Types of Transmission Media

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Types of Transmission Media

• Open-wire lines
• K carrier system
• Paired cable(twisted pairs)
• gauges and length
• high speeds 144 kbps FDX -ADSL
• Mbps rates experimentally
• Coaxial cable
• L carrier system-baseband
• CTV cable- broadband
• adapting for two-way traffic

• Microwave radio
• T carrier systems
• Satellites
• transoceanic
• direct broadcast
• Optical fiber
• high BW, low error rate
• Electronic bottleneck
• LANs, MANs, WANs
• Cellular Radio

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Optical Band
Windows
.85 m 1.3
m 1.55 m
Attenuation(dB/km)
.8 1.0 1.2
1.4 1.6
Wavelength(microns)
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Example
Window around 1.3 m 0.13 m
S/N50 dB CBW log2(1S/N)500,000 Gbps P(5 X
1014 X 100 Ph/bit)/(7.5 X 1015 ph/mw)6.66 mw
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Optical Power Sources
Item Light emitting
diode(LED) Semiconductor laser Data
rate Low(noncoherent tranS) High(coherent
trans) Mode Multmode Single
mode Distance Short(LANs) Long
(WANs) Lifetime Long life Short life Temp
sensitivity Low High Cost Low High
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Optical Networks
Ring
Star
Electronic bottlenck
All Optical
Networks
Point to Point Optical Lines
MANs
Star
Coupler
See Fig 2.2
Wavelength Division
Multiplexing(WDM)
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Advantages of Fiber

• High Bandwidth
• Low Signal-to-Noise Ratio
• Lightweight
• Electrically inert
• Hard to wiretap

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Frequency Bands
Frequency in Hz
100 102 104 106 108 1010
1012 1014 1016 1018 1020
1022 1024

Radio m wave IR UV
X-ray Gamma ray
Visible Light
104 105 106 107 108
109 1010 1011 1012 1013
1014 1015 1016
Twisted Pair Coax
Satellite
Fiber optics AM Radio FM TV
Microwave
LF MF HF VHF UHF SHF EHF THF
L S C X Ku K Ka
Radio bands
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Satellite Transmission

• Remote sites-e.g. far north
• Mobility
• Direct Access-Last mile problem
• Delay problem-0.25 roundtrip for Geo

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Keplers Third Law
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Satellite Systems
Distance to Earth Station
f
Elevation
Distance from earth
S
R
f
a
b
D
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• Keplers First and Second Laws
• Obits are elliptical with earths center as a
  focus
• Orbits sweep out areas at a constant rate

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12-20 Transponders per satellite each with 36-50
MHz Bandwidth
50 Mbps Data stream
50 MHz
or
800 voice channels(64 kbps)
Spot beams and VSAT (see pp164-166)
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Personal Communication Satellite Systems
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The Telephone System
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End-to-end Connection
CPE End office Toll office Switching
office
High BW intertoll trunks
Local loop
Local loop
Toll connecting trunks
Toll connecting trunks

• Basic Components
• Local loops -twisted pairs
• Fiber to home, fiber to curb
• Trunks - optical fiber,microwave, satellites
• Switching

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RS-232 and RS-449
Not part of telephone system
Ground
Transmit
Modem
Receive
Computer or Terminal
Request to Send
Clear to send
Data set ready
Common return
Carrier detect
Data Terminal ready
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Trunks and Multiplexing

• Frequency Division Multiplexing(FDM)
• Essentially analog
• Time Division Multiplexing
• Essentially digital

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Frequency Division Multiplexing
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First Step in Analog Multiplexing Hierarchy
1 2 . . . 12
...
48 kHz
60 108 kHz
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Analog Multiplexing Hierarchy
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Advantages of Digital Signaling

• Regeneration restores signal
• Higher data rate
• Error correction and detection
• Cheaper implementation
• Easier to maintain
• Flexible multiplexing
• Easier encryption
• Compression techniques-DPCM

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Digitization of Voice Channel
Quantizer 7 bits/sample 1 control bit/sample
64 kbps
0 4 kHz
Voice Signal
8000/sec
Sampler
Pulse Code Modulation(PCM) DPCM
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Quantization
111
110
100
Digital Output
101
Analog Input
001
011
Companding (CompressionExpansion)
010
000
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T1 Frame-Pulse Code Modulation(PCM)
Frame 1/8000125 m sec
1 2 3 23 24
F 1 2 3 ...
Channels Framing bit
Eight bits/channel slot
8000 x (24 x 8 1) 1.544 Mbps
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Digital Multiplexing Hierarchy
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Synchronous Optical Network(SONET)
Synchronous Digital Hierarchy(SDH)
Basic frame
90 bytes
B
B
B
9 rows
Section and line overhead
Payload - 87 bytes
125 m sec transmission time
Basic transmission rate 8000 x 90 x 9 x8 51.84
Mbps
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Motivation for SONET

• Interconnection of Carriers (TELCOs)
• Unifying NA, European and Japanese systems
• Multiplexing optical speeds
• Operations, administration and maintenance
• Pointers

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SONET Path
Source Mux Repeater Mux
Repeater Destination Mux
Section
Section
Section
Section
Line
Line
Path
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Synchronous Optical Network(SONET)
Synchronous Digital Hierarchy(SDH)
Basic frame
90 bytes
B
B
B
9 rows
Path Overhead
Section and line overhead
Payload - 87 bytes
125 m sec transmission time
Basic transmission rate 8000 x 90 x 9 x8 51.84
Mbps
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Optical Digital Tranmission Hierarchy
OC-1 51.84 Mbps Basic Optical Channel OC-3
155.52 Mbps 3 OC-1 OC-12 622.08 Mbps 12
OC-1 OC-24 1244.16 Mbps 24 OC-1 OC-48
2.4888 Gbps 48 OC-1
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Digital Data Streams
Analog Signals
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Circuit switching Message switching
Packet switching
Callrequest signal
1
Store and foward
2
1
Time
3
2
1
Call accept
2
3
Slope shows Propagation
3
A B C D
A B C D
A B C D
Trunks
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Switching Hierarchy - ATT
Ten regional offices fully connected with one
another
67 regional offices
Direct trunks as traffic warrants
230 primary offices
1300 toll offices
19,000 end offices
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Switch Implementation
Space division switch
Crossbar(Crosspoint) Switch
0
1
2
. . .
Connections
7
N(N-1)/2 cross points for no self connection and
FDX
...
0
1
2
7
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Multiple stages reduce cross point count
n inputs
kxn
nxk
(N/n)x(N/n)
kxn
n inputs
nxk
(N/n)x(N/n)
kxn
n inputs
nxk
k cross bars
N/n crossbars
N/n crossbars
N1000, k10
24,000 crosspoints
N(N-1)/2499,500 crosspoints
Blocking-Clos networks
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Time slot interchanger
n input lines
n output lines
0 1 2 3 4 5 6 7
4 7 6 3 0 5 2 1
RAM
N
Fig 2-40 Time division switch
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BISDN-ATM
Routing Table
Host
Switch
Trunk
Virtual Circuit
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Synchonous transmission
(each slot1 byte)
T1 frame
1 2 3 4 5 6 7 8 9 10 111213 1415 16
1718 19 202122 2324
Asynchonous transmission
6
14
3
2
One cell53 bytes
155.52 Mbps Primary rate
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ATM Switches
I/O
I/O
Switch Fabric
155 Mbps 360,000 cells/sec
Cycle time2.77 m sec
16 to 1024 input lines
Objectives 1) Low cell loss rate 2) Order
preserved

• Two basic types
• Input queueing
• Output queueing

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Input Queueing
2 3
0
1
0 3
2
3
3
3 1 1
Head-of-line blocking 58 throughput
Input Queues
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Output Queueing
0
1
2
3
100 Throughput N-fold increase in cycle time for
NxN switch
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Switch Fabrics

• Knockout Switch
• Crosspoint
• Output buffering
• calculated risk on loss

Banyan switch-self routing i.e. addresses read
directly Conflicts avoided by presorting in a
Batcher network
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Knockout Switch
Input
0 1 2 3
4 5 6 7
Output
0 1
7
Consentrator
Output Buffer
Crossbar Size limitation
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Banyan switch(Self-routing )
000
0
101
1
001
2
010
3
011
101
4
100
5
101
110
6
7
000
111
Output ports
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0
1
000
0
101
1
001
2
010
3
011
101
4
100
5
101
110
6
7
000
111
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Collision
000
0
101
1
001
2
010
3
011
4
111
100
5
101
110
6
7
111
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Batcher-Banyan Switch
Batcher Network (presort- pairwise)
Banyan Network
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Wireless Systems

• Paging
• messaging capability
• one way
• Limited bandwidth 930-950 MHz
• Cordless Telephone(No standardization)
• Analog Cellular Telephone-Mobile radio
• Advanced Mobile Phone System(AMPS)
• Cellular
• Frequency reuse

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Cell structure
Mobiles
Land Line
Rest of Network
Base Station
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Frequency Reuse
Colors represent different frequencies
ddistance between cells using same
frequency rcell radius d/r4.6
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Channels

• 832 FDX Channels
• 832 Transmit Simplex Channels
• 824 to 849 MHz
• 30 kHz width
• 832 Receive Simplex Channels
• 869 to 894 MHz
• 30 kHz width
• Four Categories of Channels
• Control(base to mobile) -system management
• Paging (base to mobile)- Alert mobile of call
• Access (bi-directional) - Call setup, channel
  assignment
• Data (bi-directional) -Voice, Fax, data

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A Quick History Lesson
1956 - Consent Decree-Bell Canada and Northern
Electric split off
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A Quick History Lesson
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1984 Final Judgement
Seven Operating Companies e.g. NYNEX, Bell South
ATT
Manufacturing
Bell Communications Research (Bellcore)
Long Distance
Bell Labs
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Recent Developments

• AT T splits into Lucent (Mfg) and ATT(Carrier)
• Long Distance competition in Canada, e.g. Sprint
• Stentor under pressure from competition