Forward error correction (FEC) is as one of the key technologies enabling the next-generation high-speed fiber optical communications. In this paper, we propose a rate-adaptive scheme using a class of generalized low-density parity-check (GLDPC) codes with a Hamming code as local code. We show that with the proposed unified GLDPC decoder architecture, a variable net coding gains (NCGs) can be achieved with no error floor at BER down to 10(-15), making it a viable solution in the next-generation high-speed fiber optical communications.

Förekomsten av ohälsa är mer vanligt i byggarbetabranschen än i andra branscher, p.g.a. arbetsolyckor och övriga förhållanden i arbetet. En av de viktiga resurserna till att förebygga skada och upprätthålla hälsa i arbetslivet, är företagshälsovård. Syftet med denna kvalitativa intervjustudie var att beskriva byggarbetares upplevelser om deras arbetshälsa/arbetsmiljö och om vad företagshälsovårdens hälsokontroller har haft för betydelse för deras beteendeförändring.   Fem byggarbetare som genomgått en hälsokontroll via företagshälsovård och åstadkommit en potentiell beteendeförändring som förbättrat hälsan, intervjuades. Den tematiska analysen av intervjuerna resulterade i fyra huvudteman: ”möjliggörande faktorer till en god arbetshälsa i byggarbetarens yrke”, ”begränsade faktorer till god arbetshälsa i byggarbetarens yrke”, ”konkreta resultat av företagshälsovårdens hälsokontroller” och ”fördelarna med företagshälsovårdens hälsofrämjande arbete”. Studiens resultat visar att byggarbetare upplevde sin arbetshälsa/arbetsmiljö som både positivt och negativt. Det positiva med arbetet var den sociala kontakten med kollegor och arbetsgivare och det negativt var arbetsmiljön som bidragit till sämre hälsa p.g.a. av muskuloskeletala skador och stress. Hälsokontroller bidrog till beteendeförändring som kan förebygga sjukdomar bland byggarbetarna.   Hälsokontrollen upplevdes som meningsfull då ett gott bemötande möjliggjorde en beteendeförändring samtidigt som en ökad insikt av att förbättra sin egen hälsa skett, efter negativa provsvar. Vidare forskning behövs om hur byggarbetares arbetshälsa kan förbättras genom företagshälsovårdens insatser. / The incidence of illness among construction workers is higher than average in other industries, because of accidents and other conditions at work. One of the most important resources to prevent injury and maintain health in the workplace, is the occupational health care. The aim of this qualitative study was to describe the construction workers experiences of their occupational health and work environment and about whether occupational health check-ups have had any significance for their behavior change. Five male construction workers who had underwent a health check and after that performed a behavior change, was recruited via an occupational care center. Data was collected by face to face and telefon interviews, that were subsequently transcribed and analysed by thematic analyse. The tematic analyse resulted in four main themes: "enabling factors for good health of the construction workers professional”, ”restricted factors to the good health of the construction worker's occupation", "benefits of occupational health promotion" and "concrete results of occupational health check-ups".   The construction workers experienced their occupational health and work environment as both positive and negative. The positive about work was the social contact with colleagues and employers, the negative was that the work environment contributed to poor health due musculoskeletal of injury and stress. Health check-ups contributed to behavior change and pontential prevention of diseases among construction workers.   The health check-ups was considered as being meaningful and enabled a change in behavior after understanding that they must change their lifestyle to avoid disease. Further research is needed on how to improve construction workers occupational health through occupational health services.

Bakgrund Hotellbranschen står inför utmaningar vad gäller att möta gästens ständigt förändrade förväntningar. För att ligga i framkant i gästerbjudandet satsas mer än någonsin på investeringar i teknologi där implementering av SST är en strategi för att överleva. Detta förändrar gästens roll i servicemötet vilket skapar en osäkerhet angående adoption av SST. Syfte Studiens syfte är att från ett kundperspektiv skapa en djupare förståelse för adoption av självserviceteknologi (SST) genom att identifiera och förstå faktorer som triggar en hotellgästs inställning och användande av SST vid incheckning. Genomförande Med avstamp i en litteraturgenomgång genomfördes en förstudie i form av ostrukturerade intervjuer med hotellgäster i syfte att identifiera triggers. Utifrån förstudien och litteraturgenomgången skapades sedan en enkät som analyserades kvantitativt i programmet SPSS för att med stöd av kvalitativa delar från förstudien besvara studiens forskningsfrågor. Slutsats Hotellgästen har generellt en god inställning till SST vid incheckning vilket förklaras mycket av SSTs förmåga att minska kö och väntan. Gästens behov av mänsklig interaktion har dock visat sig hämma adoptionen. SST vid incheckning anses vara en naturlig utveckling men behovet av interaktion tyder på att gästen inte är riktigt redo för hur teknologins framfart förändrar roller och manus i servicemötet. Istället kan interaktion ske utanför incheckningsmomentet, så länge personal finns tillgänglig på gästens villkor finns goda förutsättningar att öka gästens inställning och därmed användande av SST. / Background The hotel business is facing great challenges meeting the guest’s constantly pivoted expectations. In order to maintain the guest offering attractive, hotels are investing more than ever in technology with SST as a strategy of survival. This changes the customers’ role which makes the customer adoption doubtful. Purpose  The purpose of this study is to create a deeper knowledge for adoption of SST from a customer perspective. This by identify and understand triggers of a hotel guest’s attitude and intention to use SST at the check in. Completion  With support from a literature review, a pre-study in form of unstructured interviews with hotel guests took place in order to identify triggers. With the pre-study and literature review in mind a survey was carried out and later analysed using the software SPSS. The quantitative analysis was supported by qualitative results from the pre-study in order to fulfil the purpose. Conclusion  The hotel guest has in general a good attitude to SST at the check in which is shown to by a large extent be explained by the ability to reduce queue and waiting time. Thus is the guest’s need for interaction a hinder for adoption. SST at the check in is more or less seen as a natural service progress, but the need for interaction implies that the guest is not quite ready for how technology is changing role and script. Instead interaction can take place separated from the check in - as long as personnel is available for interaction on the guest’s own terms there are good chances to increase their attitude and thereby usage of SST.

L’objectif de la thèse est l’étude des codes correcteurs d’erreurs au niveau applicatif (Application Layer – Forward Error Correction, ou AL-FEC) pour les communications par satellite. Dans ce contexte, pendant les deux première années de thèse, nous avons proposé de nouvelles méthodes d’analyse, de construction et d’optimisation des codes à effacements définis par des matrices de parité à faible densité (code LDPC, pour « Low Density Parity Check » en anglais). La troisième année de la thèse a été consacrée à : (1) La suite des études portant sur de nouvelles méthodes de construction des codes LDPC non-binaires. D’une part, nous avons développé un nouvel algorithme (Scheduled-PEG) qui permet d’optimiser la construction des codes LDPC non-binaires pas rapport aux métriques de performance spécifiques à la couche application, notamment dans le cadre des systèmes de diffusion de contenu (broadcasting). D’autre part, nous avons proposé une nouvelle méthode de construction de codes à faible rendement, qui utilise l’image binaire étendue d’un code LDPC non-binaire. Ces études ont fait l’objet de deux publications dans deux conférences internationales : (a) “Scheduled-PEG construction of LDPC codes for Upper-Layer FEC”, International Workshop on Coding and Cryptography, April 2011, Paris, France. (b) “Extended Non-Binary Low-Density Parity-Check Codes over Erase Channels”, IEEE International Symposium on Wireless Communication Systems, November 2011, Aachen, Germany. (2) Une étude portant sur l’analyse asymptotique de codes cluster-LDPC non-binaires. Cette nouvelle classe de codes – introduite récemment (ISIT’2011) – se distingue par ses excellentes propriétés en termes de distance minimale. Notre étude a permis de déterminer de manière analytique la capacité de correction des codes cluster-LDPC non-binaires, aussi bien pour le décodage itératif par propagation de croyances (BP, pour « Belief Propagation ») que pour le décodage par maximum de vraisemblance (ML, pour « Maximum Likelihood »). Ces résultats seront intégrés à une publication scientifique sur les codes cluster-LDPC, en cours de rédaction, qui sera soumise à « IEEE Transactions on Information Theory », avant la fin de l’année 2011. (3) Une étude portant sur une méthode de construction des codes LDPC qui permet de réduire de manière significative le plancher d’erreur (« error floor ») du code, sans dégrader ses performances dans la région de « waterfall ». Ainsi, nous avons proposé la structuration de la matrice de parité du code, de manière à intégrer une partie irrégulière, optimisée pour la partie « waterfall », et une partie régulière, qui permet de réduire le plancher d’erreur du code. Cette étude fera l’objet d’une publication dans une conférence internationale (à déterminer), à soumettre début 2012. / The advent of content distribution, IPTV, video-on-demand and other similar services accelerate the demand for reliable data transmission over highly heterogeneous networks and toward terminals potentially heterogeneous too. In this context, Forward Error Correction (FEC) codes that operate at the transport or the Application Layer (AL-FEC) are used in conjunction with the FEC codes implemented at the physical layer, in order to improve the overall performance of the communication system. AL-FEC codes are aimed at recovering erased data packets and they are essential in many multicast/broadcast environments, no matter the way the information is transported, for instance using a wired or wireless link, and a terrestrial, satellite-based or hybrid infrastructure.This thesis addresses the design of Low Density Parity Check (LDPC) codes for AL-FEC applications. One the one hand, we provide an asymptotical analysis of non-binary LDPC codes over erasure channels, as well as waterfall and error-floor optimization techniques for finite-length codes. On the other hand, new concepts and coding techniques are developed in order to fully exploit the potential of non-binary LDPC codes.The first contribution of this thesis consists of the analysis and optimization of two new ensembles of LDPC codes. First, we have derived the density evolution equations for a very general ensemble of non-binary LDPC codes with rank-deficient coefficients. This allows improving the code performance, as well as designing ensembles of LDPC codes that can be punctured in an effective manner. The second approach allows the asymptotical optimization of a particular ensemble of LDPC codes, while ensuring low error-floors at finite lengths.The second contribution is the construction of finite length LDPC codes with good waterfall and error floor performance. Two approaches were investigated, according to the metric used to evaluate the code. The “Scheduled” Progressive Edge Growth (SPEG) algorithm is proposed, in order to optimize the waterfall performance of the code. Another method is proposed which consists in optimizing a specific structure of the parity check matrix. This approach gives low error-floors.The third contribution investigates a new technique of rate adaptability for non-binary LDPC codes. We propose a new method to generate “on-the-fly” incremental redundancy, which allows designing codes with flexible coding rates, in order to cope with severe channel conditions or to enable Fountain-like distribution applications.The fourth contribution focuses on a new class of LDPC codes, called non-binary cluster-LDPC codes. We derive exact equations of the density evolution for the iterative decoding and an upper bound for the maximum-likelihood decoding.Finally, we propose a practical solution to the problem of reliable communication via satellite to high-speed trains. Here, the challenge is that obstacles present along the track regularly interrupt the communication. Our solution offers optimal performance with a minimum amount of redundancy.

Low-density parity-check (LDPC) codes are linear error correcting codes which are capable of performing near channel capacity. Furthermore, they admit efficient decoding algorithms that provide near optimum performance. Their main disadvantage is that most LDPC codes have relatively complex encoders. In this thesis, we begin by giving a detailed discussion of the sum-product decoding algorithm, we then study the performance of LDPC codes on the binary erasure channel under sum-product decoding to obtain criteria for the design of codes that allow reliable transmission at rates arbitrarily close to channel capacity. Using these criteria we show how such codes are designed. We then present experimental results and compare them with theoretical predictions. Finally, we provide an overview of several approaches to solving the complex encoder problem.

Today the society is more digitalized than yesterday. Like the rest of the world, the hotel industry is also being more digitalized. In the hotel industry hotels are working a lot with how they can interact the guest to be more active in the value creating processes and have started to adopt self-service technology. Studies today are mostly focused on how to implement more technology but not really about the user experience, especially when it comes to the service holders. The aim of this study is therefore to contribute knowledge about the service holders’ perspective on self-service technologies. The study wants to understand what service holders believe self-service technologies provide and prevent when the hotel industry gets digitalized. A literature study as well as interviews and observation has been made with the purpose to gain new information to be able to carry out a result about the service holders’ experience about the self-service technology. The qualitative material has been analysed and linked with the literature study. The study gave the result that service holders believe the self- service technology to be more effective. Where the self-service station is placed seems to be crucial for its use. Service holders believe personal service to be very important. But in the end they believe it’s the staff that will suffer from the digitalization.

Appalachia can be both exquisitely breathtaking and socially tragic, it’s a place to which many Americans trace their ancestry, and yet also it often seems forgotten. In the 1960s, the region was a major target area of the US government’s War on Poverty. Once highly noted for its tremendous post-industrial era contributions to the world’s timber and coal industries, subsequent changing economic demands and industry closures in the region have left many still living in a state of unforgiving poverty. The prevalence of counties living at or below the poverty rate, as estimated by the Appalachian Regional Commission (2015), has dropped from 295 counties in the 1960s to 90 in a 2009-2013 report. Despite this drop the region still greatly suffers due to high concentrated poverty, inadequate health care access, and unemployment. Poverty still demands attention, and scholars must understand its persistence. Many note the consistent lack of access to resources, both economic and social, as primary factors (Saegert, Thompson and Warren 2001; Blakeney 2006). Therefore, I draw on social capital and its underlying relational, social engagements as my main theoretical frame. I explore some of the sociological dynamics underlying Appalachia’s persistent poverty. Through an artifact-based ethnography in a rural eastern Kentucky community, this thesis argues that the current understandings of social capital – as a mechanism to gain social or economic resources – is greatly influenced by the presence of stigma and this is most notably manifested through the readings of cultural artifacts. This thesis’ empirical data draws on ethnographic fieldwork that also included participant observation and 45 semi-structured interviews. I tried to understand the operation of social capital through the lenses of three key artifacts that seemed to me to capture elements of poverty dynamics in the region: home, ‘welfare check’, and glucose meter. These artifacts were chosen because they allowed me to understand how mobility, access, acquisition, utilization, boundaries, and the role in which stigma affects all of these areas is presented. The fieldwork and interview data was understood and supplemented by examining official statistics, government documents, and literature focusing on the emergence and maintenance of the artifacts. The thesis articulates the complicated notions surrounding social capital and how it is manifested through the usage and reading of these objects. Furthermore, this project illustrates how actors within and outside of the community affect the reading of the objects that results in the construct of physical and social boundaries. The findings for this thesis indicates the way in which individuals in communities and external agents understand resources and interact with potential resources for impoverished individuals in providing them access is negated by their reading of objects surrounding them and is affected by the stigma attached to such objects. Chapter 4 on the home examines the concept of rootedness and social mobility; how the strong kinship ties are both a response to and protection from the effects of poverty and stigma in the region. Chapter 5 on the ‘welfare check’ illustrates further the effect that strong bonding ties can have on impeding the development of bridging ties – most notably how fear or people’s reactions, are a response founded in stigma, potentially leads to the heavy reliance on an object which arguably perpetuates poverty. Lastly, Chapter 6 uses the glucose meter to examine the effect that stigma can have internally and externally to a community, thus resulting in inadequate access to health care. The thesis’ key theoretical contribution lies in an attempt to develop an understanding of some of the paradoxical ways in which social capital operates in an impoverished community, and more especially in a theorization of the role that stigma plays in our understanding of social capital. In order to explore this further, the thesis relies heavily upon the utilization of Robert Putnam’s understanding of social capital and loosely on Pierre Bourdieu’s understanding of inequality and its influence on social capital. Erving Goffman’s notion of stigma is used to contextualize the conceptual employment of social capital and its relationship with the artifacts. Current social capital literature uses the presence of, or lack of, bonding and bridging capital in order to illustrate the amount of social capital a community has. However, I illustrate that this is heavily influenced by the presence of stigma.

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Neste trabalho discutimos vários sistemas de dígitos verificadores utilizados no Brasil, muitos deles semelhantes a esquemas usados mundialmente, e fazemos uma análise da sua capacidade de detectar os diversos tipos de erros que são comuns na entrada de dados em sistemas computacionais. A análise nos mostra que os esquemas escolhidos constituem decisões subotimizadas e quase nunca obtêm a melhor taxa de detecção de erros possível. Os sistemas de dígitos verificadores são baseados em três teorias da álgebra: aritmética modular, teoria de grupos e quasigrupos. Para os sistemas baseados em aritmética modular, apresentamos várias melhorias que podem ser introduzidas. Desenvolvemos um novo esquema ótimo baseado em aritmética modular base 10 com três permutações para identificadores de tamanho maior do que sete. Descrevemos também o esquema Verhoeff, já antigo, mas pouquíssimo utilizado e que também é uma alternativa de melhoria para identificadores de tamanho até sete. Desenvolvemos ainda, esquemas ótimos para qualquer base modular prima que detectam todos os tipos de erros considerados. A dissertação faz uso ainda de elementos da estatística, no estudo das probabilidades de detecção de erros e de algoritmos, na obtenção de esquemas ótimos. / In this paper we present several check digit systems used in Brazil, many of them similar to schemes used worldwide, and we do an analysis of their ability to detect various types of errors that are common in data entry computer systems. This analysis shows that the schemes constitute suboptimal decisions and almost never get the best rate possible error detection. Check digit schemes are based on three algebra theory: modular arithmetic, group theory and quasigroup. For the schemes based on modular arithmetic we present several improvements that can be made. We developed a new optimal scheme based on modular arithmetic base 10 with three permutations for identifers larger than 7. We also present the Verhoeff scheme, already old but used very little and that is also a good alternative for improvement identifers for size up to 7. We have also developed,optimum schemes for any modular base prime that detect all types of errors considered. The dissertation also makes use of elements of statistics in the study of the probability of error detection and algorithms to obtain optimal schemes.

Made available in DSpace on 2014-06-12T17:39:33Z (GMT). No. of bitstreams: 2 arquivo6919_1.pdf: 4119217 bytes, checksum: 3f1efa22858eeae0d86c8392becd8174 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2007 / Códigos baseados em matrizes esparsas têm desempenhado um importante papel em teoria da codificação. Os códigos low-density parity-check (LDPC) constituem uma famosa família de códigos definidos a partir de matrizes de verificação de paridade esparsas que apresentam desempenhos excelentes no canal com ruído aditivo Gaussiano branco (RAGB). O sucesso desses códigos se deve a sua representação através de grafos, que permite a operação de um algoritmo de decodificação iterativo cuja complexidade cresce linearmente com o comprimento dos blocos. Esta dissertação apresenta um estudo sobre códigos LDPC e sua principal ferramenta de análise, a density evolution. Para isso, a representação gráfica de códigos de bloco lineares e o funcionamento do algoritmo de decodificação Soma-Produto são apresentados. Algumas técnicas de projeto de códigos LDPC são discutidas e seu desempenho no canal RAGB é avaliado por meio de simulações. Baseando-se nestas ferramentas, a density evolution para os canal RAGB é derivada em forma integral e em forma aproximada. Por fim, uma modificação no algoritmo Soma-Produto é proposta para decodificação de códigos LDPC no canal Gilbert-Elliott

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