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  • 13351. Yang, Zhe
    et al.
    Mohammed, Abbas
    Hult, Tommy
    Grace, David
    Downlink Coexistence Performance Assessment and Techniques for WiMAX Services from High Altitude Platform and Terrestrial Deployments2008In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 2008Article in journal (Refereed)
    Abstract [en]

    We investigate the performance and coexistence techniques for worldwide interoperability for microwave access (WiMAX) delivered from high altitude platforms (HAPs) and terrestrial systems in shared 3.5 GHz frequency bands. The paper shows that it is possible to provide WiMAX services from individual HAP systems. The coexistence performance is evaluated by appropriate choice of parameters, which include the HAP deployment spacing radius, directive antenna beamwidths based on adopted antenna models for HAPs and receivers. Illustrations and comparisons of coexistence techniques, for example, varying the antenna pointing offset, transmitting and receiving antenna beamwidth, demonstrate efficient ways to enhance the HAP system performance while effectively coexisting with terrestrial WiMAX systems.

  • 13352. Yang, Zhe
    et al.
    Mohammed, Abbas
    Hult, Tommy
    Grace, David
    Optimizing Downlink Coexistence Performance of WiMAX Services in HAP and Terrestrial Deployments in Shared Frequency Bands2007Conference paper (Refereed)
  • 13353.
    Yao, Yong
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    A Software Framework for Prioritized Spectrum Access in Heterogeneous Cognitive Radio Networks2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Today, the radio spectrum is rarely fully utilized. This problem is valid in more domains, e.g., time, frequency and geographical location. To provide an efficient utilization of the radio spectrum, the Cognitive Radio Networks (CRNs) have been advanced. The key idea is to open up the licensed spectrum to unlicensed users, thus allowing them to use the so-called spectrum opportunities as long as they do not harmfully interfere with licensed users. An important focus is laid on the limitation of previously reported research efforts, which is due to the limited consideration of the problem of competition among unlicensed users for spectrum access in heterogeneous CRNs. A software framework is introduced, which is called PRioritized Opportunistic spectrum Access System (PROAS). In PROAS, the heterogeneity aspects of CRNs are specifically expressed in terms of cross-layer design and various wireless technologies. By considering factors like ease of implementation and efficiency of control, PROAS provides priority scheduling based solutions to alleviate the competition problem of unlicensed users in heterogenous CRNs. The advanced solutions include theoretical models, numerical analysis and experimental simulations for performance evaluation. By using PROAS, three particular CRN models are studied, which are based on ad-hoc, mesh-network and cellular-network technologies. The reported results show that PROAS has the ability to bridge the gap between research results and the practical implementation of CRNs.

  • 13354.
    Yao, Yong
    Blekinge Institute of Technology, School of Computing.
    A Spectrum Decision Support System for Cognitive Radio Networks2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Cognitive Radio Networks (CRNs) offer a promising capability of alleviating the problem of spectrum insufficiency. In CRNs, the licensed spectrum channels are either exclusively reserved for licensed users or temporarily used by unlicensed users. The requirement for unlicensed users is to not harmfully impair the licensed users transmissions. Because of this, the unlicensed users must solve the task to decide which available channels should be selected. The selection process is often referred to as spectrum decision, with the aim to optimize the transmission performance of unlicensed users. A support system for CRNs is introduced, which is called Spectrum Decision Support System (SDSS). SDSS provides an intelligent spectrum decision strategy that integrates different decision making algorithms and takes into account various channel characterization parameters. The objective is to develop a scientific framework for decision making in CRNs, which involve theoretical analysis, simulation evaluation and practical implementation. Three important components of SDSS are discussed: 1) setting up an overlay decision maker, 2) prediction based spectrum decision strategy and 3) queuing modeling of CRNs. The reported results indicate the feasibility of the suggested algorithms.

  • 13355. Yao, Yong
    et al.
    Erman, David
    PlanetLab Automatic Control System2010Conference paper (Refereed)
    Abstract [en]

    PlanetLab provides a global scale environment for network research. It consists of numerous controllable computer nodes. However, due to that these nodes are deployed in various network domains, there exist experimental issues, regarding network latency, resource utilization, and unpredictable behaviors of nodes. Experimenters need to pay much attention to manually adjusting their selected nodes during the whole experimental process. PLACS is a novel tool system based on PlanetLab, and composed of node selection node management. It can intelligently and automatically coordinate the involved elements, including PlanetLab nodes, experimental programs and experimenter requirements. In this article, the corresponding mechanism functionalities and implementation designs for development are presented.

  • 13356. Yao, Yong
    et al.
    Erman, David
    Popescu, Adrian
    Spectrum Decision for Cognitive Radio Networks2011Conference paper (Refereed)
    Abstract [en]

    Cognitive Radio Networks (CRNs) are a key technology suggested to be part of 4G and beyond. The fundamental concept is to let Secondary Users (SUs) have temporal free access to spectrum bands not occupied by Primary Users (PUs). Since SUs are not allowed to cause harmful interference to PUs, SUs need to select the most available spectrum bands for access, also known as spectrum decision. In the paper, we suggest a middleware called Spectrum Decision Support System (SDSS) abstractly illustrated. The goal of SDSS is to combine the different decision methods together and to make intelligent band selection based upon partial characterizations of CRNs

  • 13357.
    Yao, Yong
    et al.
    Blekinge Institute of Technology, School of Computing.
    Ngoga, Said Rutabayiro
    Blekinge Institute of Technology, School of Computing.
    Erman, David
    Blekinge Institute of Technology, School of Computing.
    Popescu, Adrian
    Blekinge Institute of Technology, School of Computing.
    Competition-Based Channel Selection for Cognitive Radio Networks2012Conference paper (Refereed)
    Abstract [en]

    In cognitive radio networks, unlicensed users need to learn from environmental changes. This is a process that can be done in a cooperative or non-cooperative manner. Due to the competition for channel utilization among unlicensed users, the non-cooperative approach may lead to overcrowding in the available channels. This paper is about a fuzzy-logic based decision making algorithm for competition-based channel selection. The underlying decision criterion integrates both the statistics of licensed users' channel occupancy and the competition level of unlicensed users. By using such an algorithm, the unlicensed user competitors can achieve an efficient sharing of the available channels. Simulation results are reported to demonstrate the performance and effectiveness of our suggested algorithm.

  • 13358.
    Yao, Yong
    et al.
    Blekinge Institute of Technology, School of Computing.
    Ngoga, Said Rutabayiro
    Blekinge Institute of Technology, School of Computing.
    Erman, David
    Blekinge Institute of Technology, School of Computing.
    Popescu, Adrian
    Blekinge Institute of Technology, School of Computing.
    Performance of Cognitive Radio Spectrum Access with Intra- and Inter-Handoff2012Conference paper (Refereed)
    Abstract [en]

    Opportunistic spectrum access (OSA) is a technology that allows unlicensed users to access spectrum holes and to provide so efficient use of radio resources. Most of the studies done on OSA focus on the situation when the unlicensed user performs the spectrum handoff only within a single cognitive radio network (so-called intra-handoff). In this paper, we consider the users (licensed or unlicensed) to be able to do inter-handoff among different cognitive radio cells as well. The cells provide priority to inter-handoff users. By considering multiple cells being in steady-state, the arrival rates of inter-handoff users are determined. We study the OSA performance of unlicensed users under both intra- and inter-handoff schemes, with respect to the blocking and forced-termination probabilities of unlicensed users as well as the unlicensed user service-completion and inter-handoff throughputs. Our Markov chain based numerical analysis is validated by simulation experiments.

  • 13359.
    Yao, Yong
    et al.
    Blekinge Institute of Technology, School of Computing.
    Ngoga, Said Rutabayiro
    Popescu, Adrian
    Blekinge Institute of Technology, School of Computing.
    A System for Spectrum Decision in Cognitive Radio Networks2012Conference paper (Refereed)
    Abstract [en]

    In Cognitive Radio (CR) networks, licensed radio channels are allowed to be used by Secondary Users (SUs) as long as SUs do not harmfully impair the transmission of Primary Users (PUs). Therefore, a crucial task for SUs is to decide which available channel should be selected, the so-called spectrum decision. To provide intelligent spectrum decision strategy to SUs, we suggest a system called Spectrum Decision Support System (SDSS). SDSS takes into account both heterogeneity aspects and interoperability requirements of CR networks. By this, SDSS is capable of jointly considering various channel characterizations and different decision making algorithms for doing spectrum decision. The paper is reporting the SDSS architecture as well as the related work-in-progress.

  • 13360.
    Yao, Yong
    et al.
    Blekinge Institute of Technology, School of Computing.
    Ngoga, Said Rutabayiro
    Popescu, Adrian
    Blekinge Institute of Technology, School of Computing.
    Cognitive Radio Spectrum Decision Based on Channel Usage Prediction2012Conference paper (Refereed)
    Abstract [en]

    The paper is about a new strategy suggested for spectrum decision in Cognitive Radio (CR) networks. By jointly considering sensing error, Secondary Users (SUs) competition and SUs transmission collision, a new parameter called Channel Usage State (CUS) is introduced. For a particular channel, we predict the respective probabilities of occurrence of CUS states by using the LeZi-update scheme. We also adopt a fuzzy comparison algorithm to combine the prediction results as a joint value. The largest joint value is associated with the most available channel for access by SUs in the near future. By comparing with random channel access, the suggested strategy can improve SUs transmission throughput. This is demonstrated by the simulation evaluations.

  • 13361.
    Yao, Yong
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Popescu, Adrian
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    On Energy Consumption in Mobile Multimedia Networks with OpenFlow Switch2016In: 2016 INTERNATIONAL CONFERENCE ON COMMUNICATIONS (COMM 2016), IEEE, 2016, p. 309-312Conference paper (Refereed)
    Abstract [en]

    In mobile multimedia networks, the video flow usually operates in an end-to-end manner from Head-End to mobile terminals. However, measuring the energy consumption associated with a video flow is a sophisticated process due to the complexity related to this. In the paper, a theoretical measurement approach is suggested to estimate the energy consumption of a video flow through mobile multimedia networks enhanced with the support of OpenFlow switch. Two different power models are built up to compute the traffic related energy consumption at the network element side. The numerical derivation of these two theoretical models is presented.

  • 13362.
    Yao, Yong
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Popescu, Adrian
    Blekinge Institute of Technology.
    On Energy Consumption in Mobile Multimedia Networks with OpwnFlow Switch2016In: International Conference on Communications (COMM), 2016, IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    With the advance of new wireless technologies and ubiquitous radio access, mobile multimedia is becoming a very important application for both service providers and end users. This also leads to different business models such as mobile television, mobile conferencing, and remote gaming. A Mobile Multimedia Network (MMN) generally refers to several parts, which are known as the video contribution, the network distribution and the mobile terminals. The video contribution is connected to the functions of generating and processing the video content, which is eventually transferred onto the network for further distribution to mobile terminals.

  • 13363.
    Yao, Yong
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Popescu, Adrian
    Blekinge Institute of Technology.
    Fiedler, Markus
    Blekinge Institute of Technology.
    Ljung, Rickard
    Sony Mobile Communications, SWE.
    On the Performance of Video Streaming in Energy-Aware Wireless Mesh Networks2017In: European Conference on Networks and Communications (EuCNC) 2017, IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    Mobile multimedia has today become a promising application for end users and service providers. With reference to the existing systems for mobile communications, this application further demands for solving several technical problems, especially regarding video streaming over wireless networks. An interesting approach is in form ofWireless Mesh Network (WMN) based networks, where the individual video flows operate in an end-to-end (e2e) manner along a particular networking scenario including several mesh routers. That means, a particular mesh router may be traversed by multiple video flows. This situation may become even more complicated in the case of a large amount of packet retransmissions, which may deteriorate the performance of video flows. To investigate this problem, a two-level Modulated Markov Poisson Process (MMPP) based queueing model is built up and the transport performance of e2e video streaming in WMN based mobile multimedia system is analysed. Four metrics are used to study the system performance, namely e2e throughput, e2e delay, e2e error-rate and traffic-related energy consumption. Numerical analysis and evaluation studies are done. Based on the reported results, two different solutions are suggested and discussed with regard to the trade-off among these metrics.

  • 13364.
    Yao, Yong
    et al.
    Blekinge Institute of Technology, School of Computing.
    Popescu, Alexandru
    Blekinge Institute of Technology, School of Computing.
    Ngoga, Said Rubatayiro
    Blekinge Institute of Technology, School of Computing.
    Popescu, Adrian
    Blekinge Institute of Technology, School of Computing.
    On Prioritized Spectrum Access in Cognitive Radio Networks with Imperfect Sensing2013Conference paper (Refereed)
    Abstract [en]

    Cognitive Radio networks allow the unlicensed users to share the available spectrum opportunities. However, this demands for solving the problem of contention among multiple unlicensed user packets for transmission. In our paper, we consider the Opportunistic Spectrum Access model for packet transmission between two unlicensed users. We suggest a priority scheme for a unlicensed user to concurrently transmit different types of packets. Our scheme reserves a fixed number of queueing places in the buffer for the prioritized packets. We study the transmission performance under both the priority scheme and imperfect spectrum sensing, with respect to the blocking probabilities, average transmission delay and transmission throughput of unlicensed users packets. The Markov chain based numerical analysis is validated by simulation experiments. Our results show that the suggested priority scheme is able to enhance transmission throughput of unlicensed users packets, together with significant decreased average transmission delay and minor decreased total transmission throughput.

  • 13365.
    Yao, Yong
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Popescu, Alexandru
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Popescu, Adrian
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    On Fuzzy Logic-Based Channel Selection in Cognitive Radio Networks2014In: Software-Defined and Cognitive Radio Technologies for Dynamic Spectrum Management / [ed] Kaabouch, Naima; Hu, Wen-Chen, Hershey, PA 17033, USA: IGI-Global , 2014Chapter in book (Refereed)
    Abstract [en]

    Cognitive radio networks are a new technology based on which unlicensed users are allowed access to licensed spectrum under the condition that the interference perceived by licensed users is minimal. That means unlicensed users need to learn from environmental changes and to take appropriate decisions regarding the access to the radio channel. This is a process that can be done by unlicensed users in a cooperative or non-cooperative way. Whereas the non-cooperative algorithms are risky with regard to performance, the cooperative algorithms have the capability to provide better performance. Our paper reports therefore a new fuzzy logic based decision making algorithm for channel selection. The underlying decision criterion considers statistics of licensed users channel occupancy as well as information about the competition level of unlicensed users. Our theoretical studies indicate that the unlicensed users can obtain an efficient sharing of the available channels. Simulation results are reported to demonstrate the performance and effectiveness of the suggested algorithm.

  • 13366.
    Yao, Yong
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Popescu, Alexandru
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Popescu, Adrian
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    On prioritised opportunistic spectrum access in cognitive radio cellular networks2015In: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 27, no 2, p. 294-310Article in journal (Refereed)
    Abstract [en]

    Cognitive radio (CR) networks allow secondary users (SUs) to opportunistically access licensed spectrum, thus providing efficient use of radio resources. Different studies carried out on CR networks have focused on the procedure of spectrum handoff of SUs such as the data transmission in a communication that can be carried out in different channels. In this paper, we consider cellular networks enhanced with facilities for CR communication where a user with a call in progress moves across neighbouring cells, that is, the so-called inter-cell handoff. Our model assumes that the cell gives priority to inter-cell handoff calls over the calls originating within it. A finite queue is used in every cell for SUs, and a fixed number of buffer slots are reserved for the inter-handoff SU calls. With these considerations, we study the transmission performance of SUs by using Markov chains-based modelling approach. The numerical analysis is validated by simulation experiments. We also suggest a fuzzy logic-based hybrid decision-making algorithm to select the best solution for inter-handoff prioritisation. The goal is to optimise the transmission performance of SUs by leveraging their requirements on service completion throughput and waiting time in each cell. Copyright © 2014 John Wiley & Sons, Ltd.

  • 13367.
    Yarragudi, Jeevan Reddy
    Blekinge Institute of Technology, School of Engineering.
    Adaptive Speech enhancement system using Linear Microphone-array for noise Reduction2012Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    A major part of the interaction between humans takes place via speech communication. It is very difficult to understand speech signals in presence of background noise for the normal listeners and hearing impaired persons. The human speech and hearing organ is inherently sensitive to interfering noise. Interfering noise decreases speech intelligibility and quality. Speech enhancement algorithms reduces the noise and improve one or more perceptual aspects of noisy speech most notably quality and intelligibility. The main objective of speech enhancement is to reduce the influence of the noise. Speech communication is processing through Tele-conferencing, audio conferencing and video conferencing, these are influenced in indoors, office environments and closed auditoriums i.e. communication between one person to another person. These communication systems will become disturbing by some unknown noises like random noises, some mobile ring disturbances and fan noises in computers. The quality of speech is reduced in indoors due to the propagation channel (medium) and additional noise sources. According to these disturbances the quality of original speech is de-graded in conservations, so it’s need to enhance the speech from the noisy environment. In this thesis work, first proposing appropriate microphone array setup with improved speech processing technique, and implementing the generalized side lobe canceller (GSC) beam forming techniques by using required adaptive algorithm (LMS). In order to get better speech quality using the Microphone arrays. Microphone arrays have been widely used to improve the performance of speech recognition systems as well as to benefit for people who need having aids. With the help of microphone arrays, it can choose to focus on signals from a specific direction. To getting better speech quality in microphone array using adaptive algorithms, these are help in the noise suppression in accordance with the different beam forming techniques. The proposed system is implemented and evaluated using MATLAB simulation tool. The objective quality measures is Signal to Noise Ratio Improvement (SNRI), is using to validate the system. The systems were tested with a pure speech combination of male and female sampled at16 KHz, one interference noise is the male voice sampled at 16KHz and one random noises are simulated at different positions of speech and noise sources with different input SNR ratios of 0dB, 5dB, 10dB, 15dB, 20dB and 25dB. The overall signal to noise ratio improvement is determined from the main speech and two noise inputs and output powers. The SNR improvement at wiener beam former system is around 20dB and the SNR improvement at GSC system is around 26dB.

  • 13368.
    Yarrapothu, Sindhura
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Effectiveness of Backup and Disaster Recovery in Cloud: A Comparative study on Tape and Cloud based Backup and Disaster Recovery2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Context: Backup and Disaster Recovery, DR play a vital role in day-to-day IT operations. They define extensive aspects of business continuity plan in an enterprise. There is a continuous need to improve backup and recovery performance concerning attributes such as backup window size, high availability, security, etc. Definitive information is what enterprises strive for and rely upon to deviate from traditional methods towards advancing technologies, which are an intrinsic segment of business mundane actions.

    Objectives: In this study, we investigate Backup and DR plans on an enterprise level. They are compared in terms of performance metrics such as Recovery Time Objective, Recovery Point Objective, Time taken to backup, Time taken to recover and Total cost of ownership. Also, how CPU and memory utilization conduct differ in both tape-based, cloud-based Backup and DR.

    Methods: Literature study was the first step to formulate research questions by understanding present technologies in Backup and DR. This led us to conduct a survey for further understanding of challenges faced in industries gaining a more practical exposure. A case study was conducted in an enterprise to capture accurate values. An experiment had been deployed to compare performance of both scenarios and analyze which methodology elevates Backup and DR performance by overcoming challenges.

    Results: The results attained through this thesis encompass performance related metrics and also the load in terms of CPU and memory utilizations. Survey results were observed to gain better understanding of current technologies and challenges with Backup and DR in enterprises. The cloudbased backup has proved to be better in considered enterprise environment during experimentation in terms of RPO, RTO, CPU, memory utilizations and Total Cost of ownership.

    Conclusions: There have been numerous research works conducted on how backup and DR plans can be made better. But, they lack accurate information on how their performances vary, what all parameters can be improved by shifting towards advanced and contemporary methodologies withaddressing features such as scalability, flexibility and adaptability, which is provided in this study.

  • 13369.
    Yasam, Venkata Sudheer Kumar Reddy
    Blekinge Institute of Technology, School of Computing.
    An Optimized Representation for Dynamic k-ary Cardinal Trees2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Trees are one of the most fundamental structures in computer science. Standard pointer-based representations consume a significant amount of space while only supporting a small set of navigational operations. Succinct data structures have been developed to overcome these difficulties. A succinct data structure for an object from a given class of objects occupies space close to the information-theoretic lower-bound for representing an object from the class, while supporting the required operations on the object efficiently. In this thesis we consider representing trees succinctly. Various succinct representations have been designed for representing different classes of trees, namely, ordinal trees, cardinal trees and labelled trees. Barring a few, most of these representations are static in that they do not support inserting and deleting nodes. We consider succinct representations for cardinal trees that also support updates (insertions and deletions), i.e., dynamic cardinal trees. A cardinal tree of degree k, also referred to as a k-ary cardinal tree or simply a k-ary tree is a tree where each node has place for up to k children with labels from 1 to k. The information-theoretic lower bound for representing a k-ary cardinal tree on n nodes is roughly (2n+n log k) bits. Representations that take (2n+n log k+ o(n log k ) ) bits have been designed that support basic navigations operations like finding the parent, i-th child, child-labeled j, size of a subtree etc. in constant time. But these could not support updates efficiently. The only known succinct dynamic representation was given by Diego, who gave a structure that still uses (2n+n log k+o(n log k ) ) bits and supports basic navigational operations in O((log k+log log n) ) time, and updates in O((log k + log log n)(1+log k /log (log k + log log n))) amortized time. We improve the times for the operations without increasing the space complexity, for the case when k is reasonably small compared to n. In particular, when k=(O(√(log n ))) our representation supports all the navigational operations in constant time while supporting updates in O(√(log log n )) amortized time.

  • 13370.
    Yasar, Fatma Gunseli
    et al.
    Izmir Katip Celebi Universitesi, TUR.
    Kusetogullari, Hüseyin
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Underwater human body detection using computer vision algorithms2018In: 26th IEEE Signal Processing and Communications Applications Conference, SIU 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 1-4Conference paper (Refereed)
    Abstract [en]

    The number of studies to ensure the security when life-threatening unexpected events are encountered increases. Increasing of time spent under the water can cause the death of people. Thus, people who are in a risk of suffocation in the water must be found for early intervention and this process must be quick. The main contribution of this study is to detect and to track the people under the water quickly. Thresholding, Background Subtraction, Interframe Difference and Foreground Detection methods have been applied to create the silhouette of the people under the water. These methods have been demonstrated on videos which are found from internet. © 2018 IEEE.

  • 13371.
    Yasin, Affan
    et al.
    Blekinge Institute of Technology, School of Computing.
    Hasnain, Muhammad Ijlal
    Blekinge Institute of Technology, School of Computing.
    On the Quality of Grey Literature and its use in Information Synthesis during Systematic Literature Reviews2012Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Context: The Internet has become a vital channel for disseminating and accessing scientific literature for both the academic and industrial research needs. Nowadays, everyone has wide access to scientific literature repositories, which comprise of both “white” and “Grey” literature. The “Grey” literature, as opposed to “white” literature, is non-peer reviewed scientific information that is not available using commercial information sources such as IEEE or ACM. A large number of software engineering researchers are undertaking systematic literature reviews (SLRs) to investigate empirical evidence in software engineering. The key reason to include grey literature during information synthesis is to minimize the risk of any bias in the publication. Using the state of the art non-commercial databases that index information, the researchers can make the rigorous process of searching empirical studies in SLRs easier. This study explains the evidence of Grey literature while performing synthesis in Systematic Literature Reviews. Objectives: The goals of this thesis work are, 1. To identify the extent of usage of Grey Literature in synthesis during systematic literature reviews. 2. To investigate if non-commercial information sources primarily Google Scholar are sufficient for retrieving primary studies for SLRs. Methods: The work consists of a systematic literature review of SLRs and is a tertiary study and meta-analysis. The systematic literature review was conducted on 138 SLRs’ published through 2003 until 2012 (June). The article sources used are IEEEXplore, ACM Digital Library, Springer-Link and Science Direct. Results: For each of the selected article sources such as ACM, IEEEXplore, Springer-link and Science Direct, we have presented results, which describe the extent of the usage of Grey literature. The qualitative results discuss various strategies for systematic evaluation of the Grey literature during systematic literature review. The quantitative results comprise of charts and tables, showing the extent of Grey literature usage. The results from analysis of Google Scholar database describe the total number of primary studies that we are able to find using only Google Scholar database. Conclusion: From the analysis of 138 Systematic Literature Reviews (SLRs’), we conclude that the evidence of Grey literature in SLRs is around 9%. The percentage of Grey literature sources used in information synthesis sections of SLRs is around 93.2%. We were able to retrieve around 96 % of primary studies using Google Scholar database. We conclude that Google Scholar can be a choice for retrieving published studies however; it lacks detailed search options to target wider pool of articles. We also conclude that Grey literature is widely available in this age of information. We have provided guidelines in the form of strategies for systematic evaluation of Grey literature.

  • 13372.
    Yasir, Mukhtar Muhammad
    et al.
    Blekinge Institute of Technology, School of Engineering.
    Kamal, Badar Munir
    Blekinge Institute of Technology, School of Engineering.
    Issues In WiMax Handover2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    WiMax, the Worldwide Interoperability for Microwave Access is a new technology dealing with provision of data over long distance using wireless communication method in many different ways. Based on IEEE 802.16 WiMax is claimed as an alternative broadband rather than cable and DSL. In our thesis study we will findout the phenomenon and factors involved in WiMax handover and their effect on overall quality of service. We also intend to look into the solutions possible for those problems effecting WiMax QoS in handover. Handover is the main theme of wireless technolgy and it makes interoperability between diffrent network technologies and provides mobility. However there are some problems during handover and the problem in our focus will be handover delay. Handover delay if longer than expected makes the communication faulty and introduces errors and packet loss which in turns degrade QoS in WiMax

  • 13373. Yatawara, Yeshan
    et al.
    Caldera, Manora
    Kusuma, Tubagus Maulana
    Zepernick, Hans-Jürgen
    Unequal Error Protection for ROI Coded Images over Fading Channels2005Conference paper (Refereed)
    Abstract [en]

    Region of interest (ROI) coding is a feature supported by the Joint Photographic Experts Group 2000 (JPEG2000) image compression standard and allows particular regions of interest within an image to be compressed at a higher quality than the rest of the image. In this paper, unequal error protection (UEP) is proposed for ROI coded JPEG2000 images as a technique for providing increased resilience against the effects of transmission errors over a wireless communications channel. The hierarchical nature of an ROI coded JPEG2000 code-stream lends itself to the use of UEP whereby the important bits of the code-stream are protected with a strong code while the less important bits are protected with a weaker code. Simulation results obtained using symbol-by-symbol maximum a posteriori probability (MAP) decoding demonstrate that the use of UEP offers significant gains in terms of the peak signal to noise ratio (PSNR) and the percentage of readable files. Moreover, the use of ROI-based UEP leads to reduced computational complexity at the receiver.

  • 13374.
    Yates, Andrew
    et al.
    Max Planck Institut für Informatik, DEU.
    Unterkalmsteiner, Michael
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Replicating relevance-ranked synonym discovery in a new language and domain2019In: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), Springer Verlag , 2019, Vol. 11437, p. 429-442Conference paper (Refereed)
    Abstract [en]

    Domain-specific synonyms occur in many specialized search tasks, such as when searching medical documents, legal documents, and software engineering artifacts. We replicate prior work on ranking domain-specific synonyms in the consumer health domain by applying the approach to a new language and domain: identifying Swedish language synonyms in the building construction domain. We chose this setting because identifying synonyms in this domain is helpful for downstream systems, where different users may query for documents (e.g., engineering requirements) using different terminology. We consider two new features inspired by the change in language and methodological advances since the prior work’s publication. An evaluation using data from the building construction domain supports the finding from the prior work that synonym discovery is best approached as a learning to rank task in which a human editor views ranked synonym candidates in order to construct a domain-specific thesaurus. We additionally find that FastText embeddings alone provide a strong baseline, though they do not perform as well as the strongest learning to rank method. Finally, we analyze the performance of individual features and the differences in the domains. © Springer Nature Switzerland AG 2019.

  • 13375.
    Yavariabdi, Amir
    et al.
    Karatay Üniversitesi, TUR.
    Kusetogullari, Hüseyin
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Mendi, Engin
    Karatay Üniversitesi, TUR.
    Karabatak, Begum
    Turkcell, Nicosia, CYP.
    Unsupervised Change Detection using Thin Cloud-Contaminated Landsat Images2018In: 9th International Conference on Intelligent Systems 2018: Theory, Research and Innovation in Applications, IS 2018 - Proceedings / [ed] JardimGoncalves, R; Mendonca, JP; Jotsov, V; Marques, M; Martins, J; Bierwolf, R, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 21-25Conference paper (Refereed)
    Abstract [en]

    In this paper, a novel unsupervised change detection method is proposed to automatically detect changes between two cloud-contaminated Landsat images. To achieve this, firstly, a photometric invariants technique with Stationary Wavelet Transform (SWT) are applied to input images to decrease the influence of cloud and noise artifacts in the change detection process. Then, mean shift image filtering is employed on the sub-band difference images, generated via image differencing technique, to smooth the images. Next, multiple binary change detection masks are obtained by partitioning the pixels in each of the smoothed sub-band difference images into two clusters using Fuzzy c-means (FCM). Finally, the binary masks are fused using Markov Random Field (MRF) to generate the final solution. Experiments on both semi-simulated and real data sets show the effectiveness and robustness of the proposed change detection method in noisy and cloud-contaminated Landsat images. © 2018 IEEE.

  • 13376.
    YAW, FRANCIS OWUSU
    Blekinge Institute of Technology, School of Management.
    HEALTH DELIVERY SERVICE IN GHANA: CONSUMER PROTECTION AND SATISFACTION - Performance Assessment at the Komfo Anokye Teaching Hospital - Kumasi2007Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    ABSTRACT Almost every patient in Ghana has a story to tell about the health care delivery system, some pleasant and others bitter. This calls for a system of continuous quality improvement for the improvement of the health and functioning of the people . The research sort answers to the following questions: What level of quality care are patients receiving now that health care is very accessible? Are Ghanaian consumers satisfied with the services of the health sector? What is the level of awareness of Ghanaian patients of the Patients Charter promulgated to protect them? Are there any correlation between the level of patients’ satisfaction and their level of awareness of consumer/patients protection laws? The research revealed that: o doctors and nurses at the Hospital generally treat Patients with Respect and Courtesy o both doctors and nurses at the hospital do not take time to explain to patients the side-effects of medicines prescribed. o responsiveness of Hospital Staff to Patients call for help is not encouraging o Hospital staff do not provide adequate information to Patients when they are being discharged o the hospital staff keep their environment clean. o most patients of the hospital do not know that patients have rights protected by law. o the general perception of patients about the hospital was above average performance. On the satisfaction index scale they scored MnCSI – 77. However, it was also revealed that the satisfaction level of patients has correlation with their level of knowledge of patients rights It was found out that if all patients will know and insist on their rights, quality will improve at our hospitals.

  • 13377.
    Yazdani, Tulha Moaiz
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Islam, Munawar
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Design And Fabrication Of A Microstrip Antenna For WI-MAX Applications2008Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Worldwide Interoperability for Microwave Access (Wi-Max) is a broadband technology enabling the delivery of last mile (final leg of delivering connectivity from a communication provider to customer) wireless broadband access (alternative to cable and DSL). It should be easy to deploy and cheaper to user compared to other technologies. Wi-Max could potentially erase the suburban and rural blackout areas with no broadband Internet access by using an antenna with high gain and reasonable bandwidth Microstrip patch antennas are very popular among Local Area Network (LAN), Metropolitan Area Network (MAN), Wide Area Network (WAN) technologies due to their advantages such as light weight, low volume, low cost, compatibility with integrated circuits and easy to install on rigid surface. The aim is to design and fabricate a Microstrip antenna operating at 3.5GHz to achieve maximum bandwidth for Wi-Max applications. The transmission line model is used for analysis. S-parameters (S11 and S21) are measured for the fabricated Microstrip antenna using network analyzer in a lab environment. The fabricated single patch antenna brings out greater bandwidth than conventional high frequency patch antenna. The developed antenna also is found to have reasonable gain.

  • 13378.
    YE, JIENAN
    Blekinge Institute of Technology, School of Technoculture, Humanities and Planning.
    RESEARCH OF LANDSCAPE DESIGN IN RESIDENTIAL AREA2009Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    The environment of residential area has a closed relationship with human’s living. It is not only a significant place of human activities, but also an important constituent in urban environment. Along with the development of society and economy, the residential landscape is also changing. However, in the course of development, many problems have appeared. These issues have had negative effect on the quality of landscape and seriously hindered the development of residential landscape design for the future. In this thesis, residential landscape was selected as the research subject. Through the systematically organized survey and discussion of the case analysis, I was hoping to put forward some effective solutions for the existing problems and future planning. The thesis included 6 parts. Part 1 was introduction, including research background, contents and methods. Part 2 and 3 were the theoretical basis of the paper. Relational concepts and theories were presented. The Garden City theory, Neighborhood theory and the theory of organism decentralization,which had a direct role in the planning of my case studies, were fully described. In addition, based on the information from literature, the classification for landscape was made, which was also the foundation of the analyzed cases. Next three parts of the thesis were the emphasis of the thesis. Three cases, two from China and one from Sweden were selected, analyzed and discussed in which both the advantages and disadvantages of design were mentioned. By means of these studies, we could get some inspiration about residential landscape and try to avoid the redundant mistakes in future. Finally, some planning approaches and principles had come up for modern residential landscape from this study.

  • 13379.
    Yellakonda, Amulya
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    DESIGN AND IMPLEMENTATION OF RICH COMMUNICATION SERVICE SCENARIO REPLAYER AND PERFORMANCE EVALUATION OF APPLICATION SERVICE2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Rich Communication Services(RCS) program is a GSM Association (GSMA) initiative to create inter-operator communication services based on IP Multimedia Subsystem (IMS) . This initiative came up as the Global Telecom Operators ́response to the decline in their revenues and to help compete ’Over The Top’(OTT) service providers such as Viber, whatsapp, etc. RCS is an universal standard, making it inter-operable between mul- tiple service providers unlike OTT services with closed communities. RCS services use IMS as the underlying architecture with a RCS stack imple- mented into Android background service which offers high level API. For the purpose of testing RCS stack functionality which is usually affected by external dependencies like third party vendors, or ISP customizations in real telecommunication scenario, there is a persistent demand for scenario replay tools that can recreate the range of test conditions similar to those experienced in live deployments. There is also a need to evaluate the per- formance of service provided by application servers in the network in-order to predict the factors affecting the RCS service in general.

    In this work, we propose a tool to address the RCS scenario repro- duction in a test environment. The tool is implemented within an automated test environment with full control on interaction with the RCS stack, hence the ability to replay the scenario in a controlled fashion. To achieve the goal, the tool replays trace interactively with the RCS stack in a stateful manner , it ensures no improper packet generation which is critical feature for test environments where protocol semantics accuracy is fundamental. A detailed demonstration of how the tool can be deployed in test environ- ments is stated. A novel approach is used to validate the effectiveness of the replayed scenario, the sequence of events and states are compared to those from the recorded scenario using a call-back service to indicate the state. The replayed scenario showed strong relationship with the recorded RCS scenario. The paper also presents a performance evaluation of Application service by considering the request-reponse times of Network Registration procedure. The obtained results show that the average time taken for the Registration process is 555 milliseconds and in few instances there exists larger deviations from this average value showing the faulty behavior of the Server which is most crucial during the debugging process for the developers. 

  • 13380.
    Yelleswarapu, Mahesh Chandra
    Blekinge Institute of Technology, School of Computing.
    An Assessment of the Usability Quality Attribute in Open Source Software2010Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Usability is one of the important quality attributes. Open source software products are well known for their efficiency and effectiveness. Lack of usability in OSS (Open Source Software) products will result in poor usage of the product. In OSS development there is no usability team, and one could therefore expect that the usability would be low for these products. In order to find out if this was really the case we made a usability evaluation using a questionnaire for four OSS products. The questionnaire was based on a review of existing literature. This questionnaire was presented to 17 people who are working with open source products. This evaluation showed that the overall usability was above average for all the four products. It seems, however, that the lack of a usability team has made the OSS products less easy to use for inexperienced users. Based on the responses to questionnaire and a literature review, a set of guidelines and hints for increasing the usability of OSS products was defined.

  • 13381. Yeoh, Phee
    et al.
    Elkashlan, Maged
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Yang, Nan
    Da Costa, Daniel
    Transmit antenna selection in cognitive relay networks with Nakagami-m fading2013Conference paper (Refereed)
    Abstract [en]

    We examine the impact of multiple primary receivers on cognitive multiple-input multiple-output (MIMO) relay networks with underlay spectrum sharing. For such a network, we propose transmit antenna selection with receive maximal-ratio combining (TAS/MRC) as an interference-aware design to satisfy the power constraints in the primary and secondary networks. To demonstrate this, we derive new closed-form expressions for the exact and asymptotic outage probability with TAS/MRC and decode-and-forward (DF) relaying over independent Nakagami-m fading channels in the primary and secondary networks. Several important design insights are reached. We find that the TAS/MRC strategy achieves a full diversity gain when the transmit power in the secondary network is proportional to the peak interference power in the primary network. Furthermore, we highlight that the diversity-multiplexing tradeoff (DMT) of TAS/MRC is independent of the primary network and entirely dependent on the secondary network.

  • 13382. Yeoh, Phee
    et al.
    Elkashlan, Maged
    Yang, Nan
    Benevides Da Costa, Daniel
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    MIMO multi-relay networks with TAS/MRC and TAS/SC in Weibull fading channels2012Conference paper (Refereed)
    Abstract [en]

    We examine transmit antenna selection with receiver maximal-ratio combining (TAS/MRC) and transmit antenna selection with receiver selection combining (TAS/SC) in multiple-input multiple-output (MIMO) relay networks. Amongst L two-hop relay links, a single relay offering the highest end-to-end signal-to-noise ratio (SNR) is activated. Assuming independent non-identically distributed Weibull fading between the hops, new closed-form asymptotic expressions for the outage probability and the symbol error rate are derived considering NS, NR, and ND antennas at the source, the relays, and the destination, respectively. Based on such expressions, the diversity order and the array gain for M-ary phase shift keying and M-ary quadrature amplitude modulation are analyzed. We highlight that the diversity order of TAS/MRC is the same as TAS/SC. As such, we explicitly characterize the SNR gap between TAS/MRC and TAS/SC as the ratio of their respective array gains. An interesting observation is reached that for equal per-hop SNRs, the SNR gap between the two protocols is independent of L.

  • 13383. Yeoh, Phee Lep
    et al.
    Elkashlan, Maged
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Yang, Nan
    Leung, Cyril
    Cognitive MIMO relaying in Nakagami-m fading2013Conference paper (Refereed)
    Abstract [en]

    We propose transmit antenna selection with receive maximal-ratio combining (TAS/MRC) as an effective approach to reduce interference in cognitive multiple-input multiple-output (MIMO) relay networks. To demonstrate this, we derive new closed-form expressions for the exact and asymptotic outage probability of TAS/MRC with multiple antennas at the primary and secondary users. We consider underlay spectrum sharing where the secondary users (SUs) transmit in the presence of multiple primary users (PUs). We consider independent Nakagami-m fading in both the primary and secondary networks. Several important design insights are revealed. We find that TAS/MRC achieves a full diversity when the transmit power at the SUs is proportional to the peak interference power at the PUs. Furthermore, we highlight that this diversity gain is completely independent of the number of antennas at the PUs.

  • 13384. Yeoh, Phee Lep
    et al.
    Elkashlan, Maged
    Duong, Trung Q.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Yang, Nan
    da Costa, Daniel Benevides
    Transmit Antenna Selection for Interference Management in Cognitive Relay Networks2014In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 63, no 7, p. 3250-3262Article in journal (Refereed)
    Abstract [en]

    We propose transmit antenna selection (TAS) in decode-and-forward (DF) relaying as an effective approach to reduce the interference in underlay spectrum sharing networks with multiple primary users (PUs) and multiple antennas at the secondary users (SUs). We compare two distinct protocols: 1) TAS with receiver maximal-ratio combining (TAS/MRC) and 2) TAS with receiver selection combining (TAS/SC). For each protocol, we derive new closed-form expressions for the exact and asymptotic outage probability with independent Nakagami-m fading in the primary and secondary networks. Our results are valid for two scenarios related to the maximum SU transmit power, i.e., P, and the peak PU interference temperature, i.e., Q. When P is proportional to Q, our results confirm that TAS/MRC and TAS/SC relaying achieve the same full diversity gain. As such, the signal-to-noise ratio (SNR) advantage of TAS/MRC relaying relative to TAS/SC relaying is characterized as a simple ratio of their respective SNR gains. When P is independent of Q, we find that an outage floor is obtained in the large P regime where the SU transmit power is constrained by a fixed value of Q. This outage floor is accurately characterized by our exact and asymptotic results.

  • 13385. Yeoh, Phee Lep
    et al.
    Elkashlan, Maged
    Kim, Kyeong Jin
    Duong, Trung Quang
    Blekinge Institute of Technology, School of Computing.
    Karagiannidis, George K.
    Cognitive MIMO Relaying with Multiple Primary Transceivers2013In: 2013 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), 2013, p. 1956-1961Conference paper (Refereed)
    Abstract [en]

    We examine the impact of clusters of primary transceivers in cognitive multiple-input multiple-output (MIMO) relay networks with underlay spectrum sharing. In such a network, we propose antenna selection as an interference-aware design to satisfy the power constraints in the primary and secondary networks. To demonstrate this, we consider transmit antenna selection with maximal ratio combining (TAS/MRC) in the primary and secondary networks. With this in mind, we derive new closed-form asymptotic expressions for the outage probability and the symbol error rate (SER) over independent Nakagami-m fading channels. Our results lead to several new fundamental insights. In particular, we highlight that TAS/MRC achieves a full diversity gain when the maximum transmit power in the secondary network is proportional to the peak interference temperature in the primary network.

  • 13386. Yeoh, Phee Lep
    et al.
    Elkashlan, Maged
    Yang, Nan
    da Costa, Daniel B.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Unified Analysis of Transmit Antenna Selection in MIMO Multi-Relay Networks2013In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 62, no 2Article in journal (Refereed)
    Abstract [en]

    We present a unified asymptotic framework for transmit antenna selection in multiple-input multiple-output (MIMO) multi-relay networks with Rician, Nakagami-m, Weibull, and Generalized-K fading channels. We apply this framework to derive new closed-form expressions for the outage probability and symbol error rate (SER) of amplify-andforward relaying in MIMO multi-relay networks with two distinct protocols: 1) transmit antenna selection with receiver maximalratio combining (TAS/MRC), and 2) transmit antenna selection with receiver selection combining (TAS/SC). Based on these expressions, the diversity order and the array gain with M-ary phase shift keying and M-ary quadrature amplitude modulation are derived.We corroborate that the diversity order only depends on the fading distribution and the number of diversity branches, whereas the array gain depends on the fading distribution, the modulation format, the number of diversity branches, and the average per-hop signal-to-noise ratios (SNRs). We highlight that the diversity order of TAS/MRC is the same as TAS/SC, regardless of the underlying fading distribution. As such, we explicitly characterize the SNR gap between TAS/MRC and TAS/SC as the ratio of their respective array gains. An interesting observation is reached that for equal per-hop SNRs, the SNR gap between the two protocols is independent of the number of relays.

  • 13387. Yeoh, Phee Lep
    et al.
    Elkashlan, Maged
    Yang, Nan
    da Costa, Daniel
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Unified Analysis of Transmit Antenna Selection in MIMO Multirelay Networks2013In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 62, no 2, p. 933-939Article in journal (Refereed)
    Abstract [en]

    We present a unified asymptotic framework for transmit antenna selection in multiple-input multiple-output (MIMO) multirelay networks with Rician, Nakagami-m, Weibull, and generalized-K fading channels. We apply this framework to derive new closed-form expressions for the outage probability and symbol error rate (SER) of amplify-and-forward (AF) relaying in MIMO multirelay networks with two distinct protocols: 1) transmit antenna selection with receiver maximal-ratio combining (TAS/MRC) and 2) transmit antenna selection with receiver selection combining (TAS/SC). Based on these expressions, the diversity order and the array gain with M-ary phase-shift keying and M-ary quadrature-amplitude modulation are derived. We corroborate that the diversity order only depends on the fading distribution and the number of diversity branches, whereas the array gain depends on the fading distribution, the modulation format, the number of diversity branches, and the average per-hop signal-to-noise ratios (SNRs). We highlight that the diversity order of TAS/MRC is the same as TAS/SC, regardless of the underlying fading distribution. As such, we explicitly characterize the SNR gap between TAS/MRC and TAS/SC as the ratio of their respective array gains. An interesting observation is reached that for equal per-hop SNRs, the SNR gap between the two protocols is independent of the number of relays.

  • 13388. Yermeche, Zohra
    Soft-Constrained Subband Beamforming for Speech Enhancement2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    New speech acquisition applications are emerging as a result of advances in technology and the prevalence of mobile communication. While today voice control of consumer equipment is becoming a reality, communication technology has extended voice connectivity to personal computers and mobile communication devices with the aim of enabling natural communication in a variety of environments such as cars, restaurants and offices. The comfort and flexibility provided through the hands-free acquisition of speech in mobile telephony, speech recognition and hearing aids require robust techniques to deal with problems of environmental noise, reverberation, acoustic feedback and other interfering sounds which corrupt the received speech. For mobile environments, speech enhancement techniques should also provide an adaptation capacity to speaker motion with no perceptible degradations of the original speech. In this thesis, multi-microphone techniques for speech enhancement are developed. First, a framework for constrained beamforming is introduced. This framework allows us to control the tradeoff relationship between noise reduction, dereverberation and speech degradation. A constraint on the power minimization of the beamformer’s output is formulated to guarantee the integrity of the desired signal. It is shown that the robustness towards microphone mismatch of the soft-constrained beamforming structure is guaranteed by modeling the source as spatially spread. A subband recursive least-squares (RLS) beamformer is investigated and evaluated in real handsfree acoustical environments. The proposed methodology is defined to perform background noise and interference reduction, while a soft constraint built from calibration data in low noise conditions guarantees the undistorted filtering of the desired signal. This adaptive structure allows for a tracking of the noise characteristics, so as to efficiently accomplish its attenuation. A subband beamforming structure is used to improve the performance of the system and reduce the computational complexity. A real-time DSP implementation is described and evaluated for dual microphone speech enhancement. Furthermore, a novel blind soft-constrained beamforming approach for moving source speech enhancement is presented. It is based on a soft constraint defined for a delay-spread corresponding to a volume around the speech source location. A new speech-oriented time-delay estimation algorithm is combined with the beamformer to allow for speaker movement. The proposed method does not require any calibration data, knowledge of the array manifold or any other characteristics of the acoustical environment. Hence, it provides means to blindly enhance a dominant speaker in adverse noise conditions. This structure is further developed to allow for the detection and enhancement of multiple dominant speakers in a mixture of interferences and background noise. The use of a frequency-dependent constraint region opens the path for a trade-off between noise suppression and speech integrity.

  • 13389. Yermeche, Zohra
    Subband Beamforming for Speech Enhancement in Hands-Free Communication2004Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Speech enhancement by means of microphone array signal processing has a major role in voice communication applications such as audio-conferencing, hands-free telephony, voice recognition and hearing aids. In these communication scenarios, the speaker is positioned at a remote distance from the microphones, which causes problems of environment noise and interfering sound corrupting the received speech. Additionally, reverberations of the voice from walls or ceilings, also impairs the received speech signal. In the case of a duplex communication, the acoustic feedback constitutes another disturbance for the talker who hears his or her voice echoed. Successful speech enhancement solutions should achieve speech dereverberation, efficient noise and interference reduction, and for mobile environments, they should also provide an adaptation capacity to speaker motion. Microphone arrays spatially sample the sound pressure field. When combined with spatio-temporal filtering techniques known as {\em beamforming}, they can extract the sound source information from signals, of which only a mixture is observed. This is based on the inherent ability of sensor arrays to exploit the spatial correlation of multiple received signals. A subband beamforming structure can be used in order to improve the performance of the time-domain filters and reduce their computational complexity. Each of the received signals is decomposed into a set of narrow-band signals and the filtering operations of the beamformer are performed for each frequency band separately. The output of the subband beamformers are then used to reconstruct a full-band output signal. In this thesis an adaptive subband RLS beamforming approach is investigated and evaluated in real hands-free acoustical environments. The proposed methodology is defined such to perform background noise and acoustic coupling reduction, while producing an undistorted filtered version of the signal originating from a desired location. The beamformer recursively minimizes a Least Squares error based on the continuously received data. This adaptive structure allows for a tracking of the noise characteristics, such to accomplish its attenuation in an efficient manner. A soft constraint built from calibration data in low noise conditions guarantee the integrity of the desired signal without the need of any speech detection. Additionally, a new spatial filter bank design method for beamforming applications, which includes the constraint of signal passage at one position and closing in other undesired positions, is suggested. Furthermore, to allow for source mobility tracking, a soft constrained beamforming approach with built-in speaker localization, is proposed. The source of interest is modelled as a cluster of point sources and source motion is accommodated by revising the point source cluster. Real speech signals are used in the simulations and results show accurate speaker movement tractability with maintained noise and interference suppression of about 10-15 dB, when using a four-microphone array.

  • 13390. Yermeche, Zohra
    et al.
    Cornelius, Per
    Grbic, Nedelko
    Claesson, Ingvar
    Spatial Filter Bank Design for Speech Enhancement Beamforming Applications2004Conference paper (Refereed)
    Abstract [en]

    In this paper, a new spatial filter bank design method for speech enhancement beamforming applications is presented. The aim of this design is to construct a set of different filter banks that would include the constraint of signal passage at one position (and closing in other positions corresponding to known disturbing sources). By performing the directional opening towards the desired location in the fixed filter bank structure, the beamformer is left with the task of tracking and suppressing the continuously emerging noise sources. This algorithm has been implemented in MATLAB and tested on real speech recordings conducted in a car hands-free communication situation. Results show that a reduction of the total complexity can be achieved while maintaining the noise suppression performance and reducing the speech distortion.

  • 13391. Yermeche, Zohra
    et al.
    Garcia, Pilar Márquez
    Grbic, Nedelko
    Claesson, Ingvar
    A Calibrated Subband Beamforming Algorithm for Speech Enhancement2002Conference paper (Refereed)
    Abstract [en]

    This paper proposes a new calibrated adaptive frequency domain beamformer for speech enhancement. The beamformer is based on the principle of a soft constraint formed from calibration data, rather than precalculated from free-field assumptions. The benefit is that the real room acoustical properties will be taken into account. The proposed algorithm continuously estimates the spatial information for each frequency band, based on weighting of the received data. The update of the beamforming weights is done recursively where the initial precalculated correlation estimates of the speech constitute a soft constraint. The soft constraint secures the spatial-temporal passage of the desired source signal, without the need of any speech detection. The performance is evaluated in real world scenarios, both in a car-and a restaurant- environment. Interference and noise sup-pression of more than 15 dB is accomplished, while very small distortion is measured for the source signal.

  • 13392. Yermeche, Zohra
    et al.
    Grbic, Nedelko
    A Delay-Based Constrained Beamformer for Blind Speech Enhancement and Dereverberation2007Conference paper (Refereed)
    Abstract [en]

    This paper presents a new microphone array method to enhance speech signals in a noisy reverberant environment. A time-delay estimation method is used for the speech source localization. The robustness of the localization method in high noise levels is provided by a subband Kurtosis-weighted structure. The estimated inter-sensor time-delays are directly used in an adaptive soft-constrained subband beamformer. Evaluation in a simulated environment with real speech sequences shows promising results.

  • 13393. Yermeche, Zohra
    et al.
    Grbic, Nedelko
    Claesson, Ingvar
    Beamforming for Moving Source Speech Enhancement2005Conference paper (Refereed)
    Abstract [en]

    This paper presents a new constrained subband beamforming algorithm to enhance speech signals generated by a moving source in a noisy environment. The beamformer is based on the principle of a soft constraint defined for a specified region corresponding to a known source location. The soft constraint secures the spatial-temporal passage of the desired source signal in the adaptive update of the beamforming weights and guarantees the full rank property of the matrix inverted in the update. The source of interest is modelled as a cluster of stationary point sources and source motion is accommodated by revising the point source cluster. The source modelling and its direct exploitation in the beamformer through covariance estimates are presented. An algorithm for sound source localization is used for speaker movement tracking and this information is exploited to update the spatial distribution in the source model. Evaluation in a real environment with a moving speaker shows a significant noise and hands-free interference suppression within the conventional telephone bandwidth. This is achieved with a negligible impact on speech distortion.

  • 13394. Yermeche, Zohra
    et al.
    Grbic, Nedelko
    Claesson, Ingvar
    Bind Subband Beamforming with Time-delay Constraints for Moving Source Speech Enhancement2007In: IEEE Transactions on Audio, Speech, and Language Processing, ISSN 1558-7916, E-ISSN 1558-7924, Vol. 15, no 8, p. 2360-2372 Article in journal (Refereed)
    Abstract [en]

    A new robust microphone array method to enhance speech signals generated by a moving person in a noisy environment is presented. This blind approach is based on a two-stage scheme. First, a subband time-delay estimation method is used to localize the dominant speech source. The second stage involves speech enhancement, based on the acquired spatial information, by means of a soft-constrained subband beamformer. The novelty of the proposed method involves considering the spatial spreading of the sound source as equivalent to a time-delay spreading, thus, allowing for the estimated intersensor time-delays to be directly used in the beamforming operations. In comparison to previous approaches, this new method requires no special array geometry, knowledge of the array manifold, or acquisition of calibration data to adapt the array weights. Furthermore, such a scheme allows for the beamformer to efficiently adapt to speaker movement. The robustness of the time-delay estimation of speech signals in high noise levels is improved by making use of the non-Gaussian nature of speech trough a subband Kurtosis-weighted structure. Evaluation in a real environment with a moving speaker shows promising results, with suppression levels of up to 16 dB for background noise and interfering (speech) signals, associated to a relatively small effect of speech distortion.

  • 13395. Yermeche, Zohra
    et al.
    Grbic, Nedelko
    Claesson, Ingvar
    Blind Subband Beamforming for Speech Enhancement of Multiple Speakers2006Conference paper (Refereed)
    Abstract [en]

    A new blind microphone array method to enhance speech signals generated by multiple sources in a noisy environment is proposed. This approach is based on a two-stage scheme. A subband time-delay estimation algorithm is first used to localize the dominant speech sources. The speech enhancement is performed in a second stage, based on the acquired spatial information, by means of a spatially constrained subband beamformer. The robustness of this structure is ensured by the spatial constraint constructed to include the discrepancies in the acoustical environment model as well as errors in the time-delay estimation. Such scheme also allows for an efficient adaptation of the beamformer to speakers movement. The proposed subband approach for time-delay estimation exploits the sparseness of speech signals in the time-frequency domain to localize multiple speakers simultaneously. It also provides means to select the number of target sources. Evaluation in a real environment shows promising results.

  • 13396. Yermeche, Zohra
    et al.
    Grbic, Nedelko
    Claesson, Ingvar
    Blind Subband Beamforming With Time-Delay Constraints for Moving Source Speech Enhancement2007In: IEEE Transactions on Audio, Speech, and Language Processing, ISSN 1558-7916, E-ISSN 1558-7924, Vol. 15, no 8, p. 2360-2372Article in journal (Refereed)
    Abstract [en]

    A new robust microphone array method to enhance speech signals generated by a moving person in a noisy environment is presented. This blind approach is based on a two-stage scheme. First, a subband time-delay estimation method is used to localize the dominant speech source. The second stage involves speech enhancement, based on the acquired spatial information, by means of a soft-constrained subband beamformer. The novelty of the proposed method involves considering the spatial spreading of the sound source as equivalent to a time-delay spreading, thus, allowing for the estimated intersensor time-delays to be directly used in the beamforming operations. In comparison to previous approaches, this new method requires no special array geometry, knowledge of the array manifold, or acquisition of calibration data to adapt the array weights. Furthermore, such a scheme allows for the beamformer to efficiently adapt to speaker movement. The robustness of the time-delay estimation of speech signals in high noise levels is improved by making use of the non-Gaussian nature of speech trough a subband Kurtosis-weighted structure. Evaluation in a real environment with a moving speaker shows promising results, with suppression levels of up to 16 dB for background noise and interfering (speech) signals, associated to a relatively small effect of speech distortion.

  • 13397. Yermeche, Zohra
    et al.
    Grbic, Nedelko
    Claesson, Ingvar
    Moving Source Speech Enhancement Using Time-Delay Estimation2005Conference paper (Refereed)
    Abstract [en]

    This paper presents a new constrained subband beamforming algorithm to enhance speech signals generated by a moving source in a noisy environment. The beamformer is based on the principle of a soft constraint calculated from an estimated source position. The soft constraint secures the spatial-temporal passage of the desired source signal in the adaptive update of the beamforming weights and guaranties the full rank property of the covariance matrix inverted in the update. This approach allows for an efficient adaptation of the beamformer to speaker movement by using a tracking algorithm for sound source time-delay estimation. The proposed method has the benefit of taking into consideration the discrepancies in the acoustical environment model as well as errors in the time-delay estimation. Evaluation in a real environment with a moving speaker in a hands-free situation shows up to 10~dB noise suppression and 20~dB interference suppression within the conventional telephone bandwidth. This is achieved with a negligible impact on target signal distortion.

  • 13398. Yermeche, Zohra
    et al.
    Grbic, Nedelko
    Claesson, Ingvar
    Speech enhancement of multiple moving sources based on subband clustering time-delay estimation2006Conference paper (Refereed)
    Abstract [en]

    A new robust blind microphone array method to enhance speech signals generated by multiple moving sources in a noisy environment is presented. This approach is based on a two-stage scheme. A subband clustering time-delay estimation algorithm is first used to localize the dominant speech sources. The speech enhancement is performed in a second stage, based on the acquired spatial information, by means of a soft-constrained subband beamformer. The robustness of this structure is ensured by the spatial constraint constructed to include the discrepancies in the acoustical environment model as well as errors in the time-delay estimation. Such scheme also allows for an efficient adaptation of the beamformer to speakers movement. The proposed subband clustering approach for time-delay estimation exploits the sparseness of speech signals in the time-frequency domain to localize multiple speakers simultaneously. It also provides means to select the number of target sources. Evaluation in a real environment with moving speakers shows promising results.

  • 13399. Yermeche, Zohra
    et al.
    Sällberg, Benny
    Grbic, Nedelko
    Claesson, Ingvar
    Real-Time DSP Implementation of a Subband Beamforming Algorithm for Dual Microphone Speech Enhancement2007Conference paper (Refereed)
    Abstract [en]

    A real-time Digital Signal Processor (DSP) based implementation of a subband beamforming algorithm and its evaluation for dual microphone speech enhancement is presented. The algorithm, a calibrated constrained beamformer, is described theoretically and a real-time structure is proposed, including an efficient approach for multichannel data transformation. Measurements show that the battery driven DSP implementation supports 20 h operation-time, with an improved Signal-to-Noise Ratio (SNR) of up to 14~dB in high-noise factory environment. Further, less than half the provided computational performance of the DSP is used by the proposed method, hence, processing of additional tasks may be included.

  • 13400.
    Yerragudi, Panduranga Sri Charan
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Balija, Venkatesh
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Identication and Matching of Headstamp of Cartridge Using Iris Detection Algorithm2016Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Identication of cartridge is very essential in the field of forensics, military or people who collect ammunitions. The cartridges can beidentied by their headstamps.This thesis presents work on identification and matching of cartridge headstamp from the image. The Libor Masek's open source iris recognition algorithm is considered for the identification of cartridge pattern from the image.The dataset is devoleped with the cartridge headstamp patterns and matching of cartridge headstamp patterns is implemented. For matching of the cartridge pattern the Hamming distance is considered as the metric to differentiate interclass and intraclass comparisons. Variance is used as a criteria to discard the unwanted areas of the cartridge headstamp pattern.Four distinct cartridge headstamp patterns are considered. Three cartridges of each headstamp pattern are considered for intra class comparisons. The validation of the method is performed.

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