| With the increasing demand for communication services,low-orbit satellite networks have been widely used due to their advantages of small communication delay,high transmission bandwidth,low transmission power consumption,miniaturization of terminals,flexible deployment and global coverage of communication.An important part of the integrated airspace-ground network.However,the dynamic nature of the LEO satellite network topology,the uneven on-board load,and the location constraints of the ground stations bring huge challenges to the LEO satellite load balancing and affect the communication performance of the overall system.For the above problems,this paper analyzes the different flow characteristics of inter-satellite traffic and satellite-to-ground traffic in the whole network in the low-orbit satellite network,and studies the multi-path load balancing algorithm for the inter-satellite traffic flow characteristics and the satellite-to-ground traffic flow characteristics respectively.The main research contents of this paper are as follows:(1)Aiming at the problem of mesh flow characteristics and the large delay difference of multiple transmission paths during inter-satellite traffic transmission,this paper proposes a symmetric-link load balancing routing algorithm.First,design a symmetric link with a small transmission path delay difference,which allows multiple transmission links to be coupled at the low-load link,and reduces the delay difference of data transmission on different paths as much as possible.Disjoint links are used to transmit data to balance traffic distribution;secondly,a link state perception mechanism is introduced to expand the perception field of the source node,so that the source node can obtain the link quality parameters of the entire transmission path and distribute traffic for the source satellite node Sufficient decision information is provided;finally,a flow distribution mechanism based on packet scheduling is adopted,which comprehensively considers the load status and endto-end delay information of multiple transmission links,and allocates packets to the optimal link.Through simulation experiments on OPNET and STK platforms,this algorithm can effectively improve the utilization of network links,reduce the average endto-end delay of data packet transmission,reduce the out-of-order behavior of data packets at the receiving end,and improve the network performance.(2)Aiming at the characteristics of tree-like flow concentrated to ground stations during satellite-to-ground traffic transmission,and under the condition that the number of ground stations is limited and the deployment location is restricted,this paper proposes a load balancing routing algorithm based on topology balancing tree.First,build a topology balance tree,consider the load of each satellite node when calculating the routing table,adjust the next hop return node of the satellite node,and establish a topology balance tree without changing the backhaul distance from the satellite node to the ground station.It can take into account the traffic distribution between satellites while calculating the shortest path;secondly,a network state awareness mechanism is established based on the topology equilibrium tree,each satellite node exchanges information with its neighbor nodes,and establishes a local information base to provide the offloading mechanism for the offloading mechanism.information and load information;finally,a traffic distribution mechanism is established based on the topology balancing tree,and the optimal shunting node is selected among the shunting nodes and the proportion of forwarded traffic is determined to further balance the load in the network and generate a load balancing tree.Through simulation experiments on the OPNET and STK platforms,the topology balancing tree and the load balancing tree can balance the load in the network to different degrees,optimize the problem of unbalanced distribution of satellite-to-ground traffic,and improve the throughput of satellite-to-ground traffic transmission.The average end-to-end delay of data transmission is reduced. |
