LTP Protocol Optimization Face To Error Channel Of Space

With the launch of Luna 1 by the Soviet Union in 1950 s, human has entered a new stage of deep space exploration. In the 21 st century, because of the rapid development of space-related technology and needs in economy, politics and military, many countries have proposed massive exploration program s, such as the "Curiosity" of United States, "Chang’e II" of China and so on. At the same time, with the increase of transmission data volume, astral observation time and types of services, future deep space communication need to be able to provide large data, all-time and mult-types data exchange service. Based on the complicated and challenged deep space communication environment, taking the Internet on ground as reference, the conception of Interplanetary Internet(IPN) emerged.A prefect protocol architecture is the necessary guarantee for successful data exchange between nodes in network. The characteristic of deep space links, such as long delay, intermittent connectivity, high error rate and asymmetry of up/down links, makes traditional TCP/IP protoco ls unfeasible. Now there are mainly 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 some aspects according to the link’s characteristic, there are still some defects. DTN protocols take the design ideas of Space IP and CCSDS protocols as referemce, achieveing interconnection between different subnets through bundle layer. BP and LTP protocals can deal with data transmission problems in such harsh environment basically. However, frequent interruption and dismatch of available time and transmission capacity of the links often cause large transmission delay in the network and inefficiency usage of resource s.This paper focuses on DTN protocol architecture application in deep space communications. Firstly, we analyze the characteristics and mechanisms of BP and LTP protocols, completing data transmission task. Secondly, through deep analysis of CGR protocals in the BP protocals and found that though the path found by current CGR protocal could ensure reliable transmission, the transmission efficiency is very low. So we analyze the process of segments transmission under all circumstances, based on the judgment st andard that is delivery time of bundle transmission, to design the optimal transmission strategy under various link conditions, thus as the criteria of CGR routing protocal to find transporting path. Then, due to the characteristics of extreme asymmetric u plink and downlink of deep space, the idea of bundle aggregation proposed to solve the difficulty of asymmetric links. We can combine it with CGR routing protocal, the path found by CGR would determine the aggregation size of bundle. Finally, using MATLAB to simulate the retransmission times of bundle transmission, used to calculate the bundle transmission delivery time. The comparison of the optimized bundle transmission delivery time and current bundle transmission time. And the performance improvement br ought by bundle aggregation, and analyzing the throughput of bundle aggregation in different BER conditions.