基于复杂多通道带乘性噪声模型的水声通信字符估计算法

水声信道具有复杂随机时变特性并存在严重的多径时延、能量损失和畸变等因素,使得水声信道的建模和估计一直是学界的难点问题。本文基于复杂多通道带乘性噪声模型来刻画随机时变的水声信道,在信道建模基础上利用最优滤波递推算法实现发送字符的估计。该算法在线性最小方差意义下是最优的,能有效克服码间干扰和噪声污染。所建立的信道模型能够刻画复杂快变的水声信道,对应的最优信道估计算法具有计算量小的优点,能够动态跟踪信道增益的随机变化。仿真结果验证了本文算法的有效性。     

绕月探测工程地面接收站通用解调处理机性能测试

介绍了绕月探测工程数据接收地面站使用的通用解调处理机的基本组成和工作原理;讨论了针对误码率、极化合成、帧同步和滑步容错等指标要求的测试原理和方法,并对其测试结果进行了分析。为卫星通信的基带设备的测试提供了参考。     

Classification through consultation: public views of the geography of the e-Society

Although viewed by business and commerce as successful solutions, geodemographic profiling of neighbourhoods has attracted wide-ranging criticism in the academic literature. This paper addresses some specific concerns that arise because the derivation of classifications is rarely transparent and open to scrutiny or challenge. The substantive focus of the research reported in this paper is a nationwide geodemographic classification of how people engage with new information and communication technologies (ICTs). In response to the critique of geodemographics as a ‘black box’ technology, we describe how the classification was opened up to public scrutiny and how we conducted a major consultation exercise into the reliability of its results. We assess the message of the 50,000+ searches and 3952 responses collected during the consultation exercise, in terms of possible systematic errors in the shape and detail of the classification. Unusually for Internet-based surveys, we also investigate the likely reliability of the response information received and identify ways in which the outcome of consultation might be used to improve the classification. We believe that this is the first-ever large-scale consultation survey of the validity and remit of a geodemographic classification and that it may have wider implications for the creation of geodemographic classifications.     

Telegraph Messenger Boys: Crossing the Borders between History of Technology and Human Geography

Abstract

Historians of telegraphy have traditionally focused on the system-builders who invented wire communications technologies and incorporated them into profit-making enterprises. Geographers of communications have traditionally traced the changes that the telegraph network wrought on the rank-size of cities and the speed of business. Both have ignored the history of the telegraph messenger boys and the “lived geography” of the telegraph network. This article summarizes a study of telegraph messengers as both active components of technological systems and laboring agents within produced urban spaces, bringing together the fields of both history of technology and human geography.

     

Recent studies of meteors in South Africa

Recent meteor research in South Africa, arising largely from the development of forward and back scatter observing systems, is briefly reviewed. The main areas of investigation have been the use of single station radars to deduce meteor radiant structures, the study of upper atmospheric wind patterns, and research into the factors which influence the performance of meteor burst communication systems.     

面向移动通信网络建设的数字地图应用研究

网络建设与维护管理是移动通信行业日常业务工作的重要内容,由于移动通信电波传播对地理环境存在极强的依赖性,因此利用高精度的专题数字地图进行网络规划和优化成为移动通信网络建设管理的必然趋势。本文综合近年来面向移动通信网络建设数字地图的生产应用实践,结合当前技术发展导向分析,旨在探索面向移动通信网络建设数字地图生产与集成的有效途径。首先分析了移动通信网络建设的主要内容,继而总结归纳了面向移动通信网络建设的数字地图的数据组成,然后针对面向移动通信网络建设数字地图的需求特点及精度要求,给出了面向移动通信网络建设数字地图的生产工艺流程、质量控制流程及数据集成方法,最后介绍了面向移动通信网络建设数字地图的应用实例及效果分析。     

卫星干扰源定位系统星历校正研究

详细介绍了卫星干扰源定位系统中星历校正的测量原理。干扰源定位系统就是对非合作目标进行定位和定轨,测量体制较为特殊。国外相关系统定位精度在几十至百公里量级,星历校正精度在几公里至几十公里量级。针对目前干扰源定位系统精度较差的问题,给出了采用精密定轨方法对两颗同步卫星进行星历校正。通过仿真数据进行处理,最终定轨精度达到十米量级。该方法的研究及工程化使得我国自行研制的卫星干扰源定位系统具有自主测定轨能力。     

Turbo码在水下无线通信中的应用

详细阐述了Turbo码的原理，围绕Turbo码技术具体实现了一个水声通信系统，并用VC对系统进行仿真。仿真的结果及水池中获得的试验数据表明，该方案可使水下无线通信系统的性能得到显著改善。     

Assessment of project THRUST: Past,present, future

Project THRUST (Tsunami Hazards Reduction Utilizing Systems Technology) was a demonstration of satellite technology, used with existing tsunami warning methods, to create a low cost, reliable, local tsunami warning system. The major objectives were successfully realized at the end of the demonstration phase in September 1987. In June 1988, the Chilean Government held a workshop to assess the value of THRUST to national interests. Two recommendations came forth from the workshop: (1) the technology was sufficiently reliable and cost-effective to begin the development of an operational prototype and (2) the prototype would be used as the Chilean Tsunami Warning System. As of August 1989, the equipment was in operational use. In September 1989, major improvements were made in the satellite operations that reduced the response time from 88 to 17 sec and enlarged the broadcast area by 50%. The implications of the recent improvements in satellite technology are discussed for application to reductions in disaster impacts.     

海洋地理信息产品远程保障模式研究

探讨如何改变传统的保障方式,建立新的海洋地理信息产品的远程保障模式。从有线网络技术、无线3G技术和卫星通信技术三个方面论述了新的远程保障模式运行框架,提出了建立新的保障模式技术路线。远程传输测试表明,三种形式的远程保障可行、高效、实用,可以进一步研制开发相应的软硬件实体平台。