Re: [Discuss-gnuradio] Problem with OFDM Mod block

[frankist]

Thanks for the response. I am using the GRC and I let the preamble size=0.
When I use a lower number of occupied tones this error doesn't occur.
However if I used the values specified in the first post that message
appears



Michael Dickens-3 wrote:
> 
> Hi Francisco - The code in question is, as the error says, at line 106 of
> the Python file "ofdm.py":
> 
> self.preambles = digital_swig.ofdm_insert_preamble(self._fft_length,
>                                                    padded_preambles)
> 
> This code calls the C++ code found in the file
> digital_ofdm_insert_preamble.cc, which throws an error when any valid
> preamble's length is not equal to the FFT size.  This throwing has nothing
> to do with the cyclic prefix length or # occupied tones.  You should be
> able set no preambles, according to the code, by sending in a zero-length
> vector (I think).  The preamble must be a vector of vectors, with the
> first dimension being the number of preambles and the second dimension
> must be the FFT length.  Check out which preamble you're using would be my
> recommended next step.  Good luck. - MLD
> 
> On Jul 11, 2012, at 2:54 PM, frankist wrote:
>> I was trying to use the OFDM Mod block to create a OFDM signal with FFT
>> size=8192, occupied tones=6818 and CP=2048
>> 
>> However I keep getting this error:
>> 
>> File "/usr/local/lib/python2.7/dist-packages/gnuradio/digital/ofdm.py",
>> line 106, in __init__
>>    padded_preambles)
>>  File
>> "/usr/local/lib/python2.7/dist-packages/gnuradio/digital/digital_swig.py",
>> line 4517, in ofdm_insert_preamble
>>    return _digital_swig.ofdm_insert_preamble(*args, **kwargs)
>> RuntimeError: digital_ofdm_insert_preamble: invalid length for preamble
>> symbol
>> 
>> If I use a lower number of occupied tones this error disappears but I was
>> interested in this number because it is close to the DVB-T 8k mode.
>> 
>> Can you explain me what am I doing wrong or if there is a workaround for
>> this problem
> 
> 
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> 

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