09-SpreadSpectrum

Tests of randomness tests starting from an initial

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Unformatted text preview: mness tests starting from an initial seed need to know algorithm and seed to need predict sequence predict hence only receiver can decode signal Frequency Hopping Spread Spectrum (FHSS) Spectrum signal is broadcast over seemingly signal random series of frequencies random receiver hops between frequencies in receiver sync with transmitter sync eavesdroppers hear unintelligible blips jamming on one frequency affects only a jamming few bits few Frequency Hopping Example Frequency FHSS (Transmitter) FHSS Frequency Hopping Spread Spectrum System (Receiver) Spectrum Slow and Fast FHSS Slow commonly use multiple FSK (MFSK) have frequency shifted every Tc duration of signal element is Ts Slow FHSS has Tc Fast FHSS has Tc seconds seconds ≥ Ts < Ts FHSS quite resistant to noise or jamming with fast FHSS giving better performance Slow MFSK FHSS Slow Fast MFSK FHSS Fast Direct Sequence Spread Spectrum (DSSS) Spectrum each bit is represented by multiple bits each using a spreading co...
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