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Re: [Discuss-gnuradio] QPSK with direct-sequence spread spectrum

From: Peter Massam
Subject: Re: [Discuss-gnuradio] QPSK with direct-sequence spread spectrum
Date: Mon, 31 Oct 2011 10:59:06 -0700 (PDT)

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
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> Discuss-gnuradio mailing list
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