Spread Spectrum
CEN 220/CIS 192 Advanced Data Communications and Networking
Data and Computer Communications, W. Stallings...
2
Spread Spectrum
“All creative people want to do the unexpected.”
—Ecstasy and Me: My Life as a Woman,
Hedy Lamarr
3
Spread Spectrum
4
Pseudorandom Numbers
5
General Model of Spread Spectrum System
6
Spread Spectrum Advantages
Immunity from noise and multipath distortion
Can hide / encrypt signals
Several users can sha...
7
Frequency Hopping Spread Spectrum
(FHSS)
8
Frequency Hopping Example
9
FHSS (Transmitter)
Frequency Hopping Spread Spectrum (FHSS)
10
FHSS (Receiver)
Frequency Hopping Spread Spectrum (FHSS)
11
Slow and Fast FHSS
Commonly use multiple fsk (mfsk)
Have frequency shifted every tc seconds
Duration of signal element ...
12
Slow MFSK FHSS
13
Fast MFSK FHSS
14
Direct Sequence Spread Spectrum (DSSS)
Each bit is represented by multiple bits using a spreading
code
This spreads sig...
15
Direct Sequence Spread Spectrum Example
16
Direct Sequence Spread Spectrum System
17
DSSS Example Using BPSK
18
Approximate
Spectrum of
DSSS Signal
19
Code Division Multiple Access (CDMA)
20
CDMA Example
21
CDMA
Example
22
CDMA for DSSS
23
Summary
Concept of spread spectrum
FHSS

FHSS using MFSK
DSSS

DSSS using BPSK
Code Division Multiple Access

CDMA f...
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Chapter 9 - Spread Spectrum 9e

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Transcript of "Chapter 9 - Spread Spectrum 9e"

  1. 1. Spread Spectrum CEN 220/CIS 192 Advanced Data Communications and Networking Data and Computer Communications, W. Stallings 9/E, Chapter 9
  2. 2. 2 Spread Spectrum “All creative people want to do the unexpected.” —Ecstasy and Me: My Life as a Woman, Hedy Lamarr
  3. 3. 3 Spread Spectrum
  4. 4. 4 Pseudorandom Numbers
  5. 5. 5 General Model of Spread Spectrum System
  6. 6. 6 Spread Spectrum Advantages Immunity from noise and multipath distortion Can hide / encrypt signals Several users can share same higher bandwidth with little interference  CDM/CDMA Mobile telephones
  7. 7. 7 Frequency Hopping Spread Spectrum (FHSS)
  8. 8. 8 Frequency Hopping Example
  9. 9. 9 FHSS (Transmitter) Frequency Hopping Spread Spectrum (FHSS)
  10. 10. 10 FHSS (Receiver) Frequency Hopping Spread Spectrum (FHSS)
  11. 11. 11 Slow and Fast FHSS Commonly use multiple fsk (mfsk) Have frequency shifted every tc seconds Duration of signal element is ts seconds Slow fhss has tc  ts Fast fhss has tc < ts FHSS quite resistant to noise or jamming  with fast FHSS giving better performance
  12. 12. 12 Slow MFSK FHSS
  13. 13. 13 Fast MFSK FHSS
  14. 14. 14 Direct Sequence Spread Spectrum (DSSS) Each bit is represented by multiple bits using a spreading code This spreads signal across a wider frequency band Has performance similar to FHSS
  15. 15. 15 Direct Sequence Spread Spectrum Example
  16. 16. 16 Direct Sequence Spread Spectrum System
  17. 17. 17 DSSS Example Using BPSK
  18. 18. 18 Approximate Spectrum of DSSS Signal
  19. 19. 19 Code Division Multiple Access (CDMA)
  20. 20. 20 CDMA Example
  21. 21. 21 CDMA Example
  22. 22. 22 CDMA for DSSS
  23. 23. 23 Summary Concept of spread spectrum FHSS  FHSS using MFSK DSSS  DSSS using BPSK Code Division Multiple Access  CDMA for Direct Sequence Spread Spectrum
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