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  • 2501.
    Christensen, Tina
    et al.
    Blekinge Institute of Technology, School of Management.
    Stankus, Linda
    Blekinge Institute of Technology, School of Management.
    Preferences in e-Commerce Among Men, Women, and Mothers of Young Children in the US2008Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    The purpose of our research is to examine differences in e-commerce preferences between men, women, and mothers with small children (in the US). Various website factors have been established in previous studies as critical to e-commerce success. However, there are few studies that investigate how these factors vary in importance among different user groups, for example men, women, or mothers with young children. Increased understanding of these group’s preferences can help companies market themselves more effectively to these groups. A survey was distributed to residents of the US, asking respondents to rank the relative importance of 16 e-commerce features, as well as to provide performance ratings for the implementation of these features by their favorite Internet retailer. The data collected from this survey was analyzed to evaluate significant group differences in their prioritization of importance, as well as perceived performance, of the features and of three constructs (information quality, system quality, and customer-relations quality), which corresponded to more general characteristic groupings of these features. These measures were used to help identify potential performance gaps, which might serve as opportunities for companies to better meet the e-retail expectations of different customer groups. Differences in the importance of features and constructs within each of the groups were consistent with previous studies. A number of gender differences were found in the relative importance of various features, but no gender differences were found at the more general construct level. There were no significant differences in importance values between mothers and non-mothers at either the feature or construct level. However, numerous differences between the groups were found in performance ratings at both feature and construct levels. Most significant was the lower level of satisfaction among mothers, for all features and constructs. Because of a high proportion of respondents listing Amazon.com as favorite e-retailer, separate analyses were performed of these respondents and of the other “non-Amazon” respondents. These analyses showed even greater dissatisfaction among the non-Amazon mothers. In fact, Amazon performance ratings were higher than those of the non-Amazon companies for all constructs and groups, except that IQ performance for women, and especially for non-mothers, was relatively low and of possible concern.

  • 2502.
    Christensson, Ylva
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Wickström, Emelie
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Upplevelsen av återhämtning efter en kranskärlsoperation: En litteraturstudie2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Bakgrund: Hjärt-kärlsjukdom är globalt sett, den dominerande orsaken till mortalitet. Tack vare de allt mer utvecklade behandlingsmetoderna, är det idag fler som överlever. En av dessa behandlingsmetoder är kranskärlsoperation, vilken är nödvändig vid förekomst av komplicerad kranskärlssjukdom. Det är en omfattande operation som kan resultera i såväl fysiska som psykiska konsekvenser för en individ. För att sjuksköterskan ska förstå individens upplevelse av återhämtningsprocessen, krävs god kunskap om operationens innebörd och likaså förståelse för vilka faktorer som spelar in under återhämtningsprocessen.

    Syfte: Syftet med denna studie var, att beskriva individers upplevelse av återhämtning efter en kranskärlsoperation.

    Metod: För att besvara studiens syfte, har en litteraturstudie med kvalitativ design använts. Studien är baserad på 13 vetenskapliga artiklar, som har sökts fram i databaserna Cinahl och PubMed. Artiklarna analyserades utifrån Graneheim och Lundmans tolkning av kvalitativ innehållsanalys. 

    Resultat: Resultatet visade att olika upplevelser under återhämtningsprocessen kan påverka individerna. Ur analysen framkom tre kategorier som visade hur återhämtningsprocessen kunde upplevas. Dessa var begränsningar i vardagen, behovet av stöd och tillbaka till livet.

    Slutsats: Efter en kranskärlsoperation är det många faktorer som påverkar en individs upplevelse av återhämtningsprocessen. Genom en god förståelse av individens situation, tydlig information och praktisk vägledning, kan sjuksköterskan bidra till en gynnsam återhämtningsprocess i individens vardag.  

  • 2503.
    Christiansen, Line
    Blekinge Institute of Technology, Faculty of Health Sciences, Department of Health.
    SJUKSKÖTERSKORS ANVÄNDNING AV IKT I PRIMÄRVÅRDEN: - EN ENKÄTSTUDIE2015Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Background: Deficits in communication and information transfer between carelevels at hospital discharge are common and can lead to unnecessary readmissions. There is a great potential of using ICT in health care since it could facilitate faster information transfer between care levels and make the information more consistent and available for follow-up care. However there is still a lacking of knowledge in how much nurses use ICT and the factors that influence its use. Aim: The aim of the study was to describe factors influencing nurses' use of ICT system Prator in primary care and if the use can be related to the perception that ICT contributes to improved coordination in discharges from hospital. Method: A quantitative survey with thirty-seven nurses from eleven medical centers in Southern Sweden who describes their use of the ICT system Prator. Data were statistically analyzed with a descriptive and comparative approach. Results: The results show a significant difference in attitudes between nurses who use Prator and those who did not. Furthermore it shows that only half of the nurses in this study received education about Prator during the implementation. A statistically proven significant were also found in perceptions of using the system. Conclusion: Nurses who use Prator are more positive to the usability of the system and its potential to improve coordination at discharges than those nurses who did not use it. It can therefore be assumed that nurses need to work with the system to be positive about it and see the benefits of it.

  • 2504.
    Christiansen, Line
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Fagerstrom, Cecilia
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Nilsson, Lina
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Nurses' Use and Perception of an Information and Communication Technology System for Improving Coordination During Hospital Discharges A Survey in Swedish Primary Healthcare2017In: Computers, Informatics, Nursing, ISSN 1538-2931, E-ISSN 1538-9774, Vol. 35, no 7, p. 358-363Article in journal (Refereed)
    Abstract [en]

    To facilitate communications between care levels and improve coordination during hospital discharges, there is great potential in using information and communication technology systems, because they can significantly help to deter unnecessary readmissions. However, there is still a lack of knowledge about how often nurses use information and communication technology and the indicators related to its use. The aims of this study were to describe the indicators related to nurses' use of an information and communication technology system for collaboration between care levels and to estimate whether the level of use can be related to nurses' perceptions of the information and communication technology system's contribution to improve coordination during hospital discharges. A quantitative survey of 37 nurses from 11 primary healthcare centers was performed in a county in southern Sweden. The data were analyzed using descriptive and comparative analyses. The results showed that perceptions concerning the information and communication technology system's usability and time consumption differed between nurses who used the system and those who did not. Simultaneously, the nurses were rather unaware of the ability of the information and communication technology system to improve coordination during patient discharges.

  • 2505.
    Christiansen, Line
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Sanmartin Berglund, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Lindberg, Catharina
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Anderberg, Peter
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Skär, Lisa
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Health-related quality of life and related factors among a sample of older people with cognitive impairment2019In: Nursing Open, E-ISSN 2054-1058, Vol. 6, no 3, p. 849-859Article in journal (Refereed)
    Abstract [en]

    Aim: This study aimed to identify factors affecting health-related quality of life (HRQoL) of older adults with cognitive impairment and to describe the association of these factors with different components of HRQoL. Design: A cross-sectional, descriptive research design was used. Methods: Data were collected from 247 individuals aged 60 years and older from a Swedish longitudinal cohort study. The Short-Form Health Survey-12 (SF-12) and EuroQol (EQ-5D) were used to assess HRQoL. The data were analysed using descriptive and comparative statistics. Results: The present study identified several factors that influenced HRQoL of older adults with cognitive impairment. The results of a multiple logistic regression analysis revealed that the following factors were associated with physical and mental HRQoL: dependency in activities of daily living (ADL), receiving informal care and feelings of loneliness and pain. © 2019 The Authors. Nursing Open published by John Wiley & Sons Ltd.

  • 2506.
    Christiansson, Karin
    et al.
    Blekinge Institute of Technology, School of Health Science.
    Fraude, Marie
    Blekinge Institute of Technology, School of Health Science.
    Ätstörning -”en levande mardröm”- Familjens upplevelser2008Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Bakgrund: Ätstörning bland tonåringar har uppmärksammats allt mer under de senaste decennierna, parallellt med att kunskapen om sjukdomen har ökat. Eftersom sjukdomen drabbar hela familjen är det viktigt att även lägga fokus på familjens upplevelser. Syfte: Studiens syfte var att beskriva familjens upplevelser kring att leva med en tonåring som drabbats av ätstörning. Metod: Metoden som användes var en litteraturstudie, sju vetenskapliga artiklar granskades. Med hjälp av Graneheim & Lundmans analysmetod gjordes en innehållsanalys. Resultat: Resultatet visar att föräldrar till tonåringar med ätstörning upplever stor frustration och maktlöshet i den rådande situationen. Som exempel uttrycker en mamma, att leva med en tonåring med ätstörning är som ”en levande mardröm”. Föräldrarna upplever en känsla av ett splittrat familjeliv samt att syskonen påverkas negativt. Det visar sig att många föräldrar upplever att sjukdomen ”tar över” deras dotter. Föräldrarna är i behov av hjälp, stöd och kunskap om sjukdomen och dess förlopp. Slutsats: Genom att ta del av föräldrarnas upplevelser bidrar detta till en ökad kunskap hos vårdpersonalen, vilket leder till ett mer professionellt och stödjande bemötande.

  • 2507.
    Chrysanthakis, Spyros
    et al.
    Blekinge Institute of Technology, School of Management.
    Morthala, Nancy
    Blekinge Institute of Technology, School of Management.
    Zamani, Tatjana
    Blekinge Institute of Technology, School of Management.
    Valuation of Securities on Inactive Markets2013Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    Background: The main topic of the master thesis is Valuation of Securities on Inactive Markets. Securities quoted on inactive market have been investigated to present how their fair value can be efficiently measured. Securities quoted on inactive market can have limited or unreliable inputs and the valuation process can become time and money consuming. Financial professional face similar problems while valuing financial assets on inactive markets. Relevance of the topic: The master thesis might be of particular interest to investment and asset management companies which can get an opportunity to share their experiences and gain from the knowledge exchange. Method: One asset management company and three audit companies have been contacted for collecting information from different perspectives. asset management company has practical experience on conducting valuation of inactively traded securities and audit companies suggest how valuation should be done. Results have been collected through surveys and interviews to all selected companies. Then the qualitative approach has been applied on the collected results. Main findings: Even though most of the answers to the questionnaire were different, as the companies followed generally accepted international standards, their view on the valuation of inactively traded securities was relatively common. Companies admitted that the main problems in the valuation of securities quoted on inactive market are the limited access to market quotes, high spreads on the market, unreliable market information, limited access to financial data of the valued companies and considerable amount of inactively traded securities. Valuation based on multiples is most commonly used by the companies. Sometimes the combination of methods for example price of recent transaction, DCF and net assets can be applied and it is up to the investment manager to decide what methods to use. Summary of recommendations offered by the interviewed companies concerning valuation of inactively traded securities is presented at the end of the master thesis.

  • 2508.
    Chtivelband, Igor
    Blekinge Institute of Technology, School of Computing.
    HistoryLane: Web Browser History Visualization Method2012Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    With the evolution of Internet, users exploit it increasingly intensively for achieving their goals: sending emails, playing games, watching videos, reading news. They do it through Web browsers, that may vary in exact implementation, but have similar core functionalities . One of these core functionalities is the access to a browsing history. However, as browsing patterns are getting more complex, the traditional history tools become insufficient. Visualization of browsing history might be helpful in that case. In this study we propose a novel approach for browsing history visualization, named HistoryLane, which ts the parallel browsing paradigm, common for modern browsers. The main goal of HistoryLane is enabling the user to gain insight into his own or into other users' parallel browsing patterns over time. Principles of HistoryLane visualization approach are formulated based on recommendations, found during structured literature review. These principles constitute the base for a prototype, which was implemented as a Fire- fox extension. To evaluate the e ffectiveness of HistoryLane we conducted a survey and a quantitative experiment. The results of the evaluation show that HistoryLane is perceived by users as effective and intuitive method for browsing history visualization.

  • 2509.
    Chu, Thi My Chin
    et al.
    Blekinge Institute of Technology, School of Computing.
    Phan, Hoc
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    MIMO Incremental AF Relay Networks with TAS/MRC and Adaptive Modulation2013Conference paper (Other academic)
    Abstract [en]

    In this paper, we study the use of adaptive modulation (AM) for a dual-hop multiple-input multiple-output (MIMO) network with transmit antenna selection (TAS) at the transmitter and maximal ratio combining (MRC) at the receiver. Our system deploys incremental amplify-and-forward (AF) relaying with AM to forward the source signal. A switching policy for selecting between the relaying and the direct communication is utilized to maximize spectrum efficiency. In particular, we derive closed-form expressions for the outage probability, spectrum efficiency, and bit error rate (BER) for the considered system over Nakagami-m fading. The considered network not only takes advantage of TAS transmission such as achieving full diversity order with low transmit complexity but also inherits the beneficial feature of AM such as spectrum efficiency improvement. Reference

  • 2510.
    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.

  • 2511.
    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.

  • 2512. Chu, Thi My Chinh
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    MRT/MRC for Cognitive AF Relay Networks under Feedback Delay and Channel Estimation Error2012Conference paper (Refereed)
    Abstract [en]

    In this paper, we examine the performance of multiple-input multiple-output cognitive amplify-and-forward (AF) relay systems with maximum ratio transmission (MRT). In particular, closed-form expressions in terms of a tight upper bound for outage probability (OP) and symbol error rate (SER) of the system are derived when considering channel estimation error (CEE) and feedback delay (FD) in our analysis. Through our works, one can see the impact of FD and CEE on the system as well as the benefits of deploying multiple antennas at the transceivers utilizing the spatial diversity of an MRT system.

  • 2513. Chu, Thi My Chinh
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Outage Probability and Ergodic Capacity for MIMO-MRT Systems under Co-Channel Interference and Imperfect CSI2011Conference paper (Refereed)
    Abstract [en]

    In this paper, we investigate the performance of multiple-input multiple-output (MIMO) systems deploying maximum ratio transmission (MRT). Our analysis takes into account not only imperfect channel estimation at the receiver and feedback delay at the transmitter, but also includes co-channel interference (CCI). In particular, we first derive the statistical properties of the signal-to-interference-plus-noise ratio (SINR). Next, we obtain a closed-form expression for outage probability and an approximation for capacity. Finally, we show the consistency between analytical results and Monte-Carlo simulations. Our results indicate that the system performance is improved considerably in proportion to the number of transceiver antennas. Conversely, the outage probability increases, and the capacity decreases significantly with the severity of channel estimation error, feedback delay, and CCIs.

  • 2514.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, School of Computing.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Performance analysis for multiple-input multiple output- maximum ratio transmission systems with channel estimation error, feedback delay and co-channel interference2013In: IET Communications, ISSN 1751-8628, Vol. 7, no 4, p. 279-285Article in journal (Refereed)
    Abstract [en]

    In this study, the authors analyse the impact of channel estimation error (CEE), feedback delay (FD), and co-channel interference (CCI) on the performance of multiple-input multiple-output (MIMO) systems deploying maximum ratio transmission (MRT). In particular, the authors derive closed-form expressions for the ergodic capacity and the symbol error rate (SER) as well as the outage probability (OP). In addition, to reveal the effect of CEE, FD and CCI on the MIMO-MRT system, the authors adopt more simplified and tractable formulas in terms of asymptotic expressions for the ergodic capacity, SER and OP. The analysis shows that the system performance is degraded considerably under imperfect transmission conditions such as CEE, FD and CCI. However, the authors can compensate part of this degradation by deploying MRT transmission with a large number of antennas at the transmitter and receiver. Finally, the selected examples exhibit consistency between analytical results and Monte Carlo simulations.

  • 2515.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, School of Computing.
    Phan, Hoc
    Blekinge Institute of Technology, School of Computing.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Elkashlan, Maged
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Beamforming Transmission in Cognitive AF Relay Networks with Feedback Delay2013Conference paper (Refereed)
    Abstract [en]

    In this paper, we investigate the effect of feedback delay on outage probability (OP) and symbol error rate (SER) of cognitive amplify-and-forward (AF) relay networks with beamforming transmission in Rayleigh fading environment. It is assumed that the secondary transmitter and the secondary receiver are equipped with multiple antennas, whereas the relay and the primary user comprise of a single antenna. Furthermore, in this system, the secondary users use the underlay scheme in which the secondary transmitter and the relay can coexist with the primary user as long as their interference caused to the primary receiver is below a predefined threshold. Through our analysis, numerical results are provided to show the level of degradation of cognitive AF relay systems in proportion to the degree of feedback delay. In addition, we also present the effect of the number of antennas at the secondary transceiver on the performance of the considered system.

  • 2516.
    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.

  • 2517.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, School of Computing.
    Phan, Hoc
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Amplify-and-Forward Relay Assisting both Primary and Secondary Transmissions in Cognitive Radio Networks over Nakagami-m Fading2012Conference paper (Refereed)
    Abstract [en]

    In this paper, we study the performance for the primary and secondary transmissions in cognitive radio networks where the amplify-and-forward (AF) secondary relay helps to transmit the signals for both the primary and secondary transmitters over independent Nakagami-m fading. First, we derive exact closed-form expressions for outage probability and symbol error rate (SER) of the primary network. Then, we derive an exact closed-form expression for outage probability and a closed-form expression of a tight upper bound for SER of the secondary network. Furthermore, we also make a comparison for the performance of the primary system with and without the help of the secondary relay.

  • 2518.
    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.

  • 2519.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, School of Computing.
    Phan, Hoc
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Cognitive MIMO AF Relay Network with TAS/MRC Under Peak Interference Power Constraint2013Conference paper (Refereed)
    Abstract [en]

    In this paper, we study the use of transmit antenna selection (TAS) and maximal ratio combining (MRC) for a cognitive multiple-input multiple-output (MIMO) amplify-andforward (AF) relay network. We focus on the scenario that each of the source and relay selects only a single antenna which maximizes the instantaneous signal-to-noise ratio (SNR) to transmit and forward the signal while the receiver combines the signals from all receive antennas. Utilizing TAS, the considered cognitive network not only offers advantages such as achieving full diversity order with low transmit complexity but also reduces the interference induced to the primary transmission as compared to maximum ratio transmission (MRT). This in turn becomes beneficial for the secondary network when this network operates under the interference power constraint of the primary receiver. In particular, we derive expressions for the outage probability and symbol error rate (SER) of the network to evaluate the system performance. We also develop an asymptotic analysis for the outage probability and the SER to obtain diversity and coding gain. With the tractable asymptotic expressions, the effect of network parameters such as the number of antennas, the transmission distances, and the interference power constraint of the primary receiver on the system performance are readily revealed.

  • 2520.
    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.

  • 2521.
    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.

  • 2522.
    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.

  • 2523.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, School of Computing.
    Phan, Hoc
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    MIMO Incremental AF Relay Networks with TAS/MRC and Adaptive Modulation2013Conference paper (Refereed)
    Abstract [en]

    In this paper, we study the use of adaptive modulation (AM) for a dual-hop multiple-input multiple-output (MIMO) network with transmit antenna selection (TAS) at the transmitter and maximal ratio combining (MRC) at the receiver. Our system deploys incremental amplify-and-forward (AF) relaying with AM to forward the source signal. A switching policy for selecting between the relaying and the direct communications is utilized to maximize spectrum efficiency. In particular, we derive expressions for the outage probability, spectrum efficiency, and bit error rate (BER) for the considered system over Nakagamim fading. The considered network not only takes advantage of TAS transmission such as achieving full diversity order with low transmit complexity but also inherits the beneficial feature of AM such as spectrum efficiency improvement.

  • 2524.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, School of Computing.
    Phan, Hoc
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    On the Performance of Underlay Cognitive Radio Networks Using M/G/1/K Queuing Model2013In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, no 5, p. 876-879Article in journal (Refereed)
    Abstract [en]

    Motivated by a realistic scenario for cognitive radio systems, we model the underlay cognitive radio network (CRN) under interference power constraint imposed by the primary network as an M/G/1/K queueing system. The respective embedded Markov chain is provided to analyze several key queueing performance measures. In particular, the equilibrium probabilities of all states are derived and utilized to evaluate throughput, blocking probability, mean packet transmission time, mean number of packets in the system, and mean waiting time of an underlay CRN with Nakagami-m fading channels.

  • 2525.
    Chu, Thi My Chinh
    et al.
    Blekinge Institute of Technology, School of Computing.
    Phan, Hoc
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Opportunistic Spectrum Access for Cognitive Amplify-and-Forward Relay Networks2013Conference paper (Refereed)
    Abstract [en]

    In this paper, we study the performance of cognitive amplify-and-forward (AF) relay networks where the secondary users opportunistically access M licensed bands of the primary users over Nakagami-m fading channels. In order to enhance the accuracy of spectrum sensing and strongly protect the primary users from being interfered by the secondary transmission, collaborative spectrum sensing is deployed among the secondary transmitter, secondary relay, and secondary receiver. In particular, an analytical expression for the capacity of the considered network is derived. Numerical results are provided to show the influence of the arrival rate of the primary users on the channel utilization of licensed bands. Finally, the impact of the number of the licensed bands, channel utilization of the primary users, false alarm probability, and transmission distances on the capacity of the considered system are investigated.

  • 2526.
    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.

  • 2527.
    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.

  • 2528.
    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.

  • 2529.
    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.

  • 2530.
    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.

  • 2531.
    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

  • 2532.
    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.

  • 2533.
    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.

  • 2534.
    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

  • 2535.
    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

  • 2536.
    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.

  • 2537.
    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.

  • 2538.
    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.

  • 2539.
    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.

  • 2540.
    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.

  • 2541.
    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.

  • 2542.
    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.

  • 2543.
    Chukwuebuka, Owolabi Y. Lawal and Chukwuma K
    Blekinge Institute of Technology, School of Management.
    Evaluation of leadership and organizational performance in small scale industries in Nigeria: a case of selected small scale industries in Aba,Abia state,Nigeria2007Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    From time immemorial, the role of leaders in ensuring excellent organizational performance can not be over emphasized. The need for adequate motivation, suitable working environment, compensation and efficient communication between employers and employees are important to promoting excellent organization performance. Though studies on motivation and leadership role amongst employees are well studied in urban centers in developed countries, less could be said of rural centers in developing countries like Nigeria. Therefore, it was important to evaluate leadership and organizational performance in small- scale industries in Aba, Abia state, Nigeria. The evaluation was done through use of questionnaires with questions tailored towards determining: the relationship between leadership and organizational performance, pattern of leadership and the extent it has affected organizational performance, the factors responsible for worker’s low performance and how leadership style has affected labor management relations and productivity in three selected small scale industries in the study area. After analyzing the result with Chi-square, it was concluded that to attain the objectives of small-scale industries in Aba, Abia state Nigeria, it was necessary that leadership recognizes the needs of the workers, employ appropriate motivational tool such as promotion of staff based on merit and skills, provide suitable working environment and provide an appropriate leadership style that will encourage free flow of information among employer, superior officers and other employees.

  • 2544.
    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. 

  • 2545.
    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.

  • 2546.
    Chunduri, Krishna Chaitanya
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Gutti, Chalapathi
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Implementation of Adaptive Filter Structures on a Fixed Point Signal Processor for Acoustical Noise Reduction2005Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

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

  • 2547.
    Chuvarayan, Alexandra
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Peterson, Celia
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    Martel, Isabelle
    Blekinge Institute of Technology, School of Engineering, Department of Mechanical Engineering.
    A Strategic Approach for Sustainability and Resilience Planning within Municipalities2005Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    This research started by recognizing the role that local, municipal governments can play to reach the global goal of sustainability. In addition,a municipal community must be able to cope with change and disturbance in order to successfully achieve a sustainable future. This research investigates how improving municipal resilience can be a strategy to reach sustainability, and answers the primary research question “How can planning resilience help a municipal government lead a community towards sustainability?” Research was conducted through an inter-disciplinary literature review focusing on identifying key characteristics of resilience.Other methods included diagramming exercises to identify factors which foster or undermine resilience characteristics. Finally, implementable measures where identified which municipalities can implement to improve resilience and sustainability. These measures were selected using a synergy matrix, which helps select measures which most support principles for sustainability and resilience characteristics. The feasibility and current adoption of such measures was checked through interviews with municipal experts of Swedish, Canadian and Finnish municipalities.

  • 2548.
    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.

  • 2549.
    Cichocki, Radoslaw
    Blekinge Institute of Technology, School of Engineering, Department of Systems and Software Engineering.
    Classification of objects in images based on various object representations2006Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    Object recognition is a hugely researched domain that employs methods derived from mathematics, physics and biology. This thesis combines the approaches for object classification that base on two features – color and shape. Color is represented by color histograms and shape by skeletal graphs. Four hybrids are proposed which combine those approaches in different manners and the hybrids are then tested to find out which of them gives best results.

  • 2550. Ciszkowski, Tomasz
    et al.
    Eliasson, Charlott
    Fiedler, Markus
    Kotulski, Zbigniew
    Lupu, Radu
    Mazurczyk, Wojciech
    SecMon: end-to-end quality and security monitoring system2008In: Annales UMCS Informatica, ISSN 1732-1360, Vol. AI 8, no 1, p. 185-201Article in journal (Refereed)
    Abstract [en]

    The Voice over Internet Protocol (VoIP) is becoming a more available and popular way of communication for the Internet users. This also applies to the Peer-to-Peer (P2P) systems and merging these two have already proven to be successful (e.g. Skype). Even the existing standards of VoIP provide an assurance of security and Quality of Service (QoS), however, these features are usually optional and supported by a limited number of implementations. As a result, the lack of mandatory and widely applicable QoS and security guaranties makes the contemporary VoIP (P2P VoIP systems even more so than client-server ones) systems vulnerable to attacks and network disturbances. In this paper we are facing these issues and propose the SecMon system, which simultaneously provides a lightweight security mechanism and improves quality parameters of the call. SecMon is intended specially for VoIP service over P2P networks and its main advantage is that it provides authentication, data integrity services, adaptive QoS and (D)DoS attacks detection. Moreover, the SecMon approach represents a low-bandwidth consumption solution that is transparent to the users and possesses a self-organizing capability. The above- mentioned features are accomplished mainly by utilizing two information hiding techniques: digital audio watermarking and network steganography. These techniques are used to create covert channels that serve as transport channels for lightweight QoS measurement’s results. Furthermore, these metrics are aggregated in a reputation system that is used for the best route path selection in the P2P network. The reputation system also helps to mitigate (D)DoS attacks, maximize performance and increase transmission efficiency in the network.

48495051525354 2501 - 2550 of 13871
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