Experience with Delay-Tolerant Networking from Orbit

We describe the first use from space of the Bundle Protocol for Delay-Tolerant Networking (DTN) and lessons learned from experiments made and experience gained with this protocol. The Disaster Monitoring Constellation (DMC), constructed by Surrey Satellite Technology Ltd (SSTL), is a multiple-satellite Earth-imaging low-Earth-orbit sensor network in which recorded image swaths are stored onboard each satellite and later downloaded from the satellite payloads to a ground station. Store-and-forward of images with capture and later download gives each satellite the characteristics of a node in a disruption-tolerant network. Originally developed for the Interplanetary Internet, DTNs are now under investigation in an Internet Research Task Force (IRTF) DTN research group (RG), which has developed a bundle architecture and protocol. The DMC is technically advanced in its adoption of the Internet Protocol (IP) for its imaging payloads and for satellite command and control, based around reuse of commercial networking and link protocols. These satellites use of IP has enabled earlier experiments with the Cisco router in Low Earth Orbit (CLEO) onboard the constellation s UK-DMC satellite. Earth images are downloaded from the satellites using a custom IP-based high-speed transfer protocol developed by SSTL, Saratoga, which tolerates unusual link environments. Saratoga has been documented in the Internet Engineering Task Force (IETF) for wider adoption. We experiment with the use of DTNRG bundle concepts onboard the UK-DMC satellite, by examining how Saratoga can be used as a DTN convergence layer to carry the DTNRG Bundle Protocol, so that sensor images can be delivered to ground stations and beyond as bundles. Our practical experience with the first successful use of the DTNRG Bundle Protocol in a space environment gives us insights into the design of the Bundle Protocol and enables us to identify issues that must be addressed before wider deployment of the Bundle Protocol. Published in 2010 by John Wiley & Sons, Ltd. KEY WORDS: Internet; UK-DMC; satellite; Delay-Tolerant Networking (DTN); Bundle Protoco

Assessing and improving an approach to delay-tolerant networking

Delay-tolerant networking (DTN) is a term invented to describe and encompass all types of long-delay, disconnected, disrupted or intermittently-connected networks, where mobility and outages or scheduled contacts may be experienced. 'DTN' is also used to refer to the Bundle Protocol, which has been proposed as the one unifying solution for disparate DTN networking scenarios, after originally being designed solely for use in deep space for the 'Interplanetary Internet.' We evaluated the Bundle Protocol by testing it in space and on the ground. We have found architectural weaknesses in the Bundle Protocol that may prevent engineering deployment of this protocol in realistic delay-tolerant networking scenarios, and have proposed approaches to address these weaknesses.Comment: 2 pages; First Annual CCSR Research Symposium (CRS 2011), Centre for Communication Systems Research, 30 June 201

Taking Saratoga from Space-Based Ground Sensors to Ground-Based Space Sensors

The Saratoga transfer protocol was developed by Surrey Satellite Technology Ltd (SSTL) for its Disaster Monitoring Constellation (DMC) satellites. In over seven years of operation, Saratoga has provided efficient delivery of remote-sensing Earth observation imagery, across private wireless links, from these seven low-orbit satellites to ground stations, using the Internet Protocol (IP). Saratoga is designed to cope with high bandwidth-delay products, constrained acknowledgement channels, and high loss while streaming or delivering extremely large files. An implementation of this protocol has now been developed at the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO) for wider use and testing. This is intended to prototype delivery of data across dedicated astronomy radio telescope networks on the ground, where networked sensors in Very Long Baseline Interferometer (VLBI) instruments generate large amounts of data for processing and can send that data across private IP- and Ethernet-based links at very high rates. We describe this new Saratoga implementation, its features and focus on high throughput and link utilization, and lessons learned in developing this protocol for sensor-network applications.Comment: Preprint of peer-reviewed conference paper accepted by and to appear at the IEEE Aerospace 2011 conference, Big Sky, Montana, March 201

Applying autonomy to distributed satellite systems: Trends, challenges, and future prospects

While monolithic satellite missions still pose significant advantages in terms of accuracy and operations, novel distributed architectures are promising improved flexibility, responsiveness, and adaptability to structural and functional changes. Large satellite swarms, opportunistic satellite networks or heterogeneous constellations hybridizing small-spacecraft nodes with highperformance satellites are becoming feasible and advantageous alternatives requiring the adoption of new operation paradigms that enhance their autonomy. While autonomy is a notion that is gaining acceptance in monolithic satellite missions, it can also be deemed an integral characteristic in Distributed Satellite Systems (DSS). In this context, this paper focuses on the motivations for system-level autonomy in DSS and justifies its need as an enabler of system qualities. Autonomy is also presented as a necessary feature to bring new distributed Earth observation functions (which require coordination and collaboration mechanisms) and to allow for novel structural functions (e.g., opportunistic coalitions, exchange of resources, or in-orbit data services). Mission Planning and Scheduling (MPS) frameworks are then presented as a key component to implement autonomous operations in satellite missions. An exhaustive knowledge classification explores the design aspects of MPS for DSS, and conceptually groups them into: components and organizational paradigms; problem modeling and representation; optimization techniques and metaheuristics; execution and runtime characteristics and the notions of tasks, resources, and constraints. This paper concludes by proposing future strands of work devoted to study the trade-offs of autonomy in large-scale, highly dynamic and heterogeneous networks through frameworks that consider some of the limitations of small spacecraft technologies.Postprint (author's final draft

DETN: Delay-Efficient Tolerant Network for Internet of Planet

The explosion of the internet has resulted in various emerging technologies, as for example the Internet of Things (IoT). IoT is an intelligent technology and service connecting objects in the Internet. IoT facilitates the exchange of information between people and devices that communicate with each other. Beyond IoT, we are now studying a new paradigm called Internet of Planets (IoP), in which planets in a solar system communicate with each other using the Internet. This paper presents our research in the internet communications between planets, detailing benefits, limitations and directions for future work. We propose a time (delay) information-based Delay Efficient Tolerant Networking (DETN) routing scheme for efficient data transmission among mobile nodes. The results of the proposed DTN routing algorithm using NS-3 simulation tools indicate satisfactory levels of routing performance in comparison with existing DTN algorithms

Conceptual Design of a Communication-Based Deep Space Navigation Network

As the need grows for increased autonomy and position knowledge accuracy to support missions beyond Earth orbit, engineers must push and develop more advanced navigation sensors and systems that operate independent of Earth-based analysis and processing. Several spacecraft are approaching this problem using inter-spacecraft radiometric tracking and onboard autonomous optical navigation methods. This paper proposes an alternative implementation to aid in spacecraft position fixing. The proposed method Network-Based Navigation technique takes advantage of the communication data being sent between spacecraft and between spacecraft and ground control to embed navigation information. The navigation system uses these packets to provide navigation estimates to an onboard navigation filter to augment traditional ground-based radiometric tracking techniques. As opposed to using digital signal measurements to capture inherent information of the transmitted signal itself, this method relies on the embedded navigation packet headers to calculate a navigation estimate. This method is heavily dependent on clock accuracy and the initial results show the promising performance of a notional system

DETN: delay-efficient tolerant network for internet of planet

The explosion of the internet has resulted in various emerging technologies, as for example the Internet of Things (IoT). IoT is an intelligent technology and service connecting objects in the Internet. IoT facilitates the exchange of information between people and devices that communicate with each other. Beyond IoT, we are now studying a new paradigm called Internet of Planets (IoP), in which planets in a solar system communicate with each other using the Internet. This paper presents our research in the internet communications between planets, detailing benefits, limitations and directions for future work. We propose a time (delay) information-based Delay Efficient Tolerant Networking (DETN) routing scheme for efficient data transmission among mobile nodes. The results of the proposed DTN routing algorithm using NS-3 simulation tools indicate satisfactory levels of routing performance in comparison with existing DTN algorithms.N/