UHD1: Spectrum Monitoring

This page is still under development and the experiment described on this page is not yet generally available.

1) Experiment Overview

Experiment Definition: This experiment performs spectrum monitoring between 87 MHz and 6 GHz in a loop. The experimenter can also modify the code to focus on specific frequencies so that the full frequency sweep happens faster. Each full sweep is saved as a .mat file that contains powers measured at each frequency bin.

Experiment Goals: The spectrum monitoring starts at the center frequency fc=100 MHz with a sampling rate of 30.72 MHz. 500k IQ samples are collected and Welch's method is used to estimate the power spectral density (PSD) using 512 point FFT which corresponds to 30.72 MHz/512=60 kHz frequency bin spacing. We then remove 84 of the bins (42 bins from each side) and keep 428 frequency bins. Then the center frequency is increased by 25.68 MHz, IQ samples are collected and PSD is estimated. This is repeated until the center frequency reaches 6 GHz. Eventually, we end up with 231 bands each having 428 measurements and a total of 98868 measurements for a complete sweep which is saved as a separate mat file under /root/Results.       

Experiment Modes: This experiment is available in both EMULATION and TESTBED modes. However, to run this experiment in the EMULATION mode, you will need to couple this experiment with one of the other sample experiments to introduce a signal source, e.g. with SE1 sample experiment to introduce an LTE eNB.  

Configuration Parameters:

• USRP RX gain 

• USRP sampling rate

• Starting center frequency

• Number of frequencies

• Frequency increment

• FFT size

• Number of frequency bins to keep after PSD estimation

• Experiment duration

2) Performing the Experiment:

Login to the E-VM and navigate to the folder containing all the Radio scripts 

$ cd /root/Profiles/ProfileScripts/Radio 

Copy the spectrum monitoring script as startRadio.sh

$ cp Samples/startSpectrumMonitoring.sh startRadio.sh 

Use an editor to uncomment the line  /Radio/startRadio.sh in /root/startexperiment.sh and run the following command:

$ /root/startexperiment.sh  

3) Modifying the Experiment Configuration Parameters:

The python file located at the  /root/AERPAW-Dev/AHN/C-VM/RF_monitoring/myConstants.py can be edited to modify the parameters in the experiment

USRP RX gain (default value:40)

gainRX = (40,) 

USRP sampling rate (default value: 30.72 MHz)

fs = 30.72e6 

Starting center frequency (default value:100 MHz)

f_start = 100e6 

Number of frequencies (default value:231)

n_freq = 231 

Frequency increment (default value:25.68 MHz)

dfc = 25.68e6 

FFT size (default value: 512)

FFT_SIZE = 512 

The number of frequency bins to keep after PSD estimation is adjusted using cutoff_factor (default value:428 which is found by multiplying FFT Size and cutoff factor). 

cutoff_factor = 0.836

Experiment duration (default value: 24 hours). This can be kept large because when /root/stopexperiment.sh is called the experiment will end. 

duration=24

4) Results:

The mat files that contain PSD estimates can be loaded in MATLAB for post-processing. The experiment also creates a log file under /root/Results.