Hi Abhinav,
I must admit that I completely lost track of this; could you maybe
really do a sketch of what your trying to transmit something like:
x = 0-filling sample
1 = data 1
0 = data 0
xx1xx0xx0xx0xx1
or so?
Best regards,
Marcus
On 10.11.2015 07:18, abhinav narain wrote:
> Hi Marcus, others,
>
> If I understand you correctly, however, you *actually* want to do
> BPSK, and the 0 symbol is just a "filler" in between symbols,
> right? That might actually work, if you just increase the rolloff
> duration/samples per symbol of your pulse shaping filter.
>
> I think my system sort of works, with just one problem :
> Lets say I transmit two 1s with 50 0 apart (correspondingly 0 IQ
> values given to ADC) in my transmission file. I see random number 0s
> decoded at the receiver(which means there can be any number of them)
> between the two 1s. This is a problem as I cannot decode my symbols.
>
> Is this a problem with clock drift and cannot be fixed with gnuradio ?
> Do you recommend any other way to deal with it ?
>
> Thanks,
> Abhinav
>
>
> Best regards,
> Marcus
>
>
> On 10/12/2015 06:00 PM, abhinav narain wrote:
>> Hi,
>> I am trying to transmit -1,0,1 { [1]+ 100*[0]+[-1] }, basically
>> BPSK lot of 0s filled in between at certain frequency. I have
>> few questions. "Constellation object" has 3 symbols
>> ([1+0j,-1+0j,0+0j]) mapped to symbol map-> [0,1,2] respectively.
>> I agree that constellation with size 3 is weird but that is what
>> I want. I want the decision boundaries to be at -0.5, 0.5 for
>> bits and anything between that to be given symbol=2 which i can
>> discard later on. I am currently doing this in baseband, but I
>> will eventually trasmit at a some frequency X.
>>
>> I have the following baseband setup grc
>> (http://postimg.org/image/8k7g1o375/ , grc file is attached).
>> I have few problems which I am unable to fix since yesterday -
>> 1) The constellation after channel is stable (as expected) but
>> it goes weird
>> after the polyphase clock sync and costas loop (
>> http://postimg.org/image/pyg8h2vlh/ , attached image-
>> constellation_before_after_costas.png) and hence I don't get the
>> expected output of equally spaced 1, 0 in the decoder output (
>> http://postimg.org/image/a58cc35cj/ , attached image-
>> custom_decoder_0_1_2_output.png)
>>
>> 2) If I set the order of costas loop as 3 (size of
>> constellation) my flowgraph doesn't work at all. I have used the
>> parameters after reading some example code
>> in gnuradio folders and web and i guess they are correct. Please
>> correct me if I am wrong.
>>
>> Thanks,
>> Abhinav
>>
>>
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