Research On Multi-layer Satellite Network Routing Strategy Based On Grouping Management

As an important part of modern communications,satellite communications are receiving more and more attention.The multi-layer satellite communications network with diverse functions,flexible networking and strong invulnerability is focus of satellite communications research.Due to the continuous movement of the satellites,the whole satellite network' structure is dynamic.The existing routing algorithms for terrestrial network can't adapt well to such changes.In order to ensure efficient transmission of data,it is necessary to design a new routing strategy.In this paper,the routing algorithm of LEO/MEO/GEO three-layer satellite network is studied.The specific research contents and results are as fellow.The topology changes of multi-layer satellite network are very intense.Not only the interstellar links between the satellites in the same layer are constantly switched,but the interstellar links between the low orbit satellites and middle orbit satellites,middle orbit satellites and high orbit satellites are also subject to periodic changes in the relative motion between layers.As an effective topology management strategy,grouping management is widely used in the research of multi-layer satellite network routing algorithms.However,the strategies of group manager selection and group switching will affect the time-slot division.In the previous study,there was no detailed description to these effects.In this paper,by calculating the connectivity of inter-layer satellites,the division of time-slot under the different selection strategies of managers is obtained.The results show that group manager selection method with “the longest covering time” has better attributes of time-slot.The number of time slots generated by the group manager selection method based on "the longest covering time" is relatively small,but the number of time-slot is still more than 1600,and the average length of each time-slot is only 50 seconds.In this paper,according to the characteristics of group manager selection method,the time-slot division of the intra layer satellite is calculated jointly,which greatly reduces the number of time-slots,improves the average length of the time-slot,and provides the guarantee for the routing stability.When the group manager calculates the shortest path for the members of the group,the overall network topology is regarded as a weighted directed graph,and the shortest path is obtained by using algorithms such as Dijkstra and Floyd.Although the optimal solution can be obtained in this way,the overall computational load is very large,and as the number of satellites increases in the network,the amount of calculation will increase rapidly,which is not conducive to network expansion.In this paper,according to the time delay and topological characteristics,the network topology is transformed into a directed acyclic graph,and the shortest delay path is calculated based on topological sort,which can reduce the overall computational complexity greatly.The simulation results show that the optimized computation method is very close to the optimal results in terms of delay and throughput.