meljun cortes computer information processing chapter 6 with notes

7/31/2019 MELJUN CORTES Computer Information Processing Chapter 6 With Notes

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CCT101: Chapter 6

Communications and Networks (Part 1)



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



COMMUNICATIONS

• A process in which one computer transfers data,

instructions, and information to another computer(s)

• Sending device

• Communications channel

• Communication device

• Receiving device



USES OF COMMUNICATIONS

• E-mail

• Voice mail

• Fax

• Telecommuting

– Allows employees work away from the standard workplace

• Videoconferencing

• Groupware

– Helps people work together and share information over a

network



USES OF COMMUNICATIONS

• Bulletin Board System

– Maintains a centralized collection of electronic messages

• The Internet

– The Web – E-commerce

– Telephony



COMMUNICATIONS CHANNEL

• Transmission media

– Physical

– Wireless



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



WIRELESS TRANSMISSION MEDIA

• Broadcast Radio

– Long distance

– Station frequencies assigned by FCC (Federal Communications

Commission)• AM

• FM

– Slow

– Susceptible to noise




• 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




• Microwaves

– High-speed

– Microwave stations

•

Earth-based reflective dish – Line-of-sight transmission

• Avoid possible obstructions




• Communications Satellite

– Space station receives signals and re-transmits the signals

• Uplink

•

Downlink – VSAT (Very Small Aperture Terminal)

• Involve transmitting small amounts of data




• Infrared (IR)

– Uses infrared light waves

– Line-of-sight

– IrDA ports



TRANSMISSIONS CHARACTERISTICS

• Signal Type: Analog or Digital

– Analog signals are continuous wave

– Digital signals are electrical pulses




• Broadband Vs Baseband

– Broadband transmission: The media can transmit multiple

signals simultaneously

–

Baseband transmission: The media can transmit one signal at atime only




• Transmission Modes: Asynchronous and Synchronous

– Asynchronous - irregular intervals

– Synchronous - regular intervals




• 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




• Transmission rates

– Bandwidth

• Range of frequencies that a transmission medium can carry in a

given period of time

– Measured in bits per second (bps)



THE TELEPHONE NETWORK

• Public Switched Telephone Network (PSTN)

• Plain Old Telephone Service (POTS)

• Uses variety of media




• 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




• Dedicated Lines

– ISDN (Integrated Services Digital Network) lines

– Digital subscriber lines (DSL)

–

T-carrier lines – Asynchronous transfer mode (ATM)



COMMUNICATIONS SOFTWARE

• Dialing

• File transfer

• Terminal emulation

• Internet access

meljun cortes computer information processing chapter 6 with notes

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