A call admission and rate control scheme for multimedia support over IEEE 802.11 wireless LANs

Quality of service (QoS) support for multimedia services in the IEEE 802.11 wireless LAN is an important issue for such WLANs to become a viable wireless access to the Internet. In this paper, we endeavor to propose a practical scheme to achieve this goal without changing the channel access mechanism. To this end, a novel call admission and rate control (CARC) scheme is proposed. The key idea of this scheme is to regulate the arriving traffic of the WLAN such that the network can work at an optimal point. We first show that the channel busyness ratio is a good indicator of the network status in the sense that it is easy to obtain and can accurately and timely represent channel utilization. Then we propose two algorithms based on the channel busyness ratio. The call admission control algorithm is used to regulate the admission of real-time or streaming traffic and the rate control algorithm to control the transmission rate of best effort traffic. As a result, the real-time or streaming traffic is supported with statistical QoS guarantees and the best effort traffic can fully utilize the residual channel capacity left by the real-time and streaming traffic. In addition, the rate control algorithm itself provides a solution that could be used above the media access mechanism to approach the maximal theoretical channel utilization. A comprehensive simulation study in ns-2 has verified the performance of our proposed CARC scheme, showing that the original 802.11 DCF protocol can statically support strict QoS requirements, such as those required by voice over IP or streaming video, and at the same time, achieve a high channel utilization. Hongqiang Zhai received the B.E. and M.E. degrees in electrical engineering from Tsinghua University, Beijing, China, in July 1999 and January 2002 respectively. He worked as a research intern in Bell Labs Research China from June 2001 to December 2001, and in Microsoft Research Asia from January 2002 to July 2002. Currently he is pursuing the PhD degree in the Department of Electrical and Computer Engineering, University of Florida. He is a student member of IEEE. Xiang Chen received the B.E. and M.E. degrees in electrical engineering from Shanghai Jiao Tong University, Shanghai, China, in 1997 and 2000, respectively, and the Ph.D. degree in electrical and computer engineering from the University of Florida, Gainesville, in 2005. He is currently a Senior Research Engineer at Motorola Labs, Arlington Heights, IL. His research interests include resource management, medium access control, and quality of service (QoS) in wireless networks. He is a Member of Tau Beta Pi and a student member of IEEE. Yuguang Fang received a Ph.D degree in Systems and Control Engineering from Case Western Reserve University in January 1994, and a Ph.D degree in Electrical Engineering from Boston University in May 1997. From June 1997 to July 1998, he was a Visiting Assistant Professor in Department of Electrical Engineering at the University of Texas at Dallas. From July 1998 to May 2000, he was an Assistant Professor in the Department of Electrical and Computer Engineering at New Jersey Institute of Technology. In May 2000, he joined the Department of Electrical and Computer Engineering at University of Florida where he got the early promotion with tenure in August 2003 and has been an Associate Professor since then. He has published over one hundred (100) papers in refereed professional journals and conferences. He received the National Science Foundation Faculty Early Career Award in 2001 and the Office of Naval Research Young Investigator Award in 2002. He is currently serving as an Editor for many journals including IEEE Transactions on Communications, IEEE Transactions on Wireless Communications, IEEE Transactions on Mobile Computing, and ACM Wireless Networks. He is also actively participating in conference organization such as the Program Vice-Chair for IEEE INFOCOM’2005, Program Co-Chair for the Global Internet and Next Generation Networks Symposium in IEEE Globecom’2004 and the Program Vice Chair for 2000 IEEE Wireless Communications and Networking Conference (WCNC’2000).     

EPG在IPTV集成播控领域的应用

IPTV是当前我国三网融合的前沿应用之一,IPTV EPG在IPTV体系中起着重要作用。本文简要分析和介绍了IPTV EPG在IPTV集成播控平台中的作用和意义、IPTV EPG与有线电视EPG的不同之处,以及IPTV EPG与IPTV认证、鉴权、计费等机制的内在联系。结合贵州IPTV集成播控平台的建设介绍了EPG在IPTV集成播控领域的设计、实现和部署,探讨了具有中国特色的IPTV EPG的关键技术和应用。     

全业务运营的重要窗口——融合终端

介绍融合终端的发展现状和发展趋势,分析融合终端上开展的典型业务,并着重阐述发展融合终端的几个关键问题,包括融合终端的商业模式、融合终端技术以及融合业务。     

Intertemporal service pricing with strategic customers

We study a two-period intertemporal pricing game in a single-server service system with forward-looking strategic customers who make their purchase decision based on current information and anticipated future gains. Subgame perfect Nash equilibrium (SPNE) prices are derived. A comparison between revenue-maximizing equilibrium prices and welfare-maximizing equilibrium prices is conducted and the impact on the system’s performance of misunderstanding customers’ type is evaluated.     

Evaluating the performance of Swedish savings banks according to service efficiency

This article develops principles for an evaluation of the efficiency of a savings bank. It starts out from the observation that such a bank is less profit oriented than a commercial bank. The customer is a vital stakeholder to the savings bank implying a greater emphasis on customer service provision. We are using data envelopment analysis (DEA) as a method to consider the service orientation of savings banks. We thereby demonstrate how an evaluation of the performance of savings banks according to “service efficiency” differs from an evaluation based on the traditional “profit” or shareholder concept. We determine the number of Swedish savings banks being “service efficient” as well as the average degree of service efficiency in this industry.     

全业务时代,集团业务建设思考

讨论全业务时代集团业务发展的新要求,分析现行支撑系统的不足,分析构建以集团客户为中心,优化流程,促进协同运作,灵活配置等特点的全业务支撑体系的重要性,给出对新形势下集团业务建设的建议。     

Skilled workforce scheduling in Service Centres

The Skilled Workforce Project Scheduling Problem (SWPSP) is a complex problem of task scheduling and resource assignment that comes up in the daily management of many company Service Centres (SC). The SWPSP considers many real characteristics faced daily by the SC: client-company service quality agreements that establish maximum dates for the beginning and the end of tasks with penalties for delays, criticality levels indicating the client-priority in processing each task, generalized precedence relationships that can produce cycle structures, time period and percentage time lags and variable task durations depending on the worker executing the task. Furthermore, the SC workforce is made up of specialist workers characterised by efficiency levels showing their efficiency and speed executing the several types of tasks. Each worker has his or her own timetable.     

一种支持分级服务和最小带宽保证的改进TCP算法

本文提出了一种支持分级服务和最小带宽保证的改进TCP算法－DSAS－TCP，通过对TCP算中慢启动阈值和最小拥塞窗口的分级设置来使不同等级连接的平均吞吐量产生分级，并保证用户的最小带宽需求。通过理论分析和仿真实验验证了该算法的有效性。     

全球移动蜂窝通信的革命

近年来，移动蜂窝通信的发展速度可谓骇世惊人。１９９０年，移动用户有１１００万，到１９９８年底达到了３亿多个。据预测，在今后１０年中移动蜂窝用户数将超过固定电话。本文研究了全球移动蜂窝通信的发展状况，就技术革命、服务提供、管制、接入、价格以及发展前途等方面进行了详细的论述。     

降低业务平台TCO的解决方案

从介绍业务平台的现状和总体拥有成本（TCO）的组成入手,分析了现网TCO,给出了ZTEiVAS平台解决方案,最后对ZTEiVAS平台与传统业务平台进行了对比。