Further results on multicarrier MFSK based underwater acoustic communications

Multicarrier MM-ary frequency shift keying (MFSK), a parallel transmission of multiple MFSK data streams, is one basic reference scheme for underwater acoustic communications due to low-complexity incoherent processing at the receiver and ease of implementation. In this paper, we provide some further results for multicarrier MFSK based on the recent development of coherent orthogonal frequency division multiplexing (OFDM) schemes. Specifically, we adopt an OFDM based representation, develop a residual Doppler shift compensation approach at the receiver, and present different ways of computing the soft likelihood information for multicarrier MFSK transmissions in combination with nonbinary channel coding. As compared with coherent OFDM, simulation and semi-experimental results show that multicarrier MFSK has consistent performance in channels with different numbers of paths and in environments with different types of external noise.