Hi Sreeraj and Tom, For the discontinuous mode, by cutting the freq_bw to below half of the default value, I found that for differential_bpsk, the packet loss rate can be improved(from 30% to 70%), but for non-differential bpsk, the improvement is hard to see. Especially, for non-differential bpsk, I found that often the whole burst (5 packets) could lost. Maybe, it is due to the Phase rotation. I am still trying to investigate.
On Thu, Mar 7, 2013 at 11:08 AM, Sreeraj Rajendran <srees4sr...@yahoo.co.in>wrote: > Alex, > > That one is non data aided(no preamble) frequency syncronization. As Tom > mentioned FLL must be the slowest one in the three. > > Did you try adjusting loop bandwidth?. There is an example_fll example in > gr-digial. Just try that one and check how many symbols/samples it takes to > settle. > > Just go through the papers I mentioned and that idea is easy to implement > to do coarse synchronization during fast burst transmissions. > > > --- > Regards > Sreeraj Rajendran > http://home.iitb.ac.in/~rsreeraj > > ------------------------------ > *From:* Alex Zhang <cingular.a...@gmail.com> > *To:* Sreeraj Rajendran <srees4sr...@yahoo.co.in> > *Sent:* Thursday, 7 March 2013 10:24 PM > > *Subject:* Re: [Discuss-gnuradio] Very low packet loss rate for the > discontinuous BPSK communications- the analysis and looking for solution > > Dear Sreeraj, > > You mentioned the openloop synch algorithms. Are they refered to the > preamble based carrier recovery? > > Thanks > > > On Mon, Mar 4, 2013 at 8:03 AM, Sreeraj Rajendran <srees4sr...@yahoo.co.in > > wrote: > > Alex, > > If Adeel's solution is not meeting your burst transmission specs, you can > try implementing some fast openloop synchro algorithms given in [1],[2]. > You could look into some data aided schemes too, though I haven't tried > those yet. > > > [1] Digital Communication Receivers, Heinrich Meyr, Section 8.2.2 > [2] Two Frequency Estimation Schemes Operating Independently of Timing > Information, Ferdinand Classen and Heinrich Meyr > > --- > Regards > Sreeraj Rajendran > http://home.iitb.ac.in/~rsreeraj > > ------------------------------ > *From:* Adeel Anwar <adeela...@gmail.com> > *To:* Alex Zhang <cingular.a...@gmail.com> > *Cc:* discuss-gnuradio@gnu.org > *Sent:* Monday, 4 March 2013 5:51 PM > *Subject:* Re: [Discuss-gnuradio] Very low packet loss rate for the > discontinuous BPSK communications- the analysis and looking for solution > > Alex, > > 1: U can try adjusting the synchronization loops bandwidth (Phase/Timing > etc) see PFB_Timing documentation > 2: Try reducing the receiver gain (for a constant tx-amplitude/gain) or > reduce transmission amplitude/gain (for constant rx gain) > > -Adeel > > > > > > > On Sat, Mar 2, 2013 at 10:21 AM, Alex Zhang <cingular.a...@gmail.com>wrote: > > I think you may rarely get the correct packet with pktno = 0, in > continuous mode, as my guess. Your received correct packet starts from > pktno = 1. > Could you also try the discontinuous mode for the BPSK communications? > > My question is actually a problem that how to implement a more reliable > BPSK mod/demod in burst mode. The current bpsk example in GNURadio does not > work well in burst mode. > > > On Fri, Mar 1, 2013 at 11:12 PM, Manu T S <manu.t.s...@gmail.com> wrote: > > Alex, > > If it was about loosing sync, we would mostly loose the first packet even > if we are sending in continuous mode. I personally face no such issues. > > > On Sat, Mar 2, 2013 at 3:25 AM, Alex Zhang <cingular.a...@gmail.com>wrote: > > Seems no one can shed a light on this topic? > > > On Thu, Feb 28, 2013 at 10:25 PM, Alex Zhang <cingular.a...@gmail.com>wrote: > > Hello, > > In the current gr-digital/narrowband, I am using the benchmark_tx.py and > rx.py to test the bpsk communications. > It is found that the packet loss rate is very high (70% loss) in > discontinuous mode where every 5 packets are in a burst. But in continuous > mode, the paket loss rate is less than 10% for the same point to point > link. > > I captured the waveform data. From the observed result, it seems that for > each burst (5 packet), the bpsk receiver needs to re-do the frequency/time > sync. This will directly causes that the first packet of each burst will > definitely be crashed. Also, some burst can not be demodulated correctly at > all. For the same reason, even in the continuous mode, the very first > packet is also crashed at the receiver. > > I have tried to add very long preamble for each packet to ensure the data > part of the packet can be received in well sync status. But the result is > not very good. > > Before I get further investigation on the solutions, just wondering if any > ideas or existing work within this community. > > -- > > Alex, > *Dreams can come true – just believe.* > > > > > -- > > Alex, > *Dreams can come true – just believe.* > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > > -- > Manu T S > > > > > -- > > Alex, > *Dreams can come true – just believe.* > > _______________________________________________ > 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 > > > > > > -- > > Alex, > *Dreams can come true – just believe.* > > > -- Alex, *Dreams can come true – just believe.*
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