2011 6th International Conference on Telecommunication Systems, Services, and Applications (TSSA), 2011
Existing wireless channel models are based on statistical impulse response methods derived from e... more Existing wireless channel models are based on statistical impulse response methods derived from empirical analyses. These algorithms are inefficient in signal representation and consume a lot of computational power. Meanwhile, the theory of wavelets and wavelet packets, which have recently found applicability in signal processing applications, hold great promise for wireless channel modeling. In this paper the use of wavelet
In the increasingly pressing context of improving recycling, optical technologies present a broad... more In the increasingly pressing context of improving recycling, optical technologies present a broad potential to support the adequate sorting of plastics. Nevertheless, the commercially available solutions (for example, employing near-infrared spectroscopy) generally focus on identifying mono-materials of a few selected types which currently have a market-interest as secondary materials. Current progress in photonic sciences together with advanced data analysis, such as artificial intelligence, enable bridging practical challenges previously not feasible, for example in terms of classifying more complex materials. In the present paper, the different techniques are initially reviewed based on their main characteristics. Then, based on academic literature, their suitability for monitoring the composition of multi-materials, such as different types of multi-layered packaging and fibre-reinforced polymer composites as well as black plastics used in the motor vehicle industry, is discussed. Finally, some commercial systems with applications in those sectors are also presented. This review mainly focuses on the materials identification step (taking place after waste collection and before sorting and reprocessing) but in outlook, further insights on sorting are given as well as future prospects which can contribute to increasing the circularity of the plastic composites' value chains.
Spectrum Sensing is an important functionality of Cognitive Radio (CR). Accuracy and speed of est... more Spectrum Sensing is an important functionality of Cognitive Radio (CR). Accuracy and speed of estimation are the key indicators to select the appropriate spectrum sensing technique. Conventional spectrum estimation techniques which are based on Short Time Fourier Transform (STFT) suffer from familiar problems such as low frequency resolution, high variance of estimated power spectrum and high side lobes/leakages. Methods such as Multi Taper Spectrum Estimation successfully alleviate these infarctions but exact a high price in terms of complexity. On these accounts, it appears that the filter bank spectrum estimation formulated by F. Boroujeny and wavelet based spectrum estimates are the most promising and pragmatic approaches for CR applications. This article surveys and appraises available literature on various spectrum sensing techniques and discusses spectrum sensing as a key element of CR system design.
2009 Ieee 20th International Symposium on Personal Indoor and Mobile Radio Communications, Sep 13, 2009
ABSTRACT Wavelet packet transform has recently emerged as a novel spectrum estimation technique w... more ABSTRACT Wavelet packet transform has recently emerged as a novel spectrum estimation technique with attractions such as good time-frequency resolution, low variance of estimate and low complexity. Key to the successful operation of the system is the choice of the wavelet used. Commonly known wavelets are not frequency selective in nature and hence result in estimates with poor frequency resolution. To alleviate this problem, we design and develop a family of wavelets that are maximally frequency selective in nature. To this end, the design constraints are first enlisted. Then the problem, originally non-convex, is reformulated into a convex optimization problem and solved using Semi Definite Programming (SDP) tools. Through simulation studies the benefits of the newly designed wavelets are demonstrated.
2009 Ieee 20th International Symposium on Personal Indoor and Mobile Radio Communications, Sep 14, 2009
... Center for Telecommunications and Radar (IRCTR) Department of Electrical Engineering, Mathema... more ... Center for Telecommunications and Radar (IRCTR) Department of Electrical Engineering, Mathematics and Computer Science Delft University of Technology, Mekelweg 4, 2628 CD Delft, The Netherlands mklakshmanan@tudelft.nl, h ... 2 /2 , , , , 1 1 1 [ ] [ ] [ j J J N N jk jk J k J k j k ...
2010 International Conference on Signal Processing and Communications (SPCOM), 2010
ABSTRACT In this article, we investigate the application of wavelet packet transform (WPT) for sp... more ABSTRACT In this article, we investigate the application of wavelet packet transform (WPT) for spectral estimation and analysis. The main attraction for the method is the tradeoffs it offers in terms of satisfying various figure of merits such as high frequency resolution, good side lobe suppression and low variations in the estimated power spectral density (PSD). The performance of the system is evaluated through computer simulations. The results of the experiments show that the wavelet based approach offers great flexibility and adaptability apart from its performances which are comparable and at times even better than Fourier based estimates.
In this article, we investigate the application of wavelet packet transform as a novel spectrum s... more In this article, we investigate the application of wavelet packet transform as a novel spectrum sensing approach. The main attraction for wavelet packets is the tradeoffs they offer in terms of satisfying various performance metrics such as frequency resolution, variance of the estimated power spectral density (PSD) and complexity. The results of the experiments show that the wavelet based approach offers great flexibility, reconfigure ability and adaptability apart from its performances which are comparable and at times even better than Fourier based estimates.
Wavelet Packet Modulation (WPM) is a novel multicarrier modulation technique and a promising alte... more Wavelet Packet Modulation (WPM) is a novel multicarrier modulation technique and a promising alternative to the well established OFDM. A major drawback of multicarrier systems is their high peak-to-average power ratio (PAPR). In this paper, we study the PAPR performances of WPM systems. The novelty of the work is in the investigation of the stochastic of the WPM signals and influence of the waveshapes properties on their PAPR performances. Several well-known wavelets such as Daubechies, Symlets, Coiflets, Discrete Meyer and biorthogonal wavelet are applied. The results of this research show how these wavelet-based systems cope with PAPR.
Spectrum sensing is important in cognitive radio (CR). Accuracy and speed of estimation are keys ... more Spectrum sensing is important in cognitive radio (CR). Accuracy and speed of estimation are keys to select appropriate spectrum sensing technique. Conventional spectrum estimation techniques based on short time Fourier transform suffer from familiar problems such as low frequency resolution, large variance of estimated power and large side lobes. In this article, the possibility of employing wavelet packet decomposition for new spectrum sensing is investigated. In order to investigate the performance of the proposed approach, four types of sources (transmitters) are used, namely partial band, single tone, multi tone and swept tone. To simulate the temporal dynamics in CR, a special kind of source called swept tone source is devised. The novelty of this work relates to the development of wavelet packet decomposition using filter bank approach as a new spectrum sensing tool recommended for CR. The results of this study show that the wavelet based spectral estimation is a promising tec...
2007 European Conference on Wireless Technologies, 2007
Performance degradation of UWB-IR wireless systems due to interference from co-existing services ... more Performance degradation of UWB-IR wireless systems due to interference from co-existing services is an important issue. To reduce the effect of interference from coexisting sources such as the WLAN standard IEEE 802.11a on UWB Communication, the construction of a modified template waveform using multi-carrier sinusoids was proposed previously. However, that work considered a free space propagation channel model with no treatment of the frequency dependence of the UWB path loss. In this paper we broaden the study by taking into consideration a frequency dependent path loss environment. The novelty of the work is in the investigation of the effect of frequency and distance dependency of the path loss on the performance of interference mitigation scheme.
2011 6th International Conference on Telecommunication Systems, Services, and Applications (TSSA), 2011
Existing wireless channel models are based on statistical impulse response methods derived from e... more Existing wireless channel models are based on statistical impulse response methods derived from empirical analyses. These algorithms are inefficient in signal representation and consume a lot of computational power. Meanwhile, the theory of wavelets and wavelet packets, which have recently found applicability in signal processing applications, hold great promise for wireless channel modeling. In this paper the use of wavelet
In the increasingly pressing context of improving recycling, optical technologies present a broad... more In the increasingly pressing context of improving recycling, optical technologies present a broad potential to support the adequate sorting of plastics. Nevertheless, the commercially available solutions (for example, employing near-infrared spectroscopy) generally focus on identifying mono-materials of a few selected types which currently have a market-interest as secondary materials. Current progress in photonic sciences together with advanced data analysis, such as artificial intelligence, enable bridging practical challenges previously not feasible, for example in terms of classifying more complex materials. In the present paper, the different techniques are initially reviewed based on their main characteristics. Then, based on academic literature, their suitability for monitoring the composition of multi-materials, such as different types of multi-layered packaging and fibre-reinforced polymer composites as well as black plastics used in the motor vehicle industry, is discussed. Finally, some commercial systems with applications in those sectors are also presented. This review mainly focuses on the materials identification step (taking place after waste collection and before sorting and reprocessing) but in outlook, further insights on sorting are given as well as future prospects which can contribute to increasing the circularity of the plastic composites' value chains.
Spectrum Sensing is an important functionality of Cognitive Radio (CR). Accuracy and speed of est... more Spectrum Sensing is an important functionality of Cognitive Radio (CR). Accuracy and speed of estimation are the key indicators to select the appropriate spectrum sensing technique. Conventional spectrum estimation techniques which are based on Short Time Fourier Transform (STFT) suffer from familiar problems such as low frequency resolution, high variance of estimated power spectrum and high side lobes/leakages. Methods such as Multi Taper Spectrum Estimation successfully alleviate these infarctions but exact a high price in terms of complexity. On these accounts, it appears that the filter bank spectrum estimation formulated by F. Boroujeny and wavelet based spectrum estimates are the most promising and pragmatic approaches for CR applications. This article surveys and appraises available literature on various spectrum sensing techniques and discusses spectrum sensing as a key element of CR system design.
2009 Ieee 20th International Symposium on Personal Indoor and Mobile Radio Communications, Sep 13, 2009
ABSTRACT Wavelet packet transform has recently emerged as a novel spectrum estimation technique w... more ABSTRACT Wavelet packet transform has recently emerged as a novel spectrum estimation technique with attractions such as good time-frequency resolution, low variance of estimate and low complexity. Key to the successful operation of the system is the choice of the wavelet used. Commonly known wavelets are not frequency selective in nature and hence result in estimates with poor frequency resolution. To alleviate this problem, we design and develop a family of wavelets that are maximally frequency selective in nature. To this end, the design constraints are first enlisted. Then the problem, originally non-convex, is reformulated into a convex optimization problem and solved using Semi Definite Programming (SDP) tools. Through simulation studies the benefits of the newly designed wavelets are demonstrated.
2009 Ieee 20th International Symposium on Personal Indoor and Mobile Radio Communications, Sep 14, 2009
... Center for Telecommunications and Radar (IRCTR) Department of Electrical Engineering, Mathema... more ... Center for Telecommunications and Radar (IRCTR) Department of Electrical Engineering, Mathematics and Computer Science Delft University of Technology, Mekelweg 4, 2628 CD Delft, The Netherlands mklakshmanan@tudelft.nl, h ... 2 /2 , , , , 1 1 1 [ ] [ ] [ j J J N N jk jk J k J k j k ...
2010 International Conference on Signal Processing and Communications (SPCOM), 2010
ABSTRACT In this article, we investigate the application of wavelet packet transform (WPT) for sp... more ABSTRACT In this article, we investigate the application of wavelet packet transform (WPT) for spectral estimation and analysis. The main attraction for the method is the tradeoffs it offers in terms of satisfying various figure of merits such as high frequency resolution, good side lobe suppression and low variations in the estimated power spectral density (PSD). The performance of the system is evaluated through computer simulations. The results of the experiments show that the wavelet based approach offers great flexibility and adaptability apart from its performances which are comparable and at times even better than Fourier based estimates.
In this article, we investigate the application of wavelet packet transform as a novel spectrum s... more In this article, we investigate the application of wavelet packet transform as a novel spectrum sensing approach. The main attraction for wavelet packets is the tradeoffs they offer in terms of satisfying various performance metrics such as frequency resolution, variance of the estimated power spectral density (PSD) and complexity. The results of the experiments show that the wavelet based approach offers great flexibility, reconfigure ability and adaptability apart from its performances which are comparable and at times even better than Fourier based estimates.
Wavelet Packet Modulation (WPM) is a novel multicarrier modulation technique and a promising alte... more Wavelet Packet Modulation (WPM) is a novel multicarrier modulation technique and a promising alternative to the well established OFDM. A major drawback of multicarrier systems is their high peak-to-average power ratio (PAPR). In this paper, we study the PAPR performances of WPM systems. The novelty of the work is in the investigation of the stochastic of the WPM signals and influence of the waveshapes properties on their PAPR performances. Several well-known wavelets such as Daubechies, Symlets, Coiflets, Discrete Meyer and biorthogonal wavelet are applied. The results of this research show how these wavelet-based systems cope with PAPR.
Spectrum sensing is important in cognitive radio (CR). Accuracy and speed of estimation are keys ... more Spectrum sensing is important in cognitive radio (CR). Accuracy and speed of estimation are keys to select appropriate spectrum sensing technique. Conventional spectrum estimation techniques based on short time Fourier transform suffer from familiar problems such as low frequency resolution, large variance of estimated power and large side lobes. In this article, the possibility of employing wavelet packet decomposition for new spectrum sensing is investigated. In order to investigate the performance of the proposed approach, four types of sources (transmitters) are used, namely partial band, single tone, multi tone and swept tone. To simulate the temporal dynamics in CR, a special kind of source called swept tone source is devised. The novelty of this work relates to the development of wavelet packet decomposition using filter bank approach as a new spectrum sensing tool recommended for CR. The results of this study show that the wavelet based spectral estimation is a promising tec...
2007 European Conference on Wireless Technologies, 2007
Performance degradation of UWB-IR wireless systems due to interference from co-existing services ... more Performance degradation of UWB-IR wireless systems due to interference from co-existing services is an important issue. To reduce the effect of interference from coexisting sources such as the WLAN standard IEEE 802.11a on UWB Communication, the construction of a modified template waveform using multi-carrier sinusoids was proposed previously. However, that work considered a free space propagation channel model with no treatment of the frequency dependence of the UWB path loss. In this paper we broaden the study by taking into consideration a frequency dependent path loss environment. The novelty of the work is in the investigation of the effect of frequency and distance dependency of the path loss on the performance of interference mitigation scheme.
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