| Digital communication has been widely used because of its many advantages, and with the development of integrated circuit and compute technology, it is sure that digital communication will be developed with the much more fast and reliable direction. Toward digital communication, bit error and spectrum availability ratio are two main scale targets. Owing to non-ideal normal channel, serious Inter-Symbol Interference(ISI) is generated after the digital signal being transmitted, which is a very disadvantage for correct decision, sequentially communication bit error is increased. Which is not expected and measures should be taken to solve this problem.Adaptive equalization, from its bringing forward to now, has been widely employed because of its good performance. This paper simply discusses the cause of generating Inter-Symbol Interference based on normal communication channel study. Frequently used equalizer architectures are studied, and computer simulation are made and analyzed for these architectures. Advantages and disadvantages of kinds of available normal algorithms are compared and analyzed, then a new modified LMS algorithm is proposed. The modified algorithm is analyzed in theory, the performance of modified LMS and LMS algorithm are compared, then computer simulation are made and analyzed for this modified LMS algorithm. This modified LMS algorithm has good convergence and track performance since present error signal is used to evaluate next recursive step size. Generally speaking, there are correlations among input signal vectors, A modified CMA is put forward using this kind of correlation, modified CMA and CMA are compared and computer simulation are made and analyzed. The simulation shows that the modified CMA convergent rate is about twice as fast as CMA convergent rate. As well, this paper shows some instructional methods and ideas on how to select an adaptive algorithm in the course of designing an adaptive equalizer in the practical digital communication system. |
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