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USRP Transmit speed and receive quality depend of file size and Payload Length at Packet Encoder?

Posted: Fri Apr 20, 2018 7:33 am
by pilot327
Hi,
i use this flowgraph PIC 1 (01_flowgraph)

USRP transmits file (txt, picture and video) and receives this file at the same time

1. If i want to increase transmit speed i will increase PAYLOAD LENGTH in packet encoder. Is it the right way?

2.When I changed Payload Length in Packet Encoder
from 1 to 128 -- transmit speed increased from 4kb/s to 10kb/s
from 128 to 256 --  transmit speed increased from 10kb/s to 10.2kb/s

All of this changes work correctly only with files as of 61,2kb. When I try to transmit 5mb file, only 523kb are received. Why does it happen?

3. I thought that if I decreased samples/ symbol from 32 to 4 the transmit speed would increase. But it wasnt. Why?

4. When I wrote
in Packet Decoder:
   sps :32
   bps :8
   payload l: 1
and decreased sample_rate from 250k to 32k,only 3Mb out of 6Mb were received. Why does it happen? I thought only the transmit speed would decreased.

5. And why is receive width on PIC 2 (receive_width) not the same as transmit width PIC 3 (transmit_width)?
(QT sink was under the top_block when executing was running)
You can see that bandwidths of both QT sink are the same.

I use gnuradio 3.7.10 with USRP1.
I want to understand gnuradio logic and radiowave transmitting, but I am new in it.

Thank you for your answers.