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- Bengtsson, Mats, 1967-, et al.
(författare)
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Recent Advances on MIMO Processing in the SATURN Project
- 2002
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Ingår i: Proc. IST Mobile Communications Summit.
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Konferensbidrag (refereegranskat)abstract
- We highlight some recent results on the theory and algorithmsfor MIMO systems, obtained at the Royal Instituteof Technology (KTH) within the SATURN project.The paper includes a a new approximate expression forthe ergodic channel capacity of a MIMO system with correlatedfading, algorithms for MIMO beamforming underEIRP (equivalent isotropic radiated power) constraintsand a low-complexity algorithm for MIMO channel estimationin OFDM systems. Also, we show how transmitand beamformers can be determined in a decentralizedfashion without explicitly estimating the channel response.
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- Bengtsson, Mats, 1967-, et al.
(författare)
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A generalization of weighted subspace fitting to full-rank models
- 2001
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Ingår i: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1053-587X .- 1941-0476. ; 49:5, s. 1002-1012
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Tidskriftsartikel (refereegranskat)abstract
- The idea of subspace fitting provides a popular framework for different applications of parameter estimation and system identification. Previously, some algorithms have been suggested based on similar ideas, for a sensor array processing problem where the underlying data model is not low rank. We show that two of these algorithms (DSPE and DISPARE) fail to give consistent estimates and introduce a general class of subspace fitting-like algorithms for consistent estimation of parameters from a possibly full-rank data model. The asymptotic performance is analyzed, and an optimally weighted algorithm is derived. The result gives a lower bound on the estimation performance for any estimator based on a low-rank approximation of the linear space spanned by the sample data. We show that in general, for full-rank data models, no subspace-based method can reach the Cramer-Rao lower bound (CRB)
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| 7. |
- Bengtsson, Mats, 1967-, et al.
(författare)
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Measurements of Spatial Characteristics and Polarization with a Dual Polarized Antenna Array
- 1999
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Ingår i: Proceedings IEEE Vehicular Technology Conference. - : IEEE. ; , s. 366-370
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Konferensbidrag (refereegranskat)abstract
- We consider antenna arrays equipped with cross-polarized antenna elements. The multipath propagation will affect both the spatial characteristics and the polarization of the received signals which will influence the performance of the system in terms of, for example, bit error rate or direction estimation. In this paper, we present results from field measurement data recorded at the 1800 MHz band, provided by Ericsson Radio Systems AB. The study is divided into two main parts. In the first part we introduce a diversity gain measure related to the BER of an MRC receiver. The polarization diversity introduced by the radio channel is studied, and compared to the spatial diversity. In the second part we use a parameterized model of the received polarized radio waves and illustrate the typical behavior of the estimated polarization parameters
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| 9. |
- Bengtsson, Mats, 1967-, et al.
(författare)
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Optimal Downlink BeamformingUsing Semidefinite Optimization
- 1999
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Ingår i: Proc. of 37th Annual Allerton Conference on Communication,Control, and Computing. ; , s. 987-996
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- When using antenna arrays at the base station of a cellular system, one critical aspectis the transmission strategy. An optimal choice of beamformers for simultaneous transmissionto several co-channel users must be solved jointly for all users and base stations in anarea. We formulate an optimal transmit strategy and show how the solution can be calculatedefficiently using interior point methods for semidefinite optimization. The algorithmminimizes the total transmitted power under certain constraints to guarantee a specificquality of service. The method provides large flexibility in the choice of constraints andcan be extended to be robust to channel perturbations.
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| 10. |
- Bengtsson, Mats, 1967-, et al.
(författare)
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Rooting Techniques for Estimation of Angular Spread with an Antenna Array
- 1997
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Ingår i: Proceedings of IEEE 47th Vehicular Technology Conference. VTC 97. - : IEEE. ; , s. 1158-1162
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Konferensbidrag (refereegranskat)abstract
- When antenna arrays are used in mobile communications systems, multipath propagation effects must be taken into account. Local scattering around each signal source causes angular spreading. One important parameter foroptimal transmit and receive algorithms is the width of the angular spread of each scattered source signal. We present a new principle for consistent estimation of direction of arrival as well as angular spread using standardrooting techniques such as root MUSIC, MODE or ESPRIT. The computational complexity is much lower than forpreviously suggested algorithms.
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