Global ETD Search

131	Comparative Denoising Study Deep Learning & Collaborative Filter / Jämförande Brusreducerande Studie Djup Maskininlärning & Kollaborativa Filter Kamoun, Sami January 2024 (has links) This thesis addresses the challenge of denoising microscopy images captured under low-light conditionswith varying intensity levels. The study compares three deep learning models — N2V, CARE, andRCAN — against the collaborative filter BM4D, which serves as a reference point. The models weretrained on two distinct datasets: Endoplasmic Reticulum and Mitochondria datasets, both acquired witha lattice light-sheet microscope.Results show that BM4D maintains stable performance metrics and delivers superior visual quality,when compared to the noisy input. In contrast, the deep learning models exhibit poor performance onnoisy test images when trained on datasets with non-uniform noise levels. Additionally, a sensitivitycomparison of neural parameter between the same models was made. Revealing that supervised modelsare data-specific to some extent, whereas the self-supervised N2V demonstrates consistent neuralparameters, suggesting lower data specificity. / Denna uppsats tar upp problemet med att reducera brus i mikroskopibilder tagna under svagaljusförhållanden med varierande intensitetsnivåer. Studien jämför tre djupinlärningsmodeller – N2V,CARE och RCAN – mot det kollaborativa filtret BM4D, vilket agerar som en referenspunkt.Modellerna tränades på två olika dataset: Endoplasmic Reticulum och Mitochondria, båda tagna meden selektiv planbelysningsmikroskop (lattice light-sheet microscope).Resultaten visar att BM4D behåller stabila prestationsmått och levererar bättre visuell kvalitet, jämförtmed den brusiga input. Däremot visar djupinlärningsmodellerna bristande prestanda på brusigatestbilder när de tränats på data med icke-enhetliga brusnivåer. Dessutom gjordes enkänslighetsjämförelse av neurala parametrar mellan samma modeller. Detta visade att de övervakademodellerna är specifika för data i viss utsträckning, medan den självövervakade N2V-modellen visarlika neurala parametrar, vilket tyder på lägre dataspecificitet Block Matching 3D (BM3D) Block Matching 4D (BM4D) Content Aware Image Restoration (CARE) Deep Learning (DL) Image Denoising Image Quality Machine Learning (ML) Neural Network Noise Noise2Void (N2V) Signal-to-Noise Ratio (SNR) Physical Sciences Fysik
132	Modelling of Mobile Fading Channels with Fading Mitigation Techniques. Shang, Lei, lei.shang@ieee.org January 2006 (has links) This thesis aims to contribute to the developments of wireless communication systems. The work generally consists of three parts: the first part is a discussion on general digital communication systems, the second part focuses on wireless channel modelling and fading mitigation techniques, and in the third part we discuss the possible application of advanced digital signal processing, especially time-frequency representation and blind source separation, to wireless communication systems. The first part considers general digital communication systems which will be incorporated in later parts. Today's wireless communication system is a subbranch of a general digital communication system that employs various techniques of A/D (Analog to Digital) conversion, source coding, error correction, coding, modulation, and synchronization, signal detection in noise, channel estimation, and equalization. We study and develop the digital communication algorithms to enhance the performance of wireless communication systems. In the Second Part we focus on wireless channel modelling and fading mitigation techniques. A modified Jakes' method is developed for Rayleigh fading channels. We investigate the level-crossing rate (LCR), the average duration of fades (ADF), the probability density function (PDF), the cumulative distribution function (CDF) and the autocorrelation functions (ACF) of this model. The simulated results are verified against the analytical Clarke's channel model. We also construct frequency-selective geometrical-based hyperbolically distributed scatterers (GBHDS) for a macro-cell mobile environment with the proper statistical characteristics. The modified Clarke's model and the GBHDS model may be readily expanded to a MIMO channel model thus we study the MIMO fading channel, specifically we model the MIMO channel in the angular domain. A detailed analysis of Gauss-Markov approximation of the fading channel is also given. Two fading mitigation techniques are investigated: Orthogonal Frequency Division Multiplexing (OFDM) and spatial diversity. In the Third Part, we devote ourselves to the exciting fields of Time-Frequency Analysis and Blind Source Separation and investigate the application of these powerful Digital Signal Processing (DSP) tools to improve the performance of wireless communication systems. Multipath interference channel modelling fading channel capacity channel tracking channel estimation Doppler spread coherence time delay spread detection autocorrelation function (ACF) level-crossing rate (LCR) average duration of fades (ADF) diversity error correction coding MIMO (Multi-Input and Multi-Output) Frequency Division Multiplexing) MIMO (Multi-Input and Multi-Output) additive Gaussian noise signal-to-noise-ratio (SNR) Sigma-Delta quantization blind source separation time-frequency distribution (TFD).
133	Performance evaluation and protocol design of fixed-rate and rateless coded relaying networks Nikjah, Reza 06 1900 (has links) The importance of cooperative relaying communication in substituting for, or complementing, multiantenna systems is described, and a brief literature review is presented. Amplify-and-forward (AF) and decode-and-forward (DF) relaying are investigated and compared for a dual-hop relay channel. The optimal strategy, source and relay optimal power allocation, and maximum cooperative gain are determined for the relay channel. It is shown that while DF relaying is preferable to AF relaying for strong source-relay links, AF relaying leads to more gain for strong source-destination or relay-destination links. Superimposed and selection AF relaying are investigated for multirelay, dual-hop relaying. Selection AF relaying is shown to be globally strictly outage suboptimal. A necessary condition for the selection AF outage optimality, and an upper bound on the probability of this optimality are obtained. A near-optimal power allocation scheme is derived for superimposed AF relaying. The maximum instantaneous rates, outage probabilities, and average capacities of multirelay, dual-hop relaying schemes are obtained for superimposed, selection, and orthogonal DF relaying, each with parallel channel cooperation (PCC) or repetition-based cooperation (RC). It is observed that the PCC over RC gain can be as much as 4 dB for the outage probabilities and 8.5 dB for the average capacities. Increasing the number of relays deteriorates the capacity performance of orthogonal relaying, but improves the performances of the other schemes. The application of rateless codes to DF relaying networks is studied by investigating three single-relay protocols, one of which is new, and three novel, low complexity multirelay protocols for dual-hop networks. The maximum rate and minimum energy per bit and per symbol are derived for the single-relay protocols under a peak power and an average power constraint. The long-term average rate and energy per bit, and relay-to-source usage ratio (RSUR), a new performance measure, are evaluated for the single-relay and multirelay protocols. The new single-relay protocol is the most energy efficient single-relay scheme in most cases. All the multirelay protocols exhibit near-optimal rate performances, but are vastly different in the RSUR. Several future research directions for fixed-rate and rateless coded cooperative systems, and frameworks for comparing these systems, are suggested. / Communications acknowledgment signals amplify-and-forward relaying average capacity average power constraint bit error rate cooperative gain cooperative communication decode-and-forward relaying degree of freedom direct transmission distributed space-time coding dual-hop relaying energy efficiency energy per bit energy per symbol feedback communication fixed-rate coded relaying fixed-rate codes fixed-rate coding large SNR approximation maximal ratio combining maximum achievable rates maximum likelihood multiple access channels mutual information nonconcave fractional programming numerical optimization optimal power allocation orthogonal relaying outage optimality outage probability parallel channel coding peak power constraint power allocation schemes power fairness protocol design rateless coded relaying rateless codes rate efficiency rateless coding Rayleigh fading relay-to-source usage ratio relaying networks repetition coding selection relaying single-hop communication superimposed relaying symbol error rate
134	Performance evaluation and protocol design of fixed-rate and rateless coded relaying networks Nikjah, Reza Unknown Date No description available. acknowledgment signals amplify-and-forward relaying average capacity average power constraint bit error rate cooperative gain cooperative communication decode-and-forward relaying degree of freedom direct transmission distributed space-time coding dual-hop relaying energy efficiency energy per bit energy per symbol feedback communication fixed-rate coded relaying fixed-rate codes fixed-rate coding large SNR approximation maximal ratio combining maximum achievable rates maximum likelihood multiple access channels mutual information nonconcave fractional programming numerical optimization optimal power allocation orthogonal relaying outage optimality outage probability parallel channel coding peak power constraint power allocation schemes power fairness protocol design rateless coded relaying rateless codes rate efficiency rateless coding Rayleigh fading relay-to-source usage ratio relaying networks repetition coding selection relaying single-hop communication superimposed relaying symbol error rate

Page generated in 0.0185 seconds