Iterative reduced-state decoding for coded partial-response channels

The conventional iterative decoding based on the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm rises exponentially in terms of channel memory length. In this paper, we propose a low-complexity soft-input/soft-output (SISO) channel detector based on tentative hard estimates fed back from the outer decoder in the previous iteration. The computational complexity of the proposed detector is polynomial in terms of the channel memory length. To demonstrate the performance/complexity tradeoff of the proposed detector, we present simulation results for 9-tap, 11-tap, and 12-tap channels. We show that the proposed detector significantly reduces the computational complexity with only slight performance degradation compared to the full-complexity BCJR algorithm.     

浅海水声信道中的一种带循环均衡的Turbo译码结构

针对浅海水声信道长时延、强多途干扰的特点,建立了一种新的带自适应循环判决反馈均衡的Turbo译码结构,并对其性能进行了仿真研究.该结构对典型的Turbo译码器进行了改进,使之不但能输出信息比特,同时又能输出校验比特,这些比特经硬判决、符号映射及信道交织后反馈回判决反馈均衡器,构成带自适应循环判决反馈均衡的Turbo译码结构.厦门港实测5途浅海水声信道仿真结果显示,该结构具有优良的抗多途性能,信噪比大于4dB时,误比特率小于10-5,比联合判决反馈均衡的Turbo译码结构提高了约2.5dB.     

A new LDPC decoding algorithm aided by segmented cyclic redundancy checks for magnetic recording channels

We introduce a new low-density parity-check (LDPC) decoding algorithm that exploits the cyclic redundancy check (CRC) information of data segments. By using the error detection property of the CRC, we can successively decode data segments of a codeword corrupted by random errors and erasures. The key idea is that the messages from the variable nodes with correct checksum are fixed to deterministic log likelihood ratio values during LDPC iterative decoding. This approach improves the decoding speed and codeword error rate without significant modification of the LDPC decoding structure. Moreover, the CRC is also used for an early stopping criterion of LDPC decoding. Simulation results verify our claims.     

Fast method for precoding and decoding of distributive multi-input multi-output channels in relay-based decode-and-forward cooperative wireless networks

It is well-known that the performance of the relay-based decode-and-forward (DF) cooperative networks outperforms the performance of the amplify-and-forward cooperative networks. However, this performance improvement is accomplished at the expense of adding more signal processing complexity (precoding/decoding) at each relay node. In this study, the authors tackle this signal processing complexity issue by proposing a Jacket-based fast method for reducing the precoding/decoding complexity in terms of time computation. Jacket transforms have shown to find applications in signal processing and coding theory. Jacket transforms are defined to be n x n matrices A = (a_jk) over a field F with the property AA^† = n/_n, where A^† is the transpose matrix of the element-wise inverse of A, that is, A^† = (a^-1_{kj,/sub>), which generalise Hadamard transforms and centre weighted Hadamard transforms. In particular, exploiting the Jacket transform properties, the authors propose a new eigenvalue decomposition (EVD) method with application in precoding and decoding of distributive multi-input multi-output channels in relay-based DF cooperative wireless networks in which the transmission is based on using single-symbol decodable space-time block codes. The authors show that the proposed Jacket-based method of EVD has significant reduction in its computational time as compared to the conventional-based EVD method. Performance in terms of computational time reduction is evaluated quantitatively through mathematical analysis and numerical results.}     

Diffusion method of routing in channels with storage areas

Abstract

The diffusion equation of flood wave propagation in channels with storage areas has been derived and its solution is expressed in the form of error functions. From this solution, two types of peak discharge are identified. Their behaviors are examined and compared with numerical solution of complete equations of motion and continuity. A subsidence parameter is defined in terms of diffusion coefficient and inflow characteristics, and evaluated from the results of numerical solution. Hydrographs computed using the diffusion method compares favorably to those obtained from the numerical solution.     

Information rates of multidimensional front ends for digital storage channels with data-dependent transition noise

This paper presents a simulation-based method for the computation of the information rates of recently proposed multidimensional front ends for digital storage channels with transition noise. First, we propose an algorithm, based on linear prediction and state reduction techniques, that extends recent work on the information rates of magnetic recording channels affected by colored Gaussian thermal noise, intersymbol interference, and signal-dependent transition noise. Following a previous study on statistical sufficiency, we apply this algorithm to compute the information rates of digital storage systems featuring a multidimensional detection front end. The resulting information rates indicate that significant gains may be achievable by multidimensional signal processing techniques in transition-noise-limited digital storage channels.     

Discrete magnitude-squared channel modeling, equalization, and detection for volume holographic storage channels

As storage density increases, the performance of volume holographic storage channels is degraded, because intersymbol interference and noise also increase. Equalization and detection methods must be employed to mitigate the effects of intersignal interference and noise. However, the output detector array in a holographic storage system detects the intensity of the incident light's wave front, leading to loss of sign information. This sign loss precludes the applicability of conventional equalization and detection schemes. We first address channel modeling under quadratic nonlinearity and develop an efficient model named the discrete magnitude-squared channel model. We next introduce an advanced equalization method called the iterative magnitude-squared decision feedback equalization (IMSDFE), which takes the channel nonlinearity into account. The performance of IMSDFE is quantified for optical-noise-dominated channels as well as for electronic-noise-dominated channels. Results indicate that IMSDFE is a good candidate for a high-density, high-intersignal-interference volume holographic storage channel.     

Improvements in the capacity of computer-generated holographic storage using the Lee method with sparse multivalued reconstructions

The use of sparse multivalued data encodings for the purpose of increasing the capacity of parallel-access optical memories based on Fourier-transform computer-generated holography is discussed. Results based on the Lee method indicate that a sparse encoding of nonbinary data words can be used to increase the storage-area utilization efficiency from 35% to > 70%. It is also found that for signal-to-noise ratios greater than 200, five-level data encoding can be used to achieve bit error rates less than 10(-12) reliably with 60% area efficiency.     

Partial permutation decoding for MacDonald codes

We show how to find s-PD-sets of the minimal size \(s+1\) for the \(\left[ \frac{q^n-q^u}{q-1},n,q^{n-1}-q^{u-1}\right] _q \) MacDonald q-ary codes \(C_{n,u}(q)\) where \(n \ge 3\) and \(1 \le u \le n-1\). The construction of [6] can be used and gives s-PD-sets for s up to the bound \(\lfloor \frac{q^{n-u}-1}{(n-u)(q-1)} \rfloor -1\), of effective use for u small; for \(u \ge \lfloor \frac{n}{2} \rfloor \) an alternative construction is given that applies up to a bound that depends on the maximum size of a set of vectors in \(V_u(\mathbb {F}_q)\) with each pair of vectors distance at least 3 apart.     

一种新型廉价、环境友好、结构稳定且具有大离子通道的钾离子电池正极材料

得益于钾的地壳丰度及其与锂的化学相似性,钾离子电池有望应用于大规模储能领域.目前,钾离子电池的性能尚不能满足实用需求,主要原因在于缺乏合适的正极材料.基于硫酸根的强诱导效应和草酸体系制备亚铁化合物的优势,本文制备了一种新型廉价、环境友好且稳定的储钾正极材料K₄Fe₃(C₂O₄)₃(SO₄)₂.其独特的二维层状晶体结构具有3.379?的层间距,且层内具有4.576×6.846?的大环.根据第一性原理计算,该结构有利于钾离子的可逆迁移,且体积变化仅为6.4%.不同充放电态样品的同步辐射X射线吸收光谱和XRD、半电池以及全电池的电化学表征证实了其优异的电化学可逆性和结构稳定性.通过成分调控、掺杂、结构优化等策略,K₄Fe₃(C₂O₄)₃(SO₄)₂正极材料的电化学性能有望进一步提升.因此,本工作为廉价、环保的储钾正极材料提供了一种新的稳定晶体模型.     

Improvements in a Calorimeter for High-Power CW Lasers

Measurement certainty with the BB series of electrically calibrated calorimeters for high-energy lasers has been enhanced by the addition of monitors for energy backscattered from the meter and for energy missing the entrance aperture (overspill). The performance and design features of the recently constructed BB2 meter are compared with the previously described BB1 meter. Direct intercomparison shows the agreement between meters to be 1 percent.     

Two new decoding algorithms for Reed-Solomon codes

The subject of decoding Reed-Solomon codes is considered. By reformulating the Berlekamp and Welch key equation and introducing new versions of this key equation, two new decoding algorithms for Reed-Solomon codes will be presented. The two new decoding algorithms are significant for three reasons. Firstly the new equations and algorithms represent a novel approach to the extensively researched problem of decoding Reed-Solomon codes. Secondly the algorithms have algorithmic and implementation complexity comparable to existing decoding algorithms, and as such present a viable solution for decoding Reed-Solomon codes. Thirdly the new ideas presented suggest a direction for future research. The first algorithm uses the extended Euclidean algorithm and is very efficient for a systolic VLSI implementation. The second decoding algorithm presented is similar in nature to the original decoding algorithm of Peterson except that the syndromes do not need to be computed and the remainders are used directly. It has a regular structure and will be efficient for implementation only for correcting a small number of errors. A systolic design for computing the Lagrange interpolation of a polynomial, which is needed for the first decoding algorithm, is also presented.This research was supported by a grant from the Canadian Institute for Telecommunications Research under the NCE program of the Government of Canada     

Improvements in CVD diamond properties for radiotherapy dosimetry

The goal of this work was to compare the behaviour of a chemical vapour deposited (CVD) diamond sample, grown at the University of Florence using a local procedure, with that of a commercial CVD diamond. The comparison was performed exposing both systems to 25 MV photons and measuring the current response during irradiation. Properties of dosimetric interest such as stability of response, dose rate dependence and rise time were investigated. After a preliminary study, which evidenced better performances of the commercial device with respect to the local CVD diamond, the latter was irradiated with a high fluence of fast neutrons. As a result of the neutron treatment, the quality of the CVD home-made diamond has been improved to match with that of the commercial dosemeter.     

Indirect decoding edges for one-shot shape acquisition

Determining the correspondence in coded structured light is challenging, but it is very important in one-shot techniques for 3D shape reconstruction. The problem of decoding stripe patterns can be modeled as matching two code sequences. We propose decoding edges indirectly based on the property of the stripe pattern, which can be represented as edge code, color code, or mixed code sequences. While traditional methods match two edge code sequences, indirect decoding matches two color sequences or mixed code sequences. The advantages of the proposed method, including a higher Hamming distance, enforced local coherence, and more code information, make indirect decoding excellent in performance. Previously, the lack of ground truth has prevented direct comparisons of different decoding algorithms. Here we obtain six benchmark datasets using the robust space-time analysis. Five decoding methods are quantitatively evaluated using the ground truth. The comparison results show that our method is robust for complex code situations and that it outperforms the state-of-the-art technique in this area.     

矿用云台解码驱动器的设计

针对矿用云台解码驱动器工作环境恶劣的情况 ,采用MSP4 30芯片作为主要接收控制芯片 ,设计了矿用云台解码驱动器 ;同时 ,采用固态继电器 ,增强安全可靠性。     

A decoding algorithm for unique correspondence in range data acquisition

An efficient algorithm is presented for solving the correspondence problem for a computer vision system which uses encoded structured light. The structured lighting system is composed of a matrix pattern of primitives projected into the scene. The decoding algorithm determines the index in the matrix pattern of each imaged point. Once the index is found, correspondence is solved by using triangulation. Examples of the algorithm are presented.     

数字高速视频图像的解码算法

对数字化高速视频解码提出了一种改良方法:进行线性解码插值时,对原采样点样本再进 行一次平均补偿,克服颗粒噪声;采用三次插值时,调整负系数比例,补偿γ值的非线性效应,能有效克服颜色错位和“振铃”效应等。理论分析和实验均表明,该算法较好地适应于数字化高速视频解码。     

Improvements for the ultra weak variational formulation

In this paper, we investigate strategies to improve the accuracy and efficiency of the ultra weak variational formulation (UWVF) of the Helmholtz equation. The UWVF is a Trefftz type, nonpolynomial method using basis functions derived from solutions of the adjoint Helmholtz equation. We shall consider three choices of basis function: propagating plane waves (original choice), Bessel basis functions, and evanescent wave basis functions. Traditionally, two‐dimensional triangular elements are used to discretize the computational domain. However, the element shapes affect the conditioning of the UWVF. Hence, we investigate the use of different element shapes aiming to lower the condition number and number of degrees of freedom. Our results include the first tests of a plane wave method on meshes of mixed element types. In many modeling problems, evanescent waves occur naturally and are challenging to model. Therefore, we introduce evanescent wave basis functions for the first time in the UWVF to tackle rapidly decaying wave modes. The advantages of an evanescent wave basis are verified by numerical simulations on domains including curved interfaces.Copyright © 2013 John Wiley & Sons, Ltd.