The LAMS-DLC ARQ protocol

Abstract

In this paper we introduce a new data link control protocol appropriate for a low earth orbit (LEO) satellite network. The principle characteristics of an LEO satellite network are high error rates, long propagation delay, and high mobility. Although this area is traditionally dominated by forward error correction (FEC) we present a reliable protocol suited to this environment and derive the throughput for it given a finite buffer model. In our target network environment, reliability constraints may be relaxed provided that the protocol provides zero packet loss capability. The proposed scheme (called LAMS-DLC) provides a datagram service at the link level based on a Negative Acknowledgement ARQ scheme to accomplish error recovery. In LAMS-DLC the receiver sends commands for the following reasons only: to enable the sender to release buffer space held for previously transferred information frames (I-Frames); and to identify when the sender has failed. Commands are sent by the receiver so long as the link is active. The performance of the protocol is compared with the popular ARQ protocol HDLC. We show that LAMS-DLC performs better than the selective repeat HDLC and offers certain advantages in satellite networks.