A Factor-Graph Based ZP-OFDM Receiver for Deep Water Acoustic Channels
In this paper, the authors present a factor-graph based receiver for Zero-Padded Orthogonal Frequency Division Multiplexing (ZP-OFDM) transmissions over deep water channels with extremely long delay spreads. Due to the geometric structure of deep oceans, the channel delay spread between the direct paths and surface/bottom reflections can be on the order of hundreds of milliseconds, which is usually several times larger than the ZP-OFDM block duration, leading to severe InterBlock-Interference (IBI). Channel time variation also introduces Inter-Carrier-Interference (ICI). The proposed receiver addresses both IBI and ICI in a unified factor-graph representation.