Space DTN Transmission Strategy Optimization Research Based On BP/LTP Protocols

With the launch of "Luna1" by the Soviet Union in1950s, human hasentered a new stage of deep space exploration. In the21st century, because of therapid development of space-related technology and needs in economy, politicsand military, many countries have proposed massive exploration programs, suchas the "Curiosity" of United States,"Chang’e II" of China and so on. At the sametime, with the increase of transmission data volume, astral observation time andtypes of services, future deep space communication need to be able to providelarge data, all-time and mult-types data exchange service. Based on thecomplicated and challenged deep space communication environment, taking theInternet on ground as reference, the conception of Interplanetary Internet (IPN)emerged.A prefect protocol architecture is the necessary guarantee for successfuldata exchange between nodes in network. The characteristic of deep space links,such as long delay, intermittent connectivity, high error rate and asymmetry ofup/down links, makes traditional TCP/IP protocols unfeasible. Now there aremainly three kinds of Interplanetary Internet protocols: space IP protocols,CCSDS protocols and Delay/Disruption Tolerant Network Protocols (DTN).Although space IP and CCSDS protocols have revised and improved someaspects according to the link’s characteristic, there are still some defects. DTNprotocols take the design ideas of Space IP and CCSDS protocols as referemce,achieveing interconnection between different subnets through bundle layer. BPand LTP protocals can deal with data transmission problems in such harshenvironment basically. However, frequent interruption and dismatch ofavailable time and transmission capacity of the links often cause largetransmission delay in the network and inefficiency usage of resources. To solvethis problem, data transmission optimization strategy based on fragmentation isproposed in this paper.This paper focuses on DTN protocol architecture application in deep spacecommunications. Firstly, we analyze the characteristics and mechanisms of BPand LTP protocols, completing data transmission tast. Through the analysis ofdata transfer process in deep space DTN environment, we find the currentversion DTN ensures reliable transmission at the expense of some transmissionopportunities, and the dismatch of available time and transmission capacity ofthe links exacerbate it. We propose a data transmission optimization strategybased on fragmentation, build non-exhaustive queuing model with vacation to analyze transmission delay and the storage space occupation, and modify theprotocols. Finally, we build build Earth-to-Mars communication scenario throughOpportunistic Network Environment (ONE). Messages are created in Mars roveron the surface of Mars, relayed through Mars relay satellite, Moon relay satellite,Earth relay satellite, and reach the ground receiving station hop-by-hop.Simulation is done based on the transmission optimization strategy, comparedwith the current protocols. Simulation results show that transmission strategybased on fragmentation can improve the message delivery probability and reducethe transmission delay. And the influence of node storage, message size, andthe TTL is discusseed. Through this research, we hope provide some referencefor future interplanetary Internet protocol design and network infrastructurebuilding.