The Theoretical Basis for Data Communication Chapter 2
17
Chapter 2 Th Ph i lL The Physical Layer The Theoretical Basis for Data Communication • Fourier Analysis • Bandwidth-Limited Signals M i Dt Rt f Ch l • Maximum Data Rate of a Channel Bandwidth-Limited Signals A binary signal and its root-mean-square Fourier amplitudes A binary signal and its root mean square Fourier amplitudes. (b) – (c) Successive approximations to the original signal. Bandwidth-Limited Signals (2) (d) – (e) Successive approximations to the original signal (d) (e) Successive approximations to the original signal.
Transcript of The Theoretical Basis for Data Communication Chapter 2
Microsoft PowerPoint - chapter2.ppt []The Theoretical Basis for
Data Communication
• Fourier Analysis • Bandwidth-Limited Signals
M i D t R t f Ch l• Maximum Data Rate of a Channel
Bandwidth-Limited Signalsg
A binary signal and its root-mean-square Fourier amplitudesA binary signal and its root mean square Fourier amplitudes. (b) – (c) Successive approximations to the original signal.
Bandwidth-Limited Signals (2)g ( )
(d) – (e) Successive approximations to the original signal(d) (e) Successive approximations to the original signal.
*Bandwidth-Limited Signals (3)g ( )
Relation between data rate and harmonicsRelation between data rate and harmonics.
a) For a telephone wire may have 1 MHz but telephone companies add a filter restricting each customer to about 3100 Hz.
b) No hope at all for binary signals to send at data rates much higher than 38.4kbps even if the transmission facility is completely
i l ( H i t)noiseless. (no Harmonics sent) c) Nyquist’s theorem: max. data rate = 2Hlog2 V bits/sec (H: LPF BW,
V: discrete levels)V: discrete levels) d) Shannon Limit: max. data rate = H log2(1+S/N)
Guided Transmission Data
• Magnetic Media • Twisted Pair • Coaxial Cable • Fiber Optics• Fiber Optics
*Twisted Pair
Twisted Pair
a) Twisting is done because two parallel wires constitute a fine antenna.
b) Can run several kms without amplification. For longer distance, TP needs repeaters.
) C5 t i t l t lk d b tt lit i lc) C5: more twists per cm, less crosstalk and a better-quality signal over longer distances.
d) C3 (16MHz) C5(100MHz) C6(250MHz) C7(600MHz)d) C3 (16MHz), C5(100MHz), C6(250MHz), C7(600MHz) e) UTP (unshielded TP)
Coaxial Cable
*Fiber Opticsp
(a) Three examples of a light ray from inside a silica fiber impinging on the air/silica boundary at different angles.
(b) Light trapped by total internal reflection.
Fiber Opticsp
a) In the race betw. Computing and communication, the latter won. b) PCs run at 2 GHz (1981 4.77MHz): a gain of a factor of 20 per ) ( ) g p
decade. c) 56kbps to 1 Gbps: a gain of a factor of 125 per decade; available
BW in a fiber: 50000 Gbps (50 Tbps);the current practical signaling limit of about 10 Gbps is due to our inability to convert betw. electrical and optical signals any faster In lab 100 Gbps has beenelectrical and optical signals any faster. In lab, 100 Gbps has been achieved on a single fiber.
d) Single mode ( diameter is reduced to a few wavelengths of lightd) Single mode ( diameter is reduced to a few wavelengths of light, like a wave guide; the light can propagate only in a straight line)-> 50Gbps 100km without amplification.p p
e) Multi-mode fiber
Transmission of Light through Fiberg g
Attenuation of light through fiber in the infrared region. note: Optical trans. System: light source, transmission medium, detectornote: Optical trans. System: light source, transmission medium, detector
A pulse of light “1”; absence of light “0”
Fiber Cables
(a) Side view of a single fiber.(a) Side view of a single fiber. (b) End view of a sheath with three fibers.
Fiber Cables (2)( )
A comparison of semiconductor diodes and LEDs as light sourcesA comparison of semiconductor diodes and LEDs as light sources.
Fiber Optic Networksp
A fiber optic ring with active repeatersA fiber optic ring with active repeaters.
Fiber Optic Networks (2)p ( )
A passive star connection in a fiber optics networkA passive star connection in a fiber optics network.
Wireless Transmission
Li ht T i i• Lightwave Transmission
The Electromagnetic Spectrumg p
Radio Transmission
(a) In the VLF, LF, and MF bands, radio waves follow the curvature of the earth.
(b) In the HF band, they bounce off the ionosphere.
Politics of the Electromagnetic Spectrumg p
The ISM (Industrial Scientific Medical unlicensed) bands in the UnitedThe ISM (Industrial, Scientific, Medical, unlicensed) bands in the United States.
Lightwave Transmissiong
Communication Satellites
*Communication Satellites
Communication satellites and some of their properties, including altitude above the earth, round-trip delay time and number of satellites needed for global coverage
Note: (magnetosphere)(Van Allen Belt)
Communication Satellites (2)( )
Communication Satellites (3)( )
VSATs (Very Small Aperture() Terminal) using a hubVSATs (Very Small Aperture() Terminal) using a hub.
Low-Earth Orbit Satellites IridiumIridium
(a) (b)
(a) The Iridium satellites from six necklaces around the earth.( ) (b) 1628 moving cells cover the earth.
Globalstar
(a) Relaying in space.(a) Relaying in space. (b) Relaying on the ground.
Public Switched Telephone Systemp y
• Structure of the Telephone Systemp y • The Politics of Telephones • The Local Loop: Modems, ADSL and Wireless • Trunks and MultiplexingTrunks and Multiplexing • Switching
Structure of the Telephone Systemp y
(a) Fully-interconnected network. (b) Centralized switch. (c) Two-level hierarchy.
Structure of the Telephone System (2)p y ( )
A typical circuit route for a medium-distance callA typical circuit route for a medium distance call.
Major Components of the Telephone System
L l l• Local loops Analog twisted pairs going to houses and businesses
• TrunksTrunks Digital fiber optics connecting the switching officesoffices
• Switching offices Where calls are moved from one trunk to another
The Politics of Telephonesp
The relationship of LATAs(Local Access and Transport Areas), LECs(Local Exchange Carrier), and IXCs(IntereXchange Carrier). All the circles are LEC switching offices. Each
hexagon belongs to the IXC whose number is on it.
The Local Loop: Modems, ADSL, and Wireless
The use of both analog and digital transmissions for a computer toThe use of both analog and digital transmissions for a computer to computer call. Conversion is done by the modems and codecs.
Modems
(a) A binary signal (c) Frequency modulation(a) A binary signal (b) Amplitude modulation
(c) Frequency modulation (d) Phase modulation
Modems (2)( )
Modems (3)( )
(a) (b)
( ) ( )
Digital Subscriber Linesg
Bandwidth versus distanced over category 3 UTP for DSLBandwidth versus distanced over category 3 UTP for DSL.
Digital Subscriber Lines (2)g ( )
Operation of ADSL using discrete multitone modulationOperation of ADSL using discrete multitone modulation.
Digital Subscriber Lines (3)g ( )
Wireless Local Loops (802.16)p ( )
Frequency Division Multiplexingq y p g
(a) The original bandwidths. (b) The bandwidths raised in frequency(b) The bandwidths raised in frequency. (b) The multiplexed channel.
Wavelength Division Multiplexingg p g
Wavelength division multiplexingWavelength division multiplexing.
Time Division Multiplexingp g
Delta modulationDelta modulation.
Multiplexing T1 streams into higher carriersMultiplexing T1 streams into higher carriers.
Time Division Multiplexing (4)p g ( )
Two back-to-back SONET framesTwo back to back SONET frames.
Time Division Multiplexing (5)p g ( )
SONET and SDH multiplex ratesSONET and SDH multiplex rates.
Circuit Switchingg
Message Switchingg g
Packet Switchingg
The Mobile Telephone Systemp y
Fi t G ti M bil Ph• First-Generation Mobile Phones: Analog Voice
• Second Generation Mobile Phones:• Second-Generation Mobile Phones: Digital Voice
• Third-Generation Mobile Phones:• Third-Generation Mobile Phones: Digital Voice and Data
Advanced Mobile Phone Systemy
(a) Frequencies are not reused in adjacent cells. (b) To add more users, smaller cells can be used.
Channel Categories (AMPS)g ( ) The 832 channels are divided into four categories:g
• Control (base to mobile) to manage the systemControl (base to mobile) to manage the system
• Paging (base to mobile) to alert users to calls• Paging (base to mobile) to alert users to calls for them
• Access (bidirectional) for call setup and h l i tchannel assignment
• Data (bidirectional) for voice, fax, or data
D-AMPS Di it l Ad d M bil Ph S tDigital Advanced Mobile Phone System
( ) A D AMPS h l ith th(a) A D-AMPS channel with three users. (b) A D-AMPS channel with six users.
GSM Global System for Mobile CommunicationsGlobal System for Mobile Communications
GSM uses 124 frequency channels each of whichGSM uses 124 frequency channels, each of which uses an eight-slot TDM system
GSM (2)( )
A portion of the GSM framing structure.A portion of the GSM framing structure. Slot 12 CTL: control channel: paging, random access and access grant
CDMA – Code Division Multiple Accessp
a) Each station is assigned a unique m-bit chip sequence.(00011011) b) To transmit a 1 bit, sends its chip seq; to transmit a 0 bit, sends
one’s complement of its chip seq. c) B bits/s m B bits/s ( spread spectrum) d) Walsh codes: all chip seq’s are pairwise orthogonal. Two chip seq’s
ST=0 (two different stations). SS (the same station)=1 and S[S(bar)} 1S[S(bar)}=-1
*CDMA – Code Division Multiple Accessp
(a) Binary chip sequences for four stations (b) Bipolar chip sequences ( ) p p q (c) Six examples of transmissions (d) Recovery of station C’s signal
Third-Generation Mobile Phones: Digital Voice and DataDigital Voice and Data
Basic services an IMT-2000 network should provide
• High-quality voice transmission • Messaging (replace e-mail, fax, SMS, chat, etc.) • Multimedia (music videos films TV etc )• Multimedia (music, videos, films, TV, etc.) • Internet access (web surfing, w/multimedia.)
Cable Television
• Community Antenna Television I t t C bl• Internet over Cable
• Spectrum Allocationp • Cable Modems
Community Antenna Televisiony
Internet over Cable
Cable televisionCable television
Spectrum Allocationp
Frequency allocation in a typical cable TV systemFrequency allocation in a typical cable TV system used for Internet access
Cable Modems
Typical details of the upstream and downstreamTypical details of the upstream and downstream channels in North America.
Chap.2 Homeworkp
• Fourier Analysis • Bandwidth-Limited Signals
M i D t R t f Ch l• Maximum Data Rate of a Channel
Bandwidth-Limited Signalsg
A binary signal and its root-mean-square Fourier amplitudesA binary signal and its root mean square Fourier amplitudes. (b) – (c) Successive approximations to the original signal.
Bandwidth-Limited Signals (2)g ( )
(d) – (e) Successive approximations to the original signal(d) (e) Successive approximations to the original signal.
*Bandwidth-Limited Signals (3)g ( )
Relation between data rate and harmonicsRelation between data rate and harmonics.
a) For a telephone wire may have 1 MHz but telephone companies add a filter restricting each customer to about 3100 Hz.
b) No hope at all for binary signals to send at data rates much higher than 38.4kbps even if the transmission facility is completely
i l ( H i t)noiseless. (no Harmonics sent) c) Nyquist’s theorem: max. data rate = 2Hlog2 V bits/sec (H: LPF BW,
V: discrete levels)V: discrete levels) d) Shannon Limit: max. data rate = H log2(1+S/N)
Guided Transmission Data
• Magnetic Media • Twisted Pair • Coaxial Cable • Fiber Optics• Fiber Optics
*Twisted Pair
Twisted Pair
a) Twisting is done because two parallel wires constitute a fine antenna.
b) Can run several kms without amplification. For longer distance, TP needs repeaters.
) C5 t i t l t lk d b tt lit i lc) C5: more twists per cm, less crosstalk and a better-quality signal over longer distances.
d) C3 (16MHz) C5(100MHz) C6(250MHz) C7(600MHz)d) C3 (16MHz), C5(100MHz), C6(250MHz), C7(600MHz) e) UTP (unshielded TP)
Coaxial Cable
*Fiber Opticsp
(a) Three examples of a light ray from inside a silica fiber impinging on the air/silica boundary at different angles.
(b) Light trapped by total internal reflection.
Fiber Opticsp
a) In the race betw. Computing and communication, the latter won. b) PCs run at 2 GHz (1981 4.77MHz): a gain of a factor of 20 per ) ( ) g p
decade. c) 56kbps to 1 Gbps: a gain of a factor of 125 per decade; available
BW in a fiber: 50000 Gbps (50 Tbps);the current practical signaling limit of about 10 Gbps is due to our inability to convert betw. electrical and optical signals any faster In lab 100 Gbps has beenelectrical and optical signals any faster. In lab, 100 Gbps has been achieved on a single fiber.
d) Single mode ( diameter is reduced to a few wavelengths of lightd) Single mode ( diameter is reduced to a few wavelengths of light, like a wave guide; the light can propagate only in a straight line)-> 50Gbps 100km without amplification.p p
e) Multi-mode fiber
Transmission of Light through Fiberg g
Attenuation of light through fiber in the infrared region. note: Optical trans. System: light source, transmission medium, detectornote: Optical trans. System: light source, transmission medium, detector
A pulse of light “1”; absence of light “0”
Fiber Cables
(a) Side view of a single fiber.(a) Side view of a single fiber. (b) End view of a sheath with three fibers.
Fiber Cables (2)( )
A comparison of semiconductor diodes and LEDs as light sourcesA comparison of semiconductor diodes and LEDs as light sources.
Fiber Optic Networksp
A fiber optic ring with active repeatersA fiber optic ring with active repeaters.
Fiber Optic Networks (2)p ( )
A passive star connection in a fiber optics networkA passive star connection in a fiber optics network.
Wireless Transmission
Li ht T i i• Lightwave Transmission
The Electromagnetic Spectrumg p
Radio Transmission
(a) In the VLF, LF, and MF bands, radio waves follow the curvature of the earth.
(b) In the HF band, they bounce off the ionosphere.
Politics of the Electromagnetic Spectrumg p
The ISM (Industrial Scientific Medical unlicensed) bands in the UnitedThe ISM (Industrial, Scientific, Medical, unlicensed) bands in the United States.
Lightwave Transmissiong
Communication Satellites
*Communication Satellites
Communication satellites and some of their properties, including altitude above the earth, round-trip delay time and number of satellites needed for global coverage
Note: (magnetosphere)(Van Allen Belt)
Communication Satellites (2)( )
Communication Satellites (3)( )
VSATs (Very Small Aperture() Terminal) using a hubVSATs (Very Small Aperture() Terminal) using a hub.
Low-Earth Orbit Satellites IridiumIridium
(a) (b)
(a) The Iridium satellites from six necklaces around the earth.( ) (b) 1628 moving cells cover the earth.
Globalstar
(a) Relaying in space.(a) Relaying in space. (b) Relaying on the ground.
Public Switched Telephone Systemp y
• Structure of the Telephone Systemp y • The Politics of Telephones • The Local Loop: Modems, ADSL and Wireless • Trunks and MultiplexingTrunks and Multiplexing • Switching
Structure of the Telephone Systemp y
(a) Fully-interconnected network. (b) Centralized switch. (c) Two-level hierarchy.
Structure of the Telephone System (2)p y ( )
A typical circuit route for a medium-distance callA typical circuit route for a medium distance call.
Major Components of the Telephone System
L l l• Local loops Analog twisted pairs going to houses and businesses
• TrunksTrunks Digital fiber optics connecting the switching officesoffices
• Switching offices Where calls are moved from one trunk to another
The Politics of Telephonesp
The relationship of LATAs(Local Access and Transport Areas), LECs(Local Exchange Carrier), and IXCs(IntereXchange Carrier). All the circles are LEC switching offices. Each
hexagon belongs to the IXC whose number is on it.
The Local Loop: Modems, ADSL, and Wireless
The use of both analog and digital transmissions for a computer toThe use of both analog and digital transmissions for a computer to computer call. Conversion is done by the modems and codecs.
Modems
(a) A binary signal (c) Frequency modulation(a) A binary signal (b) Amplitude modulation
(c) Frequency modulation (d) Phase modulation
Modems (2)( )
Modems (3)( )
(a) (b)
( ) ( )
Digital Subscriber Linesg
Bandwidth versus distanced over category 3 UTP for DSLBandwidth versus distanced over category 3 UTP for DSL.
Digital Subscriber Lines (2)g ( )
Operation of ADSL using discrete multitone modulationOperation of ADSL using discrete multitone modulation.
Digital Subscriber Lines (3)g ( )
Wireless Local Loops (802.16)p ( )
Frequency Division Multiplexingq y p g
(a) The original bandwidths. (b) The bandwidths raised in frequency(b) The bandwidths raised in frequency. (b) The multiplexed channel.
Wavelength Division Multiplexingg p g
Wavelength division multiplexingWavelength division multiplexing.
Time Division Multiplexingp g
Delta modulationDelta modulation.
Multiplexing T1 streams into higher carriersMultiplexing T1 streams into higher carriers.
Time Division Multiplexing (4)p g ( )
Two back-to-back SONET framesTwo back to back SONET frames.
Time Division Multiplexing (5)p g ( )
SONET and SDH multiplex ratesSONET and SDH multiplex rates.
Circuit Switchingg
Message Switchingg g
Packet Switchingg
The Mobile Telephone Systemp y
Fi t G ti M bil Ph• First-Generation Mobile Phones: Analog Voice
• Second Generation Mobile Phones:• Second-Generation Mobile Phones: Digital Voice
• Third-Generation Mobile Phones:• Third-Generation Mobile Phones: Digital Voice and Data
Advanced Mobile Phone Systemy
(a) Frequencies are not reused in adjacent cells. (b) To add more users, smaller cells can be used.
Channel Categories (AMPS)g ( ) The 832 channels are divided into four categories:g
• Control (base to mobile) to manage the systemControl (base to mobile) to manage the system
• Paging (base to mobile) to alert users to calls• Paging (base to mobile) to alert users to calls for them
• Access (bidirectional) for call setup and h l i tchannel assignment
• Data (bidirectional) for voice, fax, or data
D-AMPS Di it l Ad d M bil Ph S tDigital Advanced Mobile Phone System
( ) A D AMPS h l ith th(a) A D-AMPS channel with three users. (b) A D-AMPS channel with six users.
GSM Global System for Mobile CommunicationsGlobal System for Mobile Communications
GSM uses 124 frequency channels each of whichGSM uses 124 frequency channels, each of which uses an eight-slot TDM system
GSM (2)( )
A portion of the GSM framing structure.A portion of the GSM framing structure. Slot 12 CTL: control channel: paging, random access and access grant
CDMA – Code Division Multiple Accessp
a) Each station is assigned a unique m-bit chip sequence.(00011011) b) To transmit a 1 bit, sends its chip seq; to transmit a 0 bit, sends
one’s complement of its chip seq. c) B bits/s m B bits/s ( spread spectrum) d) Walsh codes: all chip seq’s are pairwise orthogonal. Two chip seq’s
ST=0 (two different stations). SS (the same station)=1 and S[S(bar)} 1S[S(bar)}=-1
*CDMA – Code Division Multiple Accessp
(a) Binary chip sequences for four stations (b) Bipolar chip sequences ( ) p p q (c) Six examples of transmissions (d) Recovery of station C’s signal
Third-Generation Mobile Phones: Digital Voice and DataDigital Voice and Data
Basic services an IMT-2000 network should provide
• High-quality voice transmission • Messaging (replace e-mail, fax, SMS, chat, etc.) • Multimedia (music videos films TV etc )• Multimedia (music, videos, films, TV, etc.) • Internet access (web surfing, w/multimedia.)
Cable Television
• Community Antenna Television I t t C bl• Internet over Cable
• Spectrum Allocationp • Cable Modems
Community Antenna Televisiony
Internet over Cable
Cable televisionCable television
Spectrum Allocationp
Frequency allocation in a typical cable TV systemFrequency allocation in a typical cable TV system used for Internet access
Cable Modems
Typical details of the upstream and downstreamTypical details of the upstream and downstream channels in North America.
Chap.2 Homeworkp
