Re: [Discuss-gnuradio] Spread Spectrum question in gnuradio

[George Nychis]

this would be similar to 802.11b's PHY at 1Mbps, except it uses the barker sequence as opposed to the sequence you mention.  It spreads a BPSK signal using the barker sequence.  

You can take a look at the BBN 802.11b code in CGRAN to see how they implement this:
https://www.cgran.org/browser/projects/bbn_80211/branches/usrp2_version/gr-bbn/src/examples/bbn_80211b_pkt.py#L126

It modulates to BPSK, and then spreads it out via the interpolation filter.

- George

On Wed, Apr 28, 2010 at 12:19 AM, John Andrews <address@hidden> wrote:

Hi,

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.

1. If '1' is the data bit then convert it to '1010100111' (lets say this is the PN sequence) and then input it into a BPSK modulator.

2. If '1' is the data bit first input it into a BPSK modulator and then mutiply the interpolated output with the PN sequence.

Theoretically, these two methods will lead to the same result but I am not sure how to do this in gnuradio. 

Any ideas?

Thanks

John

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