On Coding and Detection Techniques for Two-Dimensional Magnetic Recording

Edited version embargoed until 15.04.2020 Full version: Access restricted permanently due to 3rd party copyright restrictions. Restriction set on 15/04/2019 by AS, Doctoral CollegeThe areal density growth of magnetic recording systems is fast approaching the superparamagnetic limit for conventional magnetic disks. This is due to the increasing demand for high data storage capacity. Two-dimensional Magnetic Recording (TDMR) is a new technology aimed at increasing the areal density of magnetic recording systems beyond the limit of current disk technology using conventional disk media. However, it relies on advanced coding and signal processing techniques to achieve areal density gains. Current state of the art signal processing for TDMR channel employed iterative decoding with Low Density Parity Check (LDPC) codes, coupled with 2D equalisers and full 2D Maximum Likelihood (ML) detectors. The shortcoming of these algorithms is their computation complexity especially with regards to the ML detectors which is exponential with respect to the number of bits involved. Therefore, robust low-complexity coding, equalisation and detection algorithms are crucial for successful future deployment of the TDMR scheme. This present work is aimed at finding efficient and low-complexity coding, equalisation, detection and decoding techniques for improving the performance of TDMR channel and magnetic recording channel in general. A forward error correction (FEC) scheme of two concatenated single parity bit systems along track separated by an interleaver has been presented for channel with perpendicular magnetic recording (PMR) media. Joint detection decoding algorithm using constrained MAP detector for simultaneous detection and decoding of data with single parity bit system has been proposed. It is shown that using the proposed FEC scheme with the constrained MAP detector/decoder can achieve a gain of up to 3dB over un-coded MAP decoder for 1D interference channel. A further gain of 1.5 dB was achieved by concatenating two interleavers with extra parity bit when data density along track is high. The use of single bit parity code as a run length limited code as well as an error correction code is demonstrated to simplify detection complexity and improve system performance. A low-complexity 2D detection technique for TDMR system with Shingled Magnetic Recording Media (SMR) was also proposed. The technique used the concatenation of 2D MAP detector along track with regular MAP detector across tracks to reduce the complexity order of using full 2D detection from exponential to linear. It is shown that using this technique can improve track density with limited complexity. Two methods of FEC for TDMR channel using two single parity bit systems have been discussed. One using two concatenated single parity bits along track only, separated by a Dithered Relative Prime (DRP) interleaver and the other use the single parity bits in both directions without the DRP interleaver. Consequent to the FEC coding on the channel, a 2D multi-track MAP joint detector decoder has been proposed for simultaneous detection and decoding of the coded single parity bit data. A gain of up to 5dB was achieved using the FEC scheme with the 2D multi-track MAP joint detector decoder over un-coded 2D multi-track MAP detector in TDMR channel. In a situation with high density in both directions, it is shown that FEC coding using two concatenated single parity bits along track separated by DRP interleaver performed better than when the single parity bits are used in both directions without the DRP interleaver.9mobile Nigeri

A NEUROMORPHIC APPROACH TO TACTILE PERCEPTION

Ph.DDOCTOR OF PHILOSOPH

Space station data system analysis/architecture study. Task 2: Options development DR-5. Volume 1: Technology options

The second task in the Space Station Data System (SSDS) Analysis/Architecture Study is the development of an information base that will support the conduct of trade studies and provide sufficient data to make key design/programmatic decisions. This volume identifies the preferred options in the technology category and characterizes these options with respect to performance attributes, constraints, cost, and risk. The technology category includes advanced materials, processes, and techniques that can be used to enhance the implementation of SSDS design structures. The specific areas discussed are mass storage, including space and round on-line storage and off-line storage; man/machine interface; data processing hardware, including flight computers and advanced/fault tolerant computer architectures; and software, including data compression algorithms, on-board high level languages, and software tools. Also discussed are artificial intelligence applications and hard-wire communications

Small business innovation research. Abstracts of 1988 phase 1 awards

Non-proprietary proposal abstracts of Phase 1 Small Business Innovation Research (SBIR) projects supported by NASA are presented. Projects in the fields of aeronautical propulsion, aerodynamics, acoustics, aircraft systems, materials and structures, teleoperators and robots, computer sciences, information systems, data processing, spacecraft propulsion, bioastronautics, satellite communication, and space processing are covered

MediaSync: Handbook on Multimedia Synchronization

This book provides an approachable overview of the most recent advances in the fascinating field of media synchronization (mediasync), gathering contributions from the most representative and influential experts. Understanding the challenges of this field in the current multi-sensory, multi-device, and multi-protocol world is not an easy task. The book revisits the foundations of mediasync, including theoretical frameworks and models, highlights ongoing research efforts, like hybrid broadband broadcast (HBB) delivery and users' perception modeling (i.e., Quality of Experience or QoE), and paves the way for the future (e.g., towards the deployment of multi-sensory and ultra-realistic experiences). Although many advances around mediasync have been devised and deployed, this area of research is getting renewed attention to overcome remaining challenges in the next-generation (heterogeneous and ubiquitous) media ecosystem. Given the significant advances in this research area, its current relevance and the multiple disciplines it involves, the availability of a reference book on mediasync becomes necessary. This book fills the gap in this context. In particular, it addresses key aspects and reviews the most relevant contributions within the mediasync research space, from different perspectives. Mediasync: Handbook on Multimedia Synchronization is the perfect companion for scholars and practitioners that want to acquire strong knowledge about this research area, and also approach the challenges behind ensuring the best mediated experiences, by providing the adequate synchronization between the media elements that constitute these experiences

Decoding Distributed Neuronal Activity in Extrastriate Cortical Areas for the Visual Prosthetic Applications

Les prothèses visuelles corticales sont planifiées pour restaurer la vision chez les individus non-voyants en appliquant du courant électrique à des sites discrets sur le cortex visuel. À ce jour, la qualité de la vision rapportée dans la littérature est celle d'un petit nombre de phosphènes (percept de spots lumineux spatialement localisés) sans organisation pour générer un percept significatif. Le principal défi consiste à développer des méthodes pour transférer les informations d'une scène visuelle dans un schéma de stimulation compréhensible pour le cerveau. Une connaissance clé pour résoudre ce défi est de comprendre comment les caractéristiques du phosphène (ou en général, les caractéristiques visuelles) sont représentées dans le modèle distribué d'activité neuronale. Une approche pour obtenir ces connaissances consiste à déterminer dans quelle mesure les réponses neuronales bien réparties peuvent détecter les changements dans une caractéristique visuelle spécifique des stimuli. Pour atteindre cet objectif, nous avons étudié la capacité de discrimination des zones corticales extrastriées V4 chez les singes macaques. Ces zones extrastriées ont de petites régions rétinotopiques qui offrent la possibilité d'échantillonner une grande région de l'espace visuel à l'aide de réseaux de microelectrodes standard telles que celles de l'Université d'Utah. Cela aide à construire des prothèses mini-invasives. Notre contribution concerne la résolution spatiale des potentiels de champs locaux (LFP) dans la zone V4 pour déterminer les limites de la capacité des prothèses visuelles à induire des phosphènes à plusieurs positions. Les LFP ont été utilisés car ils représentent une activité neuronale sur une échelle de 400 microns, ce qui est comparable à la propagation de l'effet de microstimulation dans le cortex. La zone visuelle extrastriée V4 contient également une carte rétinotopique de l'espace visuel et offre la possibilité de récupérer l'emplacement des stimuli statiques. Nous avons appliqué la méthode «Support vector machine» (SVM) pour déterminer la capacité des LFP (par rapport aux réponses à plusieurs unités - MUA) à discriminer les réponses (phosphènes) aux stimuli à différentes séparations spatiales. Nous avons constaté que malgré les grandes tailles de champs récepteurs dans V4, les réponses combinées de plusieurs sites étaient capables de discrimination fine et grossière des positions. Nous avons proposé une stratégie de sélection des électrodes basée sur les poids linéaires des décodeurs (en utilisant les valeurs de poids les plus élevées) qui a considérablement réduit le nombre d'électrodes requis pour la discrimination avec une augmentation des performances. L'application de cette stratégie présente l'avantage potentiel de réduire les dommages tissulaires dans les applications réelles. Nous avons conclu que pour un fonctionnement correct des prothèses, la microstimulation électrique devrait générer un schéma d'activité neuronale similaire à l'activité évoquée correspondant à un percept attendu. De plus, lors de la conception d'une prothèse visuelle, les limites de la capacité de discrimination des zones cérébrales implantées doivent être prises en compte. Ces limites peuvent différer pour MUA et LFP.----------ABSTRACT Cortical visual prostheses are intended to restore vision to blind individuals by applying a pattern of electrical currents at discrete sites on the visual cortex. To date, the quality of vision reported in the literature is that of a small number of phosphenes (percept of spatially localized spots of light) with no organization to generate a meaningful percept. The main challenge consists of developing methods to transfer information of a visual scene into a pattern of stimulation that is understandable to the brain. The key to solving this challenge is understanding how phosphene characteristics (or in general, visual characteristics) are represented in a distributed pattern of neural activity. One approach is to determine how well neural responses can detect changes in a specific characteristic of stimuli. To this end, we have studied the discrimination capability of V4 extrastriate cortical area in macaque monkeys. Extrastriate cortical areas have small retinotopic maps that can provide an opportunity to sample a large region of visual space using standard devices such as Utah arrays. Thus, this helps to build minimally invasive prosthetic devices. Our contribution relates to the spatial resolution of local field potentials (LFPs) in area V4 to determine the limits in the capability of visual prosthetic devices in generation of phosphenes in multiple positions. LFPs were used because they represent neural activity over a scale of 400 microns, which is comparable to the spread of microstimulation effects in the cortex. Extrastriate visual area V4 also contains a retinotopic map of visual space and offers an opportunity to recover the location of static stimuli. We applied support vector machines (SVM) to determine the capability of LFPs (compared to multi-unit responses) in discriminating responses to phosphene-like stimuli (probes) located with different spatial separations. We found that despite large receptive field sizes in V4, combined responses from multiple sites were capable of fine and coarse discrimination of positions. We proposed an electrode selection strategy based on the linear weights of the decoder (using the highest weight values) that significantly reduced the number of electrodes required for discrimination, while at the same time, increased performance. Applying this strategy has the potential to reduce tissue damages in real applications. We concluded that for the correct operation of prosthetic devices, electrical microstimulation should generate a pattern of neural activity similar to the evoked activity corresponding to an expected percept. Moreover, in the design of visual prosthesis, limits in the discrimination capability of the implanted brain areas should be taken into account. These limits may differ for MUA and LFP

Technology 2002: The Third National Technology Transfer Conference and Exposition, volume 2

Proceedings from symposia of the Technology 2002 Conference and Exposition, December 1-3, 1992, Baltimore, MD. Volume 2 features 60 papers presented during 30 concurrent sessions