LTP PERFORMANCE EVALUATION BASED ON PHY CHARACTERISTICS FOR EARTH-MARS SATELLITE LINKS

Abstract

Humanity’s interest in space explorations has increased over the past century, specifically in our closest neighboring planet – Mars. A primary motivation for investigating the red planet is the potential for it to become the first planet, other than Earth, capable of supporting human life in the future. Consequently, significant efforts have been dedicated to building equipment capable of gathering and analyzing data from the planet. To successfully transmit this information, building robust communication frameworks is growing in importance. However, the physical properties of radio waves make transmitting data over the vast distances of space a significant challenge. To successfully transfer data, it is essential to have satellites with high gain antennas, sufficiently powerful amplifiers with high transmission power and advanced telemetry coding. Therefore, one of the objectives of this paper will be designing the physical layer between satellites. Specifically between satellites orbiting Earth, Moon and Mars, creating Earth-Moon-Mars link. This network of satellites is going to deploy the Delay Tolerant Networking (DTN) framework, which is specifically built for connections with high discontinuity, significant delays, and high likelihood of packet loss. DTN has transport layer called Licklider Transmission Protocol (LTP) which is used to transmit information over harsh conditions of space. By continuously retransmitting data when a failure is encountered, LTP achieves high robustness and reduced overhead compared to Transmission Control Protocol (TCP). The main goal of this thesis is to establish an initial connection between Earth and Moon satellites, followed by a connection between the Moon and Mars, using the segment error rate (SER) obtained from physical layer modelling. To obtain SER two various modulation schemes have been implemented. Then, LTP implementation was obtained as the number of segments in the block versus time. The main conclusion is that, to obtain a small SER, modulation of a lower order should be implemented, which diminishes transmission time and increases throughput.