Performance of iterative OFDM receiver in doubly spread underwater acoustic communication channel

Underwater acoustic communication (UAC) channel is a typical doubly spread channel with large multipath delay spread and large Doppler spread. The large multipath delay spread will lead the severe inter symbol interference (ISI) in the single carrier communication systems. The usual ISI will affect as much as hundreds of symbols, which will need complex equalization. OFDM can effectively reduce the ISI with guard interval. However due to the slow speed of acoustic propagation (about 1500m/s), the slow movement of underwater sensor nodes caused by ocean current will lead large Doppler spread, which will lead severe inter carrier interference (ICI). Channel estimation in this doubly spread channel will encounter the problem that the channel state information of pilot is affected by the neighboring unknown data symbols, which will largely degrade the performance of OFDM system. The paper studies the iterative OFDM receiver to reduce the performance degradation caused by the ICI.