Survey of Inter-Satellite Communication for Small Satellite Systems: Physical Layer to Network Layer View
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paper_title: Small Satellites: Past, Present, and Future

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"Small Satellites" is the first book to describe the state of the art in microstats, nanostats, picostats, and CubeSats and the possible missions they can perform. More than two dozen internationally renowned contributors provide commentary on 50 years of history.
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paper_title: Software Defined Radio implementation of DS-CDMA in inter-satellite communications for small satellites

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In this paper, we study the problem of multi-user inter-satellite communications in a network of small satellites and design and implement of an optimum CDMA-based multiple access communication using Software Defined Radios. Inter-satellite links (ISL) enable small satellites to exchange information and share resources while reducing the traffic load to the ground. The ISL assist in performing advanced functions including distributed processing and autonomous applications. By utilizing the ISL in maintaining the relative distance between the satellites, navigation, and positioning accuracy is improved greatly. The ideology proposed here is to implement remote modifications in inter-satellite communication after launch using Software Defined Radios (SDRs), while accommodating an adaptive autonomous small satellite network. Remote upgrades from the ground as well as the potential to accommodate new applications and future services without hardware changes is very promising. Software defined radio-based implementation of an ISL can assist in enabling an adaptive and reconfigurable communication system, which can achieve higher data rates and modification of frequencies. In this paper, we designed and implemented a multi-user inter-satellite communication network using SDRs, where Code Division Multiple Access (CDMA) technique is utilized to manage the multiple access to shared communication channel among the satellites. This research is the first work to study and implement the utilization of SDRs for inter-satellite communications in small satellite systems.
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paper_title: Functional, physical, and organizational architectures of a fractionated space infrastructure for long-term earth observation missions

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Fractionated spacecraft is a novel architecture of distributed space systems (DSS), where its functionalities, such as computation, communication, data storage, payload, and even power generation, are distributed over several independent spacecraft that share those functionalities through a wireless network. It is this physically separated yet functionally wireless-linked characteristic that makes fractionated spacecraft unique to other space systems. Compared with traditional monolithic spacecraft, there are two main features of fractionated spacecraft. One is physical decomposition of the single spacecraft into several modules; the other is information integration among modules. Each module in the system hosts one or several components, which may be the functional parts of a satellite such as pay-load or resource components. In order to perform information integration, modules should maintain a cluster fight, which is distinguishable from formation flying due to the fact that there is no requirement for precise station-keeping. However, several technical barriers need to be broken down to pave the way for fractionated spacecraft to come into being. Along with networking, wireless communication, wireless power transfer, and distributed computing, cluster operation has been identified as one of the enabling technologies [1]. Challenges for cluster operations may be internal, for example to avoid collisions among modules, or external, for example to evade debris-like threats.
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paper_title: Agent computing applications in distributed satellite systems

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Space and satellite systems are considered to be the most extreme environment to design for and are fraught with engineering difficulty. Performance metrics such as fault tolerance, reliability, pre-determinism and heritage are still high of the list of requirements for all missions. But with the advent of modern day electronics, greater computing capability and networking technologies have enabled research into distributed satellite systems, where multiple spacecraft work collaboratively to perform a mission. Leveraging from these technologies, a satellite can be considered one of many nodes in an autonomous system. This paper proposes the use of an Agent based computing platform to solve orbit dynamics problems leading to a highly mobile and decentralized system. The latest Agent platforms are compared and possible Agent applications are presented; specifically, distributed image compression and a novel topology reconfiguration scheme.
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paper_title: A software platform for fractionated spacecraft

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A fractionated spacecraft is a cluster of independent modules that interact wirelessly to maintain cluster flight and realize the functions usually performed by a monolithic satellite. This spacecraft architecture poses novel software challenges because the hardware platform is inherently distributed, with highly fluctuating connectivity among the modules. It is critical for mission success to support autonomous fault management and to satisfy real-time performance requirements. It is also both critical and challenging to support multiple organizations and users whose diverse software applications have changing demands for computational and communication resources, while operating on different levels and in separate domains of security. The solution proposed in this paper is based on a layered architecture consisting of a novel operating system, a middleware layer, and component-structured applications. The operating system provides primitives for concurrency, synchronization, and secure information flows; it also enforces application separation and resource management policies. The middleware provides higher-level services supporting request/response and publish/subscribe interactions for distributed software. The component model facilitates the creation of software applications from modular and reusable components that are deployed in the distributed system and interact only through well-defined mechanisms. Two cross-cutting aspects — multi-level security and multi-layered fault management — are addressed at all levels of the architecture. The complexity of creating applications and performing system integration is mitigated through the use of a domain-specific model-driven development process that relies on a dedicated modeling language and its accompanying graphical modeling tools, software generators for synthesizing infrastructure code, and the extensive use of model-based analysis for verification and validation.
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paper_title: Wireless Sensor Motes for Small Satellite Applications

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Motes are low-cost COTS (commercial off-the-shelf) microchips, which integrate a processor, onboard sensor, RF communications link, and a power unit. High levels of power efficiency can be achieved with the use of the IEEE 802.15.4 protocol for communication between the motes, allowing long-term periods of operation for motes and reducing the power requirements of a spacecraft. The article examines the feasibility of using sensors for harness reduction between satellite subsystems, and for inter-satellite networking capabilities between satellite swarms
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paper_title: Intersatellite Links: Lower Layer Protocols for Autonomous Constellations

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Abstract : In order to have autonomous formation-flying satellite constellations in low earth orbit (LEO), the satellites in the constellation must be able to communicate with each other directly via intersatellite links (ISLs). Current ISL implementations use lower layer link protocols based on existing networking protocols such as X.25 and LAP-B, which were not designed specifically for ISL use. This paper compares current and upcoming lower layer protocols in an attempt to identify a protocol for widespread ISL use such that interaction among different constellations is possible and the addition of new satellites to existing constellations is simpler.
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paper_title: Formation flying within a constellation of nano-satellites: The QB50 mission

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QB50 is a mission establishing an international net work of 50 nano-satellites for multi-point, in-situ measurements in the lower thermosphere and re-entry research. As part of the QB50 mission, the Delft University of Technology intends to contribute two nano-satellites both being equipped with a highly miniaturized propulsio n system in addition to the science payload. This allows to demonstrate formation flyin g between these two nano-satellites which will enhance the mission both with respect to techn ology demonstration and science return. The opportunities and challenges of formation flyin g by a subset of satellites within a constellation of freely floating spacecraft are sys tematically identified and analyzed.
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paper_title: PROBA-3: Precise formation flying demonstration mission

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Abstract Formation Flying (FF) has generated a strong interest in many space applications, most of them involving a significant complexity for building for example on-board large “virtual structures or distributed observatories”. The implementation of these complex formation flying missions with critical dependency on this new, advanced and critical formation technology requires a thorough verification of the system behaviour in order to provide enough guarantees for the target mission success. A significant number of conceptual or preliminary designs, analyses, simulations, and HW on-ground testing have been performed during the last years, but still the limitations of the ground verification determine that enough confidence of the behaviour of the formation flying mission will only be possible by demonstration in flight of the concept and the associated technologies. PROBA-3 is the mission under development at ESA for in-flight formation flying demonstration, dedicated to obtain that confidence and the necessary flight maturity level in the formation flying technologies for those future target missions. PROBA-3 will demonstrate technologies such as formation metrology sensors (from very coarse to highest accuracy), formation control and GNC, system operability, safety, etc. During the last years, PROBA-3 has evolved from the initial CDF study at ESA, to two parallel phase A studies, followed by a change in the industrial configuration for the Bridging step between A and B phases. Currently the SRR consolidation has been completed, and the project is in the middle of the phase B. After the phase A study SENER and GMV were responsible for the Formation Flying System, within a mission core team completed by OHB-Sweden, QinetiQ Space and CASA Espacio. In this paper an overview of the PROBA-3 mission is provided, with a more detailed description of the formation flying preliminary design and results.
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paper_title: ESPACENET: A Framework of Evolvable and Reconfigurable Sensor Networks for Aerospace&#150;Based Monitoring and Diagnostics

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There is an increasing need to develop flexible, reconfigurable, and intelligent multi-spacecraft sensing networks for aerospace-based monitoring and diagnostics. Technical advancements in ad hoc networking, MEMS devices, low-power electronics, adaptive and reconfigurable hardware, micro-spacecraft, and micro-sensors have enabled the design and development of such highly integrated space wireless sensor networks. This paper proposes the framework for an evolvable sensor network architecture, investigated as part of the ESPACENET project, collocated at the University of Edinburgh, Essex, Kent and Surrey. The aim is to design a flexible and intelligent embedded network of reconfigurable piconodes optimised by a hierarchical multi-objective algorithm. Although the project is targeted at aerospace applications, the same intelligent network can be used for many earth bound applications such as environmental and medical diagnostics
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paper_title: Space Internet Architectures and Technologies for NASA Enterprises

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NASA's future space communication needs and requirements will be addressed through a space communications network that mirrors the terrestrial Internet in its capabilities and flexibility. NASA's needs and requirements for future data gathering and distribution by this Space Internet have been obtained from NASA's Earth Science Enterprise (ESE), the Human Exploration and Development in Space (HEDS), and the Space Science Enterprise (SSE). ::: ::: ::: ::: To address NASA's future needs, we propose and describe an integrated communications infrastructure based on Internet technologies, the architectures within the infrastructure, and the elements that make up the architectures. ::: ::: ::: ::: The architectures meet the requirements of the enterprises beyond 2010 with Internet compatible technologies and functionality. The elements of an architecture include the backbone, access, inter-spacecraft, and proximity communication parts. From the architectures, technologies have been identified which have the most impact and are critical for the implementation of the architectures. Published in 2002 by John Wiley & Sons, Ltd.
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paper_title: Space-based wireless sensor networks: Design issues

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This paper is concerned with a satellite sensor network, which applies the concept of terrestrial wireless sensor networks to space. 1,2 Constellation design and enabling technologies for picosatellite constellations such as distributed computing and intersatellite communication are discussed. The research, carried out at the Surrey Space Centre, is aimed at space weather missions in low Earth orbit (LEO). Distributed satellite system scenarios based on the flower constellation set are introduced. Communication issues of a space based wireless sensor network (SB-WSN) in reference to the Open Systems Interconnection (OSI) networking scheme are discussed. A system-on-a-chip computing platform and agent middleware for SB-WSNs are presented. The system-on-a-chip architecture centred around the LEON3 soft processor core is aimed at efficient hardware support of collaborative processing in SB-WSNs, providing a number of intellectual property cores such as a hardware accelerated Wi-Fi MAC and transceiver core and a Java co-processor. A new configurable intersatellite communications module for picosatellites is outlined.
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paper_title: Systems engineering of inter-satellite communications for distributed systems of small satellites

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Present design processes for satellite networks mainly involve interconnected system models and their parameter-based simulations without emphasizing high level requirements in the process. What is missing is a systems engineering approach and a system of verification and validation based on formal representation and analysis. We propose a systems design methodology for inter-satellite communication based on the Responsive and Formal Design (RFD) [1]–[3], which addresses the need for a model-based system engineering approach coupled with a system of validation and verification based on formal representation and analysis. The goal is to apply the RFD process to provide a solution for the Inter-Satellite Communications (ISC) problem within the Open Systems Interconnection (OSI) framework. The OSI represents a standard framework for communication between devices. It divides the communication process into seven layers, with each one providing well-defined functions and services. We will address the integration of the RFD process with the OSI framework for ISC. The RFD process involves levels of design abstraction and refinement which correspond to layers or groups of layers of the OSI model. The process illustrates how the complete framework for ISC unfolds in an iterative manner.
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paper_title: A Survey of Communication Sub-systems for Intersatellite Linked Systems and CubeSat Missions

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Intersatellite links or crosslinks provide direct connectivity between two or more satellites, thus eliminating the need for intermediate ground stations when sending data. Intersatellite links have been considered for satellite constellation missions involving earth observation and communications. Historically, a large satellite system has needed an extremely high financial budget. However, the advent of the successful CubeSat platform allows for small satellites of less than one kilogram. This low-mass pico-satellite class platform could provide financially feasible support for large platform satellite constellations. This article surveys past and planned large intersatellite linking systems. Then, the article chronicles CubeSat communication subsystems used historically and in the near future. Finally, we examine the history of inter-networking protocols in space and open research issues with the goal of moving towards the next generation intersatellite-linking constellation supported by CubeSat platform satellites.
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paper_title: Towards the next generation of nanosatellite communication systems

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The communication systems currently used on nanosatellites are usually well-proven commercial-off-the-shelf units with data rates up to 9.6 kbps. A careful analysis shows that by using advancements in microelectronics, a higher communication performance can be achieved, even within the power and mass limitations of a nanosatellite. This paper presents a new approach to maximize the performance of nanosatellite communication systems by taking a systems engineer’s perspective and by regarding the entire satellite instead of the communication system only. It is found that efficiency can be gained by also including the electrical power system in the design. The parameters that influence the performance of the communication system are identified. It is shown how these parameters can be tuned such that the limited resources on a nanosatellite are used most effectively. The results are used in designing the communication system of Delfi-n3Xt, the next nanosatellite mission of Delft University of Technology. The results presented in the paper can be used as a guideline to designing a nanosatellite of the next generation.
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paper_title: Space mission analysis and design

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List of Authors. preface. 1. The Space Mission Analysis and Design Process. 2. Mission Characterization. 3. Mission Evaluation. 4. Requirements Definition. 5. Space Mission Geometry. 6. Introduction to Astrodynamics. 7. Orbit and Constellation Design. 8. The Space Environment and Survivability. 9. Space Payload Design and Sizing. 10. Spacecraft Design and Sizing. 11. Spacecraft Subsystems. 12. Space Manufacture and Test. 13. Communications Architecture. 14. Mission Operations. 15. Ground System Design and Sizing. 16. Spacecraft Computer Systems. 17. Space Propulsion Systems. 18. Launch Systems. 19. Space Manufacturing and Reliability. 20. Cost Modeling. 21. Limits on Mission Design. 22. Design of Low-Cost Spacecraft. 23. Applying the Space Mission Analysis and Design. Appendices: A: Mass Distribution for Selected Satellites. B: Astronautical and Astrophysical Data. C: Elliptical Orbit Equations. D: Spherical Geometry Formulas. E: Universal Time and Julian Dates. F: Units and Conversion Factors. Index.
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paper_title: RCP-Planet : A rate control protocol for InterPlaNetary Internet

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SUMMARY UDP traffic is a part of the aggregate traffic over InterPlaNetary Internet backbone links, which includes planet images and multimedia data from some scientific observations. Existing rate control schemes cannot solve the rate control problem in InterPlaNetary Internet which is characterized by extremely long propagation delays, high link errors, asymmetrical bandwidth, and blackouts. In this paper, a rate control protocol, RCP-Planet, is proposed to address all the above challenges. RCP-Planet consists of two novel algorithms, i.e. Begin State and Operational State. The protocol is based on a novel rate probing mechanism, i.e. sending probing sequences to capture the available bandwidth. A new rate control scheme is designed to update the transmission rate based on the observed rate for the probing sequence. Tornado codes are used for packet-level FEC because of their fast encoding and decoding speed. Bandwidth asymmetry problem is addressed by FEC block-level ACKs. Moreover, RCP-Planet incorporates Blackout State into the protocol to improve performance in blackout conditions. Simulation results show that RCPPlanet achieves high throughput performance, fairness, and is delay tolerant. Copyright # 2007 John Wiley & Sons, Ltd.
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paper_title: Research on Formation of Microsatellite Communication with Genetic Algorithm

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For the formation of three microsatellites which fly in the same orbit and perform three-dimensional solid mapping for terra, this paper proposes an optimizing design method of space circular formation order based on improved generic algorithm and provides an intersatellite direct spread spectrum communication system. The calculating equation of LEO formation flying satellite intersatellite links is guided by the special requirements of formation-flying microsatellite intersatellite links, and the transmitter power is also confirmed throughout the simulation. The method of space circular formation order optimizing design based on improved generic algorithm is given, and it can keep formation order steady for a long time under various absorb impetus. The intersatellite direct spread spectrum communication system is also provided. It can be found that, when the distance is 1 km and the data rate is 1 Mbps, the input wave matches preferably with the output wave. And LDPC code can improve the communication performance. The correct capability of (512, 256) LDPC code is better than (2, 1, 7) convolution code, distinctively. The design system can satisfy the communication requirements of microsatellites. So, the presented method provides a significant theory foundation for formation-flying and intersatellite communication.
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paper_title: Self-Steering Antenna Arrays for Distributed Picosatellite Networks

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Blaine T. Murakami 1 17 Annual AIAA/USU Conference on Small Satellites Abstract—The potential for using self-steering arrays for secure crosslinks in picosatellite networks is investigated. The principle of operation and methods of characterization of these so-called retrodirective arrays is reviewed, and examples developed by our group are presented. New challenges for the space environment are identified, specifically the development of two-dimensional, circularly polarized retrodirective arrays optimized for size and power consumption.
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paper_title: MIMO over Satellite: A Review

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The present article carries out a review of MIMO-based techniques that have been recently proposed for satellite communications. Due to the plethora of MIMO interpretations in terrestrial systems and the particularities of satellite communications, this review is built on two pillars, namely fixed satellite and mobile satellite. Special attention is given to the characteristics of the satellite channel, which will ultimately determine the viability of MIMO over satellite. Finally, some future research directions are identified.
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paper_title: Inter-satellite links for cubesats

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Realizing inter-satellite links is a must for ensuring the success of cubesat swarm missions. Nevertheless, it has hardly been considered until now. The communication systems for cubesats have to deal with a few peculiar demands regarding consumed power, geometry and throughput. Depending on the type of application, required data rates can go up to tens of megabits per second, while power consumption and physical size are limited by the platform. The proposed communication scheme will combine power-efficient modulation and channel coding with multiple access and spread spectrum techniques, enabling the deployment of multiple satellites. Apart from this, the antenna system has to be designed such that links can be established and maintained independent of the satellites' orientation. An electrically steerable radiation pattern is achieved by placing antennas on each face of the cube. Conformal beamforming provides the system with 5 dBi gain for any desired direction of transmission, eliminating the need for attitude control. Furthermore, using planar antennas reduces the complexity of the mechanical part as they require no deployment.
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paper_title: Radio Propagation Channel Measurements for Multi-Antenna Satellite Communication Systems: A Survey

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For the terrestrial infrastructure, the multiple-input multiple-output (MIMO) architecture is a key technology that has brought the wireless gigabit vision closer to reality. Satellite communication systems have not been immune from this wave of innovation, and theoretical and experimental efforts have recently been devoted to the investigation of the applicability of multiple-antenna techniques to these systems. This paper intends to highlight and critically present the most important results from measurement campaigns conducted to characterize the radio channel of multi-antenna satellite systems. Emphasis is given on the viability of MIMO technology over satellite, and the potential enhancements in terms of channel capacity and link reliability that can be achieved through spatial and/or polarization diversity. The configurations under investigation range from very simple single-input multiple-output (SIMO) systems, with multiple antennas only at the terrestrial receiver, to quite complex and challenging systems, such as dual-satellite multiple-input single-output (MISO) systems, and single-satellite dual-polarized MIMO systems. The spotlight is on land mobile satellite (LMS) systems in outdoor radio propagation environments. However, satellite-to-indoor reception is also included.
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paper_title: Antenna Arrays A Computational Approach

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A comprehensive tutorial on the design and practical applications of antenna arrays An antenna array is an assembly of antenna elements that maximizes a received or transmitted signal in a desired direction. This practical book covers a wide range of antenna array topics that are becoming increasingly important in wireless applications, with emphasis on array design, applications, and computer modeling. Each chapter in Antenna Arrays builds upon the previous chapter, progressively addressing more difficult material. Beginning with basic electromagnetics/antennas/antenna systems information, the book then deals with the analysis and synthesis of arrays of point sources and their associated array factors. It presents a sampling of different antenna elements that replace these point sources, then presents element configurations that do not have to lie along a line or in a plane. The complex and difficult-to-predict interactions of elements and electromagnetic waves are introduced, along with computer modeling and experiments that are necessary for predicting the performance of arrays where mutual coupling is important. Then, various approaches to getting signals to and from the array elements to a computer where the signal detection takes place are explored, as are the numerical techniques behind smart antennas. The book emphasizes the computational methods used in the design and analysis of array antennas. Also featured are signal processing and numerical modeling algorithms, as well as pictures of antenna arrays and components provided by industry and government sources, with explanations of how they operate. Fully course-tested, Antenna Arrays serves as a complete text in phased array design and theory for advanced undergraduate- and graduate-level courses in electronics and communications, as well as a reference for practicing engineers and scientists in wireless communications, radar, and remote sensing.
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paper_title: Intersatellite Links and Relative Navigation: Pre-conditions for Formation Flights with Pico- and Nanosatellites

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Abstract A group of satellites can be classified as a constellation, formation or cluster. Multiple coordinated satellites are described as a formation, if a closed-loop control is adjusted, thus providing a coordinated motion control on basis of their relative positions to preserve the topology (Schilling [2009]). This technology enables various application scenarios, for example, interferometry or in-orbit servicing and it is subject to multiple technological requirements related to formation flying, limited resources or scientific payloads. In the framework of the feasibility study NaKoFo, this paper discusses the potential benefits, drawbacks and problems associated with intersatellite links and relative navigation with pico- and nanosatellites. The requirements of an intersatellite link are analyzed based on frequency, modulation, antenna, power and network protocol. A short overview of adequate communication systems for pico- and nanosatellites is also presented. Technologies for relative position determination are presented and discussed regarding their applicability in small satellite systems as well as their requirements on an intersatellite link.
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paper_title: Inter-Satellite Communications for Small Satellite Systems

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Small satellite technology has opened a new era in aerospace engineering by decreasing space mission costs, without greatly reducing the performance. The concept of formation flying using small satellites is becoming popular because of their potential to perform coordinated measurements of remote sensing space missions. The current state of art in satellite communications is a one hop link between satellite and ground station. Very little work has been done on inter-satellite communications. This paper aims to design and evaluate feasible MAC and routing layer protocols for distributed small satellite networks. The possibility to implement proposed MAC and routing protocols for two different formation flying patterns are investigated. To validate the authorsâ€™ proposed system model, they use extensive simulations to evaluate the performance of the system using throughput, access delay and end-to-end delay.
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paper_title: Characterizing Network Architecture for Inter-satellite Communication and Relative Navigation in Precise Formation Flying

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Precise formation flying (PFF) missions require formation acquisition and maintenance through interactions among spacecraft by inter-satellite communication and relative navigation. That requires the network architecture to satisfy dedicated system constraints of time-criticality for updating navigation measurements and flexibility for implementation across various phases of mission operations. Potentially applicable architectures that combine different multiple access technologies, half-duplex/full duplex configurations, and network topologies are discussed and evaluated. Half-duplex CDMA with roles rotating among all spacecraft is shown more suitable and efficient for PFF missions. Its limitation in terms of multiple access interference is analyzed as well.
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paper_title: Introduction to Wireless and Mobile Systems

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Learn how wireless systems work, how mobility is supported, what the underlying infrastructure is and what interactions are needed among different functional components with INTRODUCTION TO WIRELESS AND MOBILE SYSTEMS, 4e. Focusing on qualitative descriptions and the realistic explanations of relationships between wireless systems and performance parameters, this user-friendly book helps you learn this exciting technology through relevant examples, such as understanding how a cell phone starts working as soon as they get out of an airplane.
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paper_title: Development of a Satellite Sensor Network for Future Space Missions

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Future spacecraft are envisioned as autonomous, miniature, intelligent and massively distributed systems. At the Surrey Space Centre, a research project is currently under investigation, which aims to develop a picosatellite sensor network using the CubeSat platform. The proposed satellite sensor network will be used to demonstrate technology advances in space, including modified IEEE 802.11 wireless standard for inter-satellite links (ISL), distributed computing for computationally intensive onboard signal processing, and reconfigurable system-on-a-chip (SoC) design.
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paper_title: Wireless Sensor Networks: A Networking Perspective

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Learn the fundamental concepts, major challenges, and effective solutions in wireless sensor networking This book provides a comprehensive and systematic introduction to the fundamental concepts, major challenges, and effective solutions in wireless sensor networking (WSN). Distinguished from other books, it focuses on the networking aspects of WSNs and covers the most important networking issues, including network architecture design, medium access control, routing and data dissemination, node clustering, node localization, query processing, data aggregation, transport and quality of service, time synchronization, network security, and sensor network standards. With contributions from internationally renowned researchers, Wireless Sensor Networks expertly strikes a balance between fundamental concepts and state-of-the-art technologies, providing readers with unprecedented insights into WSNs from a networking perspective. It is essential reading for a broad audience, including academic researchers, research engineers, and practitioners in industry. It is also suitable as a textbook or supplementary reading for electrical engineering, computer engineering, and computer science courses at the graduate level.
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paper_title: Potentials and Limitations of CDMA Networks for Combined Inter-Satellite Communication and Relative Navigation

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Precision formation flying missions require formation acquisition and maintenance through the interactions among spacecraft by the inter-satellite communication and relative navigation. This paper analyses the dedicated system constraints of the network architecture for precision formation flying missions. The critical time issue and the operational flexibility are found to be two main constraints. Potentially applicable architectures are discussed and evaluated, which combine different multiple access technologies, half-duplex/full-duplex configurations and network topologies. It is proven that the most suitable and efficient architecture for PFF mission is the use of the halfduplex CDMA with the topology that allows the role of being reference rotating from one spacecraft to another in different time slots. The capability of CDMA is also investigated in terms of the multiple access interference. The paper verifies that this interference can limit the maximum number of spacecraft and bounds the inter-satellite range diversity. The interference exhibits a Doppler dependency and suffers as well from the near-far problem. Inter-satellite navigation accuracy will easily drop down below meter level at the moments of zero- or n-kHz Doppler crossovers, and also in case of the signals being corrupted by the near-by interferences. Two realistic mission scenarios are provided to verify the severe effects of the interference. Operational considerations and interference mitigation methods are also recommended.
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paper_title: Preliminary internetworking simulation of the QB50 cubesat constellation

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Constellations of small satellites now become a great alternative for scientific missions to study Earth. As a result, they should be considered appropriate communication mechanisms to retrieve the data collected. This article studies the possibility to implement TCP and UDP over IP through the use of intersatellite links and distributed ground stations, such as Genso project. We evaluate parameters like delay end-to-end and throughput for different configurations of the QB50 constellation proposed by von Karman Institute for Fluids Dynamics (VKI).
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paper_title: Global Educational Network for Satellite Operations (GENSO)

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The GENSO project is an international project that officially began in October 2006. The main goal of the project is to improve educational spacecraft communications by creating an international network of university and amateur ground stations. With the realization of such a network, more experimental data can be downloaded, a greater number of students can participate in realtime spacecraft mission operations with a hands-on approach, and new scientific missions can be realized.
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paper_title: Design and Implementation of LDMA for Low Earth Orbit Satellite Formation Network

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For low earth orbit satellite formation network, the performance of MAC depends on the degree of competition in the network. Contention-based MAC protocols such as CSMA suffer from inefficiency under the condition of high contention, but it is in the opposite way of slot-based MAC protocols such as TDMA performance. The mixed solution which combines both competition-based mechanism and schedule-based mechanism is important to resolve network effectivity. In this paper, we propose a LDMA (load-division multiple access) according to the characteristics of inter-satellite link in a small low orbit satellite formation network. Through experimental studies, we found that LDMA has the effective management for channel utilization both under the condition of low level competition and high level competition. And at the same time LDMA can effectively solve the problem of network congestion and transmission collision caused by the heavy load in the satellite formation network.
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paper_title: Efficient, flexible, scalable inter-satellite networking

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Satellite networks pose challenging requirements on the MAC sub-layer to provide flexible, scalable and efficient cross-links between satellites' communication modules. A high throughput, robust and peer-to-peer MAC protocol is introduced to inexpensively address the challenging requirements of satellite networks. In a single-radio solution, the problem of providing high network capacity for nearby satellites while maintaining links with those that are 100s of Km away is not solved with existing MAC protocols. A dual-range, dual-mode MAC and a UWB PHY is proposed that proves to solve this problem easily while maintaining flexibility and scalability to be suitable to any satellite mission. A hybrid Frequency-time division multiple access gives the system the ability to reuse available RF spectrum efficiently for long-range, power-limited links.
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paper_title: Wireless Communication in LEO Satellite Formations

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In this paper we investigate key IEEE 802.11 optimization techniques with the aim to adapt the commercial-of-the-shelf (COTS) wireless standard for inter-satellite communication in autonomous distributed spacecraft formations. Optimisation approaches such as the tuning of the IEEE 802.11 physical layer parameters and enhancing the data link layer for space applications are described. The integration of smart antennas with the MAC protocol is also considered aiming at increasing the capacity and throughput while minimizing interference and collision in close proximity links. Finally, simulation results are presented to demonstrate the effectiveness of the proposed approaches for satellite formations in low earth orbit polar and inclined orbits.
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paper_title: User Datagram and Bundle Protocol for Distributed Small Satellite Topologies

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Many planned Earth observation satellite missions use distributed satellite systems in constellation or cluster orbits instead of one, large satellite with many instru ments. This network of satellites and ground stations allows data to be efficiently downlin ked. Ho wever, to create a netwo rking protocol for constellations of small Earth observing satellites , several limitations need to be addressed, including distributed topology management, slow downlin k data-rates, and single point-to-point communication. Since distributed satellite constellations exacerbate the severity of these limitations, a thorough analysis of a constellation's network performance is required to ensure that task objectives are achievable. In this paper, we co mpared low Earth orbit (LEO) Earth observing satellite constellations using delay tolerant networking protocols and the user datagram p rotocol (UDP). The constellations' inter-satellite lin ks and downlin ks were evaluated using network metrics such as access window time, drop-rat io, and throughput. We simu lated these network metrics using the Network Simu lator 3 (ns-3). Prev ious works have proposed satellite constellations for Earth observation, however, constellations of s mall satellites have not been analy zed for network metrics. Results show that a sun-synchronous constellation with a repeating ground track outperforms a flo wer constellation with respect to increased access time, reduced drop-ratio, and higher throughput. The simulat ions also determined the optimu m med ia access control slot time and packet transmission intervals for long distance satellite links. Additionally, we were able to co mpare the throughput performance of UDP to abundle protocol by adding nodes with delay tolerant networking protocol imp lementations.
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paper_title: A New Routing Algorithm of Two-tier LEO/MEO Mobile Satellite Communication Systems

paper_content:

The performance of a two-tier LEO/MEO satellite network including inter-satellite links (ISL's) is analyzed. Specific emphasis is laid on the design of an ATM-based routing scheme for the ISL part of the system (MEO layer). The approach is to prepare a virtual topology by means of virtual path connections (VPC's) connecting all pairs of end nodes in the ISL sub-network for a complete period in advance, similar to implementing a set of (time dependent) routing tables. The search for available end-to-end routes within the ISL network is based on a new routing Algorithm (S-DRA) integrates the advantages of static routing and dynamic routing. Additionally, a new quick clustering scheme is introduced to monitor the faults to guarantee the usability of VPC. The new algorithm guarantees that: 1) the survey of VPC route is not carried on blindly no longer because of the application of the clustering scheme, 2) the flow of control information is reduced, 3) whereas the channel of link is allowable, it can reduce handover frequency as much as possible. Finally, a simulation on MEO layer analyzes the performance of the new routing algorithm
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paper_title: Inter-Satellite Communications for Small Satellite Systems

paper_content:

Small satellite technology has opened a new era in aerospace engineering by decreasing space mission costs, without greatly reducing the performance. The concept of formation flying using small satellites is becoming popular because of their potential to perform coordinated measurements of remote sensing space missions. The current state of art in satellite communications is a one hop link between satellite and ground station. Very little work has been done on inter-satellite communications. This paper aims to design and evaluate feasible MAC and routing layer protocols for distributed small satellite networks. The possibility to implement proposed MAC and routing protocols for two different formation flying patterns are investigated. To validate the authorsâ€™ proposed system model, they use extensive simulations to evaluate the performance of the system using throughput, access delay and end-to-end delay.
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paper_title: A Distributed Multicast Routing Scheme for Multi-Layered Satellite IP Networks

paper_content:

In this paper, a distributed multicast routing scheme is introduced for multi-layered satellite IP networks, which include GEO, MEO, and LEO layers. This scheme aims to minimize the total cost of multicast trees in the satellite network. Multicast trees are constructed and maintained in the dynamic satellite network topology in a distributed manner. Simulation results are provided to evaluate the performance of the new scheme in terms of end-to-end delay and multicast tree cost.
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paper_title: Satellite Networks Routing Protocol Issuesand Challenges: A Survey

paper_content:

LEO satellite networks play a very important role in broadcasting Internet and connecting remote places at the time of natural calamities. Routing plays a very important role in faster data transfer by taking shortest path. LEO satellite networks are the preferred choice due to less propagation delay and packet loss as compared to GEO satellite network. The multimedia applications and live transmissions cannot bear packet loss, jitter, and timeliness and need the high throughput through the transmission. We did a survey for the best routing protocol for satellite networks.
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paper_title: A Distributed Multipath Routing Strategy for LEO Satellite Networks

paper_content:

Traditional routing algorithms for Low Earth Orbit (LEO) often adopt single path and greed mechanism, which are ambivalent to realize optimum performances for the whole network. Compared with single path routing, Multipath routing has the advantages of strong fault tolerance and load balancing which is more appropriate for LEO satellite networks. A distributed multipath routing algorithm combined with Multi-Agent System (MASMR) is proposed in the paper. In MASMR, mobile agents and 'blackboard' are introduced. The former is used to gather multipath information and the latter provides direct interactive mode between agents. Simulation results show that, compared with Ant Colony Optimization, MASMR not only presents better end-to-end delay and but also tracks the fast changing topology of LEO satellite networks.
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paper_title: On the applicability of reliable transport protocols in satellite delay tolerant and disruptive networks

paper_content:

SUMMARY ::: ::: Delay tolerant networking (DTN) is an emerging technology introduced for deep-space communications to address both very large propagation delay or link disruptions. The DTN paradigm results promising in several satellite-based scenarios where either physical or service interruption might be experienced. This paper focuses on a set of selected satellite-based scenarios, where the DTN paradigm adoption greatly improves the unicast and multicast communications' performance with limited costs in terms of both software add-ons and architectural modifications. Copyright © 2013 John Wiley & Sons, Ltd.
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paper_title: A destruction-resistant dynamic routing algorithm for LEO/MEO satellite networks

paper_content:

Since the current off-line routing algorithms for low earth orbit (LEO)/medium earth orbit (MEO) satellite networks lack the ability of getting information on traffic distribution and link state, they can neither optimize routes nor adapt to the unpredictable topological changes. A destruction-resistant dynamic routing algorithm is proposed in this paper to solve these defects. Based on a cluster-based link-state-delivery scheme, link state information is transmitted all over the network at a low bandwidth cost; and then a border-satellite source routing scheme optimizes the routes by considering the factors like link state, routing handovers, etc. An off-line routing algorithm and the destruction-resistant dynamic routing algorithm are applied to Iridium system model for simulation. Simulation results show that in addition to the enhanced survivability, the latter's performance is better, especially when some inter-satellite links (ISLs) break down.
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paper_title: On Multicast Routing Using Rectilinear Steiner Trees for LEO Satellite Networks

paper_content:

In this paper, we propose a bandwidth-efficient multicast routing mechanism using rectilinear Steiner trees for IP-based LEO satellite networks. Different from the previous approach which minimizes the end-to-end delay, our mechanism minimizes the total bandwidth, i.e, the number of hops, used by a multicast tree since the wireless bandwidth in satellite networks is a limited and scarce resource. We propose a new integer linear programming formulation for network planning and a distributed algorithm for protocol design. Our simulation results show that the trees created by our approach use less bandwidth than shortest-path trees. Moreover, the difference of the optimal solutions and the solutions obtained by our distributed algorithm is within 5% on average.
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paper_title: Network layer integration of terrestrial and satellite IP networks over BGP-S

paper_content:

To accomplish network layer integration of terrestrial and satellite IP networks, special exterior gateway protocols are needed. In this work, a new exterior gateway protocol called Border Gateway Protocol-Satellite version (BGP-S) is introduced that enables automated discovery of paths that go through the satellite network. This protocol is designed to work in only one terrestrial gateway in every autonomous system and enables the forwarding of discovered paths in the Internet using the BGP-4 protocol.
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paper_title: A Satellite Routing Algorithm Based on Optimization of Both Delay and Bandwidth

paper_content:

The merits of the routing algorithm will have a direct impact on the performance of a communication network. Traditional satellite routing algorithms are based on shortest path algorithm, the simply considering least delay, the least hop or the best link-bandwidth utilization. For the request of real-time in information network, a routing algorithm BDSR (bandwidth-delay satellite routing) comprehensively considering both delay and bandwidth between satellite-link is proposed in this paper. Moreover, we prove that the routing algorithm is an ideal one that is suitable for LEO satellite network on NS2 simulation platform.
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paper_title: High-Throughput Distributed Spacecraft Network : Architecture and Multiple Access Technologies

paper_content:

BBN Technologies (BBN), under a task for the Space Communications Project, designed the High-Throughput Distributed Spacecraft Network, or Hi-DSN. It provides a self-forming vertically integrated network infrastructure for establishing and maintaining high-throughput multi-hop communications among spacecraft operating in diverse orbits. The Hi-DSN integrates the predictability of orbital movement to establish and maintain cross-links and multi-hop routes, ad hoc networking capabilities to autonomously discover ''new'' neighbors, null-steered spatial multiplexing to maximize re-use of the allocated spectrum, and variable-rate cross-links to maximize network connectivity under large inter-spacecraft distances and distance differentials. The Hi-DSN architecture is hierarchical and can be extended to provide dynamic ''terminal affiliation and handoff'' for transferring data from spacecraft to aircraft and spacecraft to ground terminals and sensors. The descriptions included in this paper focus on the aspects of the architecture that are relevant for the planet vicinity networks, part of NASA's future space-based internetwork communications infrastructure, and specifically on the enabling physical-layer, medium-access control (MAC) layer and sub-network level (i.e., below IP) technologies required to create a scalable communications infrastructure that can be used to extend the (terrestrial) Internet to space. In a follow-on development for NASA, BBN is designing the architectural extensions and developing the protocols to extend Internet VPNs to space, or SpaceVPNs.
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paper_title: A Survey of Communication Sub-systems for Intersatellite Linked Systems and CubeSat Missions

paper_content:

Intersatellite links or crosslinks provide direct connectivity between two or more satellites, thus eliminating the need for intermediate ground stations when sending data. Intersatellite links have been considered for satellite constellation missions involving earth observation and communications. Historically, a large satellite system has needed an extremely high financial budget. However, the advent of the successful CubeSat platform allows for small satellites of less than one kilogram. This low-mass pico-satellite class platform could provide financially feasible support for large platform satellite constellations. This article surveys past and planned large intersatellite linking systems. Then, the article chronicles CubeSat communication subsystems used historically and in the near future. Finally, we examine the history of inter-networking protocols in space and open research issues with the goal of moving towards the next generation intersatellite-linking constellation supported by CubeSat platform satellites.
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paper_title: NeXt generation/dynamic spectrum access/cognitive Radio Wireless Networks: A Survey

paper_content:

Today's wireless networks are characterized by a fixed spectrum assignment policy. However, a large portion of the assigned spectrum is used sporadically and geographical variations in the utilization of assigned spectrum ranges from 15% to 85% with a high variance in time. The limited available spectrum and the inefficiency in the spectrum usage necessitate a new communication paradigm to exploit the existing wireless spectrum opportunistically. This new networking paradigm is referred to as NeXt Generation (xG) Networks as well as Dynamic Spectrum Access (DSA) and cognitive radio networks. The term xG networks is used throughout the paper. The novel functionalities and current research challenges of the xG networks are explained in detail. More specifically, a brief overview of the cognitive radio technology is provided and the xG network architecture is introduced. Moreover, the xG network functions such as spectrum management, spectrum mobility and spectrum sharing are explained in detail. The influence of these functions on the performance of the upper layer protocols such as routing and transport are investigated and open research issues in these areas are also outlined. Finally, the cross-layer design challenges in xG networks are discussed.
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paper_title: CRAHNs : Cognitive radio ad hoc networks

paper_content:

Cognitive radio (CR) technology is envisaged to solve the problems in wireless networks resulting from the limited available spectrum and the inefficiency in the spectrum usage by exploiting the existing wireless spectrum opportunistically. CR networks, equipped with the intrinsic capabilities of the cognitive radio, will provide an ultimate spectrum-aware communication paradigm in wireless communications. CR networks, however, impose unique challenges due to the high fluctuation in the available spectrum as well as diverse quality-of-service (QoS) requirements. Specifically, in cognitive radio ad hoc networks (CRAHNs), the distributed multi-hop architecture, the dynamic network topology, and the time and location varying spectrum availability are some of the key distinguishing factors. In this paper, intrinsic properties and current research challenges of the CRAHNs are presented. First, novel spectrum management functionalities such as spectrum sensing, spectrum sharing, and spectrum decision, and spectrum mobility are introduced from the viewpoint of a network requiring distributed coordination. A particular emphasis is given to distributed coordination between CR users through the establishment of a common control channel. Moreover, the influence of these functions on the performance of the upper layer protocols, such as the network layer, and transport layer protocols are investigated and open research issues in these areas are also outlined. Finally, a new direction called the commons model is explained, where CRAHN users may independently regulate their own operation based on pre-decided spectrum etiquette.
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paper_title: A reputation-based Stackelberg game approach for spectrum sharing with cognitive cooperation

paper_content:

In this paper, we consider the problem of spectrum sharing with cooperation in a wireless system with two pairs of source-destination links, which have different priorities to access the channel. The cognitive low priority user (LPU) cooperates with the high priority user (HPU), acting as a relay, in exchange for an opportunity to access the channel. We study the interactions between the HPU and the LPU using a game theoretical approach to search for the optimal time allocation for individual transmissions and cooperation among users. We propose a new Stackelberg game formulation, in which the reputation of both users is considered to encourage cooperation and prevent misbehavior. The proposed utility functions are designed so that fairness and energy efficiency are taken into account.
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paper_title: Primary radio user activity models for cognitive radio networks: A survey

paper_content:

Abstract Cognitive Radio Networks have been emerged as a promising solution for solving the problem of spectrum scarcity and improving spectrum utilization by opportunistic use of spectrum. Cognitive radio networks utilize the spectrum which is licensed to primary radio users when they are not utilizing it, i.e., when the spectrum is idle. Thus, the performance of cognitive radio networks is highly dependent upon the activity of primary radio users. Hence, it is very important to model primary radio users activity in cognitive radio networks. By keeping this in mind, several models in the literature have been proposed for modeling primary radio users activity. But there is not any source which consolidate all these models into single platform. Therefore, this paper combines all the primary radio user activity models for cognitive radio networks at a single place. The goal of this paper is to provide a single source in the form of survey paper by which a reader can get an idea about which primary radio user activity models have been used in the literature for cognitive radio networks and how the modeling is performed. Furthermore, we also discuss issues, challenges and future directions for primary radio activity models. In fact, in this paper, different primary radio user activity models have been presented along with their classification. This paper also discusses those approaches which performed real implementation for spectrum occupancy along with spectrum bands on which the implementation is performed and location where implementation is carried out. In summary, this paper provides up-to-date survey of primary radio user activity models for cognitive radio networks.
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paper_title: Software Defined Radio: Challenges and Opportunities

paper_content:

Software Defined Radio (SDR) may provide flexible, upgradeable and longer lifetime radio equipment for the military and for civilian wireless communications infrastructure. SDR may also provide more flexible and possibly cheaper multi-standard-terminals for end users. It is also important as a convenient base technology for the future context-sensitive, adaptive and learning radio units referred to as cognitive radios. SDR also poses many challenges, however, some of them causing SDR to evolve slower than otherwise anticipated. Transceiver development challenges include size, weight and power issues such as the required computing capacity, but also SW architectural challenges such as waveform application portability. SDR has demanding implications for regulators, security organizations and business developers.
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paper_title: Software defined radios for small satellites

paper_content:

Clusters, constellations, formations, or `swarms' of small satellites are fast becoming a way to perform scientific and technological missions more affordably. As objectives of these missions become more ambitious, there are still problems in increasing the number of communication windows, supporting multiple signals, and increasing data rates over reliable intersatellite and ground links to Earth. Also, there is a shortage of available frequencies in the 2 m and 70 cm bands due to rapid increase in the number of CubeSats orbiting the Earth - leading to further regulatory issues. Existing communication systems and radio signal processing Intellectual Property (IP) cores cannot fully address these challenges. One of the possible strategies to solve these issues is by equipping satellites with a Software Defined Radio (SDR). SDR is a key area to realise various software implementations which enable an adaptive and reconfigurable communication system without changing any hardware device or feature. This paper proposes a new SDR architecture which utilises a combination of Field Programmable Gate Array (FPGA) and field programmable Radio Frequency (RF) transceiver to solve back-end and front- end challenges and thereby enabling reception of multiple signals or satellites using single user equipment.
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paper_title: Security issues for downloaded code in mobile phones

paper_content:

'Software defined radio' (SDR) is a technology that will appear in future generations of mobile phones, i.e. following the third-generation mobile phone technology that is currently being defined and developed. Early versions of 'pragmatic' SDR will allow the terminal to be reconfigured at any level of its protocol stack. Ultimately, the 'pure' SDR technology will allow a mobile phone or terminal to have its air interface software configured or reconfigured by other software (or software parameters) that have been downloaded to the terminal, e.g. over the air, or from a remote server via the Internet and one's personal computer (PC). A number of security issues arise with downloaded code that implements the air interface functions, and these may not be obvious simply from looking at the way PC software is updated on-line today. This paper starts with an outline of the code that allows a mobile phone to operate over a particular air interface. This sets the baseline for a discussion of the security issues surrounding the change of this code from one that is fixed and downloaded once only, to code that is reconfigurable during the life of a product.
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paper_title: Software Defined Radio implementation of DS-CDMA in inter-satellite communications for small satellites

paper_content:

In this paper, we study the problem of multi-user inter-satellite communications in a network of small satellites and design and implement of an optimum CDMA-based multiple access communication using Software Defined Radios. Inter-satellite links (ISL) enable small satellites to exchange information and share resources while reducing the traffic load to the ground. The ISL assist in performing advanced functions including distributed processing and autonomous applications. By utilizing the ISL in maintaining the relative distance between the satellites, navigation, and positioning accuracy is improved greatly. The ideology proposed here is to implement remote modifications in inter-satellite communication after launch using Software Defined Radios (SDRs), while accommodating an adaptive autonomous small satellite network. Remote upgrades from the ground as well as the potential to accommodate new applications and future services without hardware changes is very promising. Software defined radio-based implementation of an ISL can assist in enabling an adaptive and reconfigurable communication system, which can achieve higher data rates and modification of frequencies. In this paper, we designed and implemented a multi-user inter-satellite communication network using SDRs, where Code Division Multiple Access (CDMA) technique is utilized to manage the multiple access to shared communication channel among the satellites. This research is the first work to study and implement the utilization of SDRs for inter-satellite communications in small satellite systems.
---
paper_title: Software Defined Radio: Challenges and Opportunities

paper_content:

Software Defined Radio (SDR) may provide flexible, upgradeable and longer lifetime radio equipment for the military and for civilian wireless communications infrastructure. SDR may also provide more flexible and possibly cheaper multi-standard-terminals for end users. It is also important as a convenient base technology for the future context-sensitive, adaptive and learning radio units referred to as cognitive radios. SDR also poses many challenges, however, some of them causing SDR to evolve slower than otherwise anticipated. Transceiver development challenges include size, weight and power issues such as the required computing capacity, but also SW architectural challenges such as waveform application portability. SDR has demanding implications for regulators, security organizations and business developers.
---
paper_title: Software defined radios for small satellites

paper_content:

Clusters, constellations, formations, or `swarms' of small satellites are fast becoming a way to perform scientific and technological missions more affordably. As objectives of these missions become more ambitious, there are still problems in increasing the number of communication windows, supporting multiple signals, and increasing data rates over reliable intersatellite and ground links to Earth. Also, there is a shortage of available frequencies in the 2 m and 70 cm bands due to rapid increase in the number of CubeSats orbiting the Earth - leading to further regulatory issues. Existing communication systems and radio signal processing Intellectual Property (IP) cores cannot fully address these challenges. One of the possible strategies to solve these issues is by equipping satellites with a Software Defined Radio (SDR). SDR is a key area to realise various software implementations which enable an adaptive and reconfigurable communication system without changing any hardware device or feature. This paper proposes a new SDR architecture which utilises a combination of Field Programmable Gate Array (FPGA) and field programmable Radio Frequency (RF) transceiver to solve back-end and front- end challenges and thereby enabling reception of multiple signals or satellites using single user equipment.
---
paper_title: Agent computing applications in distributed satellite systems

paper_content:

Space and satellite systems are considered to be the most extreme environment to design for and are fraught with engineering difficulty. Performance metrics such as fault tolerance, reliability, pre-determinism and heritage are still high of the list of requirements for all missions. But with the advent of modern day electronics, greater computing capability and networking technologies have enabled research into distributed satellite systems, where multiple spacecraft work collaboratively to perform a mission. Leveraging from these technologies, a satellite can be considered one of many nodes in an autonomous system. This paper proposes the use of an Agent based computing platform to solve orbit dynamics problems leading to a highly mobile and decentralized system. The latest Agent platforms are compared and possible Agent applications are presented; specifically, distributed image compression and a novel topology reconfiguration scheme.
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Title: Survey of Inter-Satellite Communication for Small Satellite Systems: Physical Layer to Network Layer View

Section 1: INTRODUCTION
Description 1: This section provides an introduction to the topic, explaining the growing interest in small satellite systems, their advantages, and the concept of inter-satellite communications.

Section 2: Paper Organization
Description 2: This section outlines how the paper is structured and what each section will cover.

Section 3: Enabling Operations Using Network of Small Satellites
Description 3: This section discusses the operational capabilities of networks of small satellites, including servicing or proximity operations, autonomous operations, fractionated spacecraft, and distributed processing.

Section 4: Small Satellite Missions Involving Formation Flying Aspects
Description 4: This section provides examples of recent small satellite missions that apply formation flying concepts.

Section 5: BACKGROUND
Description 5: This section provides background information on different configurations of small satellites and the importance of inter-satellite communications in these configurations.

Section 6: Satellite Formation Flying
Description 6: This subsection explains the different types of formation flying patterns for small satellites, such as leader-follower, cluster, and constellation.

Section 7: Inter-Satellite Communications
Description 7: This subsection explains the significance of inter-satellite communications and its various facets, including types of data transmission and system constraints.

Section 8: DESIGN OF VARIOUS LAYERS OF THE OSI MODEL
Description 8: This section offers a detailed survey of the design approaches for the first three layers (physical, data link, and network) of the OSI model as applied to small satellite systems.

Section 9: OSI Physical Layer
Description 9: This subsection delves into the parameters of the physical layer such as frequency allocation, data rate, modulation and coding schemes, link design, and antenna types.

Section 10: OSI Data Link Layer
Description 10: This subsection discusses the data link layer responsibilities, including multiple access protocol design and key functions like framing, synchronization, error control, and flow control.

Section 11: OSI Network Layer
Description 11: This subsection explores routing protocols, network optimization objectives, and various routing approaches specific to small satellite systems.

Section 12: PROPOSED INTER-SATELLITE COMMUNICATION SOLUTIONS FOR SMALL SATELLITE SYSTEMS
Description 12: This section proposes solutions to the physical layer and data link layer challenges, including SDR implementation and modular antenna array designs.

Section 13: DESIGN PARAMETERS FOR INTER-SATELLITE COMMUNICATION DESIGN PROCESS
Description 13: This section specifies the main design constraints and parameters that drive the ISC design process and how they are derived.

Section 14: FUTURE RESEARCH DIRECTIONS
Description 14: This section outlines potential future research areas for enhancing inter-satellite communications, including cross-layer optimization and autonomous data transfer.

Section 15: CONCLUSION
Description 15: This section provides a summary of the survey, the significance of advancements in inter-satellite communications, and their potential impact on future missions.