| Author |
Message |
pixel
Joined: 16 Sep 2004
Posts: 569
Helped: 59
|
 28 Sep 2004 19:43 hybrid Spread Spectrum techniques? |
|
|
|
| What are advantagesa, and disadvantages using hybrid DS-FH (direct sequence-Freq.Hopping) spread spectrum, than simple DS, or FH?
|
|
| Back to top |
|
 |
djalli
Joined: 10 Nov 2001
Posts: 887
Helped: 15
Location: 1600 Pennsylvania Avenue, Washington DC 20500
|
| 29 Sep 2004 5:55 hybrid Spread Spectrum techniques? |
|
|
|
The whole thing of Spread Spectrum is a) to withstand the jamming from another source b) information hiding techniques.
Spread Spectrum is inherently jamming resistant. More chips you enter to spreading the better is it to withstand the jamming.
The hybrid version of DS/FH is mainly (or at least started that way) is for information hiding techniques.
Normally Direct Sequence or Frequency Hopping techniques in specifics of them employ a lot of bandwidth/power wasted and Hybrid DS/FH is desiged to be somewhat also a bridge/gap where you can play better. It just gives you options. I think this would be an advantage I think.
|
|
| Back to top |
|
|
pixel
Joined: 16 Sep 2004
Posts: 569
Helped: 59
|
| 29 Sep 2004 9:56 Re: hybrid Spread Spectrum techniques? |
|
|
|
| Hybrid process gain is Gfh*Gds, and is higher than single DS, and FH techniques, which is good. But, there has to be some disadvantages?
|
|
| Back to top |
|
|
sourour
Joined: 07 Oct 2004
Posts: 38
Helped: 3
|
| 17 Oct 2004 23:04 Re: hybrid Spread Spectrum techniques? |
|
|
|
If the total available bandwidth is too large it is not feasible to use DS alone, since the chip rate will be very high, which may require very high speed circuits and very wide band receivers. In this case we can benefit from the available bandwith by using hybrid DS/FH.
Pure FH typically requires non-coherent modultion technique, like FSK. The performance of such systems is less than the coherent modulation techniques.
Therefore, if the bandwidth is very large and we want a coherent modulation/demodulation technique, a hybrid DS/FH is a good choice.
|
|
| Back to top |
|
|
