[Discuss-gnuradio] Active Reflector

[Rafael Acurcio]

Hello all,

I'm trying to do ranging using two USRPs N210.

The idea is that the first USRP sends a signal and then the second USRP recognize it and send the signal back. Looking to the turnaround time I would be able to know the ranging.

Despite some problems that I already had, right now I'm stuck with the second USRP.

To measure the time I'm synchronizing the rx ant tx from the first USRP using the following code:

        now = self.uhd_usrp_sink_0.get_time_now()
        self.uhd_usrp_source_0.set_start_time(uhd.time_spec_t(0.1) + now)
        self.uhd_usrp_sink_0.set_start_time(uhd.time_spec_t(0.1) + now)

Using the fisrt USRP I can do ranging, connecting both (rx and tx) together, with a good precision. However I couldn't make the second USRP work yet. When I try to synchronize the tx and rx like I did in the first USRP I get a bunch of Ls (late packages) in the terminal. The code drop all the packages.

My gnuRadioCompanion blocks for the second USRP looks roughly like

USRP Source -> threshold -> USRP Sink

There's a better way to solve that problem?

Why do I get the late packages?

Thanks in advance,

Rafael.

PS: To analyze the data that I'm sending I'm using File Sink block and analyzing the data after the transmission.