A STANDARD LINK-LAYER PROTOCOL FOR SPACE MISSION COMMUNICATIONS

Abstract

A necessary step for using Internet Protocols in space is to establish the basic link-layer framing protocol for delivering Internet datagrams over satellite RF links. This paper discusses the low-level data link issues related to using the ISO standard High-level Data Link Control (HDLC) protocol to support spacecraft communications. A major driver for using HDLC is its very wide usage in the Internet today and the large amount of commercially available network equipment and test equipment. The results of a high-fidelity link simulation using HDLC are presented along with results of tests performed in 2000-2001 using Internet protocols over HDLC on the UoSAT-12 spacecraft. A rationale is provided for the selection of HDLC/Frame-Relay framing along with the IETF multi-protocol encapsulation. It also discusses the historical usage of HDLC on over 70 satellite missions. The paper also describes how HDLC relates to various applications of forward-error-correction (FEC) coding techniques, such as convolutional coding and Reed-Solomon. It describes approaches for using these techniques in ways that are independent of the protocols used at the data link layer and above. It covers issues primarily related to layer 2 (Data Link) and its relationship to layer 1 (Physical). It does not cover layer 3 (Network) and above.