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

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:

Sean

Discuss-gnuradio mailing list

[email protected]

Discuss-gnuradio Info Page

–

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.

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.