通信原理(英文版)1ppt课件
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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)
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)
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演示文稿通信原理英文版
• Digital communication system Requirement － correct decision Criterion － Error probability Basic issur － statistical decision theory
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
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)
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
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)11[63页]
![通信原理(英文版)11[63页]](https://img.taocdn.com/s3/m/e0c876856f1aff00bfd51e3d.png)
➢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)
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
【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
无线通信原理双语lecture.ppt
Wireless LAN Standards:Wi-Fi 802.11b, 802.11a, 802.11g
2019/12/18
16
WLAN Infrastructure
•Network between devices in home and office environment; •Typically gives access to a fixed infrastructure
• Cognitive and Software Defined Radio,
IEEE 802.22(proposed), et al
Area, …
The output of Wireless System Modeling and Design: International standard (IP): 802.11,802.16,GSM…
2019/12/18
17
1.5 WPANs and WMANs
WPANs: Wireless Personal Area Networks
3G Offers enhancements to current applications including greater data speeds, increased capacity for voice and data and a broader range of services.
In 2000, ITU approved the following three standards:
• Wireless Sensor Networks • 3G and beyond • 3.9G (LTE), 4G,et al
Coverage (range)
Wireless Key techniques
2019/12/18
16
WLAN Infrastructure
•Network between devices in home and office environment; •Typically gives access to a fixed infrastructure
• Cognitive and Software Defined Radio,
IEEE 802.22(proposed), et al
Area, …
The output of Wireless System Modeling and Design: International standard (IP): 802.11,802.16,GSM…
2019/12/18
17
1.5 WPANs and WMANs
WPANs: Wireless Personal Area Networks
3G Offers enhancements to current applications including greater data speeds, increased capacity for voice and data and a broader range of services.
In 2000, ITU approved the following three standards:
• Wireless Sensor Networks • 3G and beyond • 3.9G (LTE), 4G,et al
Coverage (range)
Wireless Key techniques
《通信英语教程》课件
PPT courseware for Communication English
Course
目录
• Overview of the Communication Industry • Basic knowledge of communication English • Communication English Application Practice • Common Terminology in the
It involves effective speaking and listening skills to communicate technical information in meetings, seminars, or workshops.
Communication English in Contract Agreements
The Current Situation and Future Trends of the Communication Industry
Current situation
The communication industry is currently experiencing a digital transformation, with traditional media being eclipsed by new digital platforms.
The main business areas of the communication
industry
Broadcasting
This includes television and radio stations, which produce and transmit content to观众.
Course
目录
• Overview of the Communication Industry • Basic knowledge of communication English • Communication English Application Practice • Common Terminology in the
It involves effective speaking and listening skills to communicate technical information in meetings, seminars, or workshops.
Communication English in Contract Agreements
The Current Situation and Future Trends of the Communication Industry
Current situation
The communication industry is currently experiencing a digital transformation, with traditional media being eclipsed by new digital platforms.
The main business areas of the communication
industry
Broadcasting
This includes television and radio stations, which produce and transmit content to观众.
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t
t
Analog signals
s(t) s(t)
Symbol
t
t
Digital signals
.
7
Two kinds of communication systems
• Analog communication system Requirement － High fidelity Criterion － Signal to noise ratio Basic issue － parameter estimation
• Digital communication system Requirement － correct decision Criterion － Error probability Basic issur － statistical decision theory
.
8
1.3.2 Advantages of Digital Communication
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 message can be integrated to transmit
# 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
# 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.
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
Signal：the carrier of message
What transmitted in a communication system is signal.
.
3
Measurement of information：
# “quantity of message” information content
• Digital signal： Its voltage or current can only take finite number of discrete values. For example, digital computer data signal.
.
6
Analog Signal & Digital Signal
.
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
Out put S/N increases with bandwidth according to exponential law.
.
10
11
Digital communication system model
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
Digital communication equipment:
➢Design and manufacture are easier ➢Weight & volume are smaller
Digital signal can be compressed by source coding to reduce redundency.
t
Analog signals
s(t) s(t)
Symbol
t
t
Digital signals
.
7
Two kinds of communication systems
• Analog communication system Requirement － High fidelity Criterion － Signal to noise ratio Basic issue － parameter estimation
• Digital communication system Requirement － correct decision Criterion － Error probability Basic issur － statistical decision theory
.
8
1.3.2 Advantages of Digital Communication
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 message can be integrated to transmit
# 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
# 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.
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
Signal：the carrier of message
What transmitted in a communication system is signal.
.
3
Measurement of information：
# “quantity of message” information content
• Digital signal： Its voltage or current can only take finite number of discrete values. For example, digital computer data signal.
.
6
Analog Signal & Digital Signal
.
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
Out put S/N increases with bandwidth according to exponential law.
.
10
11
Digital communication system model
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
Digital communication equipment:
➢Design and manufacture are easier ➢Weight & volume are smaller
Digital signal can be compressed by source coding to reduce redundency.