Re: [Discuss-gnuradio] RFX2400+USRP buffers

[kaleem ahmad]

Dear All,

I have tried different packet sizes and I found that 2048 bytes data at the
end is always missing:

With 128 byte packet size 17 last packets were not received
With 256 byte packet size 8 last packets were not received
With 512 byte packet size 4 last packets were not received
With 1024 byte packet size 2 last packets were not received

Can some one give me any clue??????? Actually one possible solution can be
to send 2048 bytes dummy data at the end of every packet, but the problem is
I want to send small packets of not more than 100 bytes...so it is large
overhead for me...So if someone can give me some clue about where this data
is being lost then it will be a great help????

Best Regards



kaleem ahmad wrote:
> 
> 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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