Adaptive modulation and coding based on virtual HARQ for satellite wireless communications

This paper aims to propose a virtual hybrid auto repeat request (HARQ) mode, as well as corresponding adaptive modulation and coding (AMC) method for geostationary earth orbit (GEO) satellite mobile communication systems. The virtual HARQ needs to predict the times of retransmission and transmit all the messages including the original message and retransmission messages in one transmission time interval (TTI). The AMC algorithm is based on current channel capacity which can be estimated by average mutual information (AMI) per resource particle. In this paper, we also propose a method to reduce the number of feedback bits. In this method, we use dynamic threshold to select the channel quality indicator (CQI). Simulation results show that the virtual HARQ mode and the corresponding AMC method can dramatically improve the spectrum efficiency and ensure the reliability of satellite wireless communication systems. Furthermore, the dynamic threshold method can reduce the number of feedback bits without degrading system performance.