Research On Blind Equalization Technology And Its Application In Acoustic Communication System

The inter-symbol interference (ISI) caused by the multi-path propagation is a main obstacle in the field of underwater acoustic communication. Channel equalization technology is an effective method to combat ISI. Because of needing repeatedly training sequence , the traditional adaptive equalization technology has a lower performance. The blind equalization technology that only uses received sequence without the aid of any training sequence can effectively combat ISI and advance the performance of an acoustic communication system. Therefore, this dissertation investigates the application of blind equalization technology in an acoustic communication system.The research work of the dissertation includes the following two parts: researching blind equalization technology and developing hardware and software of the verification platform.The main work of the first part includes: presenting the Bussgang blind equalization algorithms according to the mathematics model of blind equalization. The constant modules algorithm (CMA) is a well-known Bussgang blind equalization algorithm. This part analyzes the initialization and step-size's effect on the convergence performance of CMA in detail, modifies the CMA according to the effect, and then applies variable step-size theory to CMA. The simulation result has proven the improvement algorithm in the convergence rate and the equalization performance validity.The main work of the second part includes: analyzing the task and the requirements of the verification platform, and presenting the idea how to design the verification platform efficiently. The platform hardware includes two modules: analog module and digital module. They are isolated by a high-linearity analog optocouplers, in order to reduce the effect on analog module caused by digital module, because analog module is sensitive to noise. The digital module is constructed of digital signal processor (DSP) that acts as the core, field programmable gate array that acts as the logic controller, NAND flash which acts as the data memory, an ADC, a DAC and other needed peripheral. This design uses Ping-Pang cache to improve data ratio in data accessing. The platform software uses modular design. It is easy to add or delete some features. This mechanism ensures the platform's versatility and reliability.Testing in laboratory and carrying out a field experiment on the verification platform show that the performance of the platform and the algorithm are good enough.