An analysis of the block error probability performance of iterative decoding

Asymptotic iterative decoding performance is analyzed for several classes of iteratively decodable codes when the block length of the codes N and the number of iterations I go to infinity. Three classes of codes are considered. These are Gallager's regular low-density parity-check (LDPC) codes, Tanner's generalized LDPC (GLDPC) codes, and the turbo codes due to Berrou et al. It is proved that there exist codes in these classes and iterative decoding algorithms for these codes for which not only the bit error probability P/sub b/, but also the block (frame) error probability P/sub B/, goes to zero as N and I go to infinity.     

一种降低定位误差的无线传感器网络节点定位改进算法

本文针对无线传感器网络节点的定位精度问题,提出了一种采用误差修正的方法来降低累积距离误差和定位误差的传感器网络节点定位改进算法,给出了该算法的基本原理与实现方法.该算法在不增加原算法通信量及计算复杂度的基础上提高了定位精度.仿真结果显示,在同等条件下,本文提出的算法定位精度提高了5～10%.     

一种适用于ADI-FDTD法的非分裂式完全匹配层

基于FDTD法中场量D-H(电位移矢量-磁场强度)迭代公式,导出了适用于AD I-FDTD法的场量非分裂式完全匹配层(PML)的实现方案,与现有的其它AD I-FDTD法的PML技术相比,具有物理概念清晰、易于操作并节省计算机资源的优点。数值结果证明:该PML技术能有效地解决吸收边界的问题,为AD I-FDTD法的发展与推广应用提供了条件。     

An efficient PML implementation for the ADI-FDTD method

A novel implementation of the perfectly matched layer (PML) absorber for the alternating-direction implicit finite-difference time-domain method is proposed and implemented. It is shown that, compared to the traditional PML implementation, the performance of the proposed PML is more efficient for large Courant numbers.     

Serially concatenated continuous phase modulation with reduced iterative demodulation and detection

A reduced state Soft Input Soft Output （SISO） a posteriori probability algorithm for Serially Concatenated Continuous Phase Modulation （SCCPM） is proposed in this paper. Based on the Reduced State Sequence Detection （RSSD）, it has more general form compared with other reduced state SISO algorithms. The proposed algorithm can greatly reduce the state number, thus leads to the computation complexity reduction. It also minimizes the degradation in Euclidean distance with decision feedback in the reduced state trellis. Analysis and simulation results show that the performance degradation is little with proper reduction scheme.     

An improved ADI-FDTD method and its application to photonicsimulations

When the alternating direction implicit-finite difference time domain method (ADI-FDTD) is applied to simulating photonic devices, full efficiency can not be achieved if reasonable accuracy is to be kept, due to numerical errors such as numerical dispersion. A simple modification to ADI-FDTD is proposed by calculating the envelope rather than the fast-varying field, so that errors are minimized. A factor of two-five in speed can usually be gained while retaining the same level of accuracy compared with conventional FDTD. The efficiency and the accuracy of this improved approach is demonstrated on several problems, from simple waveguide structures to complex photonic crystal structures     

一种色散介质中的低误差ADI-FDTD 算法

交变方向隐式时域有限差分（ADI-FDTD）能够克服传统时域有限差分算法中稳定性条件对时间步长的限制,从而提高计算效率,但是在大步长时其误差较大。ER（低误差）-ADI-FDTD 方法通过补偿截断误差项,提高了计算精度,但是目前仅给出二维非色散条件下的形式。在ER-ADI-FDTD 的基础上,提出了一种色散介质中的低误差D-ER-ADI-FDTD 算法,推导出了完整的三维计算公式。最后通过计算和结果比较对算法进行检验。     

Joint iterative decoding of serially concatenated error controlcoded CDMA

Joint iterative decoding of multiple forward error control (FEC) encoded data streams is studied for linear multiple access channels, such as code-division multiple access (CDMA). It is shown that such systems can be viewed as serially concatenated coding systems, and that iterative soft-decision decoding can be performed successfully To improve power efficiency, powerful FEC codes are used. These FEC codes are themselves serially concatenated. The overall transmission system can be viewed as the concatenation of two error control codes with the linear multiple access channel, and soft-decision decoders are used at each stage. A variance transfer function approach applied to the analysis of this system captures the role of the component decoders in an overall iterative decoding system. We show that this approach forms a methodology to study the effects of the component codes as well as that of the iteration schedule. Analysis and simulation examples are presented for transmission systems that operate close to the Shannon limit and illustrate the accuracy of the analysis     

An efficient method to reduce the numerical dispersion in the ADI-FDTD

A new approach to reduce the numerical dispersion in the finite-difference time-domain (FDTD) method with alternating-direction implicit (ADI) is studied. By adding anisotropic parameters into the ADI-FDTD formulas, the error of the numerical phase velocity can be controlled, causing the numerical dispersion to decrease significantly. The numerical stability and dispersion relation are discussed in this paper. Numerical experiments are given to substantiate the proposed method.     

一种有效减少ADI-FDTD数值色散的方法

ADI—FDTD算法的数值色散效应较为明显，本文的研究表明一种通过添加各向异性媒质来修正相速误差，从而减少FDTD数值色散的方法，同样适用于ADI-FDTD，且收效更为显著。数值运算结果证明该方法能够简单有效地去除较宽频带范围内的色散。     

基于非零散度关系的交替方向隐式减缩FDTD算法

该文证明了即使在无源区域,交替方向隐式时域有限差分法(ADI-FDTD)所给出的电磁场量不满足零散度关系,同时推导出了该散度关系的具体表达式。基于该非零散度关系,将不受Courant稳定条件限制的ADI-FDTD法和能节约最多达1/3内存的减缩时域有限差分(R-FDTD)法结合,提出了一种新的交替方向隐式减缩FDTD算法。该算法保留了ADI-FDTD能增大时间步长,缩短计算时间的优点,同时与ADI-FDTD相比节约了最多达1/3(三维)或2/5(二维)的内存。与基于零散度关系的ADI/R-FDTD相比,该算法避免了采用长时间步长计算时的发散现象。应用所提出的ADI/R-FDTD算法计算了二维自由空间波的传播及一维频率选择表面垂直入射的问题,计算结果与ADI-FDTD计算结果完全一致,验证了ADI/R-FDTD的正确性和有效性。     

Effective error control of iterative localization for wireless sensor networks

Localization results are vulnerable to measurement errors, which allow for non-Gaussian or Gaussian measurements. In this paper we firstly propose an approximate estimation method for non-Gaussian range errors by analyzing the relationship between residuals and errors. Using the estimated range errors, we correct the residuals and propose a second localization method to improve the localization results. Then we formulate the error estimation caused by Gaussian measurements and evaluate our algorithm under various network topologies, range errors, location errors and number of anchors. We apply the error estimation method to iterative localization and explain the process of error propagation and accumulation. The error analysis under Gaussian measurements provides a guide to choose the anchors reasonably for controlling the localization errors. The experiments demonstrate the high efficiency of our proposed non-Gaussian error control method and evaluate the localization errors caused by range errors and location errors of anchors.     

Low power PLL with reduced reference spur realized with glitch-free linear PFD and current splitting CP

The integrated circuit industry not only demands finding optimal design solutions over an efficient process, but also requires the address of increased reliability challenges, caused by strong electric fields, to elevate the overall system robustness. This work reconciles such an inconsistency by proposing a transistor-level methodology for current steering DACs to map their specs onto transistor sizes and improve their performance, parametric yield as well as lifetime reliability through the state of the art evolutionary tools and reliability simulator. The tradeoff between performance specs and power consumption is obtained through a multi-objective approach by considering process variations together with lifetime stress effects. The 10-bit DAC@130MS/s is herein implemented using TSMC CMOS 0.18 μm technology. Demonstrated results point out optimal design points in short and long time reliability as well as performance parameters over a computational effective procedure.     

三维柱坐标ADI-FDTD算法及其CPML实现

提出一种三维柱坐标交互隐式方向(ADI)时域有限差分算法(FDTD)及其卷积完全匹配层(CPML)的实现方案。首先,为了简化公式的冗繁和编程的需要,将传统三维柱坐标时域有限差分算法转换成矩阵表达式的形式。其次,以矩阵变换的方式提出三维柱坐标系下ADI-FDTD 算法的矩阵表达式。最后,将匹配层的影响参数以辅助变量的方式添加至该算法中,从而完成本文算法的CPML实现。算例证明本文算法在时域和频域均有较好的效率和精度,并且具有良好的CPML 吸收效果,其反射系数可达-63 ~ -70 dB。     

Comments on "An efficient PML implementation for the ADI-FDTD method"

For original paper see Wang and Teixeira (IEEE Microwave Wireless Comp. Lett., vol.13, p.72-4, 2003 February). In this paper, a more precise way to evaluate the actual performance of the perfectly matched layer (PML) used for the alternating direction implicit finite-difference time-domain (ADI-FDTD) method is presented. It is shown that the intrinsic numerical dispersion error of the ADI-FDTD method must be taken into account when the actual performance of the ADI-PML (as well as the ADI-FDTD method) is evaluated. Most importantly, it is demonstrated that the ADI-PMLs implemented with either the traditional manner or the way proposed in have almost the same level of accuracy when the performance of the ADI-PML is correctly evaluated.     

An iterative approach to MVDR beamforming with multi-cycle optimisation

An iterative approach to GSC beamforming is presented. The algorithm is able to achieve a GSC solution through a number of optimisation cycles, each of which includes several iterative weight vector updates. The algorithm is flexible and a weight vector may contain one or a few beamforming weights, implementing the optimal solution with reduced dimensionality. It is shown through theoretical analysis that the weight vector convergences with the proposed algorithm. The effectiveness of the algorithm is demonstrated through simulation results.     

一种联合星座和伴随式信息的迭代译码算法

针对构造性的大数逻辑可译低密度奇偶校验(LDPC)码,联合信号星座和伴随式信息,提出一种基于可靠度的迭代大数逻辑译码算法。在校验节点,直接使用伴随式信息进行传递和处理;在变量节点,结合信源端的星座映射和伴随式进行译码信息收集和处理。理论分析和仿真实验结果表明,所提出的算法在保持优良译码性能的同时,具有更低的译码复杂度。