A 31.8kbps/8kHz underwater acoustic single carrier frequency division multiplexing (SC-FDM) communication system with forward error correction

This paper proposes an underwater acoustic Single Carrier Frequency Division Multiplexing (SC-FDM) communication system with a forward error correction to transmit image or movie data packet from deep sea ROV (Remotely operated vehicle) etc. to surface ship. Since the SC-FDM is basically Orthogonal Frequency Division Multiple Access (OFDM) with pre- and post-coding, frequency bandwidth is efficiently utilized to deliver high data bandwidth as well as lower Peak-to-Average-Power Ratio (PAPR) of the transmitting signal. In order to realize error-free communication adaptively to wide range of Carrier signal to Noise power Ratio CNRs, 3 carrier modulations such as QPSK / 16QAM / 64QAM and 5 code rates are supported. Using 64QAM with code rate R=7/8, a 31.8 kbps in 8kHz maximum channel bandwidth has been achieved. The system utilized 20–28 kHz and subcarrier spacing of 50 Hz. Total number of sub-carriers is 161. The system is verified by Ocean experiment at Suruga Bay with 1000m deep sea in Shizuoka, Japan. At the depth of 100m, with 64QAM and code rate R= 3/4 (Rate=27.241 kb/s), Packet Error Rate (PER) = 0 % is observed. At the depth of 400m, with 64QAM and R=2/3 (Rate=24.213 kb/s), PER=0 % is also achieved. At the depth of both 700 and 1000m, with 16QAM and code rate R= 2/3 (Rate=16.140 kb/s), PER closed to 0 % is realized.