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  • 2451.
    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.

  • 2452.
    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.

  • 2453.
    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.

  • 2454.
    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.

  • 2455.
    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.

  • 2456.
    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.

  • 2457.
    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.

  • 2458.
    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.

  • 2459.
    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.

  • 2460.
    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.

  • 2461.
    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.

  • 2462.
    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.

  • 2463.
    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.

  • 2464.
    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.

  • 2465.
    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

  • 2466.
    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.

  • 2467.
    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.

  • 2468.
    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

  • 2469.
    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

  • 2470.
    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.

  • 2471.
    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.

  • 2472.
    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.

  • 2473.
    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.

  • 2474.
    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.

  • 2475.
    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.

  • 2476.
    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.

  • 2477.
    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.

  • 2478.
    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. 

  • 2479.
    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.

  • 2480.
    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.

  • 2481.
    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.

  • 2482.
    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.

  • 2483.
    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.

  • 2484. 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.

  • 2485. Ciszkowski, Tomasz
    et al.
    Mazurczyk, Wojciech
    Kotulski, Zbigniew
    Hossfeld, Tobias
    Fiedler, Markus
    Collange, Denis
    Towards Quality of Experience-based Reputation Models for Future Web Service Provisioning2009Conference paper (Refereed)
    Abstract [en]

    This paper concerns the applicability of reputations systems for assessing Quality of Experience (QoE) for web services in Future Internet. Reputation systems provide mechanisms to manage subjective opinions in societies and yield general scoring of a particular behavior. Thus, they are likely to become an important ingredient of Future Internet. Parameters being under evaluation by reputation system may vary greatly and, particularly, may be chosen to assess the users’ satisfaction with (composite) web services. Currently, this satisfaction is usually expressed with QoE, which represents subjective users’ opinions. The goal is to predict users’ satisfaction based on reputation values. This may be beneficial for service providers in terms of checking the fulfillment of SLAs, for retaining QoE on the satisfaction level for other users sharing the same network or service resources, and for providing the users with indications which resource to choose in order to maximize its experience.

  • 2486. Ciszkowski, Tomasz
    et al.
    Mazurczyk, Wojciech
    Kotulski, Zbigniew
    Hossfeld, Tobias
    Fiedler, Markus
    Blekinge Institute of Technology, School of Computing.
    Collange, Denis
    Towards Quality of Experience-based reputation models for future web service provisioning2012In: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 51, no 4, p. 283-295Article in journal (Refereed)
    Abstract [en]

    This paper concerns the applicability of reputations systems for assessing Quality of Experience (QoE) for web services in Future Internet. Reputation systems provide mechanisms to manage subjective opinions in societies and yield a general scoring of a particular behavior. Thus, they are likely to become an important ingredient of Future Internet. Parameters being under evaluation by a reputation system may vary greatly and, particularly, may be chosen to assess the users’ satisfaction with (composite) web services. Currently, this satisfaction is usually expressed by QoE, which represents subjective users’ opinions. The goal of this paper it to present a novel framework of web services where a reputation system is incorporated for users satisfaction tracking and prediction. This approach is a beneficial tool, which enables providers to facilitate service adaptation according to users’ expectations and maintain QoE on a satisfying level. Presented reputation system operates in an environment of composite services running on a client and server side. It makes this approach highly suitable for effective QoE differentiating and maximizing user experience for specific customer profiles even the service and network resources are shared.

  • 2487.
    Civelek, Ülkan Fuat
    Blekinge Institute of Technology, School of Computing.
    An Agent-Based Approach for Automating the Process of Charging Plug-in Electric Vehicles2010Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The study of Power TAC is a Multi-Agent competitive simulation test-bed, providing opportunity to simulate research and developments of electronic agents which can manage the tasks of the consumers and energy resources in a virtual energy infrastructure. According to the Power TAC scenario, Plug-in Electrical Vehicles are a special type of consumers that interact with this infrastructure and sometimes with the producers through aggregators. The aim of this study is modeling an intelligent Plug-in Electric vehicle agent for Power TAC that acts as an intermediary between Power TAC grid and vehicle owners. The proposed agent acts autonomously and is capable of making decisions about its energy needs by learning the driving behaviors and other preferences of these vehicle owners in a specified time interval. These agents will be able to make decisions about buying energy from the grid when the charging process is necessary or sell their energy back to the grid when the conditions of the electricity market are sufficiently attractive. The objective of this study is to model a Multi-Agent system for automating the process of charging the plug-in Vehicle Agents in Power TAC scenario by determining the necessary agents and the simulation environment where the agents constructed and simulated. Аs results of this study, different strategies are defined by considering the preferences of the vehicle owners and the conditions of the vehicle; thereby the agents autonomously bid behalf of their user in order to automate the process of charging.

  • 2488.
    Claesson, Christian
    Blekinge Institute of Technology, Faculty of Engineering, Department of Spatial Planning.
    Stad i ljus: En undersökning om bygglovsbefriade solpaneler2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Att det finns en pågående klimatförändring kan nog ses som en ganska stor självklarhet av många och en lösning kan vara införande av mer förnyelsebar energi. Solpaneler tycker jag är den mest intressanta, men hur ser regelverken kring bygglov för solpaneler ut och hur välvilliga är kommunerna att införa befrielser i byggloven. Denna undersökningen  handlar om bygglovsbefriade solpaneler i alla Sveriges 290 kommuner. 

  • 2489. Claesson, Ingvar
    Dual Microphone input for Mobile Telephony2000Conference paper (Refereed)
  • 2490. Claesson, Ingvar
    FFT i ett historiskt perspektiv1997Conference paper (Refereed)
    Abstract [en]

    Några nedslag i Fouriertransformens historia och FFT:ns ursprung från 1805 och framåt behandlas i denna populära betraktelse. Vi stannar upp ett slag hos Gauss, funderar över vad han gjort för oss ingenjörer och vi avslutar med en del praktiska konsekvenser och tips som är aktuella idag.

  • 2491. Claesson, Ingvar
    FFT i ett historiskt perspektiv1997Conference paper (Refereed)
  • 2492. Claesson, Ingvar
    FFT i ett historiskt perspektiv1997In: SVIB vibrationsnytt , ISSN 0281-6830, Vol. 14/15, no 1, p. 11-15Article in journal (Refereed)
  • 2493. Claesson, Ingvar
    et al.
    Dahl, Mattias
    Nordebo, Sven
    Applied Complex Chebyshev Optimization Using Dual Nested Complex Approximation2001Conference paper (Refereed)
  • 2494. Claesson, Ingvar
    et al.
    Dahl, Mattias
    Nordebo, Sven
    Nordholm, Sven
    Acoustic Echo Cancelling with microphone arrays1995Conference paper (Refereed)
  • 2495. Claesson, Ingvar
    et al.
    Dahl, Mattias
    Nordebo, Sven
    Nordholm, Sven
    Chebyshev Optimization of Circular Arrays Inequalities1998Conference paper (Refereed)
  • 2496. Claesson, Ingvar
    et al.
    Håkansson, Lars
    Active Control of Machine-Tool Vibration in a Lathe1997Conference paper (Refereed)
    Abstract [en]

    In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration is a frequent problem, which affects the result of the machining, in particular the surface finish. The tool life is also influenced by the vibrations. When the working environment is considered, noise is frequently introduced by dynamic motion between the cutting tool and the workpiece. By proper machine design, e.g. improved stiffness of the machine structure, the problem of relative dynamic motion between cutting tool and workpiece may be partially solved. However, by active control of machine-tool vibration, a further reduction of the dynamic motion between cutting tool and workpiece can be achieved. It was found that adaptive feedback control based on the filtered-x LMS-algorithm enables a reduction of the vibration with up to 40 dB at 1.5 kHz and simultaneously with approximately 40 dB at 3 kHz. A significant improvement of the workpiece surface was observed and a substantial improvement of the acoustic noise level was obtained with adaptive control.

  • 2497. Claesson, Ingvar
    et al.
    Håkansson, Lars
    Adaptive Active Control of Machine-Tool Vibration In a Lathe1998In: International Journal of Acoustics and Vibration, ISSN 1027-5851, Vol. 3, no 4, p. 155-162Article in journal (Refereed)
    Abstract [en]

    In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration, is a frequent problem, which affects the result of the machining, and in particular, the surface finish. Tool life is also influenced by vibration. Noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. With proper machine design, i.e. improved stiffness of the machine structure, the problem of relative dynamic motion between cutting tool and workpiece may be partially solved. However, by active control of machine-tool vibration, a further reduction of the dynamic motion between cutting tool and workpiece can be achieved. It was found that adaptive feedback control of tool vibration in the cutting speed direction, based on the filtered-x LMS-algorithm, enables a reduction in vibration, by up to 40 dB at 1.5 kHz, and by approximately 40 dB at 3 kHz. It was also observed that the introduction of leakage in the filtered-x LMS-algorithm improved the stability properties of the feedback control system. A significant improvement in the workpiece surface was observed and a substantial improvement in the acoustic noise level was obtained with adaptive control.

  • 2498.
    Claesson, Ingvar
    et al.
    Blekinge Institute of Technology, Department of Signal Processing.
    Håkansson, Lars
    Blekinge Institute of Technology, Department of Signal Processing.
    Lagö, Thomas L
    Robust Control of Machine-Tool Vibration in a Lathe1999Conference paper (Refereed)
    Abstract [en]

    In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration, is a frequent problem, which affects the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced substantially by active control of the machine-tool vibration. Adaptive feedback control based on the filtered-x LMS-algorithm, enables a reduction of the vibration by up to 40 dB at 1.5 kHz and by approximately 40 dB at 3 kHz. The active control performeds a broadband attenuation of the sound pressure level by up to 35 dB. However, the process of machining a workpiece usually involves a variety of cutting data which in turn are likely to cause substantial variations in the spectral properties of the tool vibrations. Hence, variations in the spectral properties originates from changes in the excitation of the tool holder and changes in the structural response of the tool holder. To handle the potential large variations in the spectral properties of tool vibration in the turning operation the robustness of the control system has to be improved. By applying the leaky version of the filtered-x LMS algorithm in the active control of machine tool vibration it was found that the robustness of the adaptive control system was improved substantially to large variations in the spectral properties of tool vibration.

  • 2499. Claesson, Ingvar
    et al.
    Nilsson, Andreas
    Cancellation of Humming GSM Mobile Telephone Noise2003Conference paper (Refereed)
    Abstract [en]

    A sometimes annoying problem in the most internationally widespread cellular telephone system, the GSM system, is an interfering signal generated by the switching nature of TDMA cellular telephone system. A humming noise originating from the speech frames, equivalent to 160 samples of data corresponding to 20 ms at 8 kHz sampling rate is sometimes clearly audible. This paper describes a study of two different software solutions designed to suppress such interference internally in the mobile handset. The methods are Notch Filtering, which is performed on a sample-per-sample basis, and Speech Frame Noise Cancellation, which is an alternative method employing correlators and subtraction, similar to Active Noise Control.

  • 2500. Claesson, Ingvar
    et al.
    Nilsson, Andreas
    GSM TDMA Frame Rate Internal Active Noise Cancellation2003In: International Journal of Acoustics and Vibration, ISSN 1027-5851, Vol. 8, no 3, p. 159-166Article in journal (Refereed)
    Abstract [en]

    A common problem in the world's most widely-used cellular telephone system, the GSM system, is the interfering signal generated by the switching nature of TDMA cellular telephony in handheld and other terminals. Signals are sent as chunks of data, speech frames, equivalent to 160 samples of data corresponding to 20 ms at sampling rate of 8 kHz. This paper describes a study of two different software solutions designed to suppress such interference internally in the mobile handset. The methods are 1) notch filtering, which is multiplicative in frequency, and 2) subtractive noise cancellation, which is an alternative method employing correlators. The latter solution is a straigtforward, although somewhat unorthodox, application of "in-wire" active noise control. Since subtraction is performed directly in the time domain, and we have access to the state of the mobile, it is also possible to consider a recurring pause in the interference caused by the idle frame in the transmission, when the mobile listens to other base stations communicating. More complex control algorithms, based on the state of the communication between the handset and the base station, can be utilised.

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  • rtf