Documentation of FRS Full Duplex Transceiver Using USRP Hardware
Steps for Implementing Frequency Offset Calibration with USRP Hardware
1. Connect one USRP to a machine which acts as a transmitter whereas the other USRP to another virtual machine which acts as a receiver. In addition to this, connect a spectrum analyzer at the receiver side.
2. Copy 'sdruFRSFullDuplexTransceiver.m', ‘configureFDTx.m’ and ‘configureFDRx.m’ MATLAB scripts on the transmitter machine and 'sdruFRSFullDuplexTransceiver_2.m', ‘configureFDTx.m’ and ‘configureFDRx.m’ at the receiver machine, respectively.
3. Follow the steps mentioned in the Frequency Offset Calibration document to find the value of ‘rfRxFreqCorrection’ variable in the ‘sdruFRSFullDuplexTransceiver.m’ and ‘sdruFRSFullDuplexTransceiver_2.m’ scripts and set them accordingly.
4. For both transmitter and receiver, set the value of variable ‘frsFDRxParams.RadioGain’ to 30 dB and ‘frsFDRxParams.StopTime’ to 100 seconds.
5. Type ‘findsdru’ in the command window at both transmitter and receiver end. The status should be ‘Success’ as shown in the screenshot below.
6. Run the 'sdruFRSFullDuplexTransceiver.m' (The first USRP radio sends one audio signal at 467.6125 MHz, and simultaneously receives another audio signal at 467.6625 MHz) and then 'sdruFRSFullDuplexTransceiver_2.m' (The second USRP® radio sends at 467.6625 MHz and receives at 467.6125 MHz) scripts simultaneously.
7. Observe the signal on the spectrum analyzer by setting the center frequency to 467MHz.
8. The following output is obtained on the first machine which gives the information about the USRP used.
9. Following is the output obtained from second USRP.
10. The audio file will be played in the background. The audio file used while running this example is ‘The discrete Fourier transform of real valued signal has conjugate symmetry’ and it will run till the script ends.
11. Thus this example performs full duplex transmission and reception using FRS waveforms and two USRP radios.
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