No abstract

Phase noise causes significant degradation of the performance of a high order quadrature amplitude modulation (QAM) system in conjunction with a n Orthogonal Frequency Division Multiplexing (OFDM) procedure. Moreover, a n OFDM signal has a non constant envelope with large instantaneous amplitude peaks and there will be a need to limit these large variations of the signal. This paper describes a model for oscillator phase noise distortion due to the receiver tuner a n d presents some expressions for amplitude clipping introduced by the nonlinear high power amplifier in the hansmitter and by the automatic gain control in the receiver. Our simulations show the influences on an uncoded and on a trellis-coded system for transmitting Digital High-Definition Television (ITDTV) signals.

Multilevel C o d e d Modulation is a special case of Coded Modulation. It has been proposed by Imai at nearly the same time as the Trellis-Coded modulation by Ungerboeck. A sequence of subsets is coded w i t h variable rate using block and/or convolutional codes in contrast to the Trellis-Coded Modulation based on rate F. In this paper w e focus on Multilevel Codes w i t h p u n c t u r e d convolutional eodes for Digital Video Broadcasting.