Hi usrp-users,
I recently started working on a *multilateration* based localization scheme
to detect a tag USRP (reader). The 100MHz OFDM packets (STF +LTF +
information bits) are* transmitted at 100 MSps to the reader* via the
anchor hub USRP X310.
I am new to handling the time_spec and other features available to control
transmission. I have to transmit a really huge packet (*>130000 samples ~
1.3 to 3 ms*) so that the streaming and reception appears to be continuous
for a good duration of time frame for accurate reader detection.
Few Questions:
Q1 ; What is the maximum buffer size I can set for transmission. Is it
33445667 samples? I found it on the user manual?
Q2 : Is the read buffer on the receive streamer any different form the
transmit buffer in terms of maximum size it can receive before it goes into
overflow , API control etc?
Q3 : I assume ,* I cannot stream a 100 MSps data directly using a 1G
ethernet car*d without potential underflow. So I used tim_spec feature to
transmit after a fixed duration. Within this time the API should be able to
fill the buffer at a slower rate (33MSps if that is the max capability),
and allow smooth transmission without underflow. I am receive some packets
at the reader , but they seem to be truncated, or abruptly starting or
ending.
pseudo code to control transmission at 100MSps using 1G:
metadata.start_of_burst = true;
metadata.end_of_burst = false;
while(not stop_signal_called){
metadata.has_time_spec = false;
metadata.end_of_burst = false;
*g_usrp->set_time_now(uhd::time_spec_t(0.0)); g_time_spec =
g_usrp->get_time_now() + uhd::time_spec_t(0.04);*
metadata.time_spec =g_time_spec;
tx_streamer->send(&buff[0], buff.size(), metadata);
metadata.has_time_spec = false;
metadata.start_of_burst = false;
metadata.end_of_burst = true;
tx_streamer->send("", 0, metadata);
* boost::this_thread::sleep(boost::posix_time::milliseconds(50));*
}
Please do help. It is really a critical part of my research project. I am
limited to using a 1G Ethernet card, and I need to find a work around to
the 100MSps transmission issues.
Thanks
Karan Suri
MS. Electrical and Computers
University Of Michigan- Ann Arbor
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