本书是无线通信课程的权威教材,面向那些已经熟悉诸如概率论、通信原理和基本电磁学等技术概念的学生和工程师。全书深入浅出地讨论了无线通信技术与系统设计方面的内容,包括无线网络涉及的所有基本问题,特别是3G系统和无线局域网的问题,并对无线网络技术新进展和全球主要的无线通信标准给出了论述。全书共分11章,集中讲述了蜂窝的概念、移动无线电传播、调制技术、多址技术以及无线系统与标准,结合理论对无线通信系统的各个方面做了精辟论述和统计分析。

1 Introduction to Wireless Communication Systems
1.1 Evolution of Mobile Radio Communications
1.2 Mobile Radiotelephony in the U.S.
1.3 Mobile Radio Systems Around the World
1.4 Examples of Wireless Communication Systems
1.4.1 Paging Systems
1.4.2 Cordless Telephone Systems
1.4.3 Cellular Telephone Systems
1.4.3.1 How a Cellular Telephone Call is Made
1.4.4 Comparison of Common Wireless Communication Systems
1.5 Trends in Cellular Radio and Personal Communications
1.6 Problems
2 Modern Wireless Communication Systems
2.1 Second Generation (2G) Cellular Networks
2.1.1 Evolution to 2.5G Wireless Networks
2.1.2 Evolution for 2.5G TDMA Standards
2.1.2.1 HSCSD for 2.5G GSM
2.1.2.2 GPRS for 2.5G GSM and IS-136
2.1.2.3 EDGE for 2.5G GSM and IS-136
2.1.3 IS-95B for 2.5G CDMA
2.2 Third Generation (3G) Wireless Networks
2.2.1 3G W-CDMA (UMTS)
2.2.2 3G cdma2000
2.2.3 3G TD-SCDMA
2.3 Wireless Local Loop (WLL) and LMDS
2.4 Wireless Local Area Networks (WLANs)
2.5 Bluetooth and Personal Area Networks (PANs)
2.6 Summary
2.7 Problems
3 The Cellular Concept-System Design Fundamentals
3.1 Introduction
3.2 Frequency Reuse
3.3 Channel Assignment Strategies
3.4 HandoffStrategies
3.4.1 Prioritizing Handoffs
3.4.2 Practical HandoffConsiderations
3.5 Interference and System Capacity
3.5.1 Co-channel Interference and System Capacity
3.5.2 Channel Planning for Wireless Systems
3.5.3 Adjacent Channel Interference
3.5.4 Power Control for Reducing Interference
3.6 Trunking and Grade of Service
3.7 Improving Coverage & Capacity in Cellular Systems
3.7.1 Cell Splitting
3.7.2 Sectoring
3.7.3 Repeaters for Range Extension
3.7.4 A Microcell Zone Concept
3.8 Summary
3.9 Problems
4 Mobile Radio Propagation: Large-Scale Path Loss
4.1 Introduction to Radio Wave Propagation
4.2 Free Space Propagation Model
4.3 Relating Power to Electric Field
4.4 The Three Basic Propagation Mechanisms
4.5 Reflection
4.5.1 Reflection from Dielectrics
4.5.2 Brewster Angle
4.5.3 Reflection from Perfect Conductors
4.6 Ground Reflection (Two-R'ay)Model
4.7 Diffraction
4.7.1 Fresnel Zone Geometry
4.7.2 Knife-edge Diffraction Model
4.7.3 Multiple Knife:edge Diffraction
4.8 Scattering
4.8.1 Radar Cross Section Model
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5 Mobile Radio Propagation: Small-Scale Fading and Multipatipath
6 Modulation Techniques for Mobile Radio
7 Equalization, Diversity, and Channel Coding
8 Speech Coding
9 Multiple Access Techiques for Wireless Communications
10 Wireless Networking
11 Wireless Systems and Standeads
APPENDICES
INDEX

第1章 机电控制系统的基本概念
1.1 自动控制系统
1.1.1 控制的基本概念
控制已相当广泛地应用在各行各业,如温度控制、微机控制、人口控制等。所谓控制,其定义是“为达到某种目的,对某一对象施加所需的操作”,含有“调节、调整”,“管理、监督”,“运用、操作”等意思。
在上述定义中所说的对象,是指物体、机器、过程或经济、社会现象等一般广泛的系统,叫做被控对象。对于想实现控制的目标量,比如电动机的转速、储水容量水位、油压缸中活塞的位置、炉内温度等叫做控制量,而把所希望的转速、水位、位置、温度等叫做目标值或参据量。
根据产生控制作用的主体的不同,控制可分为手动控制和自动控制。由人本身通过判断和操作进行的控制叫做手动控制。例如汽车的驾驶,司机为到达目的地,需要根据路况和车况不断地操纵转向盘;又如人的行走、抓放物品等行为也都可称为手动控制。
所谓自动控制,是指在没有人直接参与的情况下,利用外加的设备或装置(称控制装置或控制器),使机器、设备或生产过程的某个工作状态或参数自动地按照预定的规律运行。
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