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Chapter 1: Introduction

Chapter 1: Introduction. Business Data Communications, 4e. Information & Communication. Generation and transfer of information is critical to today’s businesses Flow of information both mirror and shape organizational structures Networks are the enabling technology for this process.

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Chapter 1: Introduction

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  1. Chapter 1: Introduction Business Data Communications, 4e

  2. Information & Communication • Generation and transfer of information is critical to today’s businesses • Flow of information both mirror and shape organizational structures • Networks are the enabling technology for this process

  3. The “Manager’s Dilemma” • Technology is necessary for competitiveness • Cost of technology has decreased • Reliance on technology has increased • Number of choices have increased • Choices are both more difficult and more important

  4. Business Information Requirements • Voice • Data • Image • Video

  5. Distributed Data Processing • Centralized processing • Distributed processing • Hybrid systems

  6. Transmission of Information • Transmission and transmission media • e.g. twisted pair, fiber, wireless, coax • Communication Techniques • encoding, interface, protocols • Transmission efficiency • multiplexing, compression

  7. Networks • Wide Area Networks • Local Area Networks • Wireless Networks

  8. Communications Software • TCP/IP • Distributed Applications • Client/Server Architectures & Intranets

  9. Management Issues • Doing Business on the Internet • Network Management • Network Security

  10. Communications Standards • Importance • Process • Organizations

  11. Resources • Web Sites • Usenet Newsgroups • Journals • Business-oriented • Technical

  12. Telecommunication • Uses electricity to transmit messages • Speed of electricity dramatically extends reach • Sound waves: ~670 mph • Electricity: ~186,000 (speed of light) • Bandwidth= information-carrying capacity of a channel

  13. Data Communication • Adding storage overcomes time constraints • Store-and-forward communication • E-mail, voice mail, facsimile, file transfer, WWW

  14. Analog Data • Continuous signal • Expressed as an oscillation (sine wave format) of frequency • Example: Analog electrical signal generated by a microphone in response to continous changes in air pressure that make up sounds

  15. Basic Analog Terms • Wave frequency: Number of times a cycle occurs in given time period • Wave amplitude: Height of a wave cycle • Hertz: The number of times a wave cycle occurs in one second (commonly used measure of frequency)

  16. Analog Signaling phase difference • represented by sine waves 1 cycle amplitude (volts) time (sec) frequency (hertz) = cycles per second

  17. Digital Data • Represented as a sequence of discrete symbols from a finite “alphabet” of text and/or digits • Rate and capacity of a digital channel measured in bits per second (bps) • Digital data is binary: uses 1s and 0s to represent everything • Binary digits can be represented as voltage pulses

  18. Basic Digital Terms • Bit: digit in a binary number • 1 is a 1-bit number (=1 in base 10) • 10 is a 2-bit number (=2 in base 10) • 10011001 is an 8-bit number (=153 in base 10) • Byte: eight bits

  19. VIViD Communication • Voice • Image • Video • Data

  20. Converting Voice • What makes sound? Vibration of air • How can we record that vibration? • How can we convert that to an electrical signal?

  21. Analog Voice Communication • Primarily used for transmission of human voice (telephony) • Microphone captures voice vibrations, converts them to waves than can be expressed through variations of voltage • Examples • Telephone (3000Hz) • Hi-Fi Sound (15,000Hz; approximate range of human ear) • Compact Disc (20,000Hz for each of two channels)

  22. Digital Voice Communication • For good representation, must sample amplitude at a rate of at least twice the maximum frequency • Measured in samples per second, or smp/sec • Telephone quality: 8000smp/sec, each sample using 8 bits • 8 bits * 8000smp/sec = 64kbps to transmit • CD audio quality: 44000smp/sec, each sample using 16 bits • 16 bits * 44000smp/sec = 1.41mbps to transmit clearly

  23. Converting Images • Break image up into small units • More units means more detail • Units called pixels • Use photocell to read each unit, assign value • How can we represent those units electrically? • PACMAN example

  24. Image Quality Issues • More pixels=better quality • More compression=reduced quality • “Lossy” gives from 10:1 to 20:1 compression • “Lossless” gives less than 5:1 • Less compression=reduced speed of transfer • Choices in imaging technology, conversion, and communication all affect end-user’s satisfaction

  25. Video Communication • Sequences of images over time • Same concept as image, but with the dimension of time added • Significantly higher bandwidth requirements in order to send images (frames) quickly enough • Similarity of adjacent frames allows for high compression rates

  26. Data Communication • In this context, we mean data stored on computers • Already digital, so no conversion necessary • Bandwidth usually affects speed, but not quality • Examples?

  27. Bandwidth Requirements • Review chart on page 27 • What happens when bandwidth is insufficient? • Poor quality or slow transmission • How long does it take to become impatient? • Is data communication ever “fast enough”?

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