Watermarking of OFDM for Pseudonymetry: Analysis and Experimental Results

This paper presents new results for pseudonymetry, a closed-loop feedback mechanism in which active transmissions are watermarked with a pseudonym that, if it interferes with a protected passive radio receiver, can be demodulated and used to force the transmitter off of the band. This paper addresses amplitude-based watermarking of orthogonal frequency division multiplexing (OFDM) packets. We quantify the ability of a passive receiver to decode the watermark at very low signal-to-noise ratio (SNR) and the impact on the intended communication link. We demonstrate, using a testbed of software-defined radios, that the experimental implementation of pseudonymetry matches the theoretical analysis very closely. Our results quantify a fundamental trade-off in the design of pseudonymetry for OFDM and provide a practical pseudonym receiver design.