System Throughput Analysis of Rate Adaptive TDMA System Supporting Two Class Services

In this paper, an adaptive transmission scheme is proposed to improve the spectral efficiency of TDMA systems. Services accommodated in such systems are classified as QoS services and BE services. Unlike conventional adaptive TDMA systems where the time slot duration is fixed for each user, our proposed system employs transmission slots with adaptive duration. For QoS services, rate adaptive modulation is adopted to make use of the instantaneous channel conditions of individual user. For BE services, a media access control strategy (MAC) that takes the instantaneous transmission conditions of all physical links of all BE services into consideration is employed. A framework to study the proposed system in terms of the average packet loss and the average system throughput is presented. The maximum number of QoS services that can be supported in the system while a predefined requirement on the average packet loss is still satisfied is investigated. A comparison study shows that our proposed scheme has higher system throughput over both conventional fixed and adaptive TDMA systems. Ronghong Mo received her B.Sc. and M. Sc. Degree from Zhongshan University, Guangzhou, China, both in Physics. From July 1999 to July 2003, she was a research scholar in the department of Electrical and Computer Engineering in National University of Singapore (NUS), toward her PhD degree. She is currently working as a research engineer in NUS. Her research interests include adaptive modulation, synchronization and channel estimation in wireless communications. Yong Huat Chew received the B.Eng, M.Eng and Ph.D. degrees in Electrical Engineering from National University of Singapore, Singapore. Since 1996, he has been with the Institute for Infocomm Research (formerly also known as Center for Wireless Communications and Institute for Communications Research), an institute under Agency for Science, Technology and Research, where he is presently a lead Scientist. His research interests are in wireless communications, transmission over HFC, DSL and all-optical networks.     

交流调速电梯中的电能质量

因为人们越来越多地使用非线性负载，电网中就存在电源质量问题。在交流传动系统中广泛使用功率变换器，由于其非线性的工作运行状态，导致电压发生畸变，从而影响敏感设备的性能。本文试图分析由功率变换器供电的电梯交流传动系统对电源质量的影响。敏感电气设备和电梯交流传动系统都连接到0．4kV输电线路上。因功率逆变器导致的电压畸变能够导致系统故障甚至电气设备中部分元件的损坏。     

网络体系结构分析和研究

本文首先简要概述了网络体系结构的现状及存在的问题,其次对未来网络体系结构与关键问题进行分析,并重点分析和研究了智能融合以及移动性资源管理与控制中的一些关键问题以及在研究方面的一些观点     

Spectral Efficiency Evaluation for MRC Diversity Schemes Over Generalized Rician Fading Channels

In this paper, closed-form expressions for the capacities per unit bandwidth for generalized Rician fading channels are derived for power and rate adaptation, constant transmit power, channel inversion with fixed rate, and truncated channel inversion adaptation policies. The closed-form solutions are derived for the single antenna reception (without diversity combining) and maximal-ratio combining (MRC) diversity cases. Truncated channel inversion adaptation policy is the best policy for the single antenna reception case, while the channel inversion with fixed rate policy is the best policy for the MRC diversity case. Constant transmit power policy provides the lowest spectral efficiency as compared to the other policies with and without diversity.     

基于J2EE技术及Struts架构的电力营销系统的设计与实现

电力营销是电力公司运营的重要环节,供电公司电力营销管理水平的高低,直接决定了该公司的自身利益和服务质量,也影响到整个行业和社会经济的发展。本文以济阳市电力营销管理信息系统为例,讨论了基于J2EE技术及Struts架构的电力营销系统的设计与的电力营销系统的设计与实现,并对开发中的主要问题进行了详细分析。     

基于VxWorks的EPON网络管理系统的设计与实现

提出了一种电信级的EPON网络管理系统设计方案,给出了该方案的系统框架与功能实现方法,重点阐述了核心功能模块的实现流程,最后通过Tornado环境下的仿真与调试验证了方案的可行性.     

户外柜式通讯电源系统设计的自然环境因素分析

列举了影响户外柜式通讯电源系统的自然环境因素，并论述了各个因素对产品可靠性的影响机理，提出了产品设计时需要考虑的要点。为该类产品的环境适应性设计和可靠性设计提供了必要的参考，对其它户外电子设备也有借鉴意义。     

国内信息无障碍的现状及展望

介绍了信息无障碍的历史沿革、国际信息无障碍的发展过程以及国内信息无障碍的现状,阐述了信息无障碍的社会意义和应用价值,列举了视障人士存在的信息获取障碍和需求范围,对信息无障碍的应用前景进行了展望,并提出信息无障碍对于需求群体、企业和研究机构、政府三者各自的权力、利益和责任。     

基于工控软件的汽车电子控制技术可视化教学系统的设计与实现

利用MCGS组态软件和数据采集卡以及汽车电子控制系统硬件。构成的汽车电子控制技术可视化教学系统,充分展开系统电子电路实物硬件,组成实时监控与仿真系统,展现汽车电子控制系统的结构组成、功能原理,实现对汽车各个电子控制系统的动态测试与仿真,实时故障检测、模拟,具有直观、方便、节省开支的优点,在汽车教学中收到较好效果。     

光伏电源智能充电控制系统的设计

以恒流充电和dV/dt技术恒压限流充电相结合的方法,采用ATMEGA8L单片机和TL494电流型PWM脉宽调制器,对12/24V太阳能直流发电系统的充电控制器进行了设计。运行实践证明,该系统简单、快速、实时性强,有利于改善蓄电池的工作状态,保证充电质量,实现无人值守的自动充电过程,提高了蓄电池的使用寿命。