| Summary: | 碩士 === 輔仁大學 === 電子工程學系 === 98 === This work studies the effect of additive channel noise on the steady-state performance as well as on the transient performance of both the fractionally spaced equalizers (FSE) adapted via the constant modulus algorithm (CMA) (or FSE-CMA) and the FSE adapted via the multimodulus algorithm (MMA) (or FSE-MMA) when various symmetric two-dimensional signal constellations are employed. The main results of this work are three-fold. First, the CMA is less sensitive to channel noise than the MMA for all possible sources, which gives the CMA an advantage over the MMA in the presence of large channel noise. Second, an estimate of error surface curvatures at the stationary points by using the CMA and the MMA in the presence of channel noise has been explicitly derived. The derived curvatures decrease as signal-to-noise ratio (SNR) decreases, thus decreasing the convergence speed of CMA and MMA. Thirdly, the MMA used with source constellations with favorable equalization convergence and carrier phase tracking in the absence of noise (such as 4-PSK) is especially vulnerable to channel noise. However, the MMA still outperforms the CMA in terms of equalization convergence and carrier phase recovery when noise is present, though this advantage associated with the MMA becomes less evident as SNR decreases.
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