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Re: [Discuss-gnuradio] bpsk lost some packet when transmit data disconti
Re: [Discuss-gnuradio] bpsk lost some packet when transmit data discontinuously
Tue, 9 Mar 2010 06:08:02 -0800 (PST)
Thanks for your reply.
I thought that the problem can not get enough data to fill up a packet could
happen on any modulator.
But why we could receive every packet properly when using dbpsk and lost
packets when using bpsk?
(Under transmitting each packet with a time interval.)
And I went through the packetizer.py quickly and found that it seems that
different modulations have different packet preambles.
preamble = conv_packed_binary_string_to_1_0_string('\xA4\xF2')
preamble_bpsk = conv_packed_binary_string_to_1_0_string('\x55\x55\x55')
Does this different cause the bpsk can not receive data properly?
Again, Thanks for your reply. It really helps me a lot.
I am deeply appreciative.
Michael Berman-2 wrote:
> The problem does not lie with the bpsk modulator, the problem is in the
> packetizer. The packetizer waits until it gets enough data to completely
> fill up a packet, generally resulting in the loss of the last packet as
> there is not enough data to fill it perfectly.
> There is a modified copy of the packetizer.py that you could use that has
> been set up to handle this specific async digital communication scenario
> http://code.google.com/p/softwaredefinedradio . If you look at
> .../trunk/src/Data_Path, there is a modified Python file for
> You may also want to look at the dpsk.py file in this directory, as it
> how to set up the top level design to use a message queue for the
> asynchronous sending of packets. The last (useful) file in this director
> the txrx_controller.py, which establishes a custom rudimentary protocol to
> ensure packet retrieval went well, and all information is received
> properly. There is some documentation for this in the Docs folder.
> -Michael Berman
> On Tue, Mar 9, 2010 at 12:03 AM, Fisheep <address@hidden> wrote:
>> I have some problem about dbpsk and bpsk using benchmark_tx/rx.py with
>> My experiment set up was that the transmitter waits for a time delay (0.5
>> after sending a packet.
>> It means that we transmit data discontinuously.
>> If we using dbpsk modulation, we can successfully receive every packet.
>> But if we removed the differential encoder/decoder (equals to bpsk
>> modulation), we uaually
>> lost some packet (almost half of the data lost).
>> However, when we transmit data continuously,the bpsk modulation seems
>> fine and we can successfully receive every packet.
>> My problem is that what reason causing the bpsk modulation can not
>> successfully receive packet when
>> transmit data discontinuously.
>> Could anyone have any idea about it, please let me know.
>> I am deeply appreciative.
>> Fisheep :)
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