通信工程文献翻译——一、引言

扩频技术的历史(扩频,SS)可以追溯到1950年代中期,但直到80年代初,扩频技术主要应用于军事通信和秘密通信。随着个人通信服务的发展,全球定位系统(GPS)的应用,到目前为止,使用扩频技术,有超过一亿用户。无线通信已经成为电信行业最大的部门之一,经过十多年的稳步发展,是21世纪最有发展潜力。应用扩频技术在未来无线系统再次成为关注的焦点。

为了更好地掌握扩频技术在无线通信中的应用,本文首先介绍了扩频技术的基本情况,然后介绍了扩频技术的历史及其研究现状进行了讨论,最后结合无线通信系统的发展趋势,主要是第四代(4 g)移动通信系统,专注于扩频技术的发展趋势及其在未来无线通信系统中的应用。

二、扩频技术简介

扩频通信系统具备3个主要特征：

1、载波是一种不可预测的，或称之为伪随机的宽带信号；

2、载波的带宽比调制数据的带宽要宽得多；

3、接收过程是通过将本地产生的宽带载波信号的复制信号与接收到的宽带信号相关来实现的。

频谱扩展的方法主要有以下几种:直接序列扩频(DSSS)使用高速伪随机码扩频调制为低速数据传输,跳频系统是使用伪随机代码控制载频变化大频带;跳是伪随机数据传输时间槽;频率扩展线性调频系统是一个线性的变化过程。几种方式组合的混合系统也经常得到应用。

衡量扩频系统最重要的一个指标就是扩频增益，又称为处理增益。正是因为扩频系统本身具有的特征使其性能具有一系列的优势：

1、低截获概率；

2、抗干扰能力强；

3、高精度测距；

4、多址接入；

5、保密性强。

也正是这些特性使其获得了广泛的应用。

三、扩频技术的现状

1、扩频技术的研究现状

扩频技术由于其本身具有优良的性能和广泛应用,到目前为止,两个应用程序仍是主要军事抗干扰通信和移动通信系统,跳频系统和扩频系统分别在这两个领域最常用的扩频方式。一般来说,主要的跳频系统在军事通信对故意干扰,也用于秘密通信卫星通信,扩频系统主要是民用技术。

跳频系统的分析,仍专注于对各种干扰的性能,如计数器部分边带干扰和多个频率干扰。和扩频系统,即DS - CDMA系统,在移动通信系统的应用已经成为扩频技术的主流。GSM标准在欧洲和北美- 95基于CDMA技术的第二代(2 g)移动通信系统应用取得了巨大的成功。但目前所有的建议第三代移动通信系统(3 g)标准(除了边缘)采用某种形式的CDMA。所以CDMA技术成为研究最多的扩频技术中的对象,代码捕获技术和多用户检测(MUD)技术代表......

First, the introduction

The history of the Spread Spectrum technology (Spread Spectrum, SS) can be traced back to the mid - 1950 - s, but it was not until the early 80 s, Spread Spectrum technology is mainly used in military communication and secret communication. With the development of personal communications services, and the application of global positioning system (GPS), up to now, using spread spectrum technology, has had more than one hundred million users. Wireless communication has become one of the biggest department in the telecoms industry, after more than ten years of steady development, is the most potential for development in the 21st century. Application of spread spectrum technology in future wireless system has once again become the focus of attention.

In order to better grasp the application of spread spectrum technology in wireless communication, this paper first introduce the basic situation of spread spectrum technology, and then reviews the history of spread spectrum technology and its research status are discussed, and finally combined with the trend of the development of wireless communication system, mainly is the fourth generation (4 g) mobile communication system, focus on the development trend of the spread spectrum technology and its application in the future wireless communication system. 

Second, the introduction of spread spectrum technology

Spread spectrum communication system has three main characteristics: (1) the carrier is a kind of unpredictable, or called pseudo random broadband signal; (2) the bandwidth of the carrier has a much wider than the bandwidth of the modulated data; (3) receiving process is through the local broadband carrier signal generated in the replication of signal and the received broadband signals related to implementation. 

Spectrum extension ways mainly have the following kinds: direct sequence spread spectrum (DSSS) using high-speed pseudo random code spread spectrum modulation for to low speed data transmission; Frequency hopping system is using pseudo random code control carrier frequency ......