The Design And Implementation Of Protocol Conversion For Space Station Internet Access Gateway

Manned space flight project is the the largest and most complex national key project in space history of China, which has the highest technical difficulty and safety requirements. China's manned spacecraft development strategy can devide into three-step. After the space extravehicular activities of astronauts, the country will launch its own space laboratory, solving some short-term manned space problems, preparing for the future construction of the space station and astronauts'long-term garrision.At the beginning of the construction of International Space Station, Internet access issues were not taken into account. In order to satisfy the need for entertainment services and contaction with the ground of astronauts, it is necessary to test space station Internet access services using space laboratory.Based on this issue, advantages and disadvantages of applying TCP/IP protocol into space environment are analyzed in this paper. In addition,after comparison of many Internet access schemes for satellites,we finally choose to protocol gateway to solve the inapplicability of TCP/IP in space.We focus on CCSDS AOS as space communication link protocol. After analysis of the main network structure, business class and business types, we select services suitable to bear IP datagrams in the space link. Then we analyze and select the AOS service level for space station Internet aiming at high error rates problems in space environment.By making use of existing resources and transport system, we analyze the specific implementations for Space Internet services and design the space station Internet service system architecture. Then we decribe the task of every part of the system briefly and focus on the design of a protocol gateway.Through hierarchical analysis, we know the main problem of impletion of the gateway over network layer is TCP acknowledge, and IP address forgery is its key issue. Package transmission is done according to different datagram protocol gateway under the link layer.After completing TCP / IP and CCSDS protocol conversion programming, this paper analyzed and selected Linux operating system, and design the embedded protocol gateway on ARM development board. Finally, the function of the protocol gateway is tested through writing UDP and TCP client and server program.