Research On Optimization Of Data Transmission In Navigation Information Network

As a national important space infrastructure,satellite navigation system provides global users with all-weather,all-day,high-precision positioning,navigation and timing services.It has penetrated into all aspects of human society production and people's lives,and injected new energy into global economic and social development.With the higher demand for navigation and location service accuracy,the use of low-orbit satellites for real-time high-precision navigation enhancement has become the next development trend and has broad development prospects.Whether in the navigation satellite network of the satellite navigation system or the low-orbit enhanced network of the low-orbit satellite navigation enhancement system,ensuring the efficient transmission of navigation information is a prerequisite for realizing its function.Based on the development status and future development requirements of China's satellite navigation system,this paper studies the optimization of data transmission performance of navigation information network,including the inter-satellite link planning and routing algorithm optimization research of the current navigation satellite system,and the satellite-ground link planning and routing algorithms research of the future navigation enhancement system.The navigation satellite network is composed of medium-orbit satellites.The inter-satellite link is based on the time-division system of phased array antennas.The inter-satellite ranging and information transmission are completed through link switching between different time slots and different satellites.The data transmission mode is similar with“storage-carry-forward”mode in delay tolerant network.The loworbit enhanced network consists of low-orbit satellites,and the inter-satellite links remain continuously connected,so the network topology is fixed.However,the satellite-ground links are frequently switched.For the above two research objects,the main research contents of this paper include:(1)Navigation satellite network inter-satellite link planning algorithmThe problem of navigation satellite network inter-satellite link planning solves the problem of which satellite is chained to each satellite in each time slot,and is the basis of navigation data transmission.The inter-satellite link of the navigation satellite network has both the functions of ranging and communication,and the link planning needs to consider them at the same time.In this paper,the maximum matching of the bipartite graph and the maximum matching theory of the general graph are used to solve the intersatellite link assignment problem.The transmission delay of the satellite is reduced as much as possible.As well,the ranging performance is improved by ensuring all visible satellites are mutually chained.Through the combination of the two schemes,both the inter-satellite communication and the inter-satellite ranging performance are considered.In addition,this paper also theoretically discusses the problem of the number of visual matrix splits and the relationship between the PDOP and the number of inter-satellite links.(2)Navigation satellite network routing algorithmThe navigation satellite network routing problem solves the problem that with which route the data is transmitted can reach the destination as soon as possible.Since the intersatellite link has a short communication time in each time slot,and the inter-satellite link has a limited bandwidth,so the amount of information that can be transmitted in each time slot is small.The data to be transmitted often needs to be divided into multiple segments,and each segment is transmitted independently,and then stitched together after reaching the destination node.Multi-segment transmission of data increases the complexity of data transmission in a navigation satellite network.In this context,this paper proposes a hoplimited data transmission problem and a multi-segment information broadcasting problem for two typical application scenarios of navigation satellite networks.The construction protocol proves that the hop-limited information transmission problem is an NPC problem.It is proved that the problem can be judged in polynomial time under two specific conditions.Aiming at the problem of multi-segment data broadcasting of satellite nodes,different information transmission strategies are proposed,and the theoretical model is established to calculate the time of broadcast completion.The simulation results prove that the theoretical model of this paper has higher accuracy.(3)Low-orbit enhanced network satellite-ground link planningThe low-orbit satellite has a low altitude,and the satellite-ground link is frequently switched.The problem of the satellite-ground link planning focuses on solving the problem of which satellite to select to establish a satellite-ground link to transmit information.We investigate it with respect to three aspects,namely,link switching frequency,routing update frequency,and relay satellite conguration.1)Link switching frequency.Link switching will bring additional system overhead,increase the failure rate caused by handover.So the number of switchovers must be minimized.2)When the satellite-ground link is switched,the relay satellites are changed,resulting in a change in the path between satellites and the ground station,which involves a certain amount of resource consumption.Because there are limited computing resources on the satellite,the number of link switches must be reduced as much as possible.3)Relay satellite conguration.The degree of aggregation of relay satellites directly affects the degree of congestion in data transmission between satellites.By reasonably selecting relay satellites,traffic can be maximized and dispersed in different areas of the network.This paper systematically proposes and analyzes the low-orbit enhanced network satellite-ground link planning problem,and proposes the optimal link planning scheme from above three aspects,and theoretically proves the optimality of the scheme.For the least number of link switching times,this paper proves the optimality by using the maximum service time algorithm and the minimum cost and maximum flow of the constructed graph.Finally,the simulation results further verify the optimality.(4)Low-orbit enhanced network routing algorithmThe low-orbit enhanced network data transmission routing problem solves the problem of data transmission path.In order to realize its navigation enhancement function,the low-orbit enhanced network needs to exchange large amounts of data in real time between the satellites and ground stations.All data needs to go through the relay satellites,which inevitably brings data on the inter-satellite links of the relay satellites.Inter-satellite links and satellite-ground links have limited bandwidth,and large amounts of data can easily cause congestion or even packet loss.Therefore,the low-orbit enhanced network data transmission routing problem needs to consider the network traffic balance to maximize the network throughput.This paper systematically proposes and describes the data transmission problem of low-orbit enhanced network,establishes a linear programming model,and then obtains the optimal solution model.Based on the principle of maximum matching of weighted bipartite graphs,a routing algorithm based on node assignment and topology control is proposed to ensure the traffic balance of data in the network and maximize the throughput of the network.Its performance is close to the optimal performance of linear programming model,but the computational complexity is much lower than the latter.