Application of efficient importance sampling method to the simulation of digital satellite links

The authors consider the estimation of symbol error rate (SER) for digital signals transmitted through a satellite channel with a memoryless bandpass nonlinearity, typically an on-board TWT (traveling-wavetube) amplifier in a satellite repeater, when the noise at the input of a nonlinear element is nonnegligible. An improved method of importance sampling is used for SER estimation in a simulation model of a nonlinear satellite channel. The characteristics of the simulation model are as follows: the modulation can generate an MPSK or MQAM signal; at the inputs of the transponder and the receiver Butterworth or Gauss filters are used; the receiver utilizes a device for optimum phase shift of the carrier; and signal sampling is performed at the optimal moment during the signaling period. This model is also used for the analysis of the influence of other system parameters (e.g. filter type, kind of modulation, and backoff) on the quality of signal transmission. Simulation results are presented.