I second Peter. As long as you make sure in your gray-coded QPSK constellation, 0 is mapped to +1 and 1 is mapped to -1 then XOR is equivalent to multiplication.
On Mon, Oct 31, 2011 at 1:59 PM, Peter Massam <peter.mas...@plextek.com>wrote: > > In general you're right, but it depends on the details. Its usually quite > straightforward, but a common mistake is to use the wrong bit-to-symbol > mapping. 0 -> +1 and 1 -> -1 means that an XOR applied to bits is > equivalent to multiplication applied to symbols. > > > Nowlan, Sean wrote: > > > > Hi all, > > > > I'm wondering if spreading a bitstream (XOR-ing each bit with > > SPREAD_FACTOR bits of sequence) before QPSK modulation is equivalent to > > operating on the modulated stream, i.e., multiplying the complex output > > with -1's and 1's from the sequence. So far I can't get the math to work > > out. Any suggestions? > > > > Thanks, > > Sean > > > > _______________________________________________ > > Discuss-gnuradio mailing list > > Discuss-gnuradio@gnu.org > > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > > > -- > View this message in context: > http://old.nabble.com/QPSK-with-direct-sequence-spread-spectrum-tp32752034p32754111.html > Sent from the GnuRadio mailing list archive at Nabble.com. > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >
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