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51.
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. 相似文献
52.
通过对TFM调制技术的研究,修正了其中预调制滤波器冲击响应波形g(f)在时间轴上的位置及其频谱G(w)的表达式.然后将TFM基带信号进行近似,即对TFM的相位路径进行进一步的控制,得到一个改进的TFM调制技术.改进后的TFM调制技术和原TFM调制技术相比,频带压缩能力提高了一倍,误码性能不变,但会出现3 dB的寄生调幅,需要提高发射机的发射功率. 相似文献
53.
在组合系统运用Kalman滤波器技术时,准确的系统模型和可靠的观测数据是保证其性能的重要因素,否则将大大降低Kalman滤波器的估计精度,甚至导致滤波器发散.为解决上述Kalman应用中的实际问题,提出了一种新颖的基于进化人工神经网络技术的自适应Kalman滤波器.仿真试验表明该算法可以在系统模型不准确时、甚至外部观测数据短暂中断时,仍能保证Kalman滤波器的性能. 相似文献
54.
有限冲激响应(FIR)滤波器设计遇到的难题是滤波要进行大量乘法运算,即使是在全定制的专用集成电路中也会导致过大的面积与功耗.对于用硬件实现系数是常量的专用滤波器,可以通过分解系数变为应用加、减和移位而实现乘法.FIR滤波器的复杂性主要由用于系数乘法的加法器/减法器的数量决定.而对于自适应FIR滤波器,大多数场合下可用数字信号处理器(DSP)或CPU通过软件编程的方法来实现,但是对于要求高速运算的场合,VLSI实现是很好的选择.基于这一考虑,可以用符号数的正则表示(CSD)码表示系数, 再利用可重构现场可编程门阵列(FPGA)技术实现.可重构结构的应用,能保证系统的其余部分同时处于运行状态时实现FIR滤波器系数的更新.文中利用CSD码和可重构思想,提出了用FPGA实现自适应FIR滤波器的一种方案. 相似文献
55.
相对于传统的数字滤波器实现方法,符号的2次幂和(SPT)滤波器用移位寄存器替代乘法器,因而资源消耗少、速度快,更加适于专用集成电路(ASIC)设计.介绍了一种适用于宽带码分多址(WCDMA)前向信道中给定基带成形滤波器单位脉冲响应后设计SPT滤波器的方法.相对于传统的理想SPT系数优化方法,此方法更适于给定单位脉冲响应后SPT滤波器的设计,计算复杂度低;仿真结果显示,相对于更加简单的四舍五入方法,此算法在性能上又有可观的增益. 相似文献
56.
57.
用Tow-Thomas电路设计含有限非零传输零点有源滤波器的方法 总被引:4,自引:1,他引:3
Tow-Thomas电路是一种实现全极点滤波器的典型电路。本文给出了用Tow-Thoms电路设计含有限非零传输零点有源滤波器的方法,从而使Tow-Thomas电路可用于单片集成滤波器电路。而文中给出的公式可用于计算外接元件。设计实例表明了文中给出的计算公式的正确性。 相似文献
58.
根据耦合非线性薛定谔方程 ,本文研究了偏振模色散如何影响各种码型的频谱 ,分析了滑频滤波器和固定滤波器对偏振模色散的补偿作用。研究结果表明 :偏振模色散对不同码型的频谱影响是不一样的 ,对色散管理孤子的频谱影响最大 ,产生新的频率分量也最多 ,而且每个新频率分量都较强 ,比入射频谱展宽许多 ;滑频滤波器和固定滤波器对偏振模色散都具有补偿作用 ,使最大可传输距离成倍增加 ,两种滤波器对偏振模色散的补偿作用相差较小 ;但是对色散管理孤子系统中的偏振模色散补偿效果最佳。 相似文献
59.
Jocelyn Sabatier Serge Poullain Patrick Latteux Jean Luc Thomas Alain Oustaloup 《Nonlinear dynamics》2004,38(1-2):383-400
Robust speed control of a low damped electromechanical system with backlash is studied, controlled load angular speed being not measured. The proposed control strategy combines a Luenberger observer (load angular speed and load torque disturbance estimations) and a robust CRONE controller. The observer provides estimation of the load angular speed and of the disturbance torque applied on the load. Through the computation of only three independent parameters (as many as a PID controller), the CRONE controller permits to ensure the robust speed control of the load in spite of plant parametric variations and speed observation errors. The proposed control strategy is applied to a four mass experimental test bench. 相似文献
60.
Karl Gruber Christoph Kratky 《Journal of polymer science. Part A, Polymer chemistry》2004,42(3):479-486
Hydroxynitrile lyases catalyze the reversible cleavage of α-cyanohydrins to yield hydrocyanic acid and the corresponding aldehyde or ketone. Besides its biological interest, this class of enzymes is also of relevance in industrial biocatalysis for the enantioselective condensation of HCN with a variety of aldehydes and ketones. Several distinctly different types of hydroxynitrile lyases (HNLs) are known, which must have originated through convergent evolution from different ancestral proteins. Three-dimensional structural data are known for three classes of hydroxynitrile lyases. Insights into the reaction mechanisms emerged from a combination of structural, enzyme kinetic, spectroscopic, and molecular modeling data. For all three types of HNLs, mechanisms involving acid–base catalysis were proposed. In members belonging to the α,β-hydrolase type, the amino acid residues of the catalytic triad presumably act as general acid/base, whereas for flavine adenine dinucleotide (FAD)-dependent HNLs a single histidine residue fulfills this function. In the third type of HNL—which is related to carboxypeptidase—acid–base catalysis involves the carboxylate of the C-terminal residue. The catalytic relevance of a positive electrostatic potential in the active site was suggested in some of the mechanistic proposals. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 479–486, 2004 相似文献