Research On Mechanisms And Methods Of Space Routing For Satellite-Terrestrial Identifier Network

The Satellite-Terrestrial Identifier Network is a novel network architecture designed for future satellite terrestrial integrated network.It can interconnect the heterogeneous space network with terrestrial identifier network and solve the mobility,security,scalability problems simultaneously.The DTN(Delay/Disruption Tolerant Network)protocol is adopted by Satellite-Terrestrial Identifier Network to handle the long propagation delay,high bit errors and frequent link disruption problems in space environment.As part of Satellite-Terrestrial Identifier Network architecture,targeting at implementing the routing schemes in space network,this thesis mainly focuses on the contact plan design and the inter-layer contact selection for space core network,the contact quality aware routing and maximum transferable data model for space access network,the routing reliability enhancement and the congestion control for space network.The main contributions of the thesis are as follows:1.A distributed contact plan design scheme for multi-layer satellite network and two dynamic inter-layer contact selection algorithms are proposed to cope with the complex contact plan and frequent link disruption problems in space core network.Firstly,the distributed contact plan design scheme can reduce the contact plan complexity and further reduce the computing delay by dividing the complete contact information into several partial parts according to the satellite layers.Secondly,the dynamic inter-layer contact selection algorithms include the duration based inter-layer contact selection algorithm and the traffic aware inter-layer contact selection algorithm.They select the appropriate inter-layer contact by considering the contact duration and the flow distribution respectively and update the contact plan dynamically to deal with the frequent link disruption as well as avoid network congestion.Finally,the Satellite-Terrestrial Identifier Network test-bed is produced using 95 virtual nodes to evaluate the performance of the distributed contact plan design scheme and the inter-layer contact selection algorithms.Numerous experimental results show that the distributed contact plan design scheme can reduce the data delivery delay.The traffic aware inter-layer contact selection algorithm can achieve a balanced flow distribution and improve the data delivery ratio.2.A contact quality aware routing and a maximum transferable data model are proposed to cope with the impact of different link bit errors on data transmission in space access network.Firstly,the contact quality aware routing uses the number of link retransmission signals to reflect the link bit errors and adopts a contact quality based forwarding scheme to select a path with lower bit errors.Secondly,a dynamic retransmission timer setting scheme for LTP(Licklider Transmission Protocol)is proposed to avoid the unnecessary data retransmission.Based on the retransmission timer setting scheme,the maximum transferable data model which considers the influence of bit errors and asymmetric channel rate is proposed.It can provide a theoretical model for data transfer missions in space network.The proposed algorithm and model are verified using the test-bed.Numerous experimental results show that the contact quality aware routing can reduce the data delivery delay and improve the data delivery ratio.The proposed model is consistent with the experimental results.3.A routing reliability enhancement algorithm is proposed to cope with the unpredictable contact disruption problem caused by the node failure or electromagnetic interference in space network.The algorithm consists of three mechanisms including the contact disruption detection mechanism,the contact recovery detection and notification mechanism,and the forwarding mechanism considering the contact disruption state.It can exclude the disrupted contact out of the delivery path by adopting the three mechanisms.Meanwhile,in order to avoid the lower survival time data being dropped caused by the queue delay,a utility based forwarding mechanism is proposed to improve the delivery priority of these data.It can further improve the routing reliability.Numerous experimental results show that the routing reliability enhancement algorithm can improve the data delivery ratio and reduce the data delivery delay.The utility based forwarding scheme can improve the delivery ratio.4.A QoS based congestion control algorithm is proposed to cope with the network congestion caused by the insufficient of contact capacity and node storage.The algorithm consists of the contact congestion forecasting scheme and the QoS based data forwarding scheme.The contacts are divided into different congestion levels according to their residual available capacity and node storage resource.The congestion level of the forwarding path is decided by the highest congestion level of the contacts consisted in the path and different priority data will be forwarded according to the path congestion level.Numerous experimental results show that the QoS based congestion control algorithm can improve the delivery ratio of the data with lower priority and reduce the delivery delay of the data with highest priority.