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1
Tripathy, Shreejoy J. "Understanding the Form and Function of Neuronal Physiological Diversity." Research Showcase @ CMU, 2013. http://repository.cmu.edu/dissertations/318.
Full textAbstract:
For decades electrophysiologists have recorded and characterized the biophysical properties of a rich diversity of neuron types. This diversity of neuron types is critical for generating functionally important patterns of brain activity and implementing neural computations. In this thesis, I developed computational methods towards quantifying neuron diversity and applied these methods for understanding the functional implications of within-type neuron variability and across-type neuron diversity.
First, I developed a means for defining the functional role of differences among neurons of the same type. Namely, I adapted statistical neuron models, termed generalized linear models, to precisely capture how the membranes of individual olfactory bulb mitral cells transform afferent stimuli to spiking responses. I then used computational simulations to construct virtual populations of biophysically variable mitral cells to study the functional implications of within-type neuron variability. I demonstrate that an intermediate amount of intrinsic variability enhances coding of noisy afferent stimuli by groups of biophysically variable mitral cells. These results suggest that within-type neuron variability, long considered to be a disadvantageous consequence of biological imprecision, may serve a functional role in the brain.
Second, I developed a methodology for quantifying the rich electrophysiological diversity across the majority of the neuron types throughout the mammalian brain. Using semi-automated text-mining, I built a database, Neuro- Electro, of neuron type specific biophysical properties extracted from the primary research literature. This data is available at http://neuroelectro.org, which provides a publicly accessible interface where this information can be viewed. Though the extracted physiological data is highly variable across studies, I demonstrate that knowledge of article-specific experimental conditions can significantly explain the observed variance. By applying simple analyses to the dataset, I find that there exist 5-7 major neuron super-classes which segregate on the basis of known functional roles. Moreover, by integrating the NeuroElectro dataset with brain-wide gene expression data from the Allen Brain Atlas, I show that biophysically-based neuron classes correlate highly with patterns of gene expression among voltage gated ion channels and neurotransmitters. Furthermore, this work lays the conceptual and methodological foundations for substantially enhanced data sharing in neurophysiological investigations in the future.
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Romero, Arandia Iñigo. "Reading out neural populations: shared variability, global fluctuations and information processing." Doctoral thesis, Universitat Pompeu Fabra, 2017. http://hdl.handle.net/10803/404684.
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Entendre l'origen i la funció de l'activitat de poblacions neuronals, i
com aquesta activitat es relaciona amb els estímuls sensorials, les decisions
o les accions motores és un gran repte per les neurociències.
En aquest treball hem analitzat l'activitat de desenes de neurones
enregistrades a l'escorça visual primària de micos mentre se'ls presentaven
escletxes sinusoïdals en diferents orientacions. Hem trobat
que les fluctuacions globals de la xarxa mesurades mitjançant l'activitat
de la població modulen la selectivitat de les neurones de forma
multiplicativa i additiva. A més, l'activitat de la població també afecta
la informació present en grups petits de neurones, depenent de la
modulació que ha provocat a la selectivitat d'aquestes. La informació de la població sencera, però, no canvia amb aquestes fluctuacions.
A la segona part hem desenvolupat un mètode per mesurar 'correlacions
diferencials' amb dades limitades. En aplicar-ho a les dades
experimentals hem aconseguit la primera estimació preliminar de la
grandària d'aquestes correlacions que limiten la informació. Els nostres
resultats contribueixen a l'avenç en la comprensió de la codi ficació
d'informació en poblacions neuronals, i alhora generen noves preguntes
sobre com aquestes processen i transmeten informació.Entender el origen y la función de la actividad de poblaciones neuronales, y cómo esta actividad se relaciona con los estímulos sensoriales, las decisiones o las acciones motoras es un gran desafio en neurociencia. En este trabajo hemos analizado la actividad de decenas de neuronas registradas en la corteza visual primaria de monos mientras rejillas sinusoidales en diferentes orientaciones eran presentadas. Hemos encontrado que las fluctuaciones globales de la red medidas mediante la actividad de la población modulan la selectividad de las neuronas de manera multiplicativa y aditiva. Además, la actividad de la población también afecta a la información presente en grupos pequeños de neuronas, dependiendo de la modulación que ha provocado en la selectividad de estas neuronas. La información en la población completa, sin embargo, no varía con estas fluctuaciones. En la segunda parte hemos desarrollado un método para medir 'correlaciones diferenciales' con datos limitados. Al aplicarlo a los datos experimentales hemos obtenido la primera estimación preliminar del tamaño de estas correlaciones que limitan la información. Nuestros resultados contribuyen al avance del entendimiento sobre la codi ficación de la información en poblaciones neuronales, y al mismo tiempo generan más preguntas sobre cómo éstas procesan y transmiten información.
Understanding the sources and the role of the spiking activity of neural populations, and how this activity is related to sensory stimuli, decisions or motor actions is a crucial challenge in neuroscience. In this work, we analyzed the spiking activity of tens of neurons recorded in the primary visual cortex of macaque monkeys while drifting sinusoidal gratings were presented in di erent orientations. We found that global uctuations of the network measured by the population activity a ect the tuning of individual neurons both multiplicatively and additively. Population activity also has an impact in the information of small ensembles, which depends on the kind of modulation that the tuning of those neurons undergoes. Interestingly, the total information of the network is not altered by these uctuations. In the second part, we developed a method to measure 'di erential correlations' from limited amount of data, and obtained the rst, although preliminary, estimate in experimental data. Our results have important implications for information coding, and they open new questions about the way information is processed and transmitted by the spiking activity of neural populations.
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Iwaza, Lana, and Lana Iwaza. "Joint Source-Network Coding & Decoding." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00855787.
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While network data transmission was traditionally accomplished via routing, network coding (NC) broke this rule by allowing network nodes to perform linear combinations of the upcoming data packets. Network operations are performed in a specific Galois field of fixed size q. Decoding only involves a Gaussian elimination with the received network-coded packets. However, in practical wireless environments, NC might be susceptible to transmission errors caused by noise, fading, or interference. This drawback is quite problematic for real-time applications, such as multimediacontent delivery, where timing constraints may lead to the reception of an insufficient number of packets and consequently to difficulties in decoding the transmitted sources. At best, some packets can be recovered, while in the worst case, the receiver is unable to recover any of the transmitted packets.In this thesis, we propose joint source-network coding and decoding schemes in the purpose of providing an approximate reconstruction of the source in situations where perfect decoding is not possible. The main motivation comes from the fact that source redundancy can be exploited at the decoder in order to estimate the transmitted packets, even when some of them are missing. The redundancy can be either natural, i.e, already existing, or artificial, i.e, externally introduced.Regarding artificial redundancy, we choose multiple description coding (MDC) as a way of introducing structured correlation among uncorrelated packets. By combining MDC and NC, we aim to ensure a reconstruction quality that improves gradually with the number of received network-coded packets. We consider two different approaches for generating descriptions. The first technique consists in generating multiple descriptions via a real-valued frame expansion applied at the source before quantization. Data recovery is then achieved via the solution of a mixed integerlinear problem. The second technique uses a correlating transform in some Galois field in order to generate descriptions, and decoding involves a simple Gaussian elimination. Such schemes are particularly interesting for multimedia contents delivery, such as video streaming, where quality increases with the number of received descriptions.Another application of such schemes would be multicasting or broadcasting data towards mobile terminals experiencing different channel conditions. The channel is modeled as a binary symmetric channel (BSC) and we study the effect on the decoding quality for both proposed schemes. Performance comparison with a traditional NC scheme is also provided.Concerning natural redundancy, a typical scenario would be a wireless sensor network, where geographically distributed sources capture spatially correlated measures. We propose a scheme that aims at exploiting this spatial redundancy, and provide an estimation of the transmitted measurement samples via the solution of an integer quadratic problem. The obtained reconstruction quality is compared with the one provided by a classical NC scheme.
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Iwaza, Lana. "Joint Source-Network Coding & Decoding." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112048/document.
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Dans les réseaux traditionnels, la transmission de flux de données s'effectuaient par routage des paquets de la source vers le ou les destinataires. Le codage réseau (NC) permet aux nœuds intermédiaires du réseau d'effectuer des combinaisons linéaires des paquets de données qui arrivent à leurs liens entrants. Les opérations de codage ont lieu dans un corps de Galois de taille finie q. Aux destinataires, le décodage se fait par une élimination de Gauss des paquets codés-réseau reçus. Cependant, dans les réseaux sans fils, le codage réseau doit souvent faire face à des erreurs de transmission causées par le bruit, les effacements, et les interférences. Ceci est particulièrement problématique pour les applications temps réel, telle la transmission de contenus multimédia, où les contraintes en termes de délais d'acheminement peuvent aboutir à la réception d'un nombre insuffisant de paquets, et par conséquent à des difficultés à décoder les paquets transmis. Dans le meilleurs des cas, certains paquets arrivent à être décodés. Dans le pire des cas, aucun paquet ne peut être décodé.Dans cette thèse, nous proposons des schémas de codage conjoint source-réseau dont l'objectif est de fournir une reconstruction approximative de la source, dans des situations où un décodage parfait est impossible. L'idée consiste à exploiter la redondance de la source au niveau du décodeur afin d'estimer les paquets émis, même quand certains de ces paquets sont perdus après avoir subi un codage réseau. La redondance peut être soit naturelle, c'est-à-dire déjà existante, ou introduite de manière artificielle.Concernant la redondance artificielle, le codage à descriptions multiples (MDC) est choisi comme moyen d'introduire de la redondance structurée entre les paquets non corrélés. En combinant le codage à descriptions multiples et le codage réseau, nous cherchons à obtenir une qualité de reconstruction qui s'améliore progressivement avec le nombre de paquets codés-réseau reçus.Nous considérons deux approches différentes pour générer les descriptions. La première approche consiste à générer les descriptions par une expansion sur trame appliquée à la source avant la quantification. La reconstruction de données se fait par la résolution d'un problème d' optimisation quadratique mixte. La seconde technique utilise une matrice de transformée dans un corps de Galois donné, afin de générer les descriptions, et le décodage se fait par une simple éliminationde Gauss. Ces schémas sont particulièrement intéressants dans un contexte de transmission de contenus multimédia, comme le streaming vidéo, où la qualité s'améliore avec le nombre de descriptions reçues.Une seconde application de tels schémas consiste en la diffusion de données vers des terminaux mobiles à travers des canaux de transmission dont les conditions sont variables. Dans ce contexte, nous étudions la qualité de décodage obtenue pour chacun des deux schémas de codage proposés, et nous comparons les résultats obtenus avec ceux fournis par un schéma de codage réseau classique.En ce qui concerne la redondance naturelle, un scénario typique est celui d'un réseau de capteurs, où des sources géographiquement distribuées prélèvent des mesures spatialement corrélées. Nous proposons un schéma dont l'objectif est d'exploiter cette redondance spatiale afin de fournir une estimation des échantillons de mesures transmises par la résolution d'un problème d'optimisation quadratique à variables entières. La qualité de reconstruction est comparée à celle obtenue à travers un décodage réseau classiqueWhile network data transmission was traditionally accomplished via routing, network coding (NC) broke this rule by allowing network nodes to perform linear combinations of the upcoming data packets. Network operations are performed in a specific Galois field of fixed size q. Decoding only involves a Gaussian elimination with the received network-coded packets. However, in practical wireless environments, NC might be susceptible to transmission errors caused by noise, fading, or interference. This drawback is quite problematic for real-time applications, such as multimediacontent delivery, where timing constraints may lead to the reception of an insufficient number of packets and consequently to difficulties in decoding the transmitted sources. At best, some packets can be recovered, while in the worst case, the receiver is unable to recover any of the transmitted packets.In this thesis, we propose joint source-network coding and decoding schemes in the purpose of providing an approximate reconstruction of the source in situations where perfect decoding is not possible. The main motivation comes from the fact that source redundancy can be exploited at the decoder in order to estimate the transmitted packets, even when some of them are missing. The redundancy can be either natural, i.e, already existing, or artificial, i.e, externally introduced.Regarding artificial redundancy, we choose multiple description coding (MDC) as a way of introducing structured correlation among uncorrelated packets. By combining MDC and NC, we aim to ensure a reconstruction quality that improves gradually with the number of received network-coded packets. We consider two different approaches for generating descriptions. The first technique consists in generating multiple descriptions via a real-valued frame expansion applied at the source before quantization. Data recovery is then achieved via the solution of a mixed integerlinear problem. The second technique uses a correlating transform in some Galois field in order to generate descriptions, and decoding involves a simple Gaussian elimination. Such schemes are particularly interesting for multimedia contents delivery, such as video streaming, where quality increases with the number of received descriptions.Another application of such schemes would be multicasting or broadcasting data towards mobile terminals experiencing different channel conditions. The channel is modeled as a binary symmetric channel (BSC) and we study the effect on the decoding quality for both proposed schemes. Performance comparison with a traditional NC scheme is also provided.Concerning natural redundancy, a typical scenario would be a wireless sensor network, where geographically distributed sources capture spatially correlated measures. We propose a scheme that aims at exploiting this spatial redundancy, and provide an estimation of the transmitted measurement samples via the solution of an integer quadratic problem. The obtained reconstruction quality is compared with the one provided by a classical NC scheme
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Mendl, Christian. "Neuronal coding in the retina." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-139015.
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Rossoni, Enrico. "Synchronization and decoding in spiking neuronal networks." Thesis, University of Sussex, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443995.
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姍, 路., and Shan Lu. "Coding and decoding for multiuser communication systems." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12863897/?lang=0, 2014. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12863897/?lang=0.
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本論文は、多端子通信路に対するマルチユーザ符号化および復号の研究成果をまとめたものである。多重接続加算通信路による情報伝送において、複数ユーザの稼働状態を識別するための誤り訂正可能なシグネチャ符号の構成を論ず,全伝送率の高いシグネチャ符号の一般的な構成法を解明する.双方向中継通信路では、2ユーザターボ符号に対する復号の演算量を低減させる復号法を提案する。加法性白色ガウス雑音環境下では復号性能を劣化することなく、レイリーフェージング環境下では僅かな劣化にとどめながら、復号の演算量を約半分程度に低減することができる.Coding and decoding for multiuser communication systems are investigated. For MAAC, we propose a coding scheme of (k + 1)-ary error-correcting signature codes. We give binary and non-binary signature codes. They are the best error-correcting signature codes for MAAC, in the sense that they have highest sum rates known. For TWRC, we propose a low-complexity two-user turbo decoding scheme when turbo codes are applied in two users. The approximate decoding algorithm preserves low decoding complexity over the Gaussian TWRC, without much performance degradation.
博士(工学)
Doctor of Philosophy in Engineering
同志社大学
Doshisha University
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Meyer, Linda. "Coding and Decoding of Reed-Muller Codes." Thesis, Karlstads universitet, Institutionen för matematik och datavetenskap (from 2013), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-84009.
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In this thesis some families of linear error correcting codes are presented. The reader will find a general description of binary codes and more specific details about linear codes such as Hamming, repetition codes, Reed-Muller codes, etc. To fully immerse ourselves in the methods of coding and decoding, we will introduce examples in order to contribute to the understanding of the theories. In these times of much communication through computer technology, our daily lives involve a substantial amount of data transmission. It is essential that these data are transmitted without errors through the communication channels. Therefore, the scientific field of error-correcting codes holds a significant importance in many aspects of todays society. The main goal of this thesis is to study linear block codes which belong to the class of binary codes. In this case we will attribute a more prominent role to first order Reed-Muller codes.I den här uppsatsen kommer flera varianter av linjära felrättande koder att presenteras. Läsaren får ta del av en allmän beskrivning av binära koder och en mer detaljerad framställning av linjära koder så som Hamming, repetitionskod, Reed-Muller kod m.m. Tillsammans med en fördjupning i ämnet, avseende metoder för kodning och avkodning, kommer vi att ge exempel för att bidra till förståelsen. Den digitala eran, som vi lever i, innefattar att datatransmission är en del av vår vardag. Vår frekventa användning av mobila enheter visar på hur viktigt det är att data överförs korrekt via kommunikationskanalerna. Av den anledningen är vetenskapen om felrättande koder högaktuell i dagens samhälle. Det huvudsakliga syftet med uppsatsen är att studera linjära block-koder som tillhör klassen binära koder. I det här fallet kommer vi att fokusera lite extra på Reed-Muller koder av första ordningen.
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Rice, Mark. "Decoding of cyclic block codes." Thesis, University of Manchester, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330207.
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Báez, Mendoza Raymundo. "Neuronal coding of reward during social interactions." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648675.
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Abdulwahid, Khalid. "Optimal decoding for line codes." Thesis, University of Essex, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253980.
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Huluta, Emanuil. "Discrete wavelet transform architecture for image coding and decoding." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/26491.
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This thesis analyses and implements a Discrete Wavelet Transform (DWT) architecture for image processing. The architecture comprises two modules, one for image coding and the other for image decoding. Each module is implemented using a novel Modified Forward-Backward Register Allocation (MFBRA) method and accommodates two Fast Processing Elements (FPE). The resulting architecture minimizes the hardware required to perform the task together with reduced processing time, rendering the whole structure suitable for real time applications. The whole architecture is implemented and simulated using the Verilog Hardware Description Language.
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Al-Rubaie, Alaa Abdulameer Saeed. "Iterative decoding and detection for physical layer network coding." Thesis, University of Newcastle upon Tyne, 2015. http://hdl.handle.net/10443/4062.
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Wireless networks comprising multiple relays are very common and it is important that all users are able to exchange messages via relays in the shortest possible time. A promising technique to achieve this is physical layer network coding (PNC), where the time taken to exchange messages between users is achieved by exploiting the interference at the relay due to the multiple incoming signals from the users. At the relay, the interference is demapped to a binary sequence representing the exclusive-OR of both users' messages. The time to exchange messages is reduced because the relay broadcasts the network coded message to both users, who can then acquire the desired message by applying the exclusive-OR of their original message with the network coded message. However, although PNC can increase throughput it is at the expense of performance degradation due to errors resulting from the demapping of the interference to bits. A number of papers in the literature have investigated PNC with an iterative channel coding scheme in order to improve performance. However, in this thesis the performance of PNC is investigated for end-to-end (E2E) the three most common iterative coding schemes: turbo codes, low-density parity-check (LDPC) codes and trellis bit-interleaved coded modulation with iterative decoding (BICM-ID). It is well known that in most scenarios turbo and LDPC codes perform similarly and can achieve near-Shannon limit performance, whereas BICM-ID does not perform quite as well but has a lower complexity. However, the results in this thesis show that on a two-way relay channel (TWRC) employing PNC, LDPC codes do not perform well and BICM-ID actually outperforms them while also performing comparably with turbo codes. Also presented in this thesis is an extrinsic information transfer (ExIT) chart analysis of the iterative decoders for each coding scheme, which is used to explain this surprising result. Another problem arising from the use of PNC is the transfer of reliable information from the received signal at the relay to the destination nodes. The demapping of the interference to binary bits means that reliability information about the received signal is lost and this results in a significant degradation in performance when applying soft-decision decoding at the destination nodes. This thesis proposes the use of traditional angle modulation (frequency modulation (FM) and phase modulation (PM)) when broadcasting from the relay, where the real and imaginary parts of the complex received symbols at the relay modulate the frequency or phase of a carrier signal, while maintaining a constant envelope. This is important since the complex received values at the relay are more likely to be centred around zero and it undesirable to transmit long sequences of low values due to potential synchronisation problems at the destination nodes. Furthermore, the complex received values, obtained after angle demodulation, are used to derive more reliable log-likelihood ratios (LLRs) of the received symbols at the destination nodes and consequently improve the performance of the iterative decoders for each coding scheme compared with conventionally coded PNC. This thesis makes several important contributions: investigating the performance of different iterative channel coding schemes combined with PNC, presenting an analysis of the behaviour of different iterative decoding algorithms when PNC is employed using ExIT charts, and proposing the use of angle modulation at the relay to transfer reliable information to the destination nodes to improve the performance of the iterative decoding algorithms. The results from this thesis will also be useful for future research projects in the areas of PNC that are currently being addressed, such as synchronisation techniques and receiver design.
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Li, Xiaodong. "Bandwidth-efficient coded modulation and iterative decoding /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/6017.
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Fagervik, Kjetil. "Iterative decoding of concatenated codes." Thesis, University of Surrey, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268307.
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Patel, Ami (Ami M. ). "Effects of neuronal correlations on population decoding and encoding models." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/112429.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis. Thesis pagination reflects the way it was delivered to the Institute Archives and Special Collections, MIT.
Includes bibliographical references (pages 71-73).
In this thesis, we analyze the effect of the correlations in neural activity on the information that is encoded in and can be decoded from a population of neurons. Various noise models describing these correlations are considered - in particular, we use models that take into account the pairwise correlations and other, simpler models that assume shared global additive and/or multiplicative noise factors. The performance of these models on firing rate prediction (encoding) and population decoding are studied. Our analyses show a significant beneficial effect of pairwise correlations on encoding models, with much of this benefit being explained by the global noise models. However, the effects of correlations on decoding vary among our datasets, providing an empirical justification to the theoretical results suggesting correlations can be either helpful or harmful to decoding.
by Ami Patel.
M. Eng.
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Shin, Sooyoung Kim. "Trellis decoding of Reed Solomon codes." Thesis, University of Surrey, 1994. http://epubs.surrey.ac.uk/843410/.
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Reed Solomon codes, a subset of multi-level cyclic block codes with, powerful error-correcting capabilities, are computationally very efficient when algebraic decoding is applied. They may, however, give weaker performance compared to convolutional codes, at least at moderate bit error rates (around 10-5 to 10-6) on the AWGN channel. This disadvantage mainly results from the lack of a generally applicable method for soft decision decoding. Because of easy acceptance of soft decision information, trellis decoders incorporating soft decisions can produce quite useful improvements in coding gain over hard decisions with little increase in complexity. Although trellis methods are commonly used for convolutional codes they can be applied to block codes[23]. In this project, therefore, it is intended to present results of an investigation of soft decision trellis decoding as applied to Reed Solomon codes, and the development of effective decoding algorithms. As a means of maximum likelihood decoding, Viterbi decoding for Reed Solomon codes was attempted. However, the complexity of such a decoder is often prohibitive. In order to reduce the complexity of the Viterbi decoder, an existing reduced search algorithm, which was developed for convolutional codes, was applied to Reed Solomon codes. Moreover, new reduced search methods were developed to enhance its computational efficiency. In contrast to convolutional codes, low rate codes require higher decoder complexity than high rate codes for Viterbi decoding of Reed Solomon codes. For low rate Reed Solomon codes, therefore, the Fano sequential decoding algorithm was investigated, since the complexity of a sequential decoder is independent of the number of encoder memory elements. A simulation model incorporating an AWGN channel has been used to establish the performance of the various suggested decoding algorithms. Importance sampling simulation techniques have been used to reduce simulation time. Simulation results of Viterbi decoding showed that soft decision decoding for the Reed Solomon codes could give at least 2dB coding gain over hard decision decoding on the AWGN channel and that the performance of reduced search, and sequential decoding could approximate that of the Viterbi method with much better computational efficiency. Theoretical decoding performance has been established by using the weight distributions of the codes. Based upon the theoretical results, the simulation results have been analysed. Moreover, the performance and the computational efficiency of each decoding method have been compared, and the advantages and disadvantages of each method indicated. It has been shown that, by using trellis methods, the potential disadvantages of Reed Solomon codes can be removed, and thus the performance of trellis decoded Reed Solomon codes is comparable with that of convolutional codes on the AWGN channel at moderate bit error rate. Therefore, Reed Solomon codes may be used in a wider range of applications, possibly with the decoding method adjusted to the channel conditions.
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Ho, Hai Pang. "Low complexity decoding of cyclic codes." Thesis, University of Surrey, 1998. http://epubs.surrey.ac.uk/844222/.
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This thesis presents three novel low complexity decoding algorithms for Cyclic codes. These algorithms are the Extended Kasami Algorithm (EKA), Permutation Error Trapping (PET) and the Modified Dorsch Algorithm (MDA). The Extended Kasami Algorithm is a novel decoding algorithm combining the Error Trapping Algorithm with cover polynomial techniques. With a revised searching method to locate the best combination of cover positions, the Extended Kasami Algorithm can achieve bounded distance performance with complexity many times lower than other efficient decoding algorithms. In comparison with the Minimum Weight Decoding (MWD) Algorithm on (31,16) BCH codes, the complexity of EKA is only 5% of MWD at 0 dB Eb/No. Comparing EKA with the Kasami Algorithm on the (23,12) Golay code, EKA reduces the complexity consistently for all values of Eb/No. When dealing with Reed Solomon codes, it is found that the additional complexity incurred by finding the error values is a function that increases exponentially with the number of bits in each symbol. To eliminate the problem of finding the error values, Permutation Error Trapping uses a specific cyclic code property to re-shuffle symbol positions. This complements well the Error Trapping approach and most decodable error patterns can be trapped by using this simple approach. PET achieves performance close to that of MWD on the (15,9) RS code with much lower complexity. For more complex codes, like the four-symbol-error correcting (15,7) RS code. Modified Permutation Error Trapping combines part of the cover polynomial approach of EKA with PET resulting in retaining good performance with low complexity. For attempting to decode Reed Solomon codes using soft decision values, the application of a modified Dorsch Algorithm to Reed Solomon codes on various issues has been evaluated. Using a binary form of Reed Solomon codes has been found to be able to achieve near maximum likelihood performance with very few decodings.
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Souvignier, Thomas Victor. "Turbo decoding for partial response channels /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1999. http://wwwlib.umi.com/cr/ucsd/fullcit?p9938584.
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Lopes, Renato da Rocha. "Iterative estimation, equalization and decoding." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/15026.
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Fu, Shengli. "Space-time coding and decoding for MIMO wireless communication systems." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 0.57Mb, 156 p, 2005. http://wwwlib.umi.com/dissertations/fullcit?3182631.
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PHUTATHUM, AWASSADA. "Implementing Distributed Storage Systemsby Network Coding and ConsideringComplexity of Decoding." Thesis, KTH, Kommunikationsteori, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103607.
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Recently, network coding for distributed storage system has become a popular field due to increasing applications such as video, VoIP or mail. There are lots of theoretical works in this field, yet not enough practical study. In this thesis we implement a distributed storage system using network coding. In our implementation, three strategies of coding applied to this system: replication, regenerating code and regenerating code with repair by transfer. To study advantageous or disadvantageous of these strategies, we measure probability of successful downloading, repair time and processing time after implementation. We further study regenerating code with different finite field. Moreover we propose a method for low complexity of decoding algorithm. It is to assign different number of connected storage node which a receiver uses to reconstruct an original file. Our results show that the regenerating code with repair by transfer is an optimal network code for the distributed storage system when comparing to other strategies when working in small finite field size. In particular, in GF(2), the code only uses exclusive-OR to encode and decode data. In addition when finite field is large, the probability of successful downloading increases with the cost of higher complexity comparing to network code with small finite field size. To work in small finite field and consequently reducing complexity in decoding, we show by increasing number of connected node the probability of successful downloading improves. Thus we conclude that the regenerating code with repair by transfer is optimal implementation within system. However if we only consider the regenerating code with different number of connected storage node retrieving the original file, higher number of connected storage node is better than lower number of storage node connected.
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Park, Jong Il. "Trellis based soft output decoding algorithms for concatenated coding systems." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/13898.
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McPheters, Laura L. "Concatenated coding and iterative decoding for magnetic and optical recording." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/16018.
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Liu, Jingjing. "Novel LDPC coding and decoding strategies : design, analysis, and algorithms." Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/3880/.
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In this digital era, modern communication systems play an essential part in nearly every aspect of life, with examples ranging from mobile networks and satellite communications to Internet and data transfer. Unfortunately, all communication systems in a practical setting are noisy, which indicates that we can either improve the physical characteristics of the channel or find a possible systematical solution, i.e. error control coding. The history of error control coding dates back to 1948 when Claude Shannon published his celebrated work “A Mathematical Theory of Communication”, which built a framework for channel coding, source coding and information theory. For the first time, we saw evidence for the existence of channel codes, which enable reliable communication as long as the information rate of the code does not surpass the so-called channel capacity. Nevertheless, in the following 60 years none of the codes have been proven closely to approach the theoretical bound until the arrival of turbo codes and the renaissance of LDPC codes. As a strong contender of turbo codes, the advantages of LDPC codes include parallel implementation of decoding algorithms and, more crucially, graphical construction of codes. However, there are also some drawbacks to LDPC codes, e.g. significant performance degradation due to the presence of short cycles or very high decoding latency. In this thesis, we will focus on the practical realisation of finite-length LDPC codes and devise algorithms to tackle those issues. Firstly, rate-compatible (RC) LDPC codes with short/moderate block lengths are investigated on the basis of optimising the graphical structure of the tanner graph (TG), in order to achieve a variety of code rates (0.1 < R < 0.9) by only using a single encoder-decoder pair. As is widely recognised in the literature, the presence of short cycles considerably reduces the overall performance of LDPC codes which significantly limits their application in communication systems. To reduce the impact of short cycles effectively for different code rates, algorithms for counting short cycles and a graph-related metric called Extrinsic Message Degree (EMD) are applied with the development of the proposed puncturing and extension techniques. A complete set of simulations are carried out to demonstrate that the proposed RC designs can largely minimise the performance loss caused by puncturing or extension. Secondly, at the decoding end, we study novel decoding strategies which compensate for the negative effect of short cycles by reweighting part of the extrinsic messages exchanged between the nodes of a TG. The proposed reweighted belief propagation (BP) algorithms aim to implement efficient decoding, i.e. accurate signal reconstruction and low decoding latency, for LDPC codes via various design methods. A variable factor appearance probability belief propagation (VFAP-BP) algorithm is proposed along with an improved version called a locally-optimized reweighted (LOW)-BP algorithm, both of which can be employed to enhance decoding performance significantly for regular and irregular LDPC codes. More importantly, the optimisation of reweighting parameters only takes place in an offline stage so that no additional computational complexity is required during the real-time decoding process. Lastly, two iterative detection and decoding (IDD) receivers are presented for multiple-input multiple-output (MIMO) systems operating in a spatial multiplexing configuration. QR decomposition (QRD)-type IDD receivers utilise the proposed multiple-feedback (MF)-QRD or variable-M (VM)-QRD detection algorithm with a standard BP decoding algorithm, while knowledge-aided (KA)-type receivers are equipped with a simple soft parallel interference cancellation (PIC) detector and the proposed reweighted BP decoders. In the uncoded scenario, the proposed MF-QRD and VM-QRD algorithms are shown to approach optimal performance, yet require a reduced computational complexity. In the LDPC-coded scenario, simulation results have illustrated that the proposed QRD-type IDD receivers can offer near-optimal performance after a small number of detection/decoding iterations and the proposed KA-type IDD receivers significantly outperform receivers using alternative decoding algorithms, while requiring similar decoding complexity.
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Sivasankaran, Ravi. "Sequential iterative decoding of concatenated recursive systematic convolutional codes." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/13372.
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Kim, Hasung. "Turbo-Like Coding for Spread-Spectrum Communications." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4815.
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This thesis studies advanced error control schemes using turbo-like codes, turbo-like coded modulations, turbo hybrid-ARQ (Automatic Repeat reQuest) schemes, and rate compatible puncturing techniques for reliable and adaptive commercial and tactical spread-spectrum communications, especially for code-division multiple access (CDMA) cellular systems and direct-sequence (DS) and frequency-hopping (FH) anti-jam systems. Furthermore, we utilize both the maximum-likelihood (ML) bounding techniques and convergence analysis to design and analyze various turbo-like coding schemes that show different behaviors in error performance from conventional trellis coding schemes.
In the area of DS-CPM, we propose a DS concatenated coded CPM system for pulse-noise jamming channels and an anti-jam iterative receiver utilizing jammer state information. We also design a mixed concatenated CPM system that mixes CPM schemes with different convergence characteristics. In addition, we present the ML bound and convergence analysis for the jamming channel.
In the area of FH-CPM, we propose anti-jam serially concatenated slow FH-CPM systems, whose phase is continuous during each hop interval, along with coherent and non-coherent iterative receivers. We also propose an iterative jamming estimation technique for the iterative receiver.
In the area of multi-h CPM, we propose a power- and bandwidth-efficient serially concatenated multi-h CPM along with an appropriate iterative receiver structure. Serially concatenated multi-h CPM is shown to outperform single-h CPM.
To design adaptive and versatile error control schemes using turbo-like codes for packet-data networks, we propose turbo hybrid-ARQ (HARQ) and rate compatible puncturing techniques for retransmission.
In the area of turbo hybrid-ARQ, we propose a Type-I turbo HARQ scheme using a concatenated RS-turbo code and a packet combining technique for W-CDMA system to improve the performance of error and decoding latency. The W-CDMA system including the fast power control and coherent Rake receiver with a channel estimation technique for multipath fading channels is considered.
Finally, in the area of rate compatible punctured turbo-like codes, we propose rate compatible punctured turbo (RCPT) codes and rate compatible punctured serially concatenated convolutional (RCPS) codes along with their puncturing methods. In addition, we propose Type-II RCPT-HARQ and RCPS-HARQ schemes to perform an efficient incremental redundancy retransmission.
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Jiang, Jing. "Advanced channel coding techniques using bit-level soft information." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1923.
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Hicks, Matthew Graham. "Applications of acousto-optic demodulation and decoding techniques." Thesis, University of Plymouth, 1997. http://hdl.handle.net/10026.1/2563.
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This thesis describes the operation and performance of an acousto-optic demodulator system consisting of a laser source, an acousto-optic cell and a bi-cell detector. The bi-cell detector is made up of two photodiodes positioned side by side, separated by a small gap. Theory is developed to predict the following; the linear operating range for different gap sizes, absolute frequency sensitivity, system output in response to discrete phase changes, optimum gap size for phase demodulation, absolute descrete phase change sensitivity, the performance of the system in the presence of carrier noise and the effect of clipping the carrier signal on both frequency and phase modulated signals. A detailed model of the system has been written, using the software package Mathcad, which incorporates all the parameters that affect the performance of the physical system. The model has been used to study how the performance of the system changes as these parameters are varied. It is shown that the AO demodulator can be used in a number of ways; as a frequency demodulator, a phase demodulator and to demodulate digitally modulated signals, and that the optimum values of some parameters are different for each application. The model is also used to investigate the response of the system to a number of the most common forms of digital modulation. It is shown that it is possible, without any a priori knowledge of the signal, to identify each of these forms of modulation, and ultimately decode messages contained on the signals. The system can also be used to measure the frequency shift on pulse doppler radar. It is shown that the rms frequency error on a pulse using the AO demodulator is 150% better than that of existing systems. Experimental results are presented that are in good agreement with the results gained from both the theoretical and modelled analysis of the system. Finally suggestions are made for areas of further work on the signal processing of the output signals and possible uses of the demodulator in the future.
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Daniel, J. S. "Synthesis and decoding of array error control codes." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374587.
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Mirza, Javed. "Enhanced Reed Solomon decoding using soft decision information." Thesis, University of Surrey, 1993. http://epubs.surrey.ac.uk/844171/.
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Reed Solomon codes are a well-known family of multilevel codes that are used in a variety of applications where errors are assumed to be bursty in nature. One of its appealing features is that it can correct random errors and mixtures of both random and burst errors. Although the codes meet the Singleton bound with equality they are very inefficient with respect to the Hamming bound, allowing a very high proportion of uncorrectable errors to be detected but not corrected. The algebraic decoding techniques traditionally used suffer the disadvantage that soft decision decoding cannot be achieved in a single decoding attempt, although it is possible to erase symbols of low confidence and allow the decoder to fill the erasures. Since Reed Solomon codes are Maximum Distance Separable (MDS) codes, it is possible to erase any n - k symbols (where n is the length and k the dimension of the code) and still achieve a successful decoding. In this thesis a study is made of an approach in which a large number of erasure patterns of weight 2t are generated and the decodings compared with the received sequence using hard and soft decision voting strategies. In addition, two improvements to the enhanced decoder have been investigated. The first is to compare decoded sequences bit by bit with the received sequence. The second is to incorporate soft decisions. In its most basic form, the enhanced decoder is computationally inefficient, consequently various methods were investigated to overcome this problem. This was also true after reducing the exhaustive erasure pattern set to one which covered all possible combinations of 2t - l error patterns in a reduced erasure pattern set. Alternative algorithms investigated various methods to use the soft decision information to locate the most likely error symbols rather than use exhaustive decoding techniques. Although these algorithms were very efficient in terms of performance and substantially reduced the average computation, in the worst case the computational complexity they generated could exceed that of the exhaustive erasure pattern method. For comparison purposes the error correcting algorithm as proposed by Chase was implemented. It was found that the performance of the enhanced decoder was slightly superior to that of the Chase algorithm but with the added advantage of a reduction in complexity.
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Horley, Niall. "Advanced practical coding and modulation techniques for time varying channels." Thesis, Lancaster University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387440.
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Valenti, Matthew C. "Iterative Detection and Decoding for Wireless Communications." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/28290.
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Turbo codes are a class of forward error correction (FEC) codes that offer energy efficiencies close to the limits predicted by information theory. The features of turbo codes include parallel code concatenation, recursive convolutional encoding, nonuniform interleaving, and an associated iterative decoding algorithm. Although the iterative decoding algorithm has been primarily used for the decoding of turbo codes, it represents a solution to a more general class of estimation problems that can be described as follows: a data set directly or indirectly drives the state transitions of two or more Markov processes; the output of one or more of the Markov processes is observed through noise; based on the observations, the original data set is estimated.
This dissertation specifically describes the process of encoding and decoding turbo codes. In addition, a more general discussion of iterative decoding is presented. Then, several new applications of iterative decoding are proposed and investigated through computer simulation. The new applications solve two categories of problems: the detection of turbo codes over time-varying channels, and the distributed detection of coded multiple-access signals.
Because turbo codes operate at low signal-to-noise ratios, the process of phase estimation and tracking becomes difficult to perform. Additionally, the turbo decoding algorithm requires precise estimates of the channel gain and noise variance. The first significant contribution of this dissertation is a study of several methods of channel estimation suitable specifically for turbo coded systems.
The second significant contribution of this dissertation is a proposed method for jointly detecting coded multiple-access signals using observations from several locations, such as spatially separated base stations. The proposed system architecture draws from the concepts of macrodiversity combining, multiuser detection, and iterative decoding. Simulation results show that when the system is applied to the time division multiple-access cellular uplink, a significant improvement in system capacity results.Ph. D.
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Alzubi, Jafar A. "Forward error correction coding and iterative decoding using algebraic geometric theory." Thesis, Swansea University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582101.
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Tan, Jun. "Iterative decoding and multicarrier modulation for wireless communications." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/13274.
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Bozantzis, Vasilios. "Integrated vector encoding-decoding designs for non-stationary sources and noisy channels." Thesis, University of Sussex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366056.
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Yaxley, S. "Neurophysiological analysis of gustatory coding in the primate." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355810.
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Gittis, Aryn Hilary. "Decoding the ionic basis of neuronal diversity in the medial vestibular nucleus." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3303674.
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Thesis (Ph. D.)--University of California, San Diego, 2008.Title from first page of PDF file (viewed June 18, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Chauvin, Todd Henry. "Interleavers and iterative decoders for turbo codes /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/5947.
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Fayyaz, Ubaid Ullah. "Polar code design and decoding for magnetic recording." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52994.
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Powerful error-correcting codes have enabled a dramatic increase in the bit density on the recording medium of hard-disk drives (HDDs). Error-correcting codes in magnetic recording require a low-complexity decoder and a code design that delivers a target error-rate performance. This dissertation proposes an error-correcting system based on polar codes incorporating a fast, low-complexity, soft-output decoder and a design that is optimized for error-rate performance in the magnetic recording channel. LDPC codes are the state-of-the-art in HDDs, providing the required error-rate performance on high densities at the cost of increased computational complexity of the decoder. Substantial research in LDPC codes has focused on reducing decoder complexity and has resulted in many variants such as quasi-cyclic and convolutional LDPC codes. Polar codes are a recent and important breakthrough in coding theory, as they achieve capacity on a wide spectrum of channels using a low-complexity successive cancellation decoder. Polar codes make a strong case for magnetic recording, because they have low complexity decoders and adequate finite-length error-rate performance. In their current form, polar codes are not feasible for magnetic recording for two reasons. Firstly, there is no low-complexity soft-output decoder available for polar codes that is required for turbo-based equalization of the magnetic recording channel. The only soft-output decoder available to date is a message passing based belief propagation decoder that has very high computational complexity and is not suitable for practical implementations. Secondly, current polar codes are optimized for the AWGN channel only, and may not perform well under turbo-based detector for ISI channels. This thesis delivers a powerful low-complexity error-correcting system based on polar codes for ISI channels. Specifically, we propose a low-complexity soft-output decoder for polar codes that achieves better error-rate performance than the belief propagation decoder for polar codes while drastically reducing the complexity. We further propose a technique for polar code design over ISI channels that outperform codes for the AWGN channel in terms of error rate under the proposed soft-output decoder.
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Benachour, Phillip. "Trellis decoding techniques for the multiple access binary adder channel." Thesis, Lancaster University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314240.
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Akeredolu, P. S. "Some new procedures for generating and decoding error correcting codes." Thesis, De Montfort University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382273.
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Von, Solms Suné. "Design of effective decoding techniques in network coding networks / Suné von Solms." Thesis, North-West University, 2013. http://hdl.handle.net/10394/9544.
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Random linear network coding is widely proposed as the solution for practical network coding
applications due to the robustness to random packet loss, packet delays as well as network topology
and capacity changes. In order to implement random linear network coding in practical scenarios
where the encoding and decoding methods perform efficiently, the computational complex coding
algorithms associated with random linear network coding must be overcome.
This research contributes to the field of practical random linear network coding by presenting
new, low complexity coding algorithms with low decoding delay. In this thesis we contribute to this
research field by building on the current solutions available in the literature through the utilisation
of familiar coding schemes combined with methods from other research areas, as well as developing
innovative coding methods.
We show that by transmitting source symbols in predetermined and constrained patterns from
the source node, the causality of the random linear network coding network can be used to create
structure at the receiver nodes. This structure enables us to introduce an innovative decoding
scheme of low decoding delay. This decoding method also proves to be resilient to the effects of
packet loss on the structure of the received packets. This decoding method shows a low decoding
delay and resilience to packet erasures, that makes it an attractive option for use in multimedia
multicasting.
We show that fountain codes can be implemented in RLNC networks without changing the
complete coding structure of RLNC networks. By implementing an adapted encoding algorithm at
strategic intermediate nodes in the network, the receiver nodes can obtain encoded packets that
approximate the degree distribution of encoded packets required for successful belief propagation
decoding.
Previous work done showed that the redundant packets generated by RLNC networks can be
used for error detection at the receiver nodes. This error detection method can be implemented
without implementing an outer code; thus, it does not require any additional network resources. We
analyse this method and show that this method is only effective for single error detection, not
correction.
In this thesis the current body of knowledge and technology in practical random linear network
coding is extended through the contribution of effective decoding techniques in practical network
coding networks. We present both analytical and simulation results to show that the developed
techniques can render low complexity coding algorithms with low decoding delay in RLNC networks.Thesis (PhD (Computer Engineering))--North-West University, Potchefstroom Campus, 2013
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Zhao, Yuanyi. "Iterative decoding combined with physical-layer network coding on impulsive noise channels." Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3537.
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This thesis investigates the performance of a two-way wireless relay channel (TWRC) employing physical layer network coding (PNC) combined with binary and non-binary error-correcting codes on additive impulsive noise channels. This is a research topic that has received little attention in the research community, but promises to offer very interesting results as well as improved performance over other schemes. The binary channel coding schemes include convolutional codes, turbo codes and trellis bitinterleaved coded modulation with iterative decoding (BICM-ID). Convolutional codes and turbo codes defined in finite fields are also covered due to non-binary channel coding schemes, which is a sparse research area. The impulsive noise channel is based on the well-known Gaussian Mixture Model, which has a mixture constant denoted by α. The performance of PNC combined with the different coding schemes are evaluated with simulation results and verified through the derivation of union bounds for the theoretical bit-error rate (BER). The analyses of the binary iterative codes are presented in the form of extrinsic information transfer (ExIT) charts, which show the behaviour of the iterative decoding algorithms at the relay of a TWRC employing PNC and also the signal-to-noise ratios (SNRs) when the performance converges. It is observed that the non-binary coding schemes outperform the binary coding schemes at low SNRs and then converge at higher SNRs. The coding gain at low SNRs become more significant as the level of impulsiveness increases. It is also observed that the error floor due to the impulsive noise is consistently lower for non-binary codes. There is still great scope for further research into non-binary codes and PNC on different channels, but the results in this thesis have shown that these codes can achieve significant coding gains over binary codes for wireless networks employing PNC, particularly when the channels are harsh.
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Marhenke, Jörg. "On algorithms for coding and decoding algebraic-geometric codes and their implementation." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-65822.
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Blad, Anton. "Early-Decision Decoding of LDPC Codes." Licentiate thesis, Linköping : Department of Electrical Engineering, Linköping University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-17185.
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Huang, Yuheng. "Bit-interleaved coded modulation with iterative decoding for wireless communications /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/5903.
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Abedi, Ali. "Invariance Properties and Performance Evaluation of Bit Decoding Algorithms." Thesis, University of Waterloo, 2004. http://hdl.handle.net/10012/768.
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Certain properties of optimal bitwise APP (A Posteriori Probability) decoding of binary linear block codes are studied. The focus is on the Probability Density Function (pdf) of the bit Log-Likelihood-Ratio (LLR). A general channel model with discrete (not necessarily binary) input and discrete or continuous output is considered. It is proved that under a set of mild conditions on the channel, the pdf of the bit LLR of a specific bit position is independent of the transmitted code-word. It is also shown that the pdf of a given bit LLR, when the corresponding bit takes the values of zero and one, are symmetric with respect to each other (reflection of one another with respect to the vertical axis). In the case of channels with binary inputs, a sufficient condition for two bit positions to have the same pdf is presented. An analytical method for approximate performance evaluation of binary linear block codes using an Additive White Gaussian Noise (AWGN) channel model with Binary Phase Shift Keying (BPSK) modulation is proposed. The pdf of the bit LLR is expressed in terms of the Gram-Charlier series expansion. This expansion requires knowledge of the statistical moments of the bit LLR. An analytical method for calculating these moments which is based on some recursive calculations involving certain weight enumerating functions of the code is introduced. It is proved that the approximation can be as accurate as desired, using enough numbers of terms in the Gram-Charlier series expansion. A new method for the performance evaluation of Turbo-Like Codes is presented. The method is based on estimating the pdf of the bit LLR by using an exponential model. The moment matching method is combined with the maximum entropy principle to estimate the parameters of the new model. A simple method is developed for computing the Probabilities of the Point Estimates (PPE) for the estimated parameters, as well as for the Bit Error Rate (BER). It is demonstrated that this method requires significantly fewer samples than the conventional Monte-Carlo (MC) simulation.
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Escalera, Guerrero Sergio. "Coding and Decoding Design of ECOCs for Multi-class Pattern and Object Recognition." Doctoral thesis, Universitat Autònoma de Barcelona, 2008. http://hdl.handle.net/10803/5789.
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Molts problemes de la vida quotidiana estan plens de decisions multi-classe. En l'àmbit del Reconeixement de Patrons, s'han proposat moltes tècniques d'aprenentatge que treballen sobre problemes de dos classes. No obstant, la extensió de classificadors binaris al cas multi-classe és una tasca complexa. En aquest sentit, Error-Correcting Output Codes (ECOC) han demostrat ser una eina potent per combinar qualsevol nombre de classificadors binaris i així modelar problemes multi-classe. No obstant, encara hi ha molts punts oberts sobre les capacitats del framework d'ECOC. En aquesta tesis, els dos estats principals d'un disseny ECOC són analitzats: la codificació i la decodificació. Es presenten diferents alternatives de dissenys dependents del domini del problema. Aquests dissenys fan ús del coneixement del domini del problema per minimitzar el nombre de classificadors que permeten obtenir un alt rendiment de classificació. Per altra banda, l'anàlisi de la codificació de dissenys d'ECOC es emprada per definir noves regles de decodificació que prenen total avantatja de la informació provinent del pas de la codificació. A més a més, com que classificacions exitoses requereixen rics conjunts de característiques, noves tècniques de detecció/extracció de característiques es presenten i s'avaluen en els nous dissenys d'ECOC. L'avaluació de la nova metodologia es fa sobre diferents bases de dades reals i sintètiques: UCI Machine Learning Repositori, símbols manuscrits, senyals de trànsit provinents de sistemes Mobile Mapping, imatges coronàries d'ultrasò, imatges de la Caltech Repositori i bases de dades de malats de Chagas. Els resultats que es mostren en aquesta tesis mostren que s'obtenen millores de rendiment rellevants tant a la codificació com a la decodificació dels dissenys d'ECOC quan les noves regles són aplicades.Many real problems require multi-class decisions. In the Pattern Recognition field, many techniques have been proposed to deal with the binary problem. However, the extension of many 2-class classifiers to the multi-class case is a hard task. In this sense, Error-Correcting Output Codes (ECOC) demonstrated to be a powerful tool to combine any number of binary classifiers to model multi-class problems. But there are still many open issues about the capabilities of the ECOC framework. In this thesis, the two main stages of an ECOC design are analyzed: the coding and the decoding steps. We present different problem-dependent designs. These designs take advantage of the knowledge of the problem domain to minimize the number of classifiers, obtaining a high classification performance. On the other hand, we analyze the ECOC codification in order to define new decoding rules that take full benefit from the information provided at the coding step. Moreover, as a successful classification requires a rich feature set, new feature detection/extraction techniques are presented and evaluated on the new ECOC designs. The evaluation of the new methodology is performed on different real and synthetic data sets: UCI Machine Learning Repository, handwriting symbols, traffic signs from a Mobile Mapping System, Intravascular Ultrasound images, Caltech Repository data set or Chaga's disease data set. The results of this thesis show that significant performance improvements are obtained on both traditional coding and decoding ECOC designs when the new coding and decoding rules are taken into account.
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Mann, Sarah Edge. "The Original View of Reed-Solomon Coding and the Welch-Berlekamp Decoding Algorithm." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/301533.
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Reed-Solomon codes are a class of maximum distance separable error correcting codes with known fast error correction algorithms. They have been widely used to assure data integrity for stored data on compact discs, DVDs, and in RAID storage systems, for digital communications channels such as DSL internet connections, and for deep space communications on the Voyager mission. The recent explosion of storage needs for "Big Data'' has generated renewed interest in large storage systems with extended error correction capacity. Reed-Solomon codes have been suggested as one potential solution. This dissertation reviews the theory of Reed-Solomon codes from the perspective taken in Reed and Solomon's original paper on them. It then derives the Welch-Berlekamp algorithm for solving certain polynomial equations, and connects this algorithm to the problem of error correction. The discussion is mathematically rigorous, and provides a complete and consistent discussion of the error correction process. Numerous algorithms for encoding, decoding, erasure recovery, error detection, and error correction are provided and their computational cost is analyzed and discussed thus allowing this dissertation to serve as a manual for engineers interested in implementing Reed-Solomon coding.