基于三值系统的数字相位调制

介绍一种新的应用于三值系统的九相相移键控信号,并讨论了实现三值数字相位调制的一种方法,为用于三值ＣＤＭＡ通信新体制打下了必要的基础。     

一种基于带通RAKE接收机的多载波解调方法

ＣＤＭＡ２０００采用多载波和直接序列扩频两种方式来达到提供宽带数据业务的目的。针对ＣＤＭＡ２０００前向信道的三载波调制方式,提出了一种基于带通ＲＡＫＥ接收机的多载波解调方法。这种方法避开了设计多比特的基带数字滤波器,从而大大降低了实现的复杂度。文章首先分析了三载波的调制结构。根据ＲＡＫＥ接收机的原理,推导出相应的带通ＲＡＫＥ接收机模型并给出解调结构,最后,用ＳＰＷ软件对此模型进行仿真并给出了传真结     

GSM向第三代移动通信系统的平滑演进

探讨了 GSM的最新发展方向 ,分析了由第二代移动通信系统向第三代系统平滑演进的可能性和有效途径。     

三种多址蜂窝系统的容量及性能分析

从理论上推导了 FDMA、TDMA、CDMA制式的容量表达式 ,计算了 3种典型系统 AMPS、GSM和 Q- CDMA的容量关系 ,分析比较不同系统的通信性能 ,指出了移动通信系统的发展趋势     

基于AutoCAD 2000栅格地形图编辑系统的开发

对在AutoCAD 2 0 0 0平台上 ,采用ObjectARX开发工具 ,实现栅格图形数据的访问、栅格坐标与绘图坐标的转换及矢量图形向栅格图形的转换等问题进行了讨论 ,并介绍了栅格地形图基本编辑功能的编程方法。     

High Efficiency Al-Free 980nm InGaAs/InGaAsP/InGaP Strained Quantum Well Lasers

High efficiency Al-free InGaAs/InGaAsP/InGaP lasers emitting at 980nm are fabricated by MOCVD. The lasers exhibit a high internal quantum efficiency of 95 % and a low internal loss of 1.8 cm-1. Low threshold current density of 190A/cm2 and high slope efficiency of 1.06W/A are obtained by lasers with 800μm cavitylength. A high characteristic temperature 210C is also obtained by replacing the GaAs barrier with high-bandgap InGaAsP barrier. The measured vertical and parallel divergence angle are 40° and 8°, respectively.     

Performance analysis of the forward link cdma2000 1xEV‐DO evolution for multirate services in cellular wireless system

In this paper, we propose a combined analytical and simulation framework for performance evaluation of the forward link in the cdma2000 evolution for data only (1xEV‐DO) cellular systems with throughput and spectral efficiency being used as performance metrics. A closed form expression for the aggregate average throughput is derived in terms of system‐dependent parameters and a discrete random process that reflects the stochastic behavior of the transmission channel. The random process is expressed in terms of the cumulative distribution function (CDF) of the users signal‐to‐interference‐plus‐noise ratio (SINR). Quantitative results for throughput and spectral efficiency are presented for a variety of users distribution models, base station antenna types and frequency reuse factors for the cases of sectorized and non‐sectorized cells. Furthermore, we study the impact of the cell radius on the system performance. Copyright © 2006 John Wiley & Sons, Ltd.     

Recombinant Landscapes in the American City

How are urban actors, such as landscape designers, community groups, developers and local politicians, actively restructuring their environments to meet the challenges of the American city in the new global context? Grahame Shane outlines the approaches to landscape that have been emerging since the mid-20th century and are set to recombine urban assemblages whether they are located in historic city centres, postindustrial waterfronts or suburban sprawl. Copyright © 2007 John Wiley & Sons, Ltd.     

3+1 architects

Without the predominance of a single presiding tradition of modern architecture in Estonia, the way has been clear for a younger generation of architects to make their mark. Andres Kurg describes the work of 3+1 architects, who launched their career in the mid-1990s with an Estonian Embassy in Vilnius, Lithuania. Through their trend-setting domestic work, they have proved able to appeal to a new wealthy client base, while also developing their own interests in programme and architecture's relationship to the physical landscape. Copyright © 2007 John Wiley & Sons, Ltd.     

冷静看待TD-SCDMA的发展

随着3G牌照的发放,3G技术和业务再次成为业界关注的热点。作为我国自主知识产权的3G标准,TD-SCDMA(以下简称TD)对于我国电信业增强自主创新能力,实现产业结构升级,拉动国内经济发展其意义十分重大。通过重点对TD特点及发展优、劣势等方面的介绍分析,以期让读者对TD更清晰的认识,也希望能对TD的完善和应用起到一定的推动作用。