Information Technology Telecommunications and Networks

Learning Objectives When you finish this chapter, you will: Recognize why successful managers must be familiar with telecommunications concepts and terminology. Know the principles of communication within a computer system and among computers. Be able to identify the major media and devices that are used in telecommunications.

Learning Objectives Be able to list and explain the functions of different network layouts and the concept of protocols. Understand how telecommunications can improve operations in organizations. Know the latest developments in telecommunications media and transmission speeds.

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

What is Data Communications? Any transfer of data within a computer, between a computer and another device, or between two computers Two Basic Modes Parallel transmission Serial transmission

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

Communication Direction Figure 6.2 Simplex, half-duplex, and full-duplex communication

Communication Direction Asynchronous Communication In asynchronous transmission, the devices are not synchronized by any timing aids. Advantage of asynchronous transmission Does 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

Communication Modes Synchronous Communication In synchronous communication, data are transmitted using timing devices. Messages are transmitted in packets. Advantage of synchronous communication Overhead in synchronous communication is significantly smaller than in asynchronous communication.

Communication Modes Figure 6.4 Synchronous transmission

Channels and Media Communication Channel Channel Capacity Physical medium through which data can be communicated. Channel Capacity Narrow band Broadband

Channels and Media Figure 6.5 Transmission speed measurement unit

Channels and Media Media Transmission speed 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.

Channels and Media Figure 6.6 Telecommunications transmission speeds of different media

Channels and Media Twisted Pair Coaxial Cable 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

Channels and Media Microwaves Optical Fiber High-frequency, short radio-frequency (RF) waves Terrestrial microwave Satellite microwave Optical Fiber Fiber-optic technology uses light instead of electricity to transmit data.

Figure 6.7 Characteristics of channel media Channels and Media Figure 6.7 Characteristics of channel media

Analog vs. Digital Analog signals Digital signals A continuous series of waves Digital signals A series of discrete bits

Modulation Modification of a digital signal into an analog signal Demodulation Modification of an analog signal into a digital signal

Figure 6.8 Signal modulation

Modulation Amplitude Modulation (AM) Frequency Modulation (FM) Phase Modulation

Modulation Modems Multiplexers Devices that modulate and demodulate signals Multiplexers Devices that allow several telephones or computers to transmit data through a single line Frequency division multiplexing Time-division multiplexing

Modulation Figure 6.9 Multiplexing

Figure 6.10 Frequency division Modulation Figure 6.10 Frequency division

Networks LANs (Local Area Networks) WANs (Wide 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

Networks Figure 6.11 Where wireless LANs are a good choice

Networks Network Topology Physical layout of the nodes in a network Star Ring Bus Tree

Figure 6.12 Network topologies Network Topology Figure 6.12 Network topologies

Protocols Communication protocols Network protocols Rules governing the communication between computers or between computers and other computer-related devices Network protocols Rules governing a network of devices

Protocols Figure 6.13 Some communications software allows a user to establish protocols: bit rate, parity, number of data bits, stop bits, and a handshake procedure.

Protocols LAN Protocols WAN Protocols Polling Contention Token passing OSI (Open Systems Interconnection) Standard protocol model Seven layers

Figure 6.14 The seven layers of the OSI model Protocols Figure 6.14 The seven layers of the OSI model

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

The Changing Business Environment Cellular Phones Teleconferencing Voice Mail Facsimile

Ethical and Societal Issues Telecommuting: Pros and Cons Saves travel cost and time Decreases pollution May reduce unemployment. Productivity higher among telecommuters

Ethical and Societal Issues Telecommuting: Pros and 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