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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