5G Millimeter Wave Leakage

About This Project

The goal of this Project is to determine how well a given millimeter wave frequency (i.e. waveforms sent at frequencies above 20 MGhz, as 5G will need to be) can stay within its allotted bandwidth. This will be accomplished by measuring the amount of "leakage" - the amount of extra energy that is present due to the transmission of a wave - at various frequencies between about 25-28GHz.

Week 1

• Learned how to use some initial Linux commands and access nodes (i.e. remote computers) in Orbit Lab
• Discovered how to image nodes to load a previous software setup
• Began first tutorial on sending and viewing analog waveforms with Software Defined Radios ^{(Image 1)}

Week 2

• Sent analog waves of various shapes (Square, Sinusoidal, and Sawtooth), gains, sampling rates, wave frequencies, and center frequencies
• Tested hardware capabilities of a node of wave frequency vs sampling rate holding other factors constant
• Learned what WinSCP is and how to use it to get files from Orbit Lab nodes onto a personal laptop
• Figured out how to use WinSCP to transfer supplied code to a node
• Studied and adapted MATLAB code to plot waveforms in the time and frequency domains ^{(Image 2)}
• Began researching OFDM (Orthogonal Frequency Division Multiplexing)

Week 3

• Began sending digital waveforms with modulations (so they could actually carry information) using GNUradio and the benchmark_tx and benchmark_rx programs
• Tested out the differences between various modulations and sampling rates using the programs rx_ascii_art_dft to see the waveforms and benchmark_rx to note the quality of the transmission ^{(Image 3)}
• Found the limits of the b210 USRPs (the physical radios) at certain modulations in terms of the maximum sampling rate they could handle before underwriting (found the limits of the hardware).

*Began learning Bash to write my own scripts.

Week 4

• Wrote a bash program to simultaneously run the transmitter and receiver
• Authored another program to cycle through various modulations and sampling rates, parse the output for the final line with the results, and write that into a file
• Researched more about benchmark_tx and benchmark_rx to better understand the output
• Plotted the results in MATLab for each modulation, comparing the sampling rate of the transmission vs the number of successfully received packets of data ^{(Image 4)}
• Varied other factors such as tx gain and the packet size (a total of 1Mb of data was transmitted in a number of packets, with a smaller packet size resulting in a larger number of packets, which creates more granular data)
• Began connecting to a Spectrum Analyzer

Week 5

• Figured out how to see a signal on the spectrum analyzer by increasing the gain
• Researched and practiced effectively using the Spectrum Analyzer and how to save and move files onto a personal computer
• Conducted 49 tests to see the effects of varying gain and sampling rate on different modulations
• Began analyzing the spectrum analyzer's output in MATLab to find the total leakage in each waveform and plotting it vs the sampling rate for each modulation at various gains ^{(Image 5)} (defining the intended bandwidth to be within the -3dB bandwidth of the waveform from the peak of the signal to the peak of the noise floor)

Week 6

• Attempted to use an alternative method to determine what constitutes leakage vs intended bandwidth (using a function of the sampling rate at which the signal was sent to constitute the intended bandwidth)
• Discovered how to access the gnuradio companion (GRC) and began working on tutorials to send and receive OFDM signals.
• Wrote a few smaller programs to test out various predefined blocks ^{(Image 6)}
• Learned how to access the USRP radios via the GRC to get real (as opposed to simulated) data from other nodes

Week 7

• Adapted a tutorial to send and receive OFDM signals via gnuradio and the GRC
• Edited the GRC generated python code to script it so that I could have it automatically run trials given certain relevant parameters from the command line
• Wrote up a draft of Experiment 1 about my data from the trials with the spectrum analyzer ^{(Experiment 1)}
• Discovered an error on the sandbox I was using, causing me to switch to using the grid as I was planning on doing anyways (on the grid, the radios transmit waves via the air, as opposed to sandboxes where the USRP radios are connected via a wire).

Week 8

• Continued tests to verify that there was an error on the sandbox I had been using (sandbox 1)
• Learned how to work with different USRPs than the version I had been using previously (N210s as opposed to B210s)
• Managed to get a connection between USRPs on the grid and download the data (and adapted the python code again so I could make it automatically run)
• Wrote a few MATLab codes to analyze the data files, find the envelope of the wave to find the noise floor and the -3dB bandwidth, and calculate the total area of excess bandwidth contained in the wave ^{(Image 7)}
• Started plotting various sampling rates vs the excess area they had in the MATLab plots

Week 9

• Realized that the receiving bandwidth was too narrow for some of the sampling rates, causing me to set a standard for this experiment at 30 MHz
• Finished scripting/automating the data collection process (including the naming of files to include metadata about the sampling rate and other factors at which the signal was sent)
• Found a better way to account for noise by taking a sample of measurements with no signal transmission, finding the midpoint of each resulting graph, and averaging those midpoints to find the general noise level (as opposed to just assuming the edges of each graph necessarily represented the noise level).
• Took 20 samples of each sampling rate to find a more accurate plot comparing sampling rate vs excess area with a 90% margin of confidence bar ^{(Image 8)}

Week 10

• Wrote up Report 2 about the experiment from the previous week
• Worked to get signals using the new spectrum analyzer to get data from the millimeter wave frequencies (with a center frequency of 27GHz as opposed to previous experiments which were centered at 5GHz)