通信原理讲义-英文版
通信原理 英文
通信原理英文Communication PrinciplesCommunication principles refer to the fundamental concepts and theories that govern the process of transmitting information from one entity to another. These principles form the foundation of effective communication and play a crucial role in various communication systems, such as wireless communication, optical communication, and digital communication.One of the key communication principles is the concept of encoding and decoding. Encoding involves converting the information into a suitable form for transmission, while decoding involves the reverse process of converting the received signals back into meaningful information. This principle ensures that the information is accurately transmitted and understood by the receiving entity.Another important principle is the concept of modulation. Modulation is the process of modifying a carrier signal by varying its amplitude, frequency, or phase to carry the information. This principle is used in various communication systems to transmit information over long distances without significant loss or distortion.Furthermore, the principle of noise reduction is crucial in communication systems. Noise refers to any unwanted disturbance that affects the quality of the transmitted signal. To ensure reliable and clear communication, noise reduction techniques, such as filtering and error correction, are employed to minimize the impactof noise on the received signals.Additionally, the principle of multiplexing allows multiple signals to be transmitted over a single communication channel. This is achieved by dividing the channel bandwidth into smaller sub-channels, each carrying a different signal. Multiplexing enables efficient utilization of the available communication resources and allows for simultaneous transmission of multiple signals.Furthermore, the principle of synchronization is essential for successful communication. Synchronization ensures that the transmitting and receiving entities are operating in a coordinated manner, allowing for accurate transmission and reception of the information. Various techniques, such as clock synchronization and frame synchronization, are employed to achieve synchronization in communication systems.Lastly, the principle of error detection and correction is crucial for reliable communication. Error detection techniques, such as checksums and parity bits, are used to identify errors in the transmitted signals. Error correction techniques, such as forward error correction codes, are employed to correct the detected errors and ensure accurate transmission and reception of the information. In summary, communication principles are fundamental concepts and theories that govern the process of transmitting information. These principles, such as encoding and decoding, modulation, noise reduction, multiplexing, synchronization, and error detection and correction, ensure efficient and reliable communication in various communication systems.。
通信原理(英文版)
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)
通信原理(英文版)3精品名师资料
c(t ) A cos(0t 0 )
where, A --- amplitude
Modulating signal m(t)
Modulator
Modulated signal s(t)
0 --- angular frequency
Figure 3.1.1 Modulator
of carrier 0 --- initial phase Definition: Modulating signal m(t) －signal from the source Modulated signal s(t) － signal after being modulated Modulator － the device for modulation
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3.2 Linear modulation
3.2.0 Basic concept Assume: the carrier is: c(t) = Acos0 t = Acos2 f0t
modulating signal is a energy signal m(t), its spectrum is M(f ) s (t ) carrier: c(t) Modulated Modulating H(f) signal signal multiplication result: s(t) s(t) m(t) Acos t filter output: s(t) “” is used to express Fourier transform: m(t ) M ( f )
Chapter 3 Analog modulation system
3.1 Introduction
演示文稿通信原理英文版
1.3.2 Advantages of Digital Communication
1.2 Message, information & signal
Message：speech, letters, figures, images…
Information：effective content of message. Different types of messages may contain the same information
Finite number of possible values of signals Correct decision may be achieved
(a) Waveforms of distored digital signal
(b) Waveforms of digital signal after shaping
Signal：the carrier of message
What transmitted in a communication system is signal.
Measurement of information：
# “quantity of message” information content
1.3 Digital Communication
1.3.1 Basic concept
Two categories of signals • Analog signal：Its voltage or current
现代通信原理课件(英文版)(ppt 35页)
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
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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
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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)11[63页]
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➢Advantage of OQPSK:
Max. difference between adjacent symbols is only 90º. ➢ The anti-noise performance of the OQPSK is
a1
a3
a2
a4
a5
a7a3
a5
a7
a2
a4
a6
a8
➢ Anti-noise performance of 4 QDPSK signal is the same as that of QDPSK signal.
➢ 4 QDPSK system has already been used in the North America’s 2nd generation cellular networks (IS-136).
➢ Expression
sk
(t)
c os ( s t
ak
2T
t
k
)
(k 1)T t kT
where s 2f s ak 1
( When the input symbol is 1, ak =+1, when the input symbol is 0, ak = -1)
T － symbol duration;
k － definite initial phase of the k-th symbol.
4
sk
(t)
c os ( s t
ak
2T
t
k
)
(k 1)T t kT
➢ As can be seen from the above equation:
When ak =+1, the symbol frequency f1 = fs+1/(4T);
通信原理(英文版)3
Definition:
➢ Modulating signal m(t) －signal from the source
➢ Modulated signal s(t) － signal after being modulated
➢ Modulator － the device for modulation
Chapter 3 Analog modulation system
3.1 Introduction
Analog modulation: modulation of a carrier by a source
baseband analog signal
Carrier: a deterministic periodic waveform － cosinusoidal
ri
E
1 2
1
m'
(t
)2
A2
/ n2 (t)
∴Ratio of S/N before and after detection:
m(t)
1+m(t)
+1 = 1
0
1+m(t)
1
0
=
4
Frequency density
➢ Contain discrete carrier component ➢ When m(t) is cosinusoidal, and m＝100％,
sum of the two side band power ＝ half of carrier power
Basic principles
Let: m(t) = [1+m(t)]， |m(t)| 1， m(t)|max = m －modulation index, then we have the AM signal
通信原理(英文版)
【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(英文版)
is
S() s(t)ejtdt
The inverse Fourier transform of S() is the original signal:
s(t) S()ejtd
【Example 2.3】Find the frequency spectral density of a rectangular pulse.
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
T
jn0
2V si
n0T
nn02
3
Frequency spectrum figure
4
【Example 2.2】Find the frequency spectrum of a sinusoidal wave after full-wave rectification. Solution：Assume the expression of the signal is
➢ Signal power: Let R = 1, then P = V2/R = I2R = V2 = I2 ➢ Signal energy：Let S represent V or I，if S varies with time，then S can
be rewritten as s(t), Hence, the signal energy E = s2(t)dt
通信原理(英文版)1
大家好
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
Demodulation
Channel
Modulation
Informitter
1.3.4 Specifications of Digital
Communication Systems
Relationship between efficiency & reliability (rate ~ accuracy)
Two categories of signals
• Analog signal：Its voltage or current can be expressed by a continuous function of time. For example, speech signal.
• Digital signal： Its voltage or current can only take finite number of discrete values. For example, digital computer data signal.
(MF)
direction-finding, distress
calling, coast guard
大家好
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Division of frequency band
通信原理(英文版)
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.
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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
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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
无线通信原理与应用英lecture2(英文)
2020/7/18
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Illustration of a handoff scenario at cell boundary
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BS2 BS1
Equilateral triangle:
At 1.3r 2
Square: Hexagon:
As 2.0r 2
Ah 2.6r 2
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Cellular coverage representation
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The size of a cell
Macrocell large, covering a wide are range of several hundred kilometres (km) to ten km mostly deployed in rural and sparsely populated areas
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Tradeoff
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Propagation model
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Din
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Co-channel interference ratio
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Example 2
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S 12dB(15.9), n 4 Q (615.9)0.25 3.12 I
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Method of locating co-channel cells
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通信原理-英文版分析
Fig. 1.3.2 Distortion and restoration of digital signal waveforms
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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
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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
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1.3.2 Advantages of Digital Communication
Out put S/N increases with bandwidth according to exponential law.
无线通信原理双语讲义第一二讲
⽆线通信原理双语讲义第⼀⼆讲Course Code: B020305Course Title: Wireless Communications Principle and Practice (T. S. Rappaport 2004) Academic Year : 2015 Semester: 2Lecturer: Gao Huanqin (Room1610), College of Commu. and Inform.Engineering,NJUPT Lectures: 32 hours, lectured in English partially.E-mail Address: gaohq@/doc/e24373aa26fff705cc170ad9.html .au前⾔Preface (PP:1)本节课是本课程的第⼀堂课，介绍课程的相关信息；讲授第⼀章教学内容“⽆线通信概述”，它涉及英⽂教科书的第⼀、第⼆章内容。
Content（教学内容）s: Provide fundamental treatment about many practical and theoretical concepts that form the basis of wireless communications, especially fundamental cellular radio concepts such as frequency reuse. Propagation path loss prediction models for cellular networks, multiple access method. ⽆线通信基础相关的基本理论、概念与应⽤，突出基本概念与基础理论，例如蜂窝⽹中频率复⽤。
基础理论例如传播路径损耗预测模型，多址接⼊技术等。
Objective of the course（教学⽬标）: After the course the student has a good basic knowledge of cellular and personal communication systems and the systems evolving from it. Also, the student will get a basic knowledge of the design of cellular networks and understand the special requirements, which result from the mobile radio environment. 通过本课程的学习让同学了解⽆线蜂窝通信系统的基本概念、基础理论以及系统演进，了解移动⽆线环境下的蜂窝通信⽹络系统的设计及需求。
通信原理(英文版)课件
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.
通信原理讲义教程cthan
d0 2t1
01 A
t
23 d0
45 B
t
码距等于5的两个码组
汉明距离
9
为了能纠正t个错码，同时检测e个错码，要求最小码距 d0et1 (et)
A
t
e
B
t
1
汉明距离
码距等于(e+t+1)的两个码组
纠检结合工作方式： 当错码数量少时，系统按前向纠错方式工作，以节
省重发时间，提高传输效率； 当错码数量多时，系统按反馈重发的纠错方式工作，
10-1
n0 n0 n0(1/T) n0RB
式中，RB － 码元速率。
10-2
提高传输速率，采用编 码以保持误码率不变；付出 的代价仍是带宽增大。
10-3
Pe
10-4
10-5
• 2PSK A •E
•B 编码后 • •C
D
10-6
Eb/n0 (dB)
编码和误码率关系
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10.3.4 编码增益
定义：在保持误码率恒定条件下，采用纠错编码所节省的信
ARQ和前向纠错比较：
优点 监督码元较少，即码率较高 检错的计算复杂度较低 能适应不同特性的信道
缺点 需要双向信道。 不适用于一点到多点的通信系统或广播系统。
传输效率降低，可能因反复重发而造成事实上的通
信中断。
5
10.2 纠错编码的基本原理
➢ 分组码举例 设：有一种由3个二进制码元构成的编码，它共有23 = 8种 不同的可能码组： 000 – 晴 001 – 云 010 – 阴 011 – 雨 100 – 雪 101 – 霜 110 – 雾 111 – 雹 这时，若一个码组中发生错码，则将收到错误信息。 若在此8种码组中仅允许使用4种来传送天气，例如：令 000 – 晴 011 – 云 101 – 阴 110 – 雨 为许用码组，其他4种不允许使用，称为禁用码组。 这时，接收端有可能发现（检测到）码组中的一个错码。 这种编码只能检测错码，不能纠正错码。 若规定只许用两个码组：例如 000 – 晴 111 – 雨 就能检测两个以下错码，或纠正一个错码。
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.
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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)
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?