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  • 251.
    chikkala, sai sandeep
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    EVALUATION CRITERIA FOR SELECTION OF API PRODUCTS: Practitioners' Perspective2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Context. The approach of developing software systems with the use of third partycomponents i.e. COTS or OSS has increased globally. In this study API product refers toeither a software component or a software service or both packaged together, that can beaccessed through an API. Developers are faced with plethora of alternative choices to selectan API product. With this increase in components adoption, API product providers are facedwith challenge of designing their product to be more attractive than others. This needs theproviders to be educated about the developer behavior when they choose an API product.Understanding the selection practices of developers can help providers to improve thepackaging of API products, making them more suitable for selection.

    Objectives. The objectives of this study is to investigate the criteria that developers usewhen reasoning about acceptability of a software component.

    Methods. A background study is performed to identify the evaluation criteria proposed inthe literature. An empirical study using Qualitative content analysis is performed. In the study the 480 reviews of different API products are analyzed to understand the criteria frompractitioners’ perspective.

    Results. 9 relevant criteria that developer use to reason about accepting or rejecting an APIProduct are identified. 30 sub criteria related to the 9 criteria are described in the study.

    Conclusions. This study concludes that the identified 9 criteria play an important role indeveloper assessment of the API product. It is also found that the criteria have significantimpact on the ratings of API product. These criteria could guide API product providers tomake better choices when developing the product.

  • 252.
    Chilukuri, Megh Phani Dutt
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Power Profiling of Network Switches2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Context In the present world, there is an increase in the usage of the telecommunication networking services, as there is a need of efficient networking services in various fields which can be obtained by using the efficient networking components. For that purpose we have to know about the components parameters. One of the most important parameter is the energy usage of networking components. Therefore, there is a need in power profiling of the network switches.

    Objectives The objective of this research is to profile the power usage of different network components(Switches) for various load scenarios. Power measurements are done by using the open energy monitoring tool called emonpi.

    Methods The research method has been carried out by using an experimental test bed. In this research, we are going to conduct the experiments with different configurations to obtain different load conditions for sources and destinations which will be passed through DUT(Device Under Test). For that DUT’s we will measure power usage by monitoring tool called emonpi. Then the experiments are conducted for different load scenarios for different switches and results are discussed.

    Conclusion From the results obtained, the Power profiles of different DUT’s are tabulated and analyzed. These were done under different ports and load scenarios for Cisco2950, Cisco3560 and Netgear GS-724T. From the results and analysis it can be stated that the power usage of Cisco 2950 is having the maximum power usage in all the considered scenarios with respect to packet rate and also number of active ports. The Netgear-GS724T is having the minimum power usage from the three switches as it having the green switch characteristics in all scenarios. And the Cisco 3560 is in between the above two switches as it is having energy efficient management from Cisco. From this we have proposed a simple model for energy/power measurement.

  • 253.
    Chinta, Ruthvik
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Measurement of Game Immersion through Subjective Approach2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Context. People in recent times are getting engaged more often in playing video games. Few play for enjoyment, few play for stress relaxation and so on. Generally, the degree of involvement of a player with the game is described as game immersion. People when immersed into playing a game doesn't realize that they are getting dissociated with the outside world and are losing track of time.

    Objectives. In this research, the main objective is to explore the relationship between the game immersion and game experience using the five factors of game immersion. In addition, the study also involves exploring different methods that can be used to measure game immersion.

    Methods. In this research, initially literature review has been conducted to explore the meaning of game immersion and also different methods that can be used to measure it and next user studies in the form an experiment was conducted to measure game immersion. After the experiment was conducted regression analysis was performed on the data obtained from the results to describe the relation between game immersion and game experience.

    Results. After the experiment participants were asked to answer the IEQ questionnaire and the answers obtained from the questionnaire are analyzed using regression analysis. An inverse linear regression was observed between game immersion and game experience.

    Conclusions. After analyzing the data, from the observed inverse linear regression, it is concluded that game immersion levels decrease with the increase in the game experience.

  • 254.
    Chivukula, Krishna Varaynya
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Monitoring and Analysis of CPU load relationships between Host and Guests in a Cloud Networking Infrastructure: An Empirical Study2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 255.
    Chodapaneedi, Mani Teja
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Manda, Samhith
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Engagement of Developers in Open Source Projects: A Multi-Case Study2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

     In the present world, the companies on using the open source projects have been tend to increase in the innovation and productivity which is beneficial in sustaining the competence. These involve various developers across the globe who may be contributing to several other projects, they constantly engage with the project to improve and uplift the overall project. In each open source project, the level of intensity and the motivation with which the developers engage and contribute vary among time.

    Initially the research is aimed to identify how the engagement and activity of the developers in open source projects vary over time. Secondly to assess the reasons over the variance in engagement activities of the developers involved in various open source projects.

    Firstly, a literature review was conducted to identify the list of available metrics that are helpful to analyse the developer’s engagement in open source projects. Secondly, we conducted a multi-case study, that involved the investigation of developer’s engagement in 10 different open source projects of Apache foundation. The GitHub repositories were mined to gather the data regarding the engagement activities of the developers over the selected projects. To identify the reasons for the variation in engagement and activity of developers, we analysed documentation about each project and also interviewed 10 developers and 5 instructors, who provided additional insights about the challenges faced to contribute in open source projects.

    The results of this research contain the list of factors that affect the developer’s engagement with open source projects which are extracted from the case studies and are strengthened through interviews. From the data that is collected by performing repository mining, the selected projects have been categorized with the increase, decrease activeness of developers among the selected projects. By utilizing the archival data that is collected from the selected projects, the factors corporate support, community involvement, distribution of issues and contributions to open source projects and specificity of guidelines have been identified as the crucial and key factors upon the success of the open source projects reflecting the engagement of contributors. In addition to this finding the insights on using open source projects are also collected from both perspectives of developers and instructors are presented.

     This research had provided us a deeper insight on the working of open source projects and driving factors that influence engagement and activeness of the contributors. It has been evident from this research that the stated factors corporate support, community involvement, distribution of issues and contributions to open source projects and specificity of guidelines impacts the engagement and activeness of the developers. So, the open source projects minimally satisfying these projects can tend to see the increase of the engagement and activeness levels of the contributors. It also helps to seek the existing challenges and benefits upon contributing to open source projects from different perspectives.

  • 256.
    Chu, Thi My Chin
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    On Capacity of Full-Duplex Cognitive Cooperative Radio Networks with Optimal Power Allocation2017In: 2017 IEEE WIRELESS COMMUNICATIONS AND NETWORKING CONFERENCE (WCNC), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    In this paper, we examine a full-duplex transmission scheme for cognitive cooperative radio networks (CCRNs) to improve capacity. In this network, the secondary transmitter and secondary relay are allowed to utilize the licensed spectrum of the primary user by using underlay spectrum access. We assume that the CCRN is subject to the interference power constraint of the primary receiver and maximum transmit power limit of the secondary transmitter and secondary relay. Under these constraints, we propose an optimal power allocation policy for the secondary transmitter and the secondary relay based on average channel state information (CSI) to optimize capacity. Then, we derive an expression for the corresponding achievable capacity of the secondary network over Nakagami-m fading. Numerical results are provided for several scenarios to study the achievable capacity that can be offered by this full-duplex underlay CCRN using the proposed optimal power allocation scheme.

  • 257.
    Chu, Thi My Chinh
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    On the Performance Assessment of Advanced Cognitive Radio Networks2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Due to the rapid development of wireless communications together with the inflexibility of the current spectrum allocation policy, radio spectrum becomes more and more exhausted. One of the critical challenges of wireless communication systems is to efficiently utilize the limited frequency resources to be able to support the growing demand of high data rate wireless services. As a promising solution, cognitive radios have been suggested to deal with the scarcity and under-utilization of radio spectrum. The basic idea behind cognitive radios is to allow unlicensed users, also called secondary users (SUs), to access the licensed spectrum of primary users (PUs) which improves spectrum utilization. In order to not degrade the performance of the primary networks, SUs have to deploy interference control, interference mitigating, or interference avoidance techniques to minimize the interference incurred at the PUs. Cognitive radio networks (CRNs) have stimulated a variety of studies on improving spectrum utilization. In this context, this thesis has two main objectives. Firstly, it investigates the performance of single hop CRNs with spectrum sharing and opportunistic spectrum access. Secondly, the thesis analyzes the performance improvements of two hop cognitive radio networks when incorporating advanced radio transmission techniques. The thesis is divided into three parts consisting of an introduction part and two research parts based on peer-reviewed publications. Fundamental background on radio propagation channels, cognitive radios, and advanced radio transmission techniques are discussed in the introduction. In the first research part, the performance of single hop CRNs is analyzed. Specifically, underlay spectrum access using M/G/1/K queueing approaches is presented in Part I-A while dynamic spectrum access with prioritized traffics is studied in Part I-B. In the second research part, the performance benefits of integrating advanced radio transmission techniques into cognitive cooperative radio networks (CCRNs) are investigated. In particular, opportunistic spectrum access for amplify-and-forward CCRNs is presented in Part II-A where collaborative spectrum sensing is deployed among the SUs to enhance the accuracy of spectrum sensing. In Part II-B, the effect of channel estimation error and feedback delay on the outage probability and symbol error rate (SER) of multiple-input multiple-output CCRNs is investigated. In Part II-C, adaptive modulation and coding is employed for decode-and-forward CCRNs to improve the spectrum efficiency and to avoid buffer overflow at the relay. Finally, a hybrid interweave-underlay spectrum access scheme for a CCRN is proposed in Part II-D. In this work, the dynamic spectrum access of the PUs and SUs is modeled as a Markov chain which then is utilized to evaluate the outage probability, SER, and outage capacity of the CCRN.

  • 258.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Phan, Hoc
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Adaptive Modulation and Coding with Queue Awareness in Cognitive Incremental Decode-and-Forward Relay Networks2014Conference paper (Refereed)
    Abstract [en]

    This paper studies the performance of adaptive modulation and coding in a cognitive incremental decode-and-forward relaying network where a secondary source can directly communicate with a secondary destination or via an intermediate relay. To maximize transmission efficiency, a policy which flexibly switches between the relaying and direct transmission is proposed. In particular, the transmission, which gives higher average transmission efficiency, will be selected for the communication. Specifically, the direct transmission will be chosen if its instantaneous signal-to-noise ratio (SNR) is higher than one half of that of the relaying transmission. In this case, the appropriate modulation and coding scheme (MCS) of the direct transmission is selected only based on its instantaneous SNR. In the relaying transmission, since the MCS of the transmissions from the source to the relay and from the relay to the destination are implemented independently to each other, buffering of packets at the relay is necessary. To avoid buffer overflow at the relay, the MCS for the relaying transmission is selected by considering both the queue state and the respective instantaneous SNR. Finally, a finite-state Markov chain is modeled to analyze key performance indicators such as outage probability and average transmission efficiency of the cognitive relay network.

  • 259.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Phan, Hoc
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Cognitive AF Relay Assisting both Primary and Secondary Transmission with Beamforming2014Conference paper (Refereed)
    Abstract [en]

    This paper investigates the system performance of a cognitive relay network with underlay spectrum sharing wherein the relay is exploited to assist both the primary and secondary transmitters in forwarding their signals to the respective destinations. To exploit spatial diversity, beamforming transmission is implemented at the transceivers of the primary and secondary networks. Particularly, exact expressions for the outage probability and symbol error rate (SER) of the primary transmission and tight bounded expressions for the outage probability and SER of the secondary transmission are derived. Furthermore, an asymptotic analysis for the primary network, which is utilized to investigate the diversity and coding gain of the network, is developed. Finally, numerical results are presented to show the benefits of the proposed system.

  • 260.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Phan, Hoc
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Delay Analysis for Cognitive Ad Hoc Networks Using Multi-channel Medium Access Control2014In: IET Communications, ISSN 1751-8628, E-ISSN 1751-8636, Vol. 8, no 7, p. 1083-1093Article in journal (Refereed)
    Abstract [en]

    In this study, the authors analyse the average end-to-end packet delay for a cognitive ad hoc network where multiple secondary nodes randomly contend for accessing the licensed bands of primary users in non-slotted time mode. Before accessing the licensed bands, each node must perform spectrum sensing and collaboratively exchange the sensing results with other nodes of the corresponding communication as a means of improving the accuracy of spectrum sensing. Furthermore, the medium access control with collision avoidance mechanism based distributed coordination function specified by IEEE802.11 is applied to coordinate spectrum access for this cognitive ad hoc network. To evaluate the system performance, the authors model the considered network as an open G/G/1 queuing network and utilise the method of diffusion approximation to analyse the end-to-end packet delay. The authors’ analysis takes into account not only the number of secondary nodes, the arrival rate of primary users and the arrival rate of secondary users but also the effect of the number of licensed bands when assessing the average end-to-end packet delay of the networks.

  • 261.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Phan, Hoc
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Dynamic Spectrum Access for Cognitive Radio Networks with Prioritized Traffics2014In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 18, no 7, p. 1218-1221Article in journal (Refereed)
    Abstract [en]

    We develop a dynamic spectrum access (DSA) strategy for cognitive radio networks where prioritized traffic is considered. Assume that there are three classes of traffic, one traffic class of the primary user and two traffic classes of the secondary users, namely, Class 1 and Class 2. The traffic of the primary user has the highest priority, i.e., the primary users can access the spectrum at any time with the largest bandwidth demand. Furthermore, Class 1 has higher access and handoff priority as well as larger bandwidth demand as compared to Class 2. To evaluate the performance of the proposed DSA, we model the state transitions for DSA as a multi-dimensional Markov chain with three-state variables which present the number of packets in the system of the primary users, the secondary Class 1, and secondary Class 2. In particular, the blocking probability and dropping probability of the two secondary traffic classes are assessed.

  • 262.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Phan, Hoc
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Hybrid Interweave-Underlay Spectrum Access for Cognitive Cooperative Radio Networks2014In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 62, no 7, p. 2183-2197Article in journal (Refereed)
    Abstract [en]

    In this paper, we study a hybrid interweave-underlay spectrum access system that integrates amplify-and-forward relaying. In hybrid spectrum access, the secondary users flexibly switch between interweave and underlay schemes based on the state of the primary users. A continuous-time Markov chain is proposed to model and analyze the spectrum access mechanism of this hybrid cognitive cooperative radio network (CCRN). Utilizing the proposed Markov model, steady-state probabilities of spectrum access for the hybrid CCRN are derived. Furthermore, we assess performance in terms of outage probability, symbol error rate (SER), and outage capacity of this CCRN for Nakagami-m fading with integer values of fading severity parameter m. Numerical results are provided showing the effect of network parameters on the secondary network performance such as the primary arrival rate, the distances from the secondary transmitters to the primary receiver, the interference power threshold of the primary receiver in underlay mode, and the average transmit signal-to-noise ratio of the secondary network in interweave mode. To show the performance improvement of the CCRN, comparisons for outage probability, SER, and capacity between the conventional underlay scheme and the hybrid scheme are presented. The numerical results show that the hybrid approach outperforms the conventional underlay spectrum access.

  • 263.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Phan, Hoc
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Performance analysis of MIMO cognitive amplify-and-forward relay networks with orthogonal space–time block codes2015In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, Vol. 15, p. 1659-1679Article in journal (Refereed)
    Abstract [en]

    In this paper, we study the performance of multiple-input multiple-output cognitive amplify-and-forward relay networks using orthogonal space–time block coding over independent Nakagami-m fading. It is assumed that both the direct transmission and the relaying transmission from the secondary transmitter to the secondary receiver are applicable. In order to process the received signals from these links, selection combining is adopted at the secondary receiver. To evaluate the system performance, an expression for the outage probability valid for an arbitrary number of transceiver antennas is presented. We also derive a tight approximation for the symbol error rate to quantify the error probability. In addition, the asymptotic performance in the high signal-to-noise ratio regime is investigated to render insights into the diversity behavior of the considered networks. To reveal the effect of network parameters on the system performance in terms of outage probability and symbol error rate, selected numerical results are presented. In particular, these results show that the performance of the system is enhanced when increasing the number of antennas at the transceivers of the secondary network. However, increasing the number of antennas at the primary receiver leads to a degradation in the secondary system performance.

  • 264.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Zepernick, Hans-Juergen
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies. Blekinge Inst Technol, SE-37179 Karlskrona, Sweden..
    Capacity Analysis of Two-Tier Networks with MIMO Cognitive Small Cells in Nagakami-m Fading2017In: 2017 IEEE 13TH INTERNATIONAL CONFERENCE ON WIRELESS AND MOBILE COMPUTING, NETWORKING AND COMMUNICATIONS (WIMOB), IEEE , 2017, p. 457-463Conference paper (Refereed)
    Abstract [en]

    In this paper, we consider a two-tier cellular network consisting of a primary macro cell base station (PMBS) which is overlaid by cognitive small cell base stations (CSBSs) to achieve efficient spectrum utilization. The deployment of two-tier cellular networks can provide higher capacity for the system but also causes cross-tier, intra-tier, and inter-tier interference within the cellular networks. Thus, we employ transmit and receive beamforming in the considered two-tier cellular network to mitigate interference. We first design the receive beamforming vector for a primary user (PU) such that it cancels all inter-tier interference from other PUs. Then, the transmit beamforming vectors at the secondary users (SUs) are designed to null out the cross-tier interference to the PUs. Further, the receive beamforming vectors at the SUs are designed to mitigate the crosstier interference from the PUs to the SUs. Finally, the transmit beamforming vector at the PMBS is designed to maximize the signal-to-interference-plus-noise ratio at the PUs. To quantify the performance of the system, we derive an expression for the channel capacity in the downlink from the CSBSs to the SUs. Numerical results are provided to reveal the effect of network parameters such as intra-tier interference distances, fading conditions, and number of antennas on the channel capacity of the SUs.

  • 265.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Zepernick, Hans-Juergen
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Downlink outage analysis for cognitive cooperative radio networks employing non-orthogonal multiple access2018In: 2018 IEEE 7th International Conference on Communications and Electronics, ICCE 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 27-32Conference paper (Refereed)
    Abstract [en]

    In this paper, we employ power-domain non-orthogonal multiple access (NOMA) to simultaneously transmit signals to both a primary user (PU) and a secondary user (SU) of a cognitive cooperative radio network (CCRN). Higher priority is given to the PU over the SU by keeping the power allocation coefficients at the base station (BS) and relay (R) above a certain threshold. In this way, similar as the interference power limit imposed by the PU in a conventional underlay CCRN, the power allocation coefficients at the BS and R of the CCRN can be controlled to maintain a given outage performance. Analytical expressions of the cumulative distribution function of the end-to-end signal-to-interference-plus-noise ratios at the PU and SU are derived and then used to assess the outage probabilities of both users. Numerical results are presented to study the impact of system parameters on outage performance of the CCRN with power-domain NOMA. In addition, it is illustrated that increased downlink performance can be obtained by combining power-domain NOMA with CCRNs. © 2018 IEEE.

  • 266.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Zepernick, Hans-Juergen
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Non-orthogonal multiple access for DF cognitive cooperative radio networks2018In: IEEE International Conference on Communications Workshops, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 1-6Conference paper (Refereed)
    Abstract [en]

    In this paper, we study a power domain non-orthogonal multiple access (NOMA) scheme for cognitive cooperative radio networks (CCRNs). In the proposed scheme, a secondary transmitter communicates with two secondary users (SUs) by allocating transmit powers inversely proportional to the channel power gains on the links to the respective SUs. A decode-and-forward (DF) secondary relay is deployed which decodes the superimposed signals associated with the two SUs. Then, power domain NOMA is used to forward the signals from the relay to the two SUs based on the channel power gains on the corresponding two links. Mathematical expressions for the outage probability and ergodic capacity of each SU and the overall power domain NOMA CCRN are derived. Numerical results are provided to reveal the impact of the power allocation coefficients at the secondary transmitter and secondary relay, the interference power threshold at the primary receiver, and the normalized distances of the SUs on the outage probability and ergodic capacity of each SU and the whole NOMA system. © 2018 IEEE.

  • 267.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Zepernick, Hans-Juergen
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    On Secrecy Capacity of Full-Duplex Cognitive Cooperative Radio Networks2017In: 2017 IEEE GLOBECOM WORKSHOPS (GC WKSHPS), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    In this paper, we analyze the secrecy capacity of a full-duplex underlay cognitive cooperative radio network (CCRN) in the presence of an eavesdropper and under the interference power constraint of a primary network. The full-duplex mode is used at the secondary relay to improve the spectrum efficiency which in turn leads to an improvement of the secrecy capacity of the full-duplex CCRN. We utilize an approximation-and-fitting method to convert the complicated expression of the signal-to-interference-plus-noise ratio into polynomial form which is then utilized to derive an expression for the secrecy capacity. Numerical results are provided to illustrate the effect of network parameters such as transmit power, interference power limit, self-interference parameters of the full-duplex mode, and distances among links on the secrecy capacity. To reveal the benefits of the full-duplex CCRN, we compare the secrecy capacity obtained when the secondary relay operates in full-duplex and half-duplex mode.

  • 268.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Zepernick, Hans-Juergen
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Optimal Power Allocation for Hybrid Cognitive Cooperative Radio Networks with Imperfect Spectrum Sensing2018In: IEEE Access, E-ISSN 2169-3536, Vol. 6, p. 10365-10380Article in journal (Refereed)
    Abstract [en]

    In this paper, two optimal power allocation strategies for hybrid interweave-underlay cognitive cooperative radio networks (CCRNs) are proposed to maximize channel capacity and minimize outage probability. The proposed power allocation strategies are derived for the case of Rayleigh fading taking into account the impact of imperfect spectrum sensing on the performance of the hybrid CCRN. Based on the optimal power allocation strategies, the transmit powers of the secondary transmitter and secondary relay are adapted according to the fading conditions, the interference power constraint imposed by the primary network (PN), the interference from the PN to the hybrid CCRN, and the total transmit power limit of the hybrid CCRN. Numerical results are provided to illustrate the effect of the interference power constraint of the PN, arrival rate of the PN, imperfect spectrum sensing, and the transmit power constraint of the hybrid CCRN on channel capacity and outage probability. Finally, comparisons of the channel capacity and outage probability of underlay, overlay, and hybrid interweaveunderlay CCRNs are presented to show the advantages of the hybrid spectrum access. OAPA

  • 269.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Zepernick, Hans-Juergen
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies. Blekinge Inst Technol, SE-37179 Karlskrona, Sweden..
    Outage Probability and Secrecy Capacity of a Non-orthogonal Multiple Access System2017In: 11th International Conference on Signal Processing and Communication Systems, ICSPCS, 2017 / [ed] Wysocki, TA Wysocki, BJ, IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    In this paper, we analyze the outage probability and secrecy capacity of a non-orthogonal multiple access (NOMA) system in the presence of an eavesdropper. In order to enhance spectral efficiency, a base station communicates with two users simultaneously in the same frequency band by superpimposing the transmit signals to the users in the power domain. Specifically, the user with the worse channel conditions is allocated higher power such that it is able to directly decode its signal from the received superimposed signal. At the user with the better channel conditions, the interference due to NOMA is processed by successive interference cancelation. Given these system settings and accounting for decoding thresholds, we analyze the outage probability of the NOMA system over Rayleigh fading channels. Furthermore, based on the locations of the users and eavesdropper, the secrecy capacity is analyzed to assess the level of security provided to the legitimate users in the presence of an eavesdropper. Here, the decoding thresholds of legitimate users and eavesdropper are also included in the analysis of the secrecy capacity. Through numerical results, the effects of network parameters on system performance are assessed as well as the the superiority of NOMA in terms of secrecy capacity over traditional orthogonal multiple access.

  • 270.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Zepernick, Hans-Juergen
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies. Blekinge Inst Technol, SE-37179 Karlskrona, Sweden..
    Outage Probability of a Hybrid AF-DF Protocol for Two-Way Underlay Cognitive Cooperative Radio Networks2017In: 11th International Conference on Signal Processing and Communication Systems, ICSPCS 2017 / [ed] Wysocki, TA Wysocki, BJ, IEEE , 2017, p. 1-6Conference paper (Refereed)
    Abstract [en]

    In this paper, we study a hybrid amplify-and-forward (AF) and decode-and-forward (DF) scheme for two-way cognitive cooperative radio networks (CCRNs). The proposed scheme applies the AF scheme when the signal-to-interferenceplus-noise ratio (SINR) at the relay is below a predefined threshold such that the relay cannot successfully decode the signal. On the other hand, when the SINR at the relay is greater than the predefined threshold, it decodes the signal and then forwards it to the destination, i.e. avoids noise and interference amplification at the relay. An analytical expression of the outage probability of the hybrid AF-DF two-way CCRN is derived based on the probability density function and cumulative distribution function of the SINR in AF and DF mode. Numerical results are provided to illustrate the influence of network parameters such as transmit power, interference power constraint of the primary network, fading conditions, and link distances on the outage probability. Finally, the numerical results show that the hybrid strategy is able to improve system performance significantly compared to conventional AF or DF relaying.

  • 271.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Zepernick, Hans-Juergen
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Performance of a Non-orthogonal Multiple Access System with Full-Duplex Relaying2018In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, no 10, p. 2084-2087Article in journal (Refereed)
    Abstract [en]

    In this paper, we study a power-domain nonorthogonal multiple access (NOMA) system in which a base station (BS) superimposes the transmit signals to the users. To enhance spectral efficiency and link reliability for the far-distance user, a full-duplex (FD) relay assists the BS while the neardistance user is reached over the direct link. For this setting, we analyze outage probability and sum rate of the NOMA system over Nakagami-m fading with integer fading severity parameter m. Numerical results are provided for outage probability and sum rate to show the effect of system parameters on the performance of the FD NOMA system over Nakagami-m fading. IEEE

  • 272.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Zepernick, Hans-Juergen
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Performance Optimization for Hybrid Two-Way Cognitive Cooperative Radio Networks with Imperfect Spectrum Sensing2018In: IEEE Access, E-ISSN 2169-3536, Vol. 6, p. 70582-70596Article in journal (Refereed)
    Abstract [en]

    In this paper, we consider a two-way cognitive cooperative radio network (TW-CCRN) with hybrid interweaveunderlay spectrum access in the presence of imperfect spectrum sensing. Power allocation strategies are proposed that maximize the sum-rate and minimize the outage probability of the hybrid TW-CCRN. Specifically, based on the state of the primary network (PN), fading conditions, and system parameters, suitable power allocation strategies subject to the interference power constraint of the PN are derived for each transmission scenario of the hybrid TW-CCRN. Given the proposed power allocation strategies, we analyze the sum-rate and outage probability of the hybrid TW-CCRN over Rayleigh fading taking imperfect spectrum sensing into account. Numerical results are presented to illustrate the effect of the arrival rate, interference power threshold, transmit power of the PN, imperfect spectrum sensing, and maximum total transmit power on the sum-rate and outage probability of the hybrid TW-CCRN. OAPA

  • 273.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Zepernick, Hans-Juergen
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Symbol error rate and achievable rate of cognitive cooperative radio networks utilizing non-orthogonal multiple access2018In: 2018 IEEE 7th International Conference on Communications and Electronics, ICCE 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, Vol. Code 141951, p. 33-38Conference paper (Refereed)
    Abstract [en]

    In this paper, we study the employment of power-domain non-orthogonal multiple access (NOMA) concepts for a cooperative cognitive relay network (CCRN) downlink system in order to allow a base station (BS) to simultaneously transmit signals to a primary user (PU) and a secondary user (SU). As such, the considered system falls into the field of cognitive radio inspired power-domain NOMA. In this scheme, the interference power constraint of the PU imposed to SUs in conventional underlay CCRNs is replaced by controlling the power allocation coefficients at the BS and relay. Specifically, expressions for the symbol error rates at the PU and SU for different modulation schemes as well as expressions for the achievable rates are derived. On this basis, the effect of system parameters such as total transmit power and power allocation coefficients on the performance of the CCRN with power-domain NOMA is numerically studied. These numerical results provide insights into selecting favorable operation modes of the CCRN employing power-domain NOMA. © 2018 IEEE.

  • 274.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Zepernick, Hans-Juergen
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Phan, H.
    Duy Tan University, VNM.
    MAC Protocol for Opportunistic Spectrum Access in Multi-Channel Cognitive Relay Networks2017In: IEEE Vehicular Technology Conference, Institute of Electrical and Electronics Engineers Inc. , 2017Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose a medium access control (MAC) protocol for multi-channel cognitive cooperative radio networks (CCRNs). In this protocol, each secondary user (SU) senses for spectrum opportunities within M licensed bands of the primary users (PUs). To enhance the accuracy of spectrum sensing, we employ cooperative sequential spectrum sensing where SUs mutually exchange their sensing results. Moreover, the information obtained from cooperative spectrum sensing at the physical layer is integrated into the channel negotiation process at the MAC layer to alleviate the hidden terminal problem. Finally, the performance of the proposed MAC protocol in terms of aggregate throughput of the CCRNs is analyzed. Numerical results are provided to assess the impact of channel utilization by PUs, number of contenting CCRNs, number of licensed bands, and false alarm probability of SUs on the aggregate throughput. © 2017 IEEE.

  • 275.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Zepernick, Hans-Juergen
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Phan, Hoc
    Channel Reservation for Dynamic Spectrum Access of Cognitive Radio Networks with Prioritized Traffic2015In: 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATION WORKSHOP, IEEE Communications Society, 2015, p. 883-888Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose a strategy to coordinate the dynamic spectrum access (DSA) of different types of traffic. It is assumed that the DSA assigns spectrum bands to three kinds of prioritized traffic, the traffic of the primary network, the Class 1 traffic and Class 2 traffic of the secondary network. Possessing the licensed spectrum, the primary traffic has the highest access priority and can access the spectrum bands at anytime. The secondary Class 1 traffic has higher priority compared to secondary Class 2 traffic. In this system, a channel reservation scheme is deployed to control spectrum access of the traffic. Specifically, the optimal number of reservation channels is applied to minimize the forced termination probability of the secondary traffic while satisfying a predefined blocking probability of the primary network. To investigate the system performance, we model state transitions of the DSA as a multi-dimensional Markov chain with three-state variables representing the number of primary, Class 1, and Class 2 packets in the system. Based on this chain, important performance measures, i.e., blocking probability and forced termination probability are derived for the Class 1 and Class 2 secondary traffic.

  • 276.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Zepernick, Hans-Juergen
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Sundstedt, Veronica
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Analysis of Variance of Opinion Scores for MPEG-4 Scalable and Advanced Video Coding2018In: 2018 12TH INTERNATIONAL CONFERENCE ON SIGNAL PROCESSING AND COMMUNICATION SYSTEMS (ICSPCS) / [ed] Wysocki, TA Wysocki, BJ, IEEE , 2018Conference paper (Refereed)
    Abstract [en]

    In this paper, we conduct an analysis of variance (ANOVA) on opinion scores for MPEG-4 scalable video coding (SVC) and advanced video coding (AVC) standards. This work resorts on a publicly available database providing opinion scores from subjective experiments for several scenarios such as different bit rates and resolutions. In particular, ANOVA is used for statistical hypothesis testing to compare two or more sets of opinion scores instead of being constrained to pairs of sets of opinion scores as would be the case for t-tests. As the ANOVA tests of the different scenarios are performed for mean opinion scores (MOS), box plots are also provided in order to assess the distribution of the opinion scores around the median. It is shown that the opinion scores given to the reference videos in SVC and AVC for different resolutions are statistically significantly similar regardless of the content. Further, for the opinion scores of the considered database, the ANOVA tests support the hypothesis that AVC generally outperforms SVC although the performance difference may be less pronounced for higher bit rates. This work also shows that additional insights on the results of subjective experiments can be obtained by extending the analysis of opinion scores beyond MOS to ANOVA tests and box plots.

  • 277.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Phan, Hoc
    Univ Reading, GBR.
    Hybrid spectrum access with relay assisting both primary and secondary networks under imperfect spectrum sensing2016In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, article id 244Article in journal (Refereed)
    Abstract [en]

    This paper proposes a novel hybrid interweave-underlay spectrum access for a cognitive amplify-and-forward relay network where the relay forwards the signals of both the primary and secondary networks. In particular, the secondary network (SN) opportunistically operates in interweave spectrum access mode when the primary network (PN) is sensed to be inactive and switches to underlay spectrum access mode if the SN detects that the PN is active. A continuous-time Markov chain approach is utilized to model the state transitions of the system. This enables us to obtain the probability of each state in the Markov chain. Based on these probabilities and taking into account the impact of imperfect spectrum sensing of the SN, the probability of each operation mode of the hybrid scheme is obtained. To assess the performance of the PN and SN, we derive analytical expressions for the outage probability, outage capacity, and symbol error rate over Nakagami-m fading channels. Furthermore, we present comparisons between the performance of underlay cognitive cooperative radio networks (CCRNs) and the performance of the considered hybrid interweave-underlay CCRN in order to reveal the advantages of the proposed hybrid spectrum access scheme. Eventually, with the assistance of the secondary relay, performance improvements for the PN are illustrated by means of selected numerical results.

  • 278.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Phan, Hoc
    Duy Tan Univ, VNM.
    Optimal Secrecy Capacity of Underlay Cognitive Radio Networks with Multiple Relays2016In: MILCOM 2016 - 2016 IEEE MILITARY COMMUNICATIONS CONFERENCE, 2016, p. 162-167Conference paper (Refereed)
    Abstract [en]

    In this paper, we study the secrecy capacity of an underlay cooperative cognitive radio network (CCRN) where multiple relays are deployed to assist the secondary transmission. An optimal power allocation algorithm is proposed for the secondary transmitter and secondary relays to obtain the maximum secrecy capacity while satisfy the interference power constraint at the primary receiver and the transmit power budget of the CCRN. Since the optimization problem for the secrecy capacity is non-convex, we utilize an approximation and fitting method to convert the optimization problem into a geometric programming problem which then is solved by applying the Logarithmic barrier function. Numerical results are provided to study the effect of network parameters on the secrecy capacity. Through the numerical results, the advantage of the proposed power allocation algorithm compared to equal power allocation can also be observed.

  • 279.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Phan, Hoc
    Performance Evaluation of Cognitive Multi-Relay Networks with Multi-Receiver Scheduling2014Conference paper (Refereed)
    Abstract [en]

    In this paper, we investigate the performance of cognitive multiple decode-and-forward relay networks under the interference power constraint of the primary receiver wherein the cognitive downlink channel is shared among multiple secondary relays and secondary receivers. In particular, only one relay and one secondary receiver which offers the highest instantaneous signal-to-noise ratio is scheduled to transmit signals. Accordingly, only one transmission route that offers the best end-to-end quality is selected for communication at a particular time instant. To quantify the system performance, we derive expressions for outage probability and symbol error rate over Nakagami-m fading with integer values of fading severity parameter m. Finally, numerical examples are provided to illustrate the effect of system parameters such as fading conditions, the number of secondary relays and secondary receivers on the secondary system performance.

  • 280.
    Chunduri, Annapurna
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    An Effective Verification Strategy for Testing Distributed Automotive Embedded Software Functions: A Case Study2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Context. The share and importance of software within automotive vehicles is growing steadily. Most functionalities in modern vehicles, especially safety related functions like advanced emergency braking, are controlled by software. A complex and common phenomenon in today’s automotive vehicles is the distribution of such software functions across several Electronic Control Units (ECUs) and consequently across several ECU system software modules. As a result, integration testing of these distributed software functions has been found to be a challenge. The automotive industry neither has infinite resources, nor has the time to carry out exhaustive testing of these functions. On the other hand, the traditional approach of implementing an ad-hoc selection of test scenarios based on the tester’s experience, can lead to test gaps and test redundancies. Hence, there is a pressing need within the automotive industry for a feasible and effective verification strategy for testing distributed software functions.

    Objectives. Firstly, to identify the current approach used to test the distributed automotive embedded software functions in literature and in a case company. Secondly, propose and validate a feasible and effective verification strategy for testing the distributed software functions that would help improve test coverage while reducing test redundan- cies and test gaps.

    Methods. To accomplish the objectives, a case study was conducted at Scania CV AB, Södertälje, Sweden. One of the data collection methods was through conducting interviews of different employees involved in the software testing activities. Based on the research objectives, an interview questionnaire with open-ended and close-ended questions has been used. Apart from interviews, data from relevant ar- tifacts in databases and archived documents has been used to achieve data triangulation. Moreover, to further strengthen the validity of the results obtained, adequate literature support has been presented throughout. Towards the end, a verification strategy has been proposed and validated using existing historical data at Scania.

    Conclusions. The proposed verification strategy to test distributed automotive embedded software functions has given promising results by providing means to identify test gaps and test redundancies. It helps establish an effective and feasible approach to capture function test coverage information that helps enhance the effectiveness of integration testing of the distributed software functions. 

  • 281.
    Chunduri, Annapurna
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Feldt, Robert
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Adenmark, Mikael
    Scania AB, SWE.
    An effective verification strategy for testing distributed automotive embedded software functions: A case study2016In: Lecture Notes in Computer Science / [ed] Amasaki S.,Mikkonen T.,Felderer M.,Abrahamsson P.,Duc A.N.,Jedlitschka A., 2016, p. 233-248Conference paper (Refereed)
    Abstract [en]

    Integration testing of automotive embedded software functions that are distributed across several Electronic Control Unit (ECU) system software modules is a complex and challenging task in today’s automotive industry. They neither have infinite resources, nor have the time to carry out exhaustive testing of these functions. On the other hand, the traditional approach of implementing an ad-hoc selection of test scenarios based on the testers’ experience typically leads to both test gaps and test redundancies. Here, we address this challenge by proposing a verification strategy that enhances the process in order to identify and mitigate such gaps and redundancies in automotive system software testing. This helps increase test coverage by taking more data-driven decisions for integration testing of the functions. The strategy was developed in a case study at a Swedish automotive company that involved multiple data collection steps. After static validation of the proposed strategy it was evaluated on one distributed automotive software function, the Fuel Level Display, and found to be both feasible and effective. © Springer International Publishing AG 2016.

  • 282.
    Cicchetti, Antonio
    et al.
    Malardalen Univ, Vasteras, Sweden..
    Borg, Markus
    SICS Swedish Inst Comp Sci, Kista, Sweden..
    Sentilles, Severine
    Malardalen Univ, Vasteras, Sweden..
    Wnuk, Krzysztof
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Carlson, Jan
    Malardalen Univ, Vasteras, Sweden..
    Papatheocharous, Efi
    SICS Swedish Inst Comp Sci, Kista, Sweden..
    Towards Software Assets Origin Selection Supported by a Knowledge Repository2016In: PROCEEDINGS 2016 1ST INTERNATIONAL WORKSHOP ON DECISION MAKING IN SOFTWARE ARCHITECTURE, IEEE Computer Society, 2016, p. 22-29Conference paper (Refereed)
    Abstract [en]

    Software architecture is no more a mere system specification as resulting from the design phase, but it includes the process by which its specification was carried out. In this respect, design decisions in component-based software engineering play an important role: they are used to enhance the quality of the system, keep the current market level, keep partnership relationships, reduce costs, and so forth. For non trivial systems, a recurring situation is the selection of an asset origin, that is if going for in-house, outsourcing, open-source, or COTS, when in the need of a certain missing functionality. Usually, the decision making process follows a case-by-case approach, in which historical information is largely neglected: hence, it is avoided the overhead of keeping detailed documentation about past decisions, but it is hampered consistency among multiple, possibly related, decisions. The ORION project aims at developing a decision support framework in which historical decision information plays a pivotal role: it is used to analyse current decision scenarios, take well-founded decisions, and store the collected data for future exploitation. In this paper, we outline the potentials of such a knowledge repository, including the information it is intended to be stored in it, and when and how to retrieve it within a decision case.

  • 283.
    Clark, David
    et al.
    UCL, GBR.
    Feldt, Robert
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Poulding, Simon
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Yoo, Shin
    UCL, GBR.
    Information Transformation: An Underpinning Theory for Software Engineering2015In: 2015 IEEE/ACM 37th IEEE International Conference on Software Engineering, Vol 2, IEEE , 2015, p. 599-602Conference paper (Refereed)
    Abstract [en]

    Software engineering lacks underpinning scientific theories both for the software it produces and the processes by which it does so. We propose that an approach based on information theory can provide such a theory, or rather many theories. We envision that such a benefit will be realised primarily through research based on the quantification of information involved and a mathematical study of the limiting laws that arise. However, we also argue that less formal but more qualitative uses for information theory will be useful. The main argument in support of our vision is based on the fact that both a program and an engineering process to develop such a program are fundamentally processes that transform information. To illustrate our argument we focus on software testing and develop an initial theory in which a test suite is input/output adequate if it achieves the channel capacity of the program as measured by the mutual information between its inputs and its outputs. We outline a number of problems, metrics and concrete strategies for improving software engineering, based on information theoretical analyses. We find it likely that similar analyses and subsequent future research to detail them would be generally fruitful for software engineering.

  • 284.
    Clementson, Martin
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Augustsson, John
    User Study of Quantized MIP Level Data In Normal Mapping Techniques2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

     The standard MIP mapping technique halves the resolution of textures for each level of the MIP chain. In this thesis the bits per pixel(bpp) is reduced as well. Normal maps are generally used with MIP maps, and todays industry standard for these are usually 24 bpp.The reduction is simulated as there is currently no support for the lower bpp in GPU hardware.

    Objectives: To render images of normal mapped objects with decreasing bpp for each level in a MIP chain and evaluate these against the standard MIP mapping technique using a subjective user study and an objective image comparison method.

    Methods: A custom software is implemented to render the images with quantized normal maps manually placed in a MIP chain. For the subjective experiment a 2AFC test is used, and the objective part consists of a PDIFF test for the images.

    Results: The results indicate that as the MIP level is increased and the bpp is lowered, users can increasingly see a difference.

    Conclusions: The results show that participants can see a difference as the bpp is reduced, which indicates normal mapping as not suitable for this method, however further study is required before this technique can be dismissed as an applicable method

  • 285.
    Cosic Prica, Srdjan
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Video Games and Software Engineers: Designing a study based on the benefits from Video Games and how they can improve Software Engineers2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Context: This is a study about investigating if playing video games can improve any skills and characteristics in a software engineer. Due to lack of resources and time, this study will focus on designing a study that others may use to measure the results and if video games actually can improve software engineers.

    Objectives: The main objectives are finding the benefits of playing video games and how those benefits are discovered. Meaning what types of games and for how long someone needs to play in order to be affected and show improvements. Another objective is to find out what skills are requested and required in a software engineer. Then it is time to design the study based on the information gathered.

    Methods: There is a lot of literature studying involved. The method is parallel research which is when reading about the benefits of playing video games, then also reading and trying to find corresponding benefits in what is requested and required in software engineers.

    Results: There are many cognitive benefits from video games that are also beneficial in software engineers. There is no recorded limit to how long a study can go on playing video games that it proves to have negative consequences. That means that the study designed from the information gathered is very customizable and there are many results that can be measured.

    Conclusions: There is a very high chance that playing video games can result in better software engineers because the benefits that games provide are connected to skills requested and required by employers and other expert software engineers that have been in the business for a long time and have a high responsibilities over other teams of software engineers.

  • 286. Cousin, Philippe
    et al.
    Fricker, Samuel
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Felmy, Dean
    Le Gall, Franck
    Fiedler, Markus
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Validation and Quality in FI-PPP e-Health Use Case, FI-STAR Project2014Conference paper (Refereed)
  • 287.
    Cuenca, Juan
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    What are the affordances fostered by social media for amateurs artists?2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The research engages the use of social media sites for musicians with a focus on Facebook. It determines which are the advantages the platform makes available for musicians, allowing them to employ Do It Yourself strategies of production, audience relationship management and self-management. The importance of audience response and demographics allow any musician integrate keen insight into the content delivery and thus, optimize their management accordingly. This thesis will establish the affordances that engage what aspects and uses of Facebook are changing the way amateurs operate. The research appropriates the context of professionalism to the variable of knowledgeability, know-how, and Stebbins’ (1977) seven variables (confidence, perseverance, continuation commitment, preparedness and self-conception) in order to note a definition of the modern amateur in contrast to professionals.

  • 288.
    Cynthia, Salkovic
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    Esoko and WhatsApp Communication in Ghana: Mobile Services such as Esoko and WhatsApp in Reshaping Interpersonal Digital Media Communication in Ghana2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The predominant use of mobile media such as SMS and MIM across various sectors in Ghana is incontrovertibly influencing and reshaping interpersonal communications. This paper looked at the use of the Esoko SMS and WhatsApp MIM platforms and how the use of these two dominant platforms are enhancing and reshaping digital communication in the rural and urban Ghana respectively, as barriers of socioeconomic factors limits the use of sophisticated technologies in the rural setting. This is done by employing Madianou and Miller's notion of polymedia” to draw on the moral, social and the emotional use of mobile media in enacting interpersonal relationships and communications whilst keeping in focus the recursive repercussions.

  • 289.
    Dagala, Wadzani Jabani
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Analysis of Total Cost of Ownership for Medium Scale Cloud Service Provider with emphasis on Technology and Security2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Total cost of ownership is a great factor to consider when deciding to deploy cloud computing. The cost to own a data centre or run a data centre outweighs the thought of IT manager or owner of the business organisation.The research work is concerned with specifying the factors that sum the TCO for medium scale service providers with respect to technology and security. A valid analysis was made with respect to the cloud service providers expenses and how to reduce the cost of ownership.In this research work, a review of related articles was used from a wide source, reading through the abstract and overview of the articles to find its relevance to the subject. A further interview was conducted with two medium scale cloud service providers and one cloud user.In this study, an average calculation of the TCO was made and we implemented a proposed cost reduction method. We made a proposal on which and how to decide as to which cloud services users should deploy in terms of cost and security.We conclude that many articles have focused their TCO calculation on the building without making emphasis on the security. The security accumulates huge amount under hidden cost and this research work identified the hidden cost, made an average calculation and proffer a method of reducing the TCO.

  • 290.
    Damm, Johan
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    Lindgren, Alexander
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    Rockman, Carl
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    Afrika, webben och den digitala skiljelinjen2014Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [en]

    Uppsatsen beskriver en undersökning och produktion kring att utveckla en anpassad webbapplikation som kan trotsa fenomenet av den digitala skiljelinjen.

  • 291.
    Daniel, Emil
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    John, Johansson
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    Hjälte vs Skurk: ”I rymden kan ingen höra dig skrika yippee-ki-yay motherfucker”2016Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Meetings between people can be exciting and make you discover something new, also in movies. Meetings between the characters drives the plot forward, and create exciting interaction between the characters. We have chosen to focus on meetings between the hero and the villain, two strong and important character roles in the film. The character roles are taken from Vogler, The Writer's Journey (1997). To get a broader picture of how roles may appear in film, we have chosen to analyze two different films in different genres, the films we have chosen are Die Hard (1988) and Alien (1979). We have used the analytical model presented in From Antz to Titanic - A student's guide to film analysis (2000) and formed the model to our fitting. One of the parts of the analysis focuses on the technical aspects of the scenes that can help move the story forward. Based on our survey of character roles and meetings between them, we have created a movie to portray this.

  • 292.
    Danielsson, Max
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    Grahn, Håkan
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Sievert, Thomas
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Rasmusson, Jim
    Sony Mobile Communications AB, SWE.
    Comparing Two Generations of Embedded GPUs Running a Feature Detection AlgorithmManuscript (preprint) (Other academic)
    Abstract [en]

    Graphics processing units (GPUs) in embedded mobile platforms are reaching performance levels where they may be useful for computer vision applications. We compare two generations of embedded GPUs for mobile devices when run- ning a state-of-the-art feature detection algorithm, i.e., Harris- Hessian/FREAK. We compare architectural differences, execu- tion time, temperature, and frequency on Sony Xperia Z3 and Sony Xperia XZ mobile devices. Our results indicate that the performance soon is sufficient for real-time feature detection, the GPUs have no temperature problems, and support for large work-groups is important.

  • 293.
    Danielsson, Max
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies. Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Sievert, Thomas
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies. Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Viability of Feature Detection on Sony Xperia Z3 using OpenCL2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Context. Embedded platforms GPUs are reaching a level of perfor-mance comparable to desktop hardware. Therefore it becomes inter-esting to apply Computer Vision techniques to modern smartphones.The platform holds different challenges, as energy use and heat gen-eration can be an issue depending on load distribution on the device.

    Objectives. We evaluate the viability of a feature detector and de-scriptor on the Xperia Z3. Specifically we evaluate the the pair basedon real-time execution, heat generation and performance.

    Methods. We implement the feature detection and feature descrip-tor pair Harris-Hessian/FREAK for GPU execution using OpenCL,focusing on embedded platforms. We then study the heat generationof the application, its execution time and compare our method to twoother methods, FAST/BRISK and ORB, to evaluate the vision per-formance.

    Results. Execution time data for the Xperia Z3 and desktop GeForceGTX660 is presented. Run time temperature values for a run ofnearly an hour are presented with correlating CPU and GPU ac-tivity. Images containing comparison data for BRISK, ORB andHarris-Hessian/FREAK is shown with performance data and discus-sion around notable aspects.

    Conclusion. Execution times on Xperia Z3 is deemed insufficientfor real-time applications while desktop execution shows that there isfuture potential. Heat generation is not a problem for the implemen-tation. Implementation improvements are discussed to great lengthfor future work. Performance comparisons of Harris-Hessian/FREAKsuggest that the solution is very vulnerable to rotation, but superiorin scale variant images. Generally appears suitable for near duplicatecomparisons, delivering much greater number of keypoints. Finally,insight to OpenCL application development on Android is given

  • 294. Danielsson, Max
    et al.
    Sievert, Thomas
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Grahn, Håkan
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Rasmusson, Jim
    Sony Mobile Communications AB.
    Feature Detection and Description using a Harris-Hessian/FREAK Combination on an Embedded GPU2016Conference paper (Refereed)
    Abstract [en]

    GPUs in embedded platforms are reaching performance levels comparable to desktop hardware, thus it becomes interesting to apply Computer Vision techniques. We propose, implement, and evaluate a novel feature detector and descriptor combination, i.e., we combine the Harris-Hessian detector with the FREAK binary descriptor. The implementation is done in OpenCL, and we evaluate the execution time and classification performance. We compare our approach with two other methods, FAST/BRISK and ORB. Performance data is presented for the mobile device Xperia Z3 and the desktop Nvidia GTX 660. Our results indicate that the execution times on the Xperia Z3 are insufficient for real-time applications while desktop execution shows future potential. Classification performance of Harris-Hessian/FREAK indicates that the solution is sensitive to rotation, but superior in scale variant images.

  • 295.
    Dantuluri, Kishore Varma
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Impact of Virtualization on Timestamp Accuracy2015Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The ever-increasing demand for high quality services require a good quantification of performance parameters such as delay and jitter. Let’s consider one of the parameters, jitter, which is the difference between the inter arrival time of two subsequent packets and the average inter-arrival time. The arrival or departure time of a packet is termed as time-stamp. The accuracy of the timestamp will influence any performance metrics based on the arrival/departure time of a packet. Hence, the knowledge or awareness of time-stamping accuracy is important for performance evaluation. This study investigates how the time-stamping process is affected by virtualization

  • 296.
    Darisipudi, Veeravenkata Naga S Maniteja
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Sustainable Throughput – QoE Perspective2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In recent years, there has been a significant increase in the demand for streaming of high quality videos on the smart mobile phones. In order to meet the user quality requirements, it is important to maintain the end user quality while taking the resource consumption into consideration. This demand caught the attention of the research communities and network providers to prioritize Quality of Experience (QoE) in addition to the Quality of Service (QoS). In order to meet the users’ expectations, the QoE studies have gained utmost importance, thus creating the challenge of evaluating it in such a way that the quality, cost and energy consumption are taken into account. This gave way to the concept of QoE-aware sustainable throughput, which denotes the maximal throughput at which QoE problems can be still kept at a desired level.

    The aim of the thesis is to determine the sustainable throughput values from the QoE perspective. The values are observed for different delay and packet loss values in wireless and mobile scenarios. The evaluation is done using the subjective video quality assessment method.

    In the subjective assessment method, the evaluation is done using the ITU-T recommended Absolute Category Rating (ACR). The video quality ratings are taken from the users, and are then averaged to obtain the Mean Opinion Score (MOS). The obtained scores are used for analysis in determining the sustainable throughput values from the users’ perspective.

    From the results it is determined that, for all the video test cases, the videos are rated better quality at low packet loss values and low delay values. The quality of the videos with the presence of delay is rated high compared to the video quality in the case of packet loss. It was observed that the high resolution videos are feeble in the presence of higher disturbances i.e. high packet loss and larger delays. From considering all the cases, it can be observed that the QoE disturbances due to the delivery issues is at an acceptable minimum for the 360px video. Hence, the 480x360 video is the threshold to sustain the video quality.

  • 297.
    Dasari, Siva Krishna
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Lavesson, Niklas
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Andersson, Petter
    Engineering Method Development, GKN Aerospace Engine Systems Sweden.
    Persson, Marie
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Tree-Based Response Surface Analysis2015Conference paper (Refereed)
    Abstract [en]

    Computer-simulated experiments have become a cost effective way for engineers to replace real experiments in the area of product development. However, one single computer-simulated experiment can still take a significant amount of time. Hence, in order to minimize the amount of simulations needed to investigate a certain design space, different approaches within the design of experiments area are used. One of the used approaches is to minimize the time consumption and simulations for design space exploration through response surface modeling. The traditional methods used for this purpose are linear regression, quadratic curve fitting and support vector machines. This paper analyses and compares the performance of four machine learning methods for the regression problem of response surface modeling. The four methods are linear regression, support vector machines, M5P and random forests. Experiments are conducted to compare the performance of tree models (M5P and random forests) with the performance of non-tree models (support vector machines and linear regression) on data that is typical for concept evaluation within the aerospace industry. The main finding is that comprehensible models (the tree models) perform at least as well as or better than traditional black-box models (the non-tree models). The first observation of this study is that engineers understand the functional behavior, and the relationship between inputs and outputs, for the concept selection tasks by using comprehensible models. The second observation is that engineers can also increase their knowledge about design concepts, and they can reduce the time for planning and conducting future experiments.

  • 298.
    Davidsson, Paul
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Holmgren, Johan
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Persson, Jan A.
    Ramstedt, Linda
    Multi Agent Based Simulation of Transport Chains2008Conference paper (Refereed)
    Abstract [en]

    An agent-based tool for micro-level simulation of transport chains (TAPAS) is described. It is more powerful than traditional approaches as it is able to capture the interactions between individual actors of a transport chain, as well as their heterogeneity and decision making processes. Whereas traditional approaches rely on assumed statistical correlation between different parameters, TAPAS relies on causality, i.e., the decisions and negotiations that lead to the transports being performed. An additional advantage is that TAPAS is able to capture time aspects, such as, the influence of timetables, arrival times, and time-differentiated taxes and fees. TAPAS is composed of two layers, one layer simulating the physical activities taking place in the transport chain, e.g., production, storage, and transports of goods, and another layer simulating the different actors’ decision making processes and interaction. The decision layer is implemented as a multi-agent system using the JADE platform, where each agent corresponds to a particular actor. We demonstrate the use of TAPAS by investigating how the actors in a transport chain are expected to act when different types of governmental control policies are applied, such as, fuel taxes, road tolls, and vehicle taxes. By analyzing the costs and environmental effects, TAPAS provides guidance in decision making regarding such control policies. We argue that TAPAS may also complement existing approaches in different ways, for instance by generating input data such as transport demand. Since TAPAS models a larger part of the supply chain, the transport demand is a natural part of the output. Studies may concern operational decisions like choice of consignment size and frequency of deliveries, as well as strategic decisions like where to locate storages, terminals, etc., choice of producer, and adaptation of vehicle fleets.

  • 299.
    de Carvalho, Renata M.
    et al.
    Univ Quebec, LATECE Lab, Montreal, PQ, Canada..
    Mili, Hafedh
    Univ Quebec, LATECE Lab, Montreal, PQ, Canada..
    Boubaker, Anis
    Univ Quebec, LATECE Lab, Montreal, PQ, Canada..
    Gonzalez-Huerta, Javier
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Ringuette, Simon
    Trisotech Inc, Montreal, PQ, Canada..
    On the analysis of CMMN expressiveness: revisiting workflow patterns2016In: 2016 IEEE 20TH INTERNATIONAL ENTERPRISE DISTRIBUTED OBJECT COMPUTING WORKSHOP (EDOCW), 2016, p. 54-61Conference paper (Refereed)
    Abstract [en]

    Traditional business process modeling languages use an imperative style to specify all possible execution flows, leaving little flexibility to process operators. Such languages are appropriate for low-complexity, high-volume, mostly automated processes. However, they are inadequate for case management, which involves low-volume, high-complexity, knowledge-intensive work processes of today's knowledge workers. OMG's Case Management Model and Notation (CMMN), which uses a declarative style to specify constraints placed at a process execution, aims at addressing this need. To the extent that typical case management situations do include at least some measure of imperative control, it is legitimate to ask whether an analyst working exclusively in CMMN can comfortably model the range of behaviors s/he is likely to encounter. This paper aims at answering this question by trying to express the extensive collection of Workflow Patterns in CMMN. Unsurprisingly, our study shows that the workflow patterns fall into three categories: 1) the ones that are handled by CMMN basic constructs, 2) those that rely on CMMN's engine capabilities and 3) the ones that cannot be handled by current CMMN specification. A CMMN tool builder can propose patterns of the second category as companion modeling idioms, which can be translated behind the scenes into standard CMMN. The third category is problematic, however, since its support in CMMN tools will break model interoperability.

  • 300.
    de la Vara, Jose Luis
    et al.
    Carlos III University of Madrid, ESP.
    Borg, Markus
    SICS Swedish ICT AB, SWE.
    Wnuk, Krzysztof
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Moonen, Leon
    Certus Centre for S oftware V&V, NOR.
    An Industrial Survey of Safety Evidence Change Impact Analysis Practice2016In: IEEE Transactions on Software Engineering, ISSN 0098-5589, E-ISSN 1939-3520, Vol. 42, no 12, p. 1095-1117Article in journal (Refereed)
    Abstract [en]

    Context. In many application domains, critical systems must comply with safety standards. This involves gathering safety evidence in the form of artefacts such as safety analyses, system specifications, and testing results. These artefacts can evolve during a system's lifecycle, creating a need for change impact analysis to guarantee that system safety and compliance are not jeopardised. Objective. We aim to provide new insights into how safety evidence change impact analysis is addressed in practice. The knowledge about this activity is limited despite the extensive research that has been conducted on change impact analysis and on safety evidence management. Method. We conducted an industrial survey on the circumstances under which safety evidence change impact analysis is addressed, the tool support used, and the challenges faced. Results. We obtained 97 valid responses representing 16 application domains, 28 countries, and 47 safety standards. The respondents had most often performed safety evidence change impact analysis during system development, from system specifications, and fully manually. No commercial change impact analysis tool was reported as used for all artefact types and insufficient tool support was the most frequent challenge. Conclusion. The results suggest that the different artefact types used as safety evidence co-evolve. In addition, the evolution of safety cases should probably be better managed, the level of automation in safety evidence change impact analysis is low, and the state of the practice can benefit from over 20 improvement areas.

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