.
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`14. Beginning in 2003, I was co-principal investigator and technical lead
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`on a 3 year multi-million-dollar research effort for developing the Global
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`Information Grid (GIG). This project was sponsored by the Secretary of Defense’s
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`Office with a goal of developing a real-time, multi-intelligence (multi-Int) network
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`for collecting, processing, storing, disseminating, and managing information on
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`demand for decision makers including the warfighter, combatant command centers,
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`policy makers, and support personnel and was the largest network-centric warfare
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`project in development at the time. My research team (Ubiquitous Automated
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`Information Manager) focused on building and deploying a scalable application to
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`perform real-time, multi-int data fusion to support every user in the system. This
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`software application was deployed in Combat Operation Centers, Joint Interagency
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`Task Force locations, and on various platforms (mobile and small computing
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`environments) used by various warfighters. The fused data sources included
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`various content management systems, supply chain logistic reports, GPS-based
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`reports, news feeds, backend databases, sensor system reports, and various other
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`broad data sources.
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`15.
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`I have been working on classified projects since 1988. Before 1998,
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`because the work was not deemed highly classified, I was able to publish eight
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`journal and conference papers prior to 2000. Between 1999 and 2015, however, I
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`was allowed to publish only one article in an unclassified symposium and
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`published and presented about a dozen articles in classified settings. This is
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`because during this period, the vast majority of my research was highly classified.
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`As a result, nearly all of my research results were summarized in classified reports
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`and not available to the general public. Further, because the U.S. government owns
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`any intellectual property resulting from the sponsored research work, I did not
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`pursue or file patent applications.
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`16.
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`In 2015, I transferred to the School of Electrical Engineering and
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`Computer Science at Penn State as a teaching faculty member. In that role, I have
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`continued teaching graduate and undergraduate courses, guiding Ph.D. and M.S.
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`students in communication and mobile networking (including LTE and 5G cellular
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`networks), and pursuing research in this and related areas. Since 2015, I have been
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`an author on seven refereed papers as listed in my curriculum vitae.
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`17. Because of my decades of research and my continuing work at Penn
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`State, I have intimate knowledge of communication networks, including the
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`wireless technologies involved in the ’777 Patent and the Petition’s prior art
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`references in this case. I have been highly recognized as an expert in such systems
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`within the research community. I was recognized twice by the National
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`Reconnaissance Office with commendation letters (one is quoted above) for work
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`dealing with the detection and localization of cellular signals in low signal to noise
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`ratio environments. The U.S. government awarded me over $12M in grants
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`between 2003 and 2015 for projects focused on mobile communication devices and
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`networks, in which I served as a Principal Investigator (PI), Co-PI, and/or technical
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`lead.
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`18. Additionally, during my research career, I interacted extensively with
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`computer scientists and engineers responsible for the design, development, and
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`testing of wireless and mobile data networking systems and testbeds. As a research
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`faculty member, I oversaw engineers and computer scientists that executed many
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`joint projects with development organizations. These interactions exposed me to a
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`wide range of computer scientists and engineers working on wireless and cellular
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`technologies. Since 2011, I have been teaching undergraduate and graduate classes
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`in communication and mobile networking and am familiar with the curricula being
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`taught to electrical engineers and computer scientists. The interactions with a wide
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`range of computer scientists and engineers working on telecommunication and
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`wireless network technologies and the familiarity with the classes taught to
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`electrical engineers and computer scientists have allowed me to have a good
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`understanding of the level of skills possessed by a person of ordinary skill in the
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`field of communication networks. My curriculum vitae includes a more detailed
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`summary of my background, experience, and publications, as well as the cases in
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`which I have served as an expert witness.
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`III. Legal Principles
`A. Claim construction
`19.
`I understand that the first step in performing a validity analysis of the
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`patent claims is to interpret the meaning and scope of the claims by construing the
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`terms and phrases found in those claims. I understand that the appropriate
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`construction of a claim term is its ordinary and accustomed meaning as understood
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`by one of ordinary skill in the art at the time of the invention in the context of the
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`entire patent.
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`20.
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`I understand that standard for claim construction in an inter partes
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`review is the same standard as is applied in district court proceedings.
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`21.
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`I understand that a determination of the meaning and scope of the
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`claims is a matter of law. I have been informed that to determine the meaning of
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`the claims, one should consider the intrinsic evidence, which includes the patent’s
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`claims, written description, and prosecution history.
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`B.
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`Burden of Proof
`22.
`I understand that in an inter partes review, the petitioner has the
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`burden of proving unpatentability by a preponderance of the evidence.
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`C. Anticipation
`23.
`I have been instructed by counsel and understand that a reference is
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`anticipated if a single prior art reference discloses each and every claim element,
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`either explicitly or inherently, as arranged in the same way as in the claim. I
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`understand that where even one claim element is not disclosed in a reference, a
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`contention of anticipation fails.
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`24.
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`I further understand that when a reference fails to explicitly disclose a
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`claim element, that reference inherently discloses that element only if the reference
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`must necessarily include the undisclosed claim element.
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`D. Obviousness
`25.
`I have been instructed by counsel and understand that a combination
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`of prior art references may render a claim obvious if, at the time of the invention, a
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`person of ordinary skill in the art would have selected and combined those prior-art
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`elements in the normal course of research and development to yield the claimed
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`invention.
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`26.
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`I understand that in an obviousness analysis, one should consider the
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`Graham factors: the scope and content of the prior art; the differences between the
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`claimed inventions and the prior art; the level of ordinary skill in the art; and
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`certain secondary considerations, identified below. I further understand the
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`obviousness analysis is to be performed on a claim-by-claim basis. I understand
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`that a person of ordinary skill in the art is a person of ordinary creativity, not an
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`automaton.
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`27.
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`I have been instructed by counsel and understand that obviousness
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`requires more than a mere showing that the prior art includes separate references
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`covering each separate limitation in a claim under examination. I understand
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`obviousness requires the additional showing that a person of ordinary skill at the
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`time of the invention would have been motivated to combine those references in a
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`manner that would include all limitations of the challenged claim, and, in making
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`that combination, a person of ordinary skill in the art would have had a reasonable
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`expectation of success.
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`28.
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`I also understand that an obviousness analysis must be conducted with
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`awareness of the distortion caused by hindsight bias and with caution of arguments
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`reliant upon ex post reasoning. For instance, I understand that when considering
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`obviousness, I should put myself in the position of a person of ordinary skill in the
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`field at the time of the invention, rather than considering new information that is
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`known today but was not known before the priority date of the challenged patent.
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`29.
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`In particular, I understand that it is improper to use the challenged
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`patent’s disclosure or invention as a roadmap to find its prior-art components,
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`because such an approach discounts the value of combining various existing
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`features or principles in a new way to achieve a new result.
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`IV. Person of ordinary skill in the art
`30.
`In his declaration, Dr. Ding states that a person of ordinary skill in the
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`art “would have had a Bachelor’s degree in electrical engineering, computer
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`engineering, computer science, or a related field, and 2-3 years of experience in
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`design or development of wireless communication systems/networks including
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`ranging/positioning systems, or the equivalent. Additional graduate education
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`could substitute for professional experience, or significant experience in the field
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`could substitute for formal education.” Ex. 1003 at ¶ 21. The only issue I take with
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`Dr. Ding’s assessment of the level of skill in the art is with respect to the use of
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`degrees in computer engineering and computer science. Candidates for those
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`degrees will not typically encounter the wireless technologies, including signal
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`propagation and processing, at issue in the ’777 Patent and prior art references in
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`this case. I would therefore assert that a person of ordinary skill in the art would
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`have had a Bachelor’s degree in electrical engineering, or a related field, and 2-3
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`years of experience in design or development of wireless communication
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`systems/networks including ranging/positioning systems, or the equivalent.
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`Additional graduate education could substitute for professional experience, or
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`significant experience in the field could substitute for formal education. For
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`purposes of this declaration, I apply this level of skill in the art. I further note that,
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`as of the priority date of the ’777 Patent, January 29, 2004, I was at least at this
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`level of skill.
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`V.
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`The Petition’s Proposed Combination of McCrady and Raphaeli
`31. According to the assertions in the Petition and Dr. Ding’s declaration,
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`a POSITA would be motivated to incorporate Raphaeli’s teachings about
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`averaging propagation delays into McCrady’s system under two combination
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`theories. Under the first theory a “POSITA would have calculated the individual
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`propagation delays (delay estimates) from the “M” ranging message exchanges on
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`various frequencies, and then averaged those delays as taught by Raphael[i].”
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`Petition at 11-13. Under the second theory, “[t]he POSITA would have
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`contemplated the alternative approach of conducting multiple of McCrady’s
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`ranging message exchanges on a single frequency, determining corresponding
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`delays, and averaging those delays as taught by Raphali.” Petition at 13.
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`A.
`First Combination Theory
`32. The first combination theory may be summarized as “average range
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`estimates across carriers.” I address the necessary technical background material
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`and address this “average range estimates across carriers” theory below.
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`33. U.S. Patent No. 6,453,168 (“McCrady”) is directed to “a position
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`location system for determining the position of a mobile communication device,
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`and, more particularly, to a system employing two-way transmission of spread
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`spectrum ranging signals between the mobile communication device and reference
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`communication devices having relatively low accuracy clocks, to rapidly and
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`accurately determine the position of the mobile communication device in the
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`presence of severe multipath interference.” Ex. 1005, 1:9-17.
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`34. McCrady also discloses that the targeted context for the invention is
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`for “rapidly and accurately determin[ing] the physical location of a mobile
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`communications device” for military, emergency response (such as firefighters or
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`medical personnel), and search and rescue. Id., 1:15-16, 1:19-35.
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`35. McCrady further discloses as motivation for the invention that relying
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`on GPS-based satellites or ground transmitters to determine accurate and
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`operational position location of a device may be “severely degraded in the
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`presence of multipath interference.” Id., 1:15-16; see also id. 2:13-16, 3:46-51.
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`Thus, McCrady asserts that an objective of the invention is to “rapidly, reliably,
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`and accurately determine the three-dimensional position of a mobile
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`communication device in a variety of environments… where multipath interference
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`can be great.” Id., 3:54-58. Furthermore, McCrady adds that “another objective of
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`the present invention to minimize the interference caused by multipath signal
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`propagation … thereby providing highly accurate three-dimensional position
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`estimates even under severe multipath conditions.” Id., 3:66–4:3.
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`36. McCrady also states that “with the present invention[] a … device
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`provides accurate, reliable position information within milliseconds … [and] is
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`capable of determining position location to an accuracy of less than one meter in
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`a severe multipath environment.” Id., 6:20-27 (emphasis added). To accomplish
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`its goals with respect to accuracy, McCrady further describes that the system (i)
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`“perform[s] internal delay calibration” in both the master radio and the reference
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`radio to minimize difficult-to-predict internal transmitter and receiver delay
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`variation, id., 10:36-43, 10:64-11:2, 11:40-43; (ii) uses “state of the art spread
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`spectrum chipping rates and bandwidths to reduce multipath interference,” id.,
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`4:10-13, 5:13-17; (iii) performs “[l]eading edge curve fitting [] to accurately locate
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`the leading-edge of an acquisition sequence … to further reduce effect of multipath
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`interference on TOA estimates,” id., 5:17-20; and (iv) uses, “[i]f necessitated by
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`severe multipath, frequency diversity … to orthogonalize multipath
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`interference with respect to direct path signal, wherein an optimal carrier
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`frequency is identified and used to estimate the TOA to minimize the impact
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`of multipath interference” id., 5:22-27 (emphasis added).
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`37. A POSITA reading McCrady’s disclosures would understand that the
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`invention is directed to accurate, reliable, fast, high resolution position localization
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`even in high multipath environments where it discloses, for a high accuracy mode
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`operating in severe multipath conditions, the use of frequency diversity to identify
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`and utilize an optimal carrier frequency to perform the TOA estimation. “On the
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`other hand, if the multipath interference is classified as substantial and the high
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`accuracy (e.g. one meter) mode has been selected, the TOA processor implements
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`a process employing frequency diversity to identify an optimal transmission
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`frequency that minimizes multipath interference.” Id., 14:35-40.
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`38. McCrady discloses that the reference radios or the master radio can
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`declare the need for frequency diversity. When the need for frequency diversity has
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`been declared, “the master radio identifies the set of M carrier frequencies that will
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`be used to transmit a sequence of M outbound ranging messages and M
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`corresponding reply ranging messages (block 102) … These frequencies are
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`referred to as “ping” frequencies, since a rapid succession of M different frequency
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`signals or multiple “pings” are transmitted between the radios in search of an
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`optimal frequency.” Id., 14:46-56 (emphasis added).
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`39. McCrady supports this technical approach by pointing out that
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`“[r]anging performance is best when the carrier phase of the multipath is 90° with
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`respect to the direct path. If this orthogonality condition is met, the direct path and
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`multipath are separated such that the direct path and multipath can be more
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`precisely curve fit with minimal effects for multipath.” Id., 14:60-65. A POSITA
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`would understand McCrady to disclose using frequency diversity to find an
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`optimal frequency as a necessary technical component to achieve the benefits of
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`the invention’s TOA estimation techniques in a multipath environment because
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`“ping frequencies … [are used] to find the frequency that best orthogonalizes the
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`phase of the multipath interference with respect to the direct signal.” Id., 15:8-13..
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`40. A POSITA would understand that multipath “is a problem in which
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`the transmitted information takes more than one path to the receiver, thus
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`producing interference and echoes in the received signal” which in turn leads to
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`time-dispersion of the received signal. Ex. 2008, Adaptive Signal Processing,
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`Widrow and Stearns, at pg. 200. As shown in the annotated figure below, the time-
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`dispersive nature of the received signal is characterized by the impulse response of
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`the channel where the “impulse” is referring to an idealized zero-width transmitted
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`pulse (Dirac-delta function), i.e., how the transmitted signal (impulse) appears in
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`amplitude and phase at the receiver.
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`Ex. 2008, Adaptive Signal Processing, Widrow and Stearns, at pg. 200.
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`41. A POSITA would also understand that the impulse response
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`characterizes the time-response of the channel and is valid for the period of time
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`over which the time and frequency characteristics of the channel are considered to
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`be constant. A POSITA would also understand that the channel impulse response
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`can vary over time due to the changing time and frequency charactetristics of the
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`channel. There are many factors, environmental and otherwise, that will affect the
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`variation of the time and frequency characteristics of the channel over short (and
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`longer) periods of time. Consequently, these factors will affect the period of time
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`over which the time and frequency characteristics of the channel are considered to
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`be constant.
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`42.
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`In a multipath environment, the rapid changes of the amplitude and
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`phase of a received signal over a short time window is known as fading and are the
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`result of multiple signal components arriving via different propagation paths that
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`may add destructively at the receiver. “Small-scale fading, or simply fading, is
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`used to describe the rapid fluctuation of the amplitude of a radio signal over a short
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`period of time or travel distance…Fading is caused by interference between two or
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`more versions of the transmitted signal which arrive at the receiver at slightly
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`different times. These waves, called multipath waves, combine at the receiver to
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`give a resultant signal which can vary widely in amplitude and phase, depending
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`on the distribution of the intensity and relative propagation time of the waves and
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`the bandwidth of the transmitted signal.” Ex. 2009, Wireless Communications
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`Principles & Practices, Rappaport, at pg. 139. The main small-scale fading effects
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`that multipath casues on the received signal are three-fold: (1) rapid changes in
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`signal strength over a short time interval; (2) random frequency modulation due to
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`Doppler shifts on each separate multipath signal; and (3) time dispersion (echoes
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`or apparent time spread as seen in the Widrow and Stearns figure above) caused by
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`relative delays between each multipath propagation component. Id.
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`43. Additionally, it is understood to a POSITA that mobile radio
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`propagation is a complex and varied topic that involves two specific engineering
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`approaches in capturing the characteristics of a given channel. The first is
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`instantaneous measurements. The second is statistical characterization using many
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`time averaged instantaneous measurements of the channel to associate the
`
`channel’s behavior with a statistical model of multipath fading. See Ex. 2010,
`
`Digital Communications Over Fading Channels, A Unified Approach to
`
`Performance Analysis, Simon and Alouini, at pp. 15 – 28, Ex. 2011, Digital
`
`Communications, Fourth Edition, Proakis, at pp. 810–820.
`
`44. With respect to multipath, there are several physical elements of the
`
`propagation channel that create the small-scale fading effects: (i) the multipath
`
`propagation itself which is caused by reflection, refraction, and scattering
`
`occurring in the channel and is due to natural and manmade objects in the channel
`
`as well as other factors; (ii) the relative motion of the transmitter and receiver
`
`which imparts random, time varying frequency modulation (Doppler shifts) onto a
`
`given multipath component; and (iii) the relationship between the bandwidth of the
`
`signal and the bandwidth of channel (coherence bandwidth) which can cause
`
`distortion (but not significant fading) of the transmitted signal if the former is
`18
`
`
`
`
`Speir Technologies Ltd.
`Ex. 2014 - Page 20
`
`
`
`greater than the latter (if, however, the signal bandwidth is less than the channel
`
`bandwidth, the signal distortion will be negligible or minimal, but the amplitude
`
`may vary significantly (fading)). Ex. 2009, Wireless Communications Principles
`
`& Practices, Rappaport, at pp. 140-141. The small-scale fading effects are
`
`summarized in the diagram below:
`
`Id., at pg. 167.
`
`
`
`45. Generally, statistical models help a POSITA to predict the maximum
`
`and minimum fade a signal with a given bandwidth in a given frequency range
`
`might experience under given propagation conditions associated with the channel.
`
`However, for specific challenging channel conditions (channel model), a POSITA
`
`would have to rely on several signal processing methods to improve the reception
`
`quality, i.e., the likelihood of detecting the transmitted signal, in these challenging
`
`conditions. “Mobile Communication systems require signal processing techniques
`
`
`
`
`19
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`Speir Technologies Ltd.
`Ex. 2014 - Page 21
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`
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`that improve the link performance in hostile mobile radio environments.” Id., at pg.
`
`299. “Equalization, diversity, and channel coding are three techniques which can
`
`be used independently or in tandem to improve received signal quality.” Id. As to
`
`the first, an equalizer can be used in a receiver to compensate for signal distortion
`
`(spreading in time) to mitigate intersymbol interference (the overlap of the
`
`received symbols due to the time spreading of individual symbols). As to the
`
`second, spatial, time, and frequency diversity are techniques employing multiple
`
`antennas, multiple separate transmissions of the same signal, and more than one
`
`carrier respectively. As to the third, channel coding typically brings to bear
`
`convolutional codes to assist in correcting detected bit errors at the receiver. See,
`
`e.g., Ex. 1006, Raphaeli, 19:1-10.
`
`46. A POSITA would therefore have been aware that to mitigate
`
`multipath fading, “[o]ne method is to employ frequency diversity. That is, the same
`
`information bearing signal is transmitted on L carriers, where the separation
`
`between successive carriers equals or exceeds the coherence bandwidth (Δf)c of the
`
`channel.” Ex. 2011, Digital Communications, Proakis, at pg. 821. Systems using
`
`this frequency diversity technique will implement what is known as “protection
`
`switching,” where if one of the carriers being utilized is experiencing a deep fade,
`
`the system will switch over to using another carrier offset by more than the known
`
`coherence bandwidth of the channel. See Ex. 2009, Wireless Communications
`20
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`
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`Speir Technologies Ltd.
`Ex. 2014 - Page 22
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`
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`Principles & Practices, Rappaport, at pg. 335, Ex. 2012, Digital Modulation
`
`Techniques, Xiong, at pg. 562.
`
`47. A second, well known, “more sophisticated” technique utilizing
`
`frequency diversity is to transmit a signal having a bandwidth much greater than
`
`the coherence bandwidth of the channel. In this case, only one information bearing
`
`signal is transmitted, but across a frequency range known to be wider than the
`
`coherence bandwidth of the channel. “Such a signal with bandwidth W will resolve
`
`the multipath components and, thus, provide the receiver with several
`
`independently fading signal paths.” This approach utilizes a specific receiver
`
`architecture (known as a RAKE receiver) to optimize the system performance. See
`
`Ex. 2011, Digital Communications, Proakis, at pp. 821–822; Ex. 1009, Rofheart,
`
`11:66-12:27. A RAKE receiver involves combining multiple copies of the received
`
`signal to essentially average out statistically independent fades associated with
`
`each multipath component. This is in contrast to the previous frequency diversity
`
`approach discussed above in which the multiple copies of the signal are transmitted
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`on narrower bandwid
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