| 1. |
- Viberg, Mats, 1961, et al.
(författare)
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Maximum Likelihood Array Processing in Spatially Correlated Noise Fields Using Parameterized Signals
- 1997
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Ingår i: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1941-0476 .- 1053-587X. ; 45, s. 996-1004
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the problem of estimating signal parameters using an array of sensors. This problem is of interest in a variety of applications, such as radar and sonar source localization. A vast number of estimation techniques have been proposed in the literature during the past two decades. Most of these can deliver consistent estimates only if the covariance matrix of the background noise is known. In many applications, the aforementioned assumption is unrealistic. Recently, a number of contributions have addressed the problem of signal parameter estimation in unknown noise environments based on various assumptions on the noise. Herein, a different approach is taken. We assume instead that the signals are partially known. The received signals are modeled as linear combinations of certain known basis functions. The exact maximum likelihood (ML) estimator for the problem at hand is derived, as well as a computationally more attractive approximation. The Cramer Rao lower bound (CRB) on the estimation error variance is also derived and found to coincide with the CRB, assuming an arbitrary deterministic model and known noise covariance.
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| 2. |
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| 3. |
- Swindlehurst, A., et al.
(författare)
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A subspace fitting method for identification of linear state-space models
- 1995
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Ingår i: IEEE Transactions on Automatic Control. - : IEEE Control Systems Society. - 0018-9286 .- 1558-2523. ; 40:2, s. 311-316
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Tidskriftsartikel (refereegranskat)abstract
- A new method is presented for the identification of systems parameterized bylinear state-space models. The method relies on the concept of subspacefitting, wherein an input/output data model parameterized by the statematrices is found that best fits, in the least-squares sense, the dominantsubspace of the measured data. Some empirical results are included to illustrate the performance advantage of the algorithm compared to standard techniques
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| 4. |
- Zetterberg, Per, et al.
(författare)
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The Spectrum Efficiency of a Base Station Antenna Array System for Spatially Selective Transmission
- 1995
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Ingår i: IEEE Transactions on Vehicular Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9545 .- 1939-9359. ; 44:3, s. 651-660
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we investigate the spectrum efficiency gain using ransmittingantenna arrays at the base stations of a mobile cellular etwork. The proposedsystem estimates the angular positions of the mobiles from the received data, and allows multiple mobiles to be allocated to the same channel within a cell. This is possible by applying a transmit scheme which directs nulls against co-channel users within the cell. It is shown that multiple mobiles per cell is an efficient way of increasing capacity in comparison with reduced channel reuse distance and narrow beams (without directed nulls). The effect of the spatial spread angle of the locally scattered rays in the vicinity of the mobile is also investigated
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| 5. |
- Östman, Thomas, et al.
(författare)
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An Improved MUSIC Algorithm for Estimation of Time Delays in Asynchronous DS-CDMA Systems
- 1999
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Ingår i: IEEE Transactions on Communications. - : IEEE Communications Society. - 0090-6778. ; 47:11, s. 1628-1631
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Tidskriftsartikel (refereegranskat)abstract
- The problem of near–far resistant time-delay estimation in an asynchronous direct-sequence code-division multipleaccess system is considered, and by better exploiting the structureof the problem, estimators superior to previously known techniques are obtained. For a typical numerical example, a gain insignal-to-noise ratio of approximately 3 dB is obtained.
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| 6. |
- Stoica, Petre, et al.
(författare)
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Comments on "Min-Norm interpretations and consistency of MUSIC, MODE, and ML"
- 1998
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Ingår i: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1053-587X .- 1941-0476. ; 46:8, s. 2262-2263
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Tidskriftsartikel (refereegranskat)abstract
- The results and interpretations obtained in the above referred paper are shown to be well known or obvious. Additionally, corrections to some misleading statements in the aforementioned paper are presented.
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| 7. |
- Astély, David, et al.
(författare)
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Constrained Complexity Spatio-Temporal Interference Rejection Combining
- 1999
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Ingår i: Proceedings of SPAWC’99, Signal Processing Advances in Wireless Communications. - : IEEE. ; , s. 110-113
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Konferensbidrag (refereegranskat)abstract
- Space-time processing for co-channel interference (CCI) rejection and equalization with antenna arrays may provide large gains over space-only processing, especially in interference limited scenarios. However, taking thetemporal correlation of the noise and CCI process into account leads to sequence detection with highercomplexity as compared to space-only processing that neglects this correlation. We propose the use of the generalized Viterbi algorithm for sequence detection with lower complexity. Special cases include the M-algorithm and the delayed decision feedback sequence estimator. A relevant comparison between spatial andspatio-temporal processing with sequence detectors of the same complexity may thus be performed. Numerical examples show substantial gains for spatio-temporal processing as compared to space-only processing also in this case when the optimality of the sequence detector is traded for interference rejection.
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| 8. |
- Astély, David, et al.
(författare)
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Spatial signature estimation for uniform linear arrays with unknown receiver gains and phases
- 1999
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Ingår i: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1053-587X .- 1941-0476. ; 47:8, s. 2128-2138
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Tidskriftsartikel (refereegranskat)abstract
- The problem of spatial signature estimation using a uniform linear array (ULA) with unknown receiver gain and phase responses is studied. Sufficient conditions for identifying the spatial signatures are derived, and a closed-Form ESPRIT-like estimator is proposed, The performance of the method is investigated by means of simulations and on experimental data collected with an antenna array in a suburban environment. The results show that the absence of receiver calibration is not critical for uplink signal waveform estimation using a plane wave model.
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| 9. |
- Astély, David, et al.
(författare)
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The effects of local scattering on direction of arrival estimation with MUSIC
- 1999
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Ingår i: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1053-587X .- 1941-0476. ; 47:12, s. 3220-3234
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Tidskriftsartikel (refereegranskat)abstract
- In wireless communication scenarios, multipath propagation may cause angular spreading as seen from a base station antenna array. Environments where most energy incident on the array is from scatterers local to the mobile transmitters are considered, and the effects on direction of arrival (DOA) estimation with the MUSIC algorithm are studied. Previous work has studied rapidly time-varying channels and concluded that local scattering has a minor effect on DOA estimation in such scenarios. In this work, a channel that is time-invariant during the observation period is considered, and under the assumption of small angular spread, an approximate distribution for the DOA estimates is derived. The results show that local scattering has a significant impact on DOA estimation in the time invariant case. Numerical examples are included to illustrate the analysis and to demonstrate that the results may be used to formulate a simple estimator of angular spread. An extension to more general Rayleigh and Ricean fading channels is also included, In addition, results from processing experimental data collected in suburban environments are presented. Good agreement with the derived distributions is obtained.
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| 10. |
- Asztély, David, et al.
(författare)
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A Generalized Array Manifold Model for Local Scattering in Wireless Communications
- 1997
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Ingår i: Proceedings of IEEE International Conference on Acoustics, Speech, and Signal Processing. ICASSP-97. - : IEEE. ; , s. 4021-4024
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Konferensbidrag (refereegranskat)abstract
- In wireless communication scenarios, local scatterers in the vicinity of the mobile sources cause angular spreading. As a result, the spatial signatures will not belong to the conventional array manifold parameterized by direction of arrival (DOA) alone. A parameterized model for spatial signatures applicable in scenarios with localscattering is presented. Several algorithms that exploit this model are proposed, and the performance of signal waveform estimators using the model is investigated via simulations. It is demonstrated that considerable gain may result as compared with using the conventional plane wave model.
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