Research On Collaborative Data Downloading By Using Inter-satellite Links In LEO Satellite Networks

Satellite systems have attracted great attention in the recent years.There are many satellites that have been launched for weather forecast,environment monitoring,and target surveillance.The companies benefied by NASA technology sharing,such as SpaceX,make the carrier rocket become cheaper and cheaper,and more and more satellites were launched into space.The Low Earth Orbit(LEO)Satellites are the most popular satellites for its low transmission delay.One important task of the satellites is to download the data they have collected in the space to the ground servers via Earth Stations(ESs).Since satellites move at high speed along their own orbits and have very limited contact time with ESs,satellites may not be able to download all the data they have to the ground on time.In this paper,we propose two collaborative schemes,”One-hop collaborative schemes downloading data algorithm” and ”Multi-hop collaborative schemes downloading data algorithm”,which allow satellites to transfer data among themselves using intersatellite links(ISLs)before they come to the contact with the ES,such that satellites will carry the right amount of data according to the length of their contact time with the ES and the throughput of data downloading at ES is maximized.In the ”One-hop collaborative schemes downloading data algorithm”,we only offload data from one satellite to its ”one-hop” satellites.For maximized the throughput of downloading,the ”One-hop collaborative schemes downloading data algorithm” develop an iterative optimization algorithm that jointly schedules data transfer among the satellites and data downloading from satellites to the ES.However,It will take use of ”Multi-hop” ISLs(Inter-satelliteslinks)for data offloading in ”Multi-hop” case.The ”high-hop” ISLs offloading may cause congestion,so we will optimize the cost of offloading at the same time.Extensive simulations have been conducted to evaluate the effectiveness of our proposed method.The simulation results show that the data downloading throughput by using ISL data transfer can be increased significantly.In ”One-hop” simulations,the throughput of data offloading can reach to 90%,and the ”Multi-hop” can reach higher.In many cases,the throughput reaches close to 100% of the capacity of the ES.