Re: [Discuss-gnuradio] RFX2400+USRP buffers

[kaleem ahmad]

Any ideas or comments will be helpful for me and I am anxiously waiting!!!.

Kaleem Ahmad

kaleem ahmad wrote:
> 
> Hello everyone,
> 
> I am trying to implement a simple FSK system to measure bit error rate
> (BER), and packet loss rate (PLR) using:
> 
> 1-Linux
> 2-USRP motherboard
> 3-RFX2400 daughter card
> 
> I want to implement an echo back system where one Transceiver (say Master)
> will transmit a small frame (let say 48 byte, and important thing is that
> I neccessarily need small payload) to other transceiver (say Slave). The
> Salve returns the frame immediatelly without any processing to Master  and
> Master measures BER and PLR.
> 
> The problem which I am facing is that I am unable to transmitt such small
> packets. I have noticed that if I have a large file with let say few
> Kbytes contents then it is transmitted (partially, the end of file is
> always missing...I guess it is stuck somewhere in buffer????) but if I
> have such small packets as I metioned earlier then most of the time the
> packets are lost. If the packet is received then it is totally corrupt
> (say almost 100% BER) unlike large files which are received in very good
> quality (But important and notable point is that even the large files are
> 100% courrupt at the end). This makes me wonder why last few hundered
> bytes are always courrupt??? (for small file the whole file lies in that
> category of last few hundered bytes)
> 
> I have tried a lot but unable to solve the problem! Now can any one help
> me to understand what can be the problem? Is it somewhere in the buffers?
> Is it some sort of synchronization problem??? and which buffers (of
> USRP/RFX2400/GNURadio) are involved in such flowgraph. The flow graph with
> actual names of blocks used by me is given below (I have attached complete
> code if some one want to have a look):
> 
> Transmit path flowgraph:
> 
> gr.file_source -> gr.simple_framer -> gr.bytes_to_syms ->
> gr.interp_fir_filter_fff -> gr.frequency_modulator_fc ->
> gr.multiply_const_cc -> usrp.source_c
> 
> Receive path flowgraph:
> 
> usrp.source_c -> gr.fir_filter_ccf -> gr.quadrature_demod_cf ->
> simple_correlator -> gr.file_sink
> 
> Best Regards
> 
> Kaleem Ahmad
> 
>  http://www.nabble.com/file/p19415046/fsk_rx.py fsk_rx.py 
> http://www.nabble.com/file/p19415046/fsk_tx.py fsk_tx.py 
> 

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