Ch.6- telecommunications and networks Flashcards Preview

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Flashcards in Ch.6- telecommunications and networks Deck (75):
1

telecommunications

electronic transmission of signals for communications

2

telecommunications medium

material substance carries an electronic signal between a sending/ receiving device

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Networking protocol

-rules, algorithms, messages, other mechanisms, -enable software and hardware to communicate effectively

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Synchronous

as soon as sent

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Asynchronous

some delay

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Simplex channe;

data in only 1 direction,

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Half duplex channel

data in either direction, but not simultaneously (same time)

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full duplex channel

transmission in both directions + at same time

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channel bandwith

rate that data exchgd (bits per second)

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Broadband communication

telecommunications system that can exchg data very quickly

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circuit switching

-dedicated
- sets up circuit between sender and receiver before any communications can occur

12

Packet switching network

no fixed path created
-The data broken into packets, sent individually

13

Transmission media- 2 categories:
1. Guided transmission
2. wireless

1. guided along solid medium

2.signal broadcast over airways
-electromagnetic radiation

14

Twisted pair wire

Twisted pairs of copper wire, shielded/unshielded

15

coaxial cable

Inner conductor wire surrounded by insulation

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Fibre optic cable

Extremely thin strands of glass bound together
-uses light beams to send signal

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broadband over power lines

data transmitted over standard high voltage power lines

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Guided transmission types: 4

Twisted-pair wire

Coaxial cable

Fibre optic cable

Broadband over power lines

19

Near field communication

very short range wireless connectivity technology designed for cell phones and credit cards
○ When 2 NFC devices are close to each other or touching- they exchange data

- ○ Only 2 devices = peer to peer
○ By touching the " hot spot" causes peer to peer network to be established and communications flow

20

Bluetooth

-wireless communications specifications, describes how
- electronic devices can be interconnected over distances of 3-10 meters, rate of 2bps

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Ultra wideband (UWB

-extremely short pulses (50-1000 picoseconds) -transmitted across broad range radio freq. of several gigahertz

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iNFRARED TRANSMISSION

sends signal at freq of 300ghz and above
- ○ Requires line of sight and short distances

23

zIGbEE

Form of wireless communications freq used in security systems and heating and cooling trol systems

24

wI-FI

wireless telecommunications technology brand owned by the Wi-Fi alliance

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mICROWAVE TRANSMISSION

High freq (300 mhz-300ghz) signal sent through air (see fig.6.4)

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communications satellite

operates in microwave freq. range

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geostationary satellite

orbits earth directly over equator-- so appears stationary

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Low earth orbit (LEO) satellite system

employs many satellites spaced so that from any point on earth at any time, at least 1 satellite visible

29

Very small aperture terminal (VSAT)

satellite ground station w/ dish antenna smaller than 3 metres in dia.

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WIRELESS MESH

t uses many wifi access points to link series of interconnected local area networks to form wide area network capable of serving large campus or entire city

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mICROWAVE TRANSMISSION

High freq (300 mhz-300ghz) signal sent through air

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3G WIRELESS COMMUNICATION

supports wireless voice and broadband communications---3G= 3rd generation of solutions for wireless voice and data

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Global system for Mobile (GSM)

globally accepted standard for digital cellular communications

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4G WIRELESS COMMUNICATION

4th generation broaband mobile wireless- more enhanced versions

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Worldwide Interoperability for microwave access (WiMAX)

set of IEEE 802.16 wireless metro area network standards that support various types of communications access

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cOMPUTER NETWORK

communications media, devices, software to connect 2 or more computer systems or devices.

37

Personal area network (PAN)

support interconnection of information technology in range of 10 metres or so--- i.e. home network

38

Local area network (LAN)

connects computer systems and devices within small area (office, home, several floors of a building)

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metropolitan area network

connects users and their computers in geographical area that spans campus or city

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Wide area network

network that connects large geographic regions

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3 basic processing alternatives

-Cetralized
-decentralized
-distributed

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Centalized processing

processing occurs in single location (CENTRALIZED- has center)

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Decentralized processing

processing devices placed at various remote locations (not centralized, no center)

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Distributed processign

processing devices placed at remote locations but connected to each other thru a network

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File sever system

hare data through file server computing
File server sends file containing data requested

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client server architecture

servers are dedicated to special functions like database mgmt, printing, communications, program execution
○ Each server accessible by all computers in network

47

modems

elecommunications hardware
Converts (modulates/demodulates) communications signals so they can be transmitted over communications media

48

modulation

rom digital to analog

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demodulation

analog to digital

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multiplexer

combines data from multiple data sources in to a single output signal that carries many channels

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demultiplexer

receiving end; choses correct destination from many possible destinations

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front end processors

special purpose computers that manage communications to and from large computer

53

Private branch exchange (PBX)

telephone switching exchg that serves single org.
Enables users to share certain number of outside lines (trunk lines) to make telephone calls to ppl outside org.

- ○ Dial only 3-4 digits to reach anyone in org (extension?)

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SWITCH

uses physical dev. Addr in each incoming msg. on network to determine to which output port it should send msg to reach another device on same network.

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BRIDGE

connects 2 LAN's using same telecom

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ROUTER

forwards data packets (???) across 2 or more networks towards their destinations through routing.

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gATEWAY

serves as entrance to another network

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NETWORK OPERATING SYSTEM (NOS)

software that controls computer systems and devices on network and allows them to communicate with each other

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NETWORK MANAGEMENT SOFTWARE

enables mgr on networked desktop to monitor use of individual computers and shared hardware

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ENCRYPTION

converting original message into a form that can be understood only by receiver

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ENCRYPTION KEY

value that is applied (using algorithm) to set of unencrypted text to produce encrypted text or, to decrypt encrypted text

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VITRUAL PRIVATE NETWORK (VPN)

private network that uses public network (i.e. internet) to connect many remote locations

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DIGITAL SUBSCRIOBER LINE

using existing phone lines to deliver high speed internet access to homes and small biz

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ASYMMETRIC DSL (ADSL

provide connection speed from the internet to the user (download speed) hat is 3 - 4 times faster from user back to internet (upload speed)

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SYMETRIC DSL (SDSL)

used mainly by small businesses, doesn’t allow using phone same time

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VOICEMAIL

enables users to send, receive, store verbal msgs to and from other ppl

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VOICEMAILO TO TEXT

captures voice mail msg-->converts to text---> send to email acct

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REVERSE 911

delivers emergency notifications to users in a selected geographical area

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ELECTRONIC DOCUMENT DISTRIBUTION

allows sending and receiving of doc's in digital form

70

CALL CENTRE

where organization handles customer and other phone calls usually with some amount of computer automating

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AUTOMATIC CALL DISTRIBUTOR (ACD)

phone facility that manages incoming calls, handles the based on number called, and associated database of instructions

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TELECOMMUTING

use of computing devices and networks so that employees can work effectively away from office

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VIDEO CONFERENCING

enable ppl at various locations to communicate using simultaneous (same time) 2 way video and audio

74

ELECTRONIC DATA INTERCHANGE (EDI)

way to communicate data from one company to next and from one app to another in standard format,

75

ELECTRONIC FUNDS TRANSFER

trf money from one bank to another without any paper money exchanging hands