| 11. |
- Moebus, Marco, et al.
(författare)
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Parameterization of Acoustic Signatures in Ultrasound Images for the Detection of Human Presence by Autonomous Vehicles
- 2010
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Ingår i: Proceedings of ICASSP 2010.
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Konferensbidrag (refereegranskat)abstract
- We address the problem of human detection for autonomousvehicles. Instead of using an optical system, we propose toemploy an acoustic 2D array to reliably obtain an image of ahuman in a 3D spatial power spectrum which is independentof lighting conditions and uses cheap ultrasound sensors.We show that humans have a distinct acoustic signature andpropose to model the echoes from reflecting parts of objectsin the scene by a Gaussian-Mixture-Model. When the model is fitted to the acoustic image, it is straightforward toobtain geometric relations between the present echoes andrepresent the acoustic signatures in a low-dimensional parameter space. We present results based on real data measurements that demonstrate that different objects can be reconstructed from the data and discriminated. The obtainedparameter space can then be the basis for subsequent detection and classification of humans.
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| 12. |
- Moebus, M., et al.
(författare)
-
Parametrization of acoustic images for the detection of human presence by mobile platforms
- 2010
-
Ingår i: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings. - 1520-6149. - 9781424442966 ; , s. 3538-3541
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We address the problem of human detection with mobile platforms such as robots. Instead of using an optical system, we propose to employ an acoustic 2D array to reliably obtain an image of a human in a 3D spatial power spectrum which is independent of lighting conditions and uses cheap acoustic sensors. We show that humans have a distinct acoustic signature and propose to model the echoes from reflecting parts of objects in the scene by a Gaussian-Mixture- Model. When it is fitted to the acoustic image, we can extract geometric relations between the present echoes and represent the acoustic signatures in a low-dimensional parameter space. We present results based on real data measurements that demonstrate that different objects can be reconstructed from the data and discriminated. The obtained parameter space forms the basis for subsequent detection and classification of humans. ©2010 IEEE.
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| 13. |
- Owrang, Arash, 1979, et al.
(författare)
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A new method to compute optimal periodic sampling patterns
- 2011
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Ingår i: 2011 Digital Signal Processing and Signal Processing Education Meeting, DSP/SPE 2011 - Proceedings. - 9781612842271 ; , s. 259-264
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- It is possible to reconstruct a signal from cyclic nonuniform samples and thus take advantage of a lower sampling rate than the Nyquist rate. However, this has the potential drawback of amplifying signal perturbations, e.g. due to noise and quantization. We propose an algorithm based on sparse reconstruction techniques, which is able to find the sparsest sampling pattern that permits perfect reconstruction of the sampled signal. The result of our algorithm with a proper constraint values is a sparse subset of samples that results in an ideal condition number for its equivalent sub-DFT matrix. Besides, our algorithm has low complexity in terms of computation. The method is illustrated by simulations for a sparse multi band signal.
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| 14. |
- Panahi, Ashkan, 1986, et al.
(författare)
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Fast LASSO based DOA tracking
- 2011
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Ingår i: 4 th IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP), 2011. - 9781457721052 ; , s. 397-400
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a sequential, fast DOA tracking technique using the measurements of a uniform linear sensor array in the far field of a set of narrow band sources. Our approach is based on sparse approximation technique LASSO (Least Absolute Shrincage and Selection Operator), which has recently gained considerable interest for DOA and other estimation problems. Considering the LASSO optimization as a Bayesian estimation, we first define a class of prior distributions suitable for the sparse representation of the model and discuss its relation to the priors over DOAs and waveforms. Inspired by the Kalman filtering method, we introduce a nonlinear sequential filter on this family of distributions. We derive the filter for a simple random walk motion model of the DOAs. The method consists of consecutive implementation of weighted LASSO optimizations using each new measurement and updating the LASSO weights for the next step.
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| 15. |
- Panahi, Ashkan, 1986, et al.
(författare)
-
Maximum a Posteriori Based Regularization Parameter Selection
- 2011
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Ingår i: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings. - 1520-6149. - 9781457705397 ; , s. 2452-2455
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Konferensbidrag (refereegranskat)abstract
- The l(1) norm regularized least square technique has been proposed as an efficient method to calculate sparse solutions. However, the choice of the regularization parameter is still an unsolved problem, especially when the number of nonzero elements is unknown. In this paper we first design different ML estimators by interpreting the l(1) norm regularization as a MAP estimator with a Laplacian model for data. We also utilize the MDL criterion to decide on the regularization parameter. The performance of these new methods are evaluated in the context of estimating the Directions Of Arrival (DOA) for the simulated data and compared. The simulations show that the performance of the different forms of the MAP estimator are approximately equal in the one snapshot case, where MDL may not work. But for the multiple snapshot case both methods can be used.
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| 16. |
- Panahi, Ashkan, 1986, et al.
(författare)
-
On the resolution of the LASSO-based DOA estimation method
- 2011
-
Ingår i: Proceedings - 2011 International ITG Workshop on Smart Antennas, WSA 2011. - 9781612840741
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Konferensbidrag (refereegranskat)abstract
- This paper investigates the consistency of the LASSO-based DOA estimation of the narrow-band signals in infinitely high SNR. Such a method provides a robust and accurate approximation of the Maximum Likelihood estimation. However, as we show, unlike the standard techniques such as subspace methods the LASSO-based estimation is generally not consistent in high SNRs. In return, considering the true DOA's, we show that the method is consistent for certain configuration of the sources. This approach leads us to relate such a conditional consistency to the resolution concept. We next give a condition to verify the consistency of a given set of directions and simplify it to a computationally fast equivalent algorithm. The results show that the resolution in infinitely high SNR case for m sensors decreases by speed 1 over m.
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| 17. |
- Rashidi Avendi, Moslem, 1979, et al.
(författare)
-
A NLLS based sub-Nyquist rate Spectrum Sensing for Wideband Cognitive Radio
- 2011
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Ingår i: Fifth IEEE International Symposium on New Frontiers in Dynamic Spectrum Access Networks 2011(DySPAN 2011). - 9781457701788 ; , s. 545-551
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Konferensbidrag (refereegranskat)abstract
- For systems and devices, such as cognitive radio and networks, that need to be aware of available frequency bands, spectrum sensing has an important role. A major challenge in this area is the requirement of a high sampling rate in the sensing of a wideband signal. In this paper a wideband spectrum sensing method is presented that utilizes a sub-Nyquist sampling scheme to bring substantial savings in terms of the sampling rate. The correlation matrix of a finite number of noisy samples is computed and used by a NLLS estimator to detect the occupied and vacant channels of the spectrum. We provide an expression for the detection threshold as a function of sampling parameters and noise power. Also, a sequential forward selection algorithm is presented to find the occupied channels in a low complexity. The method can be applied to both correlated and uncorrelated wideband multichannel signals. A comparison with conventional energy detection using Nyquist-rate sampling shows that the proposed scheme can yield similar performance for SNR above 4 dB with a factor of 3 smaller sampling rate.
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| 18. |
- Rashidi Avendi, Moslem, 1979, et al.
(författare)
-
A Wideband Spectrum Sensing Method For Cognitive Radio Using Sub-Nyquist Sampling
- 2011
-
Ingår i: 2011 Digital Signal Processing and Signal Processing Education Meeting, DSP/SPE 2011 - Proceedings. - 9781612842271 ; , s. 30-35
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Konferensbidrag (refereegranskat)abstract
- Spectrum sensing is a fundamental component in cognitiveradio. A major challenge in this area is the requirement of a high sampling rate in the sensing of a wideband signal. In this paper a wideband spectrum sensing model is presented that utilizes a sub-Nyquist sampling scheme to bring substantial savings in terms of the sampling rate. The correlation matrix of a finite number of noisy samples is computed and used by a subspace estimator to detect the occupied and vacant channels of the spectrum. In contrast with common methods, the proposed method does not need the knowledge of signal properties that mitigates the uncertainty problem. We evaluate the performance of this method by computing the probability of detecting signal occupancy in terms of the number of samples and the SNR of randomly generated signals. The results show a reliable detection even in low SNR and small number of samples.
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| 19. |
- Rylander, Thomas, 1972, et al.
(författare)
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Reconstruction of metal protrusion on flat ground plane
- 2010
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Ingår i: IET Microwaves, Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1751-8725 .- 1751-8733. ; 4:11, s. 1746-1755
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Tidskriftsartikel (refereegranskat)abstract
- The authors present a gradient-based optimisation algorithm for the reconstruction of the shape of a metal protrusion on a flat ground plane based on the scattering matrix of an array antenna. The sensitivities are based on the continuum form of Maxwell's equations, which offers good flexibility with respect to the choice of field solver. The computational cost for the gradient is independent of the number of degrees of freedom that are used to represent the shape of the protrusion. Initial tests show that the sensitivities yield good accuracy in the 3D setting and that relatively good reconstructions of simple surfaces are feasible with a computational cost that amounts to about some ten evaluations of the scattering matrix.
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| 20. |
- Seifi, Nima, 1981, et al.
(författare)
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An Efficient Signaling for Multi-mode Transmission in Multi-user MIMO
- 2010
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Ingår i: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings. - 1520-6149. - 9781424442966 ; , s. 3402-3405
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Konferensbidrag (refereegranskat)abstract
- In this paper the downlink of a multi-user MIMO (MUMIMO)system with multi-mode transmission is considered.We propose a low-complexity algorithm for selecting usersand the corresponding number of data streams to each user,denoted as user transmission mode (UTM). The selectionis only based on the average received signal-to-noise ratio(SNR) from the base station (BS) for each user. This reducesthe overall amount of feedback for scheduling, as opposedto techniques that assume perfect instantaneous channelstate information (CSI) from all users. Analytical averagethroughput approximations are derived for each user at different UTMs. Simulation results demonstrate that the proposed algorithm provides performance close to dirty paper coding (DPC) with considerably reduced feedback.
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