Étude de la précision de l’estimation de la densité spectrale de puissance croisée,obtenue par transformation de fourier de la fonction de corrélation

The authors compare two different estimators of the crosscorrelation function and show that they give equivalent estimators in the frequency domain. They calculate the first and second order moments of the estimator of the cross-spectral-density (DSPC)due to the statistical errors and the quantification of inputs. From these general formulas, they perform numerical calculations for a particular case and they compare them to practical measurements. They show the interesting fact, that the variance of the statistical errors on the dspc is inferior by estimating its phase than by estimating its module. Furthermore, the quantification of the inputs may influence the variance of the phase of the DSPC estimated.     

Vulnérabilité aux erreurs de transmission de signaux sonores de haute qualité et méthodes de protection

The present paper deals with protection methods of high quality digital sound signals in presence of transmission errors. They are strongly related to the coding and the bit rate reduction methods used in the digital treatment of sound signals. Therefore, the first part is assigned to these aspects. Part 2 describes a procedure for a subjective evaluation of the impairments caused on digital sound signals by transmission errors. This procedure was used during tests realised in the ccett.Part 3 summarizes the main results of these tests and proposes a strategy for the protection which ensures a satisfying compromise between quality and simplicity.     

Investigation de la gestion de qualité de service dans le réseau UMTS

Bit rate announced for the future standards of telecommunication, as well as the level of integration reached are, as many factors, determining for the establishment of new applications in mobile terminals. Nowadays, mobile video streaming services are possible. Mobile users expect to receive multimedia traffic with some performance guarantees, so we must ensure the necessary quality of service during the video transmission. This paper aims at investigating quality of service issue inUmts network. More specifically, we explore the main challenge of quality of service management to dynamically optimize the distribution of load inUmts networks. Our investigation is organized in the following way. We formalize the optimization problem which is based on the graph theory and modellingUmts network as well as mobile users and applications to be used. The simulation of our optimization model show a clear improvement of the quality of service perceived by anUmts user in terms of bit rate, blocking and connection drop.     

智能手机de前世今生

Symbian、Windows Mobile、Palm OS、Linux，在手机业界，这4个响当当的名字，几乎主宰了智能手机的一切。智能手机从萌芽到现在的日益成熟，操作系统之间的争斗就从来没有停止过，这也在很大程度上促使智能手机技术的飞速发展。虽然智能手机发展还只经历了短短的数年时间，但无论它们来自何方，要去向何处，留给我们的都是一部值得回味的纷争的历史。     

关于de Bruijn序列

本文对二元域上M序列的小项集合进行研究,给出了M序列的一些新的必要条件;对非奇布尔函数给出一种(基于小项集合的)编号表示,指出了M序列编号的若干特点;给出了本原M序列小项集合及剪接标号集合的一些性质;并对奇数阶自对偶反转M序列的小项构造和计数作了初步探讨,提出了一些分析和猜想。     

ESWC新地图 de tuscan

在ESWC2008组委会公布的CS比赛规则中，大家可以注意到本次ESWC的CS比赛地图取消了我们熟悉的de_cbble，取而代之的是陌生的de_tuscan。de_cbble的平衡性一直是令人头疼的大问题，因为做T的一方很难组织起有效的进攻。但de_tuscan又如何呢？     

博大精深de北图站点

北京图书馆网络服务起步于已1995年,当时使用微波无线与电报大楼和清华大学联接。1997年在北京电信管理局的支持下,北图实现Chinanetl.544M数据带宽的光缆连通,1998年4月北京电信调拨128个IP地址用于拓展北图的网络服务建设。根据中国互联网络信息中心的安排,北图于1998年4月26日