Global ETD Search

1	Performance Comparison of Selective Rake Receivers with CLEAN Algorithms in UWB Systems Yang, Siang-Yu 26 July 2006 (has links) The Ultra-Wideband (UWB) channel is a dense multipath channel. The system performance and design complexity issues of selective-Rake receiver (SRake) are studied. Rake receiver has difficulties achieving desired system performance in the dense multipath environment. The main ideas of SRake receiver are to obtain the SNR level on known multipath channel and determine the desired number of Rake fingers. In the implementation of the SRake, the CLEAN algorithm is used in selecting the paths with relatively high energy. We can improve the performance of SRake receiver by increasing the accuracy of path selection. By the property of local maximum peak within the smaller partition, Two-Stage CLEAN algorithm acquires the more accurate delay time of multipath. In order to mitigate the sidelobe effect and noise interference, the key assumption in the Deng¡¦s Modified CLEAN algorithm is that using average amplitude around the considered data change as the criterion to determine if the data value is a true path. In this thesis, we investigate CLEAN, Two-Stage CLEAN and Deng¡¦s Modified CLEAN algorithm in three different systems including UWB-Impulse Radio, Pulse Radar and DS-UWB. From the performance comparison, it can be seen that the Two-Stage CLEAN algorithm that has the highest accuracy of path selection in UWB system. CLEAN Algorithm Two-Stage CLEAN Algorithm UWB-Impulse Radio Pulse Radar Deng's Modified CLEAN Algorithm Selective Rake Receiver Ultra-Wideband DS-UWB
2	Performance Analysis of Improved Selective-Rake on Ultra-Wideband Channels Wang, Yan-Lun 23 July 2004 (has links) The Ultra-Wideband (UWB) communication technology has been extensively attended in recent years. In this thesis, we propose the improved selective-Rake receiver and analyze the performance on UWB channels. The UWB transmission channels are modeled with statistical methods and its fading characteristics are discussed. Different impulse radio properties for the UWB communication system are analyzed. The system performance and design complexity issues of selective-Rake receiver (SRake) are studied. Rake receiver has difficulties achieving desired system performance in the dense multipath environment. The main ideas of SRake receiver are to obtain the SNR level on known multipath channel and to determine the desired number of Rake fingers. Matched filters and maximum likelihood detectors are utilized in the implementation of the SRake to estimate the signal time delay. The CLEAN algorithm is then used in selecting the paths with relatively high energy. Furthermore, we also propose a noise cancellation scheme for performance improvement in the SRake receiver. In the noise cancellation scheme, the multiresolution property of wavelet transform is used for filtering the noise interference caused by the rapid fluctuation factor. In addition, a two-stage search is combined with the original CLEAN algorithm to increase the accuracy of path selection. From our simulation results on the UWB channels, the improved SRake receiver, with noise cancellation and two-stage search, indeed has high SRake output SNR and better path accuracy than the original SRake receiver. Selective-Rake CLEAN Algorithm Impulse Radio Wavelet Transform Ultra-Wideband
3	Εφαρμογή του Clean αλγόριθμου σε συνδυασμό με την παραγοντική ανάλυση για τη μελέτη χρονοσειρών παραμέτρων βιολογικού καθαρισμού βιομηχανίας Βαλλιανάτου, Σπυριδούλα 17 September 2012 (has links) Στόχος της παρούσας εργασίας είναι η ανάπτυξη ενός μεθοδολογικού σχήματος που συνίσταται από τον CLEAN αλγόριθμο, και την παραγοντική ανάλυση, για τη μελετη χρονοσειρων παραμετρων βιολογικου καθαρισμου βιομηχανιας. Ο CLEAN αλγόριθμος χρησιμοποιείται για την πλήρωση κενών στα αρχικά δεδομένα ώστε να προκύψουν συνεχείς χρονοσειρές, ενώ η παραγοντική ανάλυση ανιχνεύει τις σχέσεις μεταξύ των αρχικών μεταβλητών. Η ανάπλαση των χρονοσειρών αναδεικνύει τις σημαντικότερες πληροφορίες όσον αφορά τη χρονική διακύμανση των κυρίαρχων διεργασιών του βιολογικού καθαρισμού – τα αποτελέσματα ενισχύονται με την εφαρμογή της παραγοντικής ανάλυσης. Η παρούσα εργασία προτείνει ένα σχετικά απλό και αποτελεσματικό μεθοδολογικό σχήμα για τη καλύτερη παρακολούθηση της λειτουργίας μονάδων βιολογικού καθαρισμού. Αναλύθηκαν και μελετήθηκαν δεκατρείς παράμετροι, οι οποίες συλλέχθηκαν σε περίοδο οχτώ ετών. Με την εφαρμογή της CLEAN φασματικής ανάλυσης και της παραγοντικής ανάλυσης επεξεργάστηκαν συνολικά 37.960 δεδομένα. Αρχικά, ο CLEAN αλγόριθμος λειτούργησε με μεγάλη επιτυχία και συμπλήρωσε όλα τα κενά των αρχικών ανεπεξέργαστων δεδομένων και στη συνέχεια με την εφαρμογή της παραγοντικής ανάλυσης φάνηκε ότι επτά διεργασίες ελέγχουν διαχρονικά τη λειτουργία του βιολογικού καθαρισμού. Η CLEAN φασματική ανάλυση σε συνδυασμό με την πολυδιάστατη στατιστική παραγοντική ανάλυση αποτελούν ένα αποτελεσματικό και εξαιρετικά χρήσιμο εργαλείο για την μελέτη περιβαλλοντικών δεδομένων. / The scope of the study is the development of a methodology based on CLEAN algorithm and factor analysis for the study of the time series of parameters from a waste water treatment unit. CLEAN algorithm is used to cover missing data and measurements in order to create a time series without gaps, while factor analysis is used to detect relations and connection between the different parameters. Filling in the gaps in the time series, points out the most important information about frequency and repeatability of the basic procedures in the waste water treatment – those results are further supported by application of the factor analysis. This study suggests a simple and efficient approach for the supervision of waste water treatment units. Thirteen parameters, recorded for an eight years period were analyzed using the suggested methodology. 37.960 data in total were analyzed and processed. CLEAN algorithm was successfully applied to fill the gaps in the data. Factor analysis was used to point out 7 procedures as the key – factors controlling the waste water treatment operation for the whole time period. CLEAN algorithm in combination with the multiparameter statistical factor analysis compose a useful and effective tool for the study of complex environmental systems, like waste water units. Clean αλγόριθμος Παραγοντική ανάλυση 628.168 3 Clean algorithm Factor analysis
4	Cost-Based CLEAN Algorithm for Selective RAKE Receivers in UWB Systems Ke, Chih-chiang 29 July 2008 (has links) In this thesis, we propose a cost-based CLEAN algorithm to accurately find dense multi-path parameters and improve the performance of selective RAKE receiver in indoor UWB systems. RAKE receiver can resolve the dense multi-path interference problems with the multi-path parameters. Because the weak paths are of lower valuable for system performance improvement, selective RAKE receiver combines only the strongest multi-path components and reduce the number of fingers to lower the complexity of RAKE receiver. However, selective RAKE receiver needs accurate multi-path detection to decide the suitable number and parameters of fingers. In order to improve the performance of selective RAKE receiver, the main issue in this thesis is to detect the best paths of channel with the CLEAN algorithm. CLEAN algorithm uses the correlation of the received signal and the template signal as the basis for searching paths. If there are closely adjacent paths, or if one of signal paths is relatively stronger, the detection error of paths may occur and thus affects the performance of the receiver. EP-based CLEAN algorithm uses the cost function and the evolutionary programming (EP) to search the multi-path delay times and gain coefficients for minimizing the cost function. Accurate multi-path detection and high resolution of adjacent paths can be obtained. However, EP-based CLEAN algorithm makes a time-consuming blind search. In the thesis, a CLEAN algorithm based on the cost function is proposed. The proposed cost-based CLEAN algorithm searches the delay times near the peaks of the cross-correlation for local minimum of the cost function, and then uses CLEAN algorithm to extract autocorrelation components and obtain the accurate multi-path detection. By testing the IEEE802.15.3a UWB channel models, and comparing with CLEAN algorithm, the cost-based CLEAN algorithm in the thesis can achieve better detection accuracy in multi-path searching, and improve the performance of selective RAKE receiver. Cost-based CLEAN Algorithm Multi-path UWB Selective RAKE Receiver Cost Function
5	Channel Probing for an Indoor Wireless Communications Channel Hunter, Brandon 13 March 2003 (has links) (PDF) The statistics of the amplitude, time and angle of arrival of multipaths in an indoor environment are all necessary components of multipath models used to simulate the performance of spatial diversity in receive antenna configurations. The model presented by Saleh and Valenzuela, was added to by Spencer et. al., and included all three of these parameters for a 7 GHz channel. A system was built to measure these multipath parameters at 2.4 GHz for multiple locations in an indoor environment. Another system was built to measure the angle of transmission for a 6 GHz channel. The addition of this parameter allows spatial diversity at the transmitter along with the receiver to be simulated. The process of going from raw measurement data to discrete arrivals and then to clustered arrivals is analyzed. Many possible errors associated with discrete arrival processing are discussed along with possible solutions. Four clustering methods are compared and their relative strengths and weaknesses are pointed out. The effects that errors in the clustering process have on parameter estimation and model performance are also simulated. multipath multipath propagation propagation environment indoor propagation indoor multipath indoor multipath propagation channel probing channel probing indoor wireless communications channel indoor wireless communications indoor wireless communications wireless communications wireless communications channel MIMO SISO multiple input multiple output single input single output antenna diversity antenna diversity antenna array channel modeling modeling model wireless propagation clustering methods clustering algorithms clustering parameter estimation parameter channel matrix h matrix ray tracing point spread function psf deconvolution clean algorithm clean algorithm antenna pattern network analyzer temporal pattern 2.4 ghz system 6 ghz system channel capacity capacity estimate channel capacity estimate propagation environment scattering transfer matrix matrix water filling solution water filling method water filling Saleh Valenzuela Saleh and Valenzuela Model arrival time of arrival angle of arrival direction of arrival arrival amplitude arrivals antenna positioner data simulations measurements angle of departure direction of departure correlation convolution errors error CFA CFAD constant false alarm constant false alarm detection signal signal dependent clutter clutter returns transmitter transmit receive receiver transmit antenna receive antenna spatial correlation system PSF system point spread function mapping fuzzy c-means clustering fuzzy clustering c-means clustering c-means fuzzy k-means euclidean distance time amplitude delay performance prediction performance prediction errors fuzzy weighted distance method rectangular method weighted rectangular method statistics statistical statistical model Electrical and Computer Engineering

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