Thursday, May 17, 2018

UTSC Air Interface: First Tests

Tonight I enlisted the help of an associate in Texas, Tech2025 (aka RFShibe) with transmitting a dummy UTSC signal. It was kind of funny because he casually asked if a HackRF could transmit UTSC, which led me to ask if he had access to one. One thing led to another, and he ended up helping me test my air interface.

I would have done it myself, and indeed I tried numerous times, but my LimeSDR Mini isn't operating like I need it to, even after the firmware upgrade.

Fortunately, Tech2025 happened to own a HackRF and agreed to transmit for me if I sent a flowgraph, and then he would show the result on an RTL dongle connected to another computer.

After I built a GNUradio flowgraph that uses a Random Source block to transmit QPSK at the proper clock rate for UTSC, I sent it via Discord's file sharing function. Tech2025 transmitted it and sent back screenshots to prove that it worked.

Here's how it looks on my end in GNUradio:

In the following real-world test, a QPSK signal carries random bytes ranging from 0 to 255.

Credit: Tech2025/RFShibe

In the next image, the range was from 0 to 3.

Credit: Tech2025/RFShibe

This signal is roughly as wide as a UTSC channel should be, so we're off to a good start.

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