Acoustic Relay (FSK — Frequency-Shift Keying)
Acoustic relay is a communication method that transmits digital data through sound waves using Frequency-Shift Keying (FSK) modulation. In FSK, different audio frequencies represent binary 0 and 1 values. Acoustic communication operates at extremely low data rates (typically tens to hundreds of bits per second) but can function through mediums impenetrable to radio waves — underwater, through walls, and in RF-shielded environments. Military applications include submarine communication, building-penetrating messaging in urban operations, and air-gapped data transfer between isolated systems. The severe bandwidth constraints of acoustic relay demand ultra-compact message formats.
How XO Defense Addresses This
The 25-byte Mustard Envelope is compatible with acoustic relay transport. At 200 bits (25 bytes × 8 bits), a Mustard Envelope can be transmitted acoustically in approximately 2-4 seconds at typical FSK data rates, enabling real-time operational messaging through underwater channels or RF-denied environments. The Mustard Envelope's fixed-length format eliminates the need for frame synchronization or length headers, simplifying the acoustic modem implementation. This makes XO Defense one of the only protocol stacks that can maintain full operational capability over acoustic channels.
Learn how XO Defense's 25-byte protocol stack operates in the most constrained environments.
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