Further Studies of Soft Decision Error Detectors for the Gaussian Channel

This correspondence is an extension of the work in [1] and [2]. We present two new classes of error detectors which utilize symbol reliability information (i.e., soft decision error detectors). First, a simple class of selectively single error correcting error detectors is discussed where the syndrome information is used and where just one single reliability number is compared to a threshold value. These error detectors are simpler than those in [1] and [2], but less powerful. Second, a class of soft decision error detectors with low probability of undetected errors is considered. The reliability information is used to reduce the probability of undetected errors without increasing the repeat request probability (compared to the hard decision error detector). Exponential properties for large signal-to-noise ratios and bounds are calculated for both classes of error detectors. Computer simulations are also presented.     

Effect of Mismatch on the Reliability of ON/OFF-Programmable CNNs

In this paper, the reliability of computation of ON/OFF-programmable cellular nonlinear networks (CNNs) is analyzed. This paper redefines the classical concept of robustness (tolerance to physical imperfections) in ON/OFF-programmable CNNs so that it can be used to predict the computation reliability of a physical realization. Also, a systematic approach to improve robustness is described, and guidelines for optimizing reliability with the given resources are given. Random mismatch is identified as the main source of errors in a physical realization. At the presence of random mismatch, we describe the probability of a cell producing an error with specific inputs and the error probability when processing random data. In addition, we show how the error probability could be defined in case the cell needs to work correctly with all possible input combinations.     

Human errors: A review

This paper briefly reviews human errors in engineering systems. Definitions for human reliability and human errors are presented. Consequences and causes of human errors are discussed. Historical developments in human reliability are briefly described. Breakdowns of human errors are given. Human error prevention and reduction methods are discussed along with human reliability data banks. In particular, Data Store and Operational Recording and Data System (OPREDS) are described. Human errors in structures and computer systems are discussed. Error rates for selected tasks are presented.     

A Class of Soft Decision Error Detectors for the Gaussian Channel

The main idea of this concise paper is to use symbol reliability information for improving the performance of error detectors. A class of soft decision error detectors (SDED's) is presented, where low weight error patterns are selectively corrected. The reliability numbers govern which error pattern to correct. Asymptotic performance and bounds are derived for the Gaussian channel. It is shown that singleerror correcting SDED's without thresholds have an exponentially lower repeat request probability than the hard decision error detector, but the same exponent in the probability of undetected errors. Detectors with thresholds are also considered. In this case it is possible to contruct an error detector with both better probability of undetected errors and better probability of repeat request than for the hard decision error detector (HDED). Bounds and computer simulations are presented and SDED's are compared to HDED's.     

The Maximum Error in System Reliability Calculations by Using a Subset of the Minimal States

The reliability of a system is evaluated from information about the minimal states, using Poincare's method (inclusion-exclusion). An equation is derived using the minimal paths, which gives the reliability (the probability of system success) as a function of the reliabilities of the components; the unreliability or probability of system failure is obtained by subtracting this from one. Dually, with the minimal cuts, an equation is derived which gives the system unreliability as a function of the unreliabilities of the components; the reliability is obtained by subtracting from one. If some of the minimal states are missing, unknown, or unused, an error is made in the calculation. The probability which is calculated from the minimal states is underestimated and its complement overestimated. In this paper a method is described for determining the maximum error, both absolute and relative, when: 1) the minimal states are all statistically independent (e.g., they have no states in common); and 2) every minimal state has the same probability p, where p is selected so as to maximize the error. It is shown that the error and its associated system probability depend only upon the ratio of the number of minimal states used to the total number of minimal states. A table of errors, system probabilities, and relative errors is given for values of this ratio 0.01 (0.01) 0.99.     

Octet error probability analysis of ADSL–DMT codewords

This paper presents an analytical investigation of the octet error probability of ADSL codewords under the impact of white Gaussian noise. It is shown that the assumption of independent bit errors which can be found in the literature is invalid in this case. Instead, as a novel method, bitgroups from DMT subcarriers contributing to a particular octet are analyzed. Typical bitgroup types are discussed with regard to their error probability. Finally, proposals for applying these results in optimized system solutions are derived.     

Use of Error Correcting Codes on Memory Words for Improved Reliability

Application of error correcting coding is often employed to improve system operation and reliability. By means of suitable reliability models and simple analysis, the effect of error correcting coding of memory words on the overall reliability of the system is discussed. Introduction of error correcting facilities will generally have three significant effects on the system: 1) increased hardware, which is also subject to failures and hence tends to lower reliability; 2) the system's ability to function in the presence of a certain class of failures; and 3) quicker detection of errors, which also means an improved repair rate. To illustrate the extent to which the above three factors govern the reliability improvement due to coding, three types of systems are considered. These systems use the same basic processor and memory units but differ in their structure and complexity. Other factors besides the three above which control the reliability improvement due to coding are the system structure and the relative sizes of processor and memory hardware.     

Stochastic behaviour of man-machine systems operating under different weather conditions

This paper presents some comments on ‘Stochastic behaviour of man-machine systems operating under different weather condition’ [1]. In addition, reliability analysis of one of the models given in [2] is performed. State probability, human operator reliability, mean time to human error (MTTHE) and probability of human error plots are shown.     

利用无损压缩降低循环冗余校验的错误漏检率及其电路实现

循环冗余校验(CRC)算法在很多领域都有广泛的应用。对于确定格式的CRC校验码生成多项式,其错误漏检率基本为确定值。因此待检数据的长度越大,出现错误而不会被检测到的机会也就越多。为了解决这方面存在的问题,该文利用无损压缩霍夫曼算法缩短待测数据的长度,从而降低了数据出错之后不能被检测到的概率。并设计出相应的可靠性校验电路。与单纯使用CRC校验的方法相比,该文提出的方法可以将出错的几率下降为原来的万分之一以下。设计得到的电路模块可以作为VLSI中的可靠性电路模块(IP)加以利用。     

A statistical analysis of phase aberration correction using image quality factors in coherent imaging systems

A fundamental analysis of phase aberration correction techniques which use speckle brightness-based image equality factors (QFs) to iteratively reduce phase errors is presented. Phase aberration arises from the spatial inhomogeneity of acoustic velocity in human tissue and degrades the performance of diagnostic ultrasonic imaging systems. A theoretical analysis is presented indicating that the mean speckle brightness decreases with root-mean-square (RMS) phase error. A general definition of QFs is given using the probability of error as a criterion of performance. The QF is optimized through minimization of the probability of error under different conditions. The analysis provides a theoretical framework for the current correction technique using QFs under a variety of conditions, and is a useful tool to evaluate new QFs and correction techniques.     

Cognitive Reliability in Manned Systems

Human components in manned systems often compensate for hardware error by utilizing other information and past experience in addition to the normal hardware output. However, errors in human information processing and utilization, cognitive reliability, often lowers the overall system reliability. Cognitive reliability in manned systems is discussed in terms of the types of human errors which may occur and in terms of factors which affect the occurrence of these errors. It is a complex function of attitudinal and structural factors and their interaction. Cognitive reliability is useful for examining man's role in complex systems where cognitive as well as perceptual-motor skills are required.     

High-SNR Analysis of Outage-Limited Communications With Bursty and Delay-Limited Information

This work analyzes the high-SNR asymptotic error performance of outage-limited communications with fading, where the number of bits that arrive at the transmitter during any timeslot is random but the delivery of bits at the receiver must adhere to a strict delay limitation. Specifically, bit errors are caused by erroneous decoding at the receiver or violation of the strict delay constraint. Under certain scaling of the statistics of the bit-arrival process with SNR, this paper shows that the optimal decay behavior of the asymptotic total probability of bit error depends on how fast the burstiness of the source scales down with SNR. If the source burstiness scales down too slowly, the total probability of error is asymptotically dominated by delay-violation events. On the other hand, if the source burstiness scales down too quickly, the total probability of error is asymptotically dominated by channel-error events. However, at the proper scaling, where the burstiness scales linearly with ${{ 1}over { sqrt {log {rm SNR} }}}$ and at the optimal coding duration and transmission rate, the occurrences of channel errors and delay-violation errors are asymptotically balanced. In this latter case, the optimal exponent of the total probability of error reveals a tradeoff that addresses the question of how much of the allowable time and rate should be used for gaining reliability over the channel and how much for accommodating the burstiness with delay constraints.      

Software reliability estimation: A realization of competing risk

A software reliability model presented here assumes a time-dependent failure rate and that debugging can remove as well as add faults with a nonzero probability. Based on these assumptions, the expected number of faults and mean standard error of the estimated faults remaining in the system are derived. The model treats the capability of correcting errors as a random process under which most of the existing software reliability models become special cases of this proposed one. It, therefore, serves to realize a competing risk problem and to unify much of the current software reliability theory. The model deals with the nonindependence of error correction and should be extremely valuable for a large-scale software project.     

Evaluating Transient Error Effects in Digital Nanometer Circuits

Radiation-induced transient errors have become a great threat to the reliability of nanometer circuits. The need for cost-effective robust circuit design mandates the development of efficient reliability metrics. We present a novel ldquonoise impact analysisrdquo methodology to evaluate the transient error effects in static CMOS digital circuits. With both the circuit, and the transient noise abstracted in the format of matrices, the circuit-noise interaction is modeled by a series of matrix transformations. During the transformation, factors that potentially affect the propagation & capture of transient errors are modeled as matrix operations. Finally, a ldquonoise capture ratiordquo is computed as the probability of a sequential element capturing transient noise inside the combinational logics, It is used as a measure of the transient noise effects in the circuit. Comparison with SPICE simulation demonstrates that our technique can accurately, yet quickly estimate the probability of transient errors causing observable error effects. The proposed methodology will greatly facilitate the economic design of robust nanometer circuits.     

Reliability/energy trade-off in Bluetooth error control schemes

Two important objectives in wireless sensor networks are reliability and reducing energy consumption. Hence, overcoming energy constraints and utilizing error control schemes such as Automatic Repeat Request (ARQ) and Forward Error Correction (FEC) are necessary to improve the energy efficiency and reliability. However, these two concerns are at odds, so there is a trade-off between them. Considering this point, the impact of various error control schemes on these objectives and the trade-off between them has been considered in Bluetooth networks recently. However, all these works consider ideal assumptions (e.g., perfect error detection) only. This work evaluates the energy-efficiency of Bluetooth error control schemes in Rayleigh fading channels taking into consideration both ideal assumptions and residual error probability of the CRC code in ARQ schemes. A comparative analysis of coding techniques using different BCH codes on the AUX1 packet is provided. In addition, the impact of variations in number of hops and SNR on the effectiveness of proposed coding techniques is analyzed through simulation. This analysis provides information that help network designers to choose suitable packet types and coding techniques for Bluetooth networks depending on the network situation.     

A stochastic model of fault introduction and removal duringsoftware development

Two broad categories of human error occur during software development: (1) development errors made during requirements analysis, design, and coding activities; (2) debugging errors made during attempts to remove faults identified during software inspections and dynamic testing. This paper describes a stochastic model that relates the software failure intensity function to development and debugging error occurrence throughout all software life-cycle phases. Software failure intensity is related to development and debugging errors because data on development and debugging errors are available early in the software life-cycle and can be used to create early predictions of software reliability. Software reliability then becomes a variable which can be controlled up front, viz, as early as possible in the software development life-cycle. The model parameters were derived based on data reported in the open literature. A procedure to account for the impact of influencing factors (e.g., experience, schedule pressure) on the parameters of this stochastic model is suggested. This procedure is based on the success likelihood methodology (SLIM). The stochastic model is then used to study the introduction and removal of faults and to calculate the consequent failure intensity value of a small-software developed using a waterfall software development     

基于一种交织码的多位翻转容错技术研究

随着技术的发展和核心电压的降低,存储器更易受瞬时错误（软错误）影响,成为影响航天器件可靠性的主要原因。错误检测与纠正（EDAC）码（也称错误纠正码）常用来对SRAM型存储器中的瞬时错误进行纠正,由单个高能粒子引起的多位翻转错误（SEMU）是普通纠一检二（SEC-DED）编码所无法处理的。提出了一种交织度为2的(26,16)交织码,该码由两个能纠正一位随机错误、二位突发错误的(13,8)系统码组成,(26,16)交织码能够纠正单个码字中小于二位的随机错误和小于四位突发错误（DEC-QAEC）。通过理论分析和硬件平台实验表明,该交织码在存储资源占用率、实时性相当情况下可靠性优于同等长度的SEC DED码,能有效提高SRAM型存储器抗多位翻转错误的能力。      

Link Error Analysis and Modeling for Video Streaming Cross‐Layer Design in Mobile Communication Networks

Particularly in wireless communications, link errors severely affect the quality of the services due to the high error probability and the specific error characteristics (burst errors) in the radio access part of the network. In this work, we show that thorough analysis and appropriate modeling of radio‐link error behavior are essential to evaluate and optimize higher layer protocols and services. They are also the basis for finding network‐aware cross‐layer processing algorithms which are capable of exploiting the specific properties of the link error statistics, such as predictability. This document presents the analysis of the radio link errors based on measurements in live Universal Mobile Telecommunication System (UMTS) radio access networks as well as new link error models originating from that analysis. It is shown that the knowledge of the specific link error characteristics leads to significant improvements in the quality of streamed video by applying the proposed novel network‐ and content‐aware cross‐layer scheduling algorithms. Although based on live UMTS network experience, many of the conclusions in this work are of general validity and are not limited to UMTS only.     

A reliability output Viterbi algorithm with applications to hybridARQ

We present an algorithm that permits a receiver to calculate the probability of packet error in parallel with the Viterbi decoding process. This packet reliability value may be used to request retransmissions in a type-I hybrid ARQ scheme. It is shown that this scheme can be used to guarantee any required bound on the packet error probability. In addition, this scheme can be used in conjunction with packet combining. The performance of this scheme is compared with that of the Yamamoto-Itoh algorithm and is shown to provide a significant improvement in throughput     

Analysis of equal-gain diversity with partially coherent fadingsignals

An analytical technique based on Gram-Charlier series expansion is presented for the computation of the error probability of equal-gain combiner (EGC) with partially coherent fading signals. Imperfect carrier recovery is attributed to the random noise present in the carrier recovery loops. The resulting noisy phase references are assumed to satisfy Tikhonov distribution. The fades on the diversity branches are assumed to be slowly varying and statistically independent with Rayleigh-distributed envelopes. The error-rate performance of coherent and differentially coherent phase-shift keying (PSK) systems are compared and the phase precision requirement for a reliable coherent detection is computed. Detection loss caused by carrier phase errors is computed for several signal-to-noise ratio (SNR) reliability and bit error probability levels. It is demonstrated that the effect of carrier phase errors on the mean SNR is negligible compared to their effect on deep fades or small bit error probabilities. It is also shown that the carrier phase precision requirement can be reduced through signal combination