53 research outputs found
Rewritable storage channels with hidden state
Many storage channels admit reading and rewriting of the content at a given
cost. We consider rewritable channels with a hidden state which models the
unknown characteristics of the memory cell. In addition to mitigating the
effect of the write noise, rewrites can help the write controller obtain a
better estimate of the hidden state. The paper has two contributions. The first
is a lower bound on the capacity of a general rewritable channel with hidden
state. The lower bound is obtained using a coding scheme that combines
Gelfand-Pinsker coding with superposition coding. The rewritable AWGN channel
is discussed as an example. The second contribution is a simple coding scheme
for a rewritable channel where the write noise and hidden state are both
uniformly distributed. It is shown that this scheme is asymptotically optimal
as the number of rewrites gets large
A Tutorial on Coding Methods for DNA-based Molecular Communications and Storage
Exponential increase of data has motivated advances of data storage
technologies. As a promising storage media, DeoxyriboNucleic Acid (DNA) storage
provides a much higher data density and superior durability, compared with
state-of-the-art media. In this paper, we provide a tutorial on DNA storage and
its role in molecular communications. Firstly, we introduce fundamentals of
DNA-based molecular communications and storage (MCS), discussing the basic
process of performing DNA storage in MCS. Furthermore, we provide tutorials on
how conventional coding schemes that are used in wireless communications can be
applied to DNA-based MCS, along with numerical results. Finally, promising
research directions on DNA-based data storage in molecular communications are
introduced and discussed in this paper
Roadmap on Superoscillations
Superoscillations are band-limited functions with the counterintuitive property that they can vary arbitrarily faster than their fastest Fourier component, over arbitrarily long intervals. Modern studies originated in quantum theory, but there were anticipations in radar and optics. The mathematical understanding—still being explored—recognises that functions are extremely small where they superoscillate; this has implications for information theory. Applications to optical vortices, sub-wavelength microscopy and related areas of nanoscience are now moving from the theoretical and the demonstrative to the practical. This Roadmap surveys all these areas, providing background, current research, and anticipating future developments
Roadmap on superoscillations
Superoscillations are band-limited functions with the counterintuitive property that they can vary arbitrarily faster than their fastest Fourier component, over arbitrarily long intervals. Modern studies originated in quantum theory, but there were anticipations in radar and optics. The mathematical understanding—still being explored—recognises that functions are extremely small where they superoscillate; this has implications for information theory. Applications to optical vortices, sub-wavelength microscopy and related areas of nanoscience are now moving from the theoretical and the demonstrative to the practical. This Roadmap surveys all these areas, providing background, current research, and anticipating future developments
Characterization of laser light propagation in fibers using optical correlation filters
Die Möglichkeit, Licht nahezu verlustfrei auf kleinen Raum zu führen, macht optische Fasern heutzutage zu einer zentralen Schlüsseltechnologie mit vielfältigen Anwendungen in Bereichen wie Lichterzeugung, Telekommunikation oder Sensorik. Dabei setzen aktuelle Entwicklungen verstärkt auf den Einsatz von multimodigen Fasern. Um die sich daraus ergebende Möglichkeit des gleichzeitigen Führens von mehreren individuellen räumlichen Strahlungsverteilungen zu nutzen, ist das Verständnis der modalen Übertragungseigenschaften von Licht in multimodalen Fasern von wesentlicher Bedeutung. Daher werden zuverlässige modenauflösende Charakterisierungsmethoden benötigt. Einen besonders vielseitigeren Ansatz stellt die optische Korrelationsfiltermethode dar. Als ersten wird das Potential dieser Methode bei der Bestimmung der modalen Übertragungseigenschaften für typische schwach führende Fasern aufgezeigt. Zusammen mit Ergebnissen zur Charakterisierung der Kopplung zwischen Freistrahl- und Fasermoden, führte dies zur erstmaligen Realisierung eines passiv kombinierten Faser-Freiraum-Kommunikationskanals. Der zweite wesentliche Fokus dieser Arbeit liegt auf der Überwindung von konzeptionellen Einschränkungen der existierenden Korrelationsfiltermethode. Dabei wird das Anwendungsspektrum der Methode auf die allgemeinen Fälle von partiell kohärente Faserstrahlen sowie hybride Modensätze erweitert. Ermöglicht wird dies durch die Anpassung der Art der verwendeten Filterfunktionen sowie deren Implementation als Filterelement mittels computergenerierter Hologramme und sub-Wellenlängen Gittern. Anhand von ausgewählten Beispielen wird der Nutzen dieser Erweiterungen zur Charakterisierung der modalen Propagationseigenschaften aufgezeigt. Diese Verallgemeinerung des Messkonzepts auf beliebige quasimonochromatische Faserstrahlen unterstreicht insbesondere den universellen Charakter der Korrelationsfiltermethode, was diese anderen, meist auf spezielle Fälle beschränkte Methoden, überlegen macht
Enhanced coding, clock recovery and detection for a magnetic credit card
Merged with duplicate record 10026.1/2299 on 03.04.2017 by CS (TIS)This thesis describes the background, investigation and construction of a system
for storing data on the magnetic stripe of a standard three-inch plastic credit
in: inch card. Investigation shows that the information storage limit within a 3.375 in
by 0.11 in rectangle of the stripe is bounded to about 20 kBytes. Practical issues
limit the data storage to around 300 Bytes with a low raw error rate: a four-fold
density increase over the standard. Removal of the timing jitter (that is prob-'
ably caused by the magnetic medium particle size) would increase the limit to
1500 Bytes with no other system changes. This is enough capacity for either a
small digital passport photograph or a digitized signature: making it possible
to remove printed versions from the surface of the card.
To achieve even these modest gains has required the development of a new
variable rate code that is more resilient to timing errors than other codes in its
efficiency class. The tabulation of the effects of timing errors required the construction
of a new code metric and self-recovering decoders. In addition, a new
method of timing recovery, based on the signal 'snatches' has been invented to
increase the rapidity with which a Bayesian decoder can track the changing velocity
of a hand-swiped card. The timing recovery and Bayesian detector have
been integrated into one computation (software) unit that is self-contained and
can decode a general class of (d, k) constrained codes. Additionally, the unit has
a signal truncation mechanism to alleviate some of the effects of non-linear distortion
that are present when a magnetic card is read with a magneto-resistive
magnetic sensor that has been driven beyond its bias magnetization.
While the storage density is low and the total storage capacity is meagre in
comparison with contemporary storage devices, the high density card may still
have a niche role to play in society. Nevertheless, in the face of the Smart card its
long term outlook is uncertain. However, several areas of coding and detection
under short-duration extreme conditions have brought new decoding methods
to light. The scope of these methods is not limited just to the credit card
Optical investigations of nanostructured oxides and semiconductors
This work is motivated by the prospect of building a quantum computer: a device that would allow physicists to explore quantum mechanics more deeply, and allow everyone else to keep their credit card numbers safe on the internet. In this thesis we explore materials that are relevant to a proposed quantum computer architecture.Systems with a ferroelectric to paraelectric transition in the vicinity of room temperature areuseful for devices. Adjusting the ferroelectric transition temperature is traditionally accomplished by chemical substitution, as in barium strontium titanate. We investigate strained-strontium titanate, which is ferroelectric at room-temperature, and a composite material of barium strontium titanate and magnesium oxide.We present optical techniques to measure electron spin dynamics with GHz dynamical bandwidth,transform-limited spectral selectivity, and phase-sensitive detection. We demonstrate the technique with a measurement of GHz-spin precession in n-GaAs. We also describe our efforts to measure single quantum dots optically.Nanoscale devices with photonic properties have been the subject of intense research over the past decade. Potential nanophotonic applications include communications, polarization-sensitive detectors, and solar power generation. Here we show photosensitivity of a nanoscale detectorwritten at the interface between two oxides
Roadmap on structured light
Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge. This roadmap touches on the key fields within structured light from the perspective of experts in those areas, providing insight into the current state and the challenges their respective fields face. Collectively the roadmap outlines the venerable nature of structured light research and the exciting prospects for the future that are yet to be realized.Peer ReviewedPostprint (published version
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Benchmarking foreign electronics technologies
This report has been drafted in response to a request from the Japanese Technology Evaluation Center`s (JTEC) Panel on Benchmarking Select Technologies. Since April 1991, the Competitive Semiconductor Manufacturing (CSM) Program at the University of California at Berkeley has been engaged in a detailed study of quality, productivity, and competitiveness in semiconductor manufacturing worldwide. The program is a joint activity of the College of Engineering, the Haas School of Business, and the Berkeley Roundtable on the International Economy, under sponsorship of the Alfred P. Sloan Foundation, and with the cooperation of semiconductor producers from Asia, Europe and the United States. Professors David A. Hodges and Robert C. Leachman are the project`s Co-Directors. The present report for JTEC is primarily based on data and analysis drawn from that continuing program. The CSM program is being conducted by faculty, graduate students and research staff from UC Berkeley`s Schools of Engineering and Business, and Department of Economics. Many of the participating firms are represented on the program`s Industry Advisory Board. The Board played an important role in defining the research agenda. A pilot study was conducted in 1991 with the cooperation of three semiconductor plants. The research plan and survey documents were thereby refined. The main phase of the CSM benchmarking study began in mid-1992 and will continue at least through 1997. reports are presented on the manufacture of integrated circuits; data storage; wireless technology; human-machine interfaces; and optoelectronics. Selected papers are indexed separately for inclusion in the Energy Science and Technology Database
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