Re: [Discuss-gnuradio] correlator in gnuradio

[Nemanja Savic]

Well, I was studying correlator, and it's pretty straight forward approach. If you specify threshold of k bits, then it will output 0x3 every time it finds pattern that differs from given preamble at max. k bits. Maybe you can provide some more information. In my designs I usually use threshold 0.

Best

Nemanja

On Wed, Jun 19, 2013 at 10:21 PM, yeran <address@hidden> wrote:

Hi everyone,

I'm trying to learning the algorithm of the correlator in generic_mod_demod.py. Then use the similar algorithm in my own block.

In the file digital_correlate_access_code_bb.cc, according to my understanding, the original algorithm is compare each bit of the 8-Byte access code with the default 8-Byte access code. If the wrong bits is less than 12 bits (the threshold), then it is decided as "access code found".

I wrote a file to detect access code, too. I compared each of the 8-Byte with the default access code. If the correct bits is more than (64bits - 12 bits), then it is decided to be found.

But when I us my program, when decoding the same data, I can always found more than the original method. For instance, when I use benchmark's original method, I can get n_rcvd=570 pkt, which means in the generic_mod_demod correlator, 570 access code are found. But my program found 577.

Has anybody been study the correlator block before? and see if there is a misunderstanding in my work?

Thanks in advance!

Ada

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Nemanja Savić