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  • 1. Dam, Hai Huyen
    et al.
    Nordebo, Sven
    Svensson, Lars
    Design of Digital Filters as the Sum of Two All--Pass Functions Using the Cepstrum Technique2003In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 51, no 3, p. 726-31Article in journal (Refereed)
  • 2. Kim, Kyeong Jin
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Poor, H. Vincent
    Shu, Lei
    Performance Analysis of Cyclic Prefixed Single-Carrier Spectrum Sharing Relay Systems in Primary User Interference2012In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 60, no 12, p. 6729-6734Article in journal (Refereed)
    Abstract [en]

    For cyclic prefixed single-carrier (CP-SC) spectrum sharing relay systems, the joint impact of the primary transmitter and primary receiver on the performance of secondary networks is investigated. A two-hop amplify-and-forward (AF) relay protocol is employed, and then its end-to-end signal-to-interference-ratio (e2e-SIR) is defined. An upper bound on the cumulative distribution function (CDF) of this e2e-SIR is derived for the CP-SC system. Having investigated an asymptotic expression for the CDF, the asymptotic outage diversity and coding gain can be obtained. Also, under a total transmission constraint, a suboptimal power allocation (sub-OPA) is derived for approximately minimizing the asymptotic outage probability. Monte Carlo simulations verify the derived outage probability and its asymptotic diversity gain with and without power allocation. It is shown that the primary transmitter has a major impact on the secondary network performance. Importantly, it is observed that when the interference from the primary transmitter proportionally increases with the interference power constraint at the primary receiver, the spectrum-sharing system results in no diversity gain for the full range of the SIR.

  • 3. Kim, Kyeong Jin
    et al.
    Duong, Quang Trung
    Blekinge Institute of Technology, School of Computing.
    Tran, Xuan Nam
    Performance Analysis of Cognitive Spectrum-Sharing Single-Carrier Systems With Relay Selection2012In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 60, no 12, p. 6435-6449Article in journal (Refereed)
    Abstract [en]

    In this paper, we analyze the performance of cooperative spectrum sharing single-carrier (SC) relay systems. Taking into account the peak interference power at the primary user (PU) and the maximum transmit power at the secondary user (SU) network, two separate power allocation constraints are formed. For a two-hop decode-and-forward (DF) relaying protocol and two power allocation constraints, two relay selection schemes, namely, a full-channel state information (CSI)-based best relay selection (BRS) and a partial CSI-based best relay selection (PBRS), are proposed. The distributions of the end-to-end signal-to-noise ratios (e2e-SNRs) for the four cases are derived first, and then their outage probabilities and asymptotic outage probabilities are derived in closed-form. The derived asymptotic outage probabilities are utilized to see different diversity gains. Monte Carlo simulations have verified the derived diversity gains for the four different cases. We also present upper bounds on the ergodic capacities for two particular cases.

  • 4. Schüldt, Christian
    et al.
    Lindström, Fredric
    Claesson, Ingvar
    A Low-Complexity Delayless Selective Subband Adaptive Filtering Algorithm2008In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 56, no 12, p. 5840-5850Article in journal (Refereed)
    Abstract [en]

    Adaptive filters of significant order, requiring high computational complexity, are necessary in many applications such as acoustic echo cancellation and wideband active noise control. Successful approaches to lessen the computational complexity of such filters are subband methods, and partial updating schemes where only a part of the filter is updated at each instant. To avoid the time delay introduced by the subband-splitting, delayless structures which reconstructs a fullband filter, producing delayless output, from the adaptive subband filters have been proposed. This paper proposes a delayless subband adaptive filter partial updating scheme, where the general idea is to only update the most misadjusted subband filter(s). Analysis in terms of mean square deviation is presented and shows that the fullband filter convergence speed is significantly increased, even for flat spectrum signals, as compared to traditional periodic subband filter update with the same computational complexity. Echo cancellation simulations with an artificial system to verify the analysis, using both flat spectrum signals and speech, is also presented, as well as offline calculations using signals from a real system.

  • 5. Tao, Xiao-Jiao
    et al.
    Claesson, Ingvar
    Grbic, Nedelko
    Narrowband acoustic doppler volume backscattering signal-part I: evolutionary spectral analysis2002In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 50, no 11, p. 2644-2655Article in journal (Refereed)
    Abstract [en]

    This paper examines the statistical properties of the narrowband Doppler volume backscattering process and analyzes its evolutionary spectrum. After clarifying the mechanism of both the finite duration Doppler effect and the continuously space-shifted integration process, the first two order time-varying statistics under a more general assumption, i.e., von Mises distribution, of random phase are derived. The generalization permits nonuniform phase tendency, which occurs in layered medium scattering. Based on the locally stationary process model, the evolutionary spectrum of the signal is derived. It is shown that the variation of the backscattering strength enters the spectrum as an amplitude modulation, whereas the variation of the random phase distribution acts as both the amplitude modulation and the frequency modulation. Finally, the observability of the average flow speed using spectral centroid estimate is discussed.

  • 6. Tao, Xiao-Jiao
    et al.
    Claesson, Ingvar
    Grbic, Nedelko
    Narrowband acoustic doppler volume backscattering signal-part II: spectral centroid estimation2002In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 50, no 10, p. 2656-2660Article in journal (Refereed)
    Abstract [en]

    This paper proposes a novel algorithm to estimate the time-varying spectral centroid of the narrowband Doppler volume backscattering signal. It is constructed in a semi-parametric way, that is, modeling parametrically the local narrowband evolutionary spectrum using an AR(2) and nonparametrically adapting its time-varying coefficients using the wavelet shrinkage. The improved performance is gained by the underlying linear prediction function of the AR(2) and the minimax optimality of the unknown smoothness adaptation of the wavelet shrinkage procedure.

  • 7.
    Trinh-Hoang, Minh
    et al.
    Tech Univ Darmstadt, DEU.
    Viberg, Mats
    Blekinge Inst Technol, S-37179 Karlskrona, Sweden..
    Pesavento, Marius
    Tech Univ Darmstadt, DEU.
    Partial Relaxation Approach: An Eigenvalue-Based DOA Estimator Framework2018In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 66, no 23, p. 6190-6203Article in journal (Refereed)
    Abstract [en]

    In this paper, the partial relaxation approach is introduced and applied to the direction-of-arrival estimation problem using spectral search. Unlike existing spectral-based methods such as conventional beamformer, Capon beamformer, or MUSIC that can be considered as single source approximation of multisource estimation criteria, the proposed approach accounts for the existence of multiple sources. At each considered direction, the manifold structure of the remaining interfering signals impinging on the sensor array is relaxed, which results in closed form estimates for the "interference" parameters. Thanks to this relaxation, the conventional multi-source optimization problem reduces to a simple spectral search. Following this principle, we propose estimators based on the deterministic maximum likelihood, weighted subspace fitting, and covariance fitting methods. To calculate the null-spectra efficiently, an iterative rooting scheme based on the rational function approximation is applied to the partial relaxation methods. Simulation results show that, irrespective of any specific structure of the sensor array, the performance of the proposed estimators is superior to the conventionalmethods, especially in the case of low signal-to-noise-ratio and low number of snapshots, while maintaining a computational cost that is comparable to MUSIC.

  • 8.
    Vu, Viet Thuy
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Pettersson, Mats
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Nyquist Sampling Requirements for Polar Grids in Bistatic Time-Domain Algorithms2015In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 63, no 2, p. 457-465Article in journal (Refereed)
    Abstract [en]

    The paper presents a derivation of Nyquist sampling requirements for the polar grids in some bistatic time-domain algorithms. The derivation is based on an airborne bistatic system with general bistatic geometry. The Nyquist sampling requirements are shown to be the functions of operating radar frequency, transmitter and receiver subaperture lengths, and bistatic geometry. How to decide the Nyquist sampling requirements for different bistatic geometries and the relationship between the Nyquist sampling requirements in the monostatic and bistatic cases are also addressed in the paper. The derived Nyquist sampling requirements is examined with the bistatic CARABAS-II like data.

  • 9. Vu, Viet Thuy
    et al.
    Sjögren, Thomas
    Pettersson, Mats
    Hellsten, Hans
    An Impulse Response Function for Evaluation of UWB SAR Imaging2010In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 58, no 7, p. 3927-3932Article in journal (Refereed)
    Abstract [en]

    Based on analysis of a point target imaged by different synthetic aperture radar (SAR) systems, the commonly used impulse response function in SAR Imaging (IRF-SAR)—a two-dimensional (2-D) sinc function—is shown to be inappropriate for ultrawideband-ultrawidebeam (UWB) SAR systems utilizing a large fractional signal bandwidth and a wide antenna beamwidth. As a consequence, the applications of the 2-D sinc function such as image quality measurements and spatial resolution estimations are limited to narrowband-narrowbeam (NB) SAR systems exploiting a small fractional signal bandwidth and a narrow antenna beamwidth. In this paper, a more general IRF-SAR, which aims at UWB SAR systems, is derived with an assumption of flat two-dimensional (2-D) Fourier transform (FT) of a SAR image and called IRF-USAR. However, the derived IRF-USAR is also valid for NB SAR systems.

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