Matching pursuits channel estimation for an underwater acoustic OFDM modem

Sparse channel estimation algorithms are proposed for underwater acoustic Orthogonal Frequency Division Multiplexing (OFDM) communications in time-varying multipath channels. Following carrier frequency offset (CFO) correction, the proposed algorithms first extract the portion of the time domain signal corresponding to pilot symbols. The Matching Pursuit (MP) algorithm is then applied to channel estimation. Performance of the proposed receiver is evaluated in simulations and in underwater field tests. Experiments in shallow water show that a BER on the order of 10^-3 is achievable at 330 m distance for uncoded data transmission. Experimental results with LDPC-coded transmission are also presented showing zero BER at 330 m.