elen602 lecture 3 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
ELEN602 Lecture 3 PowerPoint Presentation
Download Presentation
ELEN602 Lecture 3

Loading in 2 Seconds...

play fullscreen
1 / 42

ELEN602 Lecture 3 - PowerPoint PPT Presentation


  • 161 Views
  • Uploaded on

Review of last lecture layering, IP architecture Data Transmission. ELEN602 Lecture 3. Abstract View of Data Transmission. Transmitter. Receiver. Communication channel. Communication Channel Properties: -- Bandwidth -- Transmission and Propagation Delay -- Jitter -- Loss/Error rates

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'ELEN602 Lecture 3' - hamish


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
elen602 lecture 3
Review of last lecture

layering, IP architecture

Data Transmission

ELEN602 Lecture 3
slide2

Abstract View of Data Transmission

Transmitter

Receiver

Communication channel

Communication Channel Properties:

-- Bandwidth

-- Transmission and Propagation Delay

-- Jitter

-- Loss/Error rates

-- Buffering

slide3
(a) Analog transmission: all details must be reproduced accurately

Analog vs. Digital Transmission

Received

Sent

  • e.g. AM, FM, TV transmission

(b) Digital transmission: only discrete levels need to be reproduced

Received

Sent

  • e.g digital telephone, CD Audio
slide4

A Typical Communication Channel

Transmission segment

Destination

Source

Repeater

Repeater

slide5

An Analog Repeater

Recovered signal

+

residual noise

Attenuated & distorted signal

+

noise

Amp.

Equalizer

Repeater

slide6

A Digital Repeater

Decision Circuit.

& Signal

Regenerator

Amplifier

Equalizer

Timing

Recovery

slide7

d meters

0110101...

communication channel

0110101...

slide8

Characteristics of an Idealized Channel

(a) Lowpass and idealized lowpass channel

A(f)

A(f)

1

f

f

0

W

0

W

(b) Maximum pulse transmission rate is 2W pulses/second (Nyquist rate)

Channel

t

t

slide9

Impact of Noise on Communication

signal + noise

signal

noise

High

SNR

t

t

t

noise

signal + noise

signal

Low

SNR

t

t

t

Average Signal Power

SNR =

Average Noise Power

SNR (dB) = 10 log10 SNR

slide10

Channel Characterization -Frequency Domain

Aincos 2ft

Aoutcos (2ft + (f))

Channel

t

t

Aout

Ain

A(f) =

slide11

A(f)=1

1+42f2

Signal Amplitude Attentuation

1

f

slide12

Signal Phase Modulation

(f)=tan-1 2f

1/2

0

f

-45o

-90o

slide13

1 0 0 0 0 0 0 1

. . .

. . .

t

A Pulse

1 ms

slide16

Signaling a Pulse with Zero Inter-symbol Interference

s(t) = sin(2Wt)/ 2Wt

t

T T T T TT T T T TT T TT

slide17

Digital Baseband Signal and Baseband Tx. System

1

0

1

1

0

1

+A

2T

4T

5T

T

3T

0

t

-A

r(t)

Receiver

Transmitter Filter

Comm. Channel

Receiver Filter

Received signal

slide18

(a) 3 separate pulses for sequence 110

t

T

T

T

T

T

T

(b) Combined signal for sequence 110

t

T

T

T

T

T

T

slide19

typical noise

4 signal levels

8 signal levels

slide20

Signal levels -- Error Probability

0 2 4 6 8

/2

/2 = A/(M-1) 

Channel Capacity = W log (1 +SNR)

slide21

0

1

0

1

1

1

1

0

0

Unipolar

NRZ

Polar NRZ

NRZ-Inverted

(Differential

Encoding)

Bipolar

Encoding

Manchester

Encoding

Differential

Manchester

Encoding

coding methods properties
Unipolar NRZ - power = A^2/2

Polar NRZ - power = A^2/4

Bipolar encoding reduces the low-frequency spectrum

Timing Recovery is also easier, used in telephones

NRZ Inverted -- A transition means 1, no transition is 0

Errors occur in pairs

Ethernet uses Manchester encoding

A transition from + to - is 1, - to + is 0 (in the middle)

Twice the pulse rate of binary coding

Differential Manchester encoding -used in Token rings

Every pulse has a transition in the middle

A transition at the beginning is 0, no transition is 1

Coding Methods -Properties
slide24

f

f2

f1

0

fc

Figure 3.27

slide25

1

0

1

1

0

1

6T

6T

6T

2T

2T

2T

4T

4T

4T

5T

5T

5T

3T

3T

3T

T

T

T

0

0

0

Amplitude, Frequency and Phase Modulation

Information

+1

(a)

Amplitude

Shift

Keying

t

-1

+1

(b)

Frequency

Shift

Keying

t

-1

+1

(c)

Phase

Shift

Keying

t

-1

slide26

1

0

1

1

0

1

+A

(c) Modulated

Signal Yi(t)

6T

2T

4T

5T

3T

T

0

-A

6T

2T

4T

5T

3T

T

0

(a) Information

+A

(b) Baseband

Signal Xi(t)

t

6T

2T

4T

5T

T

3T

0

-A

t

+2A

(d) 2Yi(t) cos(2fct)

t

-2A

slide27

Modulator and Demodulator

(a) Modulate cos(2fct) by multiplying it by Akfor (k-1)T < t <kT:

x

Ak

Yi(t) = Akcos(2fct)

cos(2fct)

(b) Demodulate (recover) Akby multiplying by 2cos(2fct) and lowpass filtering:

Lowpass

Filter with

cutoff W Hz

x

Yi(t) = Akcos(2fct)

Xi(t)

2cos(2fct)

2Akcos2(2fct) = Ak {1 + cos(2fct)}

slide28

x

Ak

Yi(t) = Akcos(2fc t)

cos(2fc t)

+

Y(t)

x

Bk

Yq(t) = Bksin(2fc t)

sin(2fc t)

QAM Modulator

Modulatecos(2fct)and sin (2fct)bymultiplying them by Akand Bk respectively for (k-1)T < t <kT:

slide29

QAM Demodulator

Lowpass

Filter with

cutoff W/2 Hz

x

Y(t)

Ak

2cos(2fc t)

2cos2(2fct)+2Bkcos(2fct)sin(2fct)

= Ak {1 + cos(4fct)}+Bk{0 + sin(4fct)}

Lowpass

Filter with

cutoff W/2 Hz

x

Bk

2sin(2fc t)

2Bk sin2(2fct)+2Akcos(2fct)sin(2fct)

= Bk{1 - cos(4fct)}+Ak {0 + sin(4fct)}

slide30

2-D signal

Bk

Ak

4 “levels”/ pulse

2 bits / pulse

2W bits per second

Signal Constellations

Bk

2-D signal

Ak

16 “levels”/ pulse

4 bits / pulse

4W bits per second

slide31

Bk

Bk

Ak

Ak

16 “levels”/ pulse

4 bits / pulse

4W bits per second

Other Signal Constellations

4 “levels”/ pulse

2 bits / pulse

2W bits per second

slide32

Electromagnetic Spectrum

Frequency (Hz)

106

108

1010

1012

1014

1016

1018

1020

1022

1024

102

104

power &

telephone

broadcast

radio

microwave

radio

gamma rays

infrared light

visible light

ultraviolet light

x rays

106

104

102

10

10-2

10-4

10-6

10-8

10-10

10-12

10-14

Wavelength (meters)

slide33

Twisted Pair - Attentuation vs. Frequency

26 gauge

30

24 gauge

27

24

22 gauge

21

18

Attenuation (dB/mi)

19 gauge

15

12

9

6

3

f (kHz)

100

1000

1

10

Figure 3.37

slide34

Center

conductor

Dielectric

material

Braided

outer

conductor

Outer

cover

Coaxial Cable

slide35

Coaxial Cable Attentuation vs. Frequency

35

0.7/2.9 mm

30

25

1.2/4.4 mm

Attenuation (dB/km)

20

15

2.6/9.5 mm

10

5

0.01

0.1

10

100

f (MHz)

1.0

slide36

Head

end

Cable TV Distribution Tree

Unidirectional

amplifier

slide37

Upstream fiber

Fiber

Fiber

Head

end

Fiber

node

Fiber

node

Downstream fiber

Coaxial

distribution

plant

Bidirectional

Split-Band

Amplifier

Hybrid Fiber-Coaxial System

slide38

Downstream

54 MHz

500 MHz

Downstream

Upstream

42 MHz

5 MHz

54 MHz

500 MHz

(a)

Current

allocation

Proposed downstream

(b)

Proposed

hybrid

fiber-coaxial

allocation

750 MHz

550 MHz

slide39

light

cladding

jacket

core

c

(a) Geometry of optical fiber

(b) Reflection in optical fiber

slide40

(a) Multimode fiber: multiple rays follow different paths

reflected path

direct path

(b) Single mode: only direct path propagates in fiber

slide41

Electrical

signal

Electrical

signal

Optical fiber

Modulator

Receiver

Optical

source

slide42

Frequency (Hz)

106

1012

105

108

107

104

1011

109

1010

FM radio & TV

Wireless cable

AM radio

Cellular

& PCS

satellite & terrestrial

microwave

LF

MF

HF

VHF

UHF

SHF

EHF

10-1

1

102

10-3

10-2

101

104

103

Wavelength (meters)

Figure 3.48