Low Complexity OFDM Detector for Underwater Acoustic Channels

An adaptive algorithm is proposed for OFDM signal detection on Doppler-distorted, time-varying multipath channels. The focus of the approach is on low complexity post-FFT signal processing. The receiver performs MMSE combining of signals received across an array, using adaptive channel estimation. Non-uniform Doppler compensation across subbands is performed using a single adaptively estimated parameter representing the Doppler rate. Algorithm performance is demonstrated on experimental data, transmitted through a shallow water channel over the distance of 2.5 km. QPSK modulation with a varying number of carriers is used in a 24 kHz acoustic bandwidth. Excellent performance is achieved with up to 1024 carriers, yielding an overall bit rate of 30 kbps