RMFS：一种支持用户交互的流媒体调度方案

基于组播的流调度算法能够有效降低服务器和网络带宽消耗.但研究表明,在用户进行VCR交互操作情况下,这些算法的性能将急剧恶化.该文提出一种有效支持用户交互的视频点播系统流调度方案:常规组播固定调度RMFS.RMFS采用基于请求类的接纳控制策略,并通过流合并机制来合并单播流.分析了RMFS方案的最佳组播间隔、最佳请求阈值和最小服务器容量需求.仿真结果验证了分析模型的正确性和RMFS方案的可行性.     

Two-level protection and guarantee for multimedia traffic in IEEE 802.11e distributed WLANs

In order to support multimedia applications such as voice and video over the wireless medium, a contention-based channel access function, called Enhanced Distributed Channel Access (EDCA), has been developed in the emerging standard IEEE 802.11e. In the EDCA, differentiated channel access is provided for different traffic classes. In this paper, we propose a two-level protection and guarantee mechanism for voice and video traffic in the EDCA-based distributed wireless LANs. In the first-level protection, the existing voice and video flows are protected from the new and other existing voice and video flows via a distributed admission control with tried-and-known and early-protection enhancements. In the second-level protection, the voice and video flows are protected from the best-effort data traffic by adopting frame-based and limit-based data control mechanisms. Performance evaluations are conducted in terms of throughput, delay, transmission limit, number of collisions, and throughput square relative difference. Extensive simulation results demonstrate that the proposed two-level protection and guarantee mechanism is very effective in terms of the protection and guarantee of existing voice and video flows as well as the utilization of the channel capacity. An early version of this paper was presented at IEEE INFOCOM 2004.     

企业推行可靠性技术方法探讨

目前家电产品同质化竞争非常激烈,各企业在功能、性能、价格方面的差距逐渐减小,核心技术和产品质量成为企业立足的根本。其中,作为时间维度上的质薰特性-可靠性,已成为最影响消费者满意度的重要因素并受到市场广泛关注,有可能成为企业下一个战胜对手的秘密武器,如何提高产品可靠性是许多企业急切想得到的答案。文章结合企业开展可靠性工作的实践活动,从产品质量与可靠性、行业现状与企业网境引入可靠性工程的思考、可靠性工程体系建设、可靠性_T程产品导人等方面分析、阐述,力求探索一条推行可靠性技术的最佳途径,供企业同仁参考。     

建立以市场为导向的品控模式（上）

阐述＂市场导向品控模式＂的理念与实践,说明了＂市场导向品控模式＂是适合厨电发展的卓越的品质管理方法,并提供予面临类似背景与挑战的企业作为参考。     

如何在军工产品研制中体现落实质量文化的内涵

文章从实施质量控制策划、科学规范的设计开发、推行零缺陷的质量管理、严格质量问题归零管理、加强质量信息管理、促进软件工程化等几个方面阐述了如何把质量文化落实到军工产品研制中去,从而确保军工产品的质量与可靠性。     

三维控制图的应用

平均值x及极差R控制图是质量管理中用得最多的一种控制图,但它在日常生产中使用较困难,原因是经常有点跑出控制线外,即失控,而实际上生产线却无异常产生,这是从误报警而犯了第一类错误,这些主要是由平均值x及极差R控制图的局限性引起的。如果用平均值x及移动极差R控制图就完全可以解决以上问题,从而大大降低第一类风险而没有增加第二类风险。     

A Cross-Layer Approach to Enhance QoS for Multimedia Applications Over Satellite

The need for on-demand QoS support for communications over satellite is of primary importance for distributed multimedia applications. This is particularly true for the return link which is often a bottleneck due to the large set of end-users accessing a very limited uplink resource. Facing this need, Demand Assignment Multiple Access (DAMA) is a classical technique that allows satellite operators to offer various types of services, while managing the resources of the satellite system efficiently. Tackling the quality degradation and delay accumulation issues that can result from the use of these techniques, this paper proposes an instantiation of the Application Layer Framing (ALF) approach, using a cross-layer interpreter (xQoS-Interpreter). The information provided by this interpreter is used to manage the resource provided to a terminal by the satellite system in order to improve the quality of multimedia presentations from the end user’s point of view. Several experiments are carried out for different loads on the return link. Their impact on QoS is measured through different application as well as network level metrics.

A novel call admission control scheme in cellular/WLAN integration and performance analysis

In order to achieve the Quality of Service (QoS) provisioning and efficient resource utilization in cellular network and Wireless Local Area Network (WLAN) integration, an Integrated Service-Based Call Admission Control (ISB-CAC) scheme is proposed in this paper. The integrated network is modeled by using multi-dimensional Markov chains. The numerical analysis is presented to evaluate the important performance measures such as the blocking probability of originating calls, the dropping probability, and the average transfer time, etc. The steady-state probabilities of the multi-dimensional Markov chains are obtained by using an iterative approach, and the CAC parameters are optimally designed. The analytical model is validated by the computer simulation. It is shown that compared with the conventional WLAN-First Call Admission Control (WF-CAC) scheme, the proposed ISB-CAC scheme not only provides better QoS for mobile users but also utilizes the bandwidth resources more efficiently.     

抽象性：基于整合传统与现代矛盾的思考

无论是建筑还是文化,传统与现代存在着客观的差异,并处于巨大的矛盾当中。本文在总结现实的基础上,提出抽象性是一种基于现实与传统之间差异的本质思考。它是启发那种既非模仿传统,又非模仿西方的当代建筑创新思维的关键点。