Re: [Discuss-gnuradio] bpsk lost some packet when transmit data discontinuously

[Michael Berman]

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 at http://code.google.com/p/softwaredefinedradio .  If you look at .../trunk/src/Data_Path, there is a modified Python file for packetizer.py.  You may also want to look at the dpsk.py file in this directory, as it shows 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 is 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:

Hi:

I have some problem about dbpsk and bpsk using benchmark_tx/rx.py with some
modification.

My experiment set up was that the transmitter waits for a time delay (0.5 s)
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 work
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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