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271.
TD-SCDMA直放站对网络性能的影响 总被引:1,自引:0,他引:1
TD-SCDMA直放站是用于TD-SCDMA移动通信网的全双工、线性射频放大设备.介绍了TD直放站不同于其它系统的同步的时分双工模式特点,并讨论了TD-SCDMA直放站的引入可能对网络性能造成的影响及其解决方法。 相似文献
272.
SIP协议在VoIP终端的设计和实现 总被引:1,自引:0,他引:1
SIP是下一代网络中的重要协议,而基于SIP协议的VoIP业务已经对传统话音业务形成了重要的威胁,并成为各大运营商竞争的重点业务之一.概述了VoIP业务的发展现状,介绍了SIP协议的实体、消息机制以及它所提供的业务,通过对SIP协议的原理及工作流程的分析,论证了其在实现一个VoIP系统中的优势,在此基础上设计并实现了一个基于SIP协议的VoIP终端. 相似文献
273.
在介绍宽带无线移动发展趋势所采用的新技术的基础上,论述了宽带无线移动通信网络优化及相关发展策略的一些问题。 相似文献
274.
论文将Fermat素性检验的思想运用于不可约多项式的判断,给出了一个对于不可约判断问题的Monte Carlo 算法,分析了该算法的计算复杂度问题,并且给出了次数在200以内的检验结果。 相似文献
275.
Quality of service (QoS) support for multimedia services in the IEEE 802.11 wireless LAN is an important issue for such WLANs
to become a viable wireless access to the Internet. In this paper, we endeavor to propose a practical scheme to achieve this
goal without changing the channel access mechanism. To this end, a novel call admission and rate control (CARC) scheme is
proposed. The key idea of this scheme is to regulate the arriving traffic of the WLAN such that the network can work at an
optimal point. We first show that the channel busyness ratio is a good indicator of the network status in the sense that it
is easy to obtain and can accurately and timely represent channel utilization. Then we propose two algorithms based on the
channel busyness ratio. The call admission control algorithm is used to regulate the admission of real-time or streaming traffic
and the rate control algorithm to control the transmission rate of best effort traffic. As a result, the real-time or streaming
traffic is supported with statistical QoS guarantees and the best effort traffic can fully utilize the residual channel capacity
left by the real-time and streaming traffic. In addition, the rate control algorithm itself provides a solution that could
be used above the media access mechanism to approach the maximal theoretical channel utilization. A comprehensive simulation
study in ns-2 has verified the performance of our proposed CARC scheme, showing that the original 802.11 DCF protocol can
statically support strict QoS requirements, such as those required by voice over IP or streaming video, and at the same time,
achieve a high channel utilization.
Hongqiang Zhai received the B.E. and M.E. degrees in electrical engineering from Tsinghua University, Beijing, China, in July 1999 and January
2002 respectively. He worked as a research intern in Bell Labs Research China from June 2001 to December 2001, and in Microsoft
Research Asia from January 2002 to July 2002. Currently he is pursuing the PhD degree in the Department of Electrical and
Computer Engineering, University of Florida. He is a student member of IEEE.
Xiang Chen received the B.E. and M.E. degrees in electrical engineering from Shanghai Jiao Tong University, Shanghai, China, in 1997
and 2000, respectively, and the Ph.D. degree in electrical and computer engineering from the University of Florida, Gainesville,
in 2005. He is currently a Senior Research Engineer at Motorola Labs, Arlington Heights, IL. His research interests include
resource management, medium access control, and quality of service (QoS) in wireless networks. He is a Member of Tau Beta
Pi and a student member of IEEE.
Yuguang Fang received a Ph.D degree in Systems and Control Engineering from Case Western Reserve University in January 1994, and a Ph.D
degree in Electrical Engineering from Boston University in May 1997.
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. In May 2000, he joined the Department of Electrical and Computer Engineering
at University of Florida where he got the early promotion with tenure in August 2003 and has been an Associate Professor since
then. He has published over one hundred (100) papers in refereed professional journals and conferences. He received the National
Science Foundation Faculty Early Career Award in 2001 and the Office of Naval Research Young Investigator Award in 2002.
He is currently serving as an Editor for many journals including IEEE Transactions on Communications, IEEE Transactions on
Wireless Communications, IEEE Transactions on Mobile Computing, and ACM Wireless Networks. He is also actively participating
in conference organization such as the Program Vice-Chair for IEEE INFOCOM’2005, Program Co-Chair for the Global Internet
and Next Generation Networks Symposium in IEEE Globecom’2004 and the Program Vice Chair for 2000 IEEE Wireless Communications
and Networking Conference (WCNC’2000). 相似文献
276.
Chun-Tsen Lu Kun-Wei Lin Huey-Ing Chen Hung-Ming Chuang Chun-Yuan Chen Wen-Chau Liu 《Electron Device Letters, IEEE》2003,24(6):390-392
A new and interesting Pd-oxide-Al/sub 0.3/Ga/sub 0.7/As MOS hydrogen sensor has been fabricated and studied. The steady-state and transient responses with different hydrogen concentrations has been measured at various temperatures. Based on the large Schottky barrier height and presence of oxide layer, the studied device exhibits a high hydrogen detection sensitivity and wide temperature operating regime. The studied device exhibits the low-leakage current and obvious current changes when exposed to hydrogen-contained gas. Even at room temperature, a very high hydrogen detection sensitivity of 155.9 is obtained when a 9090 ppm H/sub 2//air gas is introduced. Furthermore, when exposed to hydrogen-contained gas at 95/spl deg/C, both the forward and reverse currents are substantially increased with increased hydrogen concentration. In other words, the studied device can be used as a hydrogen sensor under the applied bidirectional bias. Under the applied voltage of 0.35 V and 9090 ppm H/sub 2//air hydrogen ambient, a fast adsorption response time about 10 s is found. The transient and steady-state characteristics of hydrogen adsorption are also investigated. 相似文献
277.
278.
Effect of doping of carbon nanotubes by magnetic transition metal atoms has been considered in this paper. In the case of
semiconducting tubes, it was found that the system has zero magnetization, whereas in metallic tubes the valence electrons
of the tube screen the magnetization of the dopants: the coupling to the tube is usually antiferromagnetic (except for Cr). 相似文献
279.
280.
Thermal barrier coatings (TBC) are widely used to prevent transient high temperature attack and allow components high durability. Due to strong inhomogeneous material properties the TBC failure often initiates near the interface between the brittle oxide layer and the ductile substrate. A reliable prediction of the TBC failure requires detailed information about the crack tip field and the consequent fracture criteria. In the present paper both cohesive model and gradient plasticity are used to simulate the failure process and to study interdependence of the interface stress distribution with the specific fracture energies. Computations confirm that combination of the two models is able to simulate different failure mechanisms in the TBC system. The computational model has the potential to give a realistic prediction of the crack propagation process. 相似文献