Channel Equalization Using Passive Time Reversal Mirror in Underwater Acoustic Communication

The shallow-water acoustic channel differs from radio channels in many aspects. Two fundamental mechanisms of multipath formation are reflection at the boundaries and ray bending, so the acoustic channels may have extremely long multipath spreads. In addition, the acoustic signals are subjected to temporal and spatial varying multipath channel, which may result in severe inter-symbol interference (ISI) for underwater acoustic communication. These characteristics restrict the range and bandwidth for reliable communications and lead a low data transfer rate. In order to mitigate the inter-symbol interference caused by multipath channel, single sensor passive time reversal mirror (PTRM) is introduced and applied to Pattern time delay shift coding scheme (PDS). Through the lake trial, the PTRM is shown to be a robust and effective approach for channel equalization in underwater acoustic communication.