| 61. |
- Dahl, Mattias, et al.
(författare)
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Design of antenna array using dual nested complex approximation
- 2005
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Konferensbidrag (refereegranskat)abstract
- This paper presents a new practical approach to complex Chebyshev approximation by semi-infinite linear programming. By the new front-end technique, the associated semi-infinite linear programming problem is solved exploiting the finiteness of the related Lagrange multipliers by adapting finite-dimensional linear programming to the dual semi-infinite problem, and thereby taking advantage of the numerical siability and efficiency of conventional linear programming software packages. Furthermore, the optimization procedure is simple to describe theoretically and straightforward to implement in computer coding. The new design technique is therefore. highly accessible. The algorithm is formally introduced as the linear Dual Nested Complex Approximation (DNCA) algorithm. The DNCA algorithm is versatile and can be applied to a variety of applications such as narrow-band as well as broad-band beamformers with any geometry, conventional Finite Impulse Response (FIR) filters, analog and digital Laguerre networks. and digital FIR equalizers. The proposed optimization technique is applied to several numerical examples dealing with the design of a narrow-band base-station antenna array for mobile communication.
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| 62. |
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| 63. |
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| 64. |
- Dahl, Mattias, et al.
(författare)
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Simultaneous Echo Cancellation and Car Noise Suppression Employing a Microphone Array
- 1997
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Konferensbidrag (refereegranskat)abstract
- This paper presents a method to simultaneously perform 20 dB acoustic echo cancellation and 15-20 dB speech enhancement using an adaptive microphone array combined with spectral subtraction. Primarily intended for handsfree telephones in automobiles, the microphone array system simultaneously emphasizes the near-end talker and suppresses the handsfree loudspeaker and the broadband car noise. The array system is based on a fast and efficient on-site calibration and can be used in other situations such as conventional speaker phones.
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| 65. |
- Erman, Maria
(författare)
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Applications of Soft Computing Techniques for Wireless Communications
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents methods and applications of Fuzzy Logic and Rough Sets in the domain of Telecommunications at both the network and physical layers. Specifically, the use of a new class of functions, the truncated π functions, for classifying IP traffic by matching datagram size histograms is explored. Furthermore, work on adapting the payoff matrix in multiplayer games by using fuzzy entries as opposed to crisp values that are hard to quantify, is presented.Additionally, applications of fuzzy logic in wireless communications are presented, comprised by a comprehensive review of current trends and applications, followed by work directed towards using it in spectrum sensing and power control in cognitive radio networks.This licentiate thesis represents parts of my work in the fields of Fuzzy Systems and Wireless Communications. The work was done in collaboration between the Departments of Applied Signal Processing and Mathematics at Blekinge Institute of Technology.
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| 66. |
- Fundin, Per, et al.
(författare)
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Minimal Aliasing Subband System Identification
- 2001
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Konferensbidrag (refereegranskat)abstract
- Subband adaptive filters have been proposed to avoid the drawbacks of slow convergence and high computational complexity associated with time domain adaptive filters. While the computational complexity is reduced, other undesired properties, such as signal delays and signal aliasing, are introduced. Aliasing effects may result in loss of perception in speech applications. A method for the design of oversampled filter banks is proposed to reduce these effects. The design method aims at reducing the inband aliasing as well as the reconstruction aliasing for the reason of achieving robustness when weighting in the subbands alters the subband signal phase and magnitude.
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| 67. |
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| 68. |
- Grbic, Nedelko, et al.
(författare)
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A New Pilot-Signal based Space-Time Adaptive Algorithm
- 2001
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Konferensbidrag (refereegranskat)abstract
- In the application of adaptive antenna arrays to wireless communications, a known pilot signal sequence may be used for estimating the array response at the beginning of each data frame. This pilot sequence is usually very short and conventional training methods which estimate the array response, based solely on this training sequence, may incur large estimation errors. In this paper, we propose an online modified weighted recursive least squares type of training algorithm for estimating the optimal array response by exploiting information from the whole frame of the received signal. The benefits of the proposed algorithm is that tracking of coherent noise and interference signals is substantially improved, and the overall performance is increased. Simulation results show that the proposed method offers substantial improvement when compared to the conventional least squares method.
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| 69. |
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| 70. |
- Grbic, Nedelko, et al.
(författare)
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Acoustic Echo Cancelling and Noise Suppression with Microphone Arrays
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report presents a method to achieve acoustic echo canceling and noise suppression using microphone arrays. The method employs a digital self-calibrating microphone system. The on-site calibration process is a simple indirect calibration which adapts in each specific case to the environment and the electronic equipment used. The method also continuously reduces environmental disturbances such as car engine noise and fan noise. The method is primarily aimed at hands free mobile telephones by suppressing the hands free loudspeaker and car cabin noise simultaneously. The report also contains an evaluation of the impact of echo and noise suppression on a real conversation, accomplished in a car using a microphone array.
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