|
From: | Alex Zhang |
Subject: | Re: [Discuss-gnuradio] Very low packet loss rate for the discontinuous BPSK communications- the analysis and looking for solution |
Date: | Sat, 16 Mar 2013 14:19:38 -0500 |
On Fri, Mar 15, 2013 at 11:33 PM, Alex Zhang <address@hidden> wrote:Are you handling the phase ambiguity in the receiver somehow? The way
> 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.
things lock, the phases for BPSK could off by 180 degrees, so all 1's
are 0's and all 0's are 1's. So when you lock with a burst, you have a
50/50 chance of locking on the wrong phase and so all of your bits are
going to be wrong. You'd have to detect this and flip everything.
Tom
> On Thu, Mar 7, 2013 at 11:08 AM, Sreeraj Rajendran <address@hidden>
> 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 <address@hidden>
>> To: Sreeraj Rajendran <address@hidden>
>> 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
>> <address@hidden> 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 <address@hidden>
>> To: Alex Zhang <address@hidden>
>> Cc: address@hidden
>> 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 <address@hidden>
>> 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 <address@hidden> 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 <address@hidden>
>> wrote:
>>
>> Seems no one can shed a light on this topic?
>>
>>
>> On Thu, Feb 28, 2013 at 10:25 PM, Alex Zhang <address@hidden>
>> 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
>> address@hidden
>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>
>>
>>
>>
>> --
>> Manu T S
>>
>>
>>
>>
>> --
>>
>> Alex,
>> Dreams can come true – just believe.
>>
>> _______________________________________________
>> Discuss-gnuradio mailing list
>> address@hidden
>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>
>>
>>
>> _______________________________________________
>> Discuss-gnuradio mailing list
>> address@hidden
>> 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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> Discuss-gnuradio mailing list
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