| 1. |
- Mowlér, Marc, et al.
(författare)
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Joint estimation of mutual coupling, element factor, and phase center in antenna arrays
- 2007
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Ingår i: EURASIP Journal on Wireless Communications and Networking. - : Springer Science and Business Media LLC. - 1687-1472 .- 1687-1499. ; 2007:1, s. 030684-
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Tidskriftsartikel (refereegranskat)abstract
- A novel method is proposed for estimation of the mutual coupling matrix of an antenna array. The method extends previous work by incorporating an unknown phase center and the element factor (antenna radiation pattern) in the model, and treating them as nuisance parameters during the estimation of coupling. To facilitate this, a parametrization of the element factor based on a truncated Fourier series is proposed. The performance of the proposed estimator is illustrated and compared to other methods using data from simulations and measurements, respectively. The Cramer-Rao bound (CRB) for the estimation problem is derived and used to analyze how the required amount of measurement data increases when introducing additional degrees of freedom in the element factor model. We find that the penalty in SNR is 2.5 dB when introducing a model with two degrees of freedom relative to having zero degrees of freedom. Finally, the tradeoff between the number of degrees of freedom and the accuracy of the estimate is studied. A linear array is treated in more detail and the analysis provides a specific design tradeoff.
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| 2. |
- Mowlér, Marc, et al.
(författare)
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Methods and bounds for antenna array coupling matrix estimation
- 2007
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Ingår i: 2007 IEEE International Conference on Acoustics, Speech, and Signal Processing. - : IEEE. - 1424407273 - 1424407281 ; , s. 881-884
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Konferensbidrag (refereegranskat)abstract
- A novel method is proposed for estimation of the mutual coupling matrix of an antenna array. The method extends previous work by incorporating an unknown phase center and the element factor (antenna radiation pattern) in the model, and treating these as nuisance parameters during the estimation of coupling. To facilitate this, a parametrization of the element factor based on a truncated Fourier series is proposed. The Cramer-Rao bound (CRB) for the estimation problem is derived and used to analyze how the required amount of measurement data increases when introducing a more and more flexible model for the element factor. Finally, the performance of the proposed estimator is illustrated using data from measurements on an 8-element antenna array.
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| 3. |
- Astély, David, et al.
(författare)
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Spatio-Temporal Interference Rejection Combining
- 2005
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Ingår i: Smart Antennas - State-of-the-Art. - : Hindawi Publishing Corporation. - 9775945097 ; , s. 5-26
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Bergman, Svante, 1979-, et al.
(författare)
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Adaptive spatial bit loading using imperfect channel state information
- 2005
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Ingår i: Proceedings of International Workshop on Optical and Electronic Device Technology for Access Networks, Aalborg, Denmark.
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Konferensbidrag (refereegranskat)abstract
- Using information about the channel at the transmitter can improve the performance of multi-input multi-output (MIMO) communication systems. When perfect channel state information (CSI) is available, data can be multiplexed and optimized over independent spatial channels. When the available channel information is imperfect or partial, crosstalk between the spatial channels is inevitable complicating the design since the performance of the spatial streams has to be considered jointly. In this paper an efficient algorithm for bit and power loading on the spatial channels is presented. Focus is on maximizing the data rate at fixed bit error rate and reasonable computational complexity.
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| 5. |
- Bergman, Svante, 1979-, et al.
(författare)
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Design of robust linear dispersion codes based on imperfect
- 2006
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Ingår i: Proceedings European Signal Processing Conference.
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Konferensbidrag (refereegranskat)abstract
- This paper concerns the design of codes for multiple-input multiple-output communication systems. The transmission scheme utilizes imperfect channel state information (CSI) in the design, assuming that maximum-likelihood detection is employed at the receiver. It is argued that channel diagonalizing codes are not robust to imperfections in the CSI. A robust non-diagonalizing code with good minimum distance separation between received codewords is proposed. The design is very suitable for systems operating at high data rates since the complexity scales nicely with the number of antennas. Numerical results show that the proposed code outperforms a state-of-the-art diagonalizing precoder.
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| 6. |
- Bergman, Svante, 1979-, et al.
(författare)
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Joint Bit Allocation and Precoding for MIMO Systems With Decision Feedback Detection
- 2009
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Ingår i: IEEE Transactions on Signal Processing. - : IEEE. - 1053-587X .- 1941-0476. ; 57:11, s. 4509-4521
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers the joint design of bit loading, precoding and receive filters for a multiple-input multiple-output (MIMO) digital communication system employing decision feedback (DF) detection at the receiver. Both the transmitter as well as the receiver are assumed to know the channel matrix perfectly. It is well known that, for linear MIMO transceivers, a diagonal transmission (i.e., orthogonalization of the channel matrix) is optimal for some criteria. Surprisingly, it was shown five years ago that for the family of Schur-convex functions an additional rotation of the symbols is necessary. However, if the bit loading is optimized jointly with the linear transceiver, then this rotation is unnecessary. Similarly, for DF MIMO optimized transceivers a rotation of the symbols is sometimes needed. The main result of this paper shows that for a DF MIMO transceiver where the bit loading is jointly optimized with the transceiver filters, the rotation of the symbols becomes unnecessary, and because of this, also the DF part of the receiver is not required. The proof is based on a relaxation of the available bit rates on the individual substreams to the set of positive real numbers. In practice, the signal constellations are discrete and the optimal relaxed bit loading has to be rounded. It is shown that the loss due to rounding is small, and an upper bound on the maximum loss is derived. Numerical results are presented that confirm the theoretical results and demonstrate that orthogonal transmission and the truly optimal DF design perform almost equally well.
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| 7. |
- Bergman, Svante, 1979-, et al.
(författare)
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Lattice based linear precoding for MIMO block codes
- 2007
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Ingår i: 2007 IEEE International Conference on Acoustics, Speech, and Signal Processing. - : IEEE. - 1424407281 - 1424407273 ; , s. 329-332
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Konferensbidrag (refereegranskat)abstract
- Herein, the design of linear dispersion codes for block based multiple-input multiple-output communication systems is investigated. The receiver as well as the transmitter are assumed to have perfect knowledge of the channel, and the receiver is assumed to employ maximum likelihood detection. We propose to use linear precoding and lattice invariant operations to transform the channel matrix into a lattice with large coding gain. With appropriate approximations, it is shown that this corresponds to selecting lattices with good sphere packing properties. Lattice invariant transformations are then used to minimize the power consumption. An algorithm for this power minimization is presented along with a lower bound on the optimization. Numerical results indicate that there is a potential gain of several dB by using the method compared to channel inversion with adaptive bit loading.
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| 8. |
- Bergman, Svante, 1979-, et al.
(författare)
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Lattice-based linear precoding for MIMO channels with transmitter CSI
- 2008
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Ingår i: IEEE Transactions on Signal Processing. - : IEEE. - 1053-587X .- 1941-0476. ; 56:7, s. 2902-2914
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Tidskriftsartikel (refereegranskat)abstract
- Herein, the design of linear dispersion codes for multiple-input multiple-output communication systems is investigated. The receiver as well as the transmitter are assumed to have perfect knowledge of the channel, and the receiver is assumed to employ maximum likelihood detection. We propose to use linear precoding and lattice invariant operations to transform the channel matrix into a lattice generator matrix with large minimum distance separation. With appropriate approximations, it is shown that this corresponds to selecting lattices with good sphere-packing properties. Lattice invariant transformations are then used to minimize the power consumption. An algorithm for this power minimization is presented along with a lower bound on the optimization. Numerical results indicate significant gains by using the proposed method compared to channel diagonalization with adaptive bit loading.
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| 9. |
- Bergman, Svante, 1979-, et al.
(författare)
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Optimal Bit Loading for MIMO Systems with Decision Feedback Detection
- 2009
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Ingår i: 2009 IEEE Vehicular Technology Conference. - : IEEE. - 9781424425167 ; , s. 831-835
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Konferensbidrag (refereegranskat)abstract
- This paper considers the joint design of bit loading, precoding and receive filters for a multiple-input multiple-output (MIMO) digital communication system employing decision feedback (DF) detection at the receiver. Both the transmitter as well as the receiver are assumed to know the channel matrix perfectly. It is well known that, for linear MIMO transceivers, a diagonal transmission (i.e., orthogonalization of the matrix channel) is optimal for some criteria. Surprisingly, it was shown five years ago that for the family of Schur-convex functions an additional rotation of the symbols is necessary. However, if the bit loading is optimized jointly with the linear transceiver, then the rotation is unnecessary. Similarly, for DF MIMO transceivers, a rotation of the symbols is sometimes needed. The main result of this paper shows that for a DF MIMO transceiver where the bit loading is jointly optimized with the transceiver filters, the rotation of the symbols becomes unnecessary and, consequently, also the DF part of the receiver is not required.
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| 10. |
- Bergman, Svante, 1979-, et al.
(författare)
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Spatial multiplexing over Rician fading channels : Linear precoding transmission strategies
- 2005
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Ingår i: Nordic Conference on Radio Science and Communications (RVK).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Using information about the channel at the transmittercan improve the performance of multi-input multi-output(MIMO) communication systems. When perfect channelstate information (CSI) is available, data can be multiplexed and optimized over independent spatial channels.However, when the available channel information is imperfect or partial, crosstalk between the spatial channels isinevitable complicating the design of the transmitted data.This paper extends our earlier work on practical bit andpower loading algorithmsthat enable the use of partial CSIfor spatial multiplexing, to the case of correlated Ricianfading CSI models. Furthermore, the bit and power loading algorithm is updated for improved BER performanceas well as lower computational complexity.
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