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  • 1.
    Ahmad, Naseer
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Security Issues in Wireless Systems2009Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    ireless Communication is one of the fields of Telecommunications which is growing with the tremendous speed. With the passage of time wireless communication devices are becoming more and more common. It is not only the technology of business but now people are using it to perform their daily tasks, be it for calling, shopping, checking their emails or transfer their money. Wireless communication devices include cellular phones, cordless phones and satellite phones, smart phones like Personal Digital Assistants (PDA), two way pagers, and lots of their devices are on their way to improve this wireless world. In order to establish two way communications, a wireless link may be using radio waves or Infrared light. The Wireless communication technologies have become increasingly popular in our everyday life. The hand held devices like Personal Digital Assistants (PDA) allow the users to access calendars, mails, addresses, phone number lists and the internet. Personal digital assistants (PDA) and smart phones can store large amounts of data and connect to a broad spectrum of networks, making them as important and sensitive computing platforms as laptop PCs when it comes to an organization’s security plan. Today’s mobile devices offer many benefits to enterprises. Mobile phones, hand held computers and other wireless systems are becoming a tempting target for virus writers. Mobile devices are the new frontier for viruses, spam and other potential security threats. Most viruses, Trojans and worms have already been created that exploit vulnerabilities. With an increasing amount of information being sent through wireless channels, new threats are opening up. Viruses have been growing fast as handsets increasingly resemble small computers that connect with each other and the internet. Hackers have also discovered that many corporate wireless local area networks (WLAN) in major cities were not properly secured. Mobile phone operators say that it is only a matter of time before the wireless world is hit by the same sorts of viruses and worms that attack computer software.

  • 2.
    Chunduri, Krishna Chaitanya
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Gutti, Chalapathi
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Implementation of Adaptive Filter Structures on a Fixed Point Signal Processor for Acoustical Noise Reduction2005Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    The problem of controlling the noise level in the environment has been the focus of a tremendous amount of research over the years. Active Noise Cancellation (ANC) is one such approach that has been proposed for reduction of steady state noise. ANC refers to an electromechanical or electro acoustic technique of canceling an acoustic disturbance to yield a quieter environment. The basic principle of ANC is to introduce a canceling “anti-noise” signal that has the same amplitude but the exact opposite phase, thus resulting in an attenuated residual noise signal. Wideband ANC systems often involve adaptive filter lengths, with hundreds of taps. Using sub band processing can considerably reduce the length of the adaptive filter. This thesis presents Filtered-X Least Mean Squares (FXLMS) algorithm to implement it on a fixed point digital signal processor (DSP), ADUC7026 micro controller from Analog devices. Results show that the implementation in fixed point matches the performance of a floating point implementation.

  • 3.
    Hoque, MD. Anamul
    Blekinge Institute of Technology, School of Computing.
    VOIP mobility over heterogeneous networks with focus on mobility issue2010Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Abstract Multimedia on wireless networks and the integration with other cellular networks requires support for both mobility and quality of service. When mobile nodes move across different wireless networks, current session may be affected by the several factors like hand off delay, jitter and data loss. Voice over IP (VOIP) will be operated seamlessly across different wireless networks and that resulted few issues like mobility, signals and security. Mobile IP is proposed as a network layer host mobility solution. The problem associated with mobile IP makes it unsuitable for real time interactive solution like Voice over IP (VOIP). In this thesis paper we study the VOIP mobility in homogeneous wireless networks and cross layer mechanism for heterogeneous wireless networks which can support mobility in layer 2 of the network stack to get better VOIP performances and mobility. We describe the cross layer mechanism and the experimental results.

  • 4.
    Ijaz, Muhammad
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    TRASMISSION CONTROL PROTOCOL (TCP) PERFORMANCE EVALUATION IN MANET2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Mobile Ad hoc network routing protocols have been divided in several different categories such as Reactive and Proactive Routing Protocol. The performances of these categories are evaluated in different scenario with TCP variants. We present a comprehensive TCP performance evaluation study to understand the nature of the TCP performance in different scenarios with variable amount of payload and number of nodes. The traffic consists of three different packet sizes i.e. 512, 1000, 1500 bytes each. Three different routing protocols (AODV, DSR and TORA) are to be evaluated with three different TCP variants (Tahoe, Reno and New Reno) in three different scenarios having 3, 5 and 8 nodes. The performances parameters on the basis of which routing protocols are to be graded are mainly throughput, congestion window and delay. Conclusions are drawn based on the simulation results and the comparisons between them have been elaborated.

  • 5.
    Khan, Khalid
    Blekinge Institute of Technology, School of Computing.
    The Evaluation of Well-known Effort Estimation Models based on Predictive Accuracy Indicators2010Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Accurate and reliable effort estimation is still one of the most challenging processes in software engineering. There have been numbers of attempts to develop cost estimation models. However, the evaluation of model accuracy and reliability of those models have gained interest in the last decade. A model can be finely tuned according to specific data, but the issue remains there is the selection of the most appropriate model. A model predictive accuracy is determined by the difference of the various accuracy measures. The one with minimum relative error is considered to be the best fit. The model predictive accuracy is needed to be statistically significant in order to be the best fit. This practice evolved into model evaluation. Models predictive accuracy indicators need to be statistically tested before taking a decision to use a model for estimation. The aim of this thesis is to statistically evaluate well known effort estimation models according to their predictive accuracy indicators using two new approaches; bootstrap confidence intervals and permutation tests. In this thesis, the significance of the difference between various accuracy indicators were empirically tested on the projects obtained from the International Software Benchmarking Standard Group (ISBSG) data set. We selected projects of Un-Adjusted Function Points (UFP) of quality A. Then, the techniques; Analysis Of Variance ANOVA and regression to form Least Square (LS) set and Estimation by Analogy (EbA) set were used. Step wise ANOVA was used to form parametric model. K-NN algorithm was employed in order to obtain analogue projects for effort estimation use in EbA. It was found that the estimation reliability increased with the pre-processing of the data statistically, moreover the significance of the accuracy indicators were not only tested statistically but also with the help of more complex inferential statistical methods. The decision of selecting non-parametric methodology (EbA) for generating project estimates in not by chance but statistically proved.

  • 6.
    Khan, Mubbashar Altaf
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Ahmad, Sohaib
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Decision Making Techniques for Cognitive Radios2008Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    Spectrum scarcity is one of the biggest challenges that the modern world is facing. The efficient use of available licensed spectrum is becoming more and more critical with increasing demand and usage of the radio spectrum. Different researches show that the usage is not uniform throughout the licensed spectrum rather it is heavy in certain parts of the spectrum and has portions that are utilized inefficiently. Some researchers even claim that more than 70% of the licensed frequency band is not in use, most of the time. So, there is much room for work yet in the unutilized parts or the inefficiently utilized parts of the spectrum, to overcome the spectrum scarcity problem. Different researches are in progress and ways are being found to efficiently utilize the available licensed spectrum. One of the ways is the use of “Cognitive Radio”, according to this; the already licensed spectrum can be used more efficiently by introducing artificial intelligence, the decision-making to be specific, in the radio. This enables the radio to learn from its environment, considering certain parameters. Based on this knowledge the radio can actively exploit the possible empty frequencies in the licensed band of the spectrum that can then be assigned to other processes in such a way that they don’t cause any interference to the frequency band that is already in use. This makes the efficient usage of the available licensed spectrum possible. The users that are allocated the licensed frequency bands of the spectrum are the primary users and the users that are allocated the empty frequencies within the licensed frequency band, according to their requested QoS specifications, are known as the secondary users or the cognitive users. They are called as the secondary users as they utilize the unused spectrum resources only, on non-interfering basis, with the primary users. This thesis will focus on the implementation of different spectrum allocation techniques for these secondary users, based on Genetic Algorithms and an evaluation of the performance of these techniques using Matlab coding. This research will focus on the decision-making process mainly, with an assumption that the radio environment has already been sensed and the QoS requirements for the application have been specified either by the sensed radio environment or by the secondary user itself.

  • 7.
    Mama, Mounchili
    Blekinge Institute of Technology, School of Engineering, Department of Mathematics and Natural Sciences.
    Mathematical Modelling of The Global Positioning System Tracking Signals2008Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    Recently, there has been increasing interest within the potential user community of Global Positioning System (GPS) for high precision navigation problems such as aircraft non precision approach, river and harbor navigation, real-time or kinematic surveying. In view of more and more GPS applications, the reliability of GPS is at this issue. The Global Positioning System (GPS) is a space-based radio navigation system that provides consistent positioning, navigation, and timing services to civilian users on a continuous worldwide basis. The GPS system receiver provides exact location and time information for an unlimited number of users in all weather, day and night, anywhere in the world. The work in this thesis will mainly focuss on how to model a Mathematical expression for tracking GPS Signal using Phase Locked Loop filter receiver. Mathematical formulation of the filter are of two types: the first order and the second order loops are tested successively in order to find out a compromised on which one best provide a zero steady state error that will likely minimize noise bandwidth to tracks frequency modulated signal and returns the phase comparator characteristic to the null point. Then the Z-transform is used to build a phase-locked loop in software for digitized data. Finally, a Numerical Methods approach is developed using either MATLAB or Mathematica containing the package for Gaussian elimination to provide the exact location or the tracking of a GPS in the space for a given a coarse/acquisition (C/A) code.

  • 8.
    SEKHAR, MADHU KIRAN . EDURU RAJA CHANDRA
    et al.
    Blekinge Institute of Technology, School of Engineering.
    THOTA, PARTHA SARADHI .
    Blekinge Institute of Technology, School of Engineering.
    CONTROL OF BUCK CONVERTER BY POLYNOMIAL, PID AND PD CONTROLLERS.2012Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    This thesis is an ongoing project of Ericsson with collaboration of Blekinge Institute of Technology [BTH], and Linneaus University [LNU] to compare the functionality and performance of three controllers Polynomial Pole Placement, PID [Proportional Integral Derivative] and PD controller in third order. This paper presents the state space modeling approach of DC-DC Buck converter. The main aim of this thesis is, by considering the buck converter system of Ericsson BMR450 with the PID, POLYNOMIAL and PD controllers at feedback loop, thus running their Matlab file with their appropiate Simulink block diagram, and comparing the three controllers performance by verifying their appropiate output graphs. The third order controller design is complicated and response is slow. The second order design is easy and gives better responses than third order Polynomial, PID and PD controllers.

  • 9.
    Taghavianfar, Mohsen
    Blekinge Institute of Technology, School of Engineering.
    An Investigation on Network Entropy-Gossiping Protocol and Anti-entropy Evaluation2013Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    This thesis is concerned with studying the behavior of a gossiping protocol in the specific sense meant by Ericsson; in the following pages I’ll introduce a Markov process which models the spread of information in such systems. The results will be verified by means of a discreet-event simulation.

  • 10.
    THUPALLI, NAVEEN KUMAR
    Blekinge Institute of Technology, School of Engineering.
    MICROPHONE ARRAY SYSTEM FOR SPEECH ENHANCEMENT IN LAPTOPS2012Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Recognition of speech at the receiver end generally gets degraded in distant talking atmospheres of laptops, teleconfereing, video conferences and in hands free telephony, where the quality of speech gets contaminated and severely disturbed because of the additive noises. To make useful and effective, the exact speech signals has to be extracted from the noise signals and the user has to be given the clean speech. In such conditions the convenience of microphone array has been preferred as a means of civilizing the quality of arrested signals. A consequential growth in laptop technology and microphone array processing have made possible to improve intelligibility of speech while communication. So this contention target on reducing the additive noises from the original speech, beside design and use of different algorithms. In this thesis a multi-channel microphone array with its speech enhancement of signals to Wiener Beamformar and Generalized side lobe canceller (GSC) are used for Laptops in a noisy environment. Systems prescribed above were implemented, processed and evaluated on a computer using Mat lab considering SNR, SNRI as the main objective of quality measures. Systems were tested with two speech signals, among which one is Main speech signal and other is considered as Noise along with another random noise, sampling them at 16 KHz .Three Different source originations were taken into consideration with different input SNR’s of 0dB, 5dB, 10dB, 15dB, 20dB, 25dB. Simulation Results showed that Noise is been attenuated to a great extent. But Variations in SNR and SNRI has been observed, because of the different point origination of signals in the respective feilds.Variation in SNR and SNRI is been observed when the distance between the main speech originating point and microphone is too long compared to the noise signals. This states that origination of signals plays a huge role in maintaining the speech quality at the receiver end.

  • 11.
    VIENJIPURAM, KRISHNA KUMARAN
    et al.
    Blekinge Institute of Technology, School of Computing.
    ABDUL, ASMEER BABU
    Blekinge Institute of Technology, School of Computing.
    Improving the Quality of Multicast Networks by Using the OPNET Modeler2010Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    This thesis presents different Internet Protocol (IP) multicasting design models and together with their implementation methods in OPNET Modeler 14.5. The models presented in this report are designed for handling various types of advanced multimedia applications and services when using the multicast communication paradigm. The architectural models presented in this thesis are independent of the routing protocols used as well as of the underlying networking environment. Several exiting challenges related to high bandwidth requirements, low network delay, and jitter are discussed together with these design models, and are simulated using the OPNET Modeler. The emerging demands for new multicast capable applications, for both real-time and non real-time traffic are considered together in this report in order to better evaluate multicast traffic requirements. Efficient routing methods, group management policies, and shortest path algorithms are also discussed in the proposed models. The pros and cons of IP multicasting are described using the Protocol Independent Multicast Sparse Mode (PIM-SM) method, in the highlight of the proposed design models. Several results related to link utilization, end-to-end delay, packet loss, PIM control traffic, Internet Group Management Protocol (IGMP), and network convergence are obtained by using already available statistical methods and modules from OPNET Modeler. Our major contribution with this thesis work relates to components associated with network convergence, routing delay, and processing delay. These components are illustrated in this thesis using various OPNET metrics. Moreover, several issues related to protocol scalability, supportability, performance optimization and efficiency are also presented by using OPNET’s build in reports, i.e., executive flow and survivability analysis reports.

  • 12.
    Yang, Shun
    Blekinge Institute of Technology, School of Engineering.
    Modelling and control of a Buck converter2011Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [en]

    DC/DC buck converters are cascaded in order to generate proper load voltages. Rectified line voltage is normally converted to 48V, which then, by a bus voltage regulating converter also called the line conditioner converter, is converted to the bus voltage, e.g. 12V. A polynomial controller converter transforms the 12V into to a suitable load voltage, a fraction of or some few voltages. All cascaded converters are individually controlled in order to keep the output voltage stable constant. In this presentation focusing on the polynomial controller converter implemented as Ericsson’s buck converter BMR450. In this paper modeling, discretization and control of a simple Buck converter is presented. For the given DC-DC-Converter-Ericsson BMR 450 series, analyzing the disturbance properties of a second order buck converter controllers by a polynomial controller. The project is performed in Matlab and Simulink. The controller properties are evaluated for measurement noise, EMC noise and for parameter changes.

  • 13.
    Zavareh, Alireza
    Blekinge Institute of Technology, School of Engineering.
    Analytical and Numerical methods for a Mean curvature flow equation with applications to financial Mathematics and image processing2012Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    This thesis provides an analytical and two numerical methods for solving a parabolic equation of two-dimensional mean curvature flow with some applications. In analytical method, this equation is solved by Lie group analysis method, and in numerical method, two algorithms are implemented in MATLAB for solving this equation. A geometric algorithm and a step-wise algorithm; both are based on a deterministic game theoretic representation for parabolic partial differential equations, originally proposed in the genial work of Kohn-Serfaty [1].

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