FPGA Central

hi,

I'm designing a CDMA-DSSS transceiver.

At the receiver, the matched filter (MF) have peak at the output, so I
have to compare it to a threshold...

How to compute the value of this threshold ?

Thanks...

patrick.melet@dmradiocom.fr (Patrick) wrote in message news:<54b3002.0408170129.75cdfbce@posting.google.c om>...
> hi,
>
> I'm designing a CDMA-DSSS transceiver.
>
> At the receiver, the matched filter (MF) have peak at the output, so I
> have to compare it to a threshold...
>
> How to compute the value of this threshold ?
>
> Thanks...

The threshold value is normally determined by your noise PDF and by
selecting some acceptable "Probability of False Alarm". Most of the
analytical theory here is based around Gaussian noise models.

Cheers,
David

> The threshold value is normally determined by your noise PDF and by
> selecting some acceptable "Probability of False Alarm". Most of the
> analytical theory here is based around Gaussian noise models.
>
> Cheers,
> David

Hello David,

How can I compute the PDF of the noise ?

I've tried this to integrate the output of the matched filter and
compute the maximal value

Then how to compute the PDF value of the noise ?

Thanks.

"Patrick" <patrick.melet@dmradiocom.fr> wrote in message
news:54b3002.0408180758.68f1399b@posting.google.co m...
> > The threshold value is normally determined by your noise PDF and by
> > selecting some acceptable "Probability of False Alarm". Most of the
> > analytical theory here is based around Gaussian noise models.
> >
> > Cheers,
> > David
>
> Hello David,
>
> How can I compute the PDF of the noise ?
>
> I've tried this to integrate the output of the matched filter and
> compute the maximal value
>
> Then how to compute the PDF value of the noise ?

Look at the output of the filter with noise and no signal?
Set the threshold so that the false alarm rate is acceptable?
(Because even after you have the PDF, you have to select a point on the PDF
that's acceptable for your application).
To what extent does the noise level vary > suggesting a variable threshold?

Fred