EFFECT OF CARRIER RECOVERY AND SYMBOL TIMING RECOVERY ERROR ON THE PERFORMANCE OF 256-QAM SYSTEMS.

The effect of carrier-phase error and timing error on the performance of 256-state quadrature amplitude modulation (QAM) is investigated. Four types of timing error are considered such as static offset, sinusoidal deviation, uniform deviation and Gaussian distributed carrier phase errors. It is found that the performance is much more degraded in the presence of timing error as the roll-off factor of the raised-cosine filter decreases, whereas the roll-off factor does not affect the performance of the presence of carrier-phase error. It is shown that Gaussian-sampling deviation and Gaussian-distributed carrier-phase error cause the largest C/N degradation.