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Direct-sequence spread spectrum: Difference between revisions

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→Features: There's nothing pseudorandom about e.g. Hadamard sequences. -> strike. Nothing continuous about a string, and it's not a string, but a sequence -> strike, replace.
→Features: DSSS could be a phase modulation, but that's not generally the case -> strike. DSSS doesn't modulate a sine wave, which would hold no information -> strike. DSSS is at symbol, not at bit level. Spreading factors of 2 are commonly used, not "much shorter durations" -> strike. Symbol rate == baud rate != bit rate.
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==Features==
# DSSS [[Phase-shift keying|phase-shifts]]modulates a [[sinesequence of transmit wave]]symbols with a sequence of ''chips'', eachwhose ofduration which hasis a muchfraction shorterof duration thanthe anoriginal informationsymbol [[bit]]period. That is, each information bitsymbol is modulated by a sequence of much faster chips. Therefore, the [[Chip (CDMA)|chip rate]] is much higher than the [[information]] [[Baud|bitsymbol rate]].
# DSSS uses a [[signaling (telecommunication)|signal]] structure in which the spreading sequence produced by the transmitter is already known by the receiver. The receiver can then use the same spreading sequence to counteract its effect on the received signal in order to reconstruct the information signal.
 
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