通信信号处理第三章2012概要
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通信信号处理摘要:在这通信信号处理这门课程中,老师给我们讲解了通信系统中的一些基本知识和一些关键技术,比如多输入多输出(MIMO,multiple-input multiple-output)、正交频分复用(OFDM,orthogonal frequency division multiplexing)以及比特交织编码调制(BICM,bit-interleaved coded modulation)等技术。
这篇文章的主要内容就是对本课程内容的总结以及自己的理解。
一、基本知识1.多径衰落(1)概念在通信系统中,由于通信地面站天线波束较宽,受地物、地貌和海况等诸多因素的影响,使接收机收到经折射、反射和直射等几条路径到达的电磁波,这种现象就是多径效应。
这些不同路径到达的电磁波射线相位不一致且具有时变性,导致接收信号呈衰落状态;这些电磁波射线到达的时延不同,又导致码间干扰。
若多射线强度较大,且时延差不能忽略,则会产生误码,这种误码靠增加发射功率是不能消除的,而由此多径效应产生的衰落叫多径衰落,它也是产生码间干扰的根源。
对于数字通信、雷达最佳检测等都会产生十分严重的影响。
(2)分类主要可以分为两种,频率选择性衰落和频率非选择性衰落(平坦型衰落)。
如果各条路径传输时延差别较大,传输波形的频谱较宽(或数字信号传输速率较高),则信道对传输信号中不同频率分量强度和相位的影响各不相同。
此时,接收点合成信号不仅强度不稳定而且产生波形失真,数字信号在时间上有所展宽,这就可能千万前后码元的波形重叠,出现码间(符号间)干扰。
这种衰落称为频率选择性衰落,有时也简称选择性衰落。
如果各条路径传输时延差别不大,而传输波形的频谱较窄(数字信号传输速率较低),则信道对信号传输频带内各频率分量强度和相位的影响基本相同。
此时,接收点的合成信号只有强度的随机变化,而波形失真很小。
这种衰落称为一致性衰落,或称平坦型衰落。
瑞利信道(包络的一维统计特性服从瑞利分布)就是典型的平坦型衰落信道。
现代通信系统的信号处理方法研究第一章:引言随着现代通信技术的不断发展和普及,越来越多的通信设备、网络和系统被广泛应用于各个领域,如无线通信、卫星通信、光纤通信、数字电视等。
信号处理作为现代通信系统中的重要一环,对于实现高效、稳定、高品质的通信具有至关重要的作用。
本文将对现代通信系统的信号处理方法进行研究,分析和探讨其在实际应用中的优缺点以及未来的发展方向。
第二章:通信信号处理的基本概念通信信号处理是指对传输信号进行处理的一系列技术,包括信号采样、滤波、数据压缩、信道编码和解码等工作。
其中,信号采样是将连续时间信号转化为离散时间信号的过程。
滤波是对信号进行波形修正,去除无用的频率成分的过程。
数据压缩是将信号的冗余部分压缩以减少信号传输的数据量。
信道编码和解码是对传输信号进行编码和解码以提高传输可靠性和数据安全性。
第三章:现代通信系统的信号处理方法3.1 数字信号处理技术数字信号处理技术是将信号转化为数字信号进行处理的技术,主要包括数字滤波、数字信号处理、数字信号编码和解码等。
数字信号处理技术具有精度高、可重复、可编程、抗干扰能力强等优点,可以实现信号传输质量的稳定、高效、快速等特点。
3.2 常用的信号处理方法常用的信号处理方法包括模拟信号处理和数字信号处理两种。
模拟信号处理是将连续时间信号进行处理的技术,主要包括模拟滤波、模拟信号处理、模拟信号编码和解码等。
模拟信号处理技术具有处理速度快、实时性好等优点,但受到噪声干扰影响较大,容易出现误差和失真等问题。
数字信号处理技术具有处理精度高、可重复、可编程、抗干扰能力强等优点,但对处理器要求较高,处理速度较慢。
3.3 现代通信系统中的信号处理方法现代通信系统中的信号处理方法包括数字信号处理、模拟信号处理、混合信号处理等。
其中,数字信号处理技术被广泛应用于无线通信、卫星通信、光纤通信和数字电视等领域。
而模拟信号处理技术则主要应用于音频信号处理、图像处理和电力信号处理等领域。
Unit EightText II. Writing SkillsThis is a short, simple and straightforward piece of persuasive writing, informal style is used.nguage Points1.enjoy①enjoy (v.)②enjoyable (adj.)③enjoyment (n.)eg: We enjoy books very much.Books are enjoyable.We find great enjoyment in books.He is enjoying a book.Wrong: 1. Books are enjoying.2. We are enjoyed at the books.2. be aware of ----realizebe unaware ofPar:1) He knows very well the danger.2) He doesn't realize the danger he is facing.3) Do you know the result of the matter?4) She didn't know what was happing.3.resistible①resistible (adj.) -- that can be resistedeg: This wish to get more money is resistible.irresistible --- that can not be resistedeg: His wish to get more money is resistible, so he tries to steal.②resist (v.)--- oppose; keep oneself back frombe undamaged or unaffected by抵抗; 对抗; 不屈服于, 忍耐; 不受…的影响a)opposeeg: The country was unable to resist the invasion.She can't resist the temptation. …的诱惑They have the right to resist.b) keep oneself back fromeg: She could not resist his charms.I can't resist the wish to see him.c) undamaged or unaffected by…eg: This material resists fire.③resistance (n.) --- [u] power of resisting ; opposing power 抵抗; 抵抗力; 阻力;eg: The enemy offered very little resistance.The enemy's resistance was completely destroyed.There is much resistance to the new law.Copper has less resistance to electricity than many other metals.Healthy people have more resistance to disease than weak people.④resistant (adj.) --- offering resistance 抵抗的; 有抵抗力的; 反抗的;be resistant to…eg: Some insects are resistant to DDT.She is not resistant to disease.4.end up with --- finish ... in the end.Par:In the end, I failed in the exam. (I ended up with failure in the exam.In the end, I left much work undone. (I ended up with much work undone.)5.engross①engross (v.) --- take up all the time or attention of 花费所有的时间和精力(usu. used in passive.) 通常用于被动be engrossed in... 全神贯注于...eg: He is engrossed in his work.Par: He is reading a book attentively.We should concentrate ourselves on English study.②engrossing --- attractive 引人入胜的eg: It is an engrossing story.6. reality n. [u] [c] --- the quality of being real; real existence; sth real;sth actually seen.eg: Don't escape realities of our every day life.in reality--- in fact; reallyeg; In reality, he is a good teacher.7.content①content n. [u] the condition of being satisfied 满足live in content 心满意足eg: Now she is living in content.Do you live in content?to one's heart's content --- being completely satisfied.eg: We can swim in the river to our heart's content.The children enjoyed themselves to their heart's content.Par: When children are allowed to watch TV, they are completely satisfied to watch TV. (Children are allowed to watch TV to their heart's content.)Children are eating happily.The boys are dancing happily.②content (adj.) (不做定语) --- satisfied with what one has 满足的; 满意的be content with...eg: I'm content with my salary now.He is not content with beautiful dreams, he wants beautiful realities.be content to do sth.eg: He is content to eat the leftovers.I'm content to stay here.③content (v.) --- make content; satisfy 使满足to content sb.eg: Simple praise can content him.Par:60 marks can satisfy him.Nothing can make her satisfied.* content oneself with --- be satisfied with ...= be contented withPar:We are satisfied with our success.He is satisfied with his job.④contented adj. --- satisfied; showing or feeling satisfied满足的; 表示满意的;* 做定语:eg: He was speaking with a contented look.(smile)* 做表语: be contented (with)... --- be satisfied = be content witheg; Some people are never contented.He seems quite contented with his with his life.⑤contentedly (adv.) --- happilyeg: He went to bed contentedly.c.f. `content the content of the bag8. inevitable①inevitable (adj.) --- that can not be avoided; that is sure to happen 不可避免的eg: When you break a bone, what is inevitable? (Pain is inevitable)Par:Accident will sooner or later happen if you drive carelessly.Traffic delays always occur at week-ends.Mistake can not be avoided in dictations.②inevitably (adv.)eg: Mistakes occur inevitably in our study.9. browse①browse (vi.) --- read parts of the books without any definite plan,for interest or enjoyment 浏览书籍, 随便阅读eg: Do you browse through/among books in a bookstore?I often browse among books in a bookstore?②browse (n.) (act, period of) browsing 浏览, 浏览的啪have a good browsing (among books)浏览很长时间eg: Do you have a good browse when you go to a bookshop?10. discreet①discreet (adj.) --- careful, tactful, prudent 小心的, 懂读的;eg: a discreet personHe kept a discreet silence. (保持深重的沉默)②discreetly (adv.)eg: He drives discreetly.11. illustrate①illustrate (vt.)a) explain by examples or pictures (通过距离或图表说明)Par:The teacher explained the sentence striationHe illustrated his point by relating his own experience.He tried to explained his meaning.How he did explain his kindness.b) supply ((a book, article) with pictures or diagramseg: The artist illustrated the book with pen-and-ink drawings.(给书等配入插图) Par:I'll illustrate the book with picture.This book is well-supplied with pictures.It is a well illustrated text-book.②illustration (n.)a) illustrating or being illustrated; explanation with picturesPar: Give me an explanation (Give me an illustrator)以图表距离说明The teacher said it as an explanation (illustration) of the boy's poor work.He gave me an explanation(illustration) of the sentence pattern.in illustration of... --- in order to illustrate...Par: In order to illustrate the story, he used some examples.In order to illustrate the theory, he used some pictures.b) [c] sth. or pictures or diagrams that illustration 例子, 插图, 图表eg: Are there any illustrations on this page?I like magazines full of illustrations.by way of illustration作为...的例子eg: I mentioned it by ways of illustration.③illustrative (adj.) --- as an explanation or example of sth. 说明的, 作为例证的These words are illustrative.There are illustrative examples.12. indulgent①indulgent (adj.)--- inclined to give kind to (对...放纵; 溺爱)eg: He is an indulgent father.Indulgent parents are those who easily agree to let children do what they like.Is an indulgent teacher a good teacher?②indulge(vt.) --- gratify; give way to and satisfy(使满足; 纵容; 耽溺; 纵情; 顺从)eg: Do you think it is necessary to indulge a child?Is a teacher who indulges students a good teacher?Many rich people indulge their children.I indulge my interest in flowers. (Do I resist my interest?)indulge (oneself) in --- allow (oneself) to enjoy容许自己享受, 尽情eg: He sometimes indulges himself in a cigarette.Par:He allowed himself to have an expensive meal.We allow ourselves to have a long sheep on Sunday.(vi.)indulge ineg: He indulges in gambling.③indulgence (n.)[u] indulging; the state of being indulged 放纵; 沉溺; 纵容eg: Indulgence in smoking/drink can harm your health.Indulgence in gambling will spoil you.[c] sth one allow him to enjoy 允许自己享受的东西eg: One of my indulgences is having breakfast in bed.What is you indulgence?13. beckon v. --- call sb's attention by a movement of the hand or arm, usu.to show that he is to come nearer or to follow招手令他人走近或跟着来beckon sb. to do sth. 招手让...做...eg: The teachers beckoned others to follow him.Par:The police made a signal to ask the man to go quicker.The teacher made a signal to show the student to stop reading.beckon sb. in/on/out/forward/to sb's sideeg: He beckoned me in.He stood waiting until the policeman beckoned him on.Par: The teacher signaled me to come in.The man signaled the woman to walk forward.The policeman signaled me to go out.The man signaled me to go to his side.14. tell sb. off (for...) --- scold sbeg: He told me off for taking away the newspaper.15. tuck①tuck (v.)a) tuck (away) --- store in a safe place 将...藏起来Par: She put her dress at the button of the case.Grandfather had may old bottles put in the cellar.The map is put in the pocket.b). ---- to draw together into a small space; put into a desired or convenientplace. 缩拢; 塞置于方便之处eg: He tucked up his sleeves.When you swim, you tuck the end of your hair into your bathing-hat.Do you often tuck your shirt into your trousers?②tuck (n.) stitched fold of material in a garment (衣服的)摺等She is making a tuck in a dress.(打褶)Her dress has tucks in the sleeves.III. Questions on Text I1. Is the time spent in a bookshop very pleasant?2. Why is the time spent in a bookshop enjoyable?3. What kind of place can make people escape the realities of everyday life?4. What can people do in a bookshop or a music shop?5. Is it necessary for the assistants to greet the people who enter the bookshop?6. When do people need an assistant in a bookshop?7. Is it easy for people to become engrossed in books?8. Are people easily tempted to buy books?9. Must book sellers be patient and kind?10. Do people rend books in a bookshop?11. What kind of people often rend books in a bookshop?12. Was the book seller very kind to the identical student in this text?13. Was the book seller so kind that he kept the book in safe place in order that nobodywould buy it? (for the medical student to read?)14. Had the medical student expected to be treated with such kindness?VI. Translation1. 请你把自行车放到走廊里, 以免日晒雨淋. (get shelter from)2. 有时候, 想买某种东西的愿望是压抑不住的.3. 当你参观中国出口商品交易会的时候, 你可以欣赏各种商品, 直到心满意足为止.4. 沉迷于赌博的人是不会有所作为的.5. 请把这本书房在较安全的地方, 以免读者们随意拿走.6. 为了解释这个问题, 老师举了很多例子.(in illustration of)7. 我已经很满足现在的生活.8. 他唱着歌, 脸上挂着满意的笑容. (with a contented smile on his face)9. 在我们的学习和生活中, 犯错误是不可避免的, 最重要的认识错误和改正错误.10. 我很喜欢在星期天到广州各大书店浏览各种书籍, 这也可以说是一种我允许自己享受的东西.(Suggested key:)1.Please put your bike in the corridor to get shelter from the sun and the rain.2.Sometimes the temptation to buy something is irresistible.3.When you visit the Chinese Export Commodities Fair, you can enjoy all kinds of products toyour heart’s content.4.Those who indulge in gambling will never be promising.5.Please tuck away the book in a safe place in case the readers take it away at will.6.In illustration of this matter/issue, the teacher gave a lot of examples.7.I am content/contented with the present life.8.He is singing, with a contented smile on his face.9.In our study and daily life, it is inevitable for us to make mistakes. The most important thingis to realize the mistakes and correct them.10.I like to browse among books in big bookshops on Sundays and this is one of myindulgences.)VII. Questions on Text II:1.Are those people who buy second-hand goods mean?2.Why do people usually buy second-hand goods?3.Which book can tell you the markets of second-hand goods? (beginners guide)4.Do second-hand goods have a guarantee?5.What kind of second-hand books worth keeping?。
第三章移动通信的信号处理技术(本章部分内容为教材第四章)第一节、语音编码技术第二节、均衡技术第三节、分集技术第四节、交织与信道编码技术第一节、语音编码技术一. 语音编码概念二.波形编码基本原理三.参量编码基本原理四.混合编码技术“我爱北京天安门”波形语音波形“中国”语音波形语音波形“国”字语音波形语音波形“国”部分语音波形●语音、图像属模拟信号范畴。
●语音、图像通过编码实现数字化是必然趋势。
●数字化的语音和图像需要用较高的数码率,需占用较大的带宽和存储空间。
●压缩数字化语音和图像信号的数码率是实现语音和图像通信数字化的关键。
●编码技术的核心就是研究压缩编码算法.用尽可能低的数码率获得尽可能好的语音和图像质量。
人耳听觉特性-2人耳听觉特性-3一. 语音编码概念移动通信对语音编码的要求是:(1) 编码的速率要适合在移动信道内传输,纯编码速率应低于16kbit/s。
(2) 在一定编码速率下语音质量应尽可能高,即解码后的复原语音的保真度要高,主观评分MOS(Mean Opinion Score)应不低于3.5分(按长途语音质量要求)。
(3) 编解码时延要短,总时延不得超过65ms。
(4) 要能适应衰落信道的传输,即抗误码性能要好,以保持较好的语音质量。
(5) 算法的复杂程度要适中,应易于大规模电路集成。
(6)功耗小,便于应用于手持机语音评价客观评定方法用客观测量的手段来评价语音编码的质量,常用的方法有信噪比、加权信噪比、平均分段信噪比等。
主观评定方法是主观评定等级(Subjective Opinion Scale ),或称平均评定得分(MOS )。
MOS 得分采用五级评分标准,其方法是由数十名试听者在相同信道环境中试听并给予评分,然后对评分进行统计处理,求出平均得分。
即使努力去听,也很难听懂1劣需要集中注意力2差中等程度的注意力3满意(正常)需要注意,但不需要明显集中注意力4良可完全放松,不需要注意力5优收听注意力等级分数质量等级主观评定等级语音编码:为信源编码,移动通信数字化的基础第1/2代蜂窝系统的根本区别语音压缩编码的目的:在保持一定复杂程度和通信时延的前提下,使用尽可能少的信道容量,传送尽可能高质量的语音。
通信信号处理与调制技术概述通信信号处理与调制技术是现代通信系统中至关重要的一部分。
这些技术涉及在信号传输过程中对信号进行处理和调制,以实现高效、可靠的数据传输。
本文将介绍通信信号处理与调制技术的基本原理、常用的调制方法以及其在不同领域的应用。
一、通信信号处理技术1. 数字信号处理数字信号处理(Digital Signal Processing,DSP)是将连续时间的信号转化为离散时间的信号并对其进行处理的技术。
在通信系统中,数字信号处理常被用于提取和恢复信号、实现滤波器和调制解调器等功能。
常见的数字信号处理算法包括傅里叶变换、滤波器设计和数据压缩等。
2. 模拟信号处理模拟信号处理(Analog Signal Processing)是对连续时间的信号进行处理的技术。
模拟信号处理通常涉及信号的放大、滤波及混频等操作。
尽管数字信号处理技术已经在通信领域得到广泛应用,但模拟信号处理在某些特定场景下仍然具有重要意义,如高频信号的处理和调制。
二、调制技术1. 调制原理调制是将要传输的信息信号通过调制技术转换为适合传输的载波信号的过程。
在调制中,信息信号被调制到载波信号上的某个特定频率范围内。
这样做的目的是提高信号传输的可靠性和抗干扰能力。
常用的调制方法包括幅度调制(AM)、频率调制(FM)、相位调制(PM)等。
2. AM调制AM调制是将信息信号的振幅变化反映到载波信号上的调制技术。
AM调制广泛应用于调幅广播、短波通信等领域。
它的主要特点是简单、成本低廉,但对噪声和干扰较为敏感。
3. FM调制FM调制是将信息信号的频率变化反映到载波信号上的调制技术。
FM调制通常用于广播电台、卫星通信等领域。
相比于AM调制,FM调制具有更好的抗噪声和干扰能力,但相对复杂一些。
4. PM调制PM调制是将信息信号的相位变化反映到载波信号上的调制技术。
PM调制常应用于音频信号的传输以及无线电导航等领域。
它对于抗噪声性能要求较高,但实现难度相对较大。