| 1. |
- 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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| 2. |
- 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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| 3. |
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| 4. |
- Samuelsson, David, et al.
(författare)
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Optimal downlink beamforming with additional constraints
- 2003
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Ingår i: CONFERENCE RECORD OF THE THIRTY-SEVENTH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS. - 0780381041 ; , s. 1811-1814
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Konferensbidrag (refereegranskat)abstract
- This work addresses the problem of joint downlink beamforming and power control with general Quality of Service (QoS) constraints. Previous work on downlink beamforming does not provide a framework to handle the additional constraints in a straightforward fashion. Herein, it is shown that the QoS requirements can be formulated as quadratic constraints to a convex optimization problem. An efficient algorithm for solving the problem, based on semidefinite optimization is presented. To demonstrate the performance of the proposed approach, we present an example using quadratic constraints to greatly decrease the probability of a low instantaneous Signal to Interference and Noise Ratio (SINR) for a receiver equipped with a RAKE combiner.
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| 5. |
- Yu, Kai, et al.
(författare)
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A 20 MHz HIPERLAN/2 MIMO Channel Model in NLOS Indoor Scenarios
- 2002
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Ingår i: Nordic Conference on Radio Science and Communications (RVK). ; , s. 311-315
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, we present results of 5.2 GHz wideband indoor multiple input multiple output (MIMO) channel measurementsunder the EU IST SATURN project. First we show the average power delay profile for the single input single output (SISO) channel. Furthermore, our investigation shows that for non-line-of-sight (NLOS) indoor scenarios, the MIMO channel covariance matrix of each normalized tap of channel impulse response can be be well approximated by the Kronecker product of the covariance matrices seen from the transmitter and receiver respectively.Based on the above results, a wideband statistical model for HiperLAN/2 MIMO channel is presented. Monte-Carlo simulations show reasonably good agreement between the measured data and our model. Finally, weuse this model to show the capacity characteristics of theHiperLAN/2 channel in NLOS indoor scenarios.
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| 6. |
- Yu, Kai, et al.
(författare)
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Measurement Analysis of NLOS Indoor MIMO Channels
- 2001
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Ingår i: Proceedings IST Mobile Communications Summit. ; , s. 277-282
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, we present results from measurements conducted by the University of Bristol.We study the channel characteristics of Multiple-Input-Multiple-Output (MIMO) indoor channel at 5.2GHz. Our investigation shows that the envelope of the channel for non-line-of-sight (NLOS) indoorsituations is approximately Rayleigh distributed and consequently we focus on a statistical descriptionof the first and second order moments of the narrowband MIMO channel. Furthermore, it is shown thatfor NLOS indoor scenarios, the MIMO channel covariance matrix can be well modeled by a Kroneckerproduct of the covariance matrices describing the correlation at the transmitter and the receiver siderespectively. A statistical narrowband model for the NLOS indoor MIMO channel based on thiscovariance structure is presented along with some simulation results.
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| 7. |
- Yu, Kai, et al.
(författare)
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Narrowband MIMO Channel Modeling for LOS Indoor Scenarios
- 2002
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Ingår i: Proceedings XXVIIth Triennial General Assembly of the International Union of Radio Science (URSI).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Herein, a line-of-sight (LOS) multiple input multiple output (MIMO) channel model is presented based on 5.2 GHzindoor MIMO channel measurements. The signal from the dominant direction is estimated and removed from the channel data. The residual part is shown to be Rayleigh distributed and its covariance matrix can be well approximated by theKronecker product of the covariance matrices seen from the transmitter and receiver respectively. Therefore we model the whole narrowband LOS indoor MIMO channel as a static rank one matrix plus a statistical model based on Rayleigh distribution with a multiplicative covariance structure.
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| 8. |
- Yu, Kai, et al.
(författare)
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On The Error of Kronecker Structure Based MIMO Channel Model
- 2004
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Ingår i: Proceedings of Nordic Radio Symposium, NRS 2004.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Herein, we investigate the mismatch of the Kronecker structure based MIMO channel model. Finding the minimum mismatch is trivial and the result is always 0. The maximization problem, on the other hand, is not convex in general. Therefore we combine semidefinite programming with a grid search, to find a lower bound of the maximum mismatch. Numerical examples show that the bound is tight even for moderate number of points in the grid. The resulting worst case model error, is much larger than the model error previously observed in measurement campaigns, which confirms that the channel correlation matrix can, indeed, be well approximated by the Kronecker product of the correlation matrices at the transmitter and receiver for the measured NLOS indoor scenarios.
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