Re: [Discuss-gnuradio] Difference between blks and blks2

[Colby Boyer]

I agree with you doug.  After reading through the BBN code, that seems like why they did that.  DBPSK and DQPSK appear to be backward compatible decoding wise.

I think the reason why you cannot transmit/decode DQPSK packets is that the entire packet is encoded as DQPSK and not part DBPSK and part DQPSK.  The decoding algorithm then fails.

--Thanks

On Tue, May 12, 2009 at 7:37 AM, Doug Geiger <address@hidden> wrote:

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Colby Boyer wrote:
> Hi all,
>
> So I am not too familiar with the history of how GNU-Radio has evolved
> over the past few years and I am wondering what are the fundamental
> differences between blks and blks2(old revisions vs new revisions)?
>
> A question I am asking is why did the BBN people who wrote the 802.11b
> code make their own DPSK mod/demod and did not use the function blocks
> provided by gnuradio?  Were those blocks simply not available at the time?
>
> Last question.  Has the functionality of teh the DB/QPSK modulations in
> the blks2 library been tested? I'm in the process of cleaning up the
> 802.11b code, and if I can relay on gnu-radio libraries, rather than
> custom C++/python code, that would be better.
>
> Thanks,
> Colby

 For the 802.11b code, I think part of the reasoning was that for
providing 1 and 2Mbps service, the block needed to be able to switch
rapidly between DBPSK and DQPSK (and the block would not know until the
preamble was decoded), so they did both in parallel, and simply switched
which output was actually used as needed. If any of the BBN folks are
still on-list they may have more insight.
 Doug

- --
Doug Geiger
Research Assistant
Communications and Signal Processing Lab
Oklahoma State University
address@hidden
address@hidden
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