分类：设计开发    下载：0    浏览：834    时间：2017-07-29

翟临博，张晓敏 (山东大学信息学院，济南 250100) 摘要：提出了一种在非理想信道下分析IEEE 802.11无线局域网的饱和吞吐量的方法。分析的过程中考虑到信道“捕获”和退避“冻结”的问题，采用条件概率建立了数学模型。在IEEE 802.11b无线局域网定义的不同数据速率下，利用该方法对基本访问机制和RTS/CTS访问机制进行了分析。仿真表明，分析结果与DCF模式下的饱和吞吐量是吻合的。 关键词：802.11；802.11b；无线局域网；饱和吞吐量 Performance Analysis of Wireless LANs for Lossy Channel ZHAI Linbo, ZHANG Xiaomin (Information College, Shandong University, Jinan 250100) 【Abstract】This paper presents a way to estimate the saturation throughput of IEEE 802.11 for a lossy channel. The analysis which isinvolved incapture effects and backoff freezing procedures, is based on elementary conditional probability arguments. It uses this way to analyze theperformance of the basic access and RTS/CTS access mechanisms of IEEE 802.11b. Simulation results show the analysis accurately predicts thesaturation throughput in DCF mode. 【Key words】802.11; 802.11b; Wireless LANs; Saturation throughput

分类：设计开发    下载：0    浏览：953    时间：2017-07-29

高昊江，杨 晟，张宜生，梁书云 (华中科技大学模具技术国家重点实验室，武汉 430074) 摘要：恶劣环境下无线信号会出现时断时续的不稳定现象，导致传统的保持在线连接的通信方法不能正常工作。为此，提出了一种“信号－时间窗”分析指引下的基于FTP协议传送经混沌加密及压缩处理的XML文档的数据通信策略，给出了其在恶劣信道下成功应用的实例。系统投入运行半年多的实践结果表明，该通信策略能很好地解决恶劣环境下的数据通信问题，保证了通信的敏捷性、完整性、保密性和可靠性，在恶劣通信条件下或异构系统之间的数据通信领域具有相当的应用价值和参考意义。 关键词：恶劣环境；数据通信策略；混沌加密；XML；系统安全 Research and Application of Wireless Network Data Communication Strategy in Adverse Environments GAO Haojiang, YANG Sheng, ZHANG Yisheng, LIANG Shuyun (State Key Lab of Plast. Form. Simulation, Huazhong University of Science and Technology, Wuhan 430074) 【Abstract】In adverse environments, wireless communication speed is slow and often breaks down. It causes the traditional keeping-in-connectioncommunication methods do not work. To resolve this problem, a communication strategyis presented, which uses signal time window and FTP totransmit chaotic-encrypted and compressed XML document. The application example is also given, which has been put to use for more than half ayear. The experiments and application results show that the proposed communication strategydoes good work at bad communication conditions, andhas the advantages of agility, completeness, security and stability, which can be widely applied in the data communication fields under badcommunication conditions or between different systems. 【Key words】Adverse environments; Data communication strategy; Chaotic encryption; XML; System security

分类：设计开发    下载：0    浏览：793    时间：2017-07-29

张文柱, 李建东, 王　炫 (西安电子科技大学信息科学研究所,陕西西安　710071) 摘要: 基于场景用仿真方法研究了3 种适用于分布式无线网络的路由协议及其网络性能. 仿真结果表明,当通信半径一定时,3 种路由协议的网络性能均随着网络中节点运动速度的提高而变差;当节点运动速度一定时,3 种路由协议的网络性能均随着节点通信半径的增加而变好;同等条件下,Ad2hoc 按需距离矢量路由协议的端到端通过量高于动态源路由协议和目标序列距离矢量路由协议,分组丢失率低于动态源路由协议和目标序列距离矢量路由协议,而目标序列距离矢量路由协议的平均分组传输时延保持最低. 关键词: 分布式无线网络;路由协议;网络性能

分类：设计开发    下载：0    浏览：1022    时间：2017-07-29

段中兴1,2，张德运1 (1. 西安交通大学电子与信息工程学院，西安 710049；2. 西安建筑科技大学信控工程学院，西安 710055) 摘要：为了提高IEEE 802.11中速率选择机制的性能，提出了一种基于多信道参数数据融合算法的自动速率选择机制，克服了采用单一参数进行信道状态估计的误差和误判。在发送端，将获取到的RSS、CIR和PER信息模糊化，并运用模糊集理论进行模糊推理，形成单一参数对信道质量评估的局部决策，经过融合中心的合成运算和决策规则得到信道质量的全局判决，以此进行最佳发送速率的选择。该算法在NS2网络仿真软件的Ricean信道模型下进行了仿真。仿真结果表明该机制比固定速率和单一参数信道估计机制提高了28.4%和22.2%的平均吞吐量。 关键词：无线局域网；数据融合；速率自动选择；模糊评判 Rate Adaptation Algorithm in Multi-rate WLAN DUAN Zhongxing1,2, ZHANG Deyun1 (1. School of Electronics and Information Engineering, Xi’an Jiaotong University, Xi’an 710049; 2. School of Information and Control Engineering, Xi’an University of Architecture and Technology, Xi’an 710055) 【Abstract】A data fusion algorithm is adopted to enhance the performance of auto rate selection mechanism in IEEE 802.11 based on fuzzy systemtheory, and with the application of this mechanism, the misjudgement of channel state which estimated by single channel parameter is eliminated. Insender, the received signal strength (RSS) and carrier to interface ration (CIR) and packet error ratio(PER) value that sensors obtain is fuzzed, andeach of them is used by fuzzy logic control to make part judgement about the channel quality. The best rate is selected based on the decision whichobtained through the synthetic operation and decision rule of the data fusion center.Simulation results show that the mechanism enhances meanthroughput performance of IEEE 802. 11 system compared with that presented in the literature. Compared with the fixed transmit rate mechanism,the enhancement reaches 28.4 % , and with the single parameter estimated mechanism, the enhancement reaches 22.2 %. 【Key words】Wireless local area network(WLAN); Data fusion; Auto rate selection; Fuzzy assessment

分类：设计开发    下载：6    浏览：966    时间：2017-07-29

张 强，赵 政 (天津大学电信学院，天津 300072) 摘要：提出了一种基于地理位置信息的无线网络路由协议LADRU，以增强高移动性网络TCP的性能。协议采用单播和广播相结合的礼花式广播来减少系统开销，以随机竞争方式探测路由，减少寻找新路由的代价。通过估计网络节点的运动速率来自动调节路由探测周期，使路由得到及时更新。采用标签路由方法传递数据包，解决源路由方式数据包头过大和路由切换问题。仿真结果表明LADRU能有效地提高数据传输率和系统吞吐率。 关键词：TCP；地理位置；随机竞争；标签路由 Routing Protocol for TCP in High Mobility Ad-hoc Networks ZHANG Qiang, ZHAO Zheng (School of Electronic Information Engineering, Tianjin University, Tianjin 300072) 【Abstract】A geographical location based routing protocol is presented to augment TCP performance in high mobility wireless ad-hoc networks.This paper introduces a skyrocket broadcast by the integration of unicast and broadcast, which can drop system overhead. A new routing detectionmethod is introduced based on random competition, which reduces the cost of routing discovery. The routing can be updated in time throughperiodic routing detection whose interval is adjusted automatically according to the estimation of nodes’ speed.The data packets are transmitted by anew label routing method that can reduce the packets’ head and make it easy to switch to a new routing. The simulation shows that LADRU canincrease delivery ratio and throughput of TCP. 【Key words】TCP; geographical location; random competition; label routing

分类：设计开发    下载：0    浏览：543    时间：2017-07-29

摘要 IEEE802.11b( 研究表明! 只要重叠或相邻C11 小区中心频率相距%E2/0 以上! 就可以有效避免同频或邻频干扰" 在C11 小区密集地区! 需要严格的频率规划" 提出并实现适用于IEEE802.11b( 的一种抗干扰自适应频率规划机制" 测试表明! 在无严格频率规划条件下! 该机制能抗同频或邻频干扰和其它窄带信号干扰改善性能" 关键词:WLAN  抗干扰自适应频率规划

分类：设计开发    下载：2    浏览：873    时间：2017-07-29

刘军, 郭伟, 肖百龙, 黄飞 ( 电子科技大学通信抗干扰技术国家级重点实验室, 四川成都610054) 摘要: 通过分析IEEE 802. 11 DCF 的分组发送过程, 获得了RTS 和基本方式下分组传输的时间开销。给出了以最小化传输时间开销代价为优化目标的最优RTS 门限的计算公式。通过对当前信道分组发送的成功概率Ps 的预测, 实现了最优RTS 门限的计算, 并给出了一个具体的自适应RTS 门限调整算法, 使终端能自动调整其RTS 门限以达到或接近最优值。仿真表明自适应RTS 门限调整算法有效减小了MAC 分组传送的时间开销, 提高了信道的传输效率。 关键词: 无线局域网; 802. 11 DCF; RTS 门限; 分组成功传送概率; 自适应RTS 门限调整

分类：设计开发    下载：0    浏览：994    时间：2017-07-29

初建朋，李小进，赖宗声 (华东师范大学微电子电路与系统研究所，上海 200062) 摘 要：分析了802.11a无线局域网(WLAN)OFDM基带接收系统中频率同步和信道估计算法的运算特点。针对实际算法的特点，设计了一个面向应用的专用DSP处理器(ASP)，利用ASP可以以软件方式实现802.11a前导序列的接收。经实际流片验证表明，该设计可以实现11a前导序列接收的各种基带处理运算，具有高度的灵活性和较小的芯片面积。 关键词：正交频分复用；软件无线电；面向应用数字信号处理器；软硬件协同设计；无线局域网 Analysis and ASP Realization of 802.11a Frequency Sync. and Channel Est. CHU Jianpeng, LI Xiaojin, LAI Zongsheng (Institute of Microelectronics Circuit & System, East China Normal University, Shanghai 200062) 【Abstract】This paper analyzes the calculation cost and characteristics of 802.11a preamble receiving. Realization of these algorithms using SDR,which is based on an application specific DSP and S/W codesign, is introduced. An effectively DSP processor architecture is designed. The testresults show this design is able to implement 11a baseband process effectively and flexibly. 【Key words】OFDM; SDR; ASP; SW/HW codesign; WLAN

分类：设计开发    下载：0    浏览：840    时间：2017-07-29

3GPP网络同WLAN互连方案分析

分类：设计开发    下载：0    浏览：947    时间：2017-07-29

王春东1,2，王秀峰1 (1. 南开大学信息科学技术学院，天津 300071；2. 天津理工大学计算机科学与工程系，天津 300191) 摘要：研究了在基于802.11的系统中，如何通过信号强度进行移动设备的室内定位。在研究并实现最大群中心定位算法MCCPA的基础之上，给出了一种利用移动终端的历史位置信息对定位结果进行修正的室内定位算法(MMCCPA)。其主要思想是，在给定前一时间使用者所在位置的条件下，将使用者出现在特定范围的概率列入考量加以修正，并作为对环境因素影响的调整，这样不仅减少计算量，而且明显提高了位置估算的正确率。 关键词：无线网络；信号强度；定位算法；802.11；历史记录 Research on 802.11-based Indoor Positioning Algorithm WANG Chundong1,2, WANG Xiufeng1 (1. College of Information Science Technology, Nankai University, Tianjin 300071; 2. Dept. of Computer Science & Engineering, Tianjin University of Technology, Tianjin 300191) 【Abstract】This paper focuses on how to position the mobile device indoor by using signal strength in 802.11-based system. It introduces a802.11-based positioning system called the maximal cluster centered positioning algorithm (MCCPA). The MCCP system locates mobile objects viacollecting the sensed power strengths of the mobile objects to multiple wireless access points. Based on realizing MCCPA, the paper gives a newalgorithm named MMCCPA to correct the positioning results by using the history record information of mobile devices. The main idea of MMCCPAis that it also considers the probability of users’ appearance in the specific area in order to correct results, as an adjustment to the environmentfactors, so as to increase the preciseness and decrease the count quantity.The experimental results show that the location information provided byMMCCPA assures higher correctness than MCCPA. 【Key words】Wireless networks; Signal strength; Positioning algorithm; 802.11; History record

分类：设计开发    下载：0    浏览：1002    时间：2017-07-29

李骐，陈 涤 (山东大学信息科学与工程学院，济南 250100) 摘 要：研究了实时多媒体业务传输协议在无线－有线混合网络中所面临的新问题，在此基础上提出了一种基于TCP友好速率控制协议的新的实时业务的流控机制，利用延迟抖动率作为丢包分辨信号来调整TFRC的速率控制，以区分拥塞丢包和无线信道丢包。大量的NS仿真实验表明：该算法在无线－有线混合网络中能提高有效通过量，对于TCP流具有良好的公平性。 关键词：无线－有线混合网络；TCP友好速率控制；延迟抖动率；NS-2 TCP-friendly Rate Control Algorithm Based on Wireless-wired Hybrid Network LI Qi, CHEN Di (School of Information Science and Engineering, Shandong University, Jinan 250100) 【Abstract】Real time multimedia transport protocols in wireless-wired hybrid network are facing new challenges. On the basis of extensive studyof characteristics of wireless-wired hybrid network and the current TFRC mechanism, this paper proposes a new TCP-friendly rate controlmechanism for real-time traffics. The new mechanism uses Jitter ratio as the signal to differentiate congestion losses and wireless link losses to adjustTFRC’s rate control algorithm. Extensive simulations on NS-2 verify that the new mechanism has better performance than TFRC as well as keepsreasonable friendliness to TCP flows. 【Key words】Wireless-wired hybrid network; TCP-friendly rate control (TFRC); Jitter ratio; NS-2

分类：设计开发    下载：0    浏览：1156    时间：2017-07-29

明 亮1,2，谢桂海1，齐子元1，王新锋1，彭德云1 (1. 军械工程学院计算机工程系，石家庄 050003；2. 北京系统工程研究所，北京 100101) 摘 要：提出了基于无线网的视频智能监控系统的原理结构、带宽适应性和智能监控的实现方法，描述了系统中使用的无线组网、基于SPIHT视频编解码算法和基于内容的视频识别等关键技术，给出了系统实现后的实际测试结果及相关性能指标。 关键词：无线网；智能监控；网络视频；流媒体 WLAN-based Remote Video Intelligent Surveillance System MING Liang1,2, XIE Guihai1, QI Ziyuan1, WANG Xinfeng1, PENG Deyun1 (1. Department of Computer Engineering, Ordnance Engineering College, Shijiazhuang 050003; 2. Beijing Institute of System Eengineering, Beijing 100101) 【Abstract】This paper introduces a video intelligent surveillance system, and presents the structure of the system, adaptability for bandwidth andthe method for intelligent surveillance. It describes the key technologies, such as WLAN, efficient video coding arithmetic based on SPIHT(setpartition in hierarchical trees), intelligent alarm aroused by video-recognizing, and so on, gives out the testing results and important parameter ofperformance by realizing the system. 【Key words】WLAN; Intelligent surveillance; Network video; Streaming media