RFI Detection and Identification at OVRO Using Pseudonymetry

Protecting radio astronomy observatories from unintended interference is critical as wireless transmissions increases near protected bands. While database-driven coordination frameworks and radio quiet zones exist, they cannot rapidly identify or suppress specific interfering transmitters, especially at low signal-to-noise ratio (SNR) levels. This paper presents the first over-the-air field demonstration of Pseudonymetry at the Owens Valley Radio Observatory (OVRO), illustrating cooperative spectrum sharing between heterogeneous wireless systems. In our experiment, a narrow-band secondary transmitter embeds a pseudonym watermark into its signal, while the wide-band radio telescope passively extracts the watermark from spectrogram data. Results show that interference can be reliably detected and the interfering device uniquely identified even at low SNR where conventional demodulation is infeasible. These findings validate that passive scientific receivers can participate in a lightweight feedback loop to trigger shutdown of harmful transmissions, demonstrating the potential of Pseudonymetry as a complementary enforcement tool for protecting radio astronomy environments.

Sensing and Stopping Interfering Secondary Users: Validation of an Efficient Spectrum Sharing System

We present the design and validation of Stoppable Secondary Use (StopSec), a privacy-preserving protocol with the capability to identify a secondary user (SU) causing interference to a primary user (PU) and to act quickly to stop the interference. All users are served by a database that provides a feedback mechanism from a PU to an interfering SU. We introduce a new lightweight and robust method to watermark an SU's OFDM packet. Through extensive over-the-air real-time experiments, we evaluate StopSec in terms of interference detection, identification, and stopping latency, as well as impact on SUs. We show that the watermarking method avoids negative impact to the secondary data link and is robust to real-world time-varying channels. Interfering SUs can be stopped in under 150 milliseconds, and when multiple users are simultaneously interfering, they can all be stopped. Even when the interference is 10 dB lower than the noise power, StopSec successfully stops interfering SUs within a few seconds of their appearance in the channel. StopSec can be an effective spectrum sharing protocol for cases when interference to a PU must be quickly and automatically stopped.