Performance modeling and evaluation of data/voice services in wireless networks

Application-level performance is a key to the adoption and success of the CDMA 2000. To predict this performance in advance, a detailed end-to-end simulation model of a CDMA network is built to include application traffic characteristics, network architecture, network element details using the proposed simulation methodology. We assess the user-perceived application performance when a RAN and a CN adopt different transport architectures such as ATM and IP. To evaluate the user-perceived quality of voice service, we compare the end-to-end packet delay for different vocoder schemes such as G.711, G.726 (PCM), G.726 (ADPCM), and vocoder bypass scheme. By the simulation results, the vocoder bypass scenario shows 30% performance improvement over the others. We also compare the quality of voice service with and without DPS scheduling scheme. We know that DPS scheme keep the voice delay bound even if the service traffic is high. For data packet performance, HTTP v.1.1 shows better performance than that of HTTP v.1.0 due to the pipelining and TCP persistent connection. We may conclude that IP transport technology is better solution for higher FER environment since the packet overhead of IP is smaller than that of ATM for web browsing data traffic, while it shows opposite effect to the small size voice packet in RAN architecture. We show that the 3G-1X EV-DO system gives much better packet delay performance than 3G-1X RTT. The main conclusion is that end-to-end application-level performance is affected by various elements and layers of the network and thus it must be considered in all phases of the development process. Jae-Hyun Kim He received the B.S., M.S., and Ph.D. degrees, all in computer science and engineering, from Hanyang University, Ansan, Korea, in 1991, 1993, and 1996 respectively. In 1996, he was with the Communication Research Laboratory, Tokyo, Japan, as a Visiting Scholar. From April 1997 to October 1998, he was a post-doctoral fellow at the department of electrical engineering, University of California, Los Angeles. From November 1998 to February 2003, he worked as a member of technical staff in Performance Modeling and QoS management department, Bell laboratories, Lucent Technologies, Holmdel, NJ. He has been with the department of electrical engineering, Ajou University, Suwon, Korea, as an assistant professor since 2003. His research interests include QoS issues and cross layer optimization for high-speed wireless communication. Dr. Kim was the recipient of the LGIC Thesis Prize and Samsung Human-Tech Thesis Prize in 1993 and 1997, respectively. He is a member of the Korean Institute of Communication Sciences (KICS), Korea Institute of Telematics and Electronis (KITE), Korea Information Science Society (KISS), and IEEE. Hyun-Jin Lee received the B.S. degree in electrical engineering from Ajou University, Suwon, Korea, in 2004, and is working toward the M.S. degree and Ph. D. degree in electrical engineering at Ajou University. He has been awarded Samsung Human-Tech Thesis Prize in 2004. His research interests QoS, especially network optimization and wireless packet scheduling. He is a member of the KICS. Sung-Min Oh received the B.S. and M. S. degrees in electrical engineering form Ajou University, Suwon, Korea, in 2004, and is working toward the Ph. D. degree in electrical engineering at Ajou University. His research interests QoS performance analysis and 4G network. He is a member of the KICS. Sung-Hyun Cho received his B.S., M.S., and Ph.D. in computer science and engineering from Hanyang University, Korea, in 1995, 1997, and 2001, respectively. From 2001 to 2005, he has been with Samsung Advanced Institute of Technology, where he has been engaged in the design and standardization of MAC and upper layers of B3G, IEEE 802.16e, and WiBro systems. He is currently a MAC part leader in the telecommunication R&D center of Samsung Electronics. His research interests include 4G air interface design, radio resource management, cross layer design, and handoff in wireless systems.     

Investigation of driving performance, vection, postural sway, and simulator sickness in a fixed-based driving simulator

This paper reports the results of a pilot study conducted to determine whether there is a relationship between simulator sickness and measures of driver inputs, vection, and postural sway, in a fixed base driving simulator. Seven males and four females performed a series of alternating left and right turns (20 each), with straigth-aways inbetween. The task was designed to promote experiences of circular and linear vection, and associated sway. It was hypothesized that greater driver inputs (i.e., steering wheel and braking activity; deviation from the centerline) would correlate: with reports of vection and measures of postural sway. Ten of the eleven subjects reported moderate sickness, which precluded any statistical comparisons between “sick” and “not sick” however, there was a significant tendency for persons who reported vection to also report sickness. There were no gender differences in reported incidence of vection or sickness, however, males tended to exhibit greater lateral velocity. The next phase of investigation will necessitate reducing the strength of the stimulus (i.e., require less turns) to increase variability of sickness scores amongst subjects and permit comparisons between “sick” and “not sick.” Measurement considerations include increasing the sensitivity of vection ratings, and examination of the timecourse for the development of postural sway.     

Towards identifying the roll motion parameters of a motorcycle simulator

This study aimed at identifying the roll motion parameters of a motorcycle simulator prototype. Experienced motorcyclists tuned the angular physical movement of the mock-up and that of the visual scene to achieve an optimal riding experience during curves. The participants exceeded the rolling angles that would be required in real-world riding, while avoiding leaning the mock-up beyond 10°. In addition, they were more influenced by the speed of the virtual motorcycle than by road curvature, especially in a wide field of view. Heterogeneity was found in the roll applied to the visual scene. The overall patterns suggest that at least when washout is not applied to remove the side forces that in real-world riding are compensated by a centrifugal force, greater roll of the visual at the expense of the mock-up is mandatory to avoid performance biases that might be enhanced due to fear of falling off the simulator. Future roll motion models must take into consideration factors such as riding postures, which might not only influence the forces operating on the rider-motorcycle system, but also how motorcyclists perceive the visual world.     

基于TCN的地铁列车控制方案的研究

本文针对地铁车厢内控制设备分散的问题,设计了基于TCNRTP的地铁列车控制网络系统。采用NS2网络模拟软件构建的虚拟网络环境,编写消息数据传输层协议,通过测试列控网络的通信效率,得出了影响通信效率的因素;通过配置列控通信设备的基本功能和设定装置运行参数达到配置网络化通信的目的。     

驾驶员转向特性分类与在线辨识研究

针对汽车驾驶员转向特性分类与在线辨识问题,基于驾驶模拟器实验台,设计典型实验工况,选取具有一定驾驶经验的驾驶员进行实验研究。采集驾驶员转向过程实验数据并提取特征值,应用模糊C均值聚类算法将驾驶员转向特性分为谨慎型、一般型和激进型三类;根据分类实验数据应用BP神经网络算法建立驾驶员转向特性辨识模型,对模型辨识准确度进行离线验证,并基于辨识模型设计在线辨识方法。实验结果表明:研究方法能够实现对驾驶员转向特性的合理分类和在线准确辨识。     

基于回波模拟器的CFOSAT散射计校飞模式定标研究

航空校飞是中法海洋卫星(Chinese-French Oceanic SATellite,CFOSAT)散射计发射前需要完成的一项重要实验内容,它可以检验星载散射计的各项功能和性能,获取有效数据,是保障散射计在轨正常工作的重要环节。在本次校飞实验中,利用了回波模拟器对散射计进行地面系统测试及定标验证,探索了一种利用回波模拟器对星载散射计进行系统测试定标的方法。运用该方法对CFOSAT星载散射计进行全系统地面测试以及定标实验。回波模拟器提供给散射计标准的、已知的回波信号,散射计处理该信号后,获取系统参数并得到定标常数。校飞的实验结果验证回波模拟器对星载散射计地面测试和定标方法的可行性和准确性。     

飞行模拟器虚拟仪表设计

阐述某型飞机飞行模拟器仪表仿真系统的设计方案,给出在Visual C++6.0下基于OpenGL的虚拟仪表的绘制方法。实践证明,基于OpenGL的虚拟仪表建模形象逼真,代码的可重用性好、效率高、扩展性强,在通用性和模块化方面具有良好的特性。     

计算机防真技术应用于飞行模拟器的特点和发展趋势

分析了飞行模拟器的概念,提出了计算机防真技术在应用于飞行模拟器中体现出的技术特点,并根据这些特点引出计算机防真技术在飞行模拟器大规模运用及发展趋势.     

多模卫星信号仿真器的软件设计

本文以多模卫星信号仿真器的研制为背景,对GPS/GLONASS/BD三模仿真器上位机软件设计进行了详细的说明,介绍了仿真器软件开发的总体方案和关键模块,重点对用户界面的设计、上位机与下位机之间的数据通信、多线程的使用进行了详细论述。最后通过实际硬件平台和商用接收机对仿真器进行实验了验证。结果表明,该仿真器产生出的三个导航系统的卫星信号能够被接收机正确接收,验证了仿真器软件的正确性和实用性。     

卫星信号模拟器CBOC中频信号设计与实现

GNSS卫星信号模拟器对于GNSS系统及用户接收机的研究和设计起着非常重要的作用。本文主要研究针对Galileo系统E1频点CBOC中频信号的产生方法及数字处理技术,在基于PCIE+DSP+FPGA+DAC架构的中频板卡上完成了与PC上位机通信、波形控制参数计算和更新、副载波生成、基带信号调制以及模拟中频信号的产生;最后给出了频谱、相关峰、定位误差等测量结果,验证了信号的质量和正确性。