Conference Papers

Energy efficient binary PPM/code-multiplexed transmitted-reference multi-user UWB system

M. Gufran Khan, B. Sällberg, J. Nordberg, I. Claesson IEEE International Conference on Ultra-Wideband, pp. 615-619, Sept. 2011 This paper presents a combined binary pulse position modulation (BPPM)/code-multiplexed transmitted-reference (CM-TR) ultra wideband (UWB) system. The low complexity CM-TR UWB is not energy efficient as one half of the energy is used to transmit reference pulses and, even at low-to-medium data rates, it suffers from strong multi-user interference (MUI) and inter-frame interference (IFI). Keeping the information rate constant, the combined BPPM/CM-TR…

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Modulation Domain Adaptive Gain Equalizer for Speech Enhancement

M. Shahid, R. Ishaq, B. Sällberg, N. Grbic, B. Lövström, I. Claesson IASTED International Conference on Signal and Image Processing and Applications, Aug. 2011 This paper evaluates speech enhancement by filtering in the modulation frequency domain, as an alternative to filtering in conventional frequency domain. Adaptive Gain Equalizer (AGE) is a commonly used single-channel speech enhancement algorithm. A recently introduced class of signal transformations called modulation transform has successfully made its place alongside classical time/frequency representations. This paper presents an…

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Non-coherent detection of impulse radio UWB signals based on fourth order statistics

M. G. Khan, B. Sällberg, J. Nordberg, I. Claesson IEEE International Conference on Ultra-Wideband, pp. 824-828, Oct. 2009 Non-coherent receivers are an attractive solution for impulse radio (IR) ultra wideband (UWB) systems due to their low-complexity implementation and low power consumption. However, low-complexity detection is achieved at the expense of some loss in performance. In this paper, a non-coherent detection scheme based on fourth order statistics, i.e., kurtosis is proposed for low data rate IR-UWB systems. The performance of a…

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Direction of Arrival Estimation for Speech Sources using Fourth Order Cross Cumulants

M. Swartling, B. Sällberg, N. Grbic IEEE International Symposium on Circuits and Systems, pp. 1696-1699, May 2008 In many applications where speech separation and enhancement is of interest, e.g. conferencing systems, mobile phones and hearing aids, accurate speaker localization is important. This paper presents an alternative criteria for the well known steered response power with phase transform (SRP-PHAT) algorithm, in which the steered response relates to peaks in the fourth order cross cumulant, rather than peaks in the second order…

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An Adaptive Blind Beamformer with an Integrated Single-channel Noise Reduction Method for Robust Realtime Blind Speech Extraction

B. Sällberg, N. Grbic, I. Claesson IEEE International Conference on Acoustics, Speech, and Signal Processing, pp. 309-312, Mar. 2008 The performance of single-channel temporal noise reduction methods generally deteriorate in high noise environments, whereas spatial beamformers can maintain some level of speech enhancement. This paper presents a solution where a low complexity single-channel noise reduction method is integrated into the feedback control loop of an adaptive blind beamformer with the purpose of robust blind speech extraction in high noise environments.…

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Online Blind Speech Extraction based on a Locally Quadratic Kurtosis Criteria and a Preprocessing Automatic Gain Controller

B. Sällberg, N. Grbic, I. Claesson IEEE ELMAR, pp. 139-142, Sept. 2007 This paper focuses on realtime speech extraction using blind adaptive beamforming. The speech extraction is carried out using an approximation of the kurtosis measure in a subband domain. The introduced kurtosis approximation is an improvement of a recently proposed approximation technique where a locally quadratic criterion was solved at each iteration. The improvement introduced in this paper regards an approach to normalize this same criterion using a pre-processing…

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Online Maximization of Subband Kurtosis for Blind Adaptive Beamforming in Realtime Speech Extraction

B. Sällberg, N. Grbic, I. Claesson IEEE 15th International Conference on Digital Signal Processing, pp. 603-606, 2007 This paper presents a method for blind beamforming with application in realtime speech extraction in a non-stationary environment. The blind beamforming is carried out using an online kurtosis maximization approach where the optimization is based on Newton’s method. The main novelty of the paper lies in the formulation of the subband kurtosis approximation, where a locally quadratic criterion is solved at each iteration.…

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Real-Time DSP Implementation of a Subband Beamforming Algorithm for Dual Microphone Speech Enhancement

Z. Yermeche, B. Sällberg, N. Grbic, I. Claesson IEEE International Symposium on Circuits and Systems, pp. 353-356, May 2007 A real-time digital signal processor (DSP) based implementation of a subband beamforming algorithm and its evaluation for dual microphone speech enhancement is presented. The algorithm, a calibrated constrained beamformer, is described theoretically and a real-time structure is proposed, including an efficient approach for multichannel data transformation. Measurements show that the battery driven DSP implementation supports 20 h operation-time, with an improved…

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Real time Implementation of a Blind Beamformer for Subband Speech Enhancement using Kurtosis Maximization

B. Sällberg, M. Swartling, N. Grbic, I. Claesson International Workshop on Acoustic Echo and Noise Control, Sep. 2006 This paper presents a real time implementation of a blind beamformer for subband speech enhancement. The beamformer adaptively maximizes the statistical kurtosis measure of the beamformer’s output signal. Speech carries high kurtosis and noise often exhibit lower kurtosis. Hence, maximization of the output signal’s kurtosis enhances speech, in general. The implementation is carried out on a novel framework for real time audio…

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Blind Beamforming Using Parallel Single-channel Speech Enhancers

B. Sällberg, N. Grbic, I. Claesson IEEE ELMAR, pp. 123-126, June 2006 This paper presents an idea to extend a certain class of single channel speech enhancement algorithms to include the spatial domain. The resulting blind beamformer does not rely on a-priori knowledge of source and sensor positions and it enhances one or several speech sources based only on received data. The underlying principle in this approach is the fact that speech signals are short time stationary. Provided that the…

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