Research On An Efficient And Reliable Transmission Scheme For Space DTN

The characteristic of delay/disruption tolerant networking(DTN)that can work under the transmission conditions including the long propagation delay,frequent link disruptions,channel-rate asymmetry,etc.,enables it to meet the challenges that characterize satellite communications and space internetworking.There are many ways existing in DTN which can guarantee the reliable data delivery,such as Automatic Repeat reQuest(ARQ),error control coding(ECC)by link layer.However,their transmission efficiency will be greatly reduced under harsh space transmission conditions which result in high loss of data or many error receiving packets.With the continuous progress in space technology,the space activities of human being are becoming more and more frequent,bringing higher demand for communication ability and stability in space environment.Therefore,it's vital to consider an appropriate transmission scheme to ensure efficient and reliable data transmission in space information network.This paper first presents an in-depth review of the current development and data transmission mode of space DTN.Based on this,in order to improve the transmission efficiency and without changing the overlay networking architecture of DTN,this paper proposes a hybrid reliable transmission scheme combining the application layer channel coding and ARQ mechanism.On the one hand,the retransmission rounds can be decreased due to the ability of the channel error correcting coding.Meanwhile,with the help of ARQ mechanism,the hybrid scheme can also get enough data packets for decoding under the severe channel conditions.On the other hand,the proposed hybrid scheme plays a role in the application layer,without changing the overlay networking architecture of DTN,which enables the co-existence of the heterogeneous transmission protocols.Then,based on ION-DTN open source protocol software,this paper designs and implements the hybrid transmission scheme.The file transmission time of the hybrid transmission scheme is analyzed in theory firstly.Then the experiment for comparing the hybrid transmission scheme and the ARQ scheme which bases on LTP protocol is designed for different transmission delays,error rates and file size.The simulation results show that the proposed hybrid scheme can improve the efficiency of reliable transmission in DTN.Compared with the simple ARQ mechanism,when the channel condition gets worse,the hybrid transmission scheme will take shorter and more efficient transmission.Finally,the advantage of the application of erasure codes in space network,especially in deep space environment is pointed out.