HARQ and Adaptive TTI Bundling for Low Earth Orbit Satellite Voice Communication

To satisfy the low delay and frame error rate (FER) requirements of low earth orbit satellite (LEOs) voice communication, this paper compares the performance of HARQ and TTI Bundling. The maximum number of retransmission and the maximum number of transmission processes are calculated according to the characteristics of LEOs communication. Moreover, we propose an adaptive TTI Bundling scheme to cope with the changing environment of LEOs channels. The simulation results of the transmission performance are presented for three schemes. The simulation results show that TTI Bundling scheme has at least 3dB gain than HARQ scheme as for FER performance and throughput performance, and adaptive TTI Bundling outperforms fixed TTI Bundling. On the other hand, we also find HARQ scheme is more suitable for LEOs communication for high signal-noise ratio (SNR) condition while adaptive TTI Bundling should be used for low SNR condition.