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  • 1. Duong, Quang Trung
    et al.
    Alexandropoulos, George C.
    Tsiftsis, Theodoros A.
    Zepernick, Hans-Jürgen
    Outage probability of MIMO AF relay networks over Nakagami-m fading channels2010Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 46, nr 17Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The outage probability (OP) of multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay networks using orthogonal space-time block code is investigated. In particular, a closed-form tight lower bound expression for the OP over independently but not necessarily identically distributed Nakagami-m fading channels is derived. Moreover, an asymptotic approximation for OP which reveals the coding and diversity gains is presented. The analytical expressions are validated by Monte-Carlo simulations.

  • 2. Duong, Quang Trung
    et al.
    Bao, Vo Nguyen Quoc
    Performance Analysis of Selection Decode-and-Forward Relay Networks2008Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 44, nr 20, s. 1206-07Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The performance of decode-and-forward (DF) cooperative networks with relay selection is presented. Specifically, we derive closed-form expressions for symbol error probability (SEP), bit error rate (BER), and achievable spectral efficiency of DF relay selection system in independent but not identically distributed (i.n.i.d.) Rayleigh fading channels taking into account the incapability of decoding the received signals' cyclic redundancy code (CRC) at the relays. We also perform Monte-Carlo simulations to validate the analysis.

  • 3. Duong, Quang Trung
    et al.
    Bao, Vo Nguyen Quoc
    Alexandropoulos, George C.
    Zepernick, Hans-Jürgen
    Cooperative spectrum sharing networks with AF relay and selection diversity2011Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 47, nr 20, s. 1149-1151Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The exact outage probability (OP) of cognitive dual-hop relay networks equipped with a single amplify-and-forward (AF) relay and a selection combining receiver at the destination is derived under spectrum sharing constraint on a primary user. The tractable closed-form OP readily enables evaluation of system performance, which indicates the significance of using a relay in cognitive radio networks with a spectrum sharing approach. The proposed analysis is validated by numerical examples.

  • 4.
    Duong, Quang Trung
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Bao, Vo Nguyen Quoc
    Tran, Hung
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Alexandropoulos, George C.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Effect of primary network on performance of spectrum sharing AF relaying2012Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 48, nr 1, s. 25-U95Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Most of the research in spectrum sharing has neglected the effect of interference from primary users. In this reported work, the performance of spectrum sharing amplify-and-forward relay networks under interference-limited environment, where the interference induced by the transmission of primary networks is taken into account, is investigated. In particular, a closed-form expression tight lower bound of outage probability is derived. To reveal additional insights into the effect of primary networks on the diversity and array gains, an asymptotic expression is also obtained.

  • 5. Duong, Quang Trung
    et al.
    Bao, Vo Nguyen Quoc
    Zepernick, Hans-Jürgen
    Exact outage probability of cognitive AF relaying with underlay spectrum sharing2011Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 47, nr 17, s. 1001-1002Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The exact closed-form expression for the outage probability (OP) of cognitive radio dual-hop amplify-and-forward (AF) relay networks is derived. The tractable expression of the OP, given in the form of elementary functions, readily enables evaluating the effect of primary users on the secondary system performance. It has been shown that the use of AF relaying significantly improves the performance of cognitive radio networks compared to its direct transmission counterpart.

  • 6. Duong, Quang Trung
    et al.
    Zepernick, Hans-Jürgen
    Bao, Vo Nguyen Quoc
    Symbol error probability of hop-by-hop beamforming in Nakagami-m fading2009Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 45, nr 20, s. 1042-1044Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The symbol error probability (SEP) of amplify-and-forward(AF) multiple-input multiple-output (MIMO) cooperative networks where beamforming is adopted at both the source and destination is investigated. In particular, the tight lower bound for SEP of AF MIMO relay systems is presented with hop-by-hop beamforming over independent, but not necessarily identically distributed, Nakagami-m fading channels. Furthermore, assessing the high SNR, an asymptotic SEP expression is derived which reveals the array and diversity gain. Numerical results are shown to verify the analysis in some representative scenarios.

  • 7. Mohammed, Abbas
    Effect of Loran-C Signal Parameters on Skywave Delay Estimation of IFFT Technique2003Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 39, nr 14, s. 1091-1093Artikel i tidskrift (Refereegranskat)
  • 8. Mohammed, Abbas
    et al.
    last, David
    High Resolution Techniques for Loran-C Skywave Delay Estimation1999Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 35, nr 18, s. 1516-1517Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two high-resolution estimation techniques are applied to the problem of estimating the delays of the skywave components of signals input to Loran-C receivers. Their performance is evaluated and compared with that of a Fourier-based spectral-division technique. Simulation results show that the high-resolution algorithms improve the accuracy of the estimates significantly and estimate the skywave delay successfully in situations in which the Fourier-based method fails.

  • 9. Mohammed, Abbas
    et al.
    Last, David
    IFFT Technique for Skywave Detection in Loran-C Receivers2001Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 37, nr 6, s. 398-400Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An inverse fast Fourier transform (IFFT) technique is presented for isolating groundwave are and skyware components of Loran-C signals in receivers under conditions of very low signal-to-noise ratio. It includes the first example of the measurement of the skywave delays of off-air signals made using this method.

  • 10. Mohammed, Abbas
    et al.
    Last, David
    Loran-C Skywave Delay Detection using the ARMA Algorithm1998Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 34, nr 17, s. 1654-5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The autoregressive moving average technique (ARMA) is applied to the problem of estimating the delay of Loran-C skywaves. The performance of this technique is evaluated and compared with Fourier-based methods. The simulation results show thatthe ARMA algorithm yields significantly greater estimation accuracy and that it can also operate successfully with very noisy signals.

  • 11. Mohammed, Abbas
    et al.
    Last, David
    Loran-C skywave delay estimation using the AR Algorithm1998Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 34, nr 23, s. 2217-2219Artikel i tidskrift (Refereegranskat)
  • 12. Rohani, Behrooz
    et al.
    Rohani, Bijan
    Caldera, Manora
    Zepernick, Hans-Jürgen
    Benefits of Perceptual Speech Quality Metrics in Modern Cellular Systems2006Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 42, nr 21, s. 1250-1251Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Advanced algorithms have become available in recent years that can reliably measure the speech quality as “perceived” by humans. The benefits of applying the perceptual quality measures obtained using these algorithms in the Outer Loop Power Control (OLPC) of Third Generation Universal Mobile Telecommunication System (3G UMTS) are studied in this letter. It is shown that 20% capacity improvement compared to the use of conventional measures can be achieved while an adequate and uniform speech quality is maintained.

  • 13. Rohani, Behrooz
    et al.
    Rohani, Bijan
    Zepernick, Hans-Jürgen
    Feedback Method for Real-time Perceptual Quality Estimation2004Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 40, nr 14, s. 913-914Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a feedback scheme for real-time estimation of perceptual speech quality is proposed. The feedback information indicates the quality of each previously received speech frame as “good” or “bad”. This information is used in conjunction with the PESQ algorithm to estimate the received speech quality accurately.

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