Re: [Discuss-gnuradio] header_payload_demux

[Marcus Müller]

> The second question is:I see the fft block,it has one option:shift,and
you set yes.
The FFT block is able to shift the left half of your vector to the end.
It's basically identical to the fftshift function in Matlab: With shift,
f=0 is the middle bin (and not the first one) .

> And now I want to save the data to file and analyse the data by matlab.
> In the transmit maybe ifft(fftshift(symbol))

ifft(Ifftshift()), iff you want to have the pre-fft data.

> but in the receive what command?
What receiver?
You don't really tell us how and under what aspect you want to analyze the 
data; this seems to more of an communications engineering/design question, than 
GNU Radio-related?

> I see maybe you don't use the pilot in the receive part. Am I right?

Sorry, I did not understand. Receive part of what? So long, we have only been 
talking about header_payload_demux, which does exactly that: demuxing packet 
header and payload.

I think that generally you are on a good way of analyzing what the individual 
blocks do!
I think it would be easier for us to understand you, if you asked only one or 
two questions in the same mail and explained more exactly what you are 
considering.

Greetings,
Marcus

On 30.05.2014 03:28, xianda wrote:
> Hi<br/>     Thanks for your kindly reply.<br/>     1.The second question is:I 
> see the fft block,it has one option:shift,and you set yes.<br/>     And in 
> the transmit part,we should do the ifft.And in the receive part,we should do 
> the fft.<br/>     They all set the shift:yes.<br/>     And now I want to save 
> the data to file and analyse the data by matlab.<br/>     In the transmit 
> maybe ifft(fftshift(symbol)),but in the receive what command?<br/>     2.I 
> see maybe you don't use the pilot in the receive part.Am I right?<br/>     
> 3.I see maybe the cyclic prefix is dropped in the header_payload_demux 
> block.Am I right?<br/>     Thank you.Can you explain it?Thank you.<br/>Best 
> regards
> At 2014-05-30 05:05:54, "Martin Braun" <address@hidden> wrote:
>> On 05/29/2014 08:07 PM, xianda wrote:
>>> Hi:
>>>       Thank you in advance.
>>>       I have two simple question:
>>>      1.In the grc,i see a block: header_payload_demux  
>>>       It has 3 input:in,trigger,header_data.But i see
>>> the header_payload_demux_impl.cc:iosignature::make2(1,2,..,..).But it
>>> has 3 input,why?
>> Why 3 inputs or how come only 2 are in the io signature?
>> header_data is a message port, I guess that's what you're after.
>>
>>>      Thank you.
>>>      2.fft:I see the shift:yes.
>>>       I want to save the symbol to file sink and analyse by matlab.But
>>> now i don't know it's shift earlier or fft earlier?
>> Can you rephrase that question?
>>
>> M
>>
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