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Utilizing JANUS for Very High Frequency Underwater Acoustic Modem

JANUS is a physical layer communication standard for underwater acoustic communications published by North Atlantic Treaty Organization (NATO) in 2017. Instead of the nominal frequency band of 9440 – 13600 Hz specified in the standard, we adopt the JANUS packet for a very high frequency band spanning from 100 kHz to 130 kHz. We also add cargo packets in the same frequency band using JANUS fast mode with a symbol rate of 23 ksps and with either Binary Phase shift Keying (BPSK) or Quadrature PSK (QPSK) modulation. Experiments conducted in swimming pools show that the adopted JANUS packet can successfully achieve carrier and frame synchronization in all cases but the tolerance of different time of arrival of the signal needs to be improved in the receiver program. In addition, the decoding of the 64-bit JANUS baseline packet may suffer in severe multipath environment, which in turn degrades the detection of cargo packets.