Future Satellite Communication Systems Research Articles

Architecting CubeSat constellations for messaging service, Part I

In today’s modern and globalized world, connectivity is a key factor for businesses, production facilities, sensor networks, and ordinary people. However, there are still populated areas which are not covered by ground-based telecommunications infrastructure. This is where telecommunication satellite constellations come in, as they can provide coverage to remote and uninhabited regions and fill existing connectivity gaps to ensure data transfer.LoRa is one of the technologies designed for data transmissions over long distances with low power consumption. Alongside with other technologies of the Low-Power Wide Area Network family, it is widely used for Internet of Things applications. LoRa chirp spread spectrum modulation is robust against the Doppler frequency shifts encountered in low earth orbits, and it has already been used in IoT satellite communications. Due to the low transmitted signal power, the achieved data rate is not high, making it a suitable technology for telecommunications payloads on CubeSat platforms for messaging services. As compared to existing traditional communication satellite systems, CubeSat constellations are low-cost and may offer an affordable connectivity service to developing regions.This study is divided in two parts. In Part I the demand model is built based on the population distribution not covered by cell towers. The LoRa link performance is analyzed, considering the impact of LoRa channel parameters variation, such as spreading factor and channel bandwidth, while satellite orbital height, transmission antenna beamwidth, and transmitter peak power have a direct impact on the payload mass. Among thousands of possible configurations, 73 feasible payload designs have been downselected. In Part II of the study, the satellite mass and the total system cost are estimated based on the payload parameters obtained. Messages transmission simulation via a constellation is conducted in order to identify optimal constellation architectures for messaging service, as well as the main drivers of the system economic profitability.The presented analysis results provide a deeper understanding of LoRa connectivity advantages and limitations together with the performance drivers, which will support the optimization of future LoRa-based satellite communication systems and other IoT satellite constellations.

Adversarial Autoencoder Empowered Joint Anomaly Detection and Signal Reconstruction From Sub-Nyquist Samples

Anomaly detection is an essential part of spectrum monitoring applications. Malicious users and malfunctioning nodes could be identified via anomaly detection methods. Meanwhile, the spectrum bands that would be utilized in future 6G or satellite communication system settings are going to be wider than ever. Acquiring Nyquist sampled data from such a spectrum would require components with a very high sampling rate. To monitor a wide spectrum, a compressive sensing recovery algorithm combined with a sub-sampling approach could accomplish the task with a lower hardware cost. To solve the anomaly detection problem using a sub-sampled data stream, a joint signal recovery and anomaly detection solution utilizing an adversarial autoencoder (AAE) structure are proposed in this article. An AAE is constructed via an autoencoder and a discriminator weaved together. The discriminator would guide the autoencoder to drive its extracted feature onto a designed feature space, while the autoencoder would provide a reconstruction of the original Nyquist sampled signal. The proposed AAE structure could learn the distribution of the signal from either labelled or unlabelled training data, enabling it to work on both supervised and unsupervised data sets. The proposed AAE has shown superior reconstruction and detection performance on very sparse sampling scenarios.

Optimization Design for Sparse Planar Array in Satellite Communications

The antenna is one of the key components of satellite communication load. To address the evolving requirements of future satellite communication systems, the sparse planar array has become an important device for transmitting and receiving electromagnetic waves in emerging antenna systems. The advantages of this technology include low cost, low system complexity, and robust anti-interference ability, which have attracted widespread attention within the industry. In this paper, we investigate an optimization design of sparse planar arrays in satellite communication scenarios. Firstly, we introduce the mathematical foundation of the array antennas and establish the optimization design model of the sparse planar array. Secondly, we analyze and compare the impact of different array layout methods on the sparse planar array antenna pattern, and then introduce the latest design trend of array material design. Thirdly, we review some classical optimization methods for optimizing sparse planar arrays and the recent research advancements in promising and novel methods. Lastly, on the basis of the present research status, we propose three future research directions and two critical challenges for optimal design of sparse planar arrays in satellite communication scenarios, which can facilitate the development and realization of array technology under future B5G and 6G wireless networks.

Multi-Satellite Beam Hopping Based on Load Balancing and Interference Avoidance for NGSO Satellite Communication Systems

Due to the non-uniform distribution of the ground traffic demand and the high mobility of non-geostationary orbit (NGSO) satellites, how to make full use of the limited beam resources to serve users flexibly and efficiently is a brand-new challenge for NGSO communication systems. In order to achieve efficient spectrum utilization, the combination of full frequency multiplexing and beam hopping is a major trend in future satellite communication systems. However, conventional beam hopping methods are mainly based on geostationary satellites, which do not take into account the interference between satellites. This paper proposes a multi-satellite beam hopping algorithm based on load balancing and interference avoidance, which takes advantage of the multiple coverage features in the NGSO constellation and avoids intra-satellite interference and inter-satellite interference by designing beam-hopping patterns with spatial isolation characteristics. In particular, we decompose the multi-satellite beam hopping problem into three sub-problems, which are the multi-satellite load balancing problem, the single-satellite beam hopping pattern design problem, and the multi-satellite interference avoidance problem. Simulation results demonstrate that the proposed method reduces the load gap among satellites by about 72.5% and the average traffic satisfaction rate can reach 81.4%. Besides, our method has the lowest unmet capacity compared with other benchmarks, achieving better offered-requested data match.

Detection of radio interference in the UHF amateur radio band with the Serpens satellite

High packet losses when uplinking commands to small satellites have been reported in the UHF amateur band (430–440 MHz) since late 2013. Measurements of the uplink radio environment have shown high levels of in-band interference in previous works, but public measurement results are limited. Average interference levels are usually measured over some time to build heat maps. In this paper, the analysis is focused on sustained interference over a 24 ms time window using a maximum-minimum method. New heat maps and interference power distributions over Europe, Africa, the Middle East and the Americas were obtained using this method on measurements from the Serpens satellite. One of the missions of Serpens was to test an in orbit store-and-forward communication system to exchange short messages with ground sensors for disaster monitoring. The satellite operators had difficulties commanding the satellite due to interference, causing bit errors in uplink packets. Interference power of up to −70 dBm was detected during in-orbit measurements over Europe and North America, while expected received power from the ground stations was not more than −80 dBm. High power space-object tracking radars on the ground operating in the 420–450 MHz band could be the cause, but further measurements are required to verify this. Characterizing this interference can help develop mitigation techniques for future satellite communication systems.

Distributed Optimal Random Access Scheme for Energy Harvesting Devices in Satellite Communication Networks.

This paper considers satellite communication networks where each satellite terminal is equipped with energy harvesting (EH) devices to supply energy continuously, and randomly transmits bursty packets to a geostationary satellite over a shared wireless channel. Packet replicas combined with a successive iteration cancellation scheme can reduce the negative impact of packet collisions but consume more energy. Hence, appropriate energy management policies are required to mitigate the adverse effect of energy outages. Although centralized access schemes can provide better performance on the networks’ throughput, they expend extra signallings to allocate the resources, which leads to non-negligible communication latencies, especially for the satellite communication networks. In order to reduce the communication overhead and delay, a distributed random access (RA) scheme considering the energy constraints is studied. Each EH satellite terminal (EH-ST) decides whether to transmit the packet and how many replicas are transmitted according to its local energy and EH rates to maximize the average long-term network throughput. Owing to the nonconvexity of this problem, we adopted a game theoretic method to approximate the optimal solution. By forcing all the EH-STs to employ the same policy, we characterized and proved the existence and uniqueness of the symmetric Nash equilibrium (NE) of the game. Moreover, an efficient algorithm is proposed to calculate the symmetric NE by combining a policy iteration algorithm and the bisection method. The performance of the proposed RA scheme was investigated via numerous simulations. Simulation results showed that the proposed RA scheme is applicable to the EH devices in the future low-cost interactive satellite communication system.

Thermal Effects on a 4.2 m Center-Fed Cassegrain Antenna Strut in the Alphasat Ka- and Q-/V-Band Aldo Paraboni Propagation Measurements

Large gateways of future satellite communications (Satcom) systems will likely operate at Q-/V-band frequencies (40–50 GHz) to take advantage of the larger available bandwidth. On the other hand, Q-/V-band Satcom systems suffer from highly variable propagation losses, which must be accurately assessed and modeled. The Alphasat Aldo Paraboni propagation experiment, conceived and realized by the Italian Space Agency (ASI), Rome, Italy, has been running since 2014 to carefully investigate the propagation effects in the Ka- and Q-band and, thus, to support the design of high-throughput systems and propagation impairment mitigation techniques. In the framework of this experiment, ASI deployed two large ground terminals (Cassegrain antenna with 4.2 m diameter) in Tito Scalo (South of Italy) and Spino d’Adda (North of Italy). This contribution investigates the effect of antenna strut elongation on propagation measurements, which causes an additional reduction of 1–2 dB in the received signal during sunny days.

Adaptive suppression of passive intermodulation in digital satellite transceivers

For the performance issues of satellite transceivers suffering passive intermodulation interference, a novel and effective digital suppression algorithm is presented in this paper. In contrast to analog approaches, digital passive intermodulation (PIM) suppression approaches can be easily reconfigured and therefore are highly attractive for future satellite communication systems. A simplified model of nonlinear distortion from passive microwave devices is established in consideration of the memory effect. The multiple high-order PIM products falling into the receiving band can be described as a bilinear predictor function. A suppression algorithm based on a bilinear polynomial decorrelated adaptive filter is proposed for baseband digital signal processing. In consideration of the time-varying characteristics of passive intermodulation, this algorithm can achieve the rapidness of online interference estimation and low complexity with less consumption of resources. Numerical simulation results show that the algorithm can effectively compensate the passive intermodulation interference, and achieve a high signal-to-interference ratio gain.

Ultrawideband SIW-Fed Lens Antenna

An ultrawideband K-/Ka-band lens antenna for future satellite communication systems is presented. It consists of an extended hemispherical dielectric lens that is fed by a square substrate-integrated waveguide (SIW) and therefore offers a low-cost alternative to horn antennas. The design procedure is explained, and the antenna performance is presented. A sophisticated test fixture is developed to excite the square SIW. The measured ${S}$ -parameters and far-field patterns validate the concept and exhibit more than 13 GHz bandwidth.

Prediction model of time diversity using Japan rain radar data

SummaryThe effects of rain attenuation on communication systems will become more pronounced in future satellite communication systems, especially with the planned use of the 21‐GHz band or higher‐frequency bands. Diversity techniques provide a solution to mitigate rain attenuation effects. This study proposes a time diversity technique, one such technique that is likely to demonstrate high effectiveness. To model the system, rainfall rate statistics are necessary, and reliability is improved as the amount of statistical data increases. This paper derives the cumulative distribution of the rainfall rate across Japan over 4 years using rain radar data from the automated meteorological data acquisition system and ground‐based rain radar network and evaluates the rainfall rate at 23 observation points across Japan. We carry out a performance evaluation for all locations within Japan to confirm the efficiency of the time diversity method. Finally, we propose prediction model of the time diversity gain for Japan and other significant parameter which is time correlation of rainfall rate that was found from the time diversity results for further investigation. Copyright © 2016 John Wiley & Sons, Ltd.

Expected Queue Delay of Resource Allocation Scheme Based on Traffic Prediction in Satellite Systems

The future satellite communication systems should be able to accommodate the integrated services with a variety of applications and fulfil the quality of service requirements. Regarding to the delay requirements for different types of traffic, a novel resource allocation scheme is proposed. It is seen that the resource is allocated to each satellite terminal based on the traffic prediction. The assigned capacities are partitioned with priority coefficient according to the maximum tolerance delay of different traffic. The algorithm’s performance is validated in simulation with different types of traffic. The proposed scheme is further compared with the existing ones, such as first-come first-serve, non-pre-emptive priority and pre-emptive resume priority. The theoretical analysis and simulation results show that new algorithm can efficiently improve the delay performance of multi-application and is easy to be implemented in satellite communication system.

C7 スケーラブルなアンテナ反射鏡面構造の構成法とその軽量化設計に関する研究(膜構造(2))

To realize the future advanced satellite communication system, a new design methodology for light-weight, huge-scale antenna reflector structures is investigated. The reflector structure consists of a metal mesh surface, a cable network structure (a system of cables) and a deployable frame stricture. The cable network structure forms the mesh surface into a parabolic shape. High-rigidity cables are employed as "the tension truss structure" to form a precise surface shape. Two important design issues, the cable rigidity and the surface edge shape, were considered in this paper. Relatively large deformation is allowed to the supporting frame structure. Thus a homologous design method was applied to design the supporting structure. As a result of the optimization procedure using a FEM model, the weight of the supporting structure can be effectively reduced. In addition, by constructing hierarchical module structures, the modular structures can show a self-similarity. We are expecting to obtain structural characteristics of a whole huge structure by testing a few basic modules. This scalable design methodology can expand the proposed light-weight design for a basic module to a huge scale antenna reflector structure. Effects of the hierarchical modules design were shown comparing an existing modular structure.

Analysis on Connectivity of Inter-Orbit-Links in a MEO/LEO Double-Layer Satellite Network

As an important scheme of future global mobile satellite communication systems to provide multimedia service, a Double-Layer Satellite Network (DLSN) with MEO satellites and LEO satellites is proposed. The Inter-Orbit-Links (IOLs) between layers is an essential factor, which affects the performances of the DLSN systems. Considering certain constellation parameters, the geometric characteristics of IOLs are described and the connectivity of MEO satellites and LEO satellites in the DLSN is analyzed. By computer simulation, the results show that IOLs should be selectively established according to certain parameters rather than the simple in-sight principle.

Performance evaluation of digital beamforming strategies for satellite communications

Smart antennas are becoming one of the promising technologies to meet the rapidly increasing demands for more capacity of satellite communication systems. A main component in a smart antenna system is beamforming. Because of the limitations of analog beamforming, digital beamforming will be employed in future satellite communication systems. We evaluate the performance of various digital beamforming strategies proposed in the literature for satellite communications: 1) single fixed beam/single user, 2) single fixed beam/multiple users, 3) single adaptive beam/single user, and 4) single Chebyshev dynamic beam/multiple users. Multiple criteria including coverage, system capacity, signal-to-interference-plus-noise ratio (SINR), and computation complexity are used to evaluate these satellite communication beamforming strategies. In particular, a Ka-band satellite communication system is used to address the various issues of these beamforming strategies. For the adaptive beamforming approach, subarray structure is used to obtain the weights of a large 2D antenna array, and a globally convergent recurrent neural network (RNN) is proposed to realize the adaptive beamforming algorithm in parallel. The new subarray-based neural beamforming algorithm can reduce the computation complexity greatly, and is more effective than the conventional least mean square (LMS) beamforming approach. It is shown that the single adaptive beam/single user approach has the highest system capacity.

A new opportunity for EHF propagation experiments: the EXPRESS campaign with the satellite STENTOR

AbstractSTENTOR is a collaborative programme between CNES, France Telecom, Alcatel Space and Astrium Space. The STENTOR satellite is planned to be launched in the autumn of 2001. Apart from the Ku‐band telecommunication payload designed to test active antennas and digital transponders, an EHF payload funded by DGA (Délégation Générale pour l'Armement=French Ministry of Defence) will be devoted to propagation and transmission experiments. The transmission mission uses a 44/20 GHz transparent repeater and is aimed to test new signal processing methods in the context of future military satellite telecommunication systems. The propagation mission will consist of two high‐frequency beacons, the first one at 20.7 GHz and the second one at 41.4 GHz with a European and an Equatorial coverage. The propagation experiment called EXperimentation of PRopagation in the EHF‐band from STENTOR Satellite (EXPRESS) will be devoted to the evaluation of the influence of propagation impairments on future satellite communication systems and will provide a new opportunity for EHF experimenters. The objective of this paper is to give the information available on this project. Copyright © 2001 John Wiley & Sons, Ltd.

A European strategy for future satellite communications systems

The paper shows the ESA ambition to transition from the adversarial role of a customer to the supportive role of a partner in the field of satellite communication systems.

The next generation of UK military satellite communication systems

UK military satellite communications systems are currently provided by the Skynet programme. The current generation is collectively known as Skynet 4, and is due to be replaced from 2003 by the next generation. CDA has been asked to conduct an operational research study to review the potential communications requirements of the Ministry of Defence (MoD) in the period 2003–2013, and assess what contribution could be made to them by the proposed future military satellite communications system. This paper discusses some of the political and technical issues surrounding the work carried out. Technically, the study looked at the dynamic loading of five different satellite options in three scenarios set in 2010. Each combination of scenario and satellite was modelled, and the results produced in terms of the chosen measures of effectiveness. The sensitivity of these results to various assumptions was tested to determine the robustness of the results. The scenarios included land, air and maritime operations. In an area where little or no analysis had previously been attempted (at least in the military context) in the UK, this ‘intervention’ succeeded in clarifying the main issues, and setting a course for future work.

Channel characterization and modeling for Ka-band very small aperture terminals

An increasing number of commercial applications are being promoted for future Ka-band satellite communication systems. Many of these systems will involve low-margin very small aperture terminals (VSATs). These systems are subject to important atmospheric propagation degradations that affect the quality of transmission and the link availability. The objective of this paper is to characterize the Ka-band channel and evaluate the performance degradation in VSATs resulting from atmospheric propagation, impairments. In particular microwave propagation through a turbulent atmosphere is discussed, and the statistical characterization and modeling of tropospheric scintillation is reviewed. Moreover, the paper extends the method proposed by Filip and Vilar (1990) for the long-term characterization and modeling of the combined effect of rain impairments and scintillation. Specifically, the increase in noise temperature during rain events is added to the Filip-Vilar model. This leads to a five-parameter global fading distribution that is used to predict typical Ka-band satellite link outage time, the mathematical formalism is illustrated by applying the method to the selected case of the Advanced Communications Technology Satellite (ACTS)-Georgia Tech experimental downlink. Numerical results confirm that both rain impairments and scintillation are important factors in the design of Ka-band VSAT systems.

Dopplerprofile für Kommunikationssatelliten

Future satellite communications systems are going to use orbiting satellites. Compared with the geostationary orbit such systems have some advantages like the smaller attenuation of free space or the shorter link delay. On the other hand the relative motion of the satellite and the ground station lead to Dopplers of the radio signals. This paper describes a program which is used to compute the instantaneous Doppler for any orbit and for any position of the ground station. The results of the program are summarized over the visibility region to Doppler profiles.

Copolar and cochannel interference from adjacent satellites during rain at 12 GHz

The authors report experimental results on copolar and cochannel interference from adjacent satellites during rain obtained by measuring simultaneous rain attenuations in the 12 GHz band in two convergent slant paths to receivers located in the Fucino plain (Italy) from the geostationary satellites SIRIO (15/spl deg/W) and OTS (10/spl deg/E) in 1978-1980. The results presented here are directly applicable to the design of actual TV satellite broadcasting systems and they can be extrapolated to higher frequencies to design future satellite communication systems.