RF multicarrier signaling and antenna systems for low SNR broadband underwater communications

Most traditional underwater communication systems rely upon low data-rate acoustic communications, which cannot propagate behind objects and is confined to very narrow-band channels. We propose an alternative method supporting robust broadband radio frequency (RF) communications in low signal-to-noise ratio (SNR) undersea environments. This paper presents an integrated treatment involving broadband RF antennas and digital radio systems, potentially enabling 1 Mbps underwater communications at a medium range of 100 to 1000 meters. We describe the broadband underwater antenna design results coupled with the application of spectrally efficient multi-carrier modulation and iterative message-passing low-density parity check codes. We also present the channel modeling and underwater linklevel simulation results at 5 MHz, 10 MHz, and 15 MHz bandwidths.