Hi Antonio, > Could you tell me how can I solve the problem with the offset between > the DPSK mod and demod? Use a BER analysator with some kind of large window. In effect, I'd just write the raw send symbol stream to a file, do the same with the receive symbol stream, and calculate the error offline, if I hadn't had packets.
> Likewise, as you say, I am using a packet-based transmission. That makes BER a bit of a "secondary issue", doesn't it? Packets have checksums, and for all packets that contain bit errors, there's (hopefully) a high probability the checksum will be wrong, and the whole packet needs to be considered lost. Also, assuming symbol errors are equally likely for all symbols in a packet, you should be able to derive a PDF for the number of wrong bits per wrong packet, based on AWGN – yeah, it's that stuff from digital comm basics :) Anyway, having packets makes the whole measuring a lot easier; you'll need to write a block that buffers both the send packets and the receive packets. I don't know your packet format, but it possibly has a packet number. Use that packet number to delete received packets from the send packet buffer. If a packet is broken, reconstruct its number from the next/previous successfully received packet. Note down the correct received packets as successfull bits, and count the missing and broken packets. Best regards, Marcus On 17.07.2016 21:33, ANTONIO TAMAYO wrote: > Hello Martin, > > Thank you for your response. > Could you tell me how can I solve the problem with the offset between > the DPSK mod and demod? > In the same way, how can I garantee that I am comparing the correct > bits? Using another block? > Likewise, as you say, I am using a packet-based transmission. For this > reason I need to perform more sophisticated comparisons to calculate > the BER, what do you recommend me to calculate BER? > > Thank you all, > > Antonio > > On 06/13/2016 09:46 AM, MARTIN BRAUN wrote: > >Antonio, > > > >I'm not sure why it's telling you 'no BER', but your setup is not > >suitable to test BER anyway. Your DPSK demod will always be offset w.r.t > >the DPSK mod input (because of sync delays etc.). > > > >Such BER measurements only work well if you can guarantee you're > >comparing the right bits. > > > >Since you're doing packet-based transmission, you'll need to come up > >with something more sophisticated comparison. > > > >Cheers, > >Martin > > > >On 06/12/2016 12:22 PM, ANTONIO TAMAYO wrote: > >> Hello all, > >> > >> I'm trying to calculate de BER value of the comunications system of the > >> image attached. I'm using a DQPSK modulator and demodulator. I think > >> that I have made mistakes in the configuration of my sistem because the > >> BER value always is "none", but I can't solve them. Somebody could help me? > >> > >> Regards, > >> > >> Antonio. > >> > >> > >> _______________________________________________ > >> Discuss-gnuradio mailing list > >> Discuss-gnuradio@gnu.org <mailto:Discuss-gnuradio@gnu.org> > >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >> > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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