Study of Teaching Materials on Demand Using Space Collaboration System

本研究的目的是开发数据传输系统，为大学提供学习材料，这是扩展大学间卫星网络“空间协作系统”作为下一代高等教育基础设施的强烈需求。 TCP（传输控制协议）适用于点对点连接，但由于传播的往返时间较长，因此具有吞吐效率差的特点。为此，我们采用了UDP（用户数据报协议），实现了数据的可靠传输，与SCS的多个VSAT站实现了组播文件传输方案。SCS的扩展需要在同一校园内进行远程使用。数据传输系统旨在通过局域网从任何教室传输数据。在 SCS 室外的房间使用 SCS 需要进行远程控制。然后我们开发了可以在远距离机房操作的链路控制系统。SCS每年增加VSAT站，扩大网络。人们已经认识到SCS是日本远程教育的重要网络。同时会话的数量也会增加，这会导致预算问题。尽管图像质量和仪器操作被评估为合理，但在技术和操作方面改进 SCS 仍存在一些要求。希望数据传输服务继续为SCS用户提供强有力的支持。

The purpose of this research was to develop data transmission system for provide learning materials with universities, which was strongly required to extend Inter-University Satellite Network, "Space Collaboration System" as an infrastructure of the next generation in higher education. TCP (Transmission Control Protocol) is suitable for point-to-point connection, however, it has feature of bad throughput efficiency because of large round trip time in propagation. So, we have used UDP (User Datagram Protocol), and achieved reliable data transmission, implementing a multicast file transfer program with several VSAT stations of the SCS.Extension of the SCS needed remote use in the same campus. The data transmission system has been designed to transfer data from any lecture room through local area network. Remote control was necessary for using the SCS at the room outside the SCS room. We have then developed the link control system which can be operated at the distance room.The SCS increases the VSAT stations every year, expanding the network. It has been recognized that the SCS is an important network for distance education in Japan. The number of simultaneous session will also go up, and this causes a budget problem. There are several requirements to improve the SCS in technical and operational matters, though the quality of images and the operation of instruments have been evaluated as reasonable. We hope that the data transmission service will continue to support the SCS users strongly.