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第四讲 PowerPoint PPT Presentation


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第四讲. 4. 数据通信的主要技术指标. 数据通信的主要技术指标有数据传输速率、传输延迟、信道带宽、信道容量、数据传输的误码率等,这些指标是衡量数据传输的 有效性和可靠性 的参数。 有效性 主要由数据传输速率、传输延迟、信道带宽和信道容量等指标来衡量。 可靠性 一般用数据传输的误码率指标来衡量。. (1) 数据传输速率 数据传输速率是指单位时间内传输信息量的多少。它是衡量数据传输有效性的主要指标。 数据传输速率通常用 波特率 和 比特率 来表示。.

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第四讲

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4.


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(1)


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: (Baud)T()

Rs1/T (Baud)

1


B s bps r b 1 t log 2 n bps t n r b

(b/sbps)

Rb(1/T)log2N (bps)

TNRb


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N21

Rb1/T (bps)

Rb Rslog2N (bps)

log2N


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164Kbps 30048*10

t=8*10*300*4/64k


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Pe Ne/N

NeNPe


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(300,000km2/3)


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21000km3kbits20kbps60kbps? (200,000km/s300,000km/s)


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3/20=150ms

3/60=50ms

1000/(2*105)=5ms

36000*2/(3*105)=240ms

150+5=155ms

50+240=290ms


2 b s

(2)

(b/s)


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C 2 f log 2 n f n c c 2 f log 2 n bps

C2 F log2N

FNC()

C2 F log2N (bps)


C f log 2 1 s n

()

CF log2(1S/N)


3 6mh z 4 c 2 6m log 2 4 24mbps

36MHZ4

C= 2*6M*log24=24Mbps


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44KHZ830dB

C2 F log2N=2*4K*log28=24Kbps

dB10lgS/N

10lgS/N=30 S/N=103

CF log2(1S/N)= 4K*log21001=40Kbps


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5.

(1)


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(a)

(b)

(c)


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(2)


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01101001

01101001

0

1

1

0

1

0

0

1

01101001


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(3)


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  • DTE


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6.


2 2 1

2. 2 1.

1

  • ()


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(2)

  • ()


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(3)


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2.


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(1)


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  • ()


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  • 1AM(ASK)

    2FM(FSK)

    3PM(PSK)

  • f(t)Asin(t+)A


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  • ASK

  • ASK


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ASK

ASK


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  • FSK()(10)

  • FSK

  • FSK


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1

0

1 1

0 0

1

0

FSK


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  • PSK()(10)


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1

0

1 1

0 0

1

0

PSK


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(2)


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(a)

(b)


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(a)

(b)


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01


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1 0 1 0 0 1 1 0


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10


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0 1 0 1 1 0 0 1


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(3)

  • (PCM)(M)

  • PCM


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  • F f (F2f)


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  • 264,128, 256


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  • PCM


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011 000 001 010 101 111 110 100

PCM


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3.


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n

n

1

n


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(1) (FDM)


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  • FDM


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f

n fn

...

3 f3

2 f2

1 f1

t


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(2) (TDM)


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f

A

A B C D A B C D A BC D A B CD

t


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  • (STDM)(ATDM)


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(STDM)


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(ATDM)


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(3) (CDM)


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  • CDMCDMCDM


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  • CDM


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D

B1

B2

B2

B1

D


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(4) (WDM)

  • WDM


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  • ,


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4.


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0 1 0 0 0 0 0 1 0

1

2

3

4


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  • ()(SYN)SYN


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  • ()(0111110)


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S S S

Y Y Y

N N 1 2 N N

(a)

01111110 01111110

(b)


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