A cluster-head selection and update algorithm for ad hoc networks

A novel cluster-head selection and update algorithm “Type-based Cluster-forming Algorithm (TCA)” is proposed, which outperforms both the lowest node ID (LID) and the Weighted Clustering Algorithm (WCA) in the ad hoc network scenario considered. The system’s performance is investigated in a scenario, when the 50 communicating nodes belong to three different groups, for example, a group of rescue workers, fire-fighters and paramedics. It is demonstrated that the carefully designed protocol is capable of outperforming the above-mentioned benchmarkers both in terms of a reduced number of cluster-head updates and cluster-change events. Hence its quality-of-service may be deemed higher

A Survey of Checkpointing Algorithms in Mobile Ad Hoc Network

Checkpoint is defined as a fault tolerant technique that is a designated place in a program at which normal processing is interrupted specifically to preserve the status information necessary to allow resumption of processing at a later time. If there is a failure, computation may be restarted from the current checkpoint instead of repeating the computation from beginning. Checkpoint based rollback recovery is one of the widely used technique used in various areas like scientific computing, database, telecommunication and critical applications in distributed and mobile ad hoc network. The mobile ad hoc network architecture is one consisting of a set of self configure mobile hosts capable of communicating with each other without the assistance of base stations. The main problems of this environment are insufficient power and limited storage capacity, so the checkpointing is major challenge in mobile ad hoc network. This paper presents the review of the algorithms, which have been reported for checkpointing approaches in mobile ad hoc network

Trust Based Node Recovery and Checkpointing Techniques in Manets

Checkpointing is a process of determining the vulnerability of node in case of any attack occurs in the network. It depends on the cluster change count value of the node. If the measure of the hop exchanges required to reach the destination node from the current node, is above the previously specified value, the node under consideration is unsafe and safe points must be implemented in between the path and different subnetworks within that network must have their own implemented safe points. The message must commits to the safe points as it reaches the respective sub networks. The message in the networks evolve over the certain subnetworks. The each subnetwork has the checkpoint node, that serves the purpose for communication between different subnetworks, or between the hops in different subnetworks. This phenomenon supports the system efficiency and preserves the robustness. The process retrieval methods, therefore, should be implemented with the use of the safe points to prevent system degradation. In this research paper, an efficient recovery protocol is designed for distributed transactions in MANETs so that failures can be minimised. Dynamic analysis has also been done and it is compared with other existing protocols to validate the attained result

Security in Distributed, Grid, Mobile, and Pervasive Computing

This book addresses the increasing demand to guarantee privacy, integrity, and availability of resources in networks and distributed systems. It first reviews security issues and challenges in content distribution networks, describes key agreement protocols based on the Diffie-Hellman key exchange and key management protocols for complex distributed systems like the Internet, and discusses securing design patterns for distributed systems. The next section focuses on security in mobile computing and wireless networks. After a section on grid computing security, the book presents an overview of security solutions for pervasive healthcare systems and surveys wireless sensor network security

Investigating Polynomial Fitting Schemes for Image Compression

Image compression is a means to perform transmission or storage of visual data in the most economical way. Though many algorithms have been reported, research is still needed to cope with the continuous demand for more efficient transmission or storage. This research work explores and implements polynomial fitting techniques as means to perform block-based lossy image compression. In an attempt to investigate nonpolynomial models, a region-based scheme is implemented to fit the whole image using bell-shaped functions. The idea is simply to view an image as a 3D geographical map consisting of hills and valleys. However, the scheme suffers from high computational demands and inferiority to many available image compression schemes. Hence, only polynomial models get further considerations. A first order polynomial (plane) model is designed to work in a multiplication- and division-free (MDF) environment. The intensity values of each image block are fitted to a plane and the parameters are then quantized and coded. Blocking artefacts, a common drawback of block-based image compression techniques, are reduced using an MDF line-fitting scheme at blocks’ boundaries. It is shown that a compression ratio of 62:1 at 28.8dB is attainable for the standard image PEPPER, outperforming JPEG, both objectively and subjectively for this part of the rate-distortion characteristics. Inter-block prediction can substantially improve the compression performance of the plane model to reach a compression ratio of 112:1 at 27.9dB. This improvement, however, slightly increases computational complexity and reduces pipelining capability. Although JPEG2000 is not a block-based scheme, it is encouraging that the proposed prediction scheme performs better in comparison to JPEG 2000, computationally and qualitatively. However, more experiments are needed to have a more concrete comparison. To reduce blocking artefacts, a new postprocessing scheme, based on Weber’s law, is employed. It is reported that images postprocessed using this scheme are subjectively more pleasing with a marginal increase in PSNR (<0.3 dB). The Weber’s law is modified to perform edge detection and quality assessment tasks. These results motivate the exploration of higher order polynomials, using three parameters to maintain comparable compression performance. To investigate the impact of higher order polynomials, through an approximate asymptotic behaviour, a novel linear mapping scheme is designed. Though computationally demanding, the performances of higher order polynomial approximation schemes are comparable to that of the plane model. This clearly demonstrates the powerful approximation capability of the plane model. As such, the proposed linear mapping scheme constitutes a new approach in image modeling, and hence worth future consideration

Business model innovation in small and medium-sized enterprises: an exploration of key drivers and performance implications

Small and medium-sized enterprises (SMEs) are at the heart of a nation's wealth creation, employment generation and economic development. Hence, new ways to sustain and reinforce their competitiveness in today’s fast-changing, complex and unpredictable environment become key for their survival and the development of the region. In this context, business model innovation is emerging as a new source of competitive advantage that can complement or even substitute for traditional forms of innovation. Recently, research has started to empirically explore how SMEs can proactively address business model innovation to adapt their business model to the environmental challenges. However, the literature is widely dispersed, and further research is needed to develop the big picture of the key drivers and outcomes of business model innovation in SMEs. The main goal of this thesis is therefore to explore business model innovation in SMEs from a holistic view. Based on a sample of 78 SMEs and using an exploratory approach, it examines the effects of certain antecedents on business model innovation, and the performance implications of business model innovation. Business model innovation is also compared with other forms of innovation (product, service, marketing, process and organisation). Research is conducted through a mixed-method approach comprising a questionnaire and different methods of data analysis: partial least squares structural equation modeling, fuzzy-sets qualitative comparative analysis, and statistical tests. The findings suggest that strategizing, sensing and experimenting capabilities are key drivers of business model innovation in SMEs, and these capabilities are promoted by the managerial orientation and the innovation culture of the firm. The influence of collaboration capabilities on business model innovation, in turn, was found non-significant. The results also indicate that the use of business model innovation tools facilitates business model innovation. Approaching the phenomenon from a configurational view, the results further suggest that SMEs combine the above-mentioned antecedents following different, equally effective paths to business model innovation, thereby reflecting distinct causation-effectuation behaviours. Additionally, business model innovation seem to be related to superior firm performance, and business model advantage partially explains this relationship. Lastly, it is shown that business model innovation is a distinct but complementary form of innovation that interrelates with business innovation (product, service, marketing, process and organisation). This investigation contributes therefore to a better understanding of business model innovation in SMEs, and the results have practical implications for SMEs and public administration.Enpresa txiki eta ertainak (ETEak) aberastasun eta enpleguaren sorrerarako eta garapen ekonomikorako giltzarria dira. Horrela, egungo ingurune aldakor, konplexu eta ezustekoan ETE-en lehiakortasuna mantendu eta indartzeko modu berriak nahiatezkoak dira haien biziraupenerako eta lurraldearen garapenerako. Testuinguru horretan, negozio ereduaren berrikuntza lehiarako abantail iturri berria bilakatu da, eta berritzeko modu tradizionalak osatu edota ordezkatu ditzake. Azken urteetan ikerketak hasi dira enpirikoki aztertzen nola berritu ditzaketen modu proaktiboan ETE-ek euren negozio ereduak testuinguruko erronketara egokitzeko. Hala ere, literatura oso zabala da eta ikerketa gehiago behar dira ETE-etan negozio ereduaren berrikuntza sustatzen duten faktore nagusien eta emaitzen ikuspegia orokorra lortzeko. Hori dela eta, ETE-en negozio ereduaren berrikuntza ikuspegi holistikotik aztertzea da tesiaren helburu nagusia. 78 ETEko lagin batetik abiatuta, ikerketak explorazio ikuspegia hartu, eta aurrerakari batzuek negozio ereduaren berrikuntzan duten eragina eta negozio ereduaren berrikuntzak enpresaren emaitzetan duen ondorioa aztertzen ditu. Negozio ereduaren berrikuntza beste berrikuntza mota batzuekin (produktua, zerbitzua, marketina, prozesua eta antolakuntza) ere alderatzen da. Ikerketak, metodo misto baten antzera, datuak galdetegi baten bitartez jaso, eta hiru metodo hauen bitartez ustiatu ziren: partial least squares ekuazio estrukturalen bidezko modelizazioa, fuzzy-set analisi kualitatibo konparatiboa, eta test estatistikoak. Emaitzek aditzera ematen dutenez, estrategia garatzeko, aukerak hautemateko eta esperimentatzeko gaitasunak dira ETE-en negozio ereduaren berrikuntzaren eragile nagusiak, eta kudeaketa orientazioa eta enpresaren berrikuntza kulturak dira, berriz, gaitasun horiek sustatzen dituztenak. Lankidetza gaitasunaren eragina negozio ereduen berrikuntzan, berriz, ez zen esanguratsua. Emaitzek adierazten dute, halaber, negozio ereduaren berrikuntzarako tresnen erabilerak negozio ereduaren berrikuntza errazten duela. Horrez gain, aurrekari horiek enpresaren portaeraren arabera (causal-effectual) bide desberdinetatik negozio eredua berritzera daramaten hainbat konfigurazio eraginkor iradokitzen dira. Gainera, badirudi negozio ereduaren berrikuntza enpresaren errendimenduaren hobekuntzarekin lotuta dagoela, eta negozio ereduaren abantailak, berriz, partzialki azaltzen du erlazio hori. Azkenik, egiaztatu zen negozio ereduarena berrikuntza mota ezberdina dela, baina beste berrikuntza mota batzuen osagarria. Hori guztia dela eta, ikerketa honek ETE-etan negozio ereduen berrikuntza hobeto ulertzen laguntzen du, eta aldi berean ETE-ei eta administrazio publikoei inplikazio praktikoak eskaintzen dizkie.La pequeña y mediana empresa (PYME) es clave para la creación de riqueza, generación de empleo y el desarrollo económico. Así, las nuevas formas de mantener y reforzar su competitividad en un entorno cada vez más cambiante, complejo e impredecible, son clave para su supervivencia y el desarrollo de la región. En este contexto, la innovación en el modelo de negocio emerge como una nueva fuente de ventaja competitiva que puede complementar o incluso sustituir las formas tradicionales de innovación. Recientemente, las investigaciones han comenzado a explorar empíricamente la forma en que las PYMEs pueden innovar proactivamente su modelo de negocio para adaptarlo a los desafíos del entorno. Sin embargo, la literatura es muy dispersa y es necesario seguir investigando para obtener una idea general de los principales impulsores y los resultados de la innovación en el modelo de negocio de las PYMEs. Por lo tanto, el principal objetivo de esta tesis es explorar la innovación en el modelo de negocio en las PYMEs desde una visión holística. En base a una muestra de 78 PYMEs, esta investigación adopta un enfoque exploratorio que aborda el efecto que ciertos antecedentes tienen en la innovación en el modelo de negocio, y el impacto que ésta tiene sobre los resultados organizacionales. También se compara la innovación en el modelo de negocio con otros tipos de innovación (producto, servicio, proceso, marketing, organización). La investigación se aborda mediante un enfoque de métodos mixtos que comprende un cuestionario y diferentes métodos de análisis de datos: modelización de ecuaciones estructurales por el método de mínimos cuadrados parciales, análisis cualitativo comparativo de conjuntos difusos y pruebas estadísticas. Los resultados sugieren que las capacidades de elaboración de estrategias, detección de oportunidades y experimentación son las principales impulsoras de la innovación en el modelo de negocio de las PYMEs, y que estas capacidades son promovidas por la orientación de la gestión y la cultura de innovación de la empresa. A su vez, la influencia de las capacidades de colaboración en la innovación en el modelo de negocio resultó no ser significativa. Los resultados también indican que el uso de herramientas para la innovación en el modelo de negocio facilita la innovación en el modelo de negocio. Al abordar el fenómeno desde una perspectiva configuracional, los resultados sugieren que las PYMEs combinan estos antecedentes siguiendo caminos diferentes, pero igualmente eficaces para innovar en el modelo de negocio; lo que refleja distintos comportamientos (causales y efectuales). Además, la innovación en el modelo de negocio parece estar relacionada con un rendimiento superior de la empresa, y la ventaja del modelo de negocio explica parcialmente esta relación. Por último, se muestra que la innovación en el modelo de negocio es una forma de innovación distinta, pero complementaria, que se interrelaciona con otros tipos de innovación. Esta investigación contribuye así a una mejor comprensión de la innovación en el modelo de negocio, al tiempo que proporciona implicaciones prácticas para las PYMEs y la administración pública

Configurational explanation of marketing outcomes : a fuzzy-set qualitative comparative analysis approach

As marketing, as a function and a process, is required to explain itself with more transparency, new tools and comprehensive analysis processes must be created and adopted, so that marketing performance and its determinants can systematically be understood and developed. In this dissertation, I present fuzzy-set qualitative comparative analysis (‘FS/QCA’; Ragin, 2000; Fiss, 2008; Rihoux and Ragin, 2009; and others) as a novel approach to assessing marketing performance. My key argument is that the fuzzy-set qualitative comparative analysis research approach and methodology can be used to explain marketing outcomes as results of configurations of causal conditions in specific contexts, yielding managerially relevant knowledge that would otherwise be difficult to access and interpret. The broad aim of this dissertation is to supplement the range of marketing management support systems, modeling approaches, and marketing performance assessment systems to provide better knowledge-driven decision support. The analytical premises of FS/QCA and its applications in fields of study related to marketing position it as a candidate to overcome some key challenges faced in marketing performance analysis: dealing with causal complexity, heterogeneity, asymmetry, configurationality, contextuality, and qualitative meaning. To draw together the research approach, the methodology, and the marketing performance management perspective, I specify a synthetic research process, configurational explanation of marketing outcomes (‘CEMO’), comprising the theoretical and empirical steps required for analysis. I demonstrate how the configurational explanation process was successfully carried out in two empirical contexts to generate results that are valid, reliable, and contribute knowledge that is directly relevant within the chosen context. The key contribution of this study is intended to be methodological: a specification of an analysis process for accessing a new type of contextually relevant knowledge about causal mechanisms that shape marketing performance. New knowledge accessible with CEMO provides opportunities for staging more effective marketing actions and, ultimately, an opportunity for better marketing performance