Optimal satellite data downloading to multiple ESs by ISL offloading in LEO satellite networks

For those satellites in low earth orbit(LEO) satellite networks, due to limited storage capacity and other factors, an important task is to download their data collected in the space to earth stations (ESs). To maximize the throughput of data downloading from satellite to ESs, thus far, the existing research work has extensively studied how to efficiently allocate download time of ESs to satellites. However, a considerable part of satellites have barely contact time with ESs, because of the uneven contact between satellites and ESs.In this paper, we aim at optimizing data downloading from satellites to multiple ESs by using our inter-satellite link(ISL) routing method to offload data from the satellites that have surplus data to the satellites that have surplus contact time with ESs. First the entire satellite operation period is divided into several time intervals, a time interval is a time unit of data transmission. Then we allocate the download time between satellites and ESs. Lastly, the topology of satellites is modeled as Twisted Manhattan topology and our offloading algorithm is proposed to offload data among the satellites. Extensive simulations have been conducted to evaluate the effectiveness of our proposed scheme. The simulation results show that our scheme can significantly increase the overall system throughput of data downloading.