Ok.
The block diagram in most of the textbook says the modulated signal is
multiplied with the PN sequence.
1. If I decide to do the same then my setup will look like this
byte -> bytes_to_chunks -> chunks_to_symbols(BPSK) -> rrc_filter(X
samples per bit) -> DSSS
I am confused about the DSSS part. I am using a 63-bit PN sequence and
spreading the BPSK symbols with this sequence means I have to pass each of
the BPSK symbol through an interpolation filter with PN sequence as the
taps(like in the barker example). Am I right? If this is not how it is done
then can someone please suggest me a way.
Thanks,
John
On Thu, Apr 29, 2010 at 8:11 AM, Martin DvH <gnuradiom...@olifantasia.com>wrote:
> On Wed, 2010-04-28 at 11:23 -0700, Johnathan Corgan wrote:
> > On Tue, Apr 27, 2010 at 21:19, John Andrews <gnu.f...@gmail.com> wrote:
> >
> > > If I want to transmit a signal which is DSSS spread using BPSK. Is it
> > > correct for me to first digitally spread the incoming data bits and
> then
> > > apply BPSK before sending it to the USRP or should I first convert the
> > > signal to BPSK and then multiply the output of the BPSK modulator with
> the
> > > PN sequence although I don't know how to do it.
> >
> > Technically, these are equivalent. However, it is easier and uses
> > less CPU to XOR your data sequence with your PN code, then send it to
> > the modulator.
> I think there is a difference, if you use a root raised cosine filter,
> set for your datarate and roll-off factor.
>
> I think the correct version should then be:
> BPSKmod -> RRCfilter -> DSSS
>
> Martin
> >
> > Johnathan
> >
> >
> > _______________________________________________
> > Discuss-gnuradio mailing list
> > Discuss-gnuradio@gnu.org
> > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> >
>
>
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