Propagation delays computation in GEO multi-beam satellite communications system

In order to overcome delay-sensitive shortcoming of satellite communications system based on Time Division Duplex mode, a scheme of acquiring propagation delay of any place within a spot beam is proposed. It is accurately calculated by space geometric model according to the satellite position ranging results by three calibration stations. Based on actual system parameters in China, the influence on radio frame design and synchronization problem by using midpoint propagation delay as synchronization reference time instead of average propagation delay is analyzed. The result shows that this approximation can not only reduce the computational complexity, but also ensure the adaptability of TD-SCDMA radio frame structure in GEO satellite communications system.