Chapter 4

Chapter 4

Transmission of Digital Data / Media & Service

Satellite dish

Satellite

Radio Tower

BY Dr.Sukchatri Prasomsuk

Contents :

• 4.1 Digital Data Transmission• 4.2 DTE-DCE Interface• 4.3 Modems • 4.4 Type of Transmission Media

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4.1 Digital Data Transmission

• Communication Mode :

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• Data Transmission

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Data Transmission

Parallel Serial

Synchronous Asynchronous


• Parallel vs Serial line

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• Parallel Transmission : Transmission in which bits in a group are sent simultaneously, each using a separate link.

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Sender ;Computer

LPT1,LPT2,LPT3,etc.

Receiver ;Printer,Plotter, Circuit,

etc,

8 bits


• Serial Transmission : Transmission of data one bit at a time using only one single link.

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Sender(RS232)

0 1

0 1

0 1

0 1

Receiver(RS232)

0 1

0 1

0 1

0 1

Parallel/Serial Converter

0 1 0 1 0 1 0 1

8 bits are sent


• Asynchronous Transmission : Transfer of data with start and stop bit(s) and a variable time interval between data units.

• We send one start bit (0) at the beginning and one or more stop bits (1s) at the end of each byte. There may be a gap between each byte.

• Asynchronous here means “asynchronous at the byte level” but the bits are still synchronized; their durations are the same.

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• Asynchronous Transmission : Clock independent

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Sender Receiver11010011101100011110 110011

Start bitStop bit

Gaps

Data

Direction of flow


• Asynchronous Transmission :

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• Synchronous Transmission : A transmission method that requires a constant timing relationship between the sender and the receiver.

• We send bits one after another without start/stop bits or gaps. It is the responsibility of the receiver to group the bits.

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• Synchronous Transmission : Clock dependent

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Sender Receiver10100111 10001111 11001101

Data

Direction of flow


• Bit Oriented synchronization :

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• Character Oriented synchronization : BiSync

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4.2 DTE-DCE Interface

• Data Terminal Equipment (DTE) : A device that is an information source or an information sink. It is connected to a network through a DCE.

• Data Circuit-Terminal Equipment (DCE) : A device used as an interface between a DTE and a network.

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• Data Terminal Equipment (DTE) : is any device that is a source of or destination for binary digital data.

• Data Circuit-Terminal Equipment (DCE) : is any device that transmits or receives data in the from of an analog or digital signal through a network.

• Interface : the electrical specification of EIA-232 defines that signals other than data must be sent using OFF -> lessthan -3 Volts and ON -> greater than +3 Volts

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DTE DCE DTEDCEI nternet / Netw ork

Interface; ~ 15 m.EIA-232,EIA-442,EIA-449

InterfaceEIA-232,EIA-442,EIA-449

Data Terminal EquipmentEnd of the user’s deviceon the WAN link

Data Communications Equipment• End of the WAN provider’s

side of the communication facility• DCE is responsible for clocking

DCEDTE

ModemCSU/DSU

DTE DTEDCE DCE

4.2 DTE-DCE Interface Serial Implementation of DTE vs DCE

4.2 DTE-DCE Interface Serial Implementation of DTE vs DCE

Internet

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CSU/DSU

End user

device

Service Provider

DTE

DCE

4.2 DTE-DCE Interface Serial Point-to-Point Connections

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4.2 DTE-DCE Interface Fixed Interfaces4.2 DTE-DCE Interface Fixed Interfaces

Router—rear view

Serial WAN ports can be fixed

4.2 DTE-DCE Interface Modular Interfaces

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Console

Router—rear view

Ethernet AUIEthernet 10BaseT ISDN BRI S/T

Serial WAN ports can be modular

Module

WAN Interface

Card

4.3 Modems

• Modem stands for MOdulator/DEModulator. • Modem is a communication device that converts

binary signal into analog acoustics signal for transmission over telephone lines and converts these acoustics signals back into binary form at the receiving end.

• A Modulator converts a digital signal into an analog signal using ASK, FSK, PSK or QAM.

(Digital-to-Analog)• A Demodulator converts an analog signal into a

digital signal. (Analog-to-Digital)

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4.3 Modems

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4.3 Modems

• Modem Type :• 1. Asynchronous : for Low speed

communication• 2. Synchronous : for High speed

communication• 3. Half-Duplex : must alternately send

and received signals. • 4. Full-Duplex : can simultaneously

handle two signals using two carriers to transmit and receive data.

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4.3 Modems

• Signal Constellation

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4.3 Modems

• Constellation Samples :

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4.3 Modems

• Some Standard :• V29 : -Transmission rate up to 9600 bps• V.32bis : -2-dimensional TCM with 128

points -Transmission rate up to 14,400

bps• V.32ter : -2-dimensional TCM with 512


bps• V.34 : -2-dimensional TCM with 768


bps

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4.3 Modems

• Error Correcting :• LAPD (Link Access Protocol D) : based on

HDLC synchronous protocol.• MNP (Microcom Networking Protocol) : trademark

of Microcom• TCM : modulation with error detecting code• V.42 : CRC error correcting standard

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4.3 Modems

• Fallback :

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4.3 Modems

• Intelligent Modems : contain software to support a number of additional functions, such automatic answering and dialing.

• The AT command format is : AT command [parameter] command

[parameter] command [parameter] ...

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4.3 Modems

• Hayes Commands set :

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4.3 Modems

• Hayes Response Code :

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4.4 Type of Transmission Media

• Transmission media can be divided into two broad categories:

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Transmission Media

Guided UnGuided

Twisted-paircable

Coaxialcable

F/Ocable

Microwave Satellite Cellular

- Radio wave (Wireless)


• Twisted-pair cable: UTP (100 Hz - 5 MHz)

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• Twisted-pair cable : STP (100 Hz - 5 MHz)

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• UTP Category (CAT):• Category 1 : for telephone systems, low speed.• Category 2 : for voice and data transmission of

up to 4 Mbps.• Category 3 : transmission of up to 10 Mbps.

(Standard cable for telephone system)• Category 4 : transmission of up to 16 Mbps.

Category 5 : transmission of up to 100 Mbps. • Category 6 : transmission of up to 250 Mbps.

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Differentiating between Connections

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AUI connectors are DB15

ISO 8877 (RJ-45) connectors and jacks are slightly larger than RJ-11 phone connectors and

jacks

Fiber Connector Port

UTP Device

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The RJ-45 Connector

1

8

8 Pair 4 R4

1234567

Wire PairT is TipR is RingPair 2 T2Pair 2 R2Pair 3 T3Pair 1 R1Pair 1 T1Pair 3 R3Pair 4 T4

Pin

UTP Implementation Straight-through

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Wires on cable ends are in same order

Pin Label1 RD+2 RD-3 TD+4 NC5 NC6 TD-7 NC8 NC

Cable 10BaseT/100BaseT Straight-through

Pin Label1 TD+2 TD-3 RD+4 NC5 NC6 RD-7 NC8 NC

Server/Router

8 1

1

8

Straight-through Cable

81Hub/Switch

8 1

o

UTP Implementation Crossover

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Some wires on cable ends are crossed

8 1

og

Cable 10BaseT/100BaseT Crossover



Crossover Cable

18 1

8

8 1

br

Hub/Switch Hub/Switch


• Coaxial Cable : (100 KHz - 500 MHz)• RG-8, RG-9, RG-11 used in thick Ethernet, Radio• RG-58 used in thick Ethernet, Radio Transmitter• RG-59 used for TV

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• Fiber Optic Cable : Typical

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• Fiber Optic Cable : Cable Structures

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• Fiber Optic Cable : Optical Comparison

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• Fiber Optic Cable : Light Source

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• Fiber Optic Cable : Transmission Mode

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• Telephone system :

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Exchange

Subscriber line

ConnectorHole

Pipe

TRUNK

Central Office

Exchange

Exchange

CitySatellite dish


• Intra-Office cable :

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Radio Tower

Exchange

CitySubscriber line

Termimal Box

SD wire Drop wire

ConnectorHole

ConnectorHole

Pipe

TRUNK

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Comparing Ethernet Media Requirements

Comparing Ethernet Media Requirements

10Base5 100BaseTX

10BaseT 100BaseFX

Media

Maximum Segment Length

Topology

Connector

50-ohm coax (thick)

500 meters

Bus

100 meters

Star Star Point-to-Point

EIA/TIA Cat3, 4, 5 UTP

2 pair

EIA/TIA Cat5 UTP2 pair

62.5/125 micron multi-

modeF/O

AUIISO 8877 (RJ-45)

Duplex media-interface connector (MIC) ST

ISO 8877 (RJ-45)

400 meters100 meters


• UnGuided Media :• Unguided media or wireless communication,

transport electromagnetic waves without using a physical conductor. Instead, signals are broadcast through air.

• VLF : Very low frequency (3KHz-30KHz)--Suface• LF : Low frequency (30KHz-300KHz)--Suface • MF : Middle frequency (300KHz-3MHz)--

Tropospheric• HF : High frequency (3MHz-30MHz) --Ionospheric• VHF:Very high frequency (30MHz-300MHz)-Space & line of

sight• UHF : Ultra high frequency (300MHz-3GHz) --Space• SHF : Super high frequency (3GHz-30GHz) --Space• EHF : Extremely high frequency (30GHz-300GHz) --Space50/63


• Wireless Communication :

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• UnGuided Media : Microwave

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4.4 Type of Transmission Media Diagram of a microwave repeater

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AMPLIFIER CONVERTERPOWER

AMPLIFIER

RECEIVING ANTENNA TRANSMITTING ANTENNA


Typical repeaters required of a 20 GHz System

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TRANSMITTER REPEATER 1

Repeater Unit

REPEATER 2

Repeater Unit

RECEIVER

25 Miles


• UnGuided Media : Satellite

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• UnGuided Media : Satellite Band

C-Band : 4-6 GHz ; 5.925-6.425 GHz Uplink, 3.7 - 4.2 HGz Downlink

X-Band : 7-8 GHz

Ku-Band : 11-14 GHz ; 14 - 14.5 GHz Uplink, 11.7 - 12.2 GHz

Downlink

K-Band : 20-30 GHz

Ka-Band : 20-44 GHz

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• UnGuided Media : Geostationary Satellite

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• UnGuided Media : Cellular Telephony

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• UnGuided Media : Frequency band 900 MHz

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Base Station

Uplink890-915 MHz999 Channels

Downlink935-960 MHz999 Channels

Dulplex distance 45 MHz


• Comparison of Media :

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• Ex. VSAT design for bank system

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Microwave towerMain Computer

Head Office(Bangkok)

Microwave towerHub Station Satellite dish

PC Terminal PC Terminal PC Terminal



Satellite

Branch OfficeDPU / Controller



SAMART TELCOMS


• Factor to select media :

• Cost• Data rate and Bandwidth• Distance

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Q/A

• Thank you

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Chapter 4

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