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Chapter 2 : Business Information

This chapter explores the concepts of analog and digital data communications, including the basics of analog and digital signals, audio recording and transmission, image digitization and compression, video communication, response time, and bandwidth requirements.

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Chapter 2 : Business Information

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  1. Chapter 2 : Business Information Business Data Communications, 4e

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

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

  4. Analog Signaling phase difference 1 cycle amplitude (volts) time (sec) frequency (hertz) = cycles per second

  5. 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

  6. 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

  7. Types of Information • Audio • Data • Image • Video

  8. Understanding Audio • What makes sound? Vibration of air • How can we record that vibration? • How can we convert that to an electrical signal?

  9. Digital Audio • 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

  10. Data Communication • In this context, we mean data already stored on computers • Already digital, so no conversion from analog form necessary

  11. Understanding Images • to digitize and image, you must break it into small units • More units means more detail • Displayed units generally called pixels

  12. Image Quality Issues • More pixels=better quality=larger size • More compression=reduced quality=increased speed • “Lossy” gives from 10:1 to 20:1 compression • “Lossless” gives less than 5:1 • Format (vector vs bitmapped/raster) affects size and therefore bandwidth requirements • Choices in imaging technology, conversion, and communication all affect end-user’s satisfaction

  13. 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

  14. Response Time • User response time • System response time • Network transfer time

  15. Bandwidth Requirements • Review Figure 2.7 • What happens when bandwidth is insufficient? • How long does it take to become impatient? • Is data communication ever “fast enough”?

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