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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only QC-LDPC codes from difference matrices and difference covering arrays(IEEE-Inst Electrical Electronics Engineers Inc, 2023) Donovan, Diane M.; Rao, Asha; Üsküplü, Elif; Department of Mathematics; Yazıcı, Emine Şule; Department of Mathematics; ; College of Sciences;We give a framework that generalizes LDPC code constructions using transversal designs or related structures such as mutually orthogonal Latin squares. Our constructions offer a broader range of code lengths and codes rates. Similar earlier constructions rely on the existence of finite fields of order a power of a prime, which significantly restricts the functionality of the resulting codes. In contrast, the LDPC codes constructed here are based on difference matrices and difference covering arrays, structures that are available for any order a, resulting in LDPC codes across a broader class of parameters, notably length a(a - 1), for all even a. Such values are not possible with earlier constructions, thus establishing the novelty of these new constructions. Specifically the codes constructed here satisfy the RC constraint and for a odd, have length a(2) and rate 1 - (4a - 3)/a(2), and for a even, length a(2) - a and rate at least 1 - (4a - 6)/(a(2 )- a). When 3 does not divide a, these LDPC codes have stopping distance at least 8. When a is odd and both 3 and 5 do not divide a, our construction delivers an infinite family of QC-LDPC codes with minimum distance at least 10. We also determine lower bounds for the stopping distance of the code. Further we include simulation results illustrating the performance of our codes. The BER and FER performance of our codes over AWGN (via simulation) is at least equivalent to codes constructed previously.Publication Metadata only Multicast transport protocol analysis: self-similar sources(Springer-Verlag Berlin, 2004) Department of Mathematics; Department of Computer Engineering; Çağlar, Mine; Özkasap, Öznur; Faculty Member; Faculty Member; Department of Mathematics; Department of Computer Engineering; College of Sciences; College of Engineering; 105131; 113507We study the traffic that scalable multicast protocols generate in terms of message delays over the network as well as traffic counts at the link level in the case of self-similar sources. In particular, we study Bimodal Multicast and Scalable Reliable Multicast protocols proposed for scalable reliable multicasting. These protocols are based on different mechanisms for recovering from message losses and providing scalability. We discuss the protocol mechanisms as the main underlying factor in our empirical results. Our results can be considered as a contribution to the general problem of integration of multicast communication to large scale.Publication Metadata only An alternating service model with self-similar input to provide guaranteed QoS in wireless internet(IEEE, 2006) Iftikhar, Mohsin; Landfeldt, Bjorn; Department of Mathematics; Çağlar, Mine; Faculty Member; Department of Mathematics; College of Sciences; 105131Over the past few years, we have witnessed a growing popularity of new wireless architectures such as 3G, WiFi and Wi-Max due to the increase in demand for wireless Internet access. The all-IP based future mobile and wireless network model is expected to be the most dominant architecture for QoS provisioning in next-generation wireless networks, mainly due to its scalability and capability of inter-working heterogeneous wireless access networks. Recently, the rapid growth of various wireless infrastructures and the interesting mixture of wireless traffic generated by large number of devices (PDAs, Laptops and cell-phones) have diverted the attention of wireless research community towards understanding the nature of traffic carried by different wireless architectures. A series of recent studies on GPRS aggregated traffic, WAP and Web traffic has proven that wireless traffic exhibits strong long-range dependency. However, much of the current understanding of wireless traffic modeling builds on classical Poisson distributed traffic, which can yield misleading results and hence poor wireless network planning. In this paper, we contribute to the accurate modeling of wireless IP traffic by considering two different types of traffic that exhibit long-range dependency and self-similarity. We consider a model of two queues based on G/M/1 queueing system and analyze it on the basis of 1-limited polling service and find exact bounds on packet delay.Publication Metadata only Topology dependent information dissemination in P2P networks for anti-entropy algorithmS(Ieee, 2008) N/A; N/A; Department of Computer Engineering; Department of Mathematics; İskender, Emre; Özkasap, Öznur; Çağlar, Mine; Master Student; Faculty Member; Faculty Member; Department of Computer Engineering; Department of Mathematics; Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; N/A; 113507; 105131Analyzing the behavior of epidemic spreading in a network is a good way of modeling several network phenomena. There are several studies analyzing the spreading of email viruses. Spreading of epidemics is also a good model for several types of information dissemination in distributed systems. In this study, we examine spreading of epidemics for anti-entropy algorithms in a peer-to-peer network with any given topology. We derive nodes' exact probability distributions of being infected in each epidemic cycle.Publication Metadata only Multiclass G/M/1 queueing system with self-similar input and non-preemptive priority(Elsevier, 2008) Iftikhar, Mohsin; Singh, Tejeshwar; Landfeldt, Bjorn; Department of Mathematics; Çağlar, Mine; Faculty Member; Department of Mathematics; College of Sciences; 105131In order to deliver innovative and cost-effective IP multimedia applications over mobile devices, there is a need to develop a unified service platform for the future mobile Internet referred as the Next Generation (NG) all-IP network. It is convincingly demonstrated by numerous recent studies that modern multimedia network traffic exhibits long-range dependence (LRD) and self-similarity. These characteristics pose many novel and challenging problems in traffic engineering and network planning. One of the major concerns is how to allocate network resources efficiently to diverse traffic classes with heterogeneous QoS constraints. However, much of the current understanding of wireless traffic modeling is based on classical Poisson distributed traffic, which can yield misleading results and hence poor network planning. Unlike most existing studies that primarily focus on the analysis of single-queue systems based on the simplest First-Come-First-Serve (FCFS) scheduling policy, in this paper we introduce the first of its kind analytical performance model for multiple-queue systems with self-similar traffic scheduled by priority queueing to support differentiated QoS classes. The proposed model is based on a G/M/1 queueing system that takes into account multiple classes of traffic that exhibit long-range dependence and self-similarity. We analyze the model on the basis of non-preemptive priority and find exact packet delay and packet loss rate of the corresponding classes. We develop a finite queue Markov chain for non-preemptive priority scheduling, extending the previous work on infinite capacity systems. We extract a numerical solution for the proposed analytical framework by formulating and solving the corresponding Markov chain. We further present a comparison of the numerical analysis with comprehensive simulation studies of the same system. We also implement a Cisco-router based test bed, which serves to validate the mathematical, numerical, and simulation results as well as to support in understanding the QoS behaviour of realistic traffic input.Publication Metadata only Traffic characterization of transport level reliable multicasting: comparison of epidemic and feedback controlled loss recovery(Elsevier, 2006) N/A; Department of Computer Engineering; Department of Mathematics; Özkasap, Öznur; Çağlar, Mine; Faculty Member; Faculty Member; Department of Computer Engineering; Department of Mathematics; College of Engineering; College of Sciences; 113507; 105131Transport level multicast protocols providing reliability and scalability properties are certainly essential building blocks for several distributed group applications. We consider the effect of reliable multicast transport mechanisms oil traffic characteristics and hence network performance. Although self-similarity property of unicast traffic, ill particular TCP. has been analyzed extensively. multicast traffic has not been incorporated from this perspective. In this Study. we focus oil traffic characterization of transport level reliable multicasting. In particular, we concentrate oil two scalable and reliable multicast protocols as case studies, namely Bimodal Multicast and Scalable Reliable Multicast (SRM). and analyze the traffic generated by them. Our study consists of a complete simulation analysis supported by theoretical work. which shows that self-similarity is protocol dependent. We demonstrate that the Markovian character of Bimodal Multicast's epidemic loss recovery distinguishes ail inherently superior protocol. It discretely feeds well-behaved traffic and copes with the existing self-similarity. Oil the other hand. the feedback controlled loss recovery mechanism of SRM triggers self-similarity. Drawing upon both theoretical and Simulation analysis, our results Substantiate that transport level can induce long-range dependence even in the absence of application/user level causes.Publication Metadata only Type-speciric analysis of morphometry of dendrite spines of mice(Institute of Electrical and Electronics Engineers (IEEE), 2007) Fong, L.; Tasky, T. N.; Hurdal, M. K.; Beg, M. F.; Martone, M. E.; Ratnanather, J. T.; Department of Mathematics; Ceyhan, Elvan; Faculty Member; Department of Mathematics; College of Sciences; N/AIn this article, we analyze the morphometric measures of dendrite spines of mice derived from electron tomography images for different spine types based on pre-assigned categories. The morphometric measures we consider include the metric distance, volume, surface area, and length of dendrite spines of mice. The question of interest is how these morphometric measures differ by condition of mice; and how the metric distance relates to volume, surface area, length, and condition of mice. The Large Deformation Diffeomorphic Metric Mapping algorithm is the tool we use to obtain the metric distances that quantize the morphometry of binary images of dendrite spines with respect to a template spine. We demonstrate that for the values not adjusted for scale metric distances and other morphometric measures are significantly different between the conditions. The morphometric measures (rather than the mice condition) explain almost all the variation in metric distances. Since size (or scale) dominates the other variables in variation, we adjust metric distances and other morphometric measures for scale. We demonstrate that the scaled metric distances and other scaled morphometric variables still differ for condition, and scaled metric distances depend most significantly on scaled morphometric measures. The methodology used is also valid for morphometric measures of other organs or tissues and metric distances other than LDDMM.Publication Metadata only Traffic behavior of scalable multicast: self-similarity and protocol dependence(Elsevier Science Bv, 2003) N/A; Department of Computer Engineering; Department of Mathematics; Özkasap, Öznur; Çağlar, Mine; Faculty Member; Faculty Member; Department of Computer Engineering; Department of Mathematics; College of Engineering; College of Sciences; 113507; 105131The development of high-speed networks and the expansion of the Internet have increased both geographical extent and participant population of applications such as videoconferencing, multimedia dissemination, electronic stock exchange, and distributed cooperative work. The key property of this type of applications is the need to distribute data among multiple participants together with application specific quality of service needs which fact makes multicast protocols an essential underlying communication structure. In this paper, we analyze traffic characteristics of two scalable multicast protocols, namely Bimodal Multicast (Pbcast) and Scalable Reliable Multicast (SRM), each having different approaches for loss recovery and providing reliability. Particularly, our simulation studies demonstrate that epidemic approach of Bimodal Multicast generates a more desirable traffic than SRM with lower overhead traffic and transport delays. SRM delays show long-range dependence and self-similarity whereas Bimodal Multicast delays are shortrange dependent. Self-similarity and long-range dependence are ubiquitous in wide area networks, which lead to adverse consequences in network performance. We elaborate on the protocol mechanisms as the underlying factor in our empirical results. The intrinsic relation of these mechanisms to traffic characteristics is explored.Publication Metadata only A chain-binomial model for pull and push-based information diffusion(IEEE, 2006) Department of Mathematics; Department of Computer Engineering; Çağlar, Mine; Özkasap, Öznur; Faculty Member; Faculty Member; Department of Mathematics; Department of Computer Engineering; College of Sciences; College of Engineering; 105131; 113507We compare pull and push-based epidemic paradigms for information diffusion in large scale networks. Key benefits of these approaches are that they are fully distributed, utilize local information only via pair-wise interactions, and provide eventual consistency, scalability and communication topology-independence, which make them suitable for peer-to-peer distributed systems. We develop a chain-Binomial epidemic probability model for these algorithms. Our main contribution is the exact computation of message delivery latency observed by each peer, which corresponds to a first passage time of the underlying Markov chain. Such an analytical tool facilitates the comparison of pull and push-based spread for different group sizes, initial number of infectious peers and fan-out values which are also accomplished in this study. Via our analytical stochastic model, we show that push-based approach is expected to facilitate faster information spread both for the whole group and as experienced by each member.Publication Metadata only Message buffering in epidemic data dissemination(IEEE, 2006) N/A; Department of Mathematics; Department of Computer Engineering; Ahi, Emrah; Çağlar, Mine; Özkasap, Öznur; Master Student; Faculty Member; Faculty Member; Department of Mathematics; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; N/A; 105131; 113507In reliable group communication, epidemic or probabilistic protocols gained popularity due to their scalability to large number of peers and robustness against network failures. Reliability properties of these protocols are ensured via probabilistic guarantees. A key issue to consider when offering reliability is the buffer space used by individual peers of the group. Our aim is to optimize the buffer space while providing reliability in epidemic data dissemination protocols. We introduce a novel randomized model and compare it with a hash-based approach for buffer management. The effect of short and Iona, term buffering of peers and the buffer size on delivery latency and reliability are considered. We compute the performance measures through simulations of large-scale application scenarios.