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Information Technology in Business: Telecommunications

and Networks

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Learning Objectives

• Explain why successful managers must be familiar with telecommunications concepts and terminology

• Describe the principles of communication within a computer system and among computers

• Identify the major media and devices used in telecommunications

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Learning Objectives (Cont.)

• List and explain the functions of different network layouts and the concept of protocols

• Explain how telecommunications can improve operations in organizations

• Cite the latest developments in telecommunications media and transmission speed

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Telecommunications in Business• 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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Telecommunications in Daily Use

• Cellular Phones

• Videoconferences

• Voice Mail

• Facsimile

• Information Kiosks

• Pay at the Pump

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• Easy Passing

• Web-Based Electronic Commerce

• Worldwide Peer-to-Peer File Sharing

– Napster, Gnutella, BearShare, Morpheus

– With directory

– Without directory

Telecommunications in Daily Use (Cont.)

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Telecommunications in Daily Use (Cont.)

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Data Communications

• Any transfer of data within a computer, between a computer and another device, or between two computers

• Parallel and Serial Data Communications

– Serial data transfer refers to transmitting data one bit at a time.

– Parallel means the device is capable of receiving more than one bit at a time (that is, it receives several bits in parallel). Most modern printers are parallel.

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Data Communications (Cont.)

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• Simplex

– One-way in one direction

• Half-Duplex

– One-way in two directions

• Full-Duplex

– Two-way in two directions

Communication Direction

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Communication Direction (Cont.)

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• Parity Check

– Error detection method

– Checks that no bits are added or deleted during transmission

Error Detection

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• Communications medium – Physical medium through which data can be

communicated– Telephone lines, television cables

• Capacity– Speed at which data are communicated– Also called the transmission rate– It is often called “bandwidth”

• Bandwidth is measured in bits per second (bps)– The greater the capacity, the faster the transmission

Bandwidth and Media

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Bandwidth and Media (Cont.)

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• Bandwidth

– Narrowband is low speed

– Broadband has greater capacity

• Media

– A medium is any means by which data can be transmitted

Bandwidth and Media (Cont.)

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• A medium’s capacity is determined by the range of bits per second at which it can operate

• Baud is the number of signals per minute

– e.g. 300 bits per second = 300 baud

• Repeater receives and strengthens signals before sending them on

Transmission speed

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Transmission Speed (Cont.)

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• Telephone line made of a pair of copper wires twisted to reduce electromagnetic interference (EMI)

Twisted Pair

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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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• High-frequency, short radio-frequency (RF) waves

– Terrestrial microwave

– Satellite microwave

Microwaves

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Optical Fiber

• Fiber-optic technology uses light instead of electricity to transmit data– SUPER CLEAR GLASS STRANDS

– FAST, LIGHT, DURABLE

– TRILLIONS OF BITS PER SECOND, FULL DUPLEX

– EXPENSIVE, HARDER TO INSTALL

– OFTEN USED AS BACKBONE OF NETWORKS

SIGNALSIGNAL LASERLASER CABLECABLE PHOTOPHOTODETECTORDETECTOR SIGNALSIGNAL

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Characteristics of Media

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Modulation• Modification of a digital signal into an analog signal

• Demodulation

– Modification of an analog signal into a digital signal

• Modems

– Devices that modulate and demodulate signals

• Multiplexor - device that transmits multiple signals over single medium

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• Analog vs. Digital

– Analog: A continuous series of waves

– Digital: A series of discrete bits

Modulation (Cont.)

0010111010011101001010101110111100100010000101111010110100111010010010110010101101100

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Modulation (Cont.)

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Modulation (Cont.)

Figure 6.9 Multiplexing

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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 company

• Value-added networks (VANs)

• Wireless communication

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Network Topology

• Physical layout of the nodes in a network

– Star

– Ring

– Bus

– Tree

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Network Topology

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Star topology: a central host computer receives all messages and then forwards the message to the appropriate computer or device (e.g. printer) on the network. In a star topology, all communications must go through the main computer, and this topology is one of the oldest types.

Star Topology

HOSTHOST

USERUSER

USERUSER

USERUSER USERUSER

Advantage: easy to expand the network by adding more computers. This set-up is ideal when some information has to be centralized on the host computer, and other computers on the network can download that information from the host computer.

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Bus Topology• A bus topology connects all computers on the network through a

single circuit such as fiber optics, twisted pair etc to a central channel. Signals transmitted over the channel are called messages. This topology transmits each message to all computers on the network, although only the targeted device will respond to the message. Each device has an address and each device forwards messages to the address of a given device.

• Advantages: – easy to add or remove devices from the network without affecting network

performance. – if one of the devices on the network fails, the network is not affected.

• Disadvantage: network performance decreases as the number of messages increases, because each device checks to see if the message is for it, or for some other device. This topology is ideal for LAN’s and for applications such as e-mail and file transfers.

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Ring Topology• Ring Topology: network devices are connected to one

another in the shape of a closed loop, so that each device is connected directly to two other devices, one on either side of it (closed ring). This topology transmits a message to all devices between the sending node and the receiving node. Each computer communicates directly with any other computer by specifying the address of the device; the topology distributes processing and control functions among all devices on the network. If a computer on the network fails, the message is rerouted around it.

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Networking Hardware

• Network Interface Card

• Hub

• Switch

• Bridge

• Router

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Virtual Private Network

• A combination of private and public lines

• A link between a private network and the Internet

• “Virtual” refers to the illusion that the use is accessing a private network directly

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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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Protocols (Cont.)

• LAN Protocols– Polling

– Contention

– Token passing

• WAN Protocols– OSI (Open Systems Interconnection)

• Standard protocol model

• Seven layers

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Protocols (Cont.)

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Switching Techniques• 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

– TCP/IP

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Switching Techniques (Cont.)

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The Changing Business Environment

• Cellular Phones

• Teleconferencing

• Voice Mail

• Facsimile

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A Variety of Services• Cable

• Digital Subscriber Line (DSL)

• T1 and T3 Lines

• Satellite

• Fixed Wireless

• Gigabit Ethernet

• Optical Carrier

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A Variety of Services (Cont.)

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A Wireless Revolution

• Popular Wireless Technologies

• Would You Like Wi-Fi With That?

• Combining Technologies

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Wireless Technologies (Cont.)

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Wireless Technologies (Cont.)

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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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Ethical and Societal IssuesTelecommuting: Pros and Cons

• Cons

– Employers tend to pressure telecommuters to work harder than workers in the office.

– No office to foster new social ties and camaraderie.

– May negatively impact some segments of the economy

• Restaurants

• Downtown business and industries

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Summary• Telecommunications concepts and terminology

• Communication within a computer system and among computers

• Telecommunications media and devices

• Network layouts and protocols

• Telecommunications impact on operations

• Telecommunications developments and speed