Enhanced Data Rate Performance for VLF/LF

"Fleet Submarine Broadcast System (FSBS) VLF/LF communications are severely bandwidth limited due to the high Q of the transmit antennas and the low frequency of the VLF/LF band. The existing communications modes were designed using Minimum Shift Key (MSK)waveform modulation built into analog modulation and demodulation equipment. Soon the very capable digital Submarine Low Frequency/Very Low Frequency VMEbus Receiver (SLVR) will be deployed throughout the submarine fleet, and the analog modulators will bereplaced by digital modulators. Advanced modulation techniques such as partial response continuous phase modulation (CPM) at higher baud rates can now be considered for implementation in FSBS communications equipment. In addition, Low Density Parity CheckCodes (LDPCC) that provide additional coverage performance through forward error correction (FEC) are already being used for FSBS communications and additional improvements in these codes have been identified. Finally, incremental improvements in currentRange Extension Mode (REM) message data compression are also feasible. TSC proposes to investigate designs that incorporate a combination of advanced modulation techniques, adaptive data compression, and larger block size and higher code rate LDPCC forthe band-limited VLF communication channel in order to increase the data rate of FSBS information transfer 2 to 5 times yet maintain good coverage range.This research will establish t