09-SpreadSpectrum

09-SpreadSpectrum - William Stallings Data and Computer...

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William Stallings Data and Computer Communications 8 th Edition Chapter 9 Spread Spectrum
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Spread Spectrum Analog or digital data Analog signal Spread data over wide bandwidth Makes jamming and interception harder Frequency hoping Signal broadcast over seemingly random series of frequencies Direct Sequence Each bit is represented by multiple bits in transmitted signal Chipping code
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Spread Spectrum Concept Input fed into channel encoder Produces narrow bandwidth analog signal around central  frequency Signal modulated using sequence of digits  Spreading code/sequence Typically generated by pseudonoise/pseudorandom number  generator Increases bandwidth significantly Spreads spectrum Receiver uses same sequence to demodulate signal Demodulated signal fed into channel decoder
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General Model of Spread Spectrum System
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Gains Immunity from various noise and multipath  distortion Including jamming Can hide/encrypt signals Only receiver who knows spreading code can retrieve  signal Several users can share same higher bandwidth 
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09-SpreadSpectrum - William Stallings Data and Computer...

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