[Discuss-gnuradio] RFX2400+USRP buffers

[kaleem ahmad]

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 
-- 
View this message in context: 
http://www.nabble.com/RFX2400%2BUSRP-buffers-tp19415046p19415046.html
Sent from the GnuRadio mailing list archive at Nabble.com.