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Understanding Digital Transmission in Computer Networks

Explore pulse rate, bit rate calculations, synchronization issues, line coding schemes, and encoding techniques in digital transmission within computer networks. Learn about various encoding methods like unipolar, polar, NRZ-L, NRZ-I, RZ, Manchester, and Bipolar AMI.

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Understanding Digital Transmission in Computer Networks

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  1. Chapter 4 DigitalTransmission Computer Networks

  2. Example 1 A signal has two data levels with a pulse duration of 1 ms. We calculate the pulse rate and bit rate as follows: Pulse Rate = 1/ 10-3= 1000 pulses/s Bit Rate = Pulse Rate x log2 L = 1000 x log2 2 = 1000 bps Computer Networks

  3. Example 2 A signal has four data levels with a pulse duration of 1 ms. We calculate the pulse rate and bit rate as follows: Pulse Rate = = 1000 pulses/s Bit Rate = PulseRate x log2 L = 1000 x log2 4 = 2000 bps Computer Networks

  4. Figure 4.3DC component Computer Networks

  5. Figure 4.4Lack of synchronization Computer Networks

  6. Example 3 In a digital transmission, the receiver clock is 0.1 percent faster than the sender clock. How many extra bits per second does the receiver receive if the data rate is 1 Kbps? How many if the data rate is 1 Mbps? Solution At 1 Kbps: 1000 bits sent 1001 bits received1 extra bps At 1 Mbps: 1,000,000 bits sent 1,001,000 bits received1000 extra bps Computer Networks

  7. Figure 4.4Lack of synchronization Computer Networks

  8. Example 3 In a digital transmission, the receiver clock is 0.1 percent faster than the sender clock. How many extra bits per second does the receiver receive if the data rate is 1 Kbps? How many if the data rate is 1 Mbps? Solution At 1 Kbps: 1000 bits sent 1001 bits received1 extra bps At 1 Mbps: 1,000,000 bits sent 1,001,000 bits received1000 extra bps Computer Networks

  9. Figure 4.5Line coding schemes Computer Networks

  10. Note: Unipolar encoding uses only one voltage level. Computer Networks

  11. Figure 4.6Unipolar encoding Computer Networks

  12. Note: Polar encoding uses two voltage levels (positive and negative). Computer Networks

  13. Figure 4.7Types of polar encoding Computer Networks

  14. Note: In NRZ-L the level of the signal is dependent upon the state of the bit. Computer Networks

  15. Note: In NRZ-I the signal is inverted if a 1 is encountered. Computer Networks

  16. Figure 4.8NRZ-L and NRZ-I encoding Computer Networks

  17. Figure 4.9RZ encoding Computer Networks

  18. Note: A good encoded digital signal must contain a provision for synchronization. Computer Networks

  19. Figure 4.10Manchester encoding Computer Networks

  20. Note: In Manchester encoding, the transition at the middle of the bit is used for both synchronization and bit representation. Computer Networks

  21. Figure 4.11Differential Manchester encoding Computer Networks

  22. Note: In differential Manchester encoding, the transition at the middle of the bit is used only for synchronization. The bit representation is defined by the inversion or noninversion at the beginning of the bit. Computer Networks

  23. Note: In bipolar encoding, we use three levels: positive, zero, and negative. Computer Networks

  24. Figure 4.12Bipolar AMI encoding Computer Networks

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