SC161-Lecture4-1
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Transcript of SC161-Lecture4-1
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Chapter 4
S C 1 6 1 : P r i n c i p l e s o f I n f o r m a t i o n T e c h n o l o g y
Communication and NetworkPart 1: Data Communication
Thiti Theerathean
Center for Teaching Excellence University of the Thai Chamber of Commerce
E-mail : [email protected]
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2
• Introduction to Data Communication.- Data Communication and Telecommunication- Type of Signals - The Basic Components of Communication
• Data Transmission.- Line configurations- Direction of Transmisssion- Transmission Mode
• Communication Channel.- Guided Media- Unguided Media
• Wireless Technology.- Long-distance wireless communication- Short-range wireless communication
SC161: Principles of Information Technology
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3SC161: Principles of Information Technology
Data Communications is any transfer of data within a computer, between a computer and another device, or between two computers.
Telecommunication is communications over a distance.
Tele- distance
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4SC161: Principles of Information Technology
Data and Information travels through a communication system in the form of eletromagnetic signals. Signals are represented in two ways
• Continuous waveform.• Three basic components :
- Amplitude (Volt)- Frequency (Hz)- Phase (Radian)
• Infinite number of points between minimum and maximum amplitude.• Use an Amplifier to increase power for transmission over long distances and
reduce noise by Filter.• Used for Voice Communication.
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5SC161: Principles of Information Technology
Data and Information travels through a communication system in the form of eletromagnetic signals. Signals are represented in two ways
• Discrete waveform.• Only two different values:
- 1 is high voltage/on electrical pulses.- 0 is low voltage/off electrical pulses.
• The number of times a signal changes value per second is called “Baud rate”• Use Repeater to transmission the data over long distances.• Used for Data Communication.
time
amplitude (power)
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6SC161: Principles of Information Technology
SenderCommunication Channel
Receiver
Step 1: ……Step 2: …...Step 3: …...
Step 1: ……Step 2: …...Step 3: …...
Protocol
Message
The Basic Components of Communication.
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7SC161: Principles of Information Technology
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8SC161: Principles of Information Technology
There are two principal line configurations.
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9SC161: Principles of Information Technology
When two computers are in communication, data can flow in three ways:
A B
Only transmits. Only receives.
A B
Transmits when B receives. Transmits when A receives.
A B
Transmits and receives while B transmits and received.
Transmits and receives while A transmits and received.
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10SC161: Principles of Information Technology
Data is transmitted in two ways.
Sender Receiver
01110011 01110011
1 1 0 0 1 1 1 0
Sender Receiver
01110011 0111001101110011
Bits are transmitted sequentially, one after the other.
Bits are transmitted through separate lines simultaneously.
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11SC161: Principles of Information Technology
How does the receiving equipment know where one byte ends and another begins ?
Sender Receiver
1 1 0 0 1 1 1 0
1100111001011100
0 1 0 1 1 1 0 0 100 1
Start bit
0
Stop bit
1
Parity check bit
• Start bit and Stop bit are added.• High overhead.• low-speed communication
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12SC161: Principles of Information Technology
How does the receiving equipment know where one byte ends and another begins ?
Sender Receiver
Parity check bit
1
• basic unit transmitted is called a “packet”• Use sync bytes to announce the beginning
and end of an entire packet.
SyncSyncSync Sync
Sync byte
1 1 0 0 1 1 1 00 1 0 1 1 1 0 0
Packet
1100111001011100
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13SC161: Principles of Information Technology
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14SC161: Principles of Information Technology
Communication channels are the means by which data are transmitted from one device in a network to another. A channel can utilize different kinds of communication transmission media :
- Twisted-Pair Cable- Coaxial Cable- Fiber Optics Cable
- Infrared Transmission - Radio Frequency- Microwave and Satellite
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15SC161: Principles of Information Technology
Twisted-Pair Cable• Two insulated copper wires that are twisted together.• The pairs can be shielded (STP) or unshielded (UTP).• The standard connector for unshielded twisted pair cabling is an RJ-45 connector.
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16SC161: Principles of Information Technology
Advantages: • High availability.• Low installation cost.
Disadvantages: • Limited data rates. • Limited range.• High susceptibility to electromagnetic and
radio frequency interference.
Twisted-Pair Cable Categories: 1 - primarily for voice, less than 9600 bps2 - T-1 and ISBN line, 4 Mbps 3 - 16 MHz of bandwidth; 10 Mbps 4 - 20 MHz of bandwidth; 16 Mbps 5/5e - 100 MHz of bandwidth; 100 Mbps (4 pairs/cable) 6 - 400 MHz of bandwidth; 1Gbps (4 pairs/cable)
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17SC161: Principles of Information Technology
Twisted-Pair Cable
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18SC161: Principles of Information Technology
Coaxial Cable• A single copper wire, surrounded by an insulator and an outer conductor. • Two primary types : Thick coaxial (10mm) and Thin coaxial (4mm).• Speed : 56 kbps to 200 Mbps.
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19SC161: Principles of Information Technology
Coaxial Cable
Advantages: • High capacity (370-1000 times more than twisted pair) • Low susceptibility to noise and crosstalk (because of shielding)
Disadvantages: • Requites Amplifier or Repeater every few km. • High installation cost.
Common Uses: • Cable TV (Old: RG-59; New: RG-6) • Ethernet (RG-58:10Base2 ; RG-8:10Base5) • Amateur radio.
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20SC161: Principles of Information Technology
Fiber Optic CableA thin glass core surrounded by cladding that reflects light into the core, surrounded
by a protective plastic buffer/jacket.
• Light source is called a photo diode.• Light travels through the core and bounces off of the cladding to "make turns" • The signal degrades because of impurities in the glass
cladding
core
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21SC161: Principles of Information Technology
Fiber Optic Cable The two basic types of optical fiber.
Multi-mode optical fiber
Single-mode optical fiber
Step-index multimode
Graded-index multimode
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22SC161: Principles of Information Technology
Advantages: • High capacity.• Reduce size and weight cable.• no crosstalk and lower bit error rates.• Signal security and difficult to tap.
Disadvantages: • Can be bent.• Each fiber is one-way transmission of data.• High cost of interfaces.• Lack of standardization.
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23SC161: Principles of Information Technology
Guided Media Typical use Data Rate Range
Twisted pairCategory 1 - 2Category 3 - 6
Telephone systemLANs
Less than 2 Mbps100 Mbps
5 km.100 m (328 feet)
Coaxial CableThin (Single channel)Thick (Multi channel)
LANsLANs
Cable TV
10 Mbps10 Mbps
100 m.5 km.
Fiber Optic CableSingle-modeMulti-mode
LANsWANs
HD interconnection
10 Gbps 160 km.
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24SC161: Principles of Information Technology
Electromagnetic Spectrum.
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25SC161: Principles of Information Technology
Infrared Transmission • Using infrared-light waves at a frequency too low.• Short-range communication (no more than 5 meters)
in IrDA standard.• Cannot penetrate walls and work only in the direct
"line of sight"• Speed less than 4 Mbps.
Radio Frequencies• Distributes radio signals through the air.• Speed more than 2 Mbps.• Long distances: cellular phone, broadcast radio and TV.• Short distances: Bluetooth and Wi-Fi
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26SC161: Principles of Information Technology
Microwave • Transmits data more than 45 Mbps as High frequency radio wave.• Sending signals from one microwave station to another.• Line-of-sight transmission.
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27SC161: Principles of Information Technology
Satellite • Microwave relay station in orbit around the earth.• Transmitting a signal from a ground station is called “uplink”,
the reverse is called “downlink”
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28SC161: Principles of Information Technology
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29SC161: Principles of Information Technology
Long-distance wireless communication
The global Positioning System (GPS) consists of 24 earth-orbiting satellites continuously transmitting timed radio signals that can be used to identify earth locations.
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30SC161: Principles of Information Technology
Long-distance wireless communication
Evolution of Mobile wireless Technology
1st Generation
2nd Generation
3rd Generation
4th Generation
• Analog cellphones• Only voice communication.
• Digital cellphones• launched on the GSM standard. • Voice and data service.
• Standards defined by the ITU.• Voice data and multimedia communication.
• High speed data rate.• Support VoIP and interactive TV.
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31SC161: Principles of Information Technology
Short-range wireless communication
The Bluetooth is a short-range wireless digital standard aimed at linking devices via a piconet. The piconet typically has a range of about 10 m and a transfer rate between about 400 and 700 kbps.
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32SC161: Principles of Information Technology
Short-range wireless communication
The WiFi is a short-range wireless digital standard aimed at helping devices to communicate with hi-speed at distances up to 10 m from access points. It is known formally as an 802.11 Network.
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33SC161: Principles of Information Technology