Search

The image integrity of real-time monitoring is crucial for monitoring crop growth, helping farmers and researchers improve production efficiency and crop yields. Unfortunately, existing schemes just focus on ground equipment and drone imaging, neglecting satellite networks in remote or extreme environments. Given that satellite internet features wide area coverage, we propose SEAIS, a secure and efficient agricultural image storage scheme combining blockchain and satellite networks. SEAIS presents the mathematical model of image processing and transmission based on satellite networks. Moreover, to ensure the integrity and authenticity of image data during pre-processing such as denoising and enhancement, SEAIS includes a secure agricultural image storage and verification method based on blockchain, homomorphic encryption, and zero-knowledge proof. Specifically, images are stored via IPFS, with hash values and metadata recorded on the blockchain, ensuring immutability and transparency. The simulation results show that SEAIS exhibits more stable and efficient processing times in extreme environments. Also, it maintains low on-chain storage overhead, enhancing scalability. [ABSTRACT FROM AUTHOR]

Copyright of Space-Integrated-Ground Information Networks is the property of Beijing Xintong Media Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recent technological advancements in space, air, and ground components have made possible a new network paradigm called “space-air-ground integrated network” (SAGIN). Unmanned aerial vehicles (UAVs) play a key role in SAGINs. However, due to UAVs' high dynamics and complexity, real-world deployment of a SAGIN becomes a significant barrier to realizing such SAGINs. UAVs are expected to meet key performance requirements with limited maneuverability and resources with space and terrestrial components. Therefore, employing UAVs in various usage scenarios requires well-designed planning in algorithmic approaches. This paper provides an essential review and analysis of recent learning algorithms in a UAV-assisted SAGIN. We consider possible reward functions and discuss the state-of-the-art algorithms for optimizing the reward functions, including Q-learning, deep Q-learning, multi-armed bandit, particle swarm optimization, and satisfaction-based learning algorithms. Unlike other survey papers, we focus on the methodological perspective of the optimization problem, applicable to various missions on a SAGIN. We consider real-world configurations and the 2-dimensional (2D) and 3-dimensional (3D) UAV trajectories to reflect deployment cases. Our simulations suggest the 3D satisfaction-based learning algorithm outperforms other approaches in most cases. With open challenges discussed at the end, we aim to provide design and deployment guidelines for UAV-assisted SAGINs.

The lack of terrestrial 4G and 5G communication infrastructure in rural and remote areas aggravates the digital divide. Satellite communication is important to achieve the universal goal of connecting the digitally unconnected population through global coverage. In this paper, first, we discuss the feasibility of hosting web services in satellites through several examples of radiation-hardened processors and computational boards. Next, we propose a Space-Based Hosting Service (SBHS) approach to deploy the content-servers or copies of terrestrial content-servers in satellites to achieve the low-latency service requirements. For SBHS, we develop mathematical models for communication, queuing, as well as computation, and use B+ tree to estimate computational delay and computational energy consumption of the content-server. Further, an optimization algorithm using Markov Decision Process (MDP) is designed to schedule computational cores in Low Earth Orbit (LEO) satellites to minimize queuing delay and computational energy consumption. The efficacy of our SBHS is evaluated using extensive simulations with the Wikipedia use-case in the Iridium-NEXT satellite constellation model under varying traffic conditions from different countries. The results show that SHBS is able to achieve less than 10 ms round trip latency worldwide and minimum end-to-end delays of 9.19 ms and 24.29 ms, respectively, for text-based and multimedia-based traffic. The 92.51% and 88.66% reduction in delay for text and multimedia traffic, respectively, compared to the benchmark schemes underlines the benefits of hosting content-servers in space for achieving ultra-low latency.

New versions of HTTP protocols have been developed to overcome many of the limitations of the original HTTP/1.1 protocol and its underlying transport mechanism over TCP. In this paper, we investigated the performance of modern Internet protocols such as HTTP/2 over TCP and HTTP/3 over QUIC in high-latency satellite links. The goal was to uncover the interaction of the new features of HTTP such as parallel streams and optimized security handshake with modern congestion control algorithms such as CUBIC and BBR over high-latency links. An experimental satellite network emulation testbed was developed for the evaluation. The study analyzed several user-level web performance metrics such as average page load time, First Contentful Paint and Largest Contentful Paint. The results indicate an overhead problem with HTTP/3 that becomes more significant when using a loss-based congestion control algorithm such as CUBIC which is widely used on the Internet. Also, the results highlight the significance of the web page structure and how objects are distributed in it. Among the various Internet protocols evaluated, the results show that HTTP/3 over QUIC will perform better by an average of 35% than HTTP/2 over TCP in satellites links specifically with a more aggressive congestion algorithm such as BBR. This can be attributed to the non-blocking stream multiplexing feature of QUIC and the reduced TLS handshake of HTTP/3.

Satellite edge computing has attracted the attention of many scholars, but the limited resources of satellite networks bring great difficulties to the processing of edge-computing-dependent tasks. Therefore, under the system model of the satellite-terrestrial joint network architecture, this paper proposes an efficient scheduling strategy based on task degrees and a resource allocation strategy based on the improved sparrow search algorithm, aiming at the low success rate of application processing caused by the dependency between tasks, limited resources, and unreasonable resource allocation in the satellite edge network, which leads to the decline in user experience. The scheduling strategy determines the processing order of tasks by selecting subtasks with an in-degree of 0 each time. The improved sparrow search algorithm incorporates opposition-based learning, random search mechanisms, and Cauchy mutation to enhance search capability and improve global convergence. By utilizing the improved sparrow search algorithm, an optimal resource allocation strategy is derived, resulting in reduced processing latency for subtasks. The simulation results show that the performance of the proposed algorithm is better than other baseline schemes and can improve the processing success rate of applications. [ABSTRACT FROM AUTHOR]

New versions of HTTP protocols have been developed to overcome many of the limitations of the original HTTP/1.1 protocol and its underlying transport mechanism over TCP. In this paper, we investigated the performance of modern Internet protocols such as HTTP/2 over TCP and HTTP/3 over QUIC in high-latency satellite links. The goal was to uncover the interaction of the new features of HTTP such as parallel streams and optimized security handshake with modern congestion control algorithms such as CUBIC and BBR over high-latency links. An experimental satellite network emulation testbed was developed for the evaluation. The study analyzed several user-level web performance metrics such as average page load time, First Contentful Paint and Largest Contentful Paint. The results indicate an overhead problem with HTTP/3 that becomes more significant when using a loss-based congestion control algorithm such as CUBIC which is widely used on the Internet. Also, the results highlight the significance of the web page structure and how objects are distributed in it. Among the various Internet protocols evaluated, the results show that HTTP/3 over QUIC will perform better by an average of 35% than HTTP/2 over TCP in satellites links specifically with a more aggressive congestion algorithm such as BBR. This can be attributed to the non-blocking stream multiplexing feature of QUIC and the reduced TLS handshake of HTTP/3. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically study the achievable capacity of orthogonal and non-orthogonal multiple access (OMA and NOMA) schemes in supporting downlink satellite communication networks. Considering that various satellite applications have different delay quality-of-service (QoS) requirements, the concept of effective capacity is introduced as a delay-guaranteed capacity metric to represent users' various delay requirements. Specifically, the analytical expressions of effective capacities for each user achieved with the NOMA and OMA schemes are first studied. Then, approximated effective capacities achieved in some special cases, exact closed-form expressions of users' achievable effective capacity, and the capacity difference between NOMA and OMA schemes are derived. Simulation results are finally provided to validate the theoretical analysis and show the suitable limitations of the NOMA and OMA schemes, such as the NOMA scheme is more suitable for users with better channel quality when transmit signal-to-noise (SNR) is relatively large, while it is suitable for users with worse link gain when transmit SNR is relatively small. Moreover, the influences of delay requirements and key parameters on user selection strategy and system performance are also shown in the simulations. [ABSTRACT FROM AUTHOR]

Low Earth Orbit (LEO) Satellite Network (SatNet) with their mega-constellations are expected to play a key role in providing ubiquitous Internet and communications services in the future. LEO SatNets will provide wide-area coverage and support service availability, continuity, and scalability. To support the integration of SatNets and terrestrial Fifth Generation (5G) networks and beyond, the satellite communication industry has become increasingly involved with the 3rd Generation Partnership Project (3GPP) standardization activities for 5G. In this work, we review the 3GPP standardization activities for the integration of SatNets in 5G and beyond. The 3GPP use cases of SatNets are highlighted and potential requirements to realize them are summarized as well. The impacted areas of New Radio (NR) are discussed with some potential solutions. The foreseen requirements for the management and orchestration of SatNets within 5G are described. Future standardization directions are discussed to support the full integration of SatNets in Sixth Generation (6G) with the goal of ubiquitous global connectivity.

Future integrated terrestrial, aerial, and space networks will involve thousands of low-Earth-orbit (LEO) satellites, which will form a network of mega-constellations. These mega-constellations will play a significant role in providing communication and Internet services anywhere, at any time, and for everything. Due to the large scale and highly dynamic nature of future LEO satellite networks (SatNets), their management will be a complicated process, especially the aspect of mobility management and its two components: location management and handover management. In this article, we present a comprehensive and critical review of the state-of-the-art research in location management for LEO SatNets. First, we give an overview of the Internet Engineering Task Force (IETF) mobility management standards (e.g., Mobile IPv6 and Proxy Mobile IPv6) and discuss the limitations of their location management techniques for future LEO SatNets. We highlight the mobility characteristics of future LEO SatNets and their challenging features, and we describe two unprecedented future location management scenarios. A taxonomy of existing location management solutions for LEO SatNets is also presented with solutions classified according to three approaches. The “Issues to consider” section draws attention to critical points related to each of the reviewed approaches that should be considered in future LEO SatNets location management. To identify the research gaps, the current state of LEO SatNets location management is summarized. Noteworthy future research directions are recommended. The article provides a road map for researchers and industry to shape the future of location management for LEO SatNets.

Satellite edge computing has attracted the attention of many scholars, but the limited resources of satellite networks bring great difficulties to the processing of edge-computing-dependent tasks. Therefore, under the system model of the satellite-terrestrial joint network architecture, this paper proposes an efficient scheduling strategy based on task degrees and a resource allocation strategy based on the improved sparrow search algorithm, aiming at the low success rate of application processing caused by the dependency between tasks, limited resources, and unreasonable resource allocation in the satellite edge network, which leads to the decline in user experience. The scheduling strategy determines the processing order of tasks by selecting subtasks with an in-degree of 0 each time. The improved sparrow search algorithm incorporates opposition-based learning, random search mechanisms, and Cauchy mutation to enhance search capability and improve global convergence. By utilizing the improved sparrow search algorithm, an optimal resource allocation strategy is derived, resulting in reduced processing latency for subtasks. The simulation results show that the performance of the proposed algorithm is better than other baseline schemes and can improve the processing success rate of applications.

Introduction Television and satellite channels, in addition to other forms of social media, have facilitated the rapid and widespread transmission of foreign lifestyles, social relationships, culture, art, beliefs, and values to Iranian society. As a result, satellite networks with their diverse capabilities have become capable of affecting all aspects of human life, particularly altering the daily lives and lifestyle choices of people from all sectors of society, particularly the youth. Thus, the aim of this study is to evaluate the effectiveness of Persian-language satellite networks in shaping the lifestyles of young people and from the perspective of Bourdieu's indicators by means of the data envelopment analysis model. Materials and Methods The research method employed is case-driven and context-specific. In order to implement the model, a library study was initially conducted to evaluate the impact of TV and satellite networks on youth lifestyles according to Bourdieu's perspective. Based on the opinions of experts in the field, the input and output indices of the study were determined. To account for the non-deterministic nature of many indices, the Rough DEA model was used, which converts non-deterministic variables to intervals using the "α" level and results in an interval data envelopment analysis model. Using the MRA ranking method, the efficient intervals were ranked and compared. Then the efficiency of each evaluated network was determined through a sensitivity analysis performed at different "α" levels. Finally, each of the networks was ranked. Discussion and Results Based on the data collected and analyzed, the "Man o To" network was found to have the greatest influence on the lifestyles of young people. The "Persian BBC" network ranked second, followed by the "Nasim network" in third place, and finally, the "GEM" network placed last. These results suggest that there are significant differences in the impact of satellite networks on the lifestyles of young people, and that the "Man o To" network has been the most effective at shaping the lifestyle choices of this demographic. Conclusions Based on the research findings, it is recommended that the administrators of domestic Persian-language satellite media produce high-quality and appealing content in the fields of information, news, entertainment, and educational programming. This strategy will help boost the lifestyle indicators among the youth. Additionally, it is suggested that individuals with greater social capital and trust consume media resources from these aforementioned fields.

Abstract The dynamic weather condition is a major concern for optimum channel utilization in recent times, especially at higher frequencies with larger bandwidth for 5G applications. Over the years, rain-induced attenuation among the hydrometeors has been linked as the major cause of signal impairment especially at the frequency, f ≥ 10 GHz. However, when f > 18 GHz, the significant impact of other hydrometeors; cloud/fog, and scintillation increases tremendously, especially for Low Earth Orbit, LEO satellites. LEO satellites find applications in fibre optics technology, scientific research, remote sensing, surveillance, meteorology, satellite imaging, and other applications. In this paper, the assessment of combined impairments based on 5-year (2012-2016) data has been carried out and a dynamic adaptive intelligent scheme (DAIS) has been adopted to achieve a good quality of service along the satellite channels operating at Ku-V band frequencies over five stations representing different climatic regions in Nigeria namely: Port Harcourt (PH), Akure, Ilorin, Zaria, and Kano. The proposed DAIS based on fuzzy logic was able to achieve a significant reduction in the transmitting power by about 70% and SNR by 50% across the frequencies considered without altering the information content of the downlink parameters, thereby improving the QoS significantly and adhere to Customer Service Level Agreements (CSLAs) irrespective of the weather dynamics. The overall results show that the adaptive intelligent techniques can effectively fix signal links under the dynamic weather conditions for both satellite and wireless networks in this region. Information from the results is timely because it will serve as the bedrock for the newly launched transformation to the digital video broadcasting (DVB) system in Nigeria for effective service delivery.

In recent years, the adoption of innovative technologies in maritime transport and logistics systems has become a key aspect towards their development and growth, especially due to the complex and heterogeneous nature of the maritime environment. On the other hand, Internet of Things (IoT) solutions are gaining importance in the shipping industry thanks to the huge number of distributed cameras and sensors in modern ships, cargoes and sea ports, which can be exploited to improve safety, costs and productivity. This paper presents an experimental evaluation of a maritime platform, which enables a wide range of 5G-based services in the context of logistics and maritime transportation. Its core is a Narrow Band (NB)-IoT framework used to run massive IoT services on top of a hybrid terrestrial–satellite network and feed a OneM2M platform with significant data on maritime transport to develop high-level and value-added logistic applications on top. Among the many different services that could be provided by the maritime platform, we focus on the cargo-ship container tracking use case through the Global Tracking System, which allows for continuous container monitoring all over the seas in a port-to-port service scenario. The results of the experimental tests illustrate the capacity of the platform in managing the high number of messages transmitted by the container tracking devices (i.e., more than 3000) and its efficiency in limiting the average maximum latency and packet loss below 5.5 s and 0.9%, respectively.

With the rapid development of 5G and the Internet of Things, satellite networks are emerging as an indispensable part of realizing wide-area coverage. The growth of the constellation of low-orbit satellites makes it possible to deploy edge computing services in satellite networks. This is, however, challenging due to the topological dynamics and limited resources of satellite networks. To improve the performance of edge computing in a satellite network, we propose a satellite network task deployment method based on SDN (software-defined network) and ICN (information-centric network). In this method, based on the full analysis of satellite network resources, a mission deployment model of a low-orbit satellite network is established. The genetic algorithm is then used to solve the proposed method. Experiments confirm that this method can effectively reduce the response delay of the tasks and the network traffic caused by task processing. [ABSTRACT FROM AUTHOR]

Satellite networks (SNs) are heterogeneous networks composed of typical functional domains, such as communication domains, observation domains, etc. Since the resources are independent among domains, and are highly dynamic with the movement of satellites, it is extremely difficult to capture the potential interaction relationship among various resources, even less to realize the coordinated scheduling of cross-domain resources in large-scale SNs. Motivated by these factors, we firstly propose a multi-aspect expanded hypergraph (MAEH) to accurately depict the Spatio-temporal features of resources in various domains as well as functional property, which is presented by different aspects. Particularly, the “aspect” can involve a group of resources with a similar feature in a hyperedge rather than a bilateral relationship between two individuals, thus the MAEH can dramatically reduce the redundant connections. By exploiting the MAEH, we model the multi-domain resource allocation problem in the form of mixed-integer linear programming to maximize the completed tasks. Through the topological nested characteristic of the MAEH, we propose a two-stage scheme to accomplish the resource allocation rapidly with lower computational complexity and to improve the resource utilization ratio efficiently. Simulation results validate that compared with the optimal performance, the executive time of the proposed scheme is average fivefold less under 4% extra communication resource cost. Besides, the resource utilization ratio improves over 15% by cross-domain collaboration. [ABSTRACT FROM AUTHOR]

A random access framework based on random interleaving multiplexing (RIM) is proposed to further improve throughput for internet of things in satellite networks, which resort to the state-of-art physical layer techniques that can resolve multiple packet collisions issue. The interleavers are randomly selected by active devices from a set of available interleavers, which are used to differentiate signals of different devices sharing a subframe that consists of multiple time slots. The message passing detector (MPD) is utilized to decode collided packets. By means of transmission diversity and interference cancellation, the proposed scheme can be linked with the irregular repetition slotted ALOHA (IRSA), the RIM-IRSA protocol is proposed. The analysis of packet loss ratio (PLR) of the RIM-IRSA is given by using the density evolution method, and the optimal degree distributions are given. Simulation results show that the RIM-IRSA outperforms traditional IRSA protocol.

Modern satellite VSAT networks can be applied not only to provide satellite radio and television broadcasting, but also to other domains, such as a two-way Internet access. For this objective it has become necessary to develop appropriate standards and data transmission techniques. An unquestionable advantage of satellite systems is reception range, which translates into possibility of building networks in almost any place on Earth. Depending on the application, such networks can use many topologies. The aim of the article is to review distributed information in this area, as well as to determine the directions of development of the next generation VSAT networks. For this purpose, the literature review has been provided, with due regard to the IEEE Xplore digital library databases, and supported by practical examples.

Recent years have witnessed a growing interest in Internet access from space assisted by low earth orbit (LEO) satellite networks. In the domain of the last-mile access for the Internet of Vehicles (IoV), hybrid free-space optical (FSO)/radio-frequency (RF) communication has recently attracted worldwide research efforts. While the transmission control protocol (TCP) is the most widely deployed transport protocol on the Internet, its performance in the error-prone environment of LEO satellite-assisted hybrid FSO/RF vehicular networks is not well understood. This paper develops a comprehensive analytical model based on the cross-layer approach for TCP performance, considering the FSO and RF satellite fading channels, modeled by the Gamma-Gamma and Nakagami- $m$ distributions, respectively. The error-control solutions, including the Reed-Solomon (RS) code and Selective repeat automatic repeat request (SR-ARQ), are also employed. Numerical results quantitatively demonstrate the impact of transmission errors at last-mile links and different parameters/settings of error-control solutions on the TCP performance. The paper also supports the selection of proper TCP variants for the considered networks.

The current research status of SDN-based satellite communication networks was investigated, the SDN-based satellite communication network architecture and related key technical solutions was introduced and discussed; The opportunities and challenges faced by SDN-based satellite networks were discussed.

The ocean is a huge saltwater body that is different from terrestrial environments in terms of deployment circumstance, weather conditions, and user distributions. Therefore, it is difficult to apply terrestrial net-working technologies directly in oceans. The cost-effectiveness of satellites is still an issue to be addressed to increase their popularity due to their high cost in construction, launching, and maintenance and high deployment risks. Such situations stimulate many research efforts on networking technologies in the ocean space consisting of coastline, water surface, sky, and underwater. This article conducts a comprehensive survey on the related issues through reviewing the networking environments and communication networks already operating in the ocean space as well as ongoing R&D activities and results reported in the literature. These systems include coastal networks, water surface networks, sky networks, and underwater networks, which are reviewed and discussed along with summaries on the related topics and research issues necessary for further studies. This article, taking into account maritime communication networks and underwater networking together, aims to provide the reader with an overview on the state of the art and corresponding challenging issues for networking in the ocean space. [ABSTRACT FROM AUTHOR]

Earth Observation applications are demanding higher spatial resolution and shorter revisit times than existing systems, which can be met by ad-hoc constellations of Federated Satellite Systems. These systems are distributed satellite architectures which rely on the collaboration between satellites that share unused resources, such as memory storage, computing capabilities, or downlink opportunities. In the same context, the Internet of Satellites paradigm expands the federation concept to a multi-hop scenario, without predefining a particular satellite system architecture, and deploying temporal satellite networks. The basis of both concepts is the offer of unused satellite resources as services. Therefore, it is necessary that satellites notify their availability to the other satellites that compose the system. This work presents a novel Opportunistic Service Availability Dissemination Protocol, which allows a satellite to publish an available service to be consumed by others. Details of the protocol behavior, and packet formats are presented as part of the protocol definition. The protocol has been verified in a realistic scenario composed of Earth Observation satellites, and the Telesat mega-constellation as network backbone. The achieved results demonstrate the benefits of using a protocol as the proposed one, which in some cases even doubles the amount of data that can be downloaded. To the best of our knowledge, this proposal is the first protocol that allows deploying opportunistic services for Federated Satellite Systems.

In this article, a novel random pre-coding (RPC) based random access (RA) scheme is proposed to improve the system performance in the Internet of Things-oriented satellite networks. In this scheme, each device randomly selects a non-orthogonal multi-level complex sequence from a pre-defined pre-coding sequence set to pre-code the transmitted packets in a sub-frame, by which multiple superimposed packets in the sub-frame can be successfully decoded by using the minimum mean squared error (MMSE) based successive interference cancellation (SIC) detection algorithm. Besides, by combining the proposed RPC with the existing contention resolution diversity slotted ALOHA (CRDSA) scheme, which the RPC-CRDSA scheme is generated. The SIC processing should be carried out across sub-frames to remove the received signals that are already recovered, which can further significantly improve the system throughput. The performance of the RPC-RA scheme is evaluated via both theoretical analysis and computer simulation. The collision probabilities of both preamble and pre-coding sequences and an upper bound of throughput are derived, respectively. Simulation results show that the peak normalized throughput of RPC-CRDSA with the pre-coding sequence length L = 8 can reach 1.87 bits/symbol, which largely outperforms traditional schemes.

The emergence of Internet of Things (IoT) and high throughput satellite communication networks enables the capability of anytime, anywhere environment monitoring and sensing. A key challenge of satellite-based IoT is to enhance spectrum and energy efficiency so as to meet the ever-increasing demand for satellite bandwidth and dynamic access of a massive number of IoT terminals. In this paper, we propose a novel power control algorithm for IoT terminals being deployed in satellite-based IoT systems where some terrestrial base station is available to acquire IoT devices' information as well as to perform resource management. We adopted the Poisson point process (PPP) theory to formulate the model for this power optimization problem. The PPP theory is applied to evaluate the distance distribution of random IoT devices in this satellite-based networks. Optimal power control scheme can be obtained by taking into consideration user distribution and signal interference plus noise ratio (SINR) demand for various IoT terminals. In addition, due to the complexity of the objective function of power control deduced by the PPP theory, we utilize the pattern search method to identify an optimal solution in global area. Furthermore, we provide numerical results from various perspectives including user rates and energy efficiency to testify the performances of our power proposal.

Upcoming Low Earth Orbit Satellite Networks will provide low-latency and high downlink capacity necessary for future broadband communications and Earth Observation missions. This architecture was proposed at the beginning of the 90's, although it has just recently re-gained popularity thanks to the so-called Mega-Constellations. This network is composed of satellites that have Inter-Satellite Links (ISL) to communicate between them. Due to the satellite motion, an ISL is a temporal contact between two satellites characterized by a lifetime in which the communication remains feasible. The determination of a route between distant satellites is a challenging problem in this context. However, the satellite follows a well-known deterministic orbit trajectory, being feasible the prediction of its position by propagating a trajectory model over time. The Contact Graph Routing protocol uses this feature to determine the evolution of the routes by pre-computing on-ground a planning of the satellite contacts. This centralized ground-dependent solution cannot be directly applied in the Internet of Satellites paradigm, which proposes the autonomous deployment of heterogeneous satellite networks without pre-assuming any specific satellite system architecture. Following this concept, the present work proposes a distributed algorithm by which a satellite predicts neighbor contacts, and generates a global contact plan without trajectory propagation. To achieve this solution, an ISL has been modeled as a “close approach” between two satellites, which is characterized by their relative motion. The present work details the predictive algorithm, and evaluates its performance in two scenarios with a hybrid satellite constellation and a mega-constellation.

Satellites are the transmission medium for providing connectivity and building global, continental, or regional networks around the world (satellite operators effectively use satellites to support Internet traffic), and point-to-point connections are also possible. In practical use, there are combinations of VSAT networks with terrestrial wireless extensions, allowing end users to increase the capabilities offered via satellite. This paper provides selected information on broadband satellite networks using VSAT technology, including available protocols and transmission platforms. The aim of the article is also to present the chosen technical aspects of satellite networks working with the usage of VSAT technology.

The dynamic weather condition is a major concern for optimum channel utilization in recent times, especially at higher frequencies with larger bandwidth for 5G applications. Over the years, rain-induced attenuation among the hydrometeors has been linked as the major cause of signal impairment especially at the frequency, f > 10 GHz. However, when f > 18 GHz, the significant impact of other hydrometeors; cloud/fog, and scintillation increases tremendously, especially for Low Earth Orbit, LEO satellites. LEO satellites find applications in fibre optics technology, scientific research, remote sensing, surveillance, meteorology, satellite imaging, and other applications. In this paper, the assessment of combined impairments based on 5-year (2012-2016) data has been carried out and a dynamic adaptive intelligent scheme (DAIS) has been adopted to achieve a good quality of service along the satellite channels operating at Ku-V band frequencies over five stations representing different climatic regions in Nigeria namely: Port Harcourt (PH), Akure, Ilorin, Zaria, and Kano. The proposed DAIS based on fuzzy logic was able to achieve a significant reduction in the transmitting power by about 70% and SNR by 50% across the frequencies considered without altering the information content of the downlink parameters, thereby improving the QoS significantly and adhere to Customer Service Level Agreements (CSLAs) irrespective of the weather dynamics. The overall results show that the adaptive intelligent techniques can effectively fix signal links under the dynamic weather conditions for both satellite and wireless networks in this region. Information from the results is timely because it will serve as the bedrock for the newly launched transformation to the digital video broadcasting (DVB) system in Nigeria for effective service delivery. [ABSTRACT FROM AUTHOR]

The utilization of extremely high-frequency (EHF) bands can achieve very high throughput in satellite networks (SatNets). Nevertheless, the severe rain attenuation at EHF bands imposes strict limitations on the system availability. Smart gateway diversity (SGD) is considered indispensable in order to guarantee the required availability with reasonable cost. In this context, we examine a load-sharing SGD (LS-SGD) architecture, which has been recently proposed in the literature. For this diversity scheme, we define the system outage probability (SOP) using a rigorous probabilistic analysis based on the Poisson binomial distribution, and taking into consideration the traffic demand as well as the gateway (GW) capacity. Furthermore, we provide several methods for the exact and approximate calculation of SOP. As concerns the exact computation of SOP, a closed-form expression and an efficient algorithm based on a recursive formula are given, both with quadratic worst-case complexity in the number of GWs. Finally, the proposed approximation methods include well-known probability distributions (binomial, Poisson, normal) and a Chernoff bound. According to the numerical results, binomial and Poisson distributions are by far the most accurate approximation methods. [ABSTRACT FROM AUTHOR]

The incorporation of the cognitive radio (CR) technology as a spectrum management tool in satellite communication has attracted considerable research attention because the CR allows the coexistence of the primary and secondary networks using the same resources. In this paper, satellites and their users are considered as a primary network, and the terrestrial base stations (BSs) and their users are considered as a secondary network. Besides, it is considered that terrestrial users cause interference to satellite users due to technical and environmental constraints. This interference reduces satellite users' satisfaction with downloads rate. In such a cognitive satellite network environment, content placement may also cause a decrease in user satisfaction. The successful download probability (SDP) is analyzed in this work based on different terrestrial user density. To utilize the satellite cache resources effectively, we propose two transmission strategies based on the terrestrial user density, namely, the multi-point cooperative transmission strategy (CT) and the parallel transmission strategy (PT). In addition, based on the cache service probability we determine the ratio of content distribution most popular content (MPC) and general popular content (GPC) and optimize the content placement process using the utility function in CT mode. Through computer simulation, we give numerical results of our method. The obtained numerical results show that the proposed strategies are effective in content placement.

Satellite communication networks are expected to be indispensable as part of an integrated complement for the upcoming 5G networks since they can provide the most comprehensive coverage and reliable connection for areas where are economically unviable and/or difficult to deploy terrestrial infrastructures. Meanwhile, the power-domain non-orthogonal multiple access (NOMA), which can serve multiple users simultaneously within the same time/frequency block, has been viewed as another promising strategy used in the 5G network to provide high spectral efficiency and resource utilization. In this paper, we introduce a general overview of the application of the NOMA to various satellite architectures for the benefits of meeting the availability, coverage, and efficiency requirements targeted by the 5G. The fundamental and ubiquitous features of satellite link budget are first reviewed. Then, the advantage and benefit of introducing the NOMA scheme in various satellite architectures, such as conventional downlink/uplink satellite networks, cognitive satellite terrestrial networks, and cooperative satellite networks with satellite/terrestrial relays, are provided, along with the motivation and research methodology for each scenario. Finally, this paper reviews the potential directions for future research.

Information, as one of the important factors of armed conflicts, greatly influences the physiognomy, the direction and the speed of the development of contemporary conflicts. It expresses the availability of knowledge and data necessary for successful command and control at all levels. Its availability reduces the uncertainty in military activity and enables a better assessment of the situation, as well as making relevant decisions in real time. In the paper, the Telecommunications and Information System (TkIS) of the Serbian Armed Forces (SAF) is looked at from several aspects, and the issue of the need for improvement of the existing system, imposed by constant development of information technologies, is being updated. The concept, purpose, structure and level of development of the TkIS are dealt with in the paper, particularly the level of development of the SAF TkIS and its cause-effect relation with the defense of the Republic of Serbia, with a focus on military defense. The aim of this paper is to examine the impact of the Serbian Armed Forces telecommunications and information system on the defense of the Republic of Serbia with the emphasis on military defense, and to point out the need for continuous improvement of the TkIS and continuous education, i.e. adequate and timely training of the personnel for its use for military defense. The importance of the work is in the analyzed state of the Serbian Telecommunications and Information System in relation to the needs of the military defense of the Republic of Serbia in the context of contemporary security challenges. / Информация, как один из важных факторов войны, оказывает большое влияние на форму, направление и скорость развития современных конфликтов. Она подразумевает владение знаниями и данными, необходимыми для успешного командования и управления на всех уровнях. Владение информацией снижает степень неизвестности в военном деле и способствует лучшей оценке ситуации, а также принятию соответствующих решений в реальном времени. В данной статье с разных аспектов представлена телекоммуникационная система (ТкИС) Вооруженных сил Республики Сербия и открывается вопрос о необходимости совершенствования существующей системы, что в свою очередь требует постоянное развитие информационных технологий. В работе описаны понятие, назначение, применение, структура и достигнутый уровень развития ТкИС. С особым вниманием были проанализированы уровень развития ТкИС ВС РС и причинно-следственные связи с обороной Республики Сербия, с упором на военную оборону. Цель данной работы заключается в представлении того, каким образом информационная и телекоммуникационная системы Вооруженных сил Республики Сербия могут влиять на оборону Республики Сербия, особенно на военную оборону, нам также хотелось обратить внимание на необходимость постоянного совершенствования и развития ТкИС, то есть, в организации соответствующей и своевременной подготовки персонала для нужд военной обороны. Значимость данной работы заключается в проведенном анализе состояния телекоммуникационной и информационной систем Вооруженных сил Республики Сербия и представлении реальных нужд военной обороны Республики Сербия в контексте современных вызовов безопасности. / Informacija, kao jedan od značajnih faktora oružane borbe, u velikoj meri utiče na fizionomiju, pravac i brzinu razvoja savremenih sukoba. Ona izražava raspoloživost znanjima i podacima potrebnim za uspešno komandovanje i rukovođenje na svim nivoima. Njenom raspoloživošću smanjuje se neizvesnost u vojnoj delatnosti i omogućava se bolja procena situacije, kao i donošenje svrsishodnih odluka u realnom vremenu. U radu se sa više aspekata sagledava telekomunikaciono-informacioni sistem (TkIS) Vojske Srbije i aktuelizuje pitanje potrebe unapređenja postojećeg sistema koje nameće neprestani razvoj informacionih tehnologija. U radu se navode pojam, namena, struktura i dostignuti stepen razvoja TkIS. Detaljno su analizirani stepen razvoja TkIS VS i uzročno-posledične veze sa odbranom Republike Srbije, sa težištem na vojnoj odbrani. Cilj rada jeste da se sagleda uticaj telekomunikaciono-informacionog sistema Vojske Srbije na odbranu Republike Srbije sa težištem na vojnoj odbrani, kao i da se ukaže na potrebu neprestanog usavršavanja TkIS i kontinuirane edukacije, odnosno adekvatne i pravovremene obuke kadra za njihovo korišćenje u vojnoodbrambene svrhe. Značaj rada ogleda se u analizi stanja telekomunikaciono-informacionog sistema Vojske Srbije u odnosu na potrebe vojne odbrane Republike Srbije u kontekstu savremenih bezbednosnih izazova.

During a high-speed movement, the satellites are connected intermittently, so the queue length becomes larger and a cache overflow appears. In this paper, the abundant storage resources of the multilayered satellite network (MLSN) are used to avoid the packet loss caused by a cache overflow of the Low Earth Orbit (LEO) satellites. However, due to the limited storage space of the Geostationary Earth Orbit (GEO) satellites, an effective load balance scheme which addresses two problems: LEO satellites competition in a non-cooperative fashion and content popularity utilization, is needed. Therefore, we propose a load balancing scheme based on the Stackelberg game, containing Members of a Game Algorithm and Distributed Cache Price Bargaining Algorithm. In addition, a storage technology based on content popularity (Popularity Matching Algorithm) is introduced. The numerical results show that the proposed methods are effective in pricing, cache resource allocation of GEO satellites, and load balancing of LEO satellites.

Satellite networks have the characteristics of long transmission delay, high bit error rate (BER), and asymmetric wide band, which seriously influence the performance of traditional TCP/IP networks. In order to adapt to long delay and high BER of satellite networks, a transmission control algorithm was proposed in this study. The amount of data transmission was enhanced to fill the high bandwidth-delay product of satellite links. The transmission factor was used to estimate available bandwidth in slow start. The reason for data loss was evaluated by the data backlog value in congestion avoidance. In this way, the threshold was increased in fast recovery, and the data transmission was improved in a short time. Moreover, the value of the congestion window in slow start and congestion avoidance was analyzed. And the threshold was adjusted by different network conditions. Results demonstrate that the proposed algorithm effectively improves the throughput of satellite links by 57.14% compared with TCP New Reno and also distinguishes different data losses. These findings indicate the transmission mechanism can take lower download response time. The proposed algorithm provides a good prospect to improve the transmission performance of satellite networks. [ABSTRACT FROM AUTHOR]

An enhanced irregular repetition slotted ALOHA (IRSA) protocol is proposed by using polarization characteristic of satellite link and MIMO detection in low earth orbit (LEO) satellite networks, which is dubbed polarized MIMO IRSA (PM-IRSA). In the proposed scheme, one or two packets in one slot can be decoded by employing polarized MIMO detection, and more than two collided packets in multiple slots which can construct the virtual MIMO model can be decoded by the MIMO detection algorithm. The performance of the proposed scheme is analyzed with the density evolution (DE) approach and the degree distribution is optimized to maximize the system throughput by using a differential evolution. Numerical results certify our analysis and show that the normalized throughput of the proposed PM-IRSA can achieve 1.89 bits/symbol. [ABSTRACT FROM AUTHOR]

Due to the capability of simultaneously delivering the same information to multiple users, the multicast transmission has been widely applied over the satellite networks. Furthermore, more and more information needs to ensure the transmission delay within a predefined bound. However, the satellite networks possess the time-varying characteristics and limited energy, which causes challenges for the low delay multicast design. In this paper, we investigate the energy-efficient delay-bounded (EEDB) multicast problem to accomplish the multicast transmission within the given delay bound, but to consume energy as less as possible. Specially, with the help of the time-expanded graph (TEG), we construct the multicast time-expanded graph (MTEG) through introducing some auxiliary vertices and arcs to accurately depict the across-time multicast transmission and the “wireless multicast advantage”. Then, we formulate the EEDB multicast problem as one combinatorial optimization and propose an iterative heuristic algorithm to achieve the suboptimal multicast scheme. Simulation results are also presented to verify our proposed algorithm. [ABSTRACT FROM AUTHOR]

In this paper, we propose a spatial group based optimal uplink power control scheme to enhance the performance of random access (RA) in satellite networks. In the proposed scheme, satellite machine-type terminals (SMTs) are divided into multiple groups based on their spatial locations in a distributed fashion, and the target received power levels of SMTs are the same in the same group but different from group to group by means of uplink power control, which enables the received power diversity. The received power levels of SMTs in different groups are designed by taking into account their path losses, which effectively reduces the energy consumption of SMTs. The threshold based capture model at the gateway demodulator is adopted, and the packet loss ratio (PLR) based on this model is derived by using density evolution analysis. An optimization problem is formulated and solved to jointly find the optimal number of power levels and the optimal values of power levels, which maximizes the RA system throughput. Simulation results show that the proposed scheme can obtain considerable performance improvement with respect to the conventional schemes in terms of normalized throughput, PLR, and average energy consumption. [ABSTRACT FROM AUTHOR]

The space segment has been evolved from monolithic to distributed satellite systems. One of these distributed systems is called the federated satellite system (FSS) which aims at establishing a win-win collaboration between satellites to improve their mission performance by using the unused on-board resources. The FSS concept requires sporadic and direct communications between satellites, using inter satellite links. However, this point-to-point communication is temporal and thus it can break existent federations. Therefore, the conception of a multi-hop scenario needs to be addressed. This is the goal of the Internet of satellites (IoSat) paradigm which, as opposed to a common backbone, proposes the creation of a network using a peer-to-peer architecture. In particular, the same satellites take part of the network by establishing intermediate collaborations to deploy a FSS. This paradigm supposes a major challenge in terms of network definition and routing protocol. Therefore, this paper not only details the IoSat paradigm, but it also analyses the different satellite network models. Furthermore, it evaluates the routing protocol candidates that could be used to implement the IoSat paradigm.

The operational network of individual observation nodes project evaluated the benefits of applying distributed satellite system (DSS) architectures to Earth observation. One of its outcomes is the identification of Arctic services as top priority current user needs that require near-real-time observations. Using inter-satellite communications (ISC) capabilities, a federated satellite system (FSS) can establish a win-win collaboration between two spacecrafts to provide these services. However, as a FSS is established during the contact between two satellites, the service duration is limited. Therefore, the Internet of satellites (IoSat) paradigm promotes the use of multi-hop sporadic networks to deploy FSS. In this paper, the routing protocol (which identifies routes between a source-destination pair) becomes crucial. One of the most extended networks is the mobile ad-hoc network (MANET), in which nodes are constantly moving and changing the network topology. In principle, applying MANET technologies in the IoSat context would provide self-organization, self-configuration, and flexibility to satellite systems. The optimized linkstate routing (OLSR) protocol is the predominant solution in MANET, because it quickly reacts against topology changes. This paper aims at studying the benefits of using satellite networks with MANET solutions (e.g. OLSR) for polar satellite missions. The results presented in this article demonstrate that the access time is significantly improved, and thus these new Arctic services can be achieved.

Free Space Optical (FSO) networks, also known as optical wireless networks, have emerged as viable candidates for broadband wireless communications in the near future. The range of the potential application of FSO networks is extensive, from home to satellite. However, FSO networks have not been popularized because of insufficient availability and reliability. Researchers have focused on the problems in the physical layer in order to exploit the properties of wireless optical channels. However, recent technological developments with successful results make it practical to explore the advantages of the high bandwidth. Some researchers have begun to focus on the problems of network and upper layers in FSO networks. In this survey, we classify prospective global FSO networks into three subnetworks and give an account of them. We also present state-of-the-art research and discuss what kinds of challenges exist.