Enhancement of Ground-to-Aircraft Communication Using Audio Watermarking

This paper presents research on improving the intelligibility of spoken messages transmitted to aircraft from a ground station. The proposed solution is based on the selective calling (SELCAL) system and the audio watermarking technique. The most important elements of a spoken message (commands, numerical values) are transmitted as a watermark embedded in the speech signal and are displayed to the cockpit crew. The synchronization signal is embedded in SELCAL duo-tones. The proposed system is resistant to resampling and channel noise (at SNR > 25 dB).