Efficient multicast search under delay and bandwidth constraints

The issue of a multicast search for a group of users is discussed in this study. Given the condition that the search is over only after all the users in the group are found, this problem is called the Conference Call Search (CCS) problem. The goal is to design efficient CCS strategies under delay and bandwidth constraints. While the problem of tracking a single user has been addressed by many studies, to the best of our knowledge, this study is one of the first attempts to reduce the search cost for multiple users. Moreover, as oppose to the single user tracking, for which one can always reduce the expected search delay by increasing the expected search cost, for a multicast search the dependency between the delay and the search cost is more complicated, as demonstrated in this study. We identify the key factors affecting the search efficiency, and the dependency between them and the search delay. Our analysis shows that under tight bandwidth constraints, the CCS problem is NP-hard. We therefore propose a search method that is not optimal, but has a low computational complexity. In addition, the proposed strategy yields a low search delay as well as a low search cost. The performance of the proposed search strategy is superior to the implementation of an optimal single user search on a group of users. Amotz Bar-Noy received the B.Sc. degree in 1981 in Mathematics and Computer Science and the Ph.D. degree in 1987 in Computer Science, both from the Hebrew University, Israel. From October 1987 to September 1989 he was a post-doc fellow in Stanford University, California. From October 1989 to August 1996 he was a Research Staff Member with IBM T. J. Watson Research Center, New York. From February 1995 to September 2001 he was an associate Professor with the Electrical Engineering-Systems department of Tel Aviv University, Israel. From September 1999 to December 2001 he was with AT research labs in New Jersey. Since February 2002 he is a Professor with the Computer and Information Science Department of Brooklyn College - CUNY, Brooklyn New York. Zohar Naor received the Ph.D. degree in Computer Science from Tel Aviv University, Tel Aviv, Israel, in 2000. Since 2003 he is with the University of Haifa, Israel. His areas of interests include wireless networks, resource management of computer networks, mobility, search strategies, and multiple access protocols.     

宽带无线移动通信网络优化及相关发展策略思考

在介绍宽带无线移动发展趋势所采用的新技术的基础上，论述了宽带无线移动通信网络优化及相关发展策略的一些问题。     

IPv6与欧洲

在推进IPv6的问题上,亚洲表现的最为积极,这是因为亚洲各国承受着巨大的IP地址方面的压力。欧洲虽然在这方面没有这样大的压力,但在互联网方面一直落后于美国,这是欧洲所不甘心的。因此,欧洲在推进IPv6方面也做了许多工作。欧洲推进IPv6的基本策略是先移动,后固定,并实施了一系列的行动计划和项目。欧洲面临的挑战主要是已经部署了数量巨大的网元、操作系统与软件应用必须予以更新、互通或取代,需要仔细规划和大量投资。     

移动IP综述

论述了移动IP的概念和发展过程，分析了国内外对移动IP研究的重点问题及其方法，对移动IP的发展方向进行了归纳和总结，并提出了有关用的问题。     

广州地铁二号线民用移动通信工程简介

简单介绍了广州地铁二号线民用移动通信工程概况，并就地铁民用移动通信系统引入地铁的主要技术难点进行了论述。     

关于海面无线传播模型的探讨

现有文献中一般都认为海面环境的无线传播模型近似于自由空间传播模型，但在实际测试中发现，自由空间模型预测值与实测值差别较大，不能很好地解释此类环境的信号传播。笔者根据多次海面覆盖测试的数据，分析并拟合出了新的海面传播模型。     

宏蜂窝模型的传播模型校正研究

详细介绍了 宏蜂窝传播模 型校正的基本操作流程 结果分析及注意事项 对工程 ,人员了解和开展模型校正工作有一定的指导作用 。     

不断进取的AXE10

有近２０年历史的爱立信ＡＸＥ１０交换机在信息时代到来之际再放异彩，目前，它作为公共平台广泛应用于ＰＳＴＮ、ＩＳＤＮ、ＩＮ，ＰＬＭＮ、信令网和商务通信等。     

Planning considerations for domestic replacement satellites

Several domestic satellite systems have been more than 10 years in operation. During this time, the world has experienced a dramatic growth in communication. While the demand for more telephony and data circuits and television channels is still on the rise, new methods of signal transmission and circuit compression have been developed which may balance or reduce the need for more satellite trunk capacity. And while whole national networks are converting to digital transmission, new transmission media like optical fibre, are finding application, and may take over some of the heavy traffic routes previously carried by satellite. On the other side, business data communication between roof-top terminals, thin route traffic to remote users, television distribution by direct satellite broadcasting are becoming more popular and satellite land mobile communication may soon be a reality. Thus the domestic satellite's role appears to be slowly changing towards thin route and mobile traffic and DBS-type distribution and perhaps even radio position determination. System planners are adapting to the new trends in satellite communication and are trying to accommodate the various service payloads on a single satellite. This article discusses some aspects of the emerging multi-purpose domestic satellite, which carries fixed and mobile services, TV direct broadcasting and radio position determination, in view of network digitalization, network expansion, circuit compression, synchronization. The discussion centres on transponder supply and demand, satellite replenishment, K_u-band vs. C-band for TV direct satellite broadcasting, choice of modulation/multiple access for mobile communication, and expected accuracy in radio position determination.     

手机市场呼唤召回制度

我国移动电话用户数已跃居世界第一位,且依然蕴藏着巨大的商机。由此不但引发了日趋激烈的市场竞争,而且造成了产品质量投诉量的居高不下,其中对于存在先天设计缺陷产品的处理目前在我国尚无法可依。国际上对缺陷产品实行的召回制度同样适用于我国。这是市场经济规则的需要,也是商家诚信作风的体现。我国已融入世界经济大潮之中,目前建立手机召回制度是必要和适时的。对生产企业而言,一旦发现缺陷产品流入市场,即刻确认并将其召回是明智之举。