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Coding Structure

Coherent Modes, BPSK and QPSK​

All coherent payload modes use:

  • A common 1/2-rate convolutional FEC, K=7
  • Identical symbol rate and bandwidth
  • Repetition coding to adjust robustness

Changing the payload mode does not change Doppler tolerance or multipath behavior. The only variable is the processing gain introduced by additional redundancy.

Uncoded Mode, QPSK_10240bps​

QPSK_10240bps bypasses FEC and repetition entirely. It doubles the information rate of QPSK_5120bps but requires significantly higher SNR.

This mode is intended for users implementing custom external FEC, such as LDPC, Turbo, or Fountain codes.

FH-FSK Mode​

FH_80bps uses a frequency-hopped narrowband FSK waveform selected for extremely low-SNR or highly variable acoustic environments. It provides the highest robustness and is useful for long-range or minimal-SNR command and control links.