Review on free-space optical communications for delay and disruption tolerant networks

The increase of data-rates that are provided by free-space optical (FSO) communications is essential in our data-driven society. When used in satellite and interplanetary networks, these optical links can ensure fast connections, yet they are susceptible to atmospheric disruptions and long orbital delays. The Delay and Disruption Tolerant Networking (DTN) architecture ensures a reliable connection between two end nodes, without the need for a direct connection. This can be an asset when used with FSO links, providing protocols that can handle the intermittent nature of the connection. This paper provides a review on the theoretical and state-of-the-art studies on FSO and DTN. The aim of this review is to provide motivation for the research of an optical wireless satellite network, with focus on the use of the Licklider Transmission Protocol. The assessment presented establishes the viability of these networks, providing many examples to rely on, and summarizing the most recent stage of the development of the technologies addressed.info:eu-repo/semantics/publishedVersio

Proactive TCP mechanism to improve Handover performance in Mobile Satellite and Terrestrial Networks

Emerging standardization of Geo Mobile Radio (GMR-1) for satellite system is having strong resemblance to terrestrial GSM (Global System for Mobile communications) at the upper protocol layers and TCP (Transmission Control Protocol) is one of them. This space segment technology as well as terrestrial technology, is characterized by periodic variations in communication properties and coverage causing the termination of ongoing call as connections of Mobile Nodes (MN) alter stochastically. Although provisions are made to provide efficient communication infrastructure this hybrid space and terrestrial networks must ensure the end-to-end network performance so that MN can move seamlessly among these networks. However from connectivity point of view current TCP performance has not been engineered for mobility events in multi-radio MN. Traditionally, TCP has applied a set of congestion control algorithms (slow-start, congestion avoidance, fast retransmit, fast recovery) to probe the currently available bandwidth on the connection path. These algorithms need several round-trip times to find the correct transmission rate (i.e. congestion window), and adapt to sudden changes connectivity due to handover. While there are protocols to maintain the connection continuity on mobility events, such as Mobile IP (MIP) and Host Identity Protocol (HIP), TCP performance engineering has had less attention. TCP is implemented as a separate component in an operating system, and is therefore often unaware of the mobility events or the nature of multi-radios' communication. This paper aims to improve TCP communication performance in Mobile satellite and terrestrial networks.Comment: 5 pages, 2 figure

Routing in the Space Internet: A contact graph routing tutorial

A Space Internet is possible, as long as the delay and disruption challenges imposed by the space environment are properly tackled. Because these conditions are not well addressed by terrestrial Internet, more capable Delay-Tolerant Networking (DTN) protocols and algorithms are being developed. In particular, the principles and techniques for routing among ground elements and spacecraft in near-Earth orbit and deep-space are enacted in the Contact Graph Routing (CGR) framework. CGR blends a set of non-trivial algorithm adaptations, space operations concepts, time-dynamic scheduling, and specific graph models. The complexity of that framework suggests a need for a focused discussion to facilitate its direct and correct apprehension. To this end, we present an in-depth tutorial that collects and organizes first-hand experience on researching, developing, implementing, and standardizing CGR. Content is laid out in a structure that considers the planning, route search and management, and forwarding phases bridging ground and space domains. We rely on intuitive graphical examples, supporting code material, and references to flight-grade CGR implementations details where pertinent. We hope this tutorial will serve as a valuable resource for engineers and that researchers can also apply the insights presented here to topics in DTN research.Fil: Fraire, Juan Andres. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Universitat Saarland; AlemaniaFil: De Jonckère, Olivier. Technische Universität Dresden; AlemaniaFil: Burleigh, Scott C.. California Institute of Technology; Estados Unido

Marshall Space Flight Center Faculty Fellowship Program

The 2017 Marshall Faculty Fellowship Program involved 21 faculty in the laboratories and departments at Marshall Space Flight Center. These faculty engineers and scientists worked with NASA collaborators on NASA projects, bringing new perspectives and solutions to bear. This Technical Memorandum is a compilation of the research reports of the 2017 Marshall Faculty Fellowship program, along with the Program Announcement (Appendix A) and the Program Description (Appendix B). The research affected the following six areas: (1) Materials (2) Propulsion (3) Instrumentation (4) Spacecraft systems (5) Vehicle systems (6) Space science The materials investigations included composite structures, printing electronic circuits, degradation of materials by energetic particles, friction stir welding, Martian and Lunar regolith for in-situ construction, and polymers for additive manufacturing. Propulsion studies were completed on electric sails and low-power arcjets for use with green propellants. Instrumentation research involved heat pipes, neutrino detectors, and remote sensing. Spacecraft systems research was conducted on wireless technologies, layered pressure vessels, and two-phase flow. Vehicle systems studies were performed on life support-biofilm buildup and landing systems. In the space science area, the excitation of electromagnetic ion-cyclotron waves observed by the Magnetospheric Multiscale Mission provided insight regarding the propagation of these waves. Our goal is to continue the Marshall Faculty Fellowship Program funded by Center internal project offices. Faculty Fellows in this 2017 program represented the following minority-serving institutions: Alabama A&M University and Oglala Lakota College

Experimental Evaluation of TCP-Based DTN for Cislunar Communications in Presence of Long Link Disruption

<p/> <p>Delay/disruption tolerant networking (DTN) technology is considered a new solution to highly stressed communications in space environments. To date, little work has been done in evaluating the effectiveness and performance of the available DTN protocols when they are applied to an interplanetary Internet, especially in presence of a long link disruption. In this paper, we present an experimental investigation of the DTN architecture with a Bundle Protocol (BP) running over TCP-based convergence layer (TCPCL) protocol in a simulated cislunar communication environment characterized by a long link disruption. The intent of this work is to investigate the effectiveness of the TCPCL-based DTN protocol in coping with long link disruptions, through realistic file transfer experiments using a PC-based test-bed. The experiment results show that the DTN protocol is effective in handling a long link disruption experienced in data transmission accompanied by a cislunar link delay and a high BER. The performance of the DTN is most adversely affected by link disruption time in comparison to the effect of link delay and BER. For the transmissions with a very long link disruption of hours, the variations in goodput are nominal with respect to the change in cislunar link delay.</p