RE: Question about latency

GNU Radio
1

Hi,

On Thu, 4/2/09, Matigakis E. [email protected] wrote:

I think what I’m trying to do is very difficult if at all possible with > flowgraphs. So I will try to use in-band signaling code. Is there >
something similar to gr-howto-write-a-block for using mbloks?

Thanks

Manolis

If you are trying to do just an RF repeater (digitally connecting TX IF
and RX IF ), I don’t think the time is much as 100msec with 4MHz. There
is something wrong. I suggest to you to use BasicRX and Basic TX in the
first.

If you want to measure the delay from end to end , I suggest the
following idea (I didn’t implement and tried it, it just came on my mind
while reading your email):

Connect the output of Basic TX to the input of basic RX through 20 dB
attenuator. Start grc, connect a saw tooth signal generator to usrp
sink. Connect usrp source to oscilloscope graphical sink (channel A).
For the same scope sink, connect the saw tooth source to its other
channel (channel B). You should now see two saw tooth signals one that
send to TX and the other is the received RX. Vary saw tooth frequency
and measure the delay between the start of these two signals. This will
be the end to end latency. Of course it will depend you your PC speed
and its OS.

Let me know if it works for you.

Best Regards,

Firas

2

Hi,

I don’t have a BasicRX db. Can’t I do the same with RFX2400?
Is it dangerous to burn the db if I connect the input to the
output directly?

Manolis

-----Αρχικό μήνυμα-----
Από: Firas A. [mailto:[email protected]]
Αποστολή: Πεμ 2/4/2009 18:25
Προς: Matigakis E.
Κοιν.: [email protected]
Θέμα: RE: [Discuss-gnuradio] Question about latency

Hi,

On Thu, 4/2/09, Matigakis E. [email protected] wrote:

I think what I’m trying to do is very difficult if at all possible with > flowgraphs. So I will try to use in-band signaling code. Is there >
something similar to gr-howto-write-a-block for using mbloks?

Thanks

Manolis

If you are trying to do just an RF repeater (digitally connecting TX IF
and RX IF ), I don’t think the time is much as 100msec with 4MHz. There
is something wrong. I suggest to you to use BasicRX and Basic TX in the
first.

If you want to measure the delay from end to end , I suggest the
following idea (I didn’t implement and tried it, it just came on my mind
while reading your email):

Connect the output of Basic TX to the input of basic RX through 20 dB
attenuator. Start grc, connect a saw tooth signal generator to usrp
sink. Connect usrp source to oscilloscope graphical sink (channel A).
For the same scope sink, connect the saw tooth source to its other
channel (channel B). You should now see two saw tooth signals one that
send to TX and the other is the received RX. Vary saw tooth frequency
and measure the delay between the start of these two signals. This will
be the end to end latency. Of course it will depend you your PC speed
and its OS.

Let me know if it works for you.

Best Regards,

Firas