Comparison of digital modulations for mobile satellite channels

Abstract

Computer simulation is used to compare the performance of several modulation formats for digital communication for mobile satellite channels. The simulation accounts for such variables as transmit and receive filtering, travelling wave tube non-linearity and uplink noise. A two-ray channel model is used to represent multiple path fading, with the relative phase of the reflected ray is assumed to be uniformly distributed. Initially an expression of the conditional probability of error for different modulation techniques are derived in an integral form. It is shown that the averaging over multipath parameters however is analytically formidable, and numerical integration or computer simulation are required to obtain reasonable results. Simulation results are then presented for several modulations using the bit error probability as a measure of performance.