| 1. |
- Shahid, Muhammad, et al.
(författare)
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Modulation Domain Adaptive Gain Equalizer for Speech Enhancement
- 2011
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Konferensbidrag (refereegranskat)abstract
- 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 implementation of AGE within modulation system, for the purpose of enhancing the speech signal. The successful implementation of the proposed system has been validated with various performance measurements, i.e., Signal to Noise Ratio Improvement (SNRI), Mean Opinion Score (MOS) and Spectral Distortion (SD). A spectrogram analysis is also presented to further substantiate the performance of this work
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| 2. |
- Bartunek, Josef Strom, et al.
(författare)
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Adaptive Fingerprint Image Enhancement with Emphasis on Preprocessing of Data
- 2013
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Ingår i: IEEE Transactions on Image Processing. - : IEEE. - 1941-0042 .- 1057-7149. ; 22:2, s. 644-656
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Tidskriftsartikel (refereegranskat)abstract
- This article proposes several improvements to an adaptive fingerprint enhancement method that is based on contextual filtering. The term adaptive implies that parameters of the method are automatically adjusted based on the input fingerprint image. Five processing blocks comprise the adaptive fingerprint enhancement method, where four of these blocks are updated in our proposed system. Hence, the proposed overall system is novel. The four updated processing blocks are; preprocessing, global analysis, local analysis and matched filtering. In the pre-processing and local analysis blocks, a nonlinear dynamic range adjustment method is used. In the global analysis and matched filtering blocks, different forms of order statistical filters are applied. These processing blocks yield an improved and new adaptive fingerprint image processing method. The performance of the updated processing blocks is presented in the evaluation part of this paper. The algorithm is evaluated towards the NIST developed NBIS software for fingerprint recognition on FVC databases.
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| 3. |
- Khan, Imran, et al.
(författare)
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Performing active noise control and acoustic experiments remotely
- 2012
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Ingår i: International Journal of Online Engineering. - : Kassel University Press GmbH. - 1868-1646 .- 1861-2121. ; 8:special issue 2, s. 65-74
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a novel and advanced remotely controlled laboratory for conducting Active Noise Control (ANC), acoustic and Digital Signal Processing (DSP) experiments. The laboratory facility, recently developed by Blekinge Institute of Technology (BTH) Sweden, supports remote learning through internet covering beginners level such as simple experimental measurements to advanced users and even researchers such as algorithm development and their performance evaluation on DSP. The required software development for ANC algorithms and equipment control are carried out anywhere in the world remotely from an internet-connected client PC using a standard web browser. The paper describes in detail how ANC, acoustic and DSP experiments can be performed remotely The necessary steps involved in an ANC experiment such as validity of ANC, forward path estimation and active control applied to a broad band random noise [0-200Hz] in a ventilation duct will be described in detail. The limitations and challenges such as the forward path and nonlinearities pertinent to the remote laboratory setup will be described for the guidance of the user. Based on the acoustic properties of the ventilation duct some of the possible acoustic experiments such as mode shapes analysis and standing waves analysis etc. will also be discussed in the paper.
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| 4. |
- Khan, Muhammad Gufran, et al.
(författare)
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Energy efficient binary PPM/code-multiplexed transmitted-reference multi-user UWB system
- 2011
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Konferensbidrag (refereegranskat)abstract
- 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 UWB system utilizes 3 dB less energy per bit as compared to the CM-TR system and achieves relatively longer silent periods between the pulses, which not only mitigate the IFI but also decrease the MUI due to less collisions with other asynchronous users. In the high SNR region, where the effect of IFI and MUI severely degrades the bit-error-rate (BER) performance of the multiuser CM-TR system, simulation results verify that the multiuser BPPM/CM-TR outperforms the multiuser CM-TR system.
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| 5. |
- Khan, Muhammad Gufran, et al.
(författare)
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Non-coherent detection of impulse radio UWB signals based on fourth order statistics
- 2009
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Konferensbidrag (refereegranskat)abstract
- 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 conventional energy detector (ED) and the proposed kurtosis detector (KD) is compared in terms of bit-error-rate (BER). The simulation results validate that the KD receiver outperforms a conventional ED receiver on both additive white Gaussian noise (AWGN) and IEEE 802.15.4a multipath channels.
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| 6. |
- Khan, Muhammad Gufran, et al.
(författare)
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Non-coherent detection of impulse radio UWB signals based on fourth order statistics
- 2011
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Ingår i: Wireless Personal Communications. - : Springer Science and Business Media LLC. - 1572-834X .- 0929-6212.
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Tidskriftsartikel (refereegranskat)abstract
- Low-complex and low power non-coherent energy detector (ED) is interesting for low data rate impulse radio (IR) ultra wideband (UWB) systems but, compared to coherent receivers, it suffers from a loss in performance due to low signal-to-noise ratio (SNR) at the detector. In addition, the performance of an ED strongly depends on the integration interval (window size) of the integrator and the window position. A non-coherent kurtosis detector (KD) and a fourth-order detector (FD), which can discriminate between Gaussian noise signals and non-Gaussian IR-UWB signals by directly estimating the fourth-order moment of the received signal, are presented. The performance of the detectors is evaluated using real channels measured in a corridor, an office and a laboratory environment. The results show that bit-error-rate (BER) performance of the proposed KD receiver is better than the ED receiver only under certain conditions, while the FD receiver is slightly better than the ED in low SNR region and its performance improves as the SNR increases. In addition, the performance of the FD receiver is less sensitive to overestimation of the integration interval making it relatively robust to variations of the channel delay spread. Finally, a criteria for the selection of integration time of the proposed detector is suggested.
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| 7. |
- Khan, Muhammad Gufran, et al.
(författare)
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Non-Coherent Fourth-Order Detector for Impulse Radio Ultra Wideband Systems : Empirical Evaluation Using Channel Measurements
- 2013
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Ingår i: Wireless personal communications. - : Springer. - 0929-6212 .- 1572-834X. ; 68:1, s. 27-46
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Tidskriftsartikel (refereegranskat)abstract
- Low-complex and low-power non-coherent energy detectors (EDs) are interesting for low data rate impulse radio (IR) ultra wideband (UWB) systems, but suffer from a loss in performance compared to coherent receivers. The performance of an ED also strongly depends on the integration interval (window size) of the integrator and the window position. This paper presents a non-coherent fourth-order detector (FD) which can discriminate between Gaussian noise signals and non-Gaussian IR-UWB signals by directly estimating the fourth-order moment of the received signal. The performance of the detectors is evaluated using realistic channels measured in a corridor, an office and a laboratory environment. The results show that bit-error-rate (BER) performance of the proposed FD receiver is slightly better than the ED in low signal-to-noise ratio (SNR) region and its performance improves as the SNR increases. In addition, BER of the FD receiver is less sensitive to overestimation of the integration interval making it relatively robust to variations of the channel delay spread. Finally, a criteria for the selection of integration time of the proposed detector is suggested.
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| 8. |
- Khan, Muhammad Gufran, et al.
(författare)
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Robust Weighted Non-Coherent Receiver for Impulse Radio UWB PPM Signals
- 2011
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Ingår i: IEEE Communications Letters. - : IEEE Communications Society. - 1089-7798 .- 1558-2558. ; 15:06, s. 614-616
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Tidskriftsartikel (refereegranskat)abstract
- This letter proposes an energy detection based robust weight estimation scheme for pulse-position modulated (PPM) impulse radio ultra-wideband (IR-UWB) signals using weighted non-coherent receiver (WNCR). Conventional data-aided WNCR (DA-WNCR) scheme estimates the weighting coefficients, or channel state information (CSI), using a large number of training symbols over time-varying channels. In contrast, the proposed Robust WNCR (R-WNCR) scheme is non-data-aided (NDA), adaptive and robust to channel variations. The proposed R-WNCR estimates the weighting coefficients adaptively based on the received stochastic data, and the weight estimation process is refined using a decision directed approach.
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| 9. |
- Swartling, Mikael, et al.
(författare)
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Direction of Arrival Estimation for Speech Sources using Fourth Order Cross Cumulants
- 2008
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Konferensbidrag (refereegranskat)abstract
- 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 cross cumulant, i.e. the cross power spectrum. Since speech sources have a Probability Density Function (PDF) close to the Laplacian distribution and noise are generally closer to the Gaussian distribution, the fourth order cumulant becomes a good alternative for the steered response search for speech sources. The proposed method is evaluated and compared to the original SRP-PHAT algorithm and shows significant improvements in localization performance for speech sources.
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| 10. |
- Swartling, Mikael, et al.
(författare)
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Source localization for multiple speech sources using low complexity non-parametric source separation and clustering
- 2011
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Ingår i: Signal Processing. - : Elsevier. - 0165-1684 .- 1872-7557. ; 91:8, s. 1781-1788
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Tidskriftsartikel (refereegranskat)abstract
- This article presents a new method for localization of multiple concurrent speech sources that relies on simultaneous blind signal separation and direction of arrival (DOA) estimation, as well as a method to solve the intersection point selection problem that arises when locating multiple speech sources using multiple sensor arrays. The proposed method is based on a low complexity non-parametric blind signal separation method, making is suitable for real-time applications on embedded platforms. On top of reduced complexity in comparison to a previously presented method, the DOA estimation accuracy is also improved. Evaluation of the performance is done with both real recording and simulations, and a real-time prototype of the proposed method has been implemented on a DSP platform to evaluate the computational and the memory complexities in a real application.
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