Study of Teaching Materials on Demand Using Space Collaboration System

这项研究的目的是发展数据传输系统，以便向大学提供学习材料，这是作为下一代高等教育基础设施扩展大学间卫星网络“空间协作系统”所迫切需要的。TCP （Transmission Control Protocol）是一种适用于点对点连接的传输控制协议，但由于传输过程中往返时间较长，具有吞吐效率较差的特点。为此，我们采用了UDP （User Datagram Protocol）协议，实现了可靠的数据传输，实现了与多个卫星站的组播文件传输程序。系统的扩展需要在同一校园内远程使用。数据传输系统被设计为通过局域网从任何教室传输数据。在SCS房间外的房间使用SCS需要远程控制。然后，我们开发了可在远程机房操作的链接控制系统。国家航天局每年都增加VSAT站点，扩大网络。SCS已被公认为是日本远程教育的重要网络。同时进行的会话数量也会增加，这会导致预算问题。尽管图像质量和仪器操作已被评价为合理，但在技术和操作事项方面仍有若干改进SCS的要求。我们希望数据传输服务能继续有力地支持SCS用户。

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.