Study on Methods for Constructing Layered Protocols in High-Speed Satellite Data Networks

卫星数据网络可以用来满足在许多站点之间高速传输和交换大量信息的日益增长的需求。高速数据网络发展中需要解决的一个重要问题是如何构建通信协议。本课题的目的是研究在高速卫星数据网络中构建有效的分层协议的方法。本文首先比较了在高速卫星分组网络中采用TDMD-Reservation多址协议的面向连接（CO）逻辑链路控制（LLC）协议和无连接（CL） LLC协议的性能。特别是，我们研究了信道传输速率如何影响两种LLC协议的性能，然后确定哪种LLC协议更适合任何给定的系统环境。对比表明，随着信道传输速率的增大，CL-LLC协议比CO-LLC协议具有更多的优势，并且随着接收缓冲区容量的增大和网络负载的减小，CL-LLC协议的适用区域也越来越宽。其次，我们提出了两种构建数据链协议卫星数据网络的方法：隔离型和组合型。在隔离类型中，MAC协议是独立于其LLC协议定义的，而组合类型具有与其LLC协议相关的MAC协议。本文研究了TDMA-Reservation和Slotted-ALOHA两种MAC协议，以及面向连接的LLC协议。我们比较了两种方法，发现结合TDMA-Reservation协议的组合类型总是优于相应的隔离类型，而结合Slotted-ALOHA的两种类型之间的性能差异很小。此外，我们还研究了局域网的链路级连接控制方案，作为卫星链路互联局域网的初步研究。

Satellite data networks can be used to meet an increasing demand that a large amount of information can be transmitted and exchanged at high speeds among many sites. One of the most important problems to be solved in the development of high-speed data networks is how to construct communication protocols. The objective of this project is to develop some methods for constructing efficient layered protocols in high-speed satellite data networks.We first make a performance comparison between a connection-oriented (CO) Logical Link Control (LLC) protocol and a connectionless (CL) LLC protocol in a high-speed satellite packet network with the TDMD-Reservation multiple access protocol. In particular, we examine how the channel transmission rate affects the peformance of the two LLC protocols and then determine which LLC protocol is more suitable for any given system environment. The comparison indicates that the CL-LLC protocol has more advantages over the CO-LLC protocol as the channel transmission rate increases and that the suitable region for the CL-LLC protocol becomes wider as the receive-buffer capacity increases and as the network load decreases.Next, we propose two methods for constructing the data link protocol satellite data networks : the isolated type and combined type. In the isolated type, a MAC protocol is defined independent of its LLC protocol, whereas the combined type has a MAC protocol related to its LLC protocol. We study here two MAC protocols, TDMA-Reservation and Slotted-ALOHA, and a connection-oriented LLC protocol. We compare the two methods and then see that the combined type with the TDMA-Reservation protocol always outperforms the corresponding isolated type, while the performance difference between the two types with Slotted-ALOHA is very small.In addition, we also study link-level connection control schemes in local area networks (LAN's) as a preliminary research on interconnecting LAN's by satellite links.