Large Block Sizes Research Articles

On the Minimum Distance of Turbo Codes With Quadratic Permutation Polynomial Interleavers

An interleaver is a critical component for the channel coding performance of turbo codes. Algebraic constructions are of particular interest because they admit analytical designs and simple, practical hardware implementations. Also, the recently proposed quadratic permutation polynomial (QPP)-based interleavers by Sun and Takeshita have provided excellent performance for short-to-medium block lengths, and have been selected for the 3GPP LTE standard. In this paper, we derive some upper bounds on the best achievable minimum distance dmin of QPP-based conventional binary turbo codes (with tailbiting termination, or dual termination when the interleaver length N is sufficiently large) that are tight for larger block sizes. In particular, we show that the minimum distance is at most 2(2v+1 + 9), independent of the interleaver length, when there exists an inverse polynomial of degree two, where v is the degree of the primitive feedback and monic feedforward polynomials. However, allowing the QPP to have no inverse polynomials of degree two may give strictly larger minimum distances (and lower multiplicities). In particular, we provide several QPPs with no quadratic inverse for some of the 3GPP LTE interleaver lengths giving a dmin with the 3GPP LTE constituent encoders which is strictly larger than 50. For instance, we have found a QPP for N = 6016 which gives an estimated dmin of 57. Furthermore, we provide the exact minimum distances and the corresponding multiplicities for all 3GPP LTE turbo codes (with dual termination) which shows that the best minimum distance is 51. Finally, we compute the best achievable minimum distances with QPP interleavers for all 3GPP LTE interleaver lengths N ≤ 4096, and compare these minimum distances with the ones we get when using the 3GPP LTE polynomials.

Accuracy and precision of variance components in occupational posture recordings: a simulation study of different data collection strategies

BackgroundInformation on exposure variability, expressed as exposure variance components, is of vital use in occupational epidemiology, including informed risk control and efficient study design. While accurate and precise estimates of the variance components are desirable in such cases, very little research has been devoted to understanding the performance of data sampling strategies designed specifically to determine the size and structure of exposure variability. The aim of this study was to investigate the accuracy and precision of estimators of between-subjects, between-days and within-day variance components obtained by sampling strategies differing with respect to number of subjects, total sampling time per subject, number of days per subject and the size of individual sampling periods.MethodsMinute-by-minute values of average elevation, percentage time above 90° and percentage time below 15° were calculated in a data set consisting of measurements of right upper arm elevation during four full shifts from each of 23 car mechanics. Based on this parent data, bootstrapping was used to simulate sampling with 80 different combinations of the number of subjects (10, 20), total sampling time per subject (60, 120, 240, 480 minutes), number of days per subject (2, 4), and size of sampling periods (blocks) within days (1, 15, 60, 240 minutes). Accuracy (absence of bias) and precision (prediction intervals) of the variance component estimators were assessed for each simulated sampling strategy.ResultsSampling in small blocks within days resulted in essentially unbiased variance components. For a specific total sampling time per subject, and in particular if this time was small, increasing the block size resulted in an increasing bias, primarily of the between-days and the within-days variance components. Prediction intervals were in general wide, and even more so at larger block sizes. Distributing sampling time across more days gave in general more precise variance component estimates, but also reduced accuracy in some cases.ConclusionsVariance components estimated from small samples of exposure data within working days may be both inaccurate and imprecise, in particular if sampling is laid out in large consecutive time blocks. In order to estimate variance components with a satisfying accuracy and precision, for instance for arriving at trustworthy power calculations in a planned intervention study, larger samples of data will be required than for estimating an exposure mean value with a corresponding certainty.

Error-correcting codes for reliable communications in microgravity platforms

The PAANDA experiment was conceived to characterise the acceleration ambient of a rocket launched microgravity platform, specially the microgravity phase. The recorded data was transmitted to ground stations, leading to loss of telemetry information sent during the re-entry period. Traditionally, an error-correcting code for this channel consists of a block code with very large block size to protect against long periods of data loss. Instead, we propose the use of digital fountain codes along with conventional Reed-Solomon block codes to protect against long and short burst error periods, respectively. Aiming to use this approach for a second version of PAANDA to prevent data corruption, we propose a model for the communication channel based on information extracted from Cuma II’s telemetry data, and simulate the performance of our proposed error-correcting code under this channel model. Simulation results show that nearly all telemetry data can be recovered, including data from the re-entry period.

Identifying universality classes of absorbing phase transitions by block renormalization

We propose a renormalization scheme that can be used as a reliable method to identifyuniversality classes of absorbing phase transitions. Following the spirit of Wilson’sblock-spin renormalization group, the lattice is divided into blocks, assigning tothem an effective state by a suitable Boolean function of the interior degreesof freedom. The effective states of adjacent blocks form certain patterns whichare shown to occur with universal probability ratios if the underlying process iscritical. Measuring these probability ratios in the limit of large block sizes, oneobtains a set of universal numbers as an individual fingerprint for each universalityclass.

Design space exploration for sparse matrix‐matrix multiplication on FPGAs

SUMMARYThe design and implementation of a sparse matrix‐matrix multiplication architecture on field‐programmable gate arrays is presented. Performance of the design, in terms of computational latency, as well as the associated power‐delay and energy‐delay tradeoff are studied. Taking advantage of the sparsity of the input matrices, the proposed design allows user‐tunable power‐delay and energy‐delay tradeoffs by employing different number of processing elements (PEs) in the architecture design and different block size in the blocking decomposition. Such ability allows designers to employ different on‐chip computational architecture for different system power‐delay and energy‐delay requirements. It is in contrast to conventional dense matrix‐matrix multiplication architectures that always favor the maximum number of PEs and largest block size. In our implementation, the better energy consumption and power‐delay product favors less PEs and smaller block size for the 90%‐sparsity matrix‐matrix multiplications. Although in order to achieve better energy‐delay product, more PEs and larger block size are preferred. Copyright © 2011 John Wiley & Sons, Ltd.

Low-power way-predicting cache based on intrablock access

The conventional way-predicting cache can effectively reduce power consumption, due to only speculatively selecting an MRU (most recently used) way before starting a normal cache access. However, for accessing the data within the same cache block, to fetch an MRU table and an MRU tag-subarray is unnecessary. Especially for executing a program with good locality, the probability to access the intrablock data in the cache is more significant. Focusing on the way-predicting cache based on intrablock data access, we propose a new cache scheme that can judge if the present cache access is an intrablock, and then only directly enable one data-subarray. By this approach the proposed scheme is a further improvement on average energy savings over the conventional way-predicting cache, especially for large block sizes and good program locality. Therefore, such a way-predicting cache based on intrablock access indeed provides another solution for the design of low-power caches.

Development of a multiple‐hole die for the production of single large blocks of low‐density polystyrene using carbon dioxide as a blowing agent

AbstractA multiple‐hole die for the production of single large blocks of polystyrene foam with carbon dioxide as blowing agent was developed. First, single‐hole die experiments were carried out with different hole sizes (2.0, 1.0, and 0.50 mm). Using these single‐hole dies dimensionally‐stable foam was produced with a density of 31 kg m−3 and an open cell structure. Next, the hole diameter and hole distances for a newly constructed multiple‐hole die were chosen on basis of the radial expansion in the single‐hole die experiments. Tests with the multiple‐hole die showed that the seven strings could melt together forming one large string with a diameter of about 20 mm and a density of 50 kg m−3. Therefore, the concept of using a multiple‐hole die for producing single large blocks of polystyrene was proven. However, larger block sizes were not possible because of the limited capabilities of the extruder. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Improved differential pulse code modulation-block truncation coding method adopting two-level mean squared error near-optimal quantizers

The conventional hybrid method of block truncation coding (BTC) and differential pulse code modulation (DPCM), namely the DPCM-BTC method, offers better rate-distortion performance than the standard BTC. However, the quantization error in the hybrid method is easily increased for large block sizes due to the use of two representative levels in BTC. In this paper, we first derive a bivariate quadratic function representing the mean squared error (MSE) between the original block and the block reconstructed in the DPCM framework. The near-optimal representatives obtained by quantizing the minimum of the derived function can prevent the rapid increase of the quantization error. Experimental results show that the proposed method improves peak signal-to-noise ratio performance by up to 2dB at 1.5 bit/pixel (bpp) and by 1.2dB even at a low bit rate of 1.1 bpp as compared with the DPCM-BTC method without optimization. Even with the additional computation for the quantizer optimization, the computational complexity of the proposed method is still much lower than those of transform-based compression techniques.

Fast mode selection for H.264 video coding standard based on motion region classification

H.264/AVC achieves higher compression efficiency than previous video coding standards. However, the process of selecting the optimal coding mode for each macroblock (MB) results in extremely high computation complexity, which make it difficult for practical use. In this paper, an efficient algorithm is proposed to reduce the complexity of MB mode selection. The proposed algorithm identified the interior region of the motion object by using the motion vectors information firstly. For the interior region surrounded by the identical motion vectors, we skip the mode selection of the MBs and then treat them with large block size modes directly. We also discuss the specific examples in this region. For the boundary region, we classify them into different types according to the coded mode information. After that we process the different regions with different mode set distinctly. Experimental results show that the proposed algorithm can save the encoding time up to 46% on average compared to the conventional method in the JVT JM8.6 reference encoder with only 0.12 dB performance degradation.

Brick tunnel randomization for unequal allocation to two or more treatment groups

Studies with unequal allocation to two or more treatment groups often require a large block size for permuted block allocation. This could present a problem in small studies, multi-center studies, or adaptive design dose-finding studies. In this paper, an allocation procedure, which generalizes the maximal procedure by Berger, Ivanova, and Knoll to the case of K≥2 treatment groups and any allocation ratio, is offered. Brick tunnel (BT) randomization requires the allocation path drawn in the k-dimensional space to stay close to the allocation ray that corresponds to the targeted allocation ratio. Specifically, it requires the allocation path to be confined to the set of the k-dimensional unitary cubes that are pierced by the allocation ray (the 'brick tunnel'). The important property of the BT randomization is that the transition probabilities at each node within the tunnel are defined in such a way that the unconditional allocation ratio is the same for every allocation step. This property is not necessarily met by other allocation procedures that implement unequal allocation.

Frame Rate Up-Conversion Technique Using Hardware-Efficient Motion Estimator Architecture for Motion Blur Reduction of TFT-LCD

Motion blur in TFT-LCD is caused by sample and hold characteristic, slow response time of liquid crystal, and the inconsistency between object tracking of the human eye and the actual object location. In order to solve this problem, a high frame rate driving method based on motion estimation and motion compensation has been applied to LCD products. However, as the required processing time of motion estimation increases in LCD TV and monitor systems, real-time video image processing becomes more difficult. Frame interpolation through the large macro block (MB) size has limitations to detect small objects. So, this paper proposes the efficient motion estimator architecture which uses seven kinds of macro blocks to enhance the accuracy of motion estimation and combines the parallel processing with pre-computation technology and hardware optimization for high-speed processing. Also, for increased efficiency in the hardware architecture, we employed an I2C (Inter Integrated Circuit) communication unit to control the key parameters easily through the personnel computer. Simulation results show that the critical path at the motion estimator is reduced by about 27.47% compared to the conventional structure. As a result, the proposed motion estimator will be applicable for the high-speed frame interpolation of variable video.

Universal parity effects in the entanglement entropy ofXX chains with open boundary conditions

We consider the Rényi entanglement entropies in the one-dimensionalXX spin-chains with open boundary conditions in the presence of a magnetic field. In the caseof a semi-infinite system and a block starting from the boundary, we derive rigorously theasymptotic behavior for large block sizes on the basis of a recent mathematical theorem forthe determinant of Toeplitz plus Hankel matrices. We conjecture a generalizedFisher–Hartwig form for the corrections to the asymptotic behavior of this determinantthat allows the exact characterization of the corrections to the scaling at order for any n. By combining these results with conformal field theory arguments, we derive exactexpressions also in finite chains with open boundary conditions and in the case when theblock is detached from the boundary.

Video Coding Using a Simplified Block Structure and Advanced Coding Techniques

This paper describes a new video coding scheme based on a simplified block structure that significantly outperforms the coding efficiency of the ISO/IEC 14496-10 ITU-T H.264 advanced video coding (AVC) standard. Its conceptual design is similar to a typical block-based hybrid coder applying prediction and subsequent prediction error coding. The basic coding unit is an 8 × 8 block for inter, and an 8 × 8 or a 16 × 16 block for intra, instead of the usual 16 × 16 macroblock. No larger block sizes are considered for prediction and transform. Based on this simplified block structure, the coding scheme uses simple and fundamental coding tools with optimized encoding algorithms. In particular, the motion representation is based on a minimum partitioning with blocks sharing motion borders. In addition, compared to AVC, the new and improved coding techniques include: block-based intensity compensation, motion vector competition, adaptive motion vector resolution, adaptive interpolation filters, edge-based intra prediction and enhanced chrominance prediction, intra template matching, larger trans forms and adaptive switchable transforms selection for intra and inter blocks, and nonlinear and frame-adaptive de-noising loop filters. Finally, the entropy coder uses a generic flexible zero tree representation applied to both motion and texture data. Attention has also been given to algorithm designs that facilitate parallelization. Compared to AVC, the new coding scheme offers clear benefits in terms of subjective video quality at the same bit rate. Objective quality improvements are equally significant. At the same quality, an average bit-rate reduction of 31% compared to AVC is reported.

Fano resonances and entanglement entropy

We study the entanglement in the ground state of a chain of free spinless fermions with a single side-coupled impurity. We find a logarithmic scaling for the entanglement entropy of a segment neighboring the impurity. The prefactor of the logarithm varies continuously and contains an impurity contribution described by a one-parameter function while the contribution of the unmodified boundary enters additively. The coefficient is found explicitly by pointing out similarities with other models involving interface defects. The proposed formula gives excellent agreement with our numerical data. If the segment has an open boundary, one finds a rapidly oscillating subleading term in the entropy that persists in the limit of large block sizes. The particle-number fluctuation inside the subsystem is also reported. It is analogous with the expression for the entropy scaling, however, with a simpler functional form for the coefficient.

Weakly-Constrained Codes for Suppression of Patterning Effects in Digital Communications

We propose weakly-constrained stream and block codes with tunable pattern-dependent statistics and demonstrate that the block code capacity at large block sizes is close to the the prediction obtained from a simple Markov model published earlier. We demonstrate the feasibility of the code by presenting original encoding and decoding algorithms with a complexity log-linear in the block size and with modest table memory requirements. We also show that when such codes are used for mitigation of patterning effects in optical fibre communications, a gain of about 0.5 dB is possible under realistic conditions, at the expense of small redundancy (≈10%).

A block Chebyshev–Davidson method with inner–outer restart for large eigenvalue problems

We propose a block Davidson-type subspace iteration using Chebyshev polynomial filters for large symmetric/hermitian eigenvalue problem. The method consists of three essential components. The first is an adaptive procedure for constructing efficient block Chebyshev polynomial filters; the second is an inner–outer restart technique inside a Chebyshev–Davidson iteration that reduces the computational costs related to using a large dimension subspace; and the third is a progressive filtering technique, which can fully employ a large number of good initial vectors if they are available, without using a large block size. Numerical experiments on several Hamiltonian matrices from density functional theory calculations show the efficiency and robustness of the proposed method.

Bayesian Error Concealment With DCT Pyramid for Images

In this paper, the problem of concealing missing image blocks is casted into a framework of Bayesian estimation. The conditional expectation of the missing block vector is taken over a pilot vector of correctly decoded pixels near the missing block. Multiple observations of the missing vector and pilot vectors obtained in a neighborhood are used to approximate the expectation. We design a multiscale estimation approach with discrete cosine transform pyramid to improve estimation efficiency. The DC image of the missing block is recovered first, and then more details related to high-frequency AC coefficients are recovered successively. Moreover, the algorithm operates in an iterative mode through using estimated block to refine the searching process for the next estimation. The algorithm is found to perform very well for a wide range of block loss rates. Substantial improvement over 14 existing error concealment (inclusive of inpainting) algorithms on various images is demonstrated in our extensive experiments, under different test conditions inclusive of high-loss rates and large block sizes.

An efficient inter-frame coding with intra skip decision in H.264/AVC

In this paper, we propose a simple but effective intra-mode skip algorithm to reduce the computational cost for inter-frame coding. It makes use of motion, temporal, and spatial homogeneity characteristics of video sequences. Specifically, the motion homogeneity is defined by using the mean deviation of motion vectors (MV) of the 4×4 blocks. The temporal and spatial homogeneity are computed by the sum of absolute difference (SAD) between an original block and its prediction block of the best inter-mode and the intra-mode with large block size, respectively. Based on the three types of homogeneity, the proposed method skip the full intra-mode search for inter-frame coding to reduce the encoding time when a region has the motion homogeneity and temporal homogeneity is stronger than the spatial one. Experimental results demonstrate that the proposed algorithm significantly increases the skip decision accuracy by up to 20% and reduces the total encoding time by about 3~10% as compared to the existing methods with negligible loss in PSNR and small increment of bit rate.

Evaluation of digital image correlation techniques using realistic ground truth speckle images

Digital image correlation (DIC) has been acknowledged and widely used in recent years in the field of experimental mechanics as a contactless method for determining full field displacements and strains. Even though several sub-pixel motion estimation algorithms have been proposed in the literature, little is known about their accuracy and limitations in reproducing complex underlying motion fields occurring in real mechanical tests. This paper presents a new method for evaluating sub-pixel motion estimation algorithms using ground truth speckle images that are realistically warped using artificial motion fields that were obtained following two distinct approaches: in the first, the horizontal and vertical displacement fields are created according to theoretical formulas for the given type of experiment while the second approach constructs the displacements through radial basis function interpolation starting from real DIC results. The method is applied in the evaluation of five DIC algorithms with results indicating that the gradient-based DIC methods generally have a quality advantage when using small sized blocks and are a better choice for calculating very small displacements and strains. The Newton–Raphson is the overall best performing method with a notable quality advantage when large block sizes are employed and in experiments where large strain fields are of interest.

A Block Cipher Generation Using Color Substitution

most influential and universal approach to countering the threats to network / information security is encryption. Even though it is very authoritative, the cryptanalysts are very intelligent and they were working day and night to break the ciphers. To make a stronger cipher it is recommended that to use: More stronger and complicated encryption algorithms, Keys with more number of bits (Longer keys), larger block size as input to process, use authentication and confidentiality and secure transmission of keys. It is certain that, if we follow all the mentioned principles, can make a very stronger cipher. With this we have the following problems: It is a time consuming process for both encryption and decryption, It is difficult for the crypt analyzer to analyze the problem. Also suffers with the problems in the existing system. The main intention of this paper is to present an innovative cryptographic Substitution method, can generate stronger cipher then the existing substitution algorithms. We are sure that concept is new and the cryptanalysis did on this will prove that the cipher is strong.