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

[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 ( it is working flowgraph and you can use it free).

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 3.6.5 with GNOME.
I want to understand gnuradio logic and radiowave transmitting, but I am new in it.

Thank you for your answers.

[sunaenae]

Hi pilot327,

Thanks for reaching out! What specific device are you using? Also, Ettus Support might actually be the best resource in regards to GNU Radio programming, since all NI USRP devices are mostly programmed using the NI-USRP driver. You can reach out to Ettus support here. In addition, sample rate is not the same as symbol rate, so I would not expect them to be linked linearly in the way you expect.

Best,

Sunayna