[Discuss-gnuradio] Packet Communications Examples do not work

[Ding Zhang]

Hi There!

I am new to Gnuradio and I am trying to set up the packet sending and receiving using examples in gr-digital/examples/uhd_packet_tx and rx. 

I read the instruction Packet Communications in Gnuradio wiki. It helps a lot but when I run the examples, the RX part did not work. 

Specifically, the uhd_packet_tx works well but for uhd_packet_rx, it began to freeze after 20-30 seconds. However, even when it was active during first 20 seconds, there was no signal output from the PCS block.(I  am using QT time sink to check the output of every block. I can see signals from the previous Correlation Estimator block but nothing from the PCS Block). 

So, my first question is how I can fix the freeze problem. I checked the web and thought it might because of the Sample rate. But I have decreased the sample rate to 200k, it still had the problem. 

The second problem is why I cannot receive anything from the output of PCS(timing port marked in the example). I found out a similar problem here(http://gnuradio.4.n7.nabble.com/Overview-of-packet-decoding-td62625.html), but it was not solved also. 

I am using two USRP N210 and SBX as TX and RX respectively and connect them directly by SMA-SMA cable. The Frequency of UHD source and sink are the default setting 484M. Sample Rate is 200k to 1M. Rx Gain is 30 and TX Gain is 10. The clock source and time source are set to default instead of GPSDO because I have no GPSDO kit. Except these, I did change other parameters in the examples.

GNU Radio Companion version is 3.7.10.1.  Linux ubuntu 4.4.0-64-generic #85-Ubuntu SMP Mon Feb 20 11:50:30 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

Thanks for your time and I appreciate if anyone can give some suggestions. 

Thanks,

Ding Zhang