| This paper researches blind equalization algotithm of Bussgang family in wireless communication system,whose performance are measured by the convergent rate and residual intersymbol interference(ISI).This paper firstly introduces the process on putting forward blind equalization, how to classify equalization as well as the knowledge on channel equalization. The most typical one is constant modulus algorithm (CMA) among Bussgang family suitable for QAM equalization.Although the CMA has the simple iterative formula, it still fails to deal with the slow convergent rate and high residual ISI in the time-varying multipath fading wireless channels as well as the phase rotation in the channel with the carrier rotation. With the MCMA(Modified CMA) being proposed, this shortcoming is settled so that it's unnecessary to use equipment for phase restoration. The dual mode in which Decision-Directed mode is applied when error between output of blind equalization and ideal value is reasonably low is another method to reduce ISI.In the above analysis, the space of tap weight in the blind equalizer is equal to baud rate. The baud space equalization(BSE) only can compensate for aliasing frequent response in the receiving signal, rather than inherent aberrance in the channel due to the space of weight tap which is less than Nyquist sampling rate. When the space is the fraction of code rate in the equalization, this default is overcome. That calls fractional space equalization(FSE). My paper takes the fractional space MCMA as the example to analyse fractional space blind equalization.The simulative results show FSE-MCMA not only overcomes multipath propagation and frequency selective fading resulting from wireless channel, but produces the smaller residual ISI than CMA,MCMA as well as DMCMA..But it bring on disadvantage of relative slower convergent rate.So that it can be said that fractional space MCMA is the best algorithm among them. The result is... |
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