View
218
Download
0
Category
Preview:
Citation preview
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 1/21
CCT101: Chapter 6
Communications and Networks (Part 1)
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 2/21
OBJECTIVES
• Define the components required for successful
communications
•
Describe uses of communications• Identify the various types of transmission
media
• Explain the purpose of communications
software
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 3/21
COMMUNICATIONS
• A process in which one computer transfers data,
instructions, and information to another computer(s)
• Sending device
• Communications channel
• Communication device
• Receiving device
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 4/21
USES OF COMMUNICATIONS
• Voice mail
• Fax
• Telecommuting
– Allows employees work away from the standard workplace
• Videoconferencing
• Groupware
– Helps people work together and share information over a
network
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 5/21
USES OF COMMUNICATIONS
• Bulletin Board System
– Maintains a centralized collection of electronic messages
• The Internet
– The Web – E-commerce
– Telephony
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 6/21
COMMUNICATIONS CHANNEL
• Transmission media
– Physical
– Wireless
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 7/21
PHYSICAL TRANSMISSION MEDIA
• Twisted-pair cable
– Shielded twisted-pair (STP)
– Unshielded twisted-pair (UTP)
• Coaxial cable (coax) – Cable TV
– Not as susceptible to noise
• Fiber-optic cable
–Carries many signals
– High speed
– Less susceptible to noise
– Better security
– Smaller size
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 8/21
WIRELESS TRANSMISSION MEDIA
• Broadcast Radio
– Long distance
– Station frequencies assigned by FCC (Federal Communications
Commission)• AM
• FM
– Slow
– Susceptible to noise
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 9/21
WIRELESS TRANSMISSION MEDIA
• Cellular Radio – Cellular telephone
• Uses radio signals to transmit voice and digital datamessages
• Surf web
– Cells
• Division of broadcast area
• Each covers a specific geographic area and has itsown base station
– Mobile telephone switching office (MTSO)
• Sends and receives voice and data traffic to and fromthe public switched telephone network
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 10/21
WIRELESS TRANSMISSION MEDIA
• Microwaves
– High-speed
– Microwave stations
•
Earth-based reflective dish – Line-of-sight transmission
• Avoid possible obstructions
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 11/21
WIRELESS TRANSMISSION MEDIA
• Communications Satellite
– Space station receives signals and re-transmits the signals
• Uplink
•
Downlink – VSAT (Very Small Aperture Terminal)
• Involve transmitting small amounts of data
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 12/21
WIRELESS TRANSMISSION MEDIA
• Infrared (IR)
– Uses infrared light waves
– Line-of-sight
– IrDA ports
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 13/21
TRANSMISSIONS CHARACTERISTICS
• Signal Type: Analog or Digital
– Analog signals are continuous wave
– Digital signals are electrical pulses
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 14/21
TRANSMISSIONS CHARACTERISTICS
• Broadband Vs Baseband
– Broadband transmission: The media can transmit multiple
signals simultaneously
–
Baseband transmission: The media can transmit one signal at atime only
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 15/21
TRANSMISSIONS CHARACTERISTICS
• Transmission Modes: Asynchronous and Synchronous
– Asynchronous - irregular intervals
– Synchronous - regular intervals
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 16/21
TRANSMISSIONS CHARACTERISTICS
• Transmission Direction:
– Simplex
• Data flow only in one direction
• Radio
– Half-duplex
• Either direction, but only one direction at a time
• Fax machines
– Full-duplex
• Both directions at the same time • Telephone
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 17/21
TRANSMISSIONS CHARACTERISTICS
• Transmission rates
– Bandwidth
• Range of frequencies that a transmission medium can carry in a
given period of time
– Measured in bits per second (bps)
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 18/21
THE TELEPHONE NETWORK
• Public Switched Telephone Network (PSTN)
• Plain Old Telephone Service (POTS)
• Uses variety of media
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 19/21
THE TELEPHONE NETWORK
• Dial-Up Lines
– Temporary connection
– Same cost as regular phone call
–
Computers at two locations can establish a connection using themodem and PSTN
– Quality cannot be controlled by the user
7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes
http://slidepdf.com/reader/full/meljun-cortes-computer-information-processing-chapter-6-with-notes 20/21
THE TELEPHONE NETWORK
• Dedicated Lines
– ISDN (Integrated Services Digital Network) lines
– Digital subscriber lines (DSL)
–
T-carrier lines – Asynchronous transfer mode (ATM)
Recommended