Strongly Consistent Access Algorithms for Wireless Data Networks

In wireless data networks such as the WAP systems, the cached data may be time-sensitive and strong consistency must be maintained (i.e., the data presented to the user at the WAP handset must be the same as that in the origin server). In this paper, we study the cached data access algorithms in such systems. Two caching algorithms are investigated. In Algorithm I, Pull-Each-Read, whenever a data access occurs, the client always asks the server whether the cached entry in the client is valid or not. In Algorithm II, Callback, the server always invalidates the cached entry in the client whenever an update occurs. Analytic models are proposed to evaluate the performance of these algorithms. Our studies show that Algorithm II outperforms Algorithm I if the data access rate is high and the access pattern is irregular. We also design an adaptive mechanism to effectively switch between the two algorithms to take advantages of both algorithms. We also apply the single-level cached data access algorithms for the multi-level cache hierarchy. Our study indicates that with appropriate arrangement, strongly consistent cached data access for wireless Internet (such as WAP) can be efficiently supported.Yuguang Fang received the B.S. and M.S. degrees in Mathematics from Qufu Normal University, Qufu, Shandong, China, in 1984 and 1987, respectively, a Ph.D degree from Department of Systems, Control and Industrial Engineering at Case Western Reserve University, Cleveland, Ohio, in January 1994, and a Ph.D degree from Department of Electrical and Computer Engineering at Boston University, Massachusetts, in May 1997.From 1987 to 1988, he held research and teaching positions in both Department of Mathematics and the Institute of Automation at Qufu Normal University. He held a post-doctoral position in Department of Electrical and Computer Engineering at Boston University from June 1994 to August 1995. 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, Newark, New Jersey. From May 2000 to July 2003, he was an Assistant Professor in the Department of Electrical and Computer Engineering at University of Florida, Gainesville, Florida, where he has been an Associate Professor since August 2003. His research interests span many areas including wireless networks, mobile computing, mobile communications, automatic control, and neural networks. He has published over ninety papers in refereed professional journals and conferences. He received the National Science Foundation Faculty Early Career Development Award in 2001 and the Office of Naval Research Young Investigator Award in 2002. He is listed in Marquis Whos Who in Science and Engineering, Whos Who in America and Whos Who in World.Dr. Fang has actively engaged in many professional activities. He is a senior member of the IEEE and a member of the ACM. He is an Editor for IEEE Transactions on Communications, an Editor for IEEE Transactions on Wireless Communications, an Editor for ACM Wireless Networks, an Area Editor for ACM Mobile Computing and Communications Review, an Associate Editor for Wiley International Journal on Wireless Communications and Mobile Computing, and an Editor for IEEE Wireless Communications. He was an Editor for IEEE Journal on Selected Areas in Communications: Wireless Communications Series and the feature editor for Scanning the Literature in IEEE Wireless Communications (formerly IEEE Personal Communications). He has also actively involved with many professional conferences such as ACM MobiCom02, ACM MobiCom01, IEEE INFOCOM04, INFOCOM03, INFOCOM00, INFOCOM98, IEEE WCNC02, WCNC00 (Technical Program Vice-Chair), WCNC99, and International Conference on Computer Communications and Networking (IC3N98) (Technical Program Vice-Chair).Yi-Bing Lin received his BSEE degree from National Cheng Kung University in 1983, and his Ph.D. degree in Computer Science from the University of Washington in 1990. From 1990 to 1995, he was with the Applied Research Area at Bell Communications Research (Bellcore), Morristown, NJ. In 1995, he was appointed as a professor of Department of Computer Science and Information Engineering (CSIE), National Chiao Tung University (NCTU). In 1996, he was appointed as Deputy Director of Microelectronics and Information Systems Research Center, NCTU. During 1997-1999, he was elected as Chairman of CSIE, NCTU. His current research interests include design and analysis of personal communications services network, mobile computing, distributed simulation, and performance modeling. Dr. Lin has published over 150 journal articles and more than 200 conference papers.Dr. Lin is a senior technical editor of IEEE Network, an editor of IEEE Trans. on Wireless Communications, an associate editor of IEEE Trans. on Vehicular Technology, an associate editor of IEEE Communications Survey and Tutorials, an editor of IEEE Personal Communications Magazine, an editor of Computer Networks, an area editor of ACM Mobile Computing and Communication Review, a columnist of ACM Simulation Digest, an editor of International Journal of Communications Systems, an editor of ACM/Baltzer Wireless Networks, an editor of Computer Simulation Modeling and Analysis, an editor of Journal of Information Science and Engineering, Program Chair for the 8th Workshop on Distributed and Parallel Simulation, General Chair for the 9th Workshop on Distributed and Parallel Simulation. Program Chair for the 2nd International Mobile Computing Conference, Guest Editor for the ACM/Baltzer MONET special issue on Personal Communications, a Guest Editor for IEEE Transactions on Computers special issue on Mobile Computing, a Guest Editor for IEEE Transactions on Computers special issue on Wireless Internet, and a Guest Editor for IEEE Communications Magazine special issue on Active, Programmable, and Mobile Code Networking. Lin is the author of the book Wireless and Mobile Network Architecture (co-author with Imrich Chlamtac; published by John Wiley & Sons). Lin received 1998, 2000 and 2002 Outstanding Research Awards from National Science Council, ROC, and 1998 Outstanding Youth Electrical Engineer Award from CIEE, ROC. He also received the NCTU Outstanding Teaching Award in 2002. Lin is an Adjunct Research Fellow of Academia Sinica, and is Chair Professor of Providence University. Lin serves as consultant of many telecommunications companies including FarEasTone and Chung Hwa Telecom. Lin is an IEEE Fellow.     

无线传感器网络中数据存储与访问研究进展

 无线传感器网络集感知、计算和无线通信为一体,是以数据为中心的网络,因此数据存储与访问是无线传感器网络研究中的重要问题.本文围绕无线传感器网络以数据为中心这一条主线,对其中数据存储与访问的国内外研究进展进行了综述.首先概述了无线传感器网络中的数据存储与访问的概念与技术;然后详细探讨了各种数据存储策略,重点分析了分布式数据存储和信息中介;其次详细介绍了查询的分类、查询处理模型以及优化策略;最后对无线传感器网络中数据存储与访问技术进行了展望.     

无线基础数据管理系统的设计及应用研究

首先阐述了无线基础数据对于无线网络规划和优化工作的重要意义,从多方面分析了基础数据在实际工作中扮演的重要角色以及目前无线基础数据管理工作的不足,进而提出了建设B-S架构的无线基础数据管理系统,并说明了设计思路、系统结构和功能特点。从实际工作出发,介绍了基础数据的提取方式、管理方式以及使用方式,说明本文系统对实际网优工作具有积极支撑作用。     

Broadband Wireless Access Solutions - Progressive Challenges and Potential Valueof Next Generation Mobile Networks

The growth in mobile communication will accelerate over the next years. Today most of the mobile subscribers use cellular services only. But this will change in the near future towards broadband wireless access services like WiFi and WiMAX. This paper describes a fundamental overview of the broadband wireless access technologies and outlines the market view, major trends and introduces OFDM technologies. New developments for integration of broadband wireless access into the operators' infrastructure are also discussed.     

命名数据网络中可追溯且轻量级的细粒度访问控制机制

由于命名数据网络(NDN)具有网内缓存特点,任意用户可直接从中间路由节点获取数据,同时,内容提供商也无法得知用户的访问信息。针对这些问题,该文结合基于身份的组合公钥和Schnorr签名方法,提出了“三次握手”匿名安全认证协议,同时,采用改进的秘密共享方法来高效分发内容密钥,实现了一种可追溯且轻量级的细粒度访问控制机制(TLAC),最后,通过实验验证了TLAC机制的高效性。     

基于ZigBee技术的无线数据传输系统

ZigBee技术作为一种短距离、低复杂度、低功耗、低数据速率、低成本的无线通信技术,有效地弥补了短距离无线通信的一些不足和缺点。在ZigBee通信协议的基础上,设计并实现了一种短距离的无线数据传输系统。提出了一种新型的基于ZigBee技术的无线数据传输系统,同时详细介绍了其系统结构和节点设计以及软件流程设计。该系统同时结合运用了ZigBee技术和无线传感器网络技术,实现了系统的大范围覆盖、低功耗运行和性能的稳定可靠。     

基于BP神经网络的无线定位数据融合模型

针对常规TOA和TDOA的加权最小二乘法定位算法的缺点，提出了一种利用反向传播（BP）神经网络构造将TOA和TDOA定位信息的融合模型，并采用贝叶斯正则优化方法，来解决BP算法收敛慢和容易陷入局部极小值的问题。通过仿真表明，该模型具有较高的定位精度。     

无线数据通信网建设的探讨

本文介绍了无线数据通信网的概念及其接入方式，并对江苏省无线数据通信网建设作了初步探讨，基于无线数据通信的优点和特性，其有关广泛的应用前景和巨大的市场潜力，对国民经济信息化和对外经济发展有着重要意义。     

无线数据采集模块设计

在工业控制领域,常常需要采集大量的数据,然后传输给主机进行处理。这些网络多基于有线传输,在使用中有很多缺点,而无线传输具有成本低、效率高、维护方便等优势。这里介绍一种以555定时器组成的电路为主体的多参数无线数据采集模块,可对温度、压力等多种参数进行采集,并分时地用同一无线信道进行传输,有着广泛的应用前景。     

基于TTL电路的倒数计数器设计及应用

介绍了基于TTL电路设计的倒数计数器，该电路结构简单，调试方便，时间设置范围广，无需单片机开发系统和编程，用途广，易于制作。     

一种UHF频段无线数据传输系统接入点的射频前端

介绍了UHF(特高频)频段无线数据传输系统中接入点的一种射频前端。该前端包括调制器、上变频器、功率放大器、低噪声放大器、下变频器、解调器、频率合成器、增益控制和收发切换开关等电路。介绍了射频前端的实现方案以及关键部件的设计与测试。制作完成的射频前端集成在一块1 5 0mm×1 0 0mm的4层印制电路版上。该前端最大输出功率可达2W,接收灵敏度优于-100 dBm,收发切换时延小于1.5μs,满足系统指标要求。     

不同类型数据业务对无线资源的需求及影响分析

随着移动通信的迅猛发展,新数据业务层出不穷,从而对无线资源提出了更高的要求。本文即通过对TS—BS7进行测试得出各种数据业务在不同时段的流量占用情况及用户数分布,并对这些数据进行分析对比,得出移动通信承载的不同数据业务对无线控制信道、小Ⅸ数据业务信道、PCU资源以及对Gb口资源的占用情况,从而为后续更好地规划数据网络资源打下了良好的基础。     

空时码在高速无线通信系统中的应用

介绍了一种有效的信道编码方案-空时码,它不用增加传输带宽就能大幅度提高信道的吞吐量。还对空时码不同分类间的优缺点作了比较,并提出了下一步研究的方向。由于空时码具有很高的频谱利用率,所以最近有一种叫空时扩频(space-timespreading)已经作为cdma2000(3GPP2)的一种候选传输方案,还有另一种空时发射分集(STTD)也被引入到UMTSW-CDMA标准(3GPP1)中,而且它还有可能在4G中和未来无线局域网中得到广泛的应用。     

基于“无线城市”的无线宽带接入技术应用

"无线城市"正成为衡量一座城市整体运行效率、信息化程度及国际竞争力的重要尺度。WiMAX WiFi Mesh是组建"无线城市"模型的主流技术。基本方法是在城市部署若干个WiMAX基站及遍布城市的无线接入点,进而通过接入点实现无处不在的无线接入。围绕"无线城市"介绍了相关概念、采用技术、组成结构及发展趋势。     

基于GPRS的无线数据通信及其应用前景

先简要介绍GSM无线数据通信业务，强调GSM系统之所以能适应种类繁多的数据业务，是因为在GSM网络两端分别设置了2个功能单元TAF和IWF；通过数据业务的电路交换方式和分组交换方式的比较，引出GPRS，阐述了GPRS数据业务的技术优势，指出GPRS的优势就在于电路交换向分组交换的演变，并对其网络结构、无线数据接口进行了介绍；最后介绍了GPRS数据业务广泛的应用前景。     

无线POS机数据传输安全控制策略研究

研究了无线POS机具的安全策略、GPRS的安全机制、防火墙的应用及银行前置的安全认证和数据加密的应用管理等内容。     

Improving Energy Efficiency of Centrally Controlled Wireless Data Networks

Wireless network access protocols can assist nodes to conserve energy by identifying when they can enter low energy states. The goal is to put all nodes not involved in a transmission into the doze state. However, in doing so, one must tradeoff the energy and other costs associated with the overhead of coordinating dozing with the energy savings of putting nodes to sleep. In this paper, we define three alternative directory protocols that may be used by a central node to coordinate the transmission of data and the dozing of nodes. We attempt to optimize their performance by using scheduling and protocol parameter tuning. In addition, we consider the impact of errors and error recovery methods on energy consumption. Although one can argue that carefully scheduling transmissions will improve performance, ultimately, appropriately tuning protocols reduces scheduling's significance. In most cases, scheduling transmissions between the same nodes contiguously and ordering such transmissions shortest processing time first results in good performance. The most critical feature that contributes to an access protocol's effectiveness is its ability to minimize the time it takes to inform nodes that they may doze. However, the ability of our protocols to conserve energy is highly dependent on (1) network size, (2) traffic type (e.g., down/uplink, and peer-to-peer) and (3) channel bit error rate. In particular, we show that when protocols are faced with packet errors, more elaborate schemes to coordinate the dozing of nodes can pay-off. We conclude by recommending an energy conserving implementation of the IEEE 802.11 Point Coordination Function.     

多变量时间序列中基于克罗内克压缩感知的缺失数据预测算法

针对现有算法在预测多变量时间序列中的缺失数据时不适用或只适用于缺失数据较少的情况,该文提出一种基于克罗内克压缩感知的缺失数据预测算法。首先,利用多变量时间序列的时域平滑特性和序列之间的潜在相关性从时空两个方面设计了稀疏表示基,从而将缺失数据预测问题建模成稀疏向量恢复问题。模型求解部分,根据缺失数据的位置特点设计了适合当前应用场景且与稀疏表示基相关性低的观测矩阵。接着,从稀疏表示向量是否足够稀疏和感知矩阵是否满足有限等距特性两个方面验证了模型的性能。最后,仿真结果表明,所提算法在数据缺失严重的情况下具有良好的性能。

     

基于无线传感器网络的数据采集系统设计

传统的单点测量环境数据的采集系统无法给出被监测区域内的准确环境数据,不能满足精确测量的要求。利用无线传感器网络具有分布式多点测量的优势,设计了基于无线传感器网络的环境温度和光照度的环境数据采集系统。实验结果表明,该系统能够实时采集测量区域的温度和光照度环境数据,并可绘制出测量区域内温度和光照度的空间分布图,实现监测区内的精确测量。     

基于nRF905的无线数据传输设备设计

短距离无线通信以其使用便捷和功耗低等优势得到了广泛应用。设计了基于无线数据收发芯片nRF905、以ATmega16为主处理芯片的无线数据传输设备,给出了无线数据传输系统框图和硬件电路。同时,制定了外部数据设备和无线数据传输模块之间的串行通信协议,介绍了nRF905的配置及收发流程、USART和SPI等接口软件的设计方案,给出了系统主程序流程图。最终实现了该无线数据传输设备,实验表明该设备能完成高速有效的数据传输功能。