RTD/HEMT串联型共振隧穿三极管的设计与研制

对RTD/HEMT串联型共振隧穿三极管进行了设计和研制.测量结果表明:最大电流峰谷比为17.6∶1,棚压对峰值电压调控能力在1.5～7.7范围内,-3dB截止频率为4GHz,此种器件可与HEMT在结构和工艺上兼容,可应用于HEMT高速电路.     

对一种基于双重到达时间差的无线定位数据融合方法的探讨

介绍了几种常见的无线网络定位方法．针对无线自组（AdHoc）网络的特点，提出了一种改进的双重到达时间差DTDOA的定位数据融合方法。该方法利用在同一监测基站上两次测量值的差值再与其他基站的测量差值求差，可以有效地消除无线网络节点定位时所要求的时钟同步问题。     

基于TDM/TDMA的EPON、GPON系统测距与时延补偿机制分析

基于TDM/TDMA的PON系统若不通过统一的管理控制会产生上行数据冲突,为解决上行数据冲突,测距技术是PON系统的关键技术。文章介绍了测距技术的原理和分类,详细分析了目前EPON和GPON系统所采用的测距原理、时延补偿机制及具体的实现过程。最后,提出PON系统测距中有关冲突避免算法还有待进一步的研究,需要继续跟踪研究。     

Queue length‐based load balancing in data center networks

Traffic load balancing in data centers is an important requirement. Traffic dynamics and possibilities of changes in the topology (e.g., failures and asymmetries) make load balancing a challenging task. Existing end‐host–based schemes either employ the predominantly used ECN or combine it with RTT to get congestion information of paths. Both congestion signals, ECN and RTT, have limitations; ECN only tells whether the queue length is above or below a threshold value but does not inform about the extent of congestion; similarly, RTT in data center networks is on the scale of up to few hundreds of microseconds, and current data center operating systems lack fine‐grained microsecond‐level timers. Therefore, there is a need of a new congestion signal which should give accurate information of congestion along the path. Furthermore, in end‐host–based schemes, detecting asymmetries in the topology is challenging due to the inability to accurately measure RTT on the scale of microseconds. This paper presents QLLB, an end‐host–based, queue length–based load balancing scheme. QLLB employs a new queue length–based congestion signal that gives an exact measure of congestion along the paths. Furthermore, QLLB uses relative‐RTT to detect asymmetries in the topology. QLLB is implemented in ns‐3 and compared with ECMP, CONGA, and Hermes. The results show that QLLB significantly improves performance of short flows over the other schemes and performs within acceptable level, of CONGA and Hermes, for long flows. In addition, QLLB effectively detects asymmetric paths and performs better than Hermes under high loads.     

基于同步码分多址技术的第三代移动通信系统

中国的第三代移动通信系统（ＴＤ－ＳＣＤＭＡ）是基于同步码多址技术（ＳＣＤＭＡ）的未来陆地通信系统,它广泛采用了智能天线和软件无线电技术,工作于ＩＤＤ方式,系统向下兼容在中国有广大基础的第二代ＧＳＭ网络,同时支持电路交换和分组数据交换业务。ＴＤ－ＳＣＤＭＡ相对于第二代移动通信和其他的第三代移动通信建议,有更好的频谱利用率,并且支持更为精确的接力切换概念和系统切换的概念,未来的系统将工作于ＩＴＵ为ＩＭ     

Software‐only TDOA/RTT positioning for 3G WCDMA wireless network

A hybrid location finding technique based on time difference of arrival (TDOA) with round‐trip time (RTT) measurements is proposed for a wideband code division multiple access (WCDMA) network. In this technique, a mobile station measures timing from at least three base stations using user equipment receive—transmit (UE Rx—Tx) time difference and at least three base stations measure timing from the mobile station using RTT. The timing measurements of mobile and base stations are then combined to solve for both the location of the mobile and the synchronization offset between base stations. A software‐only geolocation system based on the above mobile/base stations timing measurements is implemented in Matlab platform and the performance of the system is investigated using large‐scale propagation models. Copyright © 2007 John Wiley & Sons, Ltd.     

IMT2000中的无线传输技术

在比较各种RTT特点的基础上,结合我国移动通信发展的需求,从国家、运营商、民族通信制造技术和广大用户的利益出发,提出了对我国第三代移动通信发展的看法：首先发展和使用基于我国提出的TD－SCDMA RTT建议所形成的CDMA TDD技术和产品,在大中城市内,提供基于GSM核心网的第三代移动通信服务。然后,再考虑建设全IP核心网和使用FDD技术及系统的问题。     

第三代移动通信系统的演进趋势

本文根据世界各国向ITU提交的无线传输技术(RTT)方案 ,讨论了向第三代移动通信系统演进的趋势。     

TD-SCDMA无线传输技术

我国提出的TD SCDMA无线传输技术 (RTT)建议已成为ITUIMT RSPC(TG8/1输出文件 )的一个组成部分 ,并将实现CDMATDD标准的集成 ,开发IS 41核心网的接口 ,形成统一的TDD国际标准。文章对该标准和建议作简单介绍 ,着重讨论采用TD SCDMA的必要性和该技术的竞争力     

RTT relation and long-range spin chain model

It is verified that the long-range interaction integrable chain models with Yangian symmetry can be obtained from RTT relation, which therefore make this kind of models merge into Yang-Baxter system. A general method for obtaining Hamiltonian from quantum determinant of transfer matrix satisfying RTT relation is given. Project supported by the National Natural Science Foundation of China.