Re: [Discuss-gnuradio] ofdm parameters

I plot the signal before the tx and after the rx on same graph to compare between them while increasing noise to know how much noise can affect it for different types of channel & frequency offset . But when I set noise to zero , I find that the 2 signals are not the same ! why ?! They may be the same but they are not synchronized . How to solve this problem ?

(Attached the loopback.grc & the graph)

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Second , There is a variable called sync word , I know that it is for synchronization using schmidl and cox algorithm & I know that is takes fft length & occupied carriers & pilot carriers
as it is written in "ofdm_rxrx.py
"if sync_word1 is None:
self.sync_word1 = _make_sync_word1(fft_len, occupied_carriers, pilot_carriers)"

But why I get an error syaying that " sync words must be fft length" when I write in sync word 1 & sync word 2 fields in the tx & rx block : (128, (range(-61,-42)+range(-41, -14) + range(-13, -7) + range(-6, 0) + range(1, 7) + range(7, 14) + range(15, 42)+range(43,62),) , ((-42, -14, 14, 42,),) ) ?
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Third , I tried my parameters in loopback example & I got no error , but I want to try tx_ofdm.grc with my parameters & put file sink after each block to understand , but I got an error in tx_ofdm.grc . Why I got an error while the same parameters don't give an error in loopback ?!!

Only I changed these parameters to be mine in tx & rx :

fft len=128 , CP =fft_len/8=16 , packet length=87

occupied carriers = (range(-61,-42)+range(-41, -14) + range(-13, -7) + range(-6, 0) + range(1, 7) + range(7, 14) + range(15, 42)+range(43,62),)
pilot carriers : ((-42, -14, 14, 42,),)
pilot symbols : (((-1+1j),(1-1j),(-1+1j),(-1-1j),),)

sync_word1=None , sync_word2=None

Here is the full output when executing :
Using Volk machine: sse4_2_64_orc
Traceback (most recent call last):
File "/home/sara/trials/tx_ofdm.py", line 241, in <module>
    tb = tx_ofdm()
File "/home/sara/trials/tx_ofdm.py", line 100, in __init__
    self.digital_ofdm_carrier_allocator_cvc_0 = digital.ofdm_carrier_allocator_cvc(fft_len, occupied_carriers, pilot_carriers, pilot_symbols, (sync_word1, sync_word2), length_tag_key)
File "/usr/local/lib/python2.7/dist-packages/gnuradio/digital/digital_swig.py", line 4312, in make
    return _digital_swig.ofdm_carrier_allocator_cvc_make(*args, **kwargs)
TypeError: in method 'ofdm_carrier_allocator_cvc_make', argument 5 of type 'std::vector< std::vector< gr_complex,std::allocator< gr_complex > >,std::allocator< std::vector< gr_complex,std::allocator< gr_complex > > > > const &'

Thanks is advance

2014-06-22 18:30 GMT+03:00 Marcus Müller <address@hidden>:

Hi Sara,
when looking into the "Instrumentation" Category in the Companion, you
will notice two subcategories with several different visualization types.
On many of these, you can set a number of input ports.

Greetings,
Marcus

On 22.06.2014 17:10, Sara Chérif wrote:
> Thanks Marcus .
> I want to append 2 plots on same graph ( the transmitted signal and the
> received signal ) . I connected WX GUI scope sink to the ofdm tx and
> another one to the ofdm rx . I put CFO model & channel model between the tx
> & rx . I want to compare between the signals while changing offset and
> noise. How can I append them on same graph ? & Is there any other method to
> plot in GNU Radio ?
>
> Thanks in advance .
>
>
> 2014-06-21 17:29 GMT+03:00 Marcus Müller <address@hidden>:
>
>> Hello Sara,
>>
>> It's hard to tell without you offering us the actual line where you call
>> make, but from looking at your symbols variable I'd say you have a tuple
>> containing a tuple of tuples of floats,
>> and what you need would be a
>> tuple of tuples containing complexes.
>>
>> Note that (1,1j) is *not* a complex, but 1+1j is.
>>
>> Greetings,
>> Marcus
>>
>> On 21.06.2014 16:00, Sara Chérif wrote:
>>> Hello ,
>>>
>>> I want to implement ofdm system with these parameters:
>>>
>>> FFT length=128
>>>
>>> Occupied subcarriers=117.
>>>
>>> 4 pilots
>>>
>>> 1 DC
>>>
>>> 6 zeros subcarriers .
>>>
>>> I put these parameters in ofdm tx & ofdm Rx:
>>>
>>> Occupied carriers =(range(-58,-42)+range(-41, -14) + range(-13, -7) +
>>> range(-6, 0) + range(1, 7) + range(7, 14) + range(15, 42)+range(43,60),)
>>>
>>> pilots carriers=((-42, -14, 14, 42,),)
>>>
>>> pilot symbols =(((-1,1j),(1,-1j),(-1,1j),(-1j,1),),)
>>>
>>>
>>> But I got this error , I don't understand what is wrong
>>>
>>>
>>> File
>>>
>> "/usr/local/lib/python2.7/dist-packages/gnuradio/digital/digital_swig.py",
>>> line 4635, in make
>>> return _digital_swig.ofdm_equalizer_simpledfe_make(*args, **kwargs)
>>> TypeError: in method 'ofdm_equalizer_simpledfe_make', argument 5 of type
>>> 'std::vector< std::vector< gr_complex,std::allocator< gr_complex >
>>>> ,std::allocator< std::vector< gr_complex,std::allocator< gr_complex > >
>>>> const &'
>>> Thanks.
>>>
>>>
>>>
>>> _______________________________________________
>>> Discuss-gnuradio mailing list
>>> address@hidden
>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>>
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>>

From:	Sara Chérif
Subject:	Re: [Discuss-gnuradio] ofdm parameters
Date:	Mon, 23 Jun 2014 19:31:29 +0300