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Information Technology in Business:

Telecommunications and Networks

Chapter 6

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Telecommunications:

Transmittal of data from one computer to another over a distance

Telecommunications has improved business in three main ways: Better communication Higher efficiency Better distribution of data

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What is the Different betweenCommunication

and Telecommunication ?

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What is Data Communications?

Data Communications is Any transfer of data

within a computer, between a computer and another device, or between two computers

Two Basic Modes Parallel transmission Serial transmission

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Communication Direction

Three Modes of Communication Between Devices Simplex

One-way in one direction Half-Duplex

One-way in two directions Full-Duplex

Two-way in two directions

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Asynchronous Communication

In asynchronous transmission, the devices are not synchronized by any timing aids.

Advantage of asynchronous transmissionDoes not need sophisticated and expensive timing

hardware Disadvantage of asynchronous transmission

Overhead, time spent transmitting bits that are not a part of the primary data

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Synchronous Communication

In synchronous communication, data are transmitted using timing devices.

Messages are transmitted in packets.

Advantage of synchronous communicationOverhead in synchronous communication is

significantly smaller than in asynchronous communication.

Synchronous transmission

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Channels and Media

Media A medium is any

means by which data can be transmitted.

Transmission speed A medium’s capacity

is determined by the range of bits per second at which it can operate.

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Channels and Media

Twisted Pair Telephone line made of a pair of copper wires

twisted to reduce electromagnetic interference (EMI)

Coaxial Cable Commonly used for cable television transmission

More expensive than twisted pair Greater transmission rate than twisted pair Much less susceptible to EMI

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Channels and Media

Microwaves High-frequency, short radio-frequency

(RF) waves Terrestrial microwave Satellite microwave

Optical Fiber Fiber-optic technology uses light

instead of electricity to transmit data.

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Channels and Media

Characteristics of channel media

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MEDIUMMEDIUM SPEEDSPEED COSTCOST TWISTED WIRETWISTED WIRE 300 BPS - 10 MBPS300 BPS - 10 MBPS LOWLOW

MICROWAVEMICROWAVE 256 KBPS - 100 MBPS256 KBPS - 100 MBPS

SATELLITESATELLITE 256 KBPS - 100 MBPS256 KBPS - 100 MBPS

COAXIAL CABLECOAXIAL CABLE 56 KBPS - 200 MBPS56 KBPS - 200 MBPS

FIBER OPTICSFIBER OPTICS 500 KBPS - 10 GBPS500 KBPS - 10 GBPS HIGHHIGH BPS BPS : BITS PER SECOND: BITS PER SECOND KBPSKBPS: KILOBITS PER SECOND: KILOBITS PER SECOND MBPSMBPS: MEGABITS PER SECOND: MEGABITS PER SECOND GBPS:GBPS: GIGABITS PER SECOND GIGABITS PER SECOND

SPEEDS & COST OF MEDIA

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OTHER SERVICES:

DIGITAL SUBSCRIBER LINE (DSL): enhancing capacity over copper telephone lines

CABLE MODEM: modem for cable TV for high-speed access to Internet

T1 LINE: dedicated telephone connection, 24 channels @ 1.544 megabits per second

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Analog vs. Digital Analog signals: A continuous series of waves

Digital signals: A series of discrete bits

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MODEMDevices that modulate and demodulate signals

Modulation: Modification of a digital signal into an analog signal

Demodulation: Modification of an analog signal into a digital signal

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Modulation

Amplitude Modulation (AM)

Frequency Modulation (FM)

Figure 6.8 Signal modulation

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Multiplexers

Devices that allow several telephones or computers to transmit data through a single lineFrequency division multiplexing

Time-division multiplexing

Multiplexing

Frequency division

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Networks

LANs (Local Area Networks) Networks within a building, or within a group of

adjacent buildings

WANs (Wide Area Networks) Networks that cross organizational boundaries or

reach outside the companyValue-added networks (VANs)Wireless communication

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Where wireless LANs are a good choice

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Networks

Network Topology Physical layout of the nodes in a network

StarRingBusTree

Network topologies

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Protocols

Communication protocols Rules governing the communication between

computers or between computers and other computer-related devices

Network protocols Rules governing a network of devices

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Some communications software allows a user to establish protocols: bit rate, parity, number of

data bits, stop bits, and a handshake procedure.

Protocols

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Figure 6.14 The seven layers of the OSI model

Protocols

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Switching Techniques and Transfer Modes

Circuit Switching:Message is communicated in its entirety from the transmitting computer to the receiving computer

Packet Switching:Message is divided into packets of bytes and transmitted via several nodes

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The Changing Business Environment

Cellular Phones Teleconferencing Voice Mail Facsimile

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Ethical and Societal IssuesTelecommuting: Pros and Cons

Pros Saves travel cost and time Decreases pollution May reduce unemployment. Productivity higher among telecommuters

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Cons Employers tend to pressure telecommuters

to work harder than workers in the office.

May negatively impact some segments of the economy

RestaurantsDowntown business and industries

Ethical and Societal IssuesTelecommuting: Pros and Cons