Dissertations / Theses on the topic '"block-scheme" form'

碩士<br>國立成功大學<br>電機工程學系碩博士班<br>91<br>The Discrete Wavelet Transform (DWT) has been used in image processing for the past few years. 2-D DWT architectures can be classified into line-based and block-based architectures. Line-based architectures are simple with low complexity. They are efficient for 1-D applications. In case of 2-D transforms (or higher), they suffer from two main problems: memory requirements and latency. These problems are inherent to line-based architectures. In this thesis, a novel block-based architecture for computing the lifting-based 2-D DWT coefficients is presented. These architectures make the significant reduction of buffer size and speeds up the calculation of 2-D wavelet coefficients as compared with those line-based fashion architectures. In addition, the proposed architecture supports the JPEG2000 default filters. Compared to the line-based architectures, the latency is reduced from N2 down to 3N. Finally, the architecture has been realized in ARM-based ALTERA EPXA10 Development Board with frequency at 44.33MHz.

碩士<br>國立成功大學<br>資訊工程學系碩博士班<br>95<br>As a result of the popularization of the Internet and digital cameras, the increase of the amount of personal image data is huge. In recent years, many researchers have found that image compression techniques adopting discrete wavelet transform (DWT) frequently outperform techniques adopting discrete cosine transform (DCT). So a lot of compression techniques involved DWT have been proposed recently. JPEG2000, for example, is a wavelet-based still image compression standard. The kernel algorithm for JPEG2000, EBOCT, proposed by Taubman, however, takes higher computation time than other state-of-the-art wavelet-based image compression schemes such as Set Partitioning Embedded block (SPECK). SPECK proposed by Pearlman, Islam, Nagaraj, and Said is thereafter integrated into the VM3.2A (Verification Model, version 3.2A) as a low complexity solution. In this thesis, we propose a method called HSPECK (Huffman SPECK) which is based on SPECK to further improve the compression ratio. From observation, we are able to establish the probability distribution over significance pattern of four sub-blocks generated successively along the wavelet decomposition process. Therefore, Huffman coding scheme can then be employed for coding wavelet coefficients. The experimental results show that under the same PSNR, the bit rates via the proposed approach are improved by 3% to 9%.

碩士<br>國立臺北科技大學<br>電資碩士班<br>102<br>The 3rd Generation Partnership Project (3GPP) completed a study on coordinated multi-point transmission and reception (CoMP) techniques to facilitate cooperative communications across multiple transmission and reception points (e.g., cells) for the LTE-Advanced (LTE-A) system. CoMP was initially brought forward in the study item of LTE-A to meet the requirements of the International Mobile Telecommunications Advanced (IMT-Advanced) in 2008. At their meeting (3GPP TSG RAN #50), the study item CoMP was agreed upon for Release 11 as a tool to improve the coverage of high data rates, cell-edge throughput, and also to increase the overall system throughput. In a CoMP operation, multiple points coordinate with each other in such a way that the transmitted signals from/to other points do not incur serious interference or can even be exploited as meaningful signals. Theoretical work has shown that CoMP offers considerable potential performance gains in both the uplink and the downlink. For this reasons, CoMP has been studied as a solution to increasing system throughput, especially at the cell-edge areas where inter-cell interference (ICI) is severe more so with the traditional approaches. Network coding (NC) is another technique that has been receiving much attention recently, for its ability to improve spectral efficiency and achieve throughput optimality. By using network coding on CoMP schemes, the throughput of the wireless system is improved further because network coding brings about a new perspective which utilizes the interference instead of mitigating it. Exclusive-OR (XOR) coding, is one of the simple implementation of NC, by which two bits can be sent in only one transmission (by XORing them) instead of the normal two transmissions. The XOR operation of NC at the antenna is normally dubbed Analogue Network Coding (ANC) or Physical Layer Network Coding (PNC). Through the use of XOR coding, multiple faulty packets can be rectified by the receiver at the cost of transmitting an additional coded packet. Using XOR coding with CoMP, therefore, improves the BER performance and can also yield to a significant increase in the system throughput by aggressively allocating the transmission rate is most wireless communication systems. Space-time coding (STC) in multiple-input multiple-output (MIMO) systems has also recently attracted so much interest, due to the performance gains that they can accomplish. Transmit diversity is one of the MIMO algorithms used in the LTE-A standard and it belongs to the STC class of techniques. STCs are capable of delivering a diversity order equal to the product of the number of transmit and receive antennas. Space-time block codes (STBCs), one of the simplest implementation of STCs, can be regarded as a multi-antenna modulation and mapping technique that provides full diversity and results in simple encoders and decoders. One of the simplest forms of STBC is the Alamouti code defined for 2-transmit antennas cases. Transmit diversity using STBC has been deployed in various 3GPP and WiMAX standards. Space-frequency block coding (SFBC), one technique closely related to STBC, is the transmit diversity technique used in LTE-A standard. The use of STBC in LTE-A can also yield to an improvement in the link quality and reliability of the system. One major drawback in using transmit diversity techniques like STBC or SFBC is that they do not improve the data rate or spectral efficiency of the system. In this thesis, we propose a double STBC technique (based on the Alamouti code) that can be applied on a network coded CoMP downlink (DL) transmission scheme to exploit diversity gain plus offer a tremendous improvement in the data rate of the system. The proposed double STBC technique is also known as double space-time transmit diversity (DSTTD) scheme for high rate applications with 4 transmit antennas. The proposed scheme will apply the double STBC to a network coded DL Joint Processing (JP) CoMP transmission scheme and the scheme is to be known as; Space-time block coding with XOR coding for DL JP CoMP Transmission Scheme. Performance of this scheme based on bit-error rate (BER) and system data rate, will be evaluated (through simulations), and comparisons with the conventional Space-time block coded JP CoMP scheme will be made. The proposed scheme yields better performance more especially in terms of the data rate of the system, due to the combination of the double STTD (DSTTD) and network (XOR) coding techniques and suffers little bit in terms of BER performance compared to conventional CoMP scheme. The poor performance in BER may be attributed to the fact that our scheme uses fewer decoding iterations in the turbo decoder at the receiver, yet the more the number iterations the more accurate the operation becomes. Another reason would be that we used a simple receiver structure which uses Zero Forcing (ZF) algorithm as the detection mechanism which has a poor performance and a lower computational complexity when compared to other detection methods like (Minimum Mean Square Error) MMSE or Sphere Decoding (SD).

碩士<br>銘傳大學<br>資訊管理學系碩士班<br>99<br>In recent years, digital watermarking has been developed to protect the copyright and integrity of multimedia content, and fragile watermarking is used for image authentication. Fragile watermarking is the scheme that extracts and transforms the intensity into watermark and performs data hiding procedure to conceal the resultant watermark in the image. If the image has been altered, one can extract the hidden watermark to detect and localize the altered region. For the altered region, one can further perform image recovery procedure to restore the image by the hidden watermark. Many image verification schemes are based on block-wise technique. Such methods typically ignore the relationship between neighboring blocks. Besides, instead of combining verification information with recovery message into a single watermark, they usually treat these two messages as unrelated ones. Therefore, in this study, we try to develop a watermarking scheme which combines verification information with recovery message into one watermark. In such a way, we introduce the feasibility that the watermark can play two roles simultaneously, thereby reducing the detection error rate and increasing the recovery quality. Experimental results show that the proposed scheme has low detection error-rate and high recovery quality in comparison with other similar methods.

碩士<br>中原大學<br>電機工程研究所<br>97<br>In this thesis, we propose a scheme for gray-level images without pixel expansion. It solves the difficulty in carrying shares by using pixel expansion scheme and the requirement of more storage space. Our method can present three different levels of black sub-block and encrypt multi pixels at the same time. This makes the stacked image has better visual quality. In the proposed scheme, we utilize the method, block coding, to encrypt the secret image and reach the purpose of pixel unexpansion. At first, we divide the secret image (x × y pixels) into n sub-blocks which are 2×2 blocks. The sub-blocks can be grouped into three types by our manner. They are 0%, 50% and 100% black sub-blocks. Then, they will individually correspond to three different shades of the black blocks (50%, 75% and 100% black blocks) that are stacked sub-blocks through our coding rules. In addition, we offer an improvement that revises the position of 75% black stacked sub-blocks and it will get more similar with the secret image than the unimproved. The contributions in this thesis are as follows: (1) The size of the stacked image is the same as the secret image. This makes us to avoid wasting a lot of storage space and carry the shares easier. (2) The black blocks of three different degrees can be more delicate to show the secret information. It has better visual effect for the stacked image. (3) After revising the position of 75% black stacked sub-blocks, the stacked images will be more similar with the secret image. As expected, visual cryptography will be employed in future. We trust that results of our research in this thesis will be probably practical and efficient to establish a useful visual cryptography scheme with above advantages in applications.

碩士<br>國立虎尾科技大學<br>資訊工程系碩士班<br>106<br>With the development of the Internet, the channels to receiving information have been diverse. Recent progresses in social networking platforms have turned the Internet an indispensable part of our daily lives. However, the Internet is filled with all kinds of users. How to protect personal information from misappropriation and falsification is thus increasingly important. Data hiding is a technique that prevents secret data from being stolen in the transmission process. This study aimed to propose an improved reversible data hiding scheme for block truncation coded image by histogram shifting, where secret data were embedded in the cover images to generate stego images. Good image quality made users other than the receiving terminal hard to observe. The proposed reversible data hiding scheme was divided into two stages. In the first stage, secret data are embedded into the reconstruction values of block truncation codes of image. With the use of threshold values, blocks making stego image quality decrease after secret data were embedded were abandoned. In the second stage, two peak points together with the use of histogram shifting technique embeds secret data into bitmaps. Additional information was recorded as a reference for retrieving secret data and reconstructing original images. The coding rule proposed in this study was adopted to compress additional information and reduce the sizes of stego files. The results indicated that the proposed scheme featured large capacity for embedding secret data and high image quality of stego images.

碩士<br>國立清華大學<br>通訊工程研究所<br>97<br>One inherent drawback associated with multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems is the high peak-to-average power ratio (PAPR) at the transmitter’s output, and this usually causes undesirable nonlinear distortions. There have been a number of PAPR reduction techniques proposed for MIMO-OFDM systems, but their computational complexity is too high to be useful for practical applications. Besides, most of them cannot be used for MIMO-OFDM systems with space frequency block coding (SFBC). In this thesis, we propose a low-complexity PAPR reduction scheme for SFBC-based MIMO-OFDM systems. We first multiply the input sequence by a set of phase rotation vectors respectively and then utilize the linear property of SFBC to decompose each resulting sequence into several sub-sequences. After computing the inverse fast Fourier transform (IFFT) to convert each frequency-domain sub-sequence into a time-domain signal, we utilize the IFFT properties to do equivalent SFBC encoding operations in the time-domain for generating candidate signal sets, where the one with the lowest maximum PAPR is selected for transmission. Based on the proposed approach, we can obtain a large number of candidate signal sets by computing only a few IFFTs. Moreover, we reduce the complexity of selecting the optimal candidate signal set by setting a threshold to avoid generating unnecessary candidate signal sets. Simulation results show that, with lower computational complexity, the proposed scheme has comparable PAPR reduction performance to existing schemes for SFBC-based MIMO-OFDM systems.

碩士<br>國立暨南國際大學<br>電機工程學系<br>96<br>H.264/AVC standard has the best bit-rate reduction comparing to the previous video coding standards. Notably, since a bit in high compression coding contains much more information than it does in low compression coding, any single bit lost in high compression coding may result in the whole block’s loss and serious visual quality degradation for the decoded image at the receiver. If the error is not removed, the decoded image is still impaired. Therefore, this thesis proposes two error concealment algorithms for variable block size scheme to improve corrupted video images. First one, this thesis uses affine model to describe the relationship between corresponding feature points, then the affine parameters is determined by least squares estimation technique. The other one, this thesis proposes an optimal weighting interpolation method to recover the lost motion vectors. The weights are estimated by the technique of mean squared error minimization where the error is raised from the horizontal and vertical interpolations for the lost motion vectors. The simulation shows that, by using the proposed algorithms, the image recovery performance is significantly improved when the video sequence in transmission is corrupted. According to PSNR values, the proposed algorithm is superior to the other methods about 0.9~1.5dB.

碩士<br>國立臺中科技大學<br>資訊工程系碩士班<br>100<br>Motion estimation has been widely used in many video applications such as video compression, video segmentation, video surveillance and video tracking. Video encoding utilizes motion estimation and the property of the inter-frame relationship to achieve the data compression. Efficient Block Matching Algorithms (BMAs) have received considerable attention and adopted in modern video compression standards such as ISO/IEC MPEG1/2/4 and ITU-T H.263/H.264. Directional Gradient Descent Searches (DGDS) has better PSNR and lower search points compared with other well-known motion estimation algorithms. To reduce the computations, this thesis presents an efficient and fast motion estimation algorithm based on H.264/AVC video coding, named Modified Directional Gradient Descent Searches (MDGDS) to enhance the Directional Gradient Descent Searches algorithm, MDGDS uses three adaptive thresholds to achieve early termination in Directional Gradient Descent Searches. An additional search pattern with adaptive thresholds for early termination is applied to DGDS to avoid meaningless calculation after the searching point is good enough. The proposed algorithm evaluates the condition of early termination based on variety video sequence characteristics. The experimental results show that MDGDS has speed up the motion estimation run time and keep the video quality with eligible degradation. Keyword : motion estimation, Directional Gradient Descent Searches, video coding, early termination

Large-eddy simulation (LES) is emerging as a promising computational tool for reacting flows. High-order schemes for LES are desirable to achieve improved solution accuracy with reduced computational cost. In this study, a parallel, block-based, three-dimensional high-order central essentially non-oscillatory (CENO) finite-volume scheme for LES of premixed turbulent combustion is developed for Cartesian mesh. This LES formulation makes use of the flame surface density (FSD) for subfilter-scale reaction rate modelling. An algebraic model is used to approximate the FSD. A detailed explanation of the governing equations for LES and the mathematical framework for CENO schemes are presented. The CENO reconstruction is validated and is also applied to three-dimensional Euler equations prior to its application to the equations governing LES of reacting flows.

A parallel, block-based, adaptive mesh refinement, finite-volume scheme is developed and validated for the solution of the Favre-Averaged Navier-Stokes equations governing three-dimensional flow of a polytropic gas. The two-equation k-omega turbulence model is used to model the unresolved turbulent scales and their influence on the mean solution. The finite-volume spatial discretization is accomplished by using a finite-volume procedure on multiblock, body-fitted, hexahedral mesh. The inviscid flux functions make use of Roe's approximate Riemann solver. The viscous flux is evaluated using a diamond path reconstruction procedure on each cell boundary. Verification and validation of the solution method is accomplished through the application of the algorithm to a number of flow problems. The results from the application of the solution method to the flow problems are in good agreement with available experimental data. Therefore, the validity of the solution method for solving three-dimensional, turbulent flows is confirmed.

Rapid growth of cities has become a trend in most countries, this is caused by urbanisation wherein people move from the rural areas to the urban areas in search of employment. It goes without saying that such population needs housing. However, it is unusual to find land for housing in an already crowded place. Therefore, to curb this shortage in housing, countries like South Africa have resorted to adoption of fragmented property holding in and around the cities. Thus, in an attempt to curtail housing shortages in the urban area as well as land shortage, communal property schemes were adopted together with their governing legislation namely, Sectional Titles Act 95 of 1986, Share Blocks Act 59 of 1980 and Property Time-sharing Control Act 75 of 1983 to name a few. Likewise, Maseru, the capital city of Lesotho is also experiencing rapid growth in population. Hence, with the introduction of Lesotho’s Sectional Titles Bill 2013 came a ray of hope that the land and housing shortage in Maseru would be addressed. With this in mind, this suggested that the Government of Lesotho together with all concerned stakeholders thought it necessary to address this problem through the 2013 Bill which, for the most part follows the South African Sectional Titles Act of 1986. It is for this reason that this study was embarked on to show other forms of property holding akin to sectional titles as well as their regulation, which can all be used to eliminate housing shortages in Lesotho.<br>LLM (Estate Law), North-West University, Potchefstroom Campus, 2015