Adaptive Equalization In High Speed Underwater Acoustic Communication System

Underwater acoustic communications are made difficult by the effect of multipath propagation. The fading which was caused by multipath propagation was one of the main factors influencing the performance of underwater acoustic communication systems. Adaptive equalizer is a very effective technology that can overcome Inter-Symbol Interference caused by multipath propagation. LMS (Least Mean Squares) and RLS (Recursive Least Squares) algorithm are two basic algorithms of adaptive filter. LMS algorithm with fixed step contradicts with the demand of parameter μ in aspect of the rate of convergence and track speed of real time system and the precision of convergence. The expert seek many LMS algorithms with variable step. RLS algorithm contain some intrinsic defects, so the scholar put forward some improved RLS algorithms. Adaptive equalizer has become focus in the field of communication.Firstly, the properties of underwater acoustic channels is analyzed and the model of underwater acoustic channels has been found. Then, the thesis compares several LMS algorithm with variable step put forward by Jing fan Tan,Gao ying,San yuan Sheng,Huai guo Liu and so on and some improved RLS algorithm such as SPRLS,MRLS and ISPRLS algorithm. Different convergence of LMS and RLS algorithm aboved is analysed with different multipath channel, right and parameter.The DSP system for adaptive equalizer is designed including hardware and software. Finally, The experiment of adaptive equalizer which used many LMS and RLS algorithms has been taken. It proved that adaptive equalizer can overcome Inter-Symbol Interference caused by multipath propagation and improve the quality of communication and decrease the rate of missing code.