基于IEEE802.15.4退避算法的改进机制

IEEE802.15.4是供低速率、低功耗和低成本设备使用的短距离无线通信的协议,定义了低速无线个域网(LR-WPANs)的MAC层和物理层规范.由于在例如无线体域网(WBAN)应用中,能量消耗是备受关注的问题,因此提出了一种基于时槽机制的CSMA/CA过程中改进的退避算法,在每次CSMA/CA开始时根据过去的传输状况动态地调整竞争窗口的最小值.通过NS-2进行仿真,实验结果表明这样的改进方案在业务负载比较高或者包的大小比较小的时候可以减少数据包碰撞概率和重传概率,从而可以减少功耗并且提高吞吐量性能.     

WAPI与IEEE 802.11i安全协议通信性能分析

网络的安全性及通信性能是用户最为关注、也是最影响无线局域网技术应用的两个方面。然而不同安全协议工作过程的差异化将导致网络性能各不相同。文中在研究无线局域网的两种主要安全协议WAPI和IEEE 802．11i的基础上，分别对其数据吞吐量及用户接入时延这两个最关键的通信性能进行定性和定量分析。分析结果表明WAPI在安全性及通信性能均优于802．11i。文中最后并提出了进一步改进WAPI通信性能的思路。     

IEEE 802.11 DCF对TCP性能的影响及算法改进

本文讨论了IEEE 802.11 DCF两种方式(RTS/CTS和CSMA/CA)混合工作时TCP的性能,发现高负载时TCP流存在不稳定的问题.基于此提出了RWB(Reserve Window Backoff)算法,该算法从联合优化的角度出发,减轻了WLAN MAC接入机制和TCP拥塞控制之间的不良影响,从而提高了TCP的吞吐量,改善了TCP流的稳定性.文中通过仿真对算法进行了分析和研究.     

基于ZigBee无线通信的汽车倾斜度测量的应用

引言ZigBee是一种新的无线局域网传输标准,它是基于IEEE802.15.4协议基础的一个通信标准。IEEE802.15.4定义了协议的物理层和媒体介质访问控制层(MAC),而ZigBee定义了网络层、安全层和应用层,见图1。这样,     

IEEE802.16e的休眠模式性能评估与优化

IEEE802.16e终端具有移动性,导致其系统配置受限于电池容量。而休眠模式作为移动终端的必备功能,它能有效地管理有限的电池容量,延长移动终端的单次充电使用时间。该文回顾了IEEE802.16e移动终端休眠模式的3种功率节省类型,通过建模移动终端的休眠模式,研究了多种功率节省类型相组合的情况,探讨了休眠模式状态下移动终端的平均能量消耗和平均能量节省问题。通过系统模型仿真,提出了基于参数配置变化的休眠模式性能评估及优化的方法。     

IEEE802.11与高级红外无线AIr MAC协议的性能比较

红外线作为室内通信无线传输媒质,具有低成本、低功耗等特点.本文描述 了IEEE 802.11红外局域网媒质访问控制协议（MAC）和红外数据协会（IrDA）提出的高级红外媒质访问控制层协议（AIr MAC）;研究了两种协议性能估计模型并利用OPNET仿真工具对IEEE 802.11 MAC与高级红外AIr MAC接入性能进行了仿真验证.通过对两种MAC协议接入方式、吞吐量性能估计模型以及吞吐量性能仿真结果进行比较分析,总结了IEEE 802.11红外局域网媒质接入协议和高级红外媒质接入协议之间的不同之处.     

IEEE802.15.4协议的性能分析与仿真

IEEE 802.15.4是一个自组织的无线网络标准,其中制定了PHY层和MAC层规范,主要应用场合为低成本、低功耗、低复杂度的无线个域网.许多参数在IEEE 802.15.4标准中仅给出取值范围而并未给出确定的值,虽然这些值对系统性能有着较为显著的影响.个域网中的设备大量采用电池供电,因此实现更低的能量消耗是该网络标...     

Analysis of bandwidth allocation algorithms for wireless personal area networks

A major issue in the design and operation of ad hoc networks is sharing the common spectrum among links in the same geographic area. Bandwidth allocation, to optimize the performance of networks in which each station can converse with at most a single neighbor at a time, has been recently studied in the context of Bluetooth Personal Area Networks. There, centralized and distributed, capacity assignment heuristics were developed, with applicability to a variety of ad hoc networks. Yet, no guarantees on the performance of these heuristics have been provided. In this paper, we extend these heuristics such that they can operate with general convex objective functions. Then, we present our analytic results regarding these heuristics. Specifically, we show that they are β-approximation (β<2) algorithms. Moreover, we show that even though the distributed and centralized algorithms allocate capacity in a different manner, both algorithms converge to the same results. Finally, we present numerical results that demonstrate the performance of the algorithms. Randeep Bhatia received the Ph.D. degree in Computer Science from University of Maryland, the M.S. degree in Mathematics and Computer Science from University of Illinois at Chicago and the B.Tech. degree in Computer Science and Engineering from Indian Institute of Technology, Delhi. He is currently with the High Speed Networks Research Department at Bell Labs, Lucent technologies, working on network design, traffic engineering and scheduling algorithms. His current research interests are in the area of QoS for multimedia services in wireless data networks. Adrian Segall received the B.Sc. and M.Sc. degrees in electrical engineering from the Technion, Israel Institute of Technology in 1965 and 1971, respectively, and the Ph.D. degree in electrical engineering with a minor in statistics from Stanford University in 1973. After serving active duty in the Israel Defense Forces, he joined in 1968 the Scientific Department of Israel’s Ministry of Defense. From 1973 to 1974 he was a Research Engineer at System Control Inc., Palo Alto, CA and a Lecturer at Stanford University. From 1974 to 1976 he was an Assistant Professor of Electrical Engineering and Computer Science at the Massachusetts Institute of Technology. From 1987 to 1998 he was on the faculty of the Department of Computer Science at the Technion. He is presently Benjamin Professor of Computer-Communication Networks in the Department of Electrical Engineering, Technion, Israel Institute of Technology. From 1982 to 1984 he was on leave with the IBM T.J.Watson Research Center, Yorktown Heights, NY. He held visiting positions with IBM, AT&T and Lucent Bell Labs. His current research interests are in the area of optical networks, wireless, sensor and ad-hoc networks. Dr. Segall is an IEEE Fellow and has served in the past as Editor for Computer Communication Theory of the IEEE Transactions on Communications, Editor for the IEEE Information Theory Society Newsletter and Senior Editor for the IEEE Journal on Selected Areas in Communications. He was selected as an IEEE delegate to the 1975 IEEE-USSR Information Theory Workshop, and is the recipient of the 1981 Miriam and Ray Klein Award for Outstanding Research and of the 1990 Taub Award in Computer Science. Gil Zussman received the B.Sc. degree in Industrial Engineering and Management and the B.A. degree in Economics (both summa cum laude) from the Technion—Israel Institute of Technology in 1995. He received the M.Sc. degree (summa cum laude) in Operations Research from Tel-Aviv University in 1999 and the Ph.D. degree in Electrical Engineering from the Technion—Israel Institute of Technology in 2004. Between 1995 and 1998, he served as an engineer in the Israel Defense Forces. He is currently a Postdoctoral Associate in the Laboratory for Information and Decision Systems in MIT. His current research interests are in the area of ad hoc and sensor networks. In particular, he is interested in energy efficient protocols, medium access control protocols, and personal area networks. Gil received the Knesset (Israeli Parliament) Award for distinguished students, the Best Student Paper Award at the IFIP-TC6 Networking 2002 Conference, and the IEEE Communications Magazine Best Paper Award at the OPNETWORK 2002 Conference. In 2004 he received the Marie Curie Outgoing International Fellowship and the Fulbright Fellowship.     

人体局域网的MAC层分析与研究

在分析人体局域网的背景和研究现状的基础上,指出MAC协议是影响人体局域网整体性能的关键技术之一.总结分析MAC层协议的研究现状,并对IEEE802.15.6标准中定义的MAC协议进行详细的探讨,进而分析了BAN的网络拓扑结构.最后,对人体局域网MAC协议研究中面临的挑战进行讨论,给出MAC协议未来的研究方向.     

基于无线802.16dMesh的电力线路抢修、巡检通信网络系统

安全稳定的电力保障是社会生活中的一件大事,电力运行中出现的任何故障都可能给正常的社会生活、生产带来严重的影响并造成巨大的经济损失。本文首先介绍了802.16d协议Mesh模式下的MAC帧结构,然后提出了一种基于IEEE 802.16d无线Mesh网络的电力线路抢修、巡检通信网络系统。系统依托MESH网络将采集得到的信息发送到信息处理中心系统。系统具有保密、易于开设使用和建网费用低廉等特点。