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Re: [Discuss-gnuradio] Transmitting a binary 'ones and zeroes' file for

From: rashi dixit
Subject: Re: [Discuss-gnuradio] Transmitting a binary 'ones and zeroes' file for Bit Error Analysis
Date: Fri, 29 Jun 2007 17:44:56 +0100 (BST)

Hey Tom

Thanks for the tip to use benchmark files for the same.On going through them made me realize they are just as identical to tx_voice.py, rx_voice.py !

And just as you had said, it would be necessary to keep track of the packets but I havent yet been able to figure out a way to overcome the lost packet situation.

The bottleneck is that if I could attach header (external preamble)from my side to the data then the sequence could be tracked. On trying to attach external data I dug through the code of pkt.py and packet_utils.py in  usr/local/lib/python2.4/site-packages/gnuradio/blksmpl and attached a string to 'payload' from my side.

Many-a-times receiver rejects the incoming packet saying:

terminate called after throwing an instance of 'std::runtime_error'
what(): msg length is not a multiple of d_itemsize
Aborted (core dumped)

Could you the suggest a possible way to overcome this error?

Thanks again!

Tom Rondeau <address@hidden> wrote:
rashi dixit wrote:
> Hello Everyone
> I am currently working on binary file transmission from one system to
> another, but couldnt figure a way out yet.
> Using tx_voice.py when I send a binary file with just an arbitrary
> stream of ones and zeroes, data is read and transmitted as packets
> well. But unfortunately, on receival side on the retrieval of data, it
> isnt written back into the file in the binary format as originally but
> a combinations of bits are clubbed and expressed by incomprehensible
> hashes and stars. So the data cant be deciphered.
> I tried using the GMSK modulation scheme. But the binary data chunks
> are filtered out during transmission only....probably due to the
> gaussian filter. Please check me out if I am wrong.
> Could anyone suggest a way for a ones and zeroes file to be
> transmitted? My final aim is to find the 'Bit error rate' of
> transmission form one node to another.
> Also is there any way of comparing two binary files? I mean how should
> one approach the bit error analysis keeping correlation in mind etc?
> Thanking you all
> Rashi Dixit


I'm not sue why you are using tx_voice.py for this. It seems to make
more sense to use benchmark_tx.py and benchmark_rx.py in the /digital
examples directory. This will modulate the bits with GMSK by default.
Keep in mind, though, that you _want_ to modulate the data before
transmitting it over the air.

The GNU Radio file sink/source write and read files as binary data, so
the files will look like hashes and stars when viewed with a text
editor. You can use gnuradio-core/src/utils/read_*_binary.m in
Matlab/Octave to read these files.

However, I'm not sure you want to just compare the output file to the
input file unless you also keep track of a packet number. If the header
is missed or corrupted in the current implementation, the packet is
completely dropped, which would completely screw up your calculations
unless you can tell that a full packet has been lossed. Then, you have
to decide how you want to handle the BER calculation due to one lost


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