| 1. |
- Andersson, Sören, et al.
(författare)
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An adaptive array for mobile communication systems
- 1991
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Ingår i: IEEE Transactions on Vehicular Technology. - Toronto, Ont, Can : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9545 .- 1939-9359. ; 40:1 pt 2, s. 230-236, s. 3289-3292
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Tidskriftsartikel (refereegranskat)abstract
- The use of adaptive antenna techniques to increase the channel capacity is discussed. Directional sensitivity is obtained by using an antenna array at the base station, possibly both in receiving and transmitting modes. A scheme for separating several signals at the same frequency is proposed. The method is based on high-resolution direction-finding followed by optimal combination of the antenna outputs. Comparison with a method based on reference signals is made. Computer simulations are carried out to test the applicability of the technique to scattering scenarios that typically arise in urban areas. The proposed scheme is found to have great potential in rejecting cochannel interference, albeit at the expense of high computational requirements.
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| 2. |
- Doherty, Patrick, 1957-, et al.
(författare)
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Fuzzy if-then-unless rules and their implementation.
- 1992
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Ingår i: International Conference on Information Processing and Management of Uncertainty in Knowledge-Based Systems, IPMU92,1992. - Linköping, Sweden : Springer.
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Konferensbidrag (refereegranskat)
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| 3. |
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| 4. |
- Wahlberg, Bo, et al.
(författare)
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Robust Signal Parameter Estimation in the Presence of Array Perturbations
- 1991
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Ingår i: Proc. of 1991 International Conference on Acoustics, Speech, and Signal Processing, 1991. ICASSP-91.. - Linköping : IEEE. ; , s. 3277-3280
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Konferensbidrag (refereegranskat)abstract
- Signal parameter estimators which are less sensitive to perturbations in the array manifold are presented. A parametrized stochastic model for the array uncertainties is introduced. The unknown array parameters can include the individual gain and phase responses of the sensors as well as their positions. Based on this model, a maximum a posteriori (MAP) estimator is formulated. This results in a fairly complex optimization problem which is computationally expensive. The MAP estimator is simplified by exploiting properties of the weighted subspace fitting method. An approximate method that further reduces the complexity is also presented, assuming smallarray perturbations. A compact expression for the MAP Cramer-Rao bound (CRB) on the signal and arrayparameter estimates is derived. A simulation study indicates that the proposed robust estimation procedures achieve the MAP-CRB even for moderate sample sizes.
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| 5. |
- Ljung, Lennart, 1946-, et al.
(författare)
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Adaptive System Performance in the Frequency Domain
- 1992
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Ingår i: Adaptive systems in control and signal processing 1992. - Linköping : Linköping University. - 9780080425962 ; , s. 33-40
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Konferensbidrag (refereegranskat)
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| 6. |
- Akçay, Hüseyin, et al.
(författare)
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On the Choice of Norms in System Identification
- 1994
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Ingår i: Proceedings of the 10th IFAC Symposium on System Identification. - Linköping : Linköping University. - 9780080422251 ; , s. 103-108
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this paper we discuss smooth and sensitive norms for prediction error system identification when the disturbances are magnitude bounded. Formal conditions for sensitive norms, which give an order of magnitude faster convergence of the parameter estimate variance, are developed. However, it also is shown that the parameter estimate variance convergence rate of sensitive norms is arbitrarily bad for certain distributions. A necessary condition for a norm to be statistically robust with respect to the family F(C) of distributions with support [-C, C] for some arbitrary C>0 is that its second derivative does not vanish on the support. A direct consequence of this observation is that the quadratic norm is statistically robust among all lp-norms, p⩽2<∞ for F(C).
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| 7. |
- Akçay, Hüseyin, et al.
(författare)
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The Least-Squares Identification of FIR Systems Subject to Worst-Case Noise
- 1994
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Ingår i: Proceedings of the 10th IFAC Symposium on System Identification. - Linköping : Linköping University. - 9780080422251 ; 23:5, s. 329-338
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The least-squares identification of FIR systems is analyzed assuming that the noise is a bounded signal and the input signal is a pseudo-random binary sequence. A lower bound on the worst-case transfer function error shows that the least-square estimate of the transfer function diverges as the order of the FIR system is increased. This implies that, in the presence of the worst-case noise, the trade-off between the estimation error due to the disturbance and the bias error (due to unmodeled dynamics) is significantly different from the corresponding trade-off in the random error case: with a worst-case formulation, the model complexity should not increase indefinitely as the size of the data set increases.
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| 8. |
- Andersson, Torbjörn, et al.
(författare)
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Estimation of Residence Time in Continuous Flow Systems with Dynamics
- 1994
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Ingår i: Proceedings of the 10th IFAC Symposium on System Identification. - Linköping : Linköping University. ; , s. 401-406
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Konferensbidrag (refereegranskat)abstract
- A method for estimation of residence time in continuous flow systems with varying dynamics is presented. By resampling, i.e., choosing time instants different from the given sampling instants, and interpolation between measured data points, we obtain a continuous flow system with constant residence time expressed in the new resampled time vector. We assume the flow patterns in the systems are invariant. The new data set is then used for identification of parameters in a chosen model structure. From the identified model, the residence time is readily calculated and a procedure for that is briefly described. The presented method is readily extended to enable use in recursive identification. In that case, however, as an improvement of tracking ability of an ordinary recursive routine.
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| 9. |
- Forsman, Krister
(författare)
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An Algorithm for Finding Periodic Solutions to Systems of Nonlinear Difference Equations
- 1991
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Ingår i: Proceedings of the 30th IEEE Conference on Decision and Control. - Linköping : Linköping University. - 0780304500 ; , s. 2889-2990 vol.3
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Konferensbidrag (refereegranskat)abstract
- An algorithm for finding all N-periodic solutions to systems of nonlinear difference equations is given. The algorithm is based on elimination theory, and in special Gröbner bases. It is applicable to polynomial systems and can handle indeterminate parameters in the system equations. The system is not required to be in state space form; implicit equations are allowed.
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| 10. |
- Forsman, Krister
(författare)
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Construction of Lyapunov Functions Using Gröbner Bases
- 1991
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Ingår i: Proceedings of the 30th IEEE Conference on Decision and Control. - Linköping : Linköping University. - 0780304500 ; , s. 798-799 vol.1
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this paper we show how so called Grobner bases can be used when choosing parameters in Lyapunov functions for nonlinear dynamical systems in an optimal way. The method suggested requires the nonlinearities of the system and the Lyapunov function to be of polynomial type. Some concrete examples of how to apply the method is provided.
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