I i try that DQPSK schema myself, but i notice that in your image you have Bits per symbol in packet encoder set to 4, but the help of packet encoder says 2 for DQPSK.
I try 2, and i get no errors until the end, probably because of file buffering. --- sent.hex 2013-12-14 10:11:41.308775941 -0800 +++ got.hex 2013-12-14 10:11:52.269776677 -0800 @@ -62206,259 +62206,3 @@ 00f2fd0: 4db3 ace4 e63f eb53 3fb3 e20a 6cdf 85ab M....?.S?...l... 00f2fe0: 1a29 0ae6 3816 2e64 bd37 dc08 6982 379b .)..8..d.7..i.7. 00f2ff0: fd0d 6dc5 0d68 53e9 0384 8234 3af2 9861 ..m..hS....4:..a -00f3000: 1625 7ce9 c0aa 64e6 9272 6ce2 9dce d524 .%|...d..rl....$ -00f3010: 1d0f 748e bcfb 88a8 f9ee 3504 1dd4 7204 ..t.......5...r. bytes_sent file has 999424 bytes and bytes_received has 995328 bytes. The difference is probably that 1 million samples from random source isnt even to the payload length of packet encoder. On Sun, Dec 8, 2013 at 8:57 PM, Henry Jin <henry.ji...@gmail.com> wrote: > Hi all, > > As per previous discussions, I have changed my design as shown in the link > https://www.dropbox.com/s/8pw27f29qf5unuq/Screenshot%20from%202013-12-08%2021%3A39%3A05.png > > This time, QPSK and BPSK both works as I compared the files generated. > However, I found two more problems: > 1. When Error Rate module is enabled, the simulation can only be run for > one or two seconds, then it gets stuck. This was observed by attaching a > scope in the flowgraph. The display of the scope is never able to be > updated. Just wonder why this happens? > 2. When DPSK Mod and Demod blocks are replaced by QAM Mod and Demod, I > find that many packets are missing in the receiver's decoded file compared > to the file on the sender side. Except the missing packets, all other > packets in the receiver's decoded file can perfectly match with the ones > sent. So what has caused this issue? To make it better understood, I > attached a screenshot comparing the two files from file sinks. > > https://www.dropbox.com/s/9203fvigi3wohmh/Screenshot%20from%202013-12-08%2021%3A52%3A48.png > > Please give me some suggestions if you have any thoughts. Thanks. > Henry > > > On Thu, Dec 5, 2013 at 2:39 PM, Henry Jin <henry.ji...@gmail.com> wrote: > >> Thanks for your effort in trying to help, Michael. I will continue to >> study and if I managed to get it working, I will keep you updated. >> >> Henry >> >> >> On Thu, Dec 5, 2013 at 2:23 PM, Michael Berman <mrberma...@gmail.com>wrote: >> >>> Henry, >>> >>> I looked at this and some of the underlying code, and tried to run your >>> example with some modifications, but all to no avail as to what you are >>> attempting to do. Last time I did anything like this I ended up using the >>> mod_pkts code (found in gr-digital/python/digital/pkt.py). Maybe there is >>> some insight in there that may shed light on what you are trying to do. >>> Sorry I couldn't be of more help. >>> >>> Michael >>> >>> >>> On Wed, Dec 4, 2013 at 1:31 PM, Henry Jin <henry.ji...@gmail.com> wrote: >>> >>>> On Wed, Dec 4, 2013 at 12:13 PM, Michael Berman <mrberma...@gmail.com> >>>> wrote: >>>> >>>>> Looking at your flowchart in the original post, you have an Unpacked >>>>> to Packed block after the demodulator, with bit's per symbol of 1. This >>>>> doesn't seem right to me. I have never tried this with a random source >>>>> like you have it setup, however there should be an Unpacked to Packed >>>>> block >>>>> prior to the modulator and a Packed to Unpacked block after the >>>>> demodulator. These should also have bits per chunck values that >>>>> correspond >>>>> with the bits per symbol of the modulator and demodulator. You need to >>>>> feed in the data in a chunk with the correct amount of bits that >>>>> correspond >>>>> to the bits per symbol of the modulation scheme being used. In the >>>>> example, it looks like you are using QPSK, and therefore the bits per >>>>> chunk >>>>> should be 2 (which is log2(number of constellation points)). The >>>>> modulator >>>>> and demodulator work with chunks of data where each chuck corresponds to a >>>>> symbol. >>>>> >>>> >>>> *If not using the random source, what other sources do you think it's >>>> better? I know GLFSR source also perfectly fits into this scenario. You >>>> also mentioned I have to attach a Unpacked to Packed block prior to the >>>> modulator. But since in my flow, I already set the random source with >>>> maximum being 256. That means it's already outputting packed bytes. Thus, >>>> IMO, Unpacked to Packed block is not needed based on my settings. The >>>> reason I set the Bits per Chunk value as 1 in the Unpacked to Packed block >>>> after demodulation is that I notice in the source code, it says the output >>>> of the demodulation block is unpacked byte with only one LSB being valid. >>>> So In my understanding, it is independent of what modulations (BPSK, QPSK, >>>> etc) I'm using. * >>>> >>>> >>>>> >>>>> For the Samples per Symbol, if I were transmitting over the air, I >>>>> would raise this value to a little bit more than 2, just to ensure the >>>>> receiver can lock onto the changes with given noise before the symbol >>>>> changes again. In this case of looping the modulator strait into the >>>>> demodulator, this should work fine. >>>>> >>>> >>>> *Thanks for the advice, I will take it. * >>>> >>>> >>>>> >>>>> One more thing I would look at would be the Error Rate block source. >>>>> I have never used this block, but in my thinking about it in this >>>>> flowchart, I would source it from the throttle instead of the random >>>>> source. This may help with keeping the data a little more somewhat >>>>> aligned. >>>>> >>>>> >>>> *Yes, this could make things clearer. But maybe it makes no difference. >>>> I remember in one of Tom's tutorial, he said as long as there is one >>>> throttle in the flow, then all the units are throttled.* >>>> >>>>> >>>>> >>>>> Michael >>>>> >>>>> >>>>> On Wed, Dec 4, 2013 at 9:52 AM, Henry Jin <henry.ji...@gmail.com>wrote: >>>>> >>>>>> I tried again replacing the DPSK module with PSK module. Still cannot >>>>>> get the correct data. The parameter for Error Rate "Bits per Symbol" is >>>>>> changed to 8 since every bit carries information in my flow. The sizes of >>>>>> the files from the two file sinks are exactly the same, except with >>>>>> different data. >>>>>> >>>>>> >>>>>> On Tue, Dec 3, 2013 at 10:11 PM, Nick Foster <bistrom...@gmail.com>wrote: >>>>>> >>>>>>> Can you try using the PSK mod/demod blocks with differential=Yes >>>>>>> instead of the DPSK mod/demod blocks? I found an issue today with the >>>>>>> DPSK >>>>>>> mod/demod blocks which results in them not actually using differential >>>>>>> encoding. >>>>>>> >>>>>>> --n >>>>>>> >>>>>>> >>>>>>> On Tue, Dec 3, 2013 at 9:00 PM, Henry Jin <henry.ji...@gmail.com>wrote: >>>>>>> >>>>>>>> Hi, >>>>>>>> >>>>>>>> I tried to build a simple flow graph of DPSK modulation and >>>>>>>> demodulation. The result is verified using the Error Rate module. The >>>>>>>> link >>>>>>>> shows the flow I'm using. >>>>>>>> >>>>>>>> >>>>>>>> https://www.dropbox.com/s/jwmmttyi4es4alf/Screenshot%20from%202013-12-03%2021%3A50%3A58.png >>>>>>>> >>>>>>>> I know that the output of demod module is unpacked bytes, so an >>>>>>>> "unpacked to packed" module is attached after demodulation. However, >>>>>>>> the >>>>>>>> BER is close to 50%, which surely indicates something wrong. I further >>>>>>>> analyzed the two inputs of the Error Rate module by writing info to the >>>>>>>> file sink. It clearly shows the discrepancy. So I just wonder what is >>>>>>>> wrong >>>>>>>> with this flow graph. Could someone please help me? >>>>>>>> >>>>>>>> Also, as I noticed, in the output file generated after "unpacked to >>>>>>>> packed" module, there are many consecutive 0s at the start of the file. >>>>>>>> Does that indicate something? >>>>>>>> >>>>>>>> Suggestions are greatly appreciated! >>>>>>>> >>>>>>>> Henry >>>>>>>> >>>>>>>> _______________________________________________ >>>>>>>> Discuss-gnuradio mailing list >>>>>>>> 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 >>>>>> >>>>>> >>>>> >>>> >>> >> > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
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