Introduction to Digital Communications

Francisco J. Escribano, 2014-15

DIGITAL COMMUNICATIONS

Block 1

Introduction to Digital Communications

2

Digital Communications: introduction

3

Digital Communications: introduction

COMMUNICATIONTHEORY

4

Digital Communications: introduction

COMMUNICATIONTHEORY

BASICCONCEPTS

5

Digital Communications: introduction

COMMUNICATIONTHEORY

DIGITALCOMMUNICATIONS

BASICCONCEPTS

6

Digital Communications: introduction

COMMUNICATIONTHEORY

DIGITALCOMMUNICATIONS

BASICCONCEPTS

ADVANCEDCONCEPTS

7

Digital Communications: introduction

COMMUNICATIONTHEORY

DIGITALCOMMUNICATIONS

BASICCONCEPTS

ADVANCEDCONCEPTS

8

Digital Communications: introduction

COMMUNICATIONTHEORY

DIGITALCOMMUNICATIONS

COMMUNICATIONSYSTEMS

BASICCONCEPTS

ADVANCEDCONCEPTS

9

Digital Communications: introduction

COMMUNICATIONTHEORY

DIGITALCOMMUNICATIONS

MOBILECOMMUNICATIONS

COMMUNICATIONSYSTEMS

BASICCONCEPTS

ADVANCEDCONCEPTS

10

Digital Communications: introduction

COMMUNICATIONTHEORY

DIGITALCOMMUNICATIONS

RADIATION ANDRADIOCOMMUNICATION

MOBILECOMMUNICATIONS

COMMUNICATIONSYSTEMS

BASICCONCEPTS

ADVANCEDCONCEPTS

11

Digital Communications: introduction

COMMUNICATIONTHEORY

COMMUNICATIONCIRCUITS

DIGITALCOMMUNICATIONS

RADIATION ANDRADIOCOMMUNICATION

MOBILECOMMUNICATIONS

COMMUNICATIONSYSTEMS

BASICCONCEPTS

ADVANCEDCONCEPTS

12

Digital Communications: introduction

● Basic texts:

– Bernard Sklar, Digital Communications, 2001, Prentice Hall (Chapter 1).

– Simon Haykin, Communication Systems, 2001, Wiley (Background and preview).

– John G. Proakis, Digital Communications, 2008, McGraw-Hill (Chapter 1).

13

Digital Communications: introduction● Logical/functional organization of communications ⇒ layers

14

Digital Communications: introduction● Logical/functional organization of communications ⇒ layers

15

Digital Communications: introduction● Logical/functional organization of communications ⇒ layers

16

Digital Communications: introduction● Logical/functional organization of communications ⇒ layers

DataStream

17

Digital Communications: introduction● Logical/functional organization of communications ⇒ layers

DataStream

DataStream

18

Digital Communications: introduction● Logical/functional organization of communications ⇒ layers

MEDIUM

DataStream

DataStream

19

Digital Communications: introduction● Logical/functional organization of communications ⇒ layers

MEDIUM

DataStream

DataStream

20

Digital Communications: introduction● Logical/functional organization of communications ⇒ layers

PHY (1) PHY (1)

MEDIUM

DataStream

DataStream

21

Digital Communications: introduction● Logical/functional organization of communications ⇒ layers

PHY (1)

MAC (2)(<DLL)

PHY (1)

MAC (2)(<DLL)

MEDIUM

DataStream

DataStream

22

Digital Communications: introduction● Logical/functional organization of communications ⇒ layers

PHY (1)

MAC (2)(<DLL)

PHY (1)

MAC (2)(<DLL)

MEDIUM

DataStream

ControlControl

DataStream

23

Digital Communications: introduction● Logical/functional organization of communications ⇒ layers

PHY (1)

MAC (2)(<DLL)

PHY (1)

MAC (2)(<DLL)

MEDIUM

DataStream

ControlControl

DataStream

24

Digital Communications: introduction● Logical/functional organization of communications ⇒ layers

PHY (1)

MAC (2)(<DLL)

PHY (1)

MAC (2)(<DLL)

MEDIUM

DigitalCommunications

DataStream

ControlControl

DataStream

25

Digital Communications: introduction● Logical/functional organization of communications ⇒ layers

PHY (1)

MAC (2)(<DLL)

PHY (1)

MAC (2)(<DLL)

MEDIUM

Telematics

DigitalCommunications

DataStream

ControlControl

DataStream

26

Digital Communications: introduction

● Before proceeding further...– All this is about... transferring information

● Some issues:– Can we precisely define information?

– How can it and its quality be measured?

– Are there any limitations to the amount of information we can transfer?

● And the answer is...

27

Digital Communications: introduction

● Before proceeding further...– All this is about... transferring information

● Some issues:– Can we precisely define information?

– How can it and its quality be measured?

– Are there any limitations to the amount of information we can transfer?

● And the answer is...

?

28

Digital Communications: introduction

● Before proceeding further...– All this is about... transferring information

● Some issues:– Can we precisely define information?

– How can it and its quality be measured?

– Are there any limitations to the amount of information we can transfer?

● And the answer is...

INFORMATION THEORY (Block 2)

Source: Wikipedia

!

29

Digital Communications: introduction● What are the main functions carried out at the physical layer?

30

Digital Communications: introduction● What are the main functions carried out at the physical layer?

31

Digital Communications: introduction● What are the main functions carried out at the physical layer?

WIFI CARD inADSL modem

32

Digital Communications: introduction● What are the main functions carried out at the physical layer?

WIFI CARD inADSL modem

Radio frequency -RF(analog)

33

Digital Communications: introduction● What are the main functions carried out at the physical layer?

WIFI CARD inADSL modem

Radio frequency -RF(analog)

Upperlayers (2,3...)

34

Digital Communications: introduction● What are the main functions carried out at the physical layer?

WIFI CARD inADSL modem

Radio frequency -RF(analog)

Base-band

(digital)

Upperlayers (2,3...)

35

Digital Communications: introduction● What are the main functions carried out at the physical layer?

WIFI CARD inADSL modem

Radio frequency -RF(analog)

Base-band

(digital)

Upperlayers (2,3...)

● Adaptation to the medium.● Information protection.● Sharing resources.● Signal generation.● Interface between RF and upper

layers.● Evaluation and compensation of

channel distortions.● …...........................................................

36

Digital Communications: introduction● What are the main functions carried out at the physical layer?

WIFI CARD inADSL modem

Radio frequency -RF(analog)

Base-band

(digital)

Upperlayers (2,3...)

● Adaptation to the medium.● Information protection.● Sharing resources.● Signal generation.● Interface between RF and upper

layers.● Evaluation and compensation of

channel distortions.● …...........................................................

37

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

38

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

39

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

40

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

PHY (1) TX

41

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

PHY (1) TX

42

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

PHY (1) TX

43

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

44

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

45

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

CHANNEL1

Performance (1)

46

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

CHANNEL1

Performance (1)

47

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

CHANNEL1

Performance (1)

CHANNEL2

Performance (2)

48

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

CHANNEL1

Performance (1)

CHANNEL2

Performance (2)

49

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

CHANNEL1

Performance (1)

CHANNEL2

Performance (2)

CHANNEL3

Performance (3)

50

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

CHANNEL1

Performance (1)

CHANNEL2

Performance (2)

CHANNEL3

Performance (3) Design & evaluation:Information Theory (Block 2)

51

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

52

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

53

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

54

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

PHY (1) RX

55

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

PHY (1) RX

56

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

PHY (1) RX

57

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

58

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

59

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

CHANNEL1

Performance (1)

60

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

CHANNEL1

Performance (1)

61

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

CHANNEL2

Performance (2)

CHANNEL1

Performance (1)

62

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

CHANNEL2

Performance (2)

CHANNEL1

Performance (1)

63

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

CHANNEL2

Performance (2)

CHANNEL1

Performance (1)

CHANNEL3

Performance (3)

64

Digital Communications: introduction

● NOTE: conceptually separated operations.– Implementation may be done jointly instead of sequentially.

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

CHANNEL2

Performance (2)

CHANNEL1

Performance (1)

CHANNEL3

Performance (3)Design & evaluation:Information Theory (Block 2)

65

Digital Communications: introduction● Additional operations at the PHY.

Source

Destination

66

Digital Communications: introduction● Additional operations at the PHY.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

Source

Destination

67

Digital Communications: introduction● Additional operations at the PHY.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

Encryption Source

Destination

68

Digital Communications: introduction● Additional operations at the PHY.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

EncryptionSourcecoding Source

Destination

69

Digital Communications: introduction● Additional operations at the PHY.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

DistortionNoise

LimitationsEncryption

Sourcecoding Source

Destination

70

Digital Communications: introduction● Additional operations at the PHY.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

DistortionNoise

Limitations

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

EncryptionSourcecoding Source

Destination

71

Digital Communications: introduction● Additional operations at the PHY.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

DistortionNoise

Limitations

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

EncryptionSourcecoding

Decryption

Source

Destination

72

Digital Communications: introduction● Additional operations at the PHY.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

DistortionNoise

Limitations

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

EncryptionSourcecoding

DecryptionSource

decoding

Source

Destination

73

Digital Communications: introduction● Additional operations at the PHY.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

DistortionNoise

Limitations

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

EncryptionSourcecoding

DecryptionSource

decoding

Source

Destination

74

Digital Communications: introduction● Additional operations at the PHY.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

DistortionNoise

Limitations

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

EncryptionSourcecoding

DecryptionSource

decoding

Source

Destination

Block 2

75

Digital Communications: introduction● Additional operations at the PHY.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

DistortionNoise

Limitations

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

EncryptionSourcecoding

DecryptionSource

decoding

Source

Destination

Block 2

76

Digital Communications: introduction● Additional operations at the PHY.

Medium accessMedium access(Block 4)(Block 4)

ModulationModulation(CT & Block 2)(CT & Block 2)

Channel codingChannel coding(Block 3)(Block 3)

PHY (1) TX

DistortionNoise

Limitations

Medium accessMedium access(Block 4)(Block 4)

DemodulationDemodulation(CT & Block 2)(CT & Block 2)

ChannelChanneldecodingdecoding(Block 3)(Block 3)

PHY (1) RX

EncryptionSourcecoding

DecryptionSource

decoding

Source

Destination

Block 2

Bas

ic h

ypo

thes

is:

equ

ipro

bab

le b

inar

y se

qu

ence

P(b

=0)

=P

(b=

1)=

0.5

77

Digital Communications: introduction● Design and performance criteria/parameters.

– Already known for those familiar with Comunication Theory.

– They are evaluated for each level/layer, point to point.

– Basic issue: limitations and tradeoffs → optimization.

78

Digital Communications: introduction● Design and performance criteria/parameters.

– Already known for those familiar with Comunication Theory.

– They are evaluated for each level/layer, point to point.

– Basic issue: limitations and tradeoffs → optimization.

iDude

79

Digital Communications: introduction● Design and performance criteria/parameters.

– Already known for those familiar with Comunication Theory.

– They are evaluated for each level/layer, point to point.

– Basic issue: limitations and tradeoffs → optimization.

iDude

SNR, Eb/N0

80

Digital Communications: introduction● Design and performance criteria/parameters.

– Already known for those familiar with Comunication Theory.

– They are evaluated for each level/layer, point to point.

– Basic issue: limitations and tradeoffs → optimization.

iDude

SNR, Eb/N0

Available power

81

Digital Communications: introduction● Design and performance criteria/parameters.

– Already known for those familiar with Comunication Theory.

– They are evaluated for each level/layer, point to point.

– Basic issue: limitations and tradeoffs → optimization.

iDude

SNR, Eb/N0

Available power

Transmissionrate

82

Digital Communications: introduction● Design and performance criteria/parameters.

– Already known for those familiar with Comunication Theory.

– They are evaluated for each level/layer, point to point.

– Basic issue: limitations and tradeoffs → optimization.

iDude

SNR, Eb/N0

Bandwidth

Available power

Transmissionrate

83

Digital Communications: introduction● Design and performance criteria/parameters.

– Already known for those familiar with Comunication Theory.

– They are evaluated for each level/layer, point to point.

– Basic issue: limitations and tradeoffs → optimization.

iDude

SNR, Eb/N0

Bandwidth

Available power

Transmissionrate

Errorprobability

84

Digital Communications: introduction● Design and performance criteria/parameters.

– Already known for those familiar with Comunication Theory.

– They are evaluated for each level/layer, point to point.

– Basic issue: limitations and tradeoffs → optimization.

iDude

SNR, Eb/N0

Bandwidth

Available power

Transmissionrate

Errorprobability

DistortionInterference

85

Digital Communications: introduction

86

MEDIUM

Digital Communications: introduction

Medium accessMedium access(TX)(TX)

Medium accessMedium access(RX)(RX)

87

MEDIUM

Digital Communications: introduction

Medium accessMedium access(TX)(TX)

Medium accessMedium access(RX)(RX)

Rmax

________

SNR____

Allowedinterference

____

Reliability____

BWmax

____

Pmax

88

MEDIUM

Digital Communications: introduction

Medium accessMedium access(TX)(TX)

Medium accessMedium access(RX)(RX)

Rmax

________

SNR____

Allowedinterference

____

Reliability____

BWmax

____

Pmax

R1 SNR

1 BW

1...

89

MEDIUM

Digital Communications: introduction

Medium accessMedium access(TX)(TX)

Medium accessMedium access(RX)(RX)

Rmax

________

SNR____

Allowedinterference

____

Reliability____

BWmax

____

Pmax

R2 SNR

2 BW

2...

R1 SNR

1 BW

1...

90

MEDIUM

Digital Communications: introduction

Medium accessMedium access(TX)(TX)

Medium accessMedium access(RX)(RX)

Rmax

________

SNR____

Allowedinterference

____

Reliability____

BWmax

____

Pmax

…...

...

R2 SNR

2 BW

2...

R1 SNR

1 BW

1...

Rn SNR

n BW

n...

91

MEDIUM

Digital Communications: introduction

Medium accessMedium access(TX)(TX)

Medium accessMedium access(RX)(RX)

Rmax

________

SNR____

Allowedinterference

____

Reliability____

BWmax

____

Pmax

…...

...

R2 SNR

2 BW

2...

R1 SNR

1 BW

1...

Rn SNR

n BW

n...

…......

R'2 SNR'

2 BW'

2...

R'1 SNR'

1 BW'

1...

R'n SNR'

n BW'

n...

92

MEDIUM

Digital Communications: introduction

Medium accessMedium access(TX)(TX)

Medium accessMedium access(RX)(RX)

Rmax

________

SNR____

Allowedinterference

____

Reliability____

BWmax

____

Pmax

…...

...

R2 SNR

2 BW

2...

R1 SNR

1 BW

1...

Rn SNR

n BW

n...

…......

R'2 SNR'

2 BW'

2...

R'1 SNR'

1 BW'

1...

R'n SNR'

n BW'

n...

SHARE ANDMANAGELIMITED

RESOURCES

93

MEDIUM

Digital Communications: introduction

Medium accessMedium access(TX)(TX)

Medium accessMedium access(RX)(RX)

Rmax

________

SNR____

Allowedinterference

____

Reliability____

BWmax

____

Pmax

…...

...

R2 SNR

2 BW

2...

R1 SNR

1 BW

1...

Rn SNR

n BW

n...

…......

R'2 SNR'

2 BW'

2...

R'1 SNR'

1 BW'

1...

R'n SNR'

n BW'

n...

SHARE ANDMANAGELIMITED

RESOURCES

InformationTheory

94

Digital Communications: introduction

95

Digital Communications: introduction

ModulationModulation(TX)(TX)

DemodulationDemodulation(RX)(RX)

96

CH

AN

NE

L

Digital Communications: introduction

ModulationModulation(TX)(TX)

DemodulationDemodulation(RX)(RX)

97

CH

AN

NE

L

Digital Communications: introduction

ModulationModulation(TX)(TX)

DemodulationDemodulation(RX)(RX) R

mod

________

SNR____

Ps(e)

____

BWmod

____

Pmod

98

CH

AN

NE

L

Digital Communications: introduction

ModulationModulation(TX)(TX)

DemodulationDemodulation(RX)(RX) R

mod

________

SNR____

Ps(e)

____

BWmod

____

Pmod

99

CH

AN

NE

L

Digital Communications: introduction

ModulationModulation(TX)(TX)

DemodulationDemodulation(RX)(RX) R

mod

________

SNR____

Ps(e)

____

BWmod

____

Pmod

100

CH

AN

NE

L

Digital Communications: introduction

ModulationModulation(TX)(TX)

DemodulationDemodulation(RX)(RX) R

mod

________

SNR____

Ps(e)

____

BWmod

____

Pmod

Pb(e)

_____

Eb/N0_____

Rb

101

CH

AN

NE

L

Digital Communications: introduction

ModulationModulation(TX)(TX)

DemodulationDemodulation(RX)(RX) R

mod

________

SNR____

Ps(e)

____

BWmod

____

Pmod

Pb(e)

_____

Eb/N0_____

Rb

ADAPT SIGNALSTO THE CHANNEL

AND IMPROVEPERFORMANCE

102

CH

AN

NE

L

Digital Communications: introduction

ModulationModulation(TX)(TX)

DemodulationDemodulation(RX)(RX) R

mod

________

SNR____

Ps(e)

____

BWmod

____

Pmod

Pb(e)

_____

Eb/N0_____

Rb

ADAPT SIGNALSTO THE CHANNEL

AND IMPROVEPERFORMANCE

InformationTheory

103

Digital Communications: introduction

104

Digital Communications: introduction

Channel codingChannel coding(TX)(TX)

ChannelChanneldecodingdecoding

(RX)(RX)

105

CH

AN

NE

L

Digital Communications: introduction

Channel codingChannel coding(TX)(TX)

ChannelChanneldecodingdecoding

(RX)(RX)

106

CH

AN

NE

L

Digital Communications: introduction

Channel codingChannel coding(TX)(TX)

ChannelChanneldecodingdecoding

(RX)(RX)

Pb(e)

________

Eb/N0(out)____

Rb

107

CH

AN

NE

L

Digital Communications: introduction

Channel codingChannel coding(TX)(TX)

ChannelChanneldecodingdecoding

(RX)(RX)

Pb(e)

________

Eb/N0(out)____

Rb

108

CH

AN

NE

L

Digital Communications: introduction

Channel codingChannel coding(TX)(TX)

ChannelChanneldecodingdecoding

(RX)(RX)

Pb(e)

________

Eb/N0(out)____

Rb

109

CH

AN

NE

L

Digital Communications: introduction

Channel codingChannel coding(TX)(TX)

ChannelChanneldecodingdecoding

(RX)(RX)

Pb(e)

________

Eb/N0(out)____

Rb

P'b(e)<P

b(e)

_____

Eb/N0(in)_____

R'b<R

b

110

CH

AN

NE

L

Digital Communications: introduction

Channel codingChannel coding(TX)(TX)

ChannelChanneldecodingdecoding

(RX)(RX)

Pb(e)

________

Eb/N0(out)____

Rb

P'b(e)<P

b(e)

_____

Eb/N0(in)_____

R'b<R

b

PROTECTINFORMATION

INTEGRITYAT THE COST

OF DATA RATE

111

CH

AN

NE

L

Digital Communications: introduction

Channel codingChannel coding(TX)(TX)

ChannelChanneldecodingdecoding

(RX)(RX)

Pb(e)

________

Eb/N0(out)____

Rb

P'b(e)<P

b(e)

_____

Eb/N0(in)_____

R'b<R

b

PROTECTINFORMATION

INTEGRITYAT THE COST

OF DATA RATEInformation

Theory

112

Digital Communications: introduction

● Example: WiFi standard(public access: http://standards.ieee.org/getieee802/download/802.11-2007.pdf )

113

Digital Communications: introduction

● Example: WiFi standard(public access: http://standards.ieee.org/getieee802/download/802.11-2007.pdf )

114

Digital Communications: introduction

● Example: WiFi standard(public access: http://standards.ieee.org/getieee802/download/802.11-2007.pdf )

115

Digital Communications: introduction

● Example: WiFi standard(public access: http://standards.ieee.org/getieee802/download/802.11-2007.pdf )

116

Digital Communications: introduction

● Medium access (channel identification).

117

Digital Communications: introduction

● Medium access (channel identification).

118

Digital Communications: introduction

● Medium access (channel identification).

119

Digital Communications: introduction

● Medium access (channel identification).

Signalgeneration

120

Digital Communications: introduction

● Medium access + modulation.

121

Digital Communications: introduction

● Medium access + modulation.

122

Digital Communications: introduction

● Medium access + modulation.

123

Digital Communications: introduction

● Medium access + modulation.

124

Digital Communications: introduction

● Medium access + modulation.

125

Digital Communications: introduction

● Medium access + modulation.Different modes

for resourcesharing

126

Digital Communications: introduction

● Medium access + modulation.Different modes

for resourcesharing

127

Digital Communications: introduction

● Modulation and channel coding.

128

Digital Communications: introduction

● Modulation and channel coding.

129

Digital Communications: introduction

● Modulation and channel coding.

130

Digital Communications: introduction

● Modulation and channel coding.

Modulator

131

Digital Communications: introduction

● Modulation and channel coding.

Modulator

132

Digital Communications: introduction

● Modulation and channel coding.

ModulatorChannelencoder

133

Digital Communications: introduction

● Modulation and channel coding.

ModulatorChannelencoder

134

Digital Communications: introduction

● Channel encoder.

135

Digital Communications: introduction

● Channel encoder.

136

Digital Communications: introduction

● Channel encoder.

137

Digital Communications: introduction

● Channel encoder.

138

Digital Communications: introduction

● Channel encoder.

Algebraicstructure

139

Digital Communications: introduction

● Channel encoder.

Algebraicstructure

140

Digital Communications: introduction

● Channel encoder.

Algebraicstructure

Implementation:finite-statemachine

141

Digital Communications: introduction● It is important to discern

– Abstract operations / layers (“divide and conquer”).

– HW implementation.

● Recall always

– Basic scheme of Digital Communications.

– Design and evaluation parameters.

– Concepts from Communication Theory and Signals and Systems.

● Main purpose:

– Given some resources, and some target conditions and target performance, manage to evaluate and/or design the appropriate subsystems.