Modulation Index Selection Strategy for Quasi-Constant Envelope OFDM Satellite System

Satellite communication is an important part of communication networks. Since the energy and the spectral of satellite system are limited, the energy efficiency and the spectral efficiency become two key performance metrics. However, these two metrics always increase in an opposite way. Quasi-constant envelope OFDM technology can provide high data rate communication links and maintain the peak-to-average power ratio (PAPR) less than 3 dB. It provides a way to get balance between these two metrics and it is suitable for satellite communication system. As the phase modulation method is used in quasi-constant envelope OFDM technology, the energy efficiency and the spectral efficiency of the system are all related to the modulation index. Since a typical satellite communication system contains various types of services, the problem is how to choose the appropriate modulation index according to the demands and conditions of different users. In this paper, a system performance model is proposed and it considers the energy efficiency and the spectral efficiency as two factors. The modulation index selection strategy is to choose the appropriate modulation index to maximize the system performance. The relationship between these two factors and the modulation index are analyzed and the system performance curves are given through simulation.