Design And Simulated Implementation Of Hierarchical Routing For Integrated Space/Air Information Networks Based On DTN

Satellite communication networks in space regions and aircraft communication networks in air regions are mutually independent of each other at present.Nodes in different kinds of networks cannot realize the direct information interaction.This results in the waste of resources and the lack of QoS(Quality of Service)to support the comprehensive application on various aerospace communication platforms.Especially nowadays,military satellites become more and more important for combat aircraft communication networks in the operational system based on information supporting.An effective mean of solving this problem is the construction of the integrated space/air information network,in order to make these heterogeneous regional networks interconnected and interoperating.The integrated space/air information network is a convergence of satellite communication networks in space regions and stratospheric communication networks including aircrafts in air regions so that it can support the direct internal information interactions.With the extensive application of the integrated space/air information network,its routing problem becomes a key research point.With the emergence of the concept of Delay-Tolerant Network(DTN)that is the network architecture designed to operate effectively as an overlay on top of regional networks,the integrated network can own its generalized routing protocol-Bundle protocol,which can tolerate the long delay and intermittent connectivity.However,the existing DTN routing algorithms are mainly designed for the space or air region separately,and there is little study on the generalized hierarchical routing algorithm to realize the communication between space and air regions.In this thesis,a Hybrid time-space Graph based Hierarchical Routing(HGHR)scheme is proposed for this heterogeneous network.The hybrid time-space graph includes two subgraphs:a deterministic one and a semi-deterministic one.As satellite orbits are pre-known in the space region,a deterministic time-space subgraph is introduced.On the other hand,since each aircraft has a cyclic movement with the predictable contact probability and contact time in the air region,a semi-deterministic time-space subgraph is constructed.Especially,to build the semi-deterministic time-space subgraph,we introduce a discrete time homogeneous semi-Markov prediction model to predict the contact probability and contact time for each pair of aircrafts in the air region.This hybrid time-space graph is transformed into the state-space graph for easy route query,where the time dimension is removed from edges.Using this state-space graph,a forwarding rule is defined for relay nodes in the integrated space/air information network,in order to achieve the HGHR.Simulation results demonstrate that HGHR has good performances in terms of data delivery ratio and end-to-end delay.