High-data-rate ultrasonic through-metal communication.

A link-adaptive frequency division multiplexing (OFDM) ultrasonic physical layer is proposed for high-data-rate communications through metal walls. The ultrasonic link allows for communication without physical penetration of the metal barrier. Link-adaptive OFDM mitigates the severe frequency- selective fading of the ultrasonic channel and greatly improves throughput over impulse or narrowband communication systems. Throughput improvements of 300% are demonstrated over current narrowband low-frequency techniques, and show improved spectral efficiency over high-frequency techniques found in the literature.