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  • 1. Brik, Bouziane
    et al.
    Lagraa, Nasreddine
    Lakas, Abderrahmane
    Cherroun, Hadda
    Cheddad, Abbas
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    ECDGP: extended cluster-based data gathering protocol for vehicular networks2015In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677Article in journal (Refereed)
  • 2.
    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.

  • 3.
    Duong, Quang Trung
    et al.
    Blekinge Institute of Technology, School of Computing.
    Shu, Lei
    Chen, Min
    Vo Nguyen Quoc, Bao
    Dac Binh, Ha
    Performance analysis of cooperative spatial multiplexing networks with AF/DF relaying and linear receiver over Rayleigh fading channels2015In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, Vol. 15, no 3, p. 500-509Article in journal (Refereed)
    Abstract [en]

    Cooperative spatial multiplexing (CSM) system has played an important role in wireless networks by offering a substantial improvement in multiplexing gain compared with its cooperative diversity counterpart. However, there is a limited number of research works that consider the performance of CSM systems. As such, in this paper, we have derived exact performance of CSM with amplify-and-forward and decode-and-forward relays in terms of outage capacity and ergodic capacity. We have shown that CSM systems yield a unity diversity order regardless of the number of antennas at the destination and the number of relays in the networks, which is the direct result of diversity and multiplexing gain trade-off. Our analytical expressions are corroborated by Monte-Carlo simulations.

  • 4. Nordebo, Sven
    et al.
    Mohammed, Abbas
    A Semi-definite Programming Approach to Spatial Decorrelation of Independently Polarized Signals2007In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, Vol. 7, no 1, p. 91-101Article in journal (Refereed)
    Abstract [en]

    A MIMO channel spatial decorrelation scheme based on semi-definite programming is introduced. As a particular application example, the paper addresses the potential gain of using multiple antennas and MIMO-OFDM techniques in order to increase the bandwidth efficiency in satellite communication systems. In particular, we consider the increase in channel capacity that is possible by exploiting satellite and polarization diversity. A fundamental case is studied with three satellite branches, and where each transmit/receive antenna unit consists of six elemental electric and magnetic dipoles yielding six distinguishable parallel polarization channels per frequency. The numerical examples show that capacity increases linearly on a logarithmic signal-to-noise ratio scale where the constant of proportionality is the number of active parallel channels. In this respect, the simultaneous use of triple electric and triple magnetic dipoles has the potential to triple the capacity of an antenna system based on antenna units of single dipoles. Copyright (c) 2006 John Wiley & Sons, Ltd.

  • 5.
    Phan, Hoc
    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.
    Duong, Quang Trung
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Tran, Hung
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Chu, Thi My Chinh
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Cognitive amplify-and-forward relay networks with beamforming under primary user power constraint over Nakagami-m fading channels2015In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, Vol. 15, no 1, p. 56-70Article in journal (Refereed)
    Abstract [en]

    In this paper, we analyze the performance of cognitive amplify-and-forward (AF) relay networks with beamforming under the peak interference power constraint of the primary user (PU). We focus on the scenario that beamforming is applied at the multi-antenna secondary transmitter and receiver. Also, the secondary relay network operates in channel state information assisted AF mode, and the signals undergo independent Nakagami-m fading. In particular, closed-form expressions for the outage probability and symbol error rate (SER) of the considered network over Nakagami-m fading are presented. More importantly, asymptotic closed-form expressions for the outage probability and SER are derived. These tractable closed-form expressions for the network performance readily enable us to evaluate and examine the impact of network parameters on the system performance. Specifically, the impact of the number of antennas, the fading severity parameters, the channel mean powers, and the peak interference power is addressed. The asymptotic analysis manifests that the peak interference power constraint imposed on the secondary relay network has no effect on the diversity gain. However, the coding gain is affected by the fading parameters of the links from the primary receiver to the secondary relay network.

  • 6.
    Sibomana, Louis
    et al.
    University of Rwanda, RWA.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Ergodic capacity of multiuser scheduling in cognitive radio networks: Analysis and comparison2016In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, Vol. 16, no 16, p. 2759-2774Article in journal (Refereed)
    Abstract [en]

    This paper analyzes the ergodic capacity of secondary point-to-multipoint communications under the outage constraint of multiple primary user receivers (PU-Rxs) and the secondary user (SU) maximum transmit power limit. We first derive analytical expressions of the ergodic capacity for three scheduling schemes, that is, round robin, Max-signal-to-interference-plus-noise-ratio (Max-SINR) and Min-SINR, and compare their performance. Numerical examples show that when the number of SU receivers (SU-Rxs) increases in the presence of a single PU-Rx and at high SINR, the Min-SINR outperforms the Max-SINR scheme. As the number of PU-Rxs increases, the Max-SINR performs better than the Min-SINR scheduling. When the number of SU-Rxs becomes large, the system capacity is enhanced but so is the feedback load. To exploit the Max-SINR transmission while reducing the feedback load, we assume a threshold based on the channel quality where the SU-Rxs with the instantaneous SINR above the threshold participate in the Max-SINR scheduling; otherwise, an SU-Rx is selected randomly. Then, an analytical expression of the average capacity is derived. Numerical results illustrate that the capacity with limited feedback is approximately the same as for the case of Max-SINR with full feedback when the SU threshold for feedback condition is set to low and medium values.

  • 7.
    Tran, Hung
    et al.
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Phan, Hoc
    Cognitive cooperative networks with decode-and-forward relay selection under interference constraints of multiple primary users2015In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, Vol. 15, no 10, p. 1433-1443Article in journal (Refereed)
    Abstract [en]

    In this paper, we study the performance of cognitive cooperative radio networks under the peak interference power constraints of multiple primary users (PUs). In particular, we consider a system model where the secondary user communication is assisted by multiple secondary relays (SRs) that operate in the decode-and-forward mode to relay the signal from a secondary transmitter to a secondary receiver. Moreover, we assume that the transmit powers of the secondary transmitter and the SRs are subject to the peak interference power constraints of multiple PUs that operate in their coverage range. Given this system setting, we first derive the cumulative distribution function of the instantaneous end-to-end signal-to-noise ratio. Then, we obtain a closed-form expression for the outage probability and an exact expression for the symbol error probability of the considered network. These tractable formulas enable us to examine the impact of the presence of multiple PUs on the performance of the considered spectrum sharing system. Furthermore, our numerical results show that system performance is improved significantly when the number of SRs increases or the channel mean power from the secondary user to the PUs is low. Also, any increase in the number of PUs in the coverage range of the secondary transmitter or the SRs leads to degradation in system performance. Finally, Monte Carlo simulations are provided to verify the correctness of our analytical results.

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