1. Introduction
RF Fingerprinting, also known as Specific Emitter Identification (SEI), is a signals intelligence (SIGINT) technique that identifies individual radio transmitters based on unique, unintentional hardware-level impairments introduced during the manufacturing process. These impairments, often termed "radiometric signatures" or "RF fingerprints," are persistent and difficult to alter, providing a physical-layer biometric for wireless devices. As of 2025-2026, SEI has evolved from a laboratory curiosity to a critical capability for spectrum management, cybersecurity, and national security, driven by advances in deep learning and the proliferation of low-cost software-defined radio (SDR) platforms.
The core premise is that no two transmitters are perfectly identical. Variations in analog components—such as oscillators, power amplifiers, mixers, and digital-to-analog converters (DACs)—create subtle, device-specific distortions in the emitted radio signal. These distortions are superimposed on the intended digital modulation and are detectable in the in-phase and quadrature (IQ) samples of the received signal.