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现代通信原理课件(英文版)

现代通信原理课件(英文版)


8
1.2 Digital and Analog source and system
• The generation of communication system
Information input m(t)
Signal processing
Carrier circuits
Transmitter
channel noise
19
1.2 Digital and Analog source and system
• Classification of communication patterm • Peer to peer communication :
simplex; half duplex; duplex • Parallel transmitting communication • Series transmitting communication
information from a analog source to the intended receiver(sink)
21
1.3 Deterministic and Random waveforms
1) Deterministic waveform It can be modeled as a completely specified function of time
现代通信原理课件Chapter One
1
Chapter One
Introduction
Why? Information Age Information Superhighway
2
Chapter One Application
military application; common application;
通信原理(英文版)

通信原理(英文版)

Chapter 2 Signals
2.1 Classification of Signals
2.1.1 Deterministic signals and random signals
• What is deterministic signal? • What is random signal?
2.1.2 Energy signals and power signals
f (t) f (t T) t
Its frequency spectrum is
/2
C( jn0 )

1 T
/ 2 Ve j n0t dt
/ 2

1 T

V
jn 0
e
j n0 t

/ 2

V e j n0 / 2 e j n0 / 2
f (t) sin(t) Its frequency spefct(rtu)m: f (t 1)
0 t 1 t
C(
jn 0 )

1 T0
T0 / 2 s(t )e jn0t dt
T0 / 2
1 sin(t )e j 2nt dt
Solution: Let the expression of the rectangular pulse be
Then its frequency spectral density is
its
Fourier
tragns(fto)rm:
1
0
t /2 t /2
G() / 2 e jt dt 1 (e j / 2 e j / 2 ) sin( / 2)
现代通信原理课件(英文版)(ppt 35页)

现代通信原理课件(英文版)(ppt 35页)

are defined on continuum. 4. Digital communication system transfers information
from a digital source to the intended receiver(sink) 5. Analog communication system transfers
2) Note: The general principles of digital and analog modulation apply to all types of channels, although channel characteristics may impose constraints that favor a particular type of signaling
15
1.2 Digital and Analog source and system
2 the advantage of digital system
1）Relatively inexpensive digital circuits may be used
2） Privacy is preserved by using data encryption
8
1.2 Digital and Analog source and system
• The generation of communication system
Information input m(t)
Signal processing
Carrier circuits
Transmitter
channel noise
1. Selection of the information-bearing
通信原理(英文版)

通信原理(英文版)

6
【Example 2.4】Find the waveform and the frequency spectral density of a sample function. Solution: The definition of the sample function is
sin t Sa ( t ) t
d(t)
1
(f)
0
t
0
f
meaning of d function: It is a pulse with infinite height, infinitesimal width, and unit area. Sa(t) has the following property:
Physical
F ( ) lim
/2 / 2
cos 0 te
jt
sin[( 0 ) / 2] sin[( 0 ) / 2] dt lim 2 ( ) / 2 ( ) / 2 0 0


The frequency spectral density of d(t):
( f ) d (t )e
jt
d (t ) 0
t 0

dt 1 d (t )dt 1

7
d(t)
and its frequency spectral density:
f (t ) f (t 1) t
1
Its frequency spectrum:
1 C ( jn 0 ) T0

T0 / 2
T0 / 2
s(t )e
通信原理 张水英版课件

通信原理 张水英版课件

4
通信发展概况
2. 近代：
1837年：莫尔斯发明电报系统。 1876年：贝尔发明电话。
5
通信发展概况
3.现代 20世纪60年代以后：
数字通信技术进入高速发展阶段。
近20多年：
数字通信迅猛发展； 光纤通信也携手同行。 两者都成为现代通行网的主要支柱。
6
通信发展概况
塞缪尔·莫尔斯 （Samuel
Finley Breese Morse
44
【例如】
有一个4PSK数字通信系统，现传输 20个码元，其中错了2个码元，那 么误码率为10%；如果每个错误码 元有一个比特错误，那么误比特率 为5%；如果每个错误码元有两个比 特错误，那么误比特率为10%；
45
【例如】
已知某四进制数字传输系统的信息传 输速率为2400（bit/s），接收端在 半小时内共收到216个错误码元，试 计算该系统的误码率。
缺点：
占用频带宽 对同步要求高、系统和设备比较复杂
17
1.3 通信系统的分类及通信方式
一、通信系统的分类
按消息的物理特征 按调制方式 按信号特征 按传输媒介 按复用方式
18
1、按消息的物理特征
电报通信系统 电话通信系统 数据通信系统 图像通信系统
。 。 。 。
19
2、按调制方式分类
基带传输：将未经调制的信号直接传送，
第1章
绪论
内容
1.1 通信的基本概念 1.2 通信系统的模型 1.3 通信系统分类及通信方式 1.4 信息的度量 1.5 通信系统的主要性能指标
2
1.1 通信的基本概念
消息、信息和信号 通信 通信发展概况
3
通信发展概况
1. 古代：
通信原理(英文版)

通信原理(英文版)


can be generalized to power signal.
10
Energy spectral density
Let the energy of an energy signal s(t) be E, then the energy
of
the
signal
is
decided
byE

s2 (t)dt
is
S() s(t)e jt dt
The inverse Fourier transform of S() is the original signal:
s(t) S ()e jtd
【Example 2.3】Find the frequency spectral density of a rectangular pulse.
0, 当t 0,
u(t)


1,
当t 0
1
u(t) = d(t)
0
Fig. 2.2.6 Unit step function
t
➢ Difference between frequency spectral density S(f) of
energy signal and frequency spectrum of periodic power
Chapter 2 Signals
2.1 Classification of Signals
2.1.1 Deterministic signals and random signals
➢ What is deterministic signal? ➢ What is random signal?
通信原理(数字通信)PCM(41页英文ppt)

通信原理(数字通信)PCM(41页英文ppt)

6/41
A First Course in Digital Communications
Chapter 4: Sampling and Quantization
Sampling Theorem
Theorem A signal having no frequency components above W Hertz is completely described by specifying the values of the signal at periodic time instants that are separated by at most 1/2W seconds. fs ≥ 2W is known as the Nyquist criterion, the sampling rate fs = 2W is called the Nyquist rate and its reciprocal called the Nyquist interval. Ideal sampling is not practical ⇒ Need practical sampling methods.
Sampling: How many samples per second are needed to exactly represent the signal and how to reconstruct the analog message from the samples? Quantization: To represent the sample value by a digital symbol chosen from a finite set. What is the choice of a discrete set of amplitudes to represent the continuous range of possible amplitudes and how to measure the distortion due to quantization? Encoding: Map the quantized signal sample into a string of digital, typically binary, symbols.
通信原理(英文版)

通信原理(英文版)

# For an equal probability binary symbol:
I = log2 [1/P(x)] = log2 [1/(1/2)] = 1 bit
4
# For an equal probability M-ary symbol:
I = log2 [1/P(x)] = log2 [1/(1/M)] = log2 M bit If M = 2k ，then I = k bit
Out put S/N increases with bandwidth according to exponential law.
10
Digital communication system model 11
2
1.2 Message, information & signal
Message：speech, letters, figures, images…
Information：effective content of message. Different types of messages may contain the same information
5
1.3 Digital Communication
1.3.1 Basic concept
Two categories of signals • Analog signal：Its voltage or current
can be expressed by a continuous function of time. For example, speech signal.
# Ex: “Rainfall will be 1 mm tomorrow” – information content small
通信原理(英文版)总复习

通信原理(英文版)总复习


PY ( f ) = H ( f ) PX ( f )
2
14
σ
2
【Example 1】 Assume Y (t ) = X cos ω t − X sin ω t is a random process, where X1 and X2 are statistically independent Gaussian random variables, and their mathematical expectations are 0, variances are σ . Find: (1) E[Y(t)]、E[Y2(t)] E[Y(t)]、 (2) The probability distribution density of Y(t) (3) R(t1，t2)
equat or
5
Channel models：
Modulation channel model Coding channel model
4. Noise in Channel
6
【Example 1】 Assume a signal source produces 4-ary signals with equal probability, 4and the width of its symbol is 125 µ s . Find its symbol rate and information rate.
17
AM
m′(t) ′ 1+m′(t) ′
+1=
1+m′(t) ′
1 0
1 0
×
=
18
Frequency density
m(t) M(f) t
⇔
-fm
通信原理-英文版分析

通信原理-英文版分析


Fig. 1.3.2 Distortion and restoration of digital signal waveforms
9
Error correcting techniques can be used. Digital encryption can be used. Different kinds of analog & digital
Principles of Communications
1
Chapter 1 Introduction 1.1 Historical Review of Communication
Origin of ancient communication Two modes of communication Development of modern communication
5
1.3 Digital Communication
1.3.1 Basic concept
Two categories of signals • Analog signal：Its voltage or current
can be expressed by a continuous function. For example, speech signal.
• Digital communication system Requirement － correct decision Criterion － Error probability Basic issur － statistical decision theory
8
1.3.2 Advantages of Digital Communication
Out put S/N increases with bandwidth according to exponential law.
通信原理英文

通信原理英文


(MF)
direction-finding, distress calling, coast guard
17
Division of frequency band
Frequency band (MHz)
3 – 30
30 – 300
300 – 3000
Name
Typical application
High frequency (HF)
# Ex: “Rainfall will be 1 mm tomorrow” – information content small
“Rainfall will be 1 m tomorrow” – information content large
“The sun will rise in the east tomorrow morning” – information content equals zero # Information content I = I [ P(x) ]，P(x) – Occurrence probability # Definition：I = loga [1/P(x)] = -logaP(x) # Usually, set a = 2, the unit of the information content will be called a bit.
5
1.3 Digital Communication
1.3.1 Basic concept
Two categories of signals • Analog signal：Its voltage or current
can be expressed by a continuous function of time. For example, speech signal.

通信原理英文版教学设计

Communication Principles - English Version Teaching Design IntroductionCommunication principles are an essential part of any telecommunication system. This English version teaching design focuses on providing students with a solid conceptual framework for understanding the fundamental principles of communication. The program’s learning objectives include developing the student’s ability to:•Familiarize with the communication system architecture•Understand basic communication signals and signal processing techniques•Analyze the key features of various modulation techniques•Develop a deep understanding of the operational principle of encryption techniquesCourse OutlineThe course consists of fifteen topics with a total of 45 hours of instruction time. Below is a detled overview of the topics covered in the class.Topic 1: Overview of Communication System Architecture •Introduction to communication•Essential elements of communication systems•Communication system architecture•Overview of communication system componentsTopic 2: Signals and Signal Processing Techniques •Introduction to signals and signal processing techniques•Analog Signals and Digital Signals•Fourier Series and Fourier Transform•Sampling and Quantization•Modulation and DemodulationTopic 3: Amplitude Modulation (AM)•Introduction to Amplitude Modulation (AM)•Time-domn description•Frequency-domn description•Modulation index•Double sideband, full carrier (DSB-FC) and double sideband, suppressed carrier (DSB-SC) AMTopic 4: Angle Modulation•Introduction to Angle Modulation•Types of Angle Modulation•Phase Modulation (PM)•Frequency Modulation (FM)•Comparison between FM and AMTopic 5: Pulse Modulation Techniques•Introduction to Pulse Modulation Techniques•Types of Pulse Modulation Techniques•Pulse Amplitude Modulation (PAM)•Pulse Width Modulation (PWM)•Pulse Position Modulation (PPM)Topic 6: Spread Spectrum Techniques•Introduction to Spread Spectrum techniques•Types of Spread Spectrum Techniques•Direct Sequence Spread Spectrum (DSSS)•Frequency Hopping Spread Spectrum (FHSS) Topic 7: Digital Modulation Techniques•Introduction to Digital Modulation Techniques •Types of Digital Modulation Techniques•Amplitude Shift Keying (ASK)•Frequency Shift Keying (FSK)•Phase Shift Keying (PSK)•Quadrature Amplitude Modulation (QAM)Topic 8: Error Detection and Correction Methods •Introduction to Error Detection and Correction Methods•Types of Error Detection and Correction Methods •Block and Convolutional Codes•Cyclic Codes and Hamming Codes•Forward Error Correction (FEC)Topic 9: Encryption Techniques•Introduction to Encryption Techniques•Types of Encryption Techniques•Symmetric Encryption•Asymmetric Encryption•Digital Signature and Public Key Infrastructure (PKI)Topic 10: Communication Channel•Introduction to the Communication Channel•Types of Communication Channels•Analog and Digital Communication Channels•Noise Introduction and Characteristics of Noise •Channel CapacityTopic 11: Multiple Access Techniques•Introduction to Multiple Access Techniques•Types of Multiple Access Techniques•Frequency Division Multiple Access (FDMA)•Time Division Multiple Access (TDMA)•Code Division Multiple Access (CDMA)Topic 12: Data Transmission•Introduction to Data Transmission•Data Transmission Modes•Synchronous and Asynchronous Transmission•Error Control and Flow Control Techniques Topic 13: Analog to Digital Conversion and Digital to Analog Conversion•Introduction to Analog to Digital Conversion and Digital to Analog Conversion•Types of Analog-Digital Conversion Techniques•Sampling and Quantization Error•Reconstruction Filter•Digital-to-Analog Conversion Techniques Topic 14: Introduction to Wireless Communication•Introduction to Wireless Communication•Basic of Wireless Communication system•Cellular system architecture•Wireless Modulation SchemeTopic 15: Advanced Topics•Introduction to Advanced Topics in Communications•Optical Communication•Satellite Communication•Ad-Hoc Networking•Next-generation NetworksTeaching StrategiesThe teaching style of this course emphasizes practical problem-solving exercises and interactive group activities. The following teaching strategies are employed in the course: •Classroom lectures•Interactive class discussions•Group activities•Audio-visual presentations•Case studies and problem-solving exercises•Guest lecturesConclusionThe Communication Principles English version teaching design provides a comprehensive approach to learning the fundamental principles of communication. Students will gn insight into the communication system architecture, essential signal processing techniques and various digital modulation schemes. The course prepares learners’ to understand the intricacies of designing communication systems and prepares them for future studies in the field of electronic communication.。

通信原理(英文版)课件

A protocol used to establish a direct connection between two points, often used for dial-up internet access.
Network Security
• Firewalls: Devices that filter incoming and outgoing traffic based on security policies to protect against unauthorized access or malicious attacks.
Modulation and Demodulation
Modulation
The process of varying a property of a carrier wave, such as its amplitude, frequency, or phase, in accordance with the information to be transmitted. This allows information to be carried over long distances through various media.
Channel Capacity and Data Rate
Channel Capacity
The maximum amount of information that can be transmitted over a communication channel without loss of data or degradation in signal quality. It is typically limited by the physical properties of the channel and the noise level present.

通信原理英文版教学课件：class six-2ASK

式中， Ps(f) － pPosw( fe)r sp14ecPtAra( lf denf0s)ityPoAf(sf(t) f0 )
PA(f) － power spectral density of A(t)
∴If PA(f) has been found, then Ps(f) can be calculated by substituting PA(f) int the above equation.
Therefore the mean power of the output noise of the bandpass filter is:
Hence its output signal to nno2 isen0rBati1o.9i2s: 10 8 W
∴（1）the
r symbol
A2
106
1
1
erf
4
ha
2 n
1
1
erf
4
h
2
n
When h equals the optimum threshold h*,
p1(x*) p0 (x*)
Pe
1 erfc 2
r /2
When r>>1,
Pe
1 er / 4
r
13
Envelope detection
∵ The output is the envelope of its input voltage y(t), we have
∴When 1 is transmitted, the probability of x(t) is
p1(x)
1
2
n
exp
(x
A) 2

通信原理课件

჉೵੏လܹᆓ 6RXWKZHVW -LDRWRQJ 8QLYHUVLW\ -4-
ɴҷỞֵॳˊ ciple of Modern Communications
ഀ߻ຬ(Twisted Pair)
A twisted pair consists of two insulated copper wires, typically about 1 mm thick. The wires are twisted together in a helical form, just like a DNA molecule. Twisting is done because two parallel wires constitute a fine antenna. When the wires are twisted, the waves from different twists cancel out, so the wire radiates less effectively.
჉೵੏လܹᆓ 6RXWKZHVW -LDRWRQJ 8QLYHUVLW\ -5-
ɴҷỞֵॳˊ Principle of Modern Communications
ઝఘඔྑ
0 1 2 3 4 5 6 7 8 9 10 11 12
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ԛసჃ ໰ԁူႎಒ
Chapter 3 Channel and Noise
3.1 3.2 3.3 3.4 3.5 3.6
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8Principles of Communications

Principles of Communications通信原理1、communication system mode l通信系统模型信源发送设备信道接收设备信宿Source T ransmitter channel receiver sink噪声源noise sourceThe function of T ransmitter is to generate a signal suitable for transmission over a channel.A channel is a physical medium used to transmit signals from T ransmitter to receiver.like wires,fiber-optical cable，space.The function of receiver is to amplify and invert the signal and restore the original electrical signal.发送设备的作用是产生合适于在信道中传输的信号。

信道是一种物理媒质，用来将来自发送设备的信号传送到接收端。

如电线、光纤电缆、空间。

接收设备的功能是将信号放大和反变换，恢复出原始的电信号。

2、Analog communication system:it is a communication system that uses analog signals to transmit information;Digital communication system:it is the use of digital signals to transmit information communication system;The technical problems involved in digital communication mainly include source coding and decoding,channel coding and decoding,digital modulation and demodulation,etc.模拟通信系统：它是利用模拟信号来传递信息的通信系统；数字通信系统：它是利用数字信号来传递信息的通信系统；数字通信涉及的技术问题主要有信源编码与译码、信道编码与译码、数字调制与解调等。

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T
0
n 2 (t )dt
2

k dimensional combined probability density function of the received voltage r(t) = s(t) + n(t) When the symbol 0 is transmitted
f 0 (r )
f ( n)
where n f 0 H
2 n

2 n

k
exp n0

0
n 2 (t )dt
f (n) f k (n1 , n2 , , nk ) f (n1 ) f (n2 ) f (nk )

Note that f (n) is not a function of time. n is a k dimensional quantity, which can be regarded as a point on the k dimensional space. f (n) is decided only by the noise energy


The meaning of “optimum” － minimum error probability Decision rule for optimum receiving Received vector r may be regarded as a point in a k dimensional space. The k dimensional space can be partitioned into two regions:A0 and A1
f (ni ) ni2 exp 2 2 2 n n 1

where n － standard deviation of the noise n2 － variance of the noise
1

k dimensional combined probability density function of noise sample voltage
Chapter 8 Optimum Receiving of Digital Signal
8.1 Statistical Characteristics of Digital Signal
Assume the highest transmission frequency of the communication system is fH , and the received voltage is expressed by its sample. One dimensional probability density of the noise sample voltage If the voltage is sampled at the sampling rate 2fH in a symbol interval; then k samples are obtained: n1, n2, …, ni, …, nk , and each sample is a random variable with normal distribution. Its one dimensional probability density can be written as
f1 ( r )

1 2 n

k
1 exp n0
0 r (t ) s1 (t ) dt
T 2

where s1 (t) － signal waveform of the transmitted symbol 1
3
8.2 Optimum Receiving Criterion of Digital Signal
f k (n1 , n2 , , nk ) f (n1 ) f (n2 ) f (nk )


1 2 n

k
1 exp 2 2 n
ቤተ መጻሕፍቲ ባይዱ
ni2 i 1
k
Average power of the received noise in a symbol duration T: k k 1 k 2 1 1 T 2 1 2 ni 2 f T ni or T 0 n (t )dt 2 f T ni2 k i 1 i 1 H i 1 H Substituting the above equation into the uppermost equation, we obtain 1 T 1

1 2 n

k
1 exp n0
0 r (t ) s0 (t ) dt
T 2

where r (t) － sum of the signal and noise voltages s0 (t) － signal waveform of the transmitted symbol 0 When the symbol 1 is transmitted
A0 A
0
A1
A1

Decision rule: If the received vector r falls into the region A0, then the decision is symbol o transmitted; If the received vector r falls into the region A1, then the decision is symbol o transmitted;
4

Total symbol error probability:
Pe P(1) P( A0 / 1) P(0) P( A1 / 0)
where
P( A0 / 1) f1 (r )dr － conditional probability of
A0
the vector r fallen in region A0 when 1 is transmitted