Humphreys claims to have given the most complete characterization of Starlink's signals to date in a paper he has posted on his lab's website. He says that this information is the first step in the development of a new global navigation technology that would operate on its own.
Humphreys says that the Starlink system signal is a secret. When they were more willing to work with us, they didn't reveal any of the signal structure to us. We had to build a radio telescope from the ground up.
To start the project, UT Austin used a Starlink terminal to stream high-definition tennis videos from the internet. A separate nearby antenna was able to listen in on the Starlink signals.
Humphreys realized that Starlink uses a technology calledOFDM. OFDM was developed at Bell Labs in the 1960s and is now used in 5G. Mark Psiaki is a professor at Virginia Tech. A way to pack the most bits per second into a given bandwidth
UT Austin researchers didn't try to break Starlink's encryption or access user data from satellites. They wanted to use the signals beamed down by the satellites to help the receiver. Humphreys was pleasantly surprised to find that they had more Synchronized Sequences than is required.
Clues to the satellite's location and speed are contained in each sequence. Humphreys says that it is wonderful for dual use of their system for positioning.
If the receiver has a good idea of the satellites' movements, it can use the sequence's regularity to calculate the distance from one satellite to another. Humphreys says a receiver can locate itself within about 30 meters by repeating this process.
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