Inter-satellite Communication Research Articles

NetSat—Challenges and lessons learned of a formation of 4 nano-satellites

The objective of the NetSat mission was to develop underlying technologies for small satellite formation flying and to demonstrate it at the level of four nano-satellites in three-dimensional configurations. Thus, base technologies, such as orbit determination, attitude determination and control, inter-satellite communication, and multi-satellite operations were studied and implemented on a 3U CubeSat platform. Technological challenges concerned in particular the precision 3-axis attitude control system in combination with an electric continuous low-thrust propulsion system. Different control approaches for efficient transitions between various formation topologies were analyzed, taking the limitations of the hardware platform (propellant mass, thrust level, power budget, attitude control capabilities) as well as external orbit perturbations into account and allowing for distributed control of multi-satellite formations. In a research program of over 15 years, the essential technologies for formations of small satellites were realized subsequently and then tested in orbit on multiple missions. On this basis, NetSat was launched on 28. September 2020 on a Soyuz rocket into a circular orbit of an altitude of 575km. During the operations phase several new operations concepts developed in the project, namely the Compass IoT network spanning all ground and satellite systems with more than 50 nodes, or a flexible operations frontend with auto-operations capabilities could be tested and allowed for operating such a multi-satellite network. Additionally, the implemented inter-satellite link among the satellites could be established and tested extensively, marking the first time that four 3U CubeSats were able to successfully demonstrate inter-satellite communication in orbit.

Cooperative Downloading for LEO Satellite Networks: A DRL-Based Approach.

In low earth orbit (LEO) satellite-based applications (e.g., remote sensing and surveillance), it is important to efficiently transmit collected data to ground stations (GS). However, LEO satellites’ high mobility and resultant insufficient time for downloading make this challenging. In this paper, we propose a deep-reinforcement-learning (DRL)-based cooperative downloading scheme, which utilizes inter-satellite communication links (ISLs) to fully utilize satellites’ downloading capabilities. To this end, we formulate a Markov decision problem (MDP) with the objective to maximize the amount of downloaded data. To learn the optimal approach to the formulated problem, we adopt a soft-actor-critic (SAC)-based DRL algorithm in discretized action spaces. Moreover, we design a novel neural network consisting of a graph attention network (GAT) layer to extract latent features from the satellite network and parallel fully connected (FC) layers to control individual satellites of the network. Evaluation results demonstrate that the proposed DRL-based cooperative downloading scheme can enhance the average utilization of contact time by up to 17.8% compared with independent downloading and randomly offloading schemes.

Multi-parameter influenced acquisition model with an in-orbit jitter for inter-satellite laser communication of the LCES system.

With the development of large low earth orbit (LEO) communication constellations, the efficiency of laser inter-satellite link (ISL) establishing become the bottleneck for subsequent large-scale launch and rapid networking applications of LEO communication constellations. Hence, we establish the pointing jitter error structure of LEO communication experiment satellites (LCES) system. The error structure can be used to trace the source of errors and evaluate the in-orbit jitter. And we derive an analytical expression of the acquisition probability density function (PDF) which comprehensively considering the influence of the scanning region, the pointing jitter error, the overlap factor and the in-orbit jitter error. The multi-parameter influenced acquisition model is validated by Monte Carlo (MC) simulations and semi-physical tests. The results reveals that the multi-parameter influenced acquisition model can be used to guide the in-orbit ISL establishing.

Steering Toward the Future: The Use of Piezo Technology for Optical Intersatellite Communication

Recent years have seen a reemergence of interest and investment in low Earth orbit (LEO) satellite constellations. First proposed in the 1990s, the construction of such constellations was once the hopeful plan of companies, such as Iridium, Globalstar, Odyssey, and Teledesic [1]. Unfortunately, most of these plans never fully came to fruition as the upfront construction costs were unfeasible, and a new competing network implementing fiber optic cables was introduced. These fiber optic cable networks promised users high data rates at a fraction of the construction costs of a satellite network. Today, as worldwide data throughput and coverage requirements increase beyond the capacity of fiber optic cable networks, companies, such as SpaceX, Amazon, ViaSat, OneWeb, and Telesat, are resurrecting the idea of LEO constellations [2]. In order to avoid the fate of their predecessors, these companies must build robust constellations with reliable satellites as launching satellites comes at high costs. One of the most critical systems aboard these satellites is the communication terminal that allows each satellite to communicate with other satellites in the constellation.

Networked TT&C for mega satellite constellations: A security perspective

Satellite constellations are promising in enabling the global Internet. However, the increasing constellation size also complicates tracking, telemetry and command (TT&C) systems. Traditional ground-based and space-based approaches have encountered significant obstacles due to, e.g., the limited satellite visible arc and long transmission delay. Considering the fast development of intersatellite communications, synergy among multiple connected satellites can be exploited to facilitate TT&C system designs. This leads to networked TT&C, which requires much less predeployed infrastructures and even performs better than traditional TT&C systems. In this paper, we elaborate system characteristics of networked TT&C compared with traditional ground-based and space-based TT&C, and propose the unique security challenges and opportunities for networked TT&C, which includes secure routing and trust mechanisms. Furthermore, since networked TT&C is a novel scenario with few relevant researches, we first investigate the current researches on secure routing and trust mechanisms for traditional terrestrial and satellite networks, and then accordingly deliver our security perspectives considering the system characteristics and security requirements of networked TT&C.

Inter-satellite optical wireless communication (IsOWC) systems challenges and applications: a comprehensive review

Abstract Satellite communication, in over half a century have attained remarkable breakthrough in high speed transmission. These innovations, on the other hand, have come in tandem with significant performance improvements in other IT and telecommunications systems. As a result, these significant benefits are not as visible to the broader public as they would be as if this burst of performance had occurred in isolation. In nutshell, space satellite communication using optical technology provide powerful alternative to radio frequency (RF) and make communication reliable and cost effective. Satellite communications systems allow a whole new race of civilian and defence operations in surveillance, telecommunications, object tracking and space exploration. Since independent satellites are restricted by volume, space and strength, small satellites production in bulk clusters may be effective for a range of wildfire monitoring, science missions, mapping in gravity and water management exploration, among others. The development of communications satellites would provide for a more comprehensive understanding of the near-earth environment as well as a more efficient and cost-effective way of reaching space, thanks to the utilisation of multi-satellite systems. As a result, when satellites are designing, IsOWC is an utmost point to be considered. The numerous researches being performed in the satellite communications for introducing multi communications based on different orbits are described in this study. IsOWC systems over radio frequency based communication are preferred due to large bandwidth, high speed, absence of electromagnetic interference (EMI), lower transmission losses and improved security. We also present a detailed listing of challenges in Is-OWC such as Doppler shift, point ahead angle, satellite vibration and tracking, acquisition tracking and pointing (ATP) and background noise sources.

Investigation of Inter-Satellite OWC Incorporating Dense WDM and Polarization Interleaving (PI)

Inter-satellite communication based on lasers (LIC) is a possible choice for future satellite networks because to ultra-high capacity and speed systems that may be achieved using compact, light-weight, and low-power optical equipment. The performance of a 64 × 40 GB/s optical wireless system with polarisation diversity for dense WDM is investigated in this research paper. Using a DWDM system with a channel spacing of 50 GHz, a high-speed system is achieved to meet the broad bandwidth needs of data services in satellites. A polarisation diversity approach is implemented in the system to decrease polarisation crosstalk and nonlinearities among nearby WDM channels. Furthermore, a comparison of the polarisation interleaved and traditional DWDM-OWC systems is performed. In addition, it was discovered that a system with varying states of polarisation across neighbouring channels performs better in terms of Q-factor and BER than a traditional system.

An MBSE Architectural Framework for Inter‐Satellite Communication in a Multiorbit Disaggregated System

AbstractThe Multi‐Orbit Disaggregated System (MODS) concept is a disaggregation strategy geared towards improved resiliency and flexibility of space missions by dispersing payloads and/or functionality across multiple small satellites (SmallSats). Although SmallSats make good candidates for deployment as a MOD System, their success hinges on the ability to realize reliable Inter‐Satellite Communication (ISC). To this end, we investigate the efficacy of developing a model‐based systems engineering (MBSE) Architectural Framework for ISC to guide and constrain instantiations of ISC architecture solutions. An MBSE architectural framework is a systems engineering artifact that defines a set of views required to describe an architecture based on MBSE principles and practices. It provides a standardized structure and guidance to capture architectural decisions while maximizing opportunities for commonality, consistency, and interoperability within the Domain of Interest. To achieve well‐defined architecture descriptions, a MODS architectural framework pattern, and a comprehensive architectural framework for the ISC (sub)system are created and presented. The Systems Modeling Language (SysML) (OMG, 2019) serves as the modeling language for the framework design.

Neural-network-based adaptive quantized attitude takeover control of spacecraft by using cellular satellites

The problem of attitude takeover control of spacecraft by using cellular satellites with the limited inter-satellite communication capacity, the unknown inertia matrix and external disturbances is studied. A hysteresis quantizer is employed to quantize the signal of control torque generated by the controller cellular satellite. The signal of quantized control torque is transmitted to the actuator cellular satellites only when the quantization signal changes, which can greatly reduce the communication burden between the controller cellular satellite and the actuator cellular satellites. To approximate the unknown attitude dynamics of the spacecraft, the radial basis function neural network is introduced. Furthermore, a distributed control allocation strategy is proposed to deal with the control allocation problem for the actuator cellular satellites with faults. Lastly, the effectiveness of the proposed scheme is validated by numerical simulations.

Mission-Oriented Real-Time Health Assessments of Microsatellite Swarm Orbits

Real-time health assessments are of great importance for the safe and stable operation of in-orbit swarms. To solve the problems of existing real-time health assessments of microsatellite swarms, such as the difficulty of selecting a multisource and assessment calculation normalization, this paper proposes a real-time health assessment method applicable to mission-oriented swarms. The method divides the microsatellite swarm into three levels: single satellite, intersatellite communication link and swarm effectiveness, which establish a multilevel index system by adopting the reliability evaluation based on random failure and failure by loss, a health evaluation based on natural connectivity, and a real-time dynamic analysis based on swarm topology. For the swarm effectiveness during the mission, the multilevel index and the entropy weight method are used to construct the effectiveness evaluation model of the whole swarm, and the health state evaluation of the swarm is realized based on the variable weight principle. The simulation results show that this method can quantify the health state of the microsatellite swarm in real-time, and it can predict the health state after the fault without maintenance.

Design and Analysis of High-Capacity MIMO System in Line-of-Sight Communication.

The phase of the channel matrix elements has a significant impact on channel capacity in a mobile multiple-input multiple-output (MIMO) communication system, notably in line-of-sight (LoS) communication. In this paper, the general expression for the phase of the channel matrix at maximum channel capacity is determined. Moreover, the optimal antenna configuration of the 2 × 2 and 3 × 3 transceiver antenna array is realized for LoS communication, providing methods for optimal antenna placement, which can be used in short-range LoS communication and non-scattering environment communication, such as coupling train communication and inter-satellite communication. Simulation results show that the 2 × 2 rectangular antenna array is more suitable for the communication of coupling trains, while the 3 × 3 circular arc antenna array is more suitable for virtual coupling trains according to antenna configurations. Moreover, the 2 × 2 antenna rectangular configuration proposed in this paper has reached the optimal channel in inter-satellite communication, which lays a foundation for the deployment of communication systems.

Composable security for inter-satellite continuous-variable quantum key distribution in the terahertz band.

Continuous-variable quantum key distribution (CVQKD) can be effectively compatible with off-the-shelf communication systems and has been proven to be the security against collective attacks in the finite-size regime and composability. In this paper, we classify three different trust levels for the loss and noise experienced by the sender and receiver. Based on these trust levels, we derive the composable finite-size security bounds of inter-satellite CVQKD in the terahertz (THz) band. We also show how these trust levels can nontrivially increase the composable secret key rates of THz-CVQKD and tolerate higher loss. Furthermore, the numerical simulations strongly support the feasibility of inter-satellite THz-CVQKD even in the worst trust level. This work provides an efficient path for building an inter-satellite quantum communication network.

Polarization‐independent dual narrow‐band perfect metamaterial absorber for optical communication

AbstractIn this paper, we demonstrate a dual narrow‐band perfect metamaterial absorber for optical communication, where a silicon nano‐disk array is placed on a thin gold film separated by a dielectric layer. Numerical results reveal that dual narrow‐band perfect absorption peaks, which are attributed to waveguide mode and magnetic dipole resonance mode, are achieved at 1310 and 1550 nm, respectively. The results show that the absorption of the two peaks is higher than 99% under the normal incidence of both TE and TM polarizations and the bandwidth is 5 and 15 nm, respectively. Moreover, the absorption peak at 1310 nm can be independently tuned by varying the thickness of the dielectric layer. These findings imply that the proposed absorber can be used in the field of optical communication, frequency‐selective photodetection, and intersatellite laser communication.

Cooperation in Space: HAPS-Aided Optical Inter-Satellite Connectivity With Opportunistic Scheduling

Issues with tracking, precision pointing, and Doppler shift are the major sources of performance loss in laser inter-satellite communication that can severely decrease the coverage and overall performance of satellite constellations. As a solution to these problems, we propose a cooperation strategy in which a high altitude platform station (HAPS) staying at a quasi-stationary position contributes to the inter-satellite connectivity. In this setup, the HAPS node uses two different scheduling approaches: one that relies on the zenith angle; the other on instantaneous signal-to-noise ratio. To quantify the performance of the proposed scheme, overall outage probabilities for the two scheduling methods are obtained. In addition, guidelines for the design of practical inter-satellite networks are provided.

Terabyte capacity-enabled (10 x 400 Gbps) Is-OWC system for long-haul communication by incorporating dual polarization quadrature phase shift key and mode division multiplexing scheme

Inter-satellite optical wireless communication (Is-OWC) links can become promising solutions to realize the next-generation high-speed communication services. The operation of Global Navigation Satellite Systems can be improved with the use of Is-OWC links through ranging and communication services. However, the key challenge in Inter-satellite link (ISL) is its effective range which is limited due to pointing errors. In this work, we propose to develop a high-capacity and long-reach Is-OWC link by incorporating hybrid mode division multiplexing (MDM) and wavelength division multiplexing (WDM) schemes to transmit ten independent channels over 40000kms Is-OWC link. Each channel is capable of carrying 400Gbps data which is encoded by the dual polarization quadrature phase shift key technique with required signal to noise ratio (SNR) and received power. The proposed Is-OWC link satisfies the enhanced communication within Geostationary Earth Orbit (GEO) and Low Earth Orbit (LEO) satellites. The proposed Is-OWC is further evaluated under the impact of space turbulences, particularly transmitter and receiver pointing errors. The result reported that the proposed Is-OWC link can transmit 4Tbps data over 16000kms with the transmitter pointing error of 2μrad and receiver pointing error of 1μrad.

A 60‐GHz low‐noise amplifier with +7.258‐dBm third‐order input intercept point using current reuse feedforward distortion cancellation for 5G emerging communication

AbstractIn the ever‐growing 5G technology, the millimetre‐wave (mmWave) frequency spectrum is the inevitable mainstream for high‐speed wireless communication. The wide‐ranging spectrum bandwidth of the mmWave frequency attracts interest in radio frequency (RF) front‐end design which will be very much beneficial for security and cellular‐based applications such as intersatellite communication and automotive vehicle‐to‐vehicle communication. The RF front end requires low‐power and low‐noise receiver architecture for effective satellite communication, and it needs high throughput with maximum data transfer for cellular‐based applications. To address these challenges, this paper presents a novel low‐noise amplifier (LNA) operating from 57.12‐ to 66.25‐GHz frequency. The design is implemented using UMC 65‐nm CMOS process technology, and the post‐layout simulations are carried out using the Cadence Spectre RF tool. At 60 GHz, the LNA exhibits a power gain of 15.46 dB, minimum noise figure (NF) of 1.32 dB while consuming 6.59 mW from a 1.2‐V supply. The LNA employs the current reuse feedforward distortion cancelation technique to improve the third‐order input intercept point (IIP3) to +7.258 dBm. The proposed LNA provides a relatively better figure of merit compared to some of the recently proposed mmWave LNA architectures.

Investigations on mode-division multiplexed free-space optical transmission for inter-satellite communication link

Investigations on mode-division multiplexed free-space optical transmission for inter-satellite communication link

Analysis of the influence of natural and climatic conditions in the Arctic and the Far North on the stability of air traffic

The analysis of the influence of natural and climatic conditions of the Arctic and Far North on the stability of air connection is investigated in this article. The provision of year-round mainline, interregional and regional air transportation is associated with the complexity of controlling the flight path of aircraft in extreme Arctic conditions. For the Arctic zone, the possibility of using a constellation of low-orbit satellite communication systems is being considered for transmitting data on the position of an aircraft to a control tower located on the ground. In this case, data transmission is possible both using GSM communication through ground stations, and using inter-satellite communication lines.

Dynamic Network Formation for FSO Satellite Communication

Satellite network optimization is essential, particularly since the cost of manufacturing, launching and maintaining each satellite is significant. Moreover, classical communication optimization methods, such as Minimal Spanning Tree, cannot be applied directly in dynamic scenarios where the satellite constellation is constantly changing. Motivated by the rapid growth of the Star-Link constellation that, as of Q4 2021, consists of over 1600 operational LEO satellites with thousands more expected in the coming years, this paper focuses on the problem of constructing an optimal inter-satellite (laser) communication network. More formally, given a large set of LEO satellites, each equipped with a fixed number of laser links, we direct each laser module on each satellite such that the underlying laser network will be optimal with respect to a given objective function and communication demand. In this work, we present a novel heuristic to create an optimal dynamic optical network communication using an Ant Colony algorithm. This method takes into account both the time it takes to establish an optical link (acquisition time) and the bounded number of communication links, as each satellite has a fixed amount of optical communication modules installed. Based on a large number of simulations, we conclude that, although the underlying problem of bounded-degree-spanning-tree is NP-hard (even for static cases), the suggested ant-colony heuristic is able to compute cost-efficient solutions in semi-real-time.

Coarse-refined combined scanning method of beaconless inter-satellite laser communication system

Coarse-refined combined scanning method of beaconless inter-satellite laser communication system