| 1. |
- Almers, Peter, et al.
(författare)
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Exercises
- 2005
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Ingår i: Wireless Communications. - 9780470848883 - 047084888X - 0470848871 ; , s. 561-593
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Bizjajeva, Svetlana, et al.
(författare)
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Mobile positioning in MIMO system using particle filtering
- 2007
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Ingår i: 2007 IEEE 66TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5. - 1090-3038. - 9781424402632 ; , s. 792-798
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Konferensbidrag (refereegranskat)abstract
- his paper represents the results of a simulation study on positioning of a mobile unit in MIMO settings. We used two different approaches for modeling the mobile movement, combined with a simple geometrical model for the MIMO channel. Three different particle filters were implemented for the position estimation. The results show that all three filters are able to achieve estimation accuracy required by Federal Communication Commission. The dimensionality of the particle filter state space is independent of the number of antenna elements, and it is possible to increase the number of antennas and use more sophisticated channel models without changing the filtering algorithms.
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| 3. |
- Florén, Fredrik, et al.
(författare)
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Dependence of the mean SNR on the interaction between multiuser diversity, multipath diversity, and feedback delay
- 2005
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Ingår i: 2005 IEEE 61st Vehicular Technology Conference. VTC2005- Spring. - 0780388879 ; , s. 1898-1902
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Konferensbidrag (refereegranskat)abstract
- We examine wireless systems employing Rake receivers and fast scheduling over multiple users. The interactions between multipath diversity, multiuser diversity, and the feedback delay are investigated in terms of the mean signal-to-noise ratio (SNR). It is assumed that all users experience the same propagation characteristics, i.e., the same number of taps and power-delay profile (PDP). The results are exact as well as asymptotic (in the number of users) expressions that quantify this interaction. It is found that as the number of taps in the channel increases, the multiuser diversity gain decreases but better robustness against feedback delay is achieved. Furthermore, the asymptotic results derived show good agreement with the exact results for an exponential PDP, even for few users. Thus, we obtain expressions for the mean SNR that are compact and easy to evaluate
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| 4. |
- Foroughi, Farzad, et al.
(författare)
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Channel estimation for a Mobile Terminal in a Multi-Standard Environment (LTE and DVB-H)
- 2009
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Ingår i: 3rd International Conference on Signal Processing and Communication Systems, 2009. ICSPCS 2009.. - 9781424444731 ; , s. 67-75
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Konferensbidrag (refereegranskat)abstract
- In this paper. we present an analysis of different channel estimator structures that can be used and efficiently implemented with minor configuration changes of a common hardware for both LTE and DVB-H Such common estimator structures for LTE and DVB-H allow algorithm and hardware reuse when both standards are implemented on the same platform. In this approach, a core estimator will be utilized to address parameter estimation for the two standards. The estimators exploit similarities in pilot patterns between LTE and DVB-H. The estimation techniques are discussed taking both algorithm and complexity issues into account.
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| 5. |
- Garcia, MJF, et al.
(författare)
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Peak power reduction for OFDM systems with orthogonal pilot sequences
- 2006
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276. ; 5:1, s. 47-51
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a novel peak-to-average power reduction approach for orthogonal frequency division multiplexing (OFDM) has been addressed. Two-dimensional pilot-symbol assisted modulation (2D-PSAM) is employed in coherent OFDM for channel estimation, and it is based on inserting known symbols spread throughout the 2D time-frequency grid. These pilot symbols are employed to simultaneously perform distortionless peak power reduction with a suboptimum technique named orthogonal pilot sequences (OPS), which reduces additional system complexity and side information compared to optimum pilot values. This proposal attains a further step over other previous works, since this set of sequences allows blind detection at the receiver without prior knowledge of any side information.
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| 6. |
- Hammarberg, Peter, et al.
(författare)
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A comparison of DFT and SVD based channel estimation in MIMO OFDM systems
- 2006
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Ingår i: 2006 IEEE 17th International Symposium on Personal, Indoor and Mobile Radio Communications (IEEE Cat. No. 06TH8881). - 1424403294
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Konferensbidrag (refereegranskat)abstract
- In this paper two simplified transform based estimators for MIMO OFDM systems using the DFT and an SVD based transform are compared over a tapped delay line channel model. In the resulting symbol error rate plots, it is seen that the DFT based estimator experiences an error floor caused by the mismatch between the discrete time model and a continuous time reality. This error floor becomes a problem at high SNR levels where high data-rate systems can be expected to operate. When using an SVD based estimator it is seen that this error floor is reduced at the cost of a somewhat increased estimator complexity
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| 7. |
- Hammarberg, Peter, et al.
(författare)
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EXIT chart evaluation of a receiver structure for multi-user multi-antenna OFDM systems
- 2009
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Ingår i: Proc. IEEE Global Telecommunications Conference (GLOBECOM) 2009. - 9781424441488 ; , s. 2402-2407
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Konferensbidrag (refereegranskat)abstract
- In this paper we evaluate, by means of Extrinsic Information Transfer (EXIT) charts, an iterative receiver that has emerged as a promising candidate for non-coherent multi-user multi-antenna OFDM systems. The receiver performs parallel interference cancellation (followed by linear filtering) and channel estimation, using soft symbols obtained from a bank of single-user decoders. For the sake of conceptual clarity we study a system with two single antenna users and a receiver with two antennas, and we demonstrate how the convergence behavior of the receiver can be visualized using paired three dimensional EXIT surfaces. Our results show that the actual decoder trajectories obtained through simulations are well predicted from the EXIT charts. For the iterative receiver under investigation we identify a very specific problem with EXIT chart generation; the EXIT curve for the inner component decoder depends on the outer encoder. To handle this problem we propose a modification to the iterative receiver which solves the aforementioned problem; the performance degradation is demonstrated to be small.
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| 8. |
- Hammarberg, Peter, et al.
(författare)
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On the performance of iterative receivers for interfering MIMO-OFDM systems in measured channels
- 2008
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Ingår i: 42nd Asilomar Conference on Signals, Systems and Computers. - 1058-6393. - 9781424429400 ; , s. 141-145
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Konferensbidrag (refereegranskat)abstract
- This paper investigates the gains harvested through base station cooperation in the up-link for a multi-user (MU) Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) system, operating in a real indoor environment. The base stations perform joint detection using an iterative receiver that carries out multi-user detection and channel estimation via soft information from the single-user decoders. Performance evaluation is carried out using real channels from an indoor dynamic dual MIMO link measurement campaign. The measured scenario represent a real life situation where two users communicate with two base stations, each with two antennas, in an environment resembling a shopping mall or an airport terminal. System performance is evaluated in terms of both Bit-Error Rate (BER) vs. Signal-to-Interference Ratio (SIR) and Cumulative Distribution Functions (CDF) for the instantaneous BER. Also, the impact of using soft information in the channel estimation is analyzed.
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