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Spread Spectrum (DSSS) vs PSK with AWGN

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hippofear

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dpsk spread-spectrum

The PSD of AWGN is N0/2 (Watts/Hz). In general, the wider your signal (in freq domain), the more total noise in the bandwidth of your signal?

So I would like to compare DSSS (modulate using PSK) vs narrow band PSK considering their signal energies are the same. DSSS has a wider spectrum so will it have a higher BER than narrow band PSK due to the greater amount of total noise in the BW?
 

dsss awgn

spread spectrum is not useful if there is no multipath, or intereference from other users. What you say is correct, you gather lot more noise, but SS helps mitigate interference and multipath. If they are not there, there is no need to use SS
-b
 
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    adane

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energy of dsss bpsk

The de-spread process accumulates the signal coherently and the noise is noncohrently accumulated. Therefore, there is about N (spreading factor) times gains.
 

Hi
Spread Spectrum (not CDMA) is important for secure communication, but not actually for mitigating interference and multipath.
After despreading, the signal energy is Inegrated.
 

That SS is for secure comm is the traditional concept, and is also the reason for its creation. However, it is commercialised now. CDMA is not for secure comm, but for bandwidth sharing. you coud say "security" is now replaced with "multi-user capability"

SS helps in multipath situations because you dont resemble not even your own delayed versions.
And if you want to share your BW with other users, SS is the way.
-b
 

Hi
You are right bulx, and this is a reason for different names for Spread Spectrum systems and CDMA.
 

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