Training Material for CDMA Mobile Communication System

CDMA&

Training Material For

ZXC10 CDMA Cellular Mobile Communication System

ZTE Corporation

February 2003

Preface

The global mobile communications market is booming. There are about 250 million users worldwide and should be nearly l billion by early next century. Code Division Multiple Access (CDMA) is the fastest-growing digital wireless technology, tripling its worldwide subscriber base between 1997 and 1998. There are already 30 million CDMA customers and, at the current growth rate, there will be 50 million by the millennium. The major markets for CDMA are North America, Latin America, and Asia (particularly China, Japan and Korea). In total, CDMA has been adopted by almost 50 countries around the world.

It is not hard to see the reasons for the success of CDMA. CDMA is m advanced digital technology that can offer about 7 to 10 times the capacity of analog technologies and up to 6 times the capacity of digita1 technologies such as Time Division Multiple Access (TDMA). The speech quality provided by CDMA systems is far superior to any other digital cellular technology, particularly in difficult radio environments such as dense urban areas and mountainous regions. In both initial deployment and long-term operation, CDMA provides the most cost-effective solution for cellular operators. After an 18-month of market rollout, Personal Communications Services (PCS) providers have adequately demonstrated the power of CDMA technology to support a marketing strategy based on low prices and superior performance in key areas such as voice quality, system reliability, and handset battery life.

CDMA service providers have a strong advantage when pursuing the market to the minutes- of-use model, given the longevity of CDMA handset battery life and the higher quality of the voice signal. A recent analysis of wireless platform performance by the Telecommunications Research and Action Center (TRAC) found that CDMA outperformed other digital and analog technologies on every front, including signal quality, security, power consumption, and reliabi1ity. Although analog technology came out ahead in availability, all three digital services (GSM, IS-136 TDMA, and IS-95 CDMA) were rated equally over analog with respect to availability of enhanced service features. The TRAC study found CDMA to be superior in signal security and voice quality over the other digital air interface standards. According to TRAC, CDMA has several advantages for consumers. Lower power consumption enables CDMA handsets to support up to 4 hours of talk time or 48 hours of standby time on a single battery charge. It has also been found that the soft-handoff characteristics of CDMA lead to fewer dropped calls than with GSM and IS- 136 TDMA. One possible drawback for some CDMA customers is that there are some limitations on roaming capabilities. Some PCS operators with cellular affiliates are supporting dual-mode handsets to allow roaming between CDMA and analog platforms.

The CDMA technology is constantly evolving to offer customers new, advanced services. The mobile data speeds offered through CDMA phones are increasing, and new voice codecs provide speech quality close to wireline. Internet access is now available through CDMA terminals. The time will soon be at hand when CDMA service providers can further exploit the enhanced service potential of their platforms. There has ken much talk of so-called third generation (3G) data capabilities, where PCS providers will be able to compete with wireline service providers at high access speeds. PCS providers are looking ahead toward providing a range of service categories such as Internet and intranet access, multimedia applications, high-speed business transactions, and telemetry. The CDMA network offers operators a smooth evolutionary path to 3G mobile systems.

The opportunity to use the CDMA platform to add a fixed wireless service feature represents an added advantage for operators. Because CDMA has ample spectrum to provide a fixed service on top of mobile, several operators are exploring using terminals that would be able to shift the handset between fixed and mobile service, depending on where the user is. The universal handset would serve as a cordless phone in the home and as a mobile handset outside the home. The evolution to 3G will open the wireless local loop (WLL) with Public Switched Telephone Network (PSTN) and Public Data Network (PDN) access, while providing more convenient control of applications and network resources. It will also open the door to convenient global roaming, service portability, zone-based ID and billing, and global directory access. The 3G technology is even expected to support seamless satellite interworking.

CDMA is the selected approach for the 3G system, as evidenced by the proposals submitted by the European Telecommunications Standards Institute (ETSI). The Association Radio Industry Business (ARIB), and the Telecommunications Industry Association (TIA). The 3G cdma200O uses a CDMA air interface based on the existing IS-95B standard to provide wireline-quality voice service and high-speed data services, ranging from 144 kbps for mobile users to 2 megabits per second (Mbps) for stationary users. It is important to note that cdma2000 is a core proposal of the TIA for International Mobile Telecommunications-2000 (IMT-2000). This book can be divided into three parts: Chapters 1 through 7 provide a foundation for understanding the material in subsequent chapters. Chapters 8 through 21 deal with mainly the products and solutions of ZTE CDMA, including the products at the radio side, at the switching side, and the layered network management center ZXCOMC. It also introduces the services, network planning and network optimization of ZTE cdma2000 1x. Chapters 22 and 23 mainly describe the typical configuration and networking modes of BTS system on the basis of ZTE products. It finally analyzes the typical cases of the application of ZTE products in WLL and cdma2000 1x, including deep coverage and wide coverage.

Chapter 1. A comprehensive knowledge concerning the development of the wireless communications, the development trend of mobile communication systems, and ZTEs research and development.

Chapter 2. Basic working principles of CDMA, including basic principle of Spread spectrum communication and some basic concepts of CDMA, and the characteristics of mobile channels.Chapter 3. A general idea of IS-95 System, including a general description of the forward / reserve channels and air interface standards.

Chapter 4. The working principle of the wireless part of cdma2000 1xRTT and its circuit domain and packet domain.Chapter 5. Some basic principles and development about 3G, centering on cdma2000 1x EV-DO. Chapter 6. The smooth evolution scheme from ZTE cdma2000 BSS side to the all-IP, the hardware composition and typical configurations of the all-IP cdma2000 BS and the performance features of ZTE all-IP scheme.

Chapter 7. The key techniques and advantages of the CDMA system.

Chapter 8. The network structure and its interfaces of the CDMA cellular mobile communication system, and the corresponding technical standards of the system, the technical indexes, software and hardware system structures he networking and configuration modes of ZTE ZXC10MSC/VLR/SSP, and its services and functions.Chapter 9. ZXC10-HLR/AUC (V3.0)

Chapter 10. CDMA Short Message Center (ZXSC100)

Chapter 11. The software and hardware structure and function of the ZXC10-BSS, including the external interfaces of the system, the overall structure and technical indices of the system, the software structure of the system, and the networking mode and system configuration.Chapter 12. The technical indexes, hardware architecture, product characteristics and networking modes & configuration of ZXCBTS M800 and ZXCBTS M190 systems.

Chapter 13. The technical indexes, hardware architecture, product characteristics and networking modes & configuration of ZXCBTS R800 and ZXCBTS R190 systems.Chapter 14. Technical indexes, hardware architecture, product characteristics and networking modes and configuration of ZXRPT-C800 system.Chapter 15. The technical indexes, hardware architecture, product characteristics and networking configuration mode of ZXICS C800 and ZXICS C801 systems.Chapter 16. The wide and deep coverage solutions of ZTEs CDMA system.Chapter 17. A description of the ZTE CDMA-WLL solution.Chapter 18. ZXPDSS Packet Switching SystemChapter 19. A description of the protocols, the standards, the technical specifications, the system architecture and the networking configuration modes of the ZTE hierarchic centralized network management center (ZXCOMC).Chapter 20. ZTE cdma2000 1x Services.

Chapter 21. ZTE Network Planning and Optimization Solution.

Chapter 22. Typical WLL networking and configuration with reference to ZXC10-BSS (V5.0) and then gives typical examples. Chapter 23. Networking Configuration Analysis with typical cdma2000 1x Cases.

Appendix A comprises a list of abbreviations.

Appendix B FAQ.

contents1Chapter 1Why CDMA?

1Introduction

11.1Development of Mobile Communications and Brief History of CDMA

11.1.1The First-generation Mobile Communication System

21.1.2The Second-generation (2G) Mobile Communications System

41.1.3Basic Concept of CDMA

51.2Evolution of CDMA Standards and the Third Generation (3G) Mobile Communications

51.2.1Evolution of the CDMA Standards

71.2.2Why the 3G Demanded

91.2.3Key Technical Features of cdma2000 1X

101.3Analysis and Prospect of CDMA Market

101.3.1Overview

121.3.2General Introduction to the ZTE Products

14Exercise

15Chapter 2Principles of the CDMA System

15Introduction

152.1Overview

162.2Basic Concepts of the CDMA System

182.3Features of the CDMA Cellular Mobile Communication Network

192.4Principles of Spread Spectrum Communication

192.4.1Brief Introduction

202.4.2Basic Principles of the Spread Spectrum Technique

222.5Walsh Code, m Sequence and M Sequence

242.6Properties of Mobile Channels

242.6.1Properties of Mobile Communication

272.6.2Convolutional Coding

272.6.3Block Interleaving Technique

282.7Brief Introduction to Speech Coding Technique

30Exercise

31Chapter 3IS-95 System Principles

31Introduction

313.1IS-95 System Overview

333.2Air Interface Standards of IS-95 System

343.3Signal Design of Forward Links

373.4Signal Design of the Reverse Link

39Exercise

41Chapter 4Principles of cdma2000 1x RTT

41Introduction

414.1Enhancement of cdma2000 1xRTT Performance

434.2Spreading Rate and Radio Configuration

444.3Types and Structures of the Channels

484.3.1Cdma2000 Turbo Encoder

494.3.2Quasi Orthogonal Function

514.3.3Orthogonal Transmit Diversity

524.3.4HPSK Modulation

524.3.5Creation of the 1xRTT Forward Channel

554.3.6Cdma2000 1xRTT Reverse Channels

574.3.7Structure of the CDMA Cellular Mobile Communications System at the Radio Side

584.3.8Basic Call Procedure

614.4Working Principle of the cdma2000 1xRTT Circuit-Switching Domain

614.4.1Architecture of the Circuit-Switching Domain of the CDMA Cellular Mobile Communications System

634.4.2Descriptions of Network Entities

664.4.3Workflow

774.5Operation Mechanism of the cdma2000 1x Packet Domain

774.5.1Position of PDSS in the Network

784.5.2Major Functions of the Network Entities of the PDSS System

794.5.3Protocol Requirements

854.5.4Service Requirements

864.5.5Flow of Communication

96Exercise

97Chapter 5Evolution of cdma2000 1x EV and ZTE HRPD Solution

97Introduction

975.1Evolution of cdma2000 Radio-Side Standards

975.1.13G Mobile Communications

1005.1.2General Description about the Development of cdma2000 Radio-Side Standards

1025.1.3cdma2000 1xEV-DO Standard

1085.1.4Brief Description of the cdma2000 1xEV-DV

1115.2Evolution from ZTE CDMA to 1x EV

113Exercise

115Chapter 6Evolution of cdma2000 BS-Side and ZTE All-IP Solution

115Introduction

1176.1Smooth Evolution of ZTE cdma2000 All-IP BSS Side

1196.2Network Framework and Hardware Composition of ZTE All-IP cdma2000

1196.2.1All-IP BSC

1256.2.2All-IP BTS

1276.2.3All-IP cdma2000 System Networking

1296.2.4Introduction to Typical Configuration

1366.2.5Characteristics of ZTE Communications All-IP

141Exercises

143Chapter 7Key Techniques and Advantages of CDMA

143Introduction

1437.1Overview of the Key Techniques

1437.1.1Power Control

1477.1.2Diversity Reception

1527.1.3Soft Handoff

1557.2Advantages of the CDMA System

1557.2.1Unique Frequency Reuse

1567.2.2Wide Coverage

1567.2.3Large Capacity

1577.2.4High Voice Quality

1587.2.5Excellent Privacy

1587.2.6User Satisfaction

1597.2.7Economy

159Exercises

163Chapter 8ZXC10-MSC/VLR/SSP (V3.0)

163Introduction

1638.1Overview

1638.1.1Network Architecture Diagram of CDMA Cellular Mobile Communications System

1658.1.2Major Interfaces between Entities

1688.1.3Technical Standards

1718.2Technical Indices of ZXC10-MSC/VLR/SSP and Software Structure and Hardware Structure of ZXC10-MSC/VLR

1718.2.1Technical Indices

1788.2.2Rack Parameters

1798.2.3ZXC10-MSC/VLR Hardware Structure

2158.2.4Software System of ZXC10-MSC/VLR

2328.3ZXC10-SSP System Structure

2328.3.1System Overview

2338.3.2ZXC10-SSP System Structure and its Functions

2388.3.3Software Architecture of ZXC10-SSP

2418.4ZXC10-MSC/VLR/SSP Function.

2428.4.1General Functional Description

2518.4.2Mobility Management Services, Basic Call Services and Handover

2518.4.3ZXC10-MSC/VLR/SSP Related Services

2598.5ZXC10-MSC/VLR/SSP Networking and Configuration

2598.5.1Networking Mode

2618.5.2System Configuration

2668.5.3Configuration of Operation and Maintenance System (OMS)

268Exercise

269Chapter 9ZXC10-HLR/AUC (V3.0)

2699.1Overview

2699.1.1Network Architecture Diagram of the CDMA Cellular Mobile Communication System

2709.1.2Major Interfaces between Entities


2779.2ZXC10-HLR/AUC Indices

2779.2.1Technical Indices


2819.3ZXC10-HLR/AUC System Hardware Structure


2849.3.2Module Functions

2859.3.3Hardware Structure

3069.3.4Hardware reliability redundancy design

3089.4Software structure of the ZXC10-HLR/AUC

3089.4.1Software architecture

3099.4.2Operation Support Subsystem

3149.4.3SS7 subsystem

3379.4.4Service Processing Subsystem

3449.4.5Database

3479.4.6Operation & Maintenance System (OMS)

3549.4.7Redundancy Design for Software Reliability

3579.5ZXC10-HLR/AUC Service Function

3589.5.1List of Various Service Functions of HLR/AUC

3599.5.2Mobile Telecom Services

3709.5.3Supplementary services

3779.6ZXC10-HLR/AUC networking and configuration

3779.6.1CPM configuration

3799.6.2HSM configuration

3809.6.3Database configuration

3809.6.4Equipment configuration of the operation & maintenance system

382Exercise

383Chapter 10CDMA Short Message Center (ZXSC100)

38310.1Overview

38310.1.1Network Architecture of the CDMA Cellular Mobile Communications System

38410.1.2Main Interfaces Description


38610.2ZXSC100 Performance Indices

38610.2.1System Indices

38710.2.2Transmission Indices


38910.3Hardware Architecture of ZXSC100


39010.3.2Hardware Structure

41210.3.3Hardware reliability redundancy design

41510.4ZXSC100 Software Structure

41510.4.1Software System

41510.4.2Operation Support Subsystem

42110.4.3SS7 Subsystem

44210.4.4SMPP Access Module

44310.4.5Service Server

45410.4.6Database Subsystem.

45710.4.7Operation & Maintenance Subsystem

46310.4.8Cell Broadcast Short Message System

46610.4.9Characteristics of the ZXSC100 System

46810.4.10Software Reliability Design

47310.5ZXSC100 Service Functions

47410.5.1ZXSC100 Supported Services

47510.5.2Basic service functions

48210.5.3Expended service functions

48610.5.4Service processing flow

51910.6ZXSC100-GW CDMA-GSM Interworking Shared Gateway and Independent Short Message System

51910.6.1Solution for The Short Message Interworking & Shared GatewayZXSC100 Connection With Other Networks

52210.6.2ZTE Independent SMC

52610.7ZXSC100 Networking and Configuration

52710.7.1Short Message Signaling Gateway

52910.7.2Server Configurations

53110.7.3OMM

531Exercise

533Chapter 11ZXC10-BSS

533Objectives

533Introduction

53311.1Overview of the Base Station System

53311.1.1Brief Introduction to ZXC10-BSS

53511.1.2Features of ZXC10-BSS

53511.1.3Architecture and Features of Air Interface (Um Interface) Protocol

54211.1.4Architecture and Features of A Interface Protocol

55211.1.5Architecture and Features of Abis Interface Protocol

55311.2Technical Indices of BSS

55311.2.1Technical Performances of BSS

55511.2.2Work Environment

55611.3Hardware Structure of BSS

55611.3.1Overview

55811.3.2Overall Hardware Structure of the ZXC10-BSS

56011.3.3Hardware System of ZXC10-BSC

57111.3.4Hardware System of ZXC10-BTS

57911.3.5Modules/Boards

59311.3.6BSS Mechanical Properties

60211.4Architecture of BSS Software

60211.4.1Overview

60311.4.2OSS Subsystem

60611.4.3Service Processing Subsystem

62111.4.4Database Subsystem

62211.4.5OMS Subsystem

62711.5Networking Mode and Typical Configuration

62711.5.1ZXC10-BSS System Networking Modes

62911.5.2Typical System Configuration

634Exercises

636Chapter 12Micro BTS

636Objectives

636Introduction

63612.1Overview

63712.2ZXCBTS M800 Technical Specifications

63812.2.1MTRX Technical Specifications

63912.2.2MPA Technical Specifications

64012.2.3RFE Technical Specifications

64212.3ZXCBTS M190 Technical Specifications



64412.3.3RFE Technical Specifications

64612.4Hardware Architecture of ZXCBTS CDMA Micro BTS

64712.5ZXCBTS CDMA Micro BTS Product Characteristics

64912.6Networking Mode And System Configuration



656Exercises

657Chapter 13Remote RF Unit

657Objectives

657Introduction

65713.1Overview

65913.2ZXCBTS R800 Technical Specifications



66113.2.3Duplex Filter (MDUP) Technical Specifications

66213.2.4Low Noise Amplifier (MLNA) Technical Specifications

66213.2.5RX Filter Technical Specifications

66313.3ZXCBTS R190 Technical Specifications

66313.3.1Technical specifications


66513.3.3Duplex Filter (MDUP) Technical Specifications

66613.3.4Low Noise Amplifier (MLNA) Technical Specifications

66713.3.5RX Filter Technical Specifications

66713.4Hardware structure of the remote RF unit

67013.5Product features of the remote RF unit

67013.6Networking Mode and System Configuration



675Exercises

677Chapter 14ZXRPT-C800

677Objectives

677Introduction

67714.1ZXRPT-C800 Characteristics

67814.2ZXRPT-C800 Technical Specifications

67914.3Hardware Structure of ZXRPT-C800

68114.4ZXRPT-C800 Networking Mode

681Exercises

683Chapter 15ZTE CDMA Indoor Distribution System

683Objectives

683Introduction

68315.1Overview

68315.2Hardware structure of the Indoor Distribution System

68315.2.1ZXICS C800 System Structure

69015.2.2ZXICS C801 System Structure

69415.3Networking Modes And System Configuration

69415.3.1Networking Modes and System Configuration of ZXICS C800

70115.3.2Networking Modes and System Configuration of ZXICS C801

703Exercises

704Chapter 16ZTE CDMA Wide and Deep Coverage Solutions

704Objectives

704Introduction

70416.1ZTE CDMA Wide Coverage Solution

70416.1.1Overview

70516.1.2Features

70616.1.3ZTE CDMA Wide-Coverage Product Series

71016.2ZTE CDMA Deep Coverage Solution

71016.2.1Overview

71116.2.2Features

71216.2.3ZTE CDMA Deep-Coverage Product Series

719Exercises

721Chapter 17ZTE CDMA-WLL Solution

721Introduction

72117.1CDMA-WLL Characteristics

72217.2ZTE CDMA-WLL Solution

72217.2.1Network Architecture

72317.2.2Network Interfaces

72417.2.3Network Features

724Exercises

725Chapter 18ZXPDSS Packet Switching System

72518.1System Overview

72518.1.1Location of the ZXPDSS System in Networks and the Main System Functions

72718.1.2Overall System Performance

73018.1.3Interface Features

73218.1.4Service Application

73218.1.5Product Technical Standards

73518.2Cdma2000-1x Packet Data Switching Node (ZXPDSS-P100)

73518.2.1Working Principles

74218.2.2Performance Specifications

74218.2.3Equipment Functions

74318.2.4Equipment Data

74318.3cdma2000-1x Packet Data Home Agent (ZXPDSS-H100)



74518.3.3Equipment Function


74618.4cdma2000-1x Packet Data Authentication, Authorization and Accounting Server (ZXPDSS-A100)



74818.4.3Equipment Functions


75118.5Networking Mode

75218.5.1Small-capacity Networking Mode (100,000 users)

75318.5.2Intermediate-capacity Networking Mode (150,000 users)

75418.5.3Large-capacity Networking Mode (600,000 users)

75418.6System Configuration Principles

75418.6.1General Traffic Model

75418.6.2Module Calculation Methods

755Exercises

756Chapter 19Hierarchical Centralized Network Management Center (ZXCOMC)

756Introduction

75619.1Overview

75819.2Protocols and Standards

75819.2.1Protocols

76019.2.2Standard

76119.3Technical Specifications

76119.3.1System Specifications

76219.3.2Environmental Specifications

76319.4ZXCOMC System Architecture

76319.4.1Overall Architecture of the XCOMC System Hardware

76319.4.2Mechanical and Electrical Characteristics

76419.4.3ZXCOMC System Software Structure

76519.4.4System Support Function Subsystem (SSF)

76519.4.5Workstation WSF Subsystem

76619.4.6Operation & Maintenance Function (OMF)

76619.4.7Network Element Adaptation Function (NAF)

76719.4.8Software Environment Requirements

76819.5Service Functions

76819.5.1Introduction to Service Functions

77119.6Networking Modes and System Configuration

77119.6.1Networking Modes


774Exercises

776Chapter 20Introduction to ZTE cdma2000 1x Services

77620.1Introduction to ZTE cdma2000 1x Services

77620.1.1Basic Services

77720.1.2Supplementary Services

78420.1.3Packet Data Service

78520.1.4Short Message Services

79820.1.5Locating Service

80120.1.6Intelligent Service

81220.1.7Characteristic Services of ZTE cdma2000 1x Mobile Communications System

817Exercises

819Chapter 21ZTE Network Planning and Optimization Solution

81921.1Purpose, Principle and Workflow of Network Planning

81921.1.1Purpose of Network Planning

82021.1.2Principle for Site Selection of Base Stations

82121.1.3Instruments Required for Network Planning

82221.1.4Pre-sales Network Planning Process

82221.2Typical Cases Analysis of ZTE Network Optimization and Planning Solutions

82221.2.1Overview

82321.2.2Introduction to Geographical Environment

82321.2.3Existing Network Conditions

82421.2.4Demand Analysis

82521.2.5Network Planning Solution

82721.2.6Electrical Measurement and Model Correction

82921.2.7Link Budget

83221.2.8Capacity Analysis

83521.2.9Coverage Simulation Forecasted Result

83621.2.10Planning Summary

83621.2.11Network System Indices

842Chapter 22Networking Configuration Analysis with Typical WLL Cases

842Introduction

84222.1ZXC10-BSS (V5.0) Networking Mode

84222.1.1Star Networking Mode

84322.1.2Ring Networking Mode

84322.1.3Chain Networking Mode

84422.1.4Star-chain Hybrid Networking Mode

84422.2Analysis on ZTE CDMA WLL Application Example

84522.2.1Case: Shenzhen 1.9G CDMA WLL

84522.2.2Case Analysis

84622.2.3Equipment Adopted in Deep coverage

84722.2.4Characteristics of ZTE CDMA WLL Deep coverage Solution

849Chapter 23Networking Configuration Analysis with Typical cdma2000 1x Cases

84923.1Phase II cdma2000 1x Network Construction Scheme of Hainan Unicom

84923.1.1Overall Construction Concepts of the Phase II Network of Hainan Unicom

85023.1.2Overview of Hainan Unicom Phase I Network

85023.1.3Overall Construction Principle of Phase II Network of Hainan Unicom

85123.1.4Core Network Circuit Domain Construction Scheme

85523.1.5Core Network Packet Domain Construction Scheme

85623.1.6Radio Network Construction Scheme

86223.1.7Construction Scheme for Phase II Network of Hainan Unicom

86323.2ZTE C++ Elaborate Network Solution

86323.2.1Overview of ZTE C++ Network

86423.2.2ZTE C++ Network Solution

86423.2.3ZTE C++ network Integrated Service Solution

86523.2.4Overview of On-site Demonstration of ZTE C++ network in Haikou

86623.3Chongqing (Wanzhou, Fuling and Qianjiang) Radio Network Coverage Solution

86623.3.1Wanzhou Coverage Solution

86823.3.2Coverage Solution in Fuling

87023.3.3Qianjiang Coverage Solution

87023.3.4Characteristics of Wide Coverage

87123.3.5Characteristics of Deep Coverage

873Reference

875Appendix A Abbreviations

888Appendix B FAQ

Part 1CDMA Principles and Techniques ZTE Corporation

February 2003PrefaceThis part mainly introduces the principles, development and features of the CDMA technologies, including the overview of cdma2000 and PDSN working principles, as well as the overall and latest development of 3G.

The contents of this part are organized as follows: Chapter 1 introduces the development, main features and current market situations of CDMA. Chapter 2 introduces some basic working principles of CDMA. Chapter 3 introduces the working principles of IS-95 system. Chapter 4 introduces the working principles of cdma2000 on the wireless and the core network sides, including the introduction to PDSN. Chapters 5 and 6 take the technical evolution of ZTE as an example to introduce the evolution policy of the 3G technologies. Chapter 7 introduces the advantages and disadvantages of CDMA.

After reading this part, the reader should be able to get a general understanding concerning the basic working principles and key technologies of CDMA; basically master the working principles of cdma2000 at the core network and wireless sides; acquire a deep understanding of advantages and disadvantages of CDMA; and be familiar with the development of CDMA and some basic concepts of 3G. Chapter 1 Why CDMA?

Objectives

After learning this chapter, you shall be able to:

Know the history of wireless communications;

Be familiar with the basic concepts, standards and the evolution of CDMA;

Know the general situations in respect of research and development, products and marketing of ZTE.

Introduction

All our customers have been engaged in the wireless communication industry for decades, and are well experienced. To serve them, you must gain some knowledge about the development of the wireless communications. Through learning this chapter, you will get a comprehensive knowledge concerning the development of the wireless communications, and know about the development trend, the companys research and development as well as the market situations to some extent, which may lay a foundation for learning latter chapters. This is the goal of learning this chapter.

1.1 Development of Mobile Communications and Brief History of CDMA

1.1.1 The First-generation Mobile Communication SystemAt the early 1970s, when Bell Laboratory put forward the concept and relevant theory in respect of the cellular system to cover a small area, some scientists first thought of the cell structure: In the architecture, cell is a kind of economical and efficient structure. The mobile network adopts the same mode. Different frequencies are used between adjacent cells, and same frequencies are used in the cells which are apart sufficiently far from each other. Then the co-channel interference can be effectively avoided, the same frequency can be used for many times, hence saving the frequency resources. Later, the cellular system developed rapidly, and quickly entered a practical stage. In the cellular network, each geographical area (usually a large and medium-sized cities and their suburb areas) is provided with many base stations, and is controlled by one mobile switch. At any place of this area, a mobile vehicle-mounted station and a portable phone can connect to PSTN via a radio channel and a switch, which can really achieve the communications with any place of the world at any time and any place. Meanwhile, as long as the adopted system is the same, the automatic roaming can be conducted, hence enlarging the movable range of the mobile station. The first-generation cellular mobile phone system is an analog cellular mobile system, characterized mainly by the use of analog mode to transmit the analog signal. AMPS (1983) of the U.S.A., TACS + ETACS (1985) of the U.K. and NAMTS (1978) of Japan have all developed their own systems.

In 1975, the Federal Communication Committee of the U.S.A. opened the mobile phone market, and decided the frequency spectrum of land mobile communications and large-capacity cellular mobile communications, which made preparations for the mobile phone to be put into the commercial use. In 1979, Japan put the first cellular mobile phone of the world into use, i.e., NAMTS. In 1979, the AMPS analog mobile cellular system was tested in Chicago of the U.S.A., and was finally put into commercial use in the U.S.A. in December 1983.

In 1977, China began to adopt the analog cellular phone for communications. The first mobile phone communication office of China was deployed in Guangzhou in November 1987.

1.1.2 The Second-generation (2G) Mobile Communications System

The rapid development of the first-generation analog cellular system also constantly exposed disadvantages, especially in the large cities with dense populations. As the frequency resources become more and more insufficient due to the frequency-division multiple access technology adopted by the analog cellular phone, and the analog cellular system is vulnerable to eavesdropping and disclosure, the users benefits may be harmed.

After the mid of 1980s, wide applications of the large-scale integrated circuits, microcomputer, microprocessor and digital signal processing technologies, provided technical support for the development of the digital mobile communication system.

In 1982, the GSM organization was established in Europe to develop the Pan-European mobile communication roaming standards. They discussed and tested 8 different laboratory plans, and finally formulated the Pan-European Global System for Mobile Communications (GSM). For the GSM mobile system, the frequency spectrum usage rate is high and the capacity is increased, and the automatic roaming and handover function can be achieved. With the adoption of Enhanced Full Rate (EFR) coding technique, the communication quality is satisfactory. In addition, thanks to such advantages as rich service types, easy encryption, strong interference immunity, small user device and low cost, the mobile communication is enabled to enter a new milestone.

On September 18, 1993, the first GSM digital mobile communication network in China was deployed in Jiaxing, Zhejiang Province. In October 1994, the first provincial GSM mobile communication network was deployed in Guangdong Province with the capacity reaching up to 50,000 subscribers.

Another mode of the 2G mobile communication system is Code Division Multiple Access (CDMA), which is a kind of advanced wireless spread spectrum communication technique adopted in the digital mobile communication during recent years. The original intention of developing the CDMA technology is to prevent the communication interference from enemies. During World War II, CDMA technology was developed and widely adopted in the military communications of anti-interference and privacy. Later it was developed and put into use of the commercial communications by Qualcomm Corp. of the U.S.A. As CDMA is originally adopted in the military communication, its security is very powerful and its technical implementation is very difficult. In 1989, Qualcomm sent the CDMA digital mobile communication system to Pacific Bell Company for small-scale test. In 1995, Hongkong Hutchison Telecomm deployed the first CDMA commercial system of the world. Many theoretical advantages of CDMA technology were verified in the practice, and they were rapidly promoted and applied in the Northern and Southern America, and Asia, etc. Many countries and regions in the world, including Hongkong of China, South Korea, Japan and the U.S.A., set up the CDMA commercial network. In the U.S.A., of 10 mobile communication operators, 7 operators adopted CDMA network. In South Korea, 60% populations are the CDMA mobile users. At the 28th Olympic Game held in Australia, CDMA technology played a significant role. In 1995, the Headquarters of the General Staff of Chinese Army and the Ministry of Post & Telecommunications of China decided to adopt the dedicated 800M-frequency in the army to set up the CDMA pilot networks in four cities, i.e., Beijing, Shanghai, Xian and Guangzhou.

To a great extent, the 2G mobile communication technology eliminated many defects of the FM technique adopted in the 1G mobile communications, thus significantly meeting various communication requirements at the time. Moreover, it had acquired wide application all over the world. As the mobile communication demands constantly increase, the people in the developed countries and regions soon found that the 2G communication technology could not meet the increasing requirements any more. The first problem lies in the network capacity. More and more mobile subscribers were too heavy for the network to bear. Although the network optimization became better and better, the users felt more and more unsatisfactory in their communications use. Such problems as call drop, connection unable and network busy annoyed the operators. The constant emergence of new technologies such as DCS1800, dual coverage and Micro Cell could still not satisfy the requirements of people. Furthermore, at the time when the 2G network technology is put forward, the standard development organizations made a serious mistake in estimating the demands for the mobile data service. Therefore, it becomes a hard potato for the 2G network technology to meet the increasing demands for the wireless data service.

The CDMA technology is a rising star in the mobile communication field. Compared with the traditional GSM technology based on time division multiplexing mechanism, it has obvious advantages. First, the capacity is larger and the usage rate of the frequency spectrum is higher in the CDMA system. With the same frequency segment as that of GSM, more users are allowed to use the system. According to estimation, with the same frequency resources, the CDMA network has a system capacity as large as 8~10 times of that in FM analog network, and 3~4 times of that in the GSM network. Second, the planning and construction of the CDMA system network are simpler than the GSM network. Finally, with the combination of CDMA, Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA) technologies, greater data bandwidth can be provided on the basis of limited frequency spectrum. The High Data Rate (HDR) technique currently shown in the cdma2000 system can provide 2.4 Mbps data bandwidth based on the frequency spectrum of 1.25 MHz, and the usage rate of the frequency spectrum reaches 1.92 bps/Hz, which is much higher compared with the traditional wireless communication technology. The usage rate of the frequency spectrum of 1x TREME can reach 3.84 bps/Hz in the future. With integration of the current developing WLAN technology, the users can easily enjoy the broadband mobile data service at any place in the near future.

1.1.3 Basic Concept of CDMAThe CDMA system is a self-interfering system, in which all the mobile users occupy the same bandwidth and frequency. This system allocates each user a unique code sequence (spread spectrum code), which is used to encode the signals of the bearer information. The receiver that knows the code sequence decodes the received signals and restores them to the original data because the crosscorrelation between the code sequences of one user and another user is very slight. Lets draw an analogy. Image the bandwidth as a large room. All the people will enter the only large room. If speaking in completely different languages, they can clearly hear the voice of their fellows, and can only be interfered by the conversations of other people. The air in the room can be imaged as the carrier of the bandwidth, and different languages are regarded as the codes. We can constantly add the users until we are blocked by the background noise. If the users signal intensity can be controlled, we can accommodate more users while keeping high-quality communication.

As the bandwidth of the code sequence is much wider than the bandwidth of signal bearing information, and the frequency spectrum of the signal has been spread in the encoding process, so this is called as spread spectrum modulation, and the generated signals are called as spread spectrum signals. CDMA is often indicated by Spectrum Spreading Multiple Access (SSMA). The spread spectrum of the transmitted signals is to provide the CDMA with multiple access capability. The spread spectrum modulation technique must cater to two basic requirements:

1.The bandwidth of the transmitted signals must be much greater than the information bandwidth.

2.The bandwidth of the generated RF signals is independent of the transmitted information.

In the spread spectrum system, the ratio of the bandwidth (Bt) of the transmitted signals to the information bandwidth (Bi) is called as the processing gain of the spread spectrum system, i.e., Gp = Bt/Bi. It can be seen that the processing gain of the CDMA system is very high.

The receiver adopts the same spread spectrum code and the received signals to conduct the correlation operation to restore the carried original information.

As the spread spectrum signal is a spectrum-spread signal, it has many advantages that are different from those of the narrowband signal.

Multiple access capability

Multi-path interference resistance capability Privacy Man-made interference resistance

Low interception probability Narrowband interference resistance capability

According to different spread spectrum modulation modes, CDMA can be divided into Direct Sequence Spread Spectrum (DS-SS), Frequency Hopping Spread Spectrum (FH-SS), Time Hopping Spread Spectrum (TH-SS) and hybrid spread spectrum.

1.2 Evolution of CDMA Standards and the Third Generation (3G) Mobile Communications1.2.1 Evolution of the CDMA Standards The development process of the CDMA standards at the wireless side can be represented by the chart below. The evolution process of the CDMA standards is roughly divided into the following stages: cdmaOne, namely, IS-95A and IS-95B: It mainly supports the voice service, belonging to G2 communication.

cdma2000 1X: It can support both voice and data services. The max. data rate can reach 153 kbps, belonging to 3G mobile communications.

cdma2000 1xEV-DO: As the enhanced version of cdma2000 1X at stage 1, it supports data services, with max. forward rate being up to 2.4 Mbps.

cdma2000 1xEV-DV: As the enhanced version of cdma2000 1X at stage 2, it supports both voice and data services, with max. data rate being up to 4 Mbps, and even higher.

Fig. 1-1 ZTE CDMA Roadmap

IS-95 is the first-released standard of the cdmaOne series standards. But the first CDMA standards really and widely applied in the world are IS-95A which supports the 8K code voice service and the STD-008 standard of the 1.9 GHz CDMA PCS system. The 13K code voice service quality is already very close to the voice service quality of the wireline phone. With the increasing demands of the mobile communication for the data service, Qualcomm of the U.S.A. declared in February 1998 to apply the IS-95B standard to the basic platform of CDMA. With IS-95B standard, the CDMA system performance could be enhanced, the data flow of the users mobile communication equipment could be increased, and the 64 kbps data service could be supported. Later, cdma2000 became the transitional standard from the narrowband CDMA system to the 3G system.

1.2.2 Why the 3G Demanded With the social progress, people have raised higher requirements for the mobile communication. Although 2G technology can well provide the mobile voice communication, it seems to be incapable to satisfy the ever-increasing requirements of the people who expect to enjoy the data and multimedia mobile communication. Furthermore, in the highly populated developed areas, the 2G system also is facing the technical bottleneck, which cannot meet the requirements of the increasing users capacity.

We are earnestly expecting the 3G technology, i.e., the third-generation mobile multimedia service. The 3G technology features the use of the enhanced broadband data and multimedia over the IP and ATM networks. The data transmission rate of the current 3G system can reach 144 kbps on the vehicle, 384kbps while walking outdoor, and 2 Mbps inside a building, which can be further increased in future. The 3G service involves video stream, audio stream, mobile interconnection, mobile commerce and e-mail, and it can be ultimately developed for the video mail and file transfer. Till now, the 3G standards have been developed in the world, and put into commercial use in many countries. They are cdma2000 technology, UMTS technology and TD-SCDMA technology developed in China. Here we take emphasis on the cdma2000 technology.

In the aspect of the mobile user:

2G (2.5G) and 3G networks will coexist for a long time. Like other new technologies, it also takes time for the 3G network to become popular. When necessary, most users will use the products based on the 3G network. Home computer is just in a similar case. For example, if a 386 computer is unable to support some game and software programs, it will upgrade to 486 or Pentium series. Although many mobile users are satisfied with the existing 2G products, the commercial and high-end users expect to enjoy the broadband wireless data products resulted from the 3G network. Therefore, a mobile operator must concurrently provide the services of both 2G and 3G.

The mobile operators intend to ensure the smooth evolution for the users. To keep their current users, an operator will gradually introduce new services to achieve the smooth evolution. This is why 2G and 3G services will coexist in the coming years. For most existing users, the 2G service can satisfy their requirements within a certain time. For the users who only use the cellular phone voice service, they possibly need not change to use the 3G network temporarily. For this reason, the smooth evolution from 2G to 3G network is very important for the mobile service operators.

In respect of the technical aspect:

IS-95 is the first-released standard of the cdmaOne series standards. But the first CDMA standard really and widely applied in the world is IS-95A. Later, such standards as TSB74 supporting 13K voice encoder, STD-008 supporting 1.9 GHz CDMA PCS system, and IS-95B supporting 64 kbps data service were developed.

The major difference between IS-95B and IS-95A is that the former allows many channels bound together. If the auxiliary traffic channel is not used, IS-95B is basically the same as IS-95A, and they can coexist in the same carrier.

The cdma2000 1X, the first stage of the 3G cdma2000 wireless communication system, is evolved from cdmaOne, with the main features of backward compatibility with the existing TIA/EIA-95-B standard and sharing or overlapping the frequency band with the IS-95A/B system. The cdma2000 1X differentiates from IS-95 via different radio configurations (RC). Through setting of RC, 1X and IS-95A/B terminals can be supported at the same time. Therefore, IS-95A/B and cdma2000 1X can coexist in the same carrier.

The cdma2000, a 3G RTT scenario put forward by TIA TR45.5 of the U.S.A. to ITU, can effectively support the existing IS-634A standard, with the core network based on ANSI-41. With network expansion mode, it can provide the running capability in the core network based on GSM-MAP.

The evolution roadmap of our products is: IS--95A ( cdma2000 1xRTT ( HDR ( ALL IP BSS products.

In recent years, the mobile communication market in the world continue to show the rapid development. According to the estimation of EMC (www.emc-database.com), the number of mobile users in the world will reach 1.6 billion in 2005. By the end of 2001, the number of mobile users in the world had reached about 950 million, with an increase of about 230 million from 720 million at the end of 2000, basically the same increase as that in 2000. Compared with that in 2000, the average traffic of each user in the world almost kept the same. However, in some countries where the service is highly popular, such as Northern European countries, the traffic of each user appears to be developing. Therefore, the traffic in the world was increased by more than 30% in 2001. In addition, the mobile data service is surprisingly increased. The number of short messages sent in the world reached 30 billion in December 2001, with an increase of about 10 times that of the previous year. In Japan, the number of Internet mobile service users (I-mode and similar services) reached about 50 million. The data service income was increased by 30% or so, with an average percentage of 4% ~ 5% of the total revenue of the operators in the world. For some operators, the data service income already counted for 15% ~ 20% of the total revenue of the operators in the world.

Currently, between the latest two outstanding 3G scenarios in the world, in the UMTS specifications, the WCDMA standards are constantly developed with new versions, diversified and fast changes, hence causing its less stability. Under this situation, it is very difficult for a manufacturer to adopt one of the versions to manufacture the equipment and the terminal device. For example, more than 500 items are pending in the version of R99 released in March 2001. Compared with the version of June 2001, the new R99 version passed at the 3GPP conference held in Beijing at the end of September 2001, 266 newly revised items passed. Obviously contrasted with the above, it is smoother for cdma2000 to evolve from 1x to 1x EV-DV. In the forward extending process of cdma2000 1x, the wireless subsystem only needs to be partially changed in the hardware and software aspects, and it is relatively more stable. Therefore, cdma20001x actually put in the commercial operation enjoys a lions share in the market currently. As cdma2000 is directly evolved from the previous CDMA system, it can provide a quickest, simplest approach at lowest cost for the 3G services. All the 3G technologies (cdma2000, WCDMA and TD-SCDMA) may be practical, while cdma2000 is the most advanced in the aspects such as product development, commercial use and market acceptance.

With increasing demands for information, the data service is developing based on diversity, large-capacity and asymmetry. To cater for the increasing data service, ZTE keeps up with the communication industry in the world, being the first company to deploy the cdma2000-1x mobile communication system in China and to develop the cdma2000-1x EV-DO mobile communication system successfully.

1.2.3 Key Technical Features of cdma2000 1XThe cdma2000 1X has a capacity twice as much as that of the IS-95A system, and can support the data transmission of 144 kbps. Compared with IS-95A, the cdma2000 1X is greatly enhanced in the aspects including wireless channel type, physical channel modulation and wireless packet interface functions. The packet switching mode is introduced in the network; and the mobile IP service is supported. All these technical features are to satisfy more 3G services with greater complexity.

The cdma2000 1X provides a reverse pilot channel, which enables the reverse channel to conduct the coherent demodulation. Compared with the incoherent demodulation technique adopted in the reverse channel of the IS-95 system, the gain can be increased by 3 dB, and the capacity of the corresponding reverse link is doubled.

The cdma2000 1X adopts the forward fast power control technique, which can control the power of the forward fast closed-loop. Compared with the slow power control technique only adopted in the forward channel of the IS-95 system, the capacity of the forward channel is greatly increased and the power consumption of the base station is decreased.

The cdma2000 1X adopts the fast paging channel, hence greatly decreasing the power consumption and increasing the standby duration of the mobile station. The standby duration of the cdma2000 1X mobile station is over 5 times that of the IS-95 mobile station.

The Orthogonal Transmit Diversity (OTD) and Space Time Spreading (STS) technologies is adopted in cdma2000 1X forward channel, hence improving the fading-resistant capability of the channel as well as the signal quality of the forward channel. With the orthogonal transmit diversity and forward fast power control technologies; the capacity of the cdma2000 1X forward channel is twice as much as that of the IS-95A system.

The Turbo code can be used over the cdma2000 1X traffic channel because the gain of 2 dB can be obtained if the Turbo code other than the convolutional code is used in the channel code. Therefore, the capacity of the cdma2000 1X system can be increased by 1.6 times that when the Turbo code is not used.

New access mode is also defined in the cdma2000 1X, which can shorten the call setup time, and lighten the interferences caused to other users in access process of the mobile station.

For the packet service of the cdma2000 1X, besides the forward and reverse basic traffic channels, the system also needs to set up the corresponding auxiliary code-division channel. If the forward link needs to transmit a large quantity of packet data, the base station will send the auxiliary channel allocation message to set up the corresponding forward auxiliary code-division channel, which transmits the data to the mobile station via the forward auxiliary code-division channel within the time specified in the message. If the reverse link needs to transmit a large amount of packet data, the mobile station will send the auxiliary channel request message to set up a corresponding reverse auxiliary code-division channel with the base station, so that the data can be transmitted to the base station via the reverse auxiliary code-division channel within the time specified in the message. From the above, we can see that the setup of the auxiliary channel enables cdma2000 1X to support the packet service more flexibly.

In cdma2000 1X, the data service of 144 kbps can be provided, and the auxiliary code-division channel is added. Several data flow and multiple services can be carried simultaneously for one user. Therefore, the services provided in cdma2000 1X are much more increased than those provided in IS-95, thus laying a foundation for supporting various multimedia packet services.

1.3 Analysis and Prospect of CDMA Market1.3.1 Overview At the end of 1980s, thanks to the abrupt change from analog to digit cellular technology in the world, the GSM technology developed in Europe was tremendously benefited, rapidly promoted in about 100 countries, and unquestionably taking the leading position in the market. However, the breakthrough in term of technical and economical performances is the application of CDMA technology in the mobile communications. During recent years, through the wide discussion and argumentation in the telecommunication industry, a new industry with great potentiality has been formed for CDMA; especially the actual operation of the commercial CDMA system in the world proves the maturity of the CDMA technology. Furthermore, the CDMA mode has been recognized as the air interface standard in the industry of the 3G mobile communications.

Compared with other existing cellular systems, significant advantages are available in CDMA: For operators, the CDMA system can increase the usage rate of the frequency spectrum, greatly save the frequency resources, decrease the number of base stations, and low down the project implementation cost; for users, the CDMA system can provide high-quality voice, better privacy, low call drop rate and low mobile transmitting power which save the battery power.

The narrowband CDMA based on IS-95 can be more smoothly transited to the 3G mobile communication.

Currently, there are more than 10 CDMA system vendors and the number of mobile phone manufacturers has reached over 40 in the world. ZTE already successfully developed the CDMA-IS95 and cdma2000 systems, and put them into commercial use in a large scale.

According to the development trend of CDMA in the world, the evolution from CDMA technology to the 3G mobile communication system will be greatly sped up. Currently, CDMA network in the world has been developed in 44 countries, with more than 120 networks, of which, 41% of them are in the Asia-Pacific regions, 38% in Northern America, 19% in Latin America and 2% in other regions. It is estimated that the total number of CDMA users will reach 280 million in 2006, of which, 80% are the cdma2000 mobile communication network users. The monthly mobile data volume of each user will exceed 200 MB, which reaches the application level of the data volume in the existing wired Internet. In the countries such as South Korea, India, New Zealand and Australia, the CDMA market is developed at an extremely fast speed. The cdma2000 technology will be developed in three stages: cdma2000-1x, 1x EV-DO and 1x EV-DV. Its downstream data transfer rate will be increased to 2.4 Mbps, even 4.8 Mbps from 153.6 kbps in the frequency width of 1.25 MHz, which directly leads the higher usage rate of the frequency spectrum. The cdma2000-1x is most successfully applied in South Korea, and the total number of users has already reached more than 28 million. The three big operators in South Korea, i.e., SK, KTF and LG, have developed cdma2000-1x services. For the network construction, SK and KTF adopt the overlap mode, and LG telecom has upgraded the previous IS-95 network.

South Korea is the first country in the world to provide the synchronized cdma2000 1 XEV DO commercial service. SK Telecom deployed the pilot service on November 17, 2001. SK Telecom deployed the synchronized IMT 2000 (cdma2000 1 XEV DO) commercial service in Inchon city on January 28, 2002, which started the new era of the synchronized mobile communication. The synchronized IMT 2000 (cdma2000 1 XEV DO) commercial service was deployed in Soeul in the mid of February 2002, in 26 cities including Pusan, Daegu, Gwangju and other cities where the World Cup Football Match was held at the end of April 2002. And it was planned to deploy the commercial service in 81 cities of the country. This service is achieved via a PCMCIA mobile phone, which is a dedicated mobile phone connected to a PDA or a notebook for wireless data communication. In April 2002, ordinary mobile phones were employed. VOD and mobile Videophone debuted in May 2002. During the World Cup Football Match, the football fans from all over the world had experienced the IMT - 2000 mobile communication service represented by the videophones, with the max. transmission rate of 2.4 Mbps, being over 16 times faster than the current rate of 144 kbps of the cdma2000 1X network. The service can be retrieved during travel, and can provide wireless multimedia services such as VOD, cartoon and photograph mail.

According to the prediction conducted by Datacomm Company, the number of CDMA users in the world will count for over 35% of the total number of mobile users in the world within the coming five years. In many developing countries where mobile communication is undeveloped, the CDMA mode will be much more adopted in the mobile communication network construction than the GSM mode. With the rapid development of the mobile communication market in the developing countries, the CDMA network will be greatly popularized in the world.

Currently, the CDMA network is being employed in more than 40 countries in the world, and it is employed as the main mobile communication network in such countries as the U.S.A., South Korea, Japan and Australia, and in some regions of South America. CDMA Development Group (CDG) released in its investigation report: In the third quarter of 2001, the number of CDMA mobile communication service users in the world reached 95 million, with an increase of 10% from the same period in 2000. And it is estimated that the number of CDMA users will exceed 100 million by the end of this year. In September 1997, the number of CDMA users in the world is about 5 million. Four years later, the number of CDMA users is increased by about 20 times, what a surprising development speed. Especially in Asia, the CDMA service is tremendously developed during recent years. The number of CDMA users in Asia is increased by 88% to 28 million. In the Asia-Pacific area, the CDMA commercial networks are constructed in many countries and regions including Hong Kong of China, Japan, South Korea, Australia, Thailand, Philippines, New Zealand and Bengal. And the number of CDMA users has exceeded 21 million.

In the international market, the CDMA products developed by ZTE have strong capability to compete with the products manufactured by any other manufacturers.

1.3.2 General Introduction to the ZTE ProductsCurrent situations of research and development:

In the CDMA development process, ZTE has had altogether about 1,500 persons devoted in the research, development and test field, and about 400 persons in the project deployment. Among them, those with the academic education of master degree or higher count for more than 80%, which forms a strong technical force.

Currently, ZTE can provide a complete set of networking scheme of the IS-95 and cdma2000 1X mobile phone systems and the CDMA wireless Local Loop (WLL) systems at three frequency bands, i.e. 450M, 800M and 1.9G.

The cdma2000 1x EV-DO (HDR) system was shown at the 3G Annual Fair held in Hong Kong of China in 2002, and was also exhibited in Guizhou Province and Guangxi Chuang Autonomous Region of China.

Currently, ZTE is developing the products based on ALL-IP platform, i.e. Super BSC and Super BTS. The ALL-IP network is the development trend of the future communication technology, and the voice and data services are provided over the IP network.

The 1XEV-DO and ALL-IP products will be provided simultaneously. According to the plan, the sample system should have been manufactured and debugged by May 2003. From then on, the data service with higher rate (2.4 Mbps) and all functions of the existing 1X system should be provided. And the pilot office will be deployed in November 2003 (the product will also be put into production at the same time).

Working frequency of the system:

The working frequency band of the 800M CDMA system should be within the ranges shown below:

(RX of the BS and TX of the MS)(TX of the BS and RX of the MS)

824 ~ 849 (MHz) 869 ~ 894 (MHz)


(RX of the BS, transmitted by MS)(TX of the BS, RX of the MS)

1850 ~ 1910 (MHz)1930 ~ 1990 (MHz)


(RX of the BS, TX of the MS)(TX of the BS, RX of the MS)

453 ~ 457.475 (MHz) 463 ~ 467.475 (MHz)

Exercise

1.Briefly describe the history of the wireless communication.

2.What are the features of the CDMA technology?

3.Briefly describe the evolution scenario of the CDMA technology.

Chapter 2 Principles of the CDMA System Objectives

After learning this chapter, you shall be able to:

Learn some basic concepts of the CDMA system. Learn the features of the CDMA cellular mobile communication network.

Grasp the principle of the spread spectrum communication.

Understand the features of the mobile channels, so as to make good preparation for learning the next chapter of cdma2000 1xRTT system principles.IntroductionThis chapter mainly introduces the basic working principles of CDMA, including some basic concepts of CDMA, and basic principle of Spread spectrum communication. At the end of this chapter, the features of channels are introduced.

2.1 Overview

CDMA is a kind of advanced multi-access mode, with a broad application perspective. Currently, it is the development hotspot in many countries around the world. The multi-access mode means that many user addresses use the same band for communicating with one another. Normally, these users scatter in different places and may be in the moving state. Here are two examples for the multi-access communication mode: multiple satellite communication earth stations communicate with one another via the same satellite transponder and many mobile user stations communicate with one another via the same base station. As the same transmission band is used, mutual interference may be generated among users, which is called multi-access interference. To reduce or eliminate the multi-access interference, different user signals must have certain features so that the receiver can differentiate them one another. This procedure is called signal division. Major signal division modes are: frequency division, time division, code division and space division. Frequency division: different users use different bands to implement the signal division. Time division: different users use different time slots to implement the signal division. Code division: all the users use the same band to transmit their signals at the same time and the signal division is implemented through the orthogonality or quasi-orthogonality among address code waveforms of different users. This mode is called the code division multi-access mode.

The code division multi-access system adopts the spread spectrum modulation signals. Its bandwidth is much greater than the bandwidth of the information signals, and the ratio of them may be tens, hundreds, or thousands. The power spectrum density of spread spectrum signals is extremely low, with very good concealment property and quite strong anti-interferences capability, e.g. anti-aiming interference, anti-multipath interference, etc. Back in 1960s, the spread spectrum technique is applied to the military and anti-interference communication. Since 1980s, with the fast development of the integrated circuit and computer technologies, the CDMA spread spectrum technique has been more and more applied to the civil communication systems. One typical application is the CDMA IS-95 digital mobile communication system developed by Qualcomm Corp. of the USA in 1990s.

The early mobile communication system is the information analog Frequency Modulation Frequency Division Multi-Access mode (FM-FDMA). This kind of system is being used till now. The digital modulation Time Division Multi-Access (GMSK-TDMA) communication system GSM developed at the early 1990s, is deemed as the representative of the new generation communication system. Meanwhile, the CDMA technology of Qualcomm Corp. is accepted as the major technique for the 3rd generation mobile communication. Currently, besides the mobile communication, the CDMA technology is being widely applied to many other fields, like the data transmission, satellite communication, and remote control and telecontrol and telemetry space communication.

As the spread spectrum signals are used, this kind of system has the capabilities against multiple kinds of interferences, especially the capability against the multi-path interference. The power spectrum density of the spread spectrum signals is very small. That is, the power of unit bandwidth is very small, nearly without interference for common non-spread spectrum communication systems. So, the same band can be shared with it, thus improving the spectrum availability. As all the users use the same carrier frequency and there is no cross-modulation, the frequency resources can be fully used. The multipath separation technique can be adopted to enhance the capability against the multi-path interference. 2.2 Basic Concepts of the CDMA SystemIn the CDMA system, each user is allocated with one unique code sequence (spread spectrum code, normally a PN code), which is also used to encode the signals bearing information. The receiver of the user who knows this code sequence decodes the received signals and restores the original data. This is because that the correlation between this user code sequence and other user code sequences is very weak. As the bandwidth of the code sequence is far bigger than that of the signal bearing information, the coding process spreads the spectrum of signals. So, it is also called spread spectrum modulation and the signal accordingly generated is called spread spectrum signals. Spreading the spectrum of signals transmitted provides CDMA with the multi-access capability.

The major difference between CDMA and GSM lies in the multi-access technique. That is, GSM uses different time slots to differentiate different users while CDMA uses different PN codes. For CDMA, first the user data (speech or data) is sent to the spread spectrum unit after being coded via channels. The spread spectrum unit generates one PN code which is unique for each user and multiplies it by the user data to generate a new spread spectrum sequence, which will be then sent to the radio frequency unit for transmission. At the receiving side, the process is just the reverse. First, the signal is received by the radio frequency unit. Then, the convolution despreading is conducted for received data on the despreading unit by using the same quasi-orthogonality PN code, thus obtaining the user data. Fig. 2-1 shows the process.

Fig. 2-1 Transmitting and receiving processes of CDMA

CDMA communication is also known as the spread spectrum multi-access communication. This is because the orthogonal code band is usually far greater than the user datas and the data is spread to a rather big spread spectrum for transmission after the operation between the PN code and the user data. The advantage of doing this is that during transmission, the signal energy is distributed across the entire bandwidth. The signal power per unit spectrum can be quite low, even lower than the background noise power. However, a relatively high receiver output signal to noise ratio and security can still be ensured.

The spread spectrum modulation technique must meet two basic requirements:

1. The bandwidth of the transmitted signal must be greater than that of the information.

2. The bandwidth of the radio frequency signal is irrelevant to the information to be transmitted.

The receiver uses the same spread spectrum code to conduct the correlation operation with the received signal to restore the original information carried. As the spread spectrum signal spreads the spectrum of signals, it has a series of performances different from the narrowband signals: multi-access capability, anti-multi-path interference capability, privacy, anti man-made interference capability, smaller interception probability and anti-narrowband interference capability.

2.3 Features of the CDMA Cellular Mobile Communication Network

Compared with FDMA and TDMA, CDMA has many special features. Part of them is inherent in the spread spectrum communication system and the rest is brought about by the soft handoff and power control technologies. The CDMA mobile communication network adopts multiple technologies, such as spread spectrum, multi-access, cellular networking, frequency reuse, etc., and is a kind of cooperative operation of 3-D signal processing of frequency domain, time domain and code (energy) domain. So, it has good anti-interference performance, capability against multi-path fading, and high security. The same frequency can be used in multiple cells repeatedly. The required carrier-to-interference ratio (C/I) is smaller than 1. Choices related to quality and capacity can be made based on requirements. These attributes provide the CDMA system following very important advantages compared with other systems:

High system capacity: In theory, the CDMA mobile network is 20 times greater than the analog network. In fact, it is 10 times greater than the analog network and 4~5 times greater than GSM.

Flexible system capacity configuration: This is related to the mechanism of CDMA. CDMA is a self-interfering system. All the mobile users occupy the same bandwidth and frequency. If we can control the signal strength of users, we can accommodate more users based on high conversation quality.

Good conversation quality: The voice quality of the CDMA system is very good. The voice encoder can adjust the data transmission rate dynamically. Meanwhile, it can select different level for transmission according to proper threshold values. At the same time, the threshold value varies with the changes of the background noise. Thus, even though the background noise is considerable, good conversation quality can be ensured.

In addition, the CDMA system adopts the soft handoff technique. During the handoff, the principle of first connect and then disconnect is adopted. Thus, the defect of the call drop in hard handoff can be overcome fully. The frequency planning is simple. Users are divided by sequence codes. So, the same CDMA carrier can be used in adjacent cells. The network planning is flexible and the expansion is simple. The battery life of the mobile station is lengthened. By adopting the power control and adjustable rate voice encoder, the service life of the mobile station battery is lengthened.

2.4 Principles of Spread Spectrum Communication

2.4.1 Brief Introduction

With the fast development of the computer network, the spread spectrum communication is being widely used because it provides computer networks with physical interface channels .

The spread spectrum communication, fiber communication and satellite communication together are named three major high-tech communication transmission modes in the information time. The spread spectrum communication technology is a kind of information transmission mode. It adopts the spread spectrum code for modulation at the transmitting end, thus making the bandwidth occupied by the signal much greater than the necessary bandwidth the information needs. At the receiving end, the same spread spectrum code is used for the correlation demodulation to despread so as to restore the information transmitted.The spread spectrum technique includes following methods: Direct sequence Spread spectrum (DS for short), Frequency Hopping (FH), Time Hopping (TH), and linear FM (Chirp). Besides, combinations of these spreading methods are also available, e.g. FH/DS, TH/DS, FH/TH, etc. In communication, DS, FH and FH/DS are widely used.

The spread spectrum communication technology has following features:

1) Strong anti-interference capability. As signals are spread to a quite wide band, it is necessary to conduct processing at the receiving end, i.e. compressing the bandwidth to restore the narrowband signals. As to the interference signals, they are spread to a very wide band as they are irrelevant to the spread spectrum PN code, thus reducing the interference power entering the signal band. Accordingly, the output signal/interference ratio of the correlator is increased and thus the anti-interference capability is very strong. Its anti-interference capability is in directly proportional to the times that its band is spread. The greater the spectrum is spread, the stronger the anti-interference capability will be.

2) Multi-access communication. Although the CDMA spread spectrum system occupies a quite wide band, its spectrum utilization ratio is even higher than that of the single-frequency single-carrier system because respective networks can use the same band at the time. In the future, CDMA will be a major multi-access communication mode for personal communication.

3) Good security. As the spread spectrum system spreads the information to be transmitted onto a quite wide band, its power density is reduced with the spreading of the spectrum, even fading in the noise. So, it has a good security. It will be very difficult to intercept or detect such signals, or it is impossible to do such actions for spread spectrum signals unless the same spread spectrum code as used by the transmitting end is used and the signals are synchronized, and correlation detection is also made. As the power spectrum density of the spread spectrum signal is quite low, in many countries (e.g. the USA, Japan, and some European countries), once the power spectrum density of a special band (e.g. ISM band) meets certain requirements, such a band can be used without approval.

4) Anti-multipath interference. In some communication environments, like the mobile communication, indoor communication, etc., the multi-path interference is very considerable. So, to guarantee smooth communication in such environments, a system must have very strong anti-interference capability. The spread spectrum has very strong anti-multipath interference capability. It provides the anti-multipath interference capability through the correlation property of the spread spectrum code used by the spread spectrum or even can improve the system performance with the multi-path energy.

Certainly, the spread spectrum communication has many other advantages, such as precious timing and ranging, arbitrary addressing, etc.

2.4.2 Basic Principles of the Spread Spectrum TechniqueThe basic feature of spread spectrum communication is that the spectrum of the baseband signals bearing the information data is spread by using the PN code with a rate many times higher than that of the information data to be transmitted, and accordingly the signal of low power spectrum density of broad band is formed for transmission. Shannon worked out the formula for calculating the channel capacity during the research of the information theory:

Where: Cchannel capacity, in bps; Bsignal bandwidth, in Hz; Ssignal mean power, in W; Nnoise mean power, in W.

This formula shows that if the information transmission rate C does not change, the bandwidth and the signal-to-noise ratio P/N can be exchanged. That is, increasing the bandwidth can transmit information reliably at the same information rate with a smaller signal-to-noise ratio. Besides, reliable communication can be kept by increasing the signal bandwidth accordingly even when the signals are submerged in noise, i.e., the advantage of a high signal-to-noise ratio can be obtained by transmitting information with a broadband signal through spreading spectrum. This is just the basic thought and theoretical basis of the spread spectrum communication.

The figure blow shows the structure of the direct sequence spread spectrum communication.

Fig. 2-2 The structure of the direct sequence spread spectrum communication

The figure below illustrates the entire spreading and despreading processes.

Fig. 2-3 The processes of spreading and despreading

The spread system has one important concept, i.e. spread spectrum gain. As the spread spectrum communication system spreads the signal spectrum at the transmitting end and restores the information at the receiving end, it brings an advantage that the anti-interference tolerance is improved greatly. Theoretical analysis shows that the anti-interference performance of a spread spectrum system is related to the bandwidth proportion of the spreading signal after the information spectrum is spread. Normally, the ratio of the spread spectrum signal bandwidth W to the information bandwidth F is called Gain Processing (GP), i.e. GP=W/F.

The processing gain indicates how the signal-to-noise ratio of the spread spectrum system is improved. Besides, other performances of the spread spectrum system are usually related to GP. So, GP is an important performance index. The greater it is, the better the performance will be.

Information data D becomes the baseband (narrow band) signals with bandwidth B1 after regular data modulation. The spread spectrum modulation is made for the baseband signals with the Pseudo Noise Code (PN Code) generated by the spread spectrum code generator, forming the spreading signals with a bandwidth of B2 (far greater than B1) and extremely low power spectrum density. This is equivalent to distributing the signal energy of narrow band B1 onto broadband B2 for transmission by adopting the PN code. The receiving end uses the same PN code as that used during the transmitting for spread spectrum demodulation and restoring the broadband signals to regular baseband signals. That is, the components corresponding to those of the transmitting are extracted from the broadband according to the regulation of the PN code and are integrated, thus forming the common baseband signals. Then, information data D can be demodulated with regular communication processing.

2.5 Walsh Code, m Sequence and M SequenceIn the CDMA system, some orthogonal and quasi-orthogonal codes are needed. Mathematically, there are many types of orthogonal functions, e.g. the Handmard function family, Walsh function family, Haar function family, etc. In CDMA system, the Walsh orthogonal code is adopted.

The Walsh function is a kind of binary orthogonal function system, with the value range of 1 and 1.It has multiple equivalent definition methods. The commonest one is the Handmard numbering method. The Walsh function in IS-95 just adopts this definition method.

The Walsh function set is a complete non-sine type orthogonal function set, usually used as the address codes of users.

In the IS-95 standard, the specific construction table of the Walsh function (r=6, n=26=64-bit 6464) is given.

The most important feature of the Walsh function is that it is orthogonal in the interval [0, 1]

By multiplying two Walsh functions, we can obtain another Walsh function, i.e. closeness for the multiplication. Besides, the Walsh function is fully orthogonal in the case of complete synchronization. However, in the case of asynchronization, its self-correlation and cross-correlation is neither ideal. Meanwhile, these two indices degrade remarkably with the increase in the value of the synchronization error.The following will discuss the features of the Walsh-PN compound code.

When meeting the strict synchronization, the Walsh function can implement the strict orthogonality. As the mobile channels are parameter-variable multi-path channels, it is very difficult to ensure strict synchronization.

When the synchronization error is produced, Walsh correlation will degrade quickly.

The m sequence self-correlation functions are not fully orthogonal. Its cross-correlation value is -1/p (p is the cycle of the m sequence).

Respective advantages of the Walsh code and the PN code are combined. That is, the features of the compound code can be used to overcome the defects of both.

In the CDMA system, three sequences are the long code, short code and Walsh code. The following conducts a comparison among them.

The short code is used for the orthogonal modulation of the forward/reverse channels. In the forward channel, different base stations use different short codes to mark themselves. The length of the short code is 215.

The long code is obtained by outputting the result of adding one PN code generated by a 42-bit shift register, one 42-bit long code mask, and modulo 2. The long code mask of each channel is different. Also, the long code mask is generated via a 42-bit shift register. The length is 242-1. In the CDMA system, the long code is used for scramble in the forward link and for spreading spectrum in the reverse link.

The Walsh code is used for the forward spreading spectrum of the CDMA system, by means of its orthogonality.

The table below gives a comparison among three codes of the CDMA system.Table 2-1 The comparison among three codes of the CDMA systemCode sequenceLengthApplication positionApplication purposeCode rate

m sequence (the maximal length linear feedback shift register, i.e. the long code)242 1Reverse access channelReverse traffic channelDirect sequence spread spectrumIdentifying the mobile station1.2288 M

Forward paging channelForward traffic channelUsed for data scramble19.2 K

M sequence (the Maximal length feedback non-linear shift register, i.e. the short code)215All the reverse channelsOrthogonal spreading helpful to modulation1.2288 M

All the forward channelsOrthogonal spreading is helpful to modulation and identify the base station.

Walsh function64All the reverse channelsOrthogonal modulation307.2 K

All the forward channelsOrthogonal spreading, identifying respective forward channels1.2288 M

2.6 Properties of Mobile Channels2.6.1 Properties of Mobile CommunicationRadio signals suffer various interferences during the propagation. People may say mobile channels are the most complicated communication channels. This is because that the radio signals will encounter various obstacles that make signals suffer fading caused by multi-path effect, shadow effect, scattering and diffraction, besides the interferences usually encountered in the cable channel. Moreover, signals can be affected by terrain. In addition, changes of the weather will also cause slow fading of radios signals. When a mobile station moves at a high speed, the situation may be worse. In this case, the Doppler frequency shift effect will happen to signals. Meanwhile, all these factors vary with the moving of the mobile station.

Multi-path propagationThe multi-path interference caused by multi-path propagation means mutual interference between the code elements at the receiving end caused by different arrival time of radio waves due to different transmission paths. It can cause the attenuation in the amplitude of the data signals transmitted. Also, the waveform broadening can be caused and thus the data transmission rate will be restricted. The multi-path interference occurring in the mobile channels are mainly caused by the signal reflection of huge buildings. From the angle of the mobile station, this means that the same signal arrives at the mobile station at different time and from different directions, which is shown in Fig. 2-4.

Fig. 2-4 Multi-path propagation of radio signalMulti-path signals not only scatter the energy of signals but also make only a part of the signal energy transmitted received by the mobile station. Besides, as the multi-path signals reach the mobile station via different paths and at different time, their phases thereby are different from each other as well. Thus, multi-path signals received by the receiver may cause extremely serious fading. In this way, the signal-to-noise ratio of signals is decreased greatly, and the communication effect is influenced. Besides, in the case of broadband communication, the spectrum of signals is comparatively wide, so the frequency-selective fading may also occur. This is mainly because some frequency components are fully cancelled out due to multi-paths as the fading depths generated on different frequencies are different in different multi-path cases. Fig. 2-5 shows the details.

Fig. 2-5 The real frequency-selective Rayleigh fading channel

In the figure, the vertical axis stands for the gain (in dB) and the horizontal axes stand for the frequency and time respectively. In this figure, we can see many deep valleys, where serious fading occurs. The so-called Rayleigh fading refers to the multi-path fading that the probability distribution function of the electric-field intensity of signals is subject to the Rayleigh probability distribution. And another major factor contributing to the Rayleigh fading is the Doppler effect, which will be discussed below. In the mobile communication, multi-path is unavoidable. Although it has serious interfere on communication, people can make use of it as well. For example, when a mobile station moves to the back of a big building and enters the shadow area, the radio signals can reach the mobile station by reflected signals only. People can use this reflected wave and/or diffracted wave to keep the continuity of the speech. In the GSM and CDMA mobile communication systems, the technical measures against the multi-path interference are time domain equalization and diversity reception.

Doppler frequency shift

In general knowledge, we all have such an experience: When a police car is bearing up to us, we may feel the alarm whistle become sharper and harsher while softer when it is bearing off us . This is just the frequency variation caused by the Doppler frequency shift. The Doppler frequency shift means that the multi-path effect not only can cause changes in the amplitude of the transmitted signals, but also can cause changes in the frequency structure of the transmitted signals. Thus, the phase fluctuates, which causes incorrect receiving of data signals. The Doppler frequency shifts value can be calculated with the formula below:

Doppler frequency shift = (movement speed/wavelength) ( COS (the included angle between the incidence wave and the movement direction)

When people make calls with a mobile station in a state of moving slowly, the Doppler frequency shift can be ignored. However, when people do that in a car moving fast, this factor must be considered.

Signal shadow and transmission loss

As mentioned above, as most of the signal energy is blocked by the building, fading will occur as well when a mobile station enters the shadow area of a building. In this case, the mobile station can receive the signals reflected or diffracted from other bodies only. However, this kind of fading is quite slower than that caused by the multi-path interference. So it is called slow fading. It is not so hard to deal with as the fast fading.

Fading means that the amplitude of the signals at the receiving end often changes randomly. That is, sometimes it is very heavy while sometimes it is very slight, without a regular pattern. According to fading period, fading is divided into the slow one and the fast one. The fast fading is normally caused by multi-path propagation. It causes serious distortion of signals. The slow fading is caused by such factors as different types of atmospheric refraction, terrain along the route or influences of other obstacles. With the increase of the frequency, the distribution curve that the signal level varies wit

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Training Material for CDMA Mobile Communication System