1 / 35

CPET/ECET 355

CPET/ECET 355. 4. Digital Transmission Data Communications and Networking Fall 2004 Professor Paul I-Hai Lin Electrical and Computer Engineering Technology Indiana University-Purdue University Fort Wayne www.ecet.ipfw.edu/~lin. 4.1 Line Encoding.

gelsey
Download Presentation

CPET/ECET 355

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CPET/ECET 355 4. Digital Transmission Data Communications and Networking Fall 2004 Professor Paul I-Hai Lin Electrical and Computer Engineering Technology Indiana University-Purdue University Fort Wayne www.ecet.ipfw.edu/~lin 4. Digital Transmisison - Lin

  2. 4.1 Line Encoding • A process converting binary data, a sequence of bits, to a digital signal • Binary data: data, text, numbers, graphical images, audio, and video • Some characteristics: Signal levels, bit rate, dc components, self-synchronization From p. 85, Figure 4.1 of Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  3. 4.1 Line Encoding (cont.) • Signal Level vs. Data Level Three signal levels, 2 data levels From p. 86, Figure 4.2 of Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  4. 4.1 Line Encoding (cont.) • Pulse Rate vs. Bit Rate • Pulse Rate • Number of pulses per second • A pulse is the min amount of time required to send a symbol • Bit Rate • Number of bits per second • BitRate = PulseRate x Log2L • Level of signal = 2, BitRate = PulseRate • Level of signal = 4, BitRate = 2 x PulseRate • Example 1 & 2: Find Bit rate • If - Pulse rate 1000 pulses/sec, L = 2, 1000 bps • If - Pulse rate 1000 pulses/sec, L = 4, 2000 bps 4. Digital Transmisison - Lin

  5. 4.1 Line Encoding (cont.) • DC Components (undesirable) • Cannot passing through a transformer • Unnecessary energy on the line From p. 87, Figure 4.3 of Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  6. 4.1 Line Encoding (cont.) • Self-Synchronization (desirable) • For correctly interpret signal • Sending 10110001; receiving 110111000011 Figure 4.4 Lack of Synchronization, From p. 88, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  7. 4.1 Line Encoding (cont.) • Line Coding Schemes • Unipolar • Simple and primitive • One voltage level • Two problems: DC component & Lack of synchronization • Polar • Two signal levels: positive & negative • Eliminate DC component • Biploar • Three signal levels: positive, zero, and negative 4. Digital Transmisison - Lin

  8. 4.1 Line Encoding (cont.) • Unipolar Encoding Figure 4.6 Unipolar Encoding, From p. 89, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  9. 4.1 Line Encoding (cont.) • Polar Encoding • NRZ: Non Return to Zero • RZ: Return to Zero • Manchester • Differential Manchester 4. Digital Transmisison - Lin

  10. 4.1 Line Encoding (cont.) • NRZ: Non Return to Zero • NRZ-L • 0 positive; 1 negative • Sync. Problem if long string of 0s or 1s is encountered • NRZ-I • the signal is inverted if a 1 is encountered • A long string of 0s still cause sync. problem Figure 4.8 NRZ-L and NRZ-I Encoding, From p. 91, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  11. 4.1 Line Encoding (cont.) • RZ: Return to Zero • Uses three values: positive, zero, negative • Ensure Sync: a signal change for each bit • Main disadvantage: use more bandwidth Figure 4.9 RZ Encoding, From p. 91, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  12. 4.1 Line Encoding (cont.) • Manchester Encoding • Uses two level signal values: positive, negative • Sync: Inversion at the middle of each bit • Zero: High -> Low; One: Low -> High Figure 4.10 Manchester Encoding, From p. 92, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  13. 4.1 Line Encoding (cont.) • Differential Manchester Encoding • Uses two level signal values: positive, negative • Sync: Inversion at the middle of each bit • Zero: A transition; One: No transition Figure 4.10 Differential Manchester Encoding, From p. 93, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  14. 4.1 Line Encoding (cont.) • Biploar Encoding • Uses three level signal values: positive, zero, negative • 0: Zero level; 1: Alternating positive and negative voltages • AMI: Alternate Mark Inversion • BnZS: Bipolar n-zero Substitution Figure 4.12 Bipolar AMI Encoding, From p. 94, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  15. 4.2 Block Encoding • Improve performance • Ensure synchronization through redundancy bits • Block Encoding Schemes • 4B/5B: 4-bit data encoded into 5-bit code • 8B/10B: 8-bit data encoded into 10-bit code • 8b/6T: 8-bit data encoded into 6-symbol code 4. Digital Transmisison - Lin

  16. 4.2 Block Encoding (cont.) • Block Encoding Figure 4.15 Block Encoding, From p. 95, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  17. 4.2 Block Encoding (cont.) • 4B/5B Block Substitution • Better Sync & Error detection • 16 groups -> 32 groups • No more than 3 consecutive 0s Figure 4.16 Substitution in Block Encoding, From p. 95, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  18. 4.2 Block Encoding (cont.) • 4B/5B Encoding Table Table 4.1 4B/5B Encoding, From p. 97, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  19. 4.2 Block Encoding (cont.) • 4B/5B Encoding Table Table 4.1 4B/5B Encoding, From p. 97, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  20. 4.2 Block Encoding (cont.) • 8B/6T Encoding • 28: 256 possibilities • 36: 729 six-symbol ternary signal Figure 4.17 Example of 8B/6T Encoding, From p. 98, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  21. 4.3 Sampling • Pulse Amplitude Modulation (PAM) • Sample & Hold circuit • Pulse Code Modulation (PCM) • Quantized PAM • Sampling Rate • Nyquist theorem • How many bit per sample 4. Digital Transmisison - Lin

  22. 4.3 Sampling (cont.) • PAM Figure 4.18 PAM, From p. 99, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  23. 4.3 Sampling (cont.) • Quantized PAM Signal Figure 4.19 Quantized PAM Signal, From p. 100, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  24. 4.3 Sampling (cont.) • Quantization, sign & magnitude Figure 4.20 Quantizing by using sign and magnitude, From p. 100, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  25. 4.3 Sampling (cont.) • PCM Figure 4.21 PCM, From p. 101, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  26. 4.3 Sampling (cont.) • PCM Figure 4.22 From analog signal to PCM digital code, From p. 101, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  27. = x Hz = 2 x samples 4.3 Sampling (cont.) • Nyquist Theorem • Sampling rate must be at least 2 times the highest frequency = ½ x Figure 4.23 Nyquist Theorem, From p. 102, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  28. 4.3 Sampling (cont.) • Examples • Q1: What sampling rate is needed for a signal with a bandwidth of 10 KHz (1KHz to 11KHz) • A1: Sampling rate = 2 x 11 KHz = 22,000 samples per second 4. Digital Transmisison - Lin

  29. 4.3 Sampling (cont.) • Examples • Q2: A signal is sampled. Each sample requires at least 12 levels of precision (+0 to +5 and 0 to -5). How many bits should be sent for each sample? • A2: 4-bit • 1-bit for sign • 3-bit for magnitude (8-levels) 4. Digital Transmisison - Lin

  30. 4.3 Sampling (cont.) • Examples • Q3: We want to digitize the human voice. What is the bit rate, assuming 8-bits per sample? • A3: BW of Human voice 0-4000 Hz • Sampling rate 4000 x 2 = 8000 samples/sec • Bit rate • 8000 sample/sec x 8 bit/sample = 64,000 bps 4. Digital Transmisison - Lin

  31. 4.4 Transmission Mode • Parallel • Serial • Synchronous • Asynchronous Figure 4.25 Parallel transmission, From p. 104, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  32. 4.4 Transmission Mode • Serial Transmission Figure 4.26 Serial transmission, From p. 105, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  33. 4.4 Transmission Mode • Serial - Asynchronous Figure 4.27Asynchronlus transmission, From p. 106, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  34. 4.4 Transmission Mode • Serial - Synchronous Figure 4.28 Synchronlus transmission, From p. 107, Data Communications and Networking, Forouzan, McGrawHill 4. Digital Transmisison - Lin

  35. Summary Questions? 4. Digital Transmisison - Lin

More Related