Research on bidirectional equalization in PDS system for under-water acoustic communication

Virtual time reversal mirror(VTRM) leads to spatial focusing and adaptive channel equalization.When VTRM is applied to pattern time delay shift coding(PDS) system for underwater acoustic communication,the system is called VTRM-PDS system,and so the system has the ability of resisting multipath interference.But when the communication nodes have slow movement,the channel is time-variant,and so in a frame of signal,the channel equalization effect will decrease with the time and mismatch will happen.Bidirectional equalization scheme is proposed in the paper.The scheme can adequately use detection signal and channel information and increase channel equalization effect by for-ward and backward equalization without study of channel.The lake trial results prove the superiority of bidirectional equalization scheme.