discuss-gnuradio
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Discuss-gnuradio] Question about USRP2 transmitter with OFDM packet.


From: 周亮
Subject: [Discuss-gnuradio] Question about USRP2 transmitter with OFDM packet.
Date: Sat, 18 Jun 2011 01:30:02 +0800

Hi,

One weeks ago I downloaded OFDM program (modified for USRP2, from Veljko Pejovic ) and tested with it. I got a problem when I used USRP2 to transmit OFDM packets. When I transmit continuous OFDM signals the receiver only receive some pieces of packet.  So I tried to test with one packet.

Size of my (modulated, cp added)OFDM packet is about 90KB(default ofdm parameters, fft size 512, occupied tones 200,packet size 400, etc).

First I saved one OFDM packet in a file.
Then I used GRC to read  this packet content from file and send it to USRP2 sink.(Just one packet). Center frequency 2.4GHz( with XCVR2450)
At last I used GRC to receive packet with another USRP2, and record the received samples.

It seems that the USRP2 transmitter could not send the whole OFDM packet properly. With interpolation/decimation rate 32, the receiver could see  about first 30% of OFDM packet. With interpolation/decimation rate 16 and 8, about 70% of the OFDM packet is received...With interpolation rate 14 the OFDM packet is broken into 2 pieces...

I also found that no matter what interpolation rate is used, the OFDM tx program just send data to USRP2 at same data rate, which seems unreasonable.

After all, it seems that if main program send ethernet packages too fast, USRP2 tx buffer will be overflowed and the transmit signal will be lost.  Is it true?

If so, what is size of tx buffer in USRP2? Is it possible to control the ethernet data rate so that the tx buffer in USRP2 is not overflowed?

Please give some advices, all replies are appreciated!

Thank you!

Liang

reply via email to

[Prev in Thread] Current Thread [Next in Thread]