| 1. |
- Carlemalm, Catharina, et al.
(författare)
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Algorithms for time delay estimation using a low complexity exhaustive search
- 1999
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Ingår i: IEEE Transactions on Automatic Control. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9286 .- 1558-2523. ; 44:5, s. 1031-1037
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Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the problem of time-delay estimation. Two new algorithms for time-delay estimation are developed and analyzed. The suggested methods combine an exhaustive search with a low complexity. Consequently, the problems with local minima of gradient search algorithms are avoided. The receiver operating characteristics (ROC) are computed, and together with simulation results these verify the performance of the estimation schemes.
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| 2. |
- Carlemalm, Catharina, et al.
(författare)
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Detection and Discrimination of Double Talk and Echo Path Changes in a Telephone Channel
- 1998
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Ingår i: Signal Analysis and Prediction. - : Springer. - 0817640428 - 9780817640422 ; , s. 407-418
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- It is important to detect a change in the echo path quickly but not confuse it with double talk, since the echo canceler should react differently for these two phenomena. In this chapter, a sequential detection scheme is presented and, based on model assumptions, the maximum a posteriori probabilities of the occurrence of double talk and abrupt changes in the echo path are derived. By utilizing the fact that the most active part of a typical impulse response of a telephone channel is short and by using a low complexity time-delay estimation algorithm to find these most active taps and not estimating the rest of the taps, low computational complexity of the proposed detection method is achieved. The scheme is veried experimentally in computer simulations using a real speech signal and impulse responses created from measured impulse responses from real hybrids of a telephone channel.
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| 3. |
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| 4. |
- Carlemalm, Catharina, et al.
(författare)
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On the problem of blind equalization considering abrupt changes in the channel characteristics
- 2015
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Ingår i: European Signal Processing Conference. - : European Signal Processing Conference, EUSIPCO.
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Konferensbidrag (refereegranskat)abstract
- The problem of blind equalization in a digital communication system is considered. Unfortunately, the circuit might suffer from abrupt changes. Thus, it is critical not to ignore this phenomenon when the problem of blind equalization is analyzed. The proposed method, which is based on an Ito stochastic differential calculus approach, describes the dynamics of the output signal with an infinite impulse response (IIR) model where the involved taps are modeled as time-varying cadlag (con-tinu a droite limites a gauche) processes. Therefore, nonlinear and time-variant changes in the channel characteristics are included.
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| 5. |
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| 6. |
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| 7. |
- Carlemalm, Catharina, et al.
(författare)
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On the Problem of Detection and Discrimination of Double Talk and Change in the Echo Path
- 1995
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The problem of detection and discrimination of double talk and change in the echo path in a telephone channel is considered. The phenomenon echo path change requires fast adaptation of the channel model to be able to equalize the echo dynamics. On the other hand, the adaption rate should be reduced when double talk occurs. Thus, it is critical to quickly detect a change in the echo path while not confusing it with double talk, which gives a similar effect. The proposed likelihood based approach compares a global channel model with a local one over a sliding window, both estimated with the recursive least squares algorithm.
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| 8. |
- Gustafsson, Fredrik, et al.
(författare)
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MAP based schemes for detection of double talk and abrupt changes in the echo path for fading channels
- 1998
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Ingår i: Proceedings of the 9th European Signal Processing Conference. - 9607620070
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Konferensbidrag (refereegranskat)abstract
- An algorithm for discrimination and detection of the two phenomena double talk and abrupt changes in the echo path is proposed for fading channels. Being able to discriminate and detect these two phenomena is crucial since the echo canceler must react differently. The suggested detection scheme is based on a sequential detection approach. The communication channel is modeled as a randomly time-varying linear system. An autoregressive model is used to describe the time evolution of the channel taps. The channel parameters are identified using a Kalman filter coupled with a recursive least squares algorithm, and, based on model assumptions, the maximum a posteriori probabilities corresponding to double talk and abrupt echo path changes are calculated. The proposed scheme is verified experimentally by way of computer simulations.
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| 9. |
- Gustafsson, Fredrik, et al.
(författare)
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On the Problem of Detection and Discrimination of Double Talk and Change in the Echo Path
- 1996
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Ingår i: Proceedings of the 1996 IEEE International Conference on Acoustics, Speech and Signal Processing. - 0780331923 ; , s. 2742-2745 vol.5
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Konferensbidrag (refereegranskat)abstract
- The problem of detection and discrimination of double talk and change in the echo path in a telephone channel is considered. The phenomenon echo path change requires fast adaptation of the channel model to be able to equalize the echo dynamics. On the other hand, the adaption rate should be reduced when double talk occurs. Thus, it is critical to quickly detect a change in the echo path while not confusing it with double talk, which gives a similar effect. The proposed likelihood based approach compares a global channel model with a local one over a sliding window, both estimated with the recursive least squares algorithm.
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| 10. |
- Logothetis, Catharina Carlemalm, et al.
(författare)
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Joint Channel and velocity estimation
- 2007
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Ingår i: 2007 IEEE international conference on networking, sensing and control, vols 1 and 2. ; , s. 781-786
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Konferensbidrag (refereegranskat)abstract
- An allgorithm for jointly tracking the Rayleigh fading channel and the mobile velocity is presented. The proposed scheme is based on the Interacting Multiple Model (IMM) Algorithm. The IMM utilizes a bank of Kalman filter, each matched to a specific mobile velocity, and the output of the filters are linearly combined based on the instantaneous likelihood of the velocity-models. The proposed scheme allows the tracking of abrupt changes in the mobile velocity even in very low SNR environments.
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