Error statistics in data transmission over fading channels

We investigate the behavior of block errors which arise in data transmission on fading channels. Our approach takes into account the details of the specific coding/modulation scheme and tracks the fading process symbol by symbol. It is shown that a Markov approximation for the block error process (possibly degenerating into an identically distributed (i.i.d.) process for sufficiently fast fading) is a good model for a broad range of parameters. Also, it is observed that the relationship between the marginal error rate and the transition probability is largely insensitive to parameters such as block length, degree of forward error correction and modulation format, and depends essentially on an appropriately normalized version of the Doppler frequency. This relationship can therefore be computed in the simple case of a threshold model and then used more generally as an accurate approximation. This observation leads to a unified approach for the channel modeling, and to a simplified performance analysis of upper layer protocols     

Frequency and attenuation dependent fade slope statistics

Results obtained from slant path propagation experiments carried out with the OLYMPUS satellite are reported. Concurrent attenuation measurements at 12.5, 20 and 30 GHz have been analyzed with regard to the rate of change of rain attenuation (fade slope). The results indicate that pronounced fade slopes occur mostly in the high attenuation range.<>     

Fade slope statistics for three 12-GHz satellite beacon links inBrazil

The fade slope is defined as the rate of increase or decrease of attenuation over time. The possible correlation between the statistics of fade slope values and attenuation levels is investigated. Results show a direct positive correlation between the mean values of fade slope and the attenuation levels. The distributions of fade slope values present a degree of skewness toward the negative values that makes the curves depart from the Gaussian distribution observed by other authors     

Error statistics for average power measurements in wireless communication systems

The measurement of the average received power is essential for power control and dynamic channel allocation in wireless communication systems. However, due to the effects of multipath fading and additive noise inherent to the wireless channel, there can be significant errors in such measurements. In this paper, the error statistics for average power measurements are considered; in particular, the probability distribution of the value of the average received power at the time of interest conditioned on an outdated measurement is obtained. The resulting expression should have high utility in the analysis of wireless communication systems. However, in this paper, the design of power control algorithms that minimize the average transmitted power required to achieve a desired outage probability for the link is considered. A number of novel power control algorithms based on various models for the error in the average power measurement are derived. Numerical results indicate that power control algorithms based on the accurate expression derived in this paper can demonstrate significant gains over those based on previous approximate models.     

长途呼叫2822局通知音回送有误问题的处理

详细介绍了S1240交换机当服务项目通知音回送有误时,对交换机中数据检查的步骤和对问题的处理方法,为维护人员处理此类问题提供了参考。     

Error detection and correction options for data services in B-ISDN

The authors investigate error detection and correction options for data services in the broadband integrated services digital network (B-ISDN). They discuss and analyze different options for error detection and correction by considering the various alternatives ranging from no error protection to only error detection. Based on the analysis and results presented, a per-cell cyclic redundancy check (CRC) has been adopted in the adaptation layer for all data services. The authors focus on the ATM (asynchronous transfer mode) adaptation layer (AAL) error protection alternatives available within the framework of a per-cell CRC. The ATM cell header and AAL fields are described. A 4 bit cell sequence number for detecting cell misordering is analyzed. Based on the analysis, it is concluded that the 4 bit sequence number provides a powerful capability for detection of cell misordering     

精确数据分析与统计规律研究的计算机实现

精确数据分析与统计规律研究是科学研究的重要环节.结合具体实例,详细介绍了在重力加速度测定和分析过程中,利用Origin和Matlab等计算机软件实现数据精确分析的过程,并详细阐述了运用Matlab语言编写应用程序,从而完成偶然误差统计规律研究的过程.     

Error statistics and construction of error correcting codes for differentially encoded CPSK channels (Corresp.)

A simple Markov chain model for differentially encoded CPSK Channels faciliates the calculation of the probability of the occurrence of several most probable error patterns in a given codeword. Several error correcting codes which can efficiently correct several most-probable error patterns are proposed and their error performances are analyzed.     

基于文本数据的统计与分析系统

随着信息社会的迅速发展,大量的数据不断涌现,特别是一些社交网络产生的文本数据,比如短信、彩信、即使通信等,给数据的统计和分析带来了新的挑战,而面向通用数据类型设计的数据库分析系统已很难达到快速分析、实时响应的要求。文章采用无共享架构的seal系统,具有良好的实时分析响应能力,通过增加细粒度索引,提高数据库的访问性能。     

Comparison of backscattered signal statistics as derived fromindoor scatterometric and SAR experiments

A comparison between indoor scatterometric and SAR measurements of distributed targets is presented. In particular, the backscattered signal statistics (in amplitude and phase) obtained in these two types of measurements are compared for different surface parameters (roughness and correlation length) and varying spatial resolutions in the SAR images. Experimental data have been taken in the European Microwave Signature Laboratory (EMSL) at JRC, an indoor facility which is able to measure extended targets both in scatterometric and linear SAR mode under the same conditions. The results confirm that, with spatial resolutions in the SAR image smaller than two autocorrelation lengths (ACL), the statistics of the backscattered signal depends significantly on the resolution cell size. For larger resolution cells, the experimental data are consistent with the Rayleigh model. This experimental finding substantially confirms the results based on numerical simulations, previously presented in the literature     

大数据在司法统计工作中的应用

随着移动互联网、智能终端的发展,我们已经步入了大数据时代.大数据在司法统计中的应用.由于司法统计与现代信息技术的深度融合,运用大数据技术作为支撑,提升办案能力,是司法检察工作因应犯罪信息化、智能化新情况的必然举措.当前,司法检察工作面临数据源缺乏、大数据运用水平低、数据分析人才匮乏、传统审查思维僵化等问题,应进一步打通数据调取通道,推动设立数据共享平台,理顺技术协作机制,解决大数据运用的基础问题.同时,应培养专门的法律大数据分析人才,提升检察技术和信息化队伍的专业素质.     

无线电监测数据统计分析探讨

0前言 　　日常无线电监测是无线电管理中的一项重要工作,开展日常无线电监测,收集和处理监测数据,是描述和评价无线电环境状况,进行无线电管理的基础依据.     

Improved class statistics estimation for sparse data problems in offline signature verification

Sparse data problems are prominent in applications of offline signature verification. By using a small number of training samples, the class statistics estimation errors may be significant, resulting in worsened verification performance. In this paper, we propose two methods to improve the statistics estimation. The first approach employs an elastic distortion model to artificially generate additional training samples for pairs of genuine signatures. These additional samples, together with original genuine samples, are used to compute statistic parameters for a Mahalanobis distance threshold classifier. The other approach is to adopt regularization techniques to overcome the problem of inverting an ill-conditioned sample covariance matrix due to insufficient training samples. A ridge-like estimator is modeled to add some constant values for diagonal elements of the sample covariance matrix. Experimental results showed that both methods were able to improve verification accuracy when they were incorporated with a set of peripheral features. Effectiveness of the methods was validated by quantity analysis.     

Comments on uniqueness of statistics derived from moments of random variables

Electrical engineers and physicists are often confronted with the problem of finding a probability density of a random variable (e.g., a noisy signal) from its moments. Some sources of apparent confusion in deciding whether the distribution is uniquely determined are discussed.     

Effect of wet antenna attenuation on propagation data statistics

Wet antenna attenuation during rain events is examined through carrying out simulated rain experiments. These were conducted on the receiving antenna of the Vancouver ACTS terminal under conditions similar to those prevalent when the propagation data on the Vancouver ACTS path were collected. The findings from these experiments are used to estimate path attenuation data for that path by adjusting the collected data for wet antenna attenuation via two different models. Primary and secondary statistics of the path attenuation data derived from the models at the two ACTS frequencies, nominally 20 and 27 GHz, are computed and compared with those for the unadjusted, measured data. This was done for the four-year period of December 1993 to November 1997 and includes average and worst month cumulative distribution functions and fade-duration and fade-slope statistics. While the two models yield similar statistics, these differ significantly from those derived from the unadjusted data. The comparison of the two sets of statistics suggests that the use of those of the unadjusted data to represent path attenuation would grossly exaggerate the requirements for system design     

Estimation of subrefraction statistics using surface synoptic meteorological data

A companion paper developed a subrefractive fading model, in terms of a minimum effectivekvalue, using surface synoptic meteorological data. The concept is extended here to cover the whole subrefractive event, so that using the effectivekparameterk_{e}, analog radio systems can be simply designed. In the case of digital systems, severe subrefraction may cause outages due to thermal noise increase and this effect must be considered in design. For plains paths, where subrefraction risks are greatest, a method of estimating the shape of thek_{e}versus time curve of individual events by using correlations with surface synoptic meteorlogical data is given. By summation of time below each selectedk_{e}value enables statistics ofk_{e}to be produced. Examples of the method are given, and it is shown how regions of subrefraction may be defined.     

On classification with empirically observed statistics anduniversal data compression

Classification with empirically observed statistics is studied for finite alphabet sources. Efficient universal discriminant functions are described and shown to be related to universal data compression. It is demonstrated that if one of the probability measure of the two classes is not known, it is still possible to define a universal discrimination function which performs as the optimal (likelihood ratio) discriminant function (which can be evaluated only if the probability measures of the two classes are available). If both of the probability measures are not available but training vectors from at least one of the two classes are available, it is demonstrated that no discriminant function can perform efficiency of the length of the training vectors does not grow at least linearly with the length of the classified vector. A universal discriminant function is introduced and shown to perform efficiently when the length of the training vectors grows linearly with the length of the classified sequence, in the sense that it yields an error exponent that is arbitrarily close to that of the optimal discriminant function     

Application of synthetic storm data to evaluate simpler techniques for predicting rain attenuation statistics

The concept of employing synthetic storm data to evaluate simpler attenuation prediction techniques based on cumulative distributions of point rain rate is introduced. As examples, several versions of the «path average rain rate technique» and a new method developed by Crane are tested using 10-year rain rate data bases from several Canadian locations. The results indicate that there is no universal relationship for the ratio of the path average to the point rain rate in terms of either rain rate or percentage of time. However, Crane’s new method appears to be an improvement over earlier versions of the path average rain rate technique.