* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Management Information Systems
Survey
Document related concepts
Computer network wikipedia , lookup
Cellular network wikipedia , lookup
History of smart antennas wikipedia , lookup
Amplitude modulation wikipedia , lookup
History of telecommunication wikipedia , lookup
Universal asynchronous receiver-transmitter wikipedia , lookup
Telecommunications in Russia wikipedia , lookup
Norwegian Public Safety Network wikipedia , lookup
Transcript
Information Technology Telecommunications and Networks 1 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. 2 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. 3 Telecommunications in Business 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 4 What is Data Communications? 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 5 Communication Direction Three Modes of Communication Between Devices Simplex Half-Duplex One-way in one direction One-way in two directions Full-Duplex Two-way in two directions 6 Communication Direction Figure 6.2 Simplex, half-duplex, and full-duplex communication 7 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 8 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. 9 Communication Modes Figure 6.4 Synchronous transmission 10 Channels and Media Communication Channel Physical medium through which data can be communicated. Channel Capacity Narrow band Broadband 11 Channels and Media Figure 6.5 Transmission speed measurement unit 12 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. 13 Channels and Media Figure 6.6 Telecommunications transmission speeds of different media 14 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 15 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. 16 Channels and Media Figure 6.7 Characteristics of channel media 17 Analog vs. Digital Analog signals A continuous series of waves Digital signals A series of discrete bits 18 Modulation Modification of a digital signal into an analog signal Demodulation Modification of an analog signal into a digital signal 19 Modulation Figure 6.8 Signal modulation 20 Modulation Amplitude Modulation (AM) Frequency Modulation (FM) Phase Modulation 21 Modulation Modems 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 22 Modulation Figure 6.9 Multiplexing 23 Modulation Figure 6.10 Frequency division 24 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 25 Networks Figure 6.11 Where wireless LANs are a good choice 26 Networks Network Topology Physical layout of the nodes in a network Star Ring Bus Tree 27 Network Topology Figure 6.12 Network topologies 28 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 29 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. 30 Protocols LAN Protocols Polling Contention Token passing WAN Protocols OSI (Open Systems Interconnection) Standard protocol model Seven layers 31 Protocols Figure 6.14 The seven layers of the OSI model 32 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 33 The Changing Business Environment Cellular Phones Teleconferencing Voice Mail Facsimile 34 Ethical and Societal Issues Telecommuting: Pros and Cons Pros Saves travel cost and time Decreases pollution May reduce unemployment. Productivity higher among telecommuters 35 Ethical and Societal Issues Telecommuting: 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 36