Time sync issue in USRP x410 with basebandTransmitter & basebandReceiver

Hello,

I have successfully established communication with usrp in loopback mode,

But when I connected two individual usrp's and tried to transmit and capture i was getting a mismatch between both radios time,

Tried using clock source and time source as internal and also GPSDO.

This is my code:

clc;

clearvars -except tx rx

radio1="Radio_1";

if ~exist('tx', 'var') || ~isvalid(tx)

tx=basebandTransmitter(radio1,"TransmitDataType","double","Antennas","DB0:RF1:TX/RX0","Preload",true,"RadioGain",20,"CenterFrequency",512e6,"SampleRate",2e6);

end

radio2="Radio_2";

if ~exist('rx', 'var') || ~isvalid(rx)

rx=basebandReceiver(radio2,"Antennas","DB0:RF1:RX1","CaptureDataType","double","Preload",true,"RadioGain",20,"CenterFrequency",512e6,"SampleRate",2e6);

end

setTimeNextPPS(radioConfigurations("Radio_1"), 0);

setTimeNextPPS(radioConfigurations("Radio_2"), 0);

t1 = getRadioTime(r1);

t2 = getRadioTime(r2);

fprintf('\nRadio 1 time: %.9f \n', t1);

fprintf('Radio 2 time: %.9f \n', t2);

fprintf('Time difference: %.9f ms\n', (t1 - t2));

Output:

Radio 1 time: 8.289583870

Radio 2 time: 8.291099585

Time difference: -0.001515715 secs

My issues:

1. I was manually setting both radios time to zero by setting the next PPS, Even then time mistamatch issue is there in between two radios.
2. Is there any way that i can set radio 1 as master and radio 2 as slave, And import clock and time source from radio 1 to radio 2.
3. Or is there any way that i can configure trig in/out port of one usrp to output PPS signal for other radio.
4. Even when both radio's are connected and locked to GPSDO, there is mismatch in both radios time.

[Jieming Xu]

Hello Varun,

Thank you for using the Wireless Testbench Toolbox and for your inquiry.

Issue 1: Yes, this behavior is expected. Since getRadioTime(r1) and getRadioTime(r2) are executed consecutively, the time gap between these two function calls is the difference you observe. To achieve your desired result, I suggest using the function getTimeLastPPS. This will return the device time at the last PPS signal. Please note that you need a PPS box connected to both devices.

Issue 2: You can synchronize device 2 using the clock from device 1.

Issue 3: No, this feature is not supported in the current MATLAB version.

Issue 4: Yes, it is supportted. Please pay attention, the GPSDO need longer time to take effect than PPS. Please allow longer time for GPSDO to work.