IEEE1394在大幅面彩色数字复印机中的应用

本文简要描述了IEEE1394的基本特征,着重讨论了基于1394接口的,在大幅面彩色数字复印机的扫描单元和转印单元之间进行数据传输的一种简易方法,实践证明这个方法是可行的。文章还给出了IEEE1394同步和异步传输的程序代码示例。     

基于以太网的智能家庭网络系统设计

随着物质生活水平的不断提高，家居网络技术的发展和应用正日益对整个社会产生巨大的影响。信息家电的出现和家庭网络技术的发展，促进了智能化、网络化家庭的实现。根据当前网络的发展现状，通过对家庭网络平台及其主网关的分析和研究，以太网为主干的智能家庭网络系统，将能实现对家庭设备的智能化管理与控制；再结合家庭网关和Inernet，必将为居民营造出现代化的家居生活环境。     

无线局域网在医疗中的应用

作为个人通信的一个重要组成部分，无线局域网已经掀起移动计算的新浪潮。无线技术在传榆速率、安全性方面不断改进，它不仅是有线网络的无线延伸，也可以作为LAN的无线替代。通过分析3种不同的IEEE802.11扩展标准的调制方式、工作频段等，突出说明了IEEE802.llg标准的优越性。根据医疗领域的特殊性，在基于IEEE802.11g基础上，初步构建了一个可扩展的无线医疗网络。     

一种改进IEEE802.15.3MAC协议机制的信道资源分配算法

本文简单介绍了IEEE802.15.3协议,分析了协议的MAC层QoS机制。针对实时VBR(VariableBitRate)业务流,提出了一种改进协议机制的信道资源分配算法,并在性能上与平均资源分配算法进行了分析和比较,通过仿真验证了此分配算法能有效降低实时VBR码流的丢帧率,提高系统传输的QoS性能。     

Perturbing and evaluating numerical programs without recompilation—the wonglediff way

wonglediff is a program that tests the sensitivity of arbitrary program executables or processes to changes that are introduced by a process that runs in parallel. On Unix and Linux kernels, wonglediff creates a supervisor process that runs applications and, on the fly, introduces desired changes to their process state. When execution terminates, it then summarizes the resulting changes in the output files. The technique employed has a variety of uses. This paper describes an implementation of wonglediff that checks the sensitivity of programs to random changes in the floating‐point rounding modes. It runs a program several times, ‘wongling’ it each time: randomly toggling the IEEE‐754 rounding mode of the program as it executes. By comparing the resulting output, one gets a poor man's numerical stability analysis for the program. Although the analysis does not give any kind of guarantee about a program's stability, it can reveal genuine instability, and it does serve as a particularly useful and revealing idiot light. In our implementation, differences among the output files from the program's multiple runs are summarized in a report. This report is in fact an HTML version of the output file, with inline mark‐up summarizing individual differences among the multiple instances. When viewed with a browser, the differences can be highlighted or rendered in many different ways. Copyright © 2004 John Wiley & Sons, Ltd.     

An enhancement to the IEEE 802.11e EDCA providing QoS guarantees

One of the challenges that must be overcome to realize the practical benefits of ad hoc networks is quality of service (QoS). However, the IEEE 802.11 standard, which undeniably is the most widespread wireless technology of choice for WLANs and ad hoc networks, does not address this issue. In order to support applications with QoS requirements, the upcoming IEEE 802.11e standard enhances the original IEEE 802.11 MAC protocol by introducing a new coordination function which has both contention-based and contention-free medium access methods. In this paper, we consider the contention-based medium access method, the EDCA, and propose an extension to it such that it can be used to provide QoS guarantees in WLANs operating in ad hoc mode. Our solution is fully distributed, uses admission control to regulate the usage of resources and gives stations with high-priority traffic streams an opportunity to reserve time for collision-free access to the medium.     

The 802.11n MIMO-OFDM Standard for Wireless LAN and Beyond

An overview is given of the new IEEE 802.11n standard. This is the first wireless LAN standard based on MIMO-OFDM, a technique pioneered by Airgo Networks to give a significant performance increase in both range and rate relative to conventional wireless LAN. Performance results show that net user throughputs over 100 Mbps are achievable, which is about four times larger than the maximum achievable throughput using IEEE 802.11a/g. For the same throughput, MIMO-OFDM achieves a range that is about 3 times larger than non-MIMO systems. This significant improvement in range-rate performance makes MIMO-OFDM the ideal solution not only for wireless LAN, but also for home entertainment networks and 4G networks. Richard van Nee received the M.Sc. degree in Electrical Engineering from Twente University in Enschede, the Netherlands, in 1990. In May 1995, he received the PhD degree from Delft University of Technology. From 1995 to 2000, he worked for Lucent Technologies Bell Labs on wireless LAN transmission techniques. He was one of the original proposers of the CCK and OFDM modulation techniques which were adopted by the IEEE 802.11b and IEEE802.11a wireless LAN standards. In 2001, he cofounded Airgo Networks that developed the first MIMO-OFDM modem for wireless LAN and which techniques form the basis of the IEEE 802.11n standard. Together with Ramjee Prasad, he wrote a book on OFDM, entitled ‘OFDM for Mobile Multimedia Communications.’ In 2002 he received the Dutch Veder award for his contributions to standardization of wireless communications.     

差错信道下IEEE 802.11 DCF最优帧长分析及信道自适应策略

分析了差错信道下IEEE 802.11 DCF在饱和状态下的吞吐量以及帧长度对吞吐量的影响.研究表明在一定的误码率（BER）下存在最优的帧长使得系统吞吐量最大,并且该最优值与发送节点的数目无关.在此基础上,提出了一种简单的基于BER区间划分的帧长控制的信道自适应发送策略.仿真表明,与固定帧长的发送策略相比较,使用该策略在差错信道下可以有效地提高吞吐量.     

无线城域网中中心调度的竞争解决方案

针对无线城域网PMP模式下的竞争问题，提出了一种中心调度的竞争解决方案CSCR（centralized scheduling contention resolution）。通过对每一时间帧内活动用户站（subscriber stations）数目的预测，基站（basestation）给所有用户站提供了一个优化的竞争窗口，所有用户站都采用该窗口独立地参与竞争。理论分析和模拟结果表明，与IEEE802．16推荐的基于二进制指数回退BEB（binary exponential backoff）算法的方案相比，CSCR方案不但易于实现，而且能更加有效地利用无线资源，同时减少请求接入延时。