1. 1 Information Technology in Business: Telecommunications and Networks Chapter 6

2. 2 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

3. 3 What is the Different between Communication and Telecommunication ?

4. 4 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

5. 5 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

6. 6 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

7. 7 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. Synchronous transmission

8. 8 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.

9. 9 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

10. 10 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.

11. 11 Channels and Media Characteristics of channel media

12. 12 MEDIUM MEDIUM SPEED SPEED COST COST TWISTED WIRE TWISTED WIRE 300 BPS - 10 MBPS 300 BPS - 10 MBPSLOW MICROWAVE MICROWAVE 256 KBPS - 100 MBPS 256 KBPS - 100 MBPS SATELLITE SATELLITE 256 KBPS - 100 MBPS 256 KBPS - 100 MBPS COAXIAL CABLE COAXIAL CABLE 56 KBPS - 200 MBPS 56 KBPS - 200 MBPS FIBER OPTICS FIBER OPTICS 500 KBPS - 10 GBPS 500 KBPS - 10 GBPSHIGH BPS : BITS PER SECOND BPS : BITS PER SECOND KBPS: KILOBITS PER SECOND KBPS: KILOBITS PER SECOND MBPS: MEGABITS PER SECOND MBPS: MEGABITS PER SECOND GBPS: GIGABITS PER SECOND GBPS: GIGABITS PER SECOND SPEEDS & COST OF MEDIA

13. 13 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 *

14. 14 Analog vs. Digital Analog signals: A continuous series of waves Digital signals: A series of discrete bits

15. 15 MODEM Devices 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

16. 16 Modulation  Amplitude Modulation (AM)  Frequency Modulation (FM) Figure 6.8 Signal modulation

17. 17 Multiplexers Devices that allow several telephones or computers to transmit data through a single line  Frequency division multiplexing  Time-division multiplexing Multiplexing Frequency division

18. 18 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

19. 19 Where wireless LANs are a good choice

20. 20 Networks  Network Topology Physical layout of the nodes in a network Star Ring Bus Tree Network topologies

21. 21 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

22. 22 Some communications software allows a user to establish protocols: bit rate, parity, number of data bits, stop bits, and a handshake procedure. Protocols

23. 23 Figure 6.14 The seven layers of the OSI model Protocols

24. 24 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

25. 25 The Changing Business Environment  Cellular Phones  Teleconferencing  Voice Mail  Facsimile

26. 26 Ethical and Societal Issues Telecommuting: Pros and Cons  Pros Saves travel cost and time Decreases pollution May reduce unemployment. Productivity higher among telecommuters

27. 27  Cons Employers tend to pressure telecommuters to work harder than workers in the office. May negatively impact some segments of the economy Restaurants Downtown business and industries Ethical and Societal Issues Telecommuting: Pros and Cons