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  • 1.
    Abari, Farzad Foroughi
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Optimization of Audio Processing algorithms (Reverb) on ARMv6 family of processors2008Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Audio processing algorithms are increasingly used in cell phones and today’s customers are placing more demands on cell phones. Feature phones, once the advent of mobile phone technology, nowadays do more than just providing the user with MP3 play back or advanced audio effects. These features have become an integral part of medium as well as low-end phones. On the other hand, there is also an endeavor to include as improved quality as possible into products to compete in market and satisfy users’ needs. Tackling the above requirements has been partly satisfied by the advance in hardware design and manufacturing technology. However, as new hardware emerges into market the need for competence to write efficient software and exploit the new features thoroughly and effectively arises. Even though compilers are also keeping up with the new tide space for hand optimized code still exist. Wrapped in the above goal, an effort was made in this thesis to partly cover the competence requirement at Multimedia Section (part of Ericsson Mobile Platforms) to develope optimized code for new processors. Forging persistently ahead with new products, EMP has always incorporated the latest technology into its products among which ARMv6 family of processors has the main central processing role in a number of upcoming products. To fully exploit latest features provided by ARMv6, it was required to probe its new instruction set among which new media processing instructions are of outmost importance. In order to execute DSP-intensive algorithms (e.g. Audio Processing algorithms) efficiently, the implementation should be done in low-level code applying available instruction set. Meanwhile, ARMv6 comes with a number of new features in comparison with its predecessors. SIMD (Single Instruction Multiple Data) and VFP (Vector Floating Point) are the most prominent media processing improvements in ARMv6. Aligned with thesis goals and guidelines, Reverb algorithm which is among one of the most complicated audio features on a hand-held devices was probed. Consequently, its kernel parts were identified and implementation was done both in fixed-point and floating-point using the available resources on hardware. Besides execution time and amount of code memory for each part were measured and provided in tables and charts for comparison purposes. Conclusions were finally drawn based on developed code’s efficiency over ARM compiler’s as well as existing code already developed and tailored to ARMv5 processors. The main criteria for optimization was the execution time. Moreover, quantization effect due to limited precision fixed-point arithmetic was formulated and its effect on quality was elaborated. The outcomes, clearly indicate that hand optimization of kernel parts are superior to Compiler optimized alternative both from the point of code memory as well as execution time. The results also confirmed the presumption that hand optimized code using new instruction set can improve efficiency by an average 25%-50% depending on the algorithm structure and its interaction with other parts of audio effect. Despite its many draw backs, fixed-point implementation remains yet to be the dominant implementation for majority of DSP algorithms on low-power devices.

  • 2.
    Abdelsamad, Deena
    Blekinge Institute of Technology, School of Engineering.
    Video Transmission Jerkiness Measure2013Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [en]

    Digital video transmission is widely used nowadays in multimedia. Frame dropping, freeze and reduced number of frames in the transmitted video are common symptoms of bad transmission quality. In order to assess the quality of transmission, a criterion is introduced in a model for a no reference video jerkiness measure [3]. This model is dierent from the former models presented as it depends on viewing conditions and video resolutions, so it is applicable for any frame size from QCIF to HD. The model uses simple mathematical equations of jerkiness and can be used for any video sequence [3]. A model of reduced reference method (Qtransmission) which depends on a pre-measured Jerkiness is introduced as a suggestion of future work.

  • 3.
    Abelsson, Sara
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Propagation Measurements at 3.5 GHz for WiMAX2007Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    Propagation measurements at the frequency 3.5 GHz for the WiMAX technology have been conducted. The purpose of these measurements is that a coverage analysis should be accomplished. The mathematical software package MATLAB has been used to analyze the collected data from the measurement campaign. Path loss models have also been used and a comparison between these models and the collected data has been performed. An analysis prediction tool from an application called WRAP has also been used in the comparison with the collected data. In this thesis, diff

  • 4.
    Abghari, Shahrooz
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    García Martín, Eva
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Johansson, Christian
    NODA Intelligent Systems AB, SWE.
    Lavesson, Niklas
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Grahn, Håkan
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Trend analysis to automatically identify heat program changes2017In: Energy Procedia, Elsevier, 2017, Vol. 116, 407-415 p.Conference paper (Refereed)
    Abstract [en]

    The aim of this study is to improve the monitoring and controlling of heating systems located at customer buildings through the use of a decision support system. To achieve this, the proposed system applies a two-step classifier to detect manual changes of the temperature of the heating system. We apply data from the Swedish company NODA, active in energy optimization and services for energy efficiency, to train and test the suggested system. The decision support system is evaluated through an experiment and the results are validated by experts at NODA. The results show that the decision support system can detect changes within three days after their occurrence and only by considering daily average measurements.

  • 5.
    Abualhana, Munther
    et al.
    Blekinge Institute of Technology, School of Computing.
    Tariq, Ubaid
    Blekinge Institute of Technology, School of Computing.
    Improving QoE over IPTV using FEC and Retransmission2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    IPTV (Internet Protocol Television), a new and modern concept of emerging technologies with focus on providing cutting edge high-resolution television, broadcast, and other fascinating services, is now easily available with only requirement of high-speed internet. Everytime a new technology is made local, it faces tremendous problems whether from technological point of view to enhance the performance or when it comes down to satisfy the customers. This cutting edge technology has provided researchers to embark and play with different tools to provide better quality while focusing on existing tools. Our target in dissertation is to provide a few interesting facets of IPTV and come up with a concept of introducing an imaginary cache that can re-collect the packets travelling from streaming server to the end user. In the access node this cache would be fixed and then on the basis of certain pre-assumed research work we can conclude how quick retransmission can take place when the end user responds back using RTCP protocol and asks for the retransmission of corrupted/lost packets. In the last section, we plot our scenario of streaming server on one side and client, end user on the other end and make assumption on the basis of throughput, response time and traffic.

  • 6.
    Adamov, Alexander
    et al.
    Harkivskij Nacionalnij Universitet Radioelectroniki, UKR.
    Carlsson, Anders
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Cloud incident response model2016In: Proceedings of 2016 IEEE East-West Design and Test Symposium, EWDTS 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016Conference paper (Refereed)
    Abstract [en]

    This paper addresses the problem of incident response in clouds. A conventional incident response model is formulated to be used as a basement for the cloud incident response model. Minimization of incident handling time is considered as a key criterion of the proposed cloud incident response model that can be done at the expense of embedding infrastructure redundancy into the cloud infrastructure represented by Network and Security Controllers and introducing Security Domain for threat analysis and cloud forensics. These architectural changes are discussed and applied within the cloud incident response model. © 2016 IEEE.

  • 7.
    Adapa, Nagaswaroopa
    et al.
    Blekinge Institute of Technology, School of Engineering.
    Bollu, Sravya
    Blekinge Institute of Technology, School of Engineering.
    Performance analysis of different adapative algorithms based on acoustic echo cancellation2013Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    In modern telecommunication systems like hands-free and teleconferencing systems, the problem arise during conversation is the creation of an acoustic echo. This problem degrades the quality of the information signal. All speech processing equipments like noise cancelling headphones and hearing aids should be able to filter different kinds of interfering signals and produce a clear sound to the listener. Currently, echo cancellation is a most interesting and challenging task in any communication system. Echo is the delayed and degraded version of original signal which travels back to its source after several reflections. Eliminating this effect without affecting the original quality of the speech is a challenge of research in present days. Echo cancellation in voice communication is a process of removing the echo to improve the clarity and quality of the voice signals. In our thesis we mainly focused on the acoustic echo cancellation in a closed room using adaptive filters. The Acoustic echo cancellation with adaptive filtering technique will more accurately enhance the speech quality in hands free communication systems. The main aim of using adaptive algorithms for echo cancellation is to achieve higher ERLE at higher rate of convergence with low complexity. The adaptive algorithms NLMS, APA and RLS are implemented using MATLAB. These algorithms are tested with the simulation of echo occurring environment by using constant room dimensions , microphone and source positions. The performance of the NLMS, APA and RLS are evaluated in terms ERLE and misalignment. The results show that RLS algorithm achieve good performance with more computational complexity comparing with the NLMS and APA algorithms. The NLMS algorithm has very low computational complexity comparing to RLS and APA algorithms. The results are taken for both input signal as speech signal and noise separately and plotted in the results section.

  • 8.
    Adapa, Sasank Sai Sujan
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    APPLYING LEAN PRINCIPLES FOR PERFORMANCE ORIENTED SERVICE DESIGN OF VIRTUAL NETWORK FUNCTIONS FOR NFV INFRASTRUCTURE: Concepts of Lean2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Context. Network Function Virtualization was recently proposed by European Telecommunications Standards Institute (ETSI) to improve the network service flexibility by virtualization of network services and applications that run on hardware. To virtualize network functions, the software is decoupled from underlying physical hardware. NFV aims to transform industries by reducing capital investments on hardware by using commercial-of-the-shelf (COTS) hardware. NFV makes rapid innovative growth in telecom services through software based service deployment.

    Objectives. This thesis work aims to investigate how business organizations function and the roles in defining a service relationship model. The work also aims to define a service relationship model and to validate it via proof of concept using network function virtualization as a service. For this thesis, we finally apply lean principles for the defined service relationship model to reduce waste and investigate how lean benefits the model to be proven as performance service oriented.

    Methods. The essence of this work is to make a business organization lean by investigating its actions and applying lean principles. To elaborate, this thesis work involves in a research of papers from IEEE, TMF, IETF and Ericsson. It results in modelling of a PoC by following requirement analysis methodology and by applying lean principles to eliminate unnecessary processes which doesn’t add any value.

    Results. The results of the work include a full-fledged service relationship model that include three service levels with roles that can fit in to requirement specifications of NFV infrastructure. The results also show the service levels functionalities and their relationships between the roles. It has also been observed that the services that are needed to be standardized are defined with syntax for ways to describe network functions. It is observed that lean principles benefit the service relationship model from reducing waste factors and hereby providing a PoC which is performance service oriented.

    Conclusions. We conclude that roles defined are fit for the service relationship model designed. Moreover, we conclude that the model can hence contain the flow of service by standardizing the subservices and reducing waste interpreted with lean principles and there is a need for further use case proof of the model in full scale industry trials. It also concludes the ways to describe network functions syntax which follows lean principles that are essential to have them for the sub-services standardization. However, PoC defined can be an assurance to the NFV infrastructure.

  • 9.
    Addu, Raj Kiran
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Potuvardanam, Vinod Kumar
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Effect of Codec Performance on Video QoE for videos encoded with Xvid, H.264 and WebM/VP82014Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    In recent years, there has been a significant growth in multimedia services such as mobile video streaming, Video-on-Demand and video conferencing. This has led to the development of various video coding techniques, aiming to deliver high quality video while using available bandwidth efficiently. This upsurge in the usage of video applications has also resulted in making endusers more quality-conscious. In order to meet the users’ expectations, the Quality of Experience (QoE) studies has gained utmost importance from both researchers and service providers. This thesis aims to compare the performance of H.264/AVC, Xvid and WebM/VP8 video codecs in wired and wireless networks. The codec performance is evaluated for different packet loss and delay variation values. The evaluation of codec performance is done using both subjective and objective assessment methods. In subjective assessment method, the evaluation of video codec performance is done using ITU-T recommended Absolute Category Rating (ACR) method. Using this method the perceptual video quality ratings are taken from the users, which are then averaged to obtain Mean Opinion Score. These obtained scores are used to analyze the performance of encoded videos with respect to users’ perception. In addition to subjective assessment method, the quality of encoded video is also measured using objective assessment method. The objective metric SSIM (Structural Similarity) is used to evaluate the performance of encoded videos. Based on the results, it was found that for lower packet loss and delay variation values H.264 showed better results when compared to Xvid and WebM/VP8 whereas, WebM/VP8 outperformed Xvid and H.264 for higher packet loss and delay variation values. On the whole, H.264 and WebM/VP8 performed better than Xvid. It was also found that all three video codecs performed better in wired network when compared to the wireless network.

  • 10.
    Adebomi, OYEKANLU Emmanuel
    et al.
    Blekinge Institute of Technology, School of Computing.
    Mwela, JOHN Samson
    Blekinge Institute of Technology, School of Computing.
    Impact of Packet Losses on the Quality of Video Streaming2010Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    In this thesis, the impact of packet losses on the quality of received videos sent across a network that exhibit normal network perturbations such as jitters, delays, packet drops etc has been examined. Dynamic behavior of a normal network has been simulated using Linux and the Network Emulator (NetEm). Peoples’ perceptions on the quality of the received video were used in rating the qualities of several videos with differing speeds. In accordance with ITU’s guideline of using Mean Opinion Scores (MOS), the effects of packet drops were analyzed. Excel and Matlab were used as tools in analyzing the peoples’ opinions which indicates the impacts that different loss rates has on the transmitted videos. Statistical methods used for evaluation of data are mean and variance. We conclude that people have convergence of opinions when losses become extremely high on videos with highly variable scene changes

  • 11.
    Adeleke, Adesina
    Blekinge Institute of Technology, School of Management.
    How External Forces are influencing the Ebusiness strategy of MTN-Nigeria2009Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    The Internet and e-business has had enormous impact on many companies in Nigeria and there has been much research on how e-business influences the environment, but little can be found on how the environment of a developing country like Nigeria influences e-business. In e-business, technology tells the business what can be done in smarter ways. Technology not only can make business more efficient but also can make business more effective in targeting and reaching markets, however technology cannot enhance business in isolation as there are other vital factors that equally impact business. This thesis presents an adapted version of the PESTEL (Political, Economic, Socio cultural, Technology, Environment, and Legal) framework so called e-business PESTEL framework, as a method for structural analysis of macro environment forces in the future. In addition to this PESTEL framework, the Porter’s five forces model was employed to analyse the industrial forces that also influence MTNN e-business strategy. The main goal of this research is to give an overview of industry and macro-environment forces influencing the e-business strategy MTN-Nigeria and the impact of future developments. The research methodology was explorative and descriptive. A further method for future analysis of the macro-environments influences and a suggestion on how to incorporate it in this research work is given. The e-business strategy of MTNN consists of four areas: E-procurement, E-collaboration (CRM), Supply chain management and E-commerce. The influences found on macro-environments level are political and sociocultural forces and in the industry levels are bargaining power of customers and suppliers of its products and services .The most recommendations are that MTN-Nigeria should add e-business PESTEL framework described in this thesis to its e-business strategy check. Furthermore MTNN should include environment analysis more extensively in their e-business strategy approach as the factors in this research work shape the environment in which it carries out its business.

  • 12.
    ADHIKARLA, VAMSI KIRAN
    Blekinge Institute of Technology, School of Engineering.
    3D VIDEO FORMAT CONVERSION2011Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The main aim of this thesis work is to find/implement various methods that convert Conventional Stereoscopic 3D Video (CSV) to Multiview video (MVV). The work investigates different methods that can produce multiple views given a stereoscopic pair from a frame of a particular video sequence and continues with the process of selecting the best among investigated methods that has optimum quality and speed. In contrast to the existing algorithms, this work disregards the physical depth but instead focus on pixel value correspondence. The intermediate view generation in this work is not considered as a geometrical problem, but a morphing problem. Different morphing algorithms (mesh, field and thin plate spline morphing techniques) are considered for conversion. Performance of each morphing algorithm is in turn compared using different correspondence matching techniqes. The investigated methods aim to produce arbitrary number of novel synthesized camera views from a sparse view set. Mesh morphing algorithm is found to be a better candidate in terms of signal to noise ratio, but requires accurate correspondences at edges of an object in a particular scene and also needs more execution time to generate more number of views. A new approach to field morphing has been introduced in this thesis work, which performs better in terms of execution time and also found to produce intermediate views with reasonable signal to noise ratio. This approach is observed to bring good trade off between speed and accuracy. This conversion has an advantage it can be used as a decompression mechanism that can produce multiple views required for an Autostereoscopic 3D display from a stereoscopic left and right pair. This approach also brings the benefit of backward compatibility as present standards for CSV may be used to provide multiview 3D video to high fidelity Autostereoscopic 3D displays of the future. This work has applications in free view point television, video conferencing systems etc.,

  • 13.
    Adolfsson, Henrik
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Svensson, Peter
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Design and implementation of the MMS portal2006Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [en]

    MMS-enabled terminals on the market today are very complicated to use. It takes several steps to create a multi-slide MMS-message with images and text. This discourages users from using it. To increase usage of MMS, several companies provide web-based or stand-alone programs that allow users to create and send MMS-messages from a regular computer. However these editors have many limitations and are not user-friendly. This thesis describes the design and implementation of a user-friendly web-based MMS-portal where users can create, edit and send MMS-messages. The portal is integrated into Densitet’s system for development of mobile services. Conclusions that can be draw from this work are that problems with MMS interoperability have mostly the poor standardization to blame. Different terminals support different types of images and sound formats, and to make the MMS-portal user-friendly, format conversions of uploaded content had to be implemented. Also the MMS-portal only supports basic MMS-functionality. If the MMS-specification includes more audio and image formats and if the MMS-terminals are upgraded to handle these formats, sending MMS-messages will be easier and mobile messaging will continue to grow.

  • 14. Adolfsson, Stefan
    On Automatic Detection of Burn-through Using a Parametric Model1995Report (Other academic)
  • 15. Adolfsson, Stefan
    Quality Monitoring in Pulsed GMA Welding Using Modern Signal Processing Methods1995Licentiate thesis, comprehensive summary (Other academic)
  • 16. Adolfsson, Stefan
    Quility Monitoring in Robotised Short Circuiting GMA Welding1997Report (Other academic)
    Abstract [en]

    This paper addresses the problem of automatic monitoring the weld quality produced by robotised short arc welding. A simple statistical change detection algorithm for the weld quality, recursive Sequential Probability Ratio Test (SPRT), is used. The algorithm may equivalently be viewed as a cumulative sum (CUSUM) - type test. The test statistics is based upon the variance of the amplitude of the weld voltage. The performance of the algorithm is evaluated using experimental data. The results obtained from the algorithm indicate that it is possible to detect changes in the weld quality automatically and on-line.

  • 17. Adolfsson, Stefan
    et al.
    Bahrami, Ali
    Bolmsjö, Gunnar
    Claesson, Ingvar
    Automatic quality monitoring in robotised GMA welding using a repeated sequential probability ratio test method1997In: International Journal for the Joining of Materials, ISSN 0905-6866, Vol. 9, no 1, 2-8 p.Article in journal (Refereed)
  • 18. Adolfsson, Stefan
    et al.
    Bahrami, Ali
    Claesson, Ingvar
    A Sequential Probability Ratio Test Method for Quality Monitoring in Robotised GMA Welding1997Conference paper (Refereed)
    Abstract [en]

    This paper deals with the problem of automatic monitoring the weld quality when welding with Gas Metal Arc (GMA) in short circuiting mode. Experiments with two different types of T-joints are performed in order to provoke optimal and non-optimal welding conditions. During the experiments, voltage and current are measured from the welding process. A simple statistical change detection algorithm for the weld quality, the repeated Sequential Probability Ratio Test (SPRT), is used. The algorithm can equivalently be viewed as a cumulative sum (CUSUM) - type test. The test statistics is based upon the fluctuations of amplitude in the weld voltage. It is shown that the fluctuations of the weld voltage amplitude decreases when the welding process is not operating under optimal condition. The results obtained from the experiments indicate that it is possible to detect changes in the weld quality automatically and on-line.

  • 19. Adolfsson, Stefan
    et al.
    Bahrami, Ali
    Claesson, Ingvar
    Quality Monitoring in Robotised Welding using Sequential Probability Ratio test1996Conference paper (Refereed)
    Abstract [en]

    This paper addresses the problem of automatic monitoring the weld quality produced by robotised short arc welding. A simple statistical change detection algorithm for the weld quality, recursive sequential probability ratio test (SPRT), is used. The algorithm may equivalently be viewed as a cumulative sum (CUSUM) type test. The test statistics is based upon the variance of the amplitude of the weld voltage. It is shown that the variance of the weld voltage amplitude decreases when the welding process is not operating under optimal condition. The performance of the algorithm is evaluated using experimental data. The results obtained from the algorithm indicate that it is possible to detect changes in the weld quality automatically and on-line

  • 20. Adolfsson, Stefan
    et al.
    Bahrami, Ali
    Claesson, Ingvar
    Bolmsjö, Gunnar
    On-line quality monitoring in short: circuit gas metal arc welding1999In: Welding Journal, ISSN 0043-2296, Vol. 78, no 2, 59S-73S p.Article in journal (Refereed)
    Abstract [en]

    This paper addresses the problems involved in the automatic monitoring of the weld quality produced by robotized short-arc welding. A simple statistical change detection algorithm for the weld quality, the repeated Sequential Probability Ratio Test (SPRT), was used. The algorithm may similarly be viewed as a cumulative sum (CUSUM) type test, and is well-suited to detecting sudden minor changes in the monitored test statistic. The test statistic is based on the variance of the weld voltage, wherein it will be shown that the variance decreases when the welding process is not operating under optimal conditions. The performance of the algorithm is assessed through the use of experimental data. The results obtained from the algorithm show that it is possible to detect changes in weld quality automatically and on-line.

  • 21. Adolfsson, Stefan
    et al.
    Ericson, Klas
    Grennberg, Anders
    Automatic Detection of Burn-through in GMA Welding Using a Parametric Model1996In: Mechanical Systems & Signal Processing, ISSN 0888-3270 , Vol. 10, no 5, 633-651 p.Article in journal (Refereed)
    Abstract [en]

    This paper addresses the problem of automatic detection of burn-through in weld joints. Gas metal are (GMA) welding with pulsed current is used, and welding voltage and current are recorded. As short-circuitings are common between the welding electrode and the work piece during burn-through, a short-circuit detector is developed to detect these events. To detect another specific characteristic of burn-through-a broadband long-lasting voltage component-this detector is combined with a square-law detector. This second detector is based on a non-linear modification of an autoregressive model with extra input (ARX-model) of the welding process. The results obtained from this compound detector indicate that it is possible to detect burn-through in the welds automatically. The work also indicates that it is possible to design an on-line monitoring system for robotic GMA welding.

  • 22. Adolfsson, Stefan
    et al.
    Ericson, Klas
    Gustavsson, Jan-Olof
    Ågren, Björn
    Quality Monitoring for Pulsed Arc Welding1994Conference paper (Refereed)
  • 23. Adolfsson, Stefan
    et al.
    Ericson, Klas
    Ågren, Björn
    On Automatic Detection of Burn-through in GMA Welding: Weld Voltage Analysis1995Report (Other academic)
  • 24.
    Advaita, Advaita
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Gali, Mani Meghala
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Performance Analysis of a MIMO Cognitive Cooperative Radio Network with Multiple AF Relays2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the rapid growth of wireless communications, the demand for the various multimedia services is increasing day by day leading to a deficit in the frequency spectrum resources. To overcome this problem, the concept of cognitive radio technology has been proposed which allows the unlicensed secondary user (SU) to access the licensed spectrum of the primary user (PU), thus improving the spectrum utilization. Cooperative communications is another emerging technology which is capable of overcoming many limitations in wireless systems by increasing reliability and coverage. The transmit and receive diversity techniques such as orthogonal space–time block codes (OSTBCs) and selection combining (SC) in multiple-input multiple-output (MIMO) cognitive amplify and forward relay networks help to reduce the effects of fading, increase reliability and extend radio coverage.

     

    In this thesis, we consider a MIMO cognitive cooperative radio network (CCRN) with multiple relays. The protocol used at the relays is an amplify and forward protocol. At the receiver, the SC technique is applied to combine the signals. Analytical expressions for the probability density function (PDF) and cumulative distribution function (CDF) of the signal-to-noise ratio (SNR) are derived. On this basis, the performance in terms of outage probability is obtained. Mathematica has been used to generate numerical results from the analytical expressions. The system model is simulated in MATLAB to verify the numerical results. The performance analysis of the system model is hence done in terms of outage probability.

  • 25.
    Afaq, Muhammad
    et al.
    Blekinge Institute of Technology, School of Engineering.
    Faheem, Sahibzada Muhammad
    Blekinge Institute of Technology, School of Engineering.
    Performance Analysis of Selected Cooperative Relaying Techniques2010Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Recently, cooperative communication has gained significant interest due to the fact that it exploits spatial diversity and provides capacity/performance gain over conventional single- input single-output (SISO) systems. A mobile node with single antenna can cooperate with a nearby mobile node having single antenna in multi-user environment to create the effect of virtual multiple antenna system. Hence, reducing the complexity associated with actual multiple antenna systems. Despite the small size and power constraints, a mobile node can still benefit from spatial diversity by employing cooperation, thus saving transmission power and increasing the coverage range of the network. In this thesis, we have selected some of relaying protocols, namely, amplify-and-forward, decode-and-forward, detect-and-forward, and selective detect-and-forward that are studied and implemented for two different relaying geometries, i.e. equidistant and collinear. Results are studied and compared with each other to show the performance of each protocol in terms of average symbol error probabilities. The considered system model has three nodes, i.e. source, relay, destination. Communicating nodes are considered to be half-duplex with single antenna for transmission and reception. The source, when communicating with the destination, broadcasts the information, which is heard by the nearby relay. The relay then uses one of the cooperation protocols. Finally, the relayed signal reaches the destination, where it is detected by maximal ratio combiner (MRC) and combined with the direct transmission for possible diversity gains. The transmission path or the channel is modeled as a frequency non-selective Rayleigh fading in the presence additive white Gaussian noise (AWGN). The effect of path loss has been observed on cooperation for collinear arrangement with exponential decay up to four. Considering equidistant arrangement, decode-and-forward shows good performance at high signal-to-noise ratio (SNR) while amplify-and-forward is very promising for very low SNR. A selective relaying scheme called selective detect-and- forward is also presented which outperforms its fixed counterparts for a wide range of SNR.

  • 26.
    Aftab, Adnan
    et al.
    Blekinge Institute of Technology, School of Computing.
    Mufti, Muhammad Nabeel
    Blekinge Institute of Technology, School of Computing.
    Spectrum sensing through implementation of USRP22011Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Scarcity of the wireless spectrum has led to the development of new techniques for better utilization of the wireless spectrum. Demand for high data rates and better voice quality is resulting in the development of new wireless standard making wireless spectrum limited than ever. In this era of wireless communication, service providers and telecom operators are faced with a dilemma where they need a large sum of the wireless spectrum to meet the ever increasing quality of service requirements of consumers. This has led to the development of spectrum sensing techniques to find the unused spectrum in the available frequency band. The results presented in this thesis will help out in developing clear understanding of spectrum sensing techniques. Comparison of different spectrum sensing approaches. The experiments carried out using USRP2 and GNU radio will help the reader to understand the concept of underutilized frequency band and its importance in Cognitive Radios.

  • 27.
    Ahmad, Nadeem
    et al.
    Blekinge Institute of Technology, School of Computing.
    Habib, M. Kashif
    Blekinge Institute of Technology, School of Computing.
    Analysis of Network Security Threats and Vulnerabilities by Development & Implementation of a Security Network Monitoring Solution2010Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Communication of confidential data over the internet is becoming more frequent every day. Individuals and organizations are sending their confidential data electronically. It is also common that hackers target these networks. In current times, protecting the data, software and hardware from viruses is, now more than ever, a need and not just a concern. What you need to know about networks these days? How security is implemented to ensure a network? How is security managed? In this paper we will try to address the above questions and give an idea of where we are now standing with the security of the network.

  • 28.
    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.

  • 29.
    Ahmad, Waqas
    et al.
    Blekinge Institute of Technology, School of Engineering.
    Aslam, Muhammad Kashif
    Blekinge Institute of Technology, School of Engineering.
    An investigation of Routing Protocols in Wireless Mesh Networks (WMNs) under certain Parameters2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Wireless Mesh Networks (WMNs) are bringing revolutionary change in the field of wireless networking. It is a trustworthy technology in applications like broadband home networking, network management and latest transportation systems. WMNs consist of mesh routers, mesh clients and gateways. It is a special kind of wireless Ad-hoc networks. One of the issues in WMNs is resource management which includes routing and for routing there are particular routing protocols that gives better performance when checked with certain parameters. Parameters in WMNs include delay, throughput, network load etc. There are two types of routing protocols i.e. reactive protocols and proactive protocols. Three routing protocols AODV, DSR and OLSR have been tested in WMNs under certain parameters which are delay, throughput and network load. The testing of these protocols will be performed in the Optimized Network Evaluation Tool (OPNET) Modeler 14.5. The obtained results from OPNET will be displayed in this thesis in the form of graphs. This thesis will help in validating which routing protocol will give the best performance under the assumed conditions. Moreover this thesis report will help in doing more research in future in this area and help in generating new ideas in this research area that will enhance and bring new features in WMNs.

  • 30.
    Ahmad, Zunnurain
    Blekinge Institute of Technology, School of Engineering.
    Design and Implementation of Quasi Planar K-Band Array Antenna Based on Travelling Wave Structures2013Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Designing antenna arrays based on travelling wave structures has been studied extensively during the past couple of decades and literature on several array topologies is present. It has been an active area of research as constant improvement of antenna arrays is desired for different communication systems developed. Slotted waveguide antennas are one form of travelling wave structures which is adapted in this study due to several advantages offered over other planar array structures. Waveguide slots have been used for a couple of decades as radiating elements. Several design studies have been carried out regarding use of slots with different orientations and geometry and cascading them together to be used as array antennas. Waveguide antennas are preferred as they provide low losses in the feed structure and also offer good radiation characteristics. This study provides a design procedure for implementing a circular polarized planar antenna array based on slotted waveguide structures. The antenna is designed to work in the 19.7 - 20.2 GHz range which is the operating frequency for the downlink of satellites.

  • 31.
    Ahmadi Mehri, Vida
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    An Investigation of CPU utilization relationship between host and guests in a Cloud infrastructure2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cloud computing stands as a revolution in IT world in recent years. This technology facilitates resource sharing by reducing hardware costs for business users and promises energy efficiency and better resource utilization to the service providers. CPU utilization is a key metric considered in resource management across clouds.

    The main goal of this thesis study is directed towards investigating CPU utilization behavior with regard to host and guest, which would help us in understanding the relationship between them. It is expected that perception of these relationships would be helpful in resource management.

    Working towards our goal, the methodology we adopted is experi- mental research. This involves experimental modeling, measurements and observations from the results. The experimental setup covers sev- eral complex scenarios including cloud and a standalone virtualization system. The results are further analyzed for a visual correlation.

    Results show that CPU utilization in cloud and virtualization sce- nario coincides. More experimental scenarios are designed based on the first observations. The obtaining results show the irregular behav- ior between PM and VM in variable workload.

    CPU utilization retrieved from both cloud and a standalone system is similar. 100% workload situations showed that CPU utilization is constant with no correlation co-efficient obtained. Lower workloads showed (more/less) correlation in most of the cases in our correlation analysis. It is expected that more number of iterations can possibly vary the output. Further analysis of these relationships for proper resource management techniques will be considered. 

  • 32.
    ahmed, amar
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Performance and Modeling of SIP Session Setup2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    During the recent last years, transport of multimedia sessions, such as audio streams and video conferences, over IP has acquired a lot of attention since most of communication technologies are migrating to work over IP. However, sending media streams over IP networks has encountered some problems related to signaling issues. The ongoing research in this area has produced some solutions to this subject. Internet Engineering Task Force (IETF) has introduced Session Initiation Protocol (SIP), which has proved to be an efficient protocol for controlling sessions over IP. While a great deal of research performed in evaluating the performance of SIP and comparing it with its competent protocols such as H.323, studying the delay caused by initiating the session has acquired less attention. In this document, we have addressed the SIP session setup delay problem. In the lab, we have built up a test bed for running several SIP session scenarios. Using different models for those scenarios, we have measured session setup delays for all used models. The analysis performed for each model showed that we could propose some models to be applied for SIP session setup delay components.

  • 33.
    Ahmed, Ashraf AwadElkarim Widaa
    et al.
    Blekinge Institute of Technology, School of Engineering.
    Makki, Ahmed Hamza Ibrahim
    Blekinge Institute of Technology, School of Engineering.
    Performance Evaluation of Uplink Multiple Access Techniques in LTE Mobile Communication System2010Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The User Equipments (UE) nowadays are able to provide various internet applications and services that raise the demand for high speed data transfer and Quality of Service (QoS). Accordingly, next generation mobile communication systems driven by these demands are expected to provide higher data rates and better link quality compared to the existing systems. Orthogonal Frequency Division Multiple Access (OFDMA) and Single Carrier Frequency Division Multiple Access (SC-FDMA) are strong multiple access candidates for the uplink of the International Mobile Telecommunications-Advanced (IMT-Advanced). These multiple access techniques in combination with other promising technologies such as multi-hops transmission and Multiple-Input-Multiple-Output (MIMO) will be utilized to reach the targeted IMT-Advanced system performance. In this thesis, OFDMA and SC-FDMA are adopted and studied in the uplink of Long Term Evolution (LTE). Two transmission scenarios are considered, namely the single hop transmission and the relay assisted transmission (two hops). In addition, a hybrid multiple access technique that combines the advantages of OFDMA and SC-FDMA in term of low Peak-to-Average Power Ratio (PAPR) and better link performance (in terms of Symbol Error Rate (SER)) has been proposed in relay assisted transmission scenario. Simulation results show that the proposed hybrid technique achieves better end-to-end link performance in comparison to the pure SC-FDMA technique and maintains the same PAPR value in access link. In addition, a lower PAPR is achieved compared to OFDMA case, which is an important merit in the uplink transmission due to the UE’s power resources constraint (limited battery power).

  • 34.
    Ahmed, Ishtiaque
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Study of the Local Backprojection Algorithm for Image Formation in Ultra Wideband Synthetic Aperture Radar2008Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The purpose of this thesis project is to study and evaluate a UWB Synthetic Aperture Radar (SAR) data image formation algorithm, that was previously less familiar and, that has recently got much attention in this field. Certain properties of it made it acquire a status in radar signal processing branch. This is a fast time-domain algorithm named Local Backprojection (LBP). The LBP algorithm has been implemented for SAR image formation. The algorithm has been simulated in MATLAB using standard values of pertinent parameters. Later, an evaluation of the LBP algorithm has been performed and all the comments, estimation and judgment have been done on the basis of the resulting images. The LBP has also been compared with the basic time-domain algorithm Global Backprojection (GBP) with respect to the SAR images. The specialty of LBP algorithm is in its reduced computational load than in GBP. LBP is a two stage algorithm — it forms the beam first for a particular subimage and, in a later stage, forms the image of that subimage area. The signal data collected from the target is processed and backprojected locally for every subimage individually. This is the reason of naming it Local backprojection. After the formation of all subimages, these are arranged and combined coherently to form the full SAR image.

  • 35.
    Ahmed, Mamun
    Blekinge Institute of Technology, School of Engineering.
    Adaptive Sub band GSC Beam forming using Linear Microphone-Array for Noise Reduction/Speech Enhancement.2012Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    This project presents the description, design and the implementation of a 4-channel microphone array that is an adaptive sub-band generalized side lobe canceller (GSC) beam former uses for video conferencing, hands-free telephony etc, in a noisy environment for speech enhancement as well as noise suppression. The side lobe canceller evaluated with both Least Mean Square (LMS) and Normalized Least Mean Square (NLMS) adaptation. A testing structure is presented; which involves a linear 4-microphone array connected to collect the data. Tests were done using one target signal source and one noise source. In each microphone’s, data were collected via fractional time delay filtering then it is divided into sub-bands and applied GSC to each of the subsequent sub-bands. The overall Signal to Noise Ratio (SNR) improvement is determined from the main signal and noise input and output powers, with signal-only and noise-only as the input to the GSC. The NLMS algorithm significantly improves the speech quality with noise suppression levels up to 13 dB while LMS algorithm is giving up to 10 dB. All of the processing for this thesis is implemented on a computer using MATLAB and validated by considering different SNR measure under various types of blocking matrix, different step sizes, different noise locations and variable SNR with noise.

  • 36.
    Ahmed, Sabbir
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Performance of Multi-Channel Medium Access Control Protocol incorporating Opportunistic Cooperative Diversity over Rayleigh Fading Channel2006Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    This thesis paper proposes a Medium Access Control (MAC) protocol for wireless networks, termed as CD-MMAC that utilizes multiple channels and incorporates opportunistic cooperative diversity dynamically to improve its performance. The IEEE 802.11b standard protocol allows the use of multiple channels available at the physical layer but its MAC protocol is designed only for a single channel. The proposed protocol utilizes multiple channels by using single interface and incorporates opportunistic cooperative diversity by using cross-layer MAC. The new protocol leverages the multi-rate capability of IEEE 802.11b and allows wireless nodes far away from destination node to transmit at a higher rate by using intermediate nodes as a relays. The protocol improves network throughput and packet delivery ratio significantly and reduces packet delay. The performance improvement is further evaluated by simulation and analysis.

  • 37. Ahmed, Sabbir
    et al.
    Casas, Christian Ibar
    Coso, Aitor del
    Mohammed, Abbas
    Performance of Multi-Channel MAC incorporating Opportunistic Cooperative Diversity2007Conference paper (Refereed)
  • 38. Aibinu, A.M.
    et al.
    Iqbal, Muhammad Imran
    Nilsson, M.
    Salami, M.J.E.
    A New Method of Correcting Uneven Illumination Problem in Fundus Images2007Conference paper (Refereed)
    Abstract [en]

    Recent advancements in signal and image processing have reduced the time of diagnoses, effort and pressure on the screeners by providing auto diagnostic tools for different diseases. The success rate of these tools greatly depend on the quality of acquired images. Bad image quality can significantly reduce the specificity and the sensitivity which in turn forces screeners back to their tedious job of manual diagnoses. In acquired fundus images, some areas appear to be brighter than the other, that is areas close to the center of the image are always well illuminated, hence appear very bright while areas far from the center are poorly illuminated hence appears to be very dark. Several techniques including the simple thresholding, Naka Rushton (NR) filtering technique and histogram equalization (HE) method have been suggested by various researchers to overcome this problem. However, each of these methods has limitations at their own and hence the need to develop a more robust technique that will provide better performance with greater flexibility. A new method of compensating uneven (irregular) illumination in fundus images termed global-local adaptive histogram equalization using partially-overlapped windows (GLAPOW) is proposed in this paper. The developed algorithm has been tested and the results obtained show superior performance when compared to other known techniques for uneven illumination correction.

  • 39. Aibinu, A.M.
    et al.
    Iqbal, Muhammad Imran
    Nilsson, M.
    Salami, M.J.E.
    Automatic Diagnosis of Diabetic Retinopathy from Fundus Images Using Digital Signal and Image Processing Techniques2007Conference paper (Refereed)
    Abstract [en]

    Automatic diagnosis and display of diabetic retinopathy from images of retina using the techniques of digital signal and image processing is presented in this paper. The acquired images undergo pre-processing to equalize uneven illumination associated with the acquired fundus images. This stage also removes noise present in the image. Segmentation stage clusters the image into two distinct classes while the abnormalities detection stage was used to distinguish between candidate lesions and other information. Methods of diagnosis of red spots, bleeding and detection of vein-artery crossover points have also been developed in this work using the color information, shape, size, object length to breadth ration as contained in the acquired digital fundus image. Furthermore, two graphical user interfaces (GUIs) have also been developed during this work; the first is for the collection of lesion data information and was used by the ophthalmologist in marking images for database while the second GUI is for automatic diagnosing and displaying of the result in a user friendly manner. The algorithm was tested with a separate set of 25 fundus images. From this, the result obtained for microaneurysms and haemorrhages diagnosis shows the appropriateness of the method.

  • 40. Aibinu, A.M.
    et al.
    Iqbal, Muhammad Imran
    Shafie, A.A.
    Salami, M.J.E.
    Nilsson, Mikael
    Vascular intersection detection in retina fundus images using a new hybrid approach2010In: Computers in Biology and Medicine, ISSN 0010-4825, E-ISSN 1879-0534, Vol. 40, no 1, 81-89 p.Article in journal (Refereed)
    Abstract [en]

    The use of vascular intersection aberration as one of the signs when monitoring and diagnosing diabetic retinopathy from retina fundus images (FIs) has been widely reported in the literature. In this paper, a new hybrid approach called the combined cross-point number (CCN) method able to detect the vascular bifurcation and intersection points in FIs is proposed. The CCN method makes use of two vascular intersection detection techniques, namely the modified cross-point number (MCN) method and the simple cross-point number (SCN) method. Our proposed approach was tested on images obtained from two different and publicly available fundus image databases. The results show a very high precision, accuracy, sensitivity and low false rate in detecting both bifurcation and crossover points compared with both the MCN and the SCN methods.

  • 41.
    Aida, Horaniet
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Isabel, Llorente
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Formation of High Resolution Images in SAR using GNSS2009Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [en]

    The aim of this thesis is to investigate the possibility to form high resolution Synthetic Aperture Radar (SAR) images using the Global Navigation Satellite System (GNSS) Galileo, GPS and Glonas, In particular the thesis study the GPS signal and evaluate its properties for bistatic case. The report is based on the fact that Galileo and GPS are both positioning systems with similar characteristics. The difference is mainly that Galileo System uses a larger number of satellites and a different modulation scheme to improve the efficiency of the system, resulting in a better accuracy. On the topic of GNSS SAR, the report will be described with modes, resolution, geometry and algorithms. It is also explained the Space Surface Bi-static Radar and within two particular cases: parallel and non parallel paths

  • 42.
    Ajayi, Taiwo Seun
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Mobile Satellite Communications: Channel Characterization and Simulation2007Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    Abstract: The channel characterization of a mobile satellite communication which is an important and fast growing arm of wireless communication plays an important role in the transmission of information through a propagation medium from the transmitter to the receiver with minimum barest error rate putting into consideration the channel impairments of different geographical locations like urban, suburban, rural and hilly. The information transmitted from satellite to mobile terminals suffers amplitude attenuation and phase variation which is caused by multipath fading and signal shadowing effects of the environment. These channel impairments are commonly described by three fading phenomena which are Rayleigh fading, Racian fading and Log-normal fading which characterizes signal propagation in different environments. They are mixed in different proportions by different researchers to form a model to describe a particular channel. In the thesis, the general overview of mobile satellite is conducted including the classification of satellite by orbits, the channel impairments, the advantages of mobile satellite communication over terrestrial. Some of the major existing statistical models used in describing different type of channels are looked into and the best out of them which is Lutz model [6] is implemented. By simulating the Lutz model which described all possible type of environments into two states which represent non-shadowed or LOS and shadowed or NLOS conditions, shows that the BER is predominantly affected by shadowing factor.

  • 43.
    Akbar, Mohamed Kazaludeen
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Performance Evaluation and Comparison of Coherent and Incoherent Receivers under Atmospheric Turbulence2014Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Optical free space communication system faces the major challenge because of the atmospheric condition. Signals receive in the ground station using two different types of receivers (Coherent detection and Intensity Modulation and Direct Detection (IM/DD)). Coherent detection uses PIN photo detector in the receiver end to attain the more sensitivity of the receiver. It receives the input data as a carrier signal and the local oscillator signal is mixed with the received signal and down convert the carrier signal to an intermediate frequency signal. The Intensity Modulation direct detection uses the Avalanche photo detector in the receiver end to attain the more sensitivity. This detection receives the input signal as a carrier signal and it is directly demodulated at the receiver back into the original signal. Signals receive in the ground station from the aircraft will be affected by the various types of noise like shot noise, thermal noise, etc. The occurrence of noises in the coherent detection is not exactly same as the IM/DD. Some noise get varies according to the electrical circuit noise produced in the receiver side. By deriving the signal-to-noise ratio, the background noise occur in the desired signal can be calculated. One of the main goals would be to derive a Probability Density Function (PDF) of the Signal-to-Noise Ratio (SNR) of the each type of receiver to check the efficiency of the receivers. Transmitting the optical signal from aircraft will face some data loss problem due to atmospheric turbulence disturbances, to identify the loss arises in the transmitting signal will be done by using the probability error method. Bit Error Rate (BER) derivation will take place to calculate and to identify the data loss occurs in the received signal. The project deals with measuring the efficiency and sensitivity among those two optical receivers and to check the robustness between those receivers against scintillations (power fades and surges) effects. In this work performance of the coherent receiver and IM/DD receiver using APD is compared with the different system characteristics. Sensitivity and performance of both the receivers are calculated with the same fading vector. Signal to noise ratio and bit error rate are theoretically derived and numerically analyzed in the case of atmospheric turbulence. Numerical results predict the performance of both the receivers.

  • 44.
    Akbar, Zeeshan
    et al.
    Blekinge Institute of Technology, School of Computing.
    Ali, Asar
    Blekinge Institute of Technology, School of Computing.
    Evaluation of AODV and DSR Routing Protocols of Wireless Sensor Networks for Monitoring Applications2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Deployment of sensor networks are increasing either manually or randomly to monitor physical environments in different applications such as military, agriculture, medical transport, industry etc. In monitoring of physical environments, the most important application of wireless sensor network is monitoring of critical conditions. The most important in monitoring application like critical condition is the sensing of information during emergency state from the physical environment where the network of sensors is deployed. In order to respond within a fraction of seconds in case of critical conditions like explosions, fire and leaking of toxic gases, there must be a system which should be fast enough. A big challenge to sensor networks is a fast, reliable and fault tolerant channel during emergency conditions to sink (base station) that receives the events. The main focus of this thesis is to discuss and evaluate the performance of two different routing protocols like Ad hoc On Demand Distance Vector (AODV) and Dynamic Source Routing (DSR) for monitoring of critical conditions with the help of important metrics like throughput and end-to-end delay in different scenarios. On the basis of results derived from simulation a conclusion is drawn on the comparison between these two different routing protocols with parameters like end-to-end delay and throughput.

  • 45.
    Akber, Raza
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Raza, Syed Aqeel
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Shafique, Usman
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Performance Evaluation of WiMAX2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The advancements in broadband and mobile communication has given many privileges to the subscribers for instance high speed data connectivity, voice and video applications in economical rates with good quality of services. WiMAX is an eminent technology that provides broadband and IP connectivity on “last mile” scenario. It offers both line of sight and non-line of sight wireless communication. Orthogonal frequency division multiple access is used by WiMAX on its physical layer. Orthogonal frequency division multiple access uses adaptive modulation technique on the physical layer of WiMAX and it uses the concept of cyclic prefix that adds additional bits at the transmitter end. The signal is transmitted through the channel and it is received at the receiver end. Then the receiver removes these additional bits in order to minimize the inter symbol interference, to improve the bit error rate and to reduce the power spectrum. In our research work, we investigated the physical layer performance on the basis of bit error rate, signal to noise ratio, power spectral density and error probability. These parameters are discussed in two different models. The first model is a simple OFDM communication model without the cyclic prefix, while the second model includes cyclic prefix.

  • 46.
    Akhter, Habiba
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Apodization Method in UWB SAR Imaging2014In: 2014 1ST INTERNATIONAL CONFERENCE ON ELECTRICAL ENGINEERING AND INFORMATION & COMMUNICATION TECHNOLOGY (ICEEICT 2014), IEEE Computer Society Digital Library, 2014Conference paper (Refereed)
    Abstract [en]

    Synthetic Aperture Radar (SAR) image processing involves a two dimensional (2-D) Fourier Transform (FT) and the spectrum shape introduces high intensity sidelobes. These sidelobes may severely distort the image. Apodization technique can decrease the sidelobes level while preserving the image resolution. However, in Ultra wideband (UWB) SAR imaging, we have to reduce both orthogonal and non-orthogonal sidelobes. In this paper, a new linear window function has been presented based on analysis of different linear and non-linear apodization techniques. This new linear method controls both orthogonal and non-orthogonal sidelobes better than other conventional window functions. This method has been applied and verified with a real SAR image.

  • 47.
    Akhter, Habiba
    Blekinge Institute of Technology, School of Engineering.
    Evaluation of weighting functions for Sidelobe control in UWB SAR image processing2013Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Ultra wideband (UWB) Synthetic Aperture Radar (SAR) holds huge possibilities for both terrestrial and celestial object sensing with excellent details which assists in science and technology. SAR systems associated with large antenna beamwidth, large signal bandwidth and low frequency operating in the VHF/UHF region is becoming gradually more popular because of their rising number of application in the areas of ground-penetrating radar (GPR) and foliage penetration radar (FOPEN). Apodization techniques in UWB SAR imaging have attracted significant interest in recent years for sidelobe suppression in SAR images. This technique is split into two groups: linear apodization and non-linear apodization. Linear apodization technique means to apply amplitude weighting functions in frequency domain prior to the final inverse Fourier transform requisite to appropriately focus on the SAR images. Both linear and non linear techniques can be used to suppress sidelobes level. Frequently used linear weighting functions are Hanning, Hamming and Blackman. Linear techniques can control the sidelobes level but image resolution reduces simultaneously. But non-linear techniques like Spatially Variant Apodization (SVA), Complex Duel Apodization and Dual-Apodization can suppress sidelobes and preserve the spatial resolution concurrently. However for these methods, it can be hard to understand how the output signal relates to input signal and also the phase information of image is lost. In this thesis paper, the main focus is, on apodization techniques to propose a new weighting function for sidelobe apodization and investigate it on real SAR images. In this thesis, we also study Impulse response (IPR) function for UWB SAR image processing. A two dimensional sinc function is used as an impulse response function for narrow band (NB) SAR system. This function can be obtained from a two dimensional Fourier Transform of a SAR image. This rectangular estimation is reasonable for narrow band and narrowbeam SAR. But for large bandwidth and wide integration angles, this approximation for the UWB SAR spectrum is not valid. It can provide erroneous SAR image quality measurements. To obtain precise image quality measurement, SAR image need to be generated for a range of different integration angle as UWB SAR systems are related with large integration angle to maintain azimuth focusing. So, in this work the choices of optimum windows have been investigated at different integration angles in order to see if there are large differences between NB SAR Apodization and UWB SAR Apodization.

  • 48.
    Akinwande, Gbenga Segun
    Blekinge Institute of Technology, School of Computing.
    Signaling Over Protocols Gateways in Next-Generation Networks2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    In this thesis, I examined various signalling both in wired and mobile networks, with more emphasis on SIGTRAN. The SIGTRAN is the protocol suite applicable in the current new generation and next-generation networks, most especially as it enables service provider to be able to interpolate both wireline and wireless services within the same architecture. This concept is an important component in today’s Triple-play communication, and hence this thesis has provided a broad view on Signalling and Protocol Gateways in Traditional and Next Generations Networks. Signal flow in a typical new generation network was examined by carrying out discrete event simulation of UMTS network using OPNET modeller 14.5. Through both Packet-Switching (PS) and Circuit-Switching (CS) signalling, I was able to examine the QoS on a UMTS. Precisely, I looked at throughput on UMTS network by implementing WFQ and MDRR scheduling schemes.

  • 49.
    Alahari, Yeshwanth
    et al.
    Blekinge Institute of Technology, School of Computing.
    Buddhiraja, Prashant
    Blekinge Institute of Technology, School of Computing.
    Analysis of packet loss and delay variation on QoE for H.264 andWebM/VP8 Codecs2011Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The popularity of multimedia services over Internet has increased in the recent years. These services include Video on Demand (VoD) and mobile TV which are predominantly growing, and the user expectations towards the quality of videos are gradually increasing. Different video codec’s are used for encoding and decoding. Recently Google has introduced the VP8 codec which is an open source compression format. It is introduced to compete with existing popular codec namely H.264/AVC developed by ITU-T Video Coding Expert Group (VCEG), as by 2016 there will be a license fee for H.264. In this work we compare the performance of H.264/AVC and WebM/VP8 in an emulated environment. NetEm is used as an emulator to introduce delay/delay variation and packet loss. We have evaluated the user perception of impaired videos using Mean Opinion Score (MOS) by following the International Telecommunication Union (ITU) Recommendations Absolute Category Rating (ACR) and analyzed the results using statistical methods. It was found that both video codec’s exhibit similar performance in packet loss, But in case of delay variation H.264 codec shows better results when compared to WebM/VP8. Moreover along with the MOS ratings we also studied the effect of user feelings and online video watching experience impacts on their perception.

  • 50.
    Alam, Md. Jobayer
    et al.
    Blekinge Institute of Technology, School of Engineering.
    Sujan, Shaha Mohammed Goni Abed
    Blekinge Institute of Technology, School of Engineering.
    Low Complexity Channel Estimation for OFDM Systems Based on LS and MMSE Estimators’2010Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    In this paper we investigate the block-type pilot channel estimation for orthogonal frequency-division multiplexing (OFDM) systems. The estimation is based on the minimum mean square error (MMSE) estimator and the least square (LS) estimator. We derive the MMSE and LS estimators’ architecture and investigate their performances. We prove that the MMSE estimator performance is better but computational complexity is high, contrary the LS estimator has low complexity but poor performance. For reducing complexity we proposed two different solutions which are the Simplified Least Square (SLS) estimator and the modified MMSE estimator. We evaluate estimator’s performance on basis of mean square error and symbol error rate for 16 QAM systems. We also evaluate estimator’s computational complexity.

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