The Study On Variable Step Size Blind Equlization Algorithm

Blind equalization is a self-adaptive equalization technology. It doesn't need referring to a training sequence to maintain normal work, only utilizes the prior information of transmitted signals to equalize the channel character. So in the digital communication system a training sequence isn't transmitted, which can raise the channel's efficiency. However blind equalization may get much better equalization ability at the same time. The super performance of blind equalization makes it be noticed widely and be used in many fields such as digital communication system , radar system , earthquake and image processing system and so on.The major contribution of this paper is summarized as follow-.(1) This paper systematically analyses and summarizes the basic theory of blind equalization such as equalization criterion, algorithm form, performance parameter. CMA algorithm of Bussgang algorithms is the emphasis.(2) This paper analyses the convergence performance of the traditional CMA algorithm. The fixed step size of the traditional CMA algorithm makes convergence speed and residual error become a contradiction, which makes the application fields of CMAalgorithm limited. In order to solute the contradiction this paper derives CMA blind equalization algorithms that adopt the variable step size but the fixed step size.(3) This paper derives an improved CMA blind equalization algorithm utilizing the vary of MSE. The simulation with computer shows the improved algorithms have the better convergence performance than CMA algorithm.(4) This paper derives an improved CMA blind equalization algorithm basing on the power of the equalizer's output signal. The simulation with computer shows the improved algorithms have better convergence performance than CMA algorithm.