Satellite Communication Links Research Articles

Fade Duration Analysis on a Ka-Band Link Operating in the Tropical Region

Communication systems are rapidly shifting towards higher frequencies due to congestion experienced at lower frequencies and the growing demand for higher data transmission rates within the network. However, it has been observed that as frequency increases, the susceptibility of the system to weather-related factors, particularly adverse weather conditions like rain, becomes more pronounced. This has raised significant concerns regarding the dependability of satellite communication links. This research investigates the dynamic characteristics of signal degradation caused by atmospheric effects, specifically focusing on the impact of rain fade. The study involves an analysis of fading duration using a year's worth of data extracted from Measat-5, operating at a beacon frequency of 20.199 GHz and positioned at an elevation angle of 68.8°. Such data is useful when developing a fade mitigation technique (FMT) that mitigates the disruptive effects caused by heavy rainfall, ultimately leading to an enhancement in both signal quality and overall signal availability.

LWARX: Lightweight ARX white-box cipher for satellite communications

Satellite communication links are vulnerable to attacks due to the lack of necessary security protection and can be considered as a white-box environment. In a white-box environment, cryptanalysts can access the intermediate processes of the algorithm and even manipulate or change the operating environment. Cryptanalysts can obtain keys or tamper with important data in many ways, which makes data communication unsecured. To solve the problem, a lightweight white-box cipher over Addition/Rotation/XOR (ARX) structure (LWARX) is proposed, which has 48 rounds of iterations through an unbalanced Feistel structure. On this basis, some of its linear operations are represented as lookup tables, and a secure external coding method is combined to complete the white-box implementation. The design and white-box implementation of the algorithm has resulted in a lighter and more rational structure, and still provides sufficient obfuscation of the data even when the S-box is discarded. The test results show that the average encryption speed is 37.53 Kbps, and average encryption speed after white-box implementation is 30.05 Kbps. And it can resist various attacks. The security of the algorithm against common attack methods such as differential analysis, linear analysis, code lifting attacks and BGE attacks is given in the paper with security analysis and specific values. This scheme balances computing efficiency and security, takes up little space, can be applied to scenarios with limited hardware and software resources, and broadens the application area of white-box cryptography.

Prediction of Q-Band Rain Attenuation Statistics Using Frequency Scaling Models for Temperate Location, Vigo, Spain

The prediction of yearly rain attenuation statistics at Q-band is made from Ka-band measurement for a temperate location, Vigo, Spain, using different frequency scaling models. The validity of the different frequency scaling models is tested for the present location by graphical comparison between measurement and prediction and also in terms of mean, standard deviation, and root mean square errors (RMSE). The Battesti model performs better compared to other existing frequency scaling models, RMSE is only 4.16% and 5.52% for the periods July 2016 to June 2017 and July 2017 to June 2018 respectively. The proposed new power law model increases the accuracy of the prediction for which the RMSE error is 1.09% and 2.17% less compared to the Battesti model for the periods July 2016 to June 2017 and July 2017 to June 2018, respectively. In predicting monthly statistics, the proposed model performs better compared to the Battesti model for all the months except December, January, and February. While predicting monthly statistics, for the proposed model, the maximum and minimum prediction errors are 18.50% and 0.39%, respectively. For the prediction of diurnal statistics, the proposed model performs better compared to the Battesti model with a very small prediction error, less than 4% for both days. The present study can be useful in the design and planning of satellite communication links in present or similar climatic regions for estimating rain attenuation at Q band or above, for which the experimental setup's cost is very high and requires a large receiver margin.

Time-division based integrated sensing, communication, and computing in integrated satellite-terrestrial networks

In this paper, we investigate time-division based framework for integrated sensing, communication, and computing in integrated satellite-terrestrial networks. We consider a scenario, where Internet-of-Things devices on the ground operate with sensing and communication in a time-division manner, and can process the sensing results locally, at the edge, or in the cloud via the satellite communication link. Based on the proposed framework, we formulate a multi-dimensional optimization problem to maximize the utility performance of sensing, communication, and computing abilities. After decomposing the original optimization problem into two subproblems, we first derive the closed-form solution of the optimal task partitioning strategy for terrestrial users and satellite users. Then, we develop the joint subframe allocation and task partitioning strategy to optimize the overall performance, by means of which the Pareto optimal solutions can be obtained along the Pareto frontier. Extensive simulations are provided to demonstrate the effectiveness of the proposed strategy, which is 10% to 60% superior compared with the benchmarks. Also, the trade-off between the multidimensional resource and multi-functional performance is analyzed from the perspective of network design.

A review of link budget analysis of satellite communication systems

At present, the link budget of satellite systems has become an essential part of the engineering design of satellite communication systems. Through the link budget, the performance of communication equipment and the loss of signal attenuation and interference during transmission can be comprehensively analysed, and the equipment resource configuration and device parameters can be continuously optimised to meet the user's communication capacity and quality requirements while leaving appropriate margins. This study aims to explore the link budget of the satellite system, study the parameters, channel characteristics and application of the satellite link budget, and provide a theoretical basis and practical reference for the design and performance optimisation of the satellite communication system. Firstly, the research background and significance of satellite communication links are introduced, and the characteristics and advantages of other communication systems are analysed and compared from multiple dimensions. The main factors affecting the link budget, such as path loss, related atmospheric attenuation, and carrier-to-noise ratio, were mainly discussed using the parameter estimation method and comparative analysis. Then, from the perspective of channel characteristics, the critical issues of satellite link budget, including signal-to-noise ratio, code rate and other factors, are discussed. Based on the above research, this paper summarises the performance evaluation of satellite communication systems and provides a reference for practical applications.

Realistic assessment of transport protocols performance over LEO-based communications

We study the performance exhibited by the transport protocols, Transport Control Protocol (TCP) and QUIC, over realistic satellite networks. We propose a novel methodology, which combines real implementation (exploiting virtualization techniques) and simulation, to carry out systematic and repetitive experiments. We modify the default operation of the ns-3 framework and we integrate the dynamism that characterizes satellite communication links, particularly Low Earth Orbit (LEO). We carry out a thorough assessment over different setups, changing the operating frequency band and packet buffer lengths. In addition, we ascertain the impact of using the multi-streaming feature that QUIC integrates. The results show that QUIC yields lower delays than TCP, although it might suffer from higher jitter in particular setups. In addition, the results evince that using multiple streams in QUIC does not yield a relevant gain for the default Round-Robin (RR) scheduler. We propose more appropriate scheduling strategies, which are able to yield better performances with unbalanced traffic. Even if the behavior of transport protocols over non-terrestrial-networks might not be always appropriate, the obtained results evince that QUIC can definitively bring benefits when compared to TCP. Furthermore, we have shown that optimal scheduling policies yields a fairer performance when using multiple flows, having unbalanced traffic loads.

Proof-of-Concept Real-Time Implementation of Interleavers for Optical Satellite Links

Ground-satellite optical links are a promising technology for increasing capacity and security over radio frequency links, while reducing weight and power consumption. However, atmospheric turbulence generates power fadings at the reception terminal. This effect can be mitigated by combining adaptive optics, forward error correction and data interleaving. While adaptive optics has been extensively studied, forward error correction together with long interleaving (e.g., multiple 10 ms) has not yet been demonstrated in this context. In this article, we present a proof of concept of an optical satellite uplink, precompensated by adaptive optics, which leverages a long interleaver in an external memory and operates at 10 Gbps with SFP+ transceivers. We account for the issues associated with real-time implementation and interfacing to a high-speed memory. To validate our proof of concept, we generate time-series for a typical ground to geostationary satellite communication link, using a field-validated simulator. Using these time series, we calculate the required interleaver time as a function of the launch power. Finally, we show the impact of different transmitter pupil diameters and of different wind speed profiles, on the interleaver duration.

Direction-of-Arrival (DoA) Estimation Performance for Satellite Applications in a Multipath Environment with Rician Fading and Spatial Correlation

Direction-of-arrival (DoA) estimation methods are highly versatile and find extensive applications in satellite communication. DoA methods are employed across a range of orbits, from low Earth orbits (LEO) to geostationary Earth orbits (GEO). They serve multiple applications, including altitude determination, geolocation and estimation accuracy, target localization, and relative and collaborative positioning. This paper provides a framework for modeling the DoA angle in satellite communications with respect to the elevation angle. The proposed approach employs a closed-form expression that incorporates various factors, such as the antenna boresight angle, satellite and Earth station positions, and the altitude parameters of the satellite stations. By leveraging this formulation, the work accurately calculates the Earth station’s elevation angle and effectively models the DoA angle. To the authors’ knowledge, this contribution is unique and has not been previously addressed in the available literature. Furthermore, this paper studies the impact of spatial correlation in the channel on well-known DoA estimation techniques. As a significant part of this contribution, the authors introduce a signal model incorporating correlation in satellite communication. Although selected studies have presented spatial signal correlation models in satellite communications to analyze the performance metrics, such as the bit error or symbol error probability, outage probability, and ergodic capacity, this work stands out by presenting and adapting a correlation model in the signal specifically for studying DoA estimations. Accordingly, this paper evaluates DoA estimation performance using root mean square error (RMSE) measurements for different satellite communication link conditions (uplink and downlink) through extensive Monte Carlo simulations. The simulation’s performance is evaluated by comparing it with the Cramer–Rao lower bound (CRLB) performance metric under additive white Gaussian noise (AWGN) conditions, i.e., thermal noise. The simulation results demonstrate that incorporating a spatial signal correlation model for DoA estimations significantly improves RMSE performance in satellite systems.

A New Reference Sample for High-Frequency Multipactor Testing

Multipactor (MP) is a high-power effect severely limiting the performance of satellite communication links. A reference sample is normally used in the experimental setups for MP testing in order to verify its correct operation. However, the low gaps required for high frequencies jeopardize the manufacturability of the devices traditionally used for this purpose. A new reference sample, based on a stepped-impedance resonator (SIR), is proposed in this letter. The key design considerations are also outlined. A prototype operating between 17 and 18 GHz has been manufactured and tested, proving the novel structure allows higher gaps, and is, thus, suitable for higher frequency bands.

Multi-domain united link adaptation technique in high-throughput satellite communication system

Under the condition of using the same frequency resources, the communication capacity of high-throughput satellites is tens or even hundreds of times higher than that of traditional satellites. Compared with traditional satellites, high-throughput satellites have a large capacity, high speed, and anti-interference characteristics. However, the high-throughput satellite communication link using Ku/Ka-band is vulnerable to weather factors such as rain attenuation, so the system should have a control mechanism to achieve fade countermeasures. The existing methods include transmission power adjustment, mod cod adaptive adjustment, carrier symbol rate adjustment, etc. In this paper, various technical means are comprehensively used to compare and analyze the effect of combined control and propose a multi-domain united link adaptation technique to optimize link availability and resource utilization.

A REVIEW OF THE EFFECTS OF LOW ELEVATION ANGLES ON THE PROPAGATION FOR SATELLITE COMMUNICATION LINK

The propagation phenomenon for satellite communication links is affected by the elevation angle of the satellite. Low elevation angles can cause signal attenuation due to increased atmospheric absorption, increased multipath fading, and rain attenuation. These effects can lead to decreased signal-to-noise ratio, reduced link availability, and degraded performance. This paper examines the effects of low elevation angle on the propagation phenomenon for satellite communication links. The paper begins by discussing the basics of satellite communication links, including the components of a link, the types of signals used, and the various propagation phenomena that can affect signal transmission. It then focuses on the effects of low elevation angle on signal propagation, including multipath fading, scintillation, and rain attenuation. The paper discusses how these effects can be mitigated through various techniques such as antenna design and signal processing. The results suggest that increasing the antenna gain and using higher frequency bands can help reduce the impact of low elevation angles on satellite communication links. Finally, it provides an overview of current research in this area and suggests potential future research directions.

The technology platform of the EIVE CubeSat mission for high throughput downlinks at W-band

This paper details the motivation and the status of a new satellite mission, which targets the in-orbit verification of a wide band satellite communication link, operating in the high millimeter-wave regime at 71–76GHz. Under ideal weather conditions, data rates over 15Gb/s in complex modulation formats are expected to be demonstrated in-orbit, while data rates over 6Gb/s are still expected under adverse atmospheric and weather conditions. The scientific payload, hosted by a 6U-CubeSat platform, comprises a high-performance W-band transmitter with GaN-based solid state power amplifiers, an InGaAs-based low-noise receiver and a modern FPGA-based digital processing unit, realizing arbitrary waveform generation functionality and 4k image/video storage. The ground terminal employs a highly directive Cassegrain antenna with coarse GNSS and fine multi-mode RF tracking and a low-noise receiver together with an integrated high-speed digital processing and storage unit.

Satellite Communication Effectiveness Evaluation Based on Distributed Multi-Node Receptions

Satellite-communication effectiveness evaluation is one of the key issues in the field of satellite communication links for satellite operation, maintenance, and emergency communication. However, conventional model-based calculation methods require accurate meteorological parameters, thus not applicable to practical engineering problems. In this paper, a hybrid method, combing direct calculation and equilibrium approximation, is proposed to evaluate the effectiveness of a satellite communication system, with distributed multi-node receiver stations on the earth. Especially, the proposed equilibrium approximation approach is resilient to meteorological factors. Field tests corroborate the feasibility of this new method for real-world problems.

Optimalisasi Saluran Komunikasi Berbasis Gelombang Mikro Sebagai Alternatif Sistem Pemantauan Curah Hujan

As a vast archipelagic country with diverse topographic conditions and has an annual average rainfall of more than 2000 mm, Indonesia is prone to hydrometeorological disasters. Based on Indonesia's disaster data, throughout 2021 there were 3,658 incidents of floods and landslides distributed throughout Indonesia. This makes real-time rainfall monitoring with high density indispensable. Indonesia currently has a rainfall monitoring system about 1000 automatic rain gauges, so an increase in the spatial resolution of network is necessary. The increasing density of monitoring equipment using rain gauges and weather radar poses the problem of high procurement and operational costs. Therefore, several alternative rainfall monitoring systems are needed. In this article, we review several studies that focus on the utilization of terrestrial and satellite communication link operating in high frequency bands as an alternative for measuring rainfall. Optimization of the satellite communication system network is more suitable than terrestrial networks to be applied in Indonesia with archipelagic areas because it has a large number of point distributions with wider coverage. The use of artificial intelligence with deep learning techniques such as one dimensional convolutional neural network (1D-CNN) is also very promising to estimate rainfall intensity because it has a high accuracy of 93%..

Machine Learning-Based Satellite Routing for SAGIN IoT Networks

Due to limited coverage, radio access provided by ground communication systems is not available everywhere on the Earth. It is necessary to develop a new three-dimensional network architecture in a bid to meet various connection requirements. Space–air–ground integrated networks (SAGINs) offer large coverage, but the communication quality of satellites is often compromised by weather conditions. To solve this problem, we propose an extended extreme learning machine (ELM) algorithm in this paper, which can predict the communication attenuation caused by rainy weather to satellite communication links, so as to avoid large path loss caused by bad weather conditions. Firstly, we use Internet of Things (IoT)-enabled sensors to collect weather-related data. Then, the system feeds the data to the extended ELM model to obtain a category prediction for blockage caused by weather. Finally, this information helps the selection of the data transmission link and thus improves the satellite routing performance.

Satellite to Ground Station, Attenuation Prediction for 2.4–72 GHz Using LTSM, an Artificial Recurrent Neural Network Technology

Satellite communication links suffer from arbitrary weather phenomena such as clouds, rain, snow, fog, and dust. Furthermore, when signals approach the ground station, they have to overcome buildings blocking the direct access to the ground station. This work proposes a model to predict the remaining signal strength for the next timeframe after deducting the attenuation and disruption impact caused during its propagation from the satellite to the ground station. The proposed model can be adjusted to comply with any geographic region and a broad spectrum of frequencies. We employ LTSM, an artificial recurrent neural network technology, providing a time-dependent prediction. We can instantly calibrate the satellite outgoing signal strength to overcome the predicted attenuation, resulting in satellite energy saving using this prediction.

Unseasonal super ionospheric plasma bubble and scintillations seeded by the 2022 Tonga Volcano Eruption related perturbations

The Hunga–Tonga volcano eruption at 04:14:45 UT on 15 January 2022 produced various waves propagating globally, disturbing the background atmosphere and ionosphere. Coinciding with the arrival of perturbation waves, several equatorial plasma bubbles (EPBs) were consecutively generated at post-sunset hours over the East/Southeast Asian region, with the largest extension to middle latitudes. These EPBs caused intenseL-band amplitude scintillations at middle-to-low latitudes, with signal fading depths up to ~16 dB. Considering the very rare occurrence of EPBs during this season in the East/Southeast Asian sector and the significantly modulated background ionosphere, we believe that the perturbation waves launched by the volcano eruption triggered the generation of the unseasonal super EPBs. The ionospheric perturbations linked with the 2022 Tonga volcano eruption propagated coincidently through the East/Southeast Asia longitude sector near sunset, modulated the equatorial F region bottomside plasma density, and acted as the seeding source for the generation of the unseasonal super bubbles. Our results implicate that volcano eruption could indirectly affect the satellite communication links in the region more than ten thousand kilometers away.

UltraViolet SANitizing System for Sterilization of Ambulances Fleets and for Real-Time Monitoring of Their Sterilization Level.

Background: The contamination of ambulances with pathogenic agents represents a potential threat for the public health, not only for common pathogens but also for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The aim of this project was to exploits the germicidal effect of the UVC radiation at 254 nm to sanitize the patient’s compartment of ambulances with an advanced UltraViolet SANitizing System (UV-SAN) and assess its relevance for avoiding the spread of COVID-19 and other drug resistant pathogens. Methods: The system is equipped with UVC lamps that are activated when the ambulance compartment is empty and sanitize the environment in less than 15 min. An Ozone sensor continuously monitors the gas concentration, ensuring it does not exceed threshold value harmful for patients and operators’ health. The system is relying on GNSS data and a satellite communication link, which allow to monitor and record traceability (when, where and what) of all the sanitation operations performed. This information is real-time monitored from a dedicated web-application. Results: UVC irradiation efficiently reduced SARS-CoV-2 virus titer (>99.99%), on inanimate surfaces such as plastic, stainless steel or rubber, with doses ranging from 5.5 to 24.8 mJ/cm2 and the UV-SAN system is effective against multi drug resistant (MDR) bacteria up to >99.99%, after 10 to 30 min of irradiation. Conclusions: UV-SAN can provide rapid, efficient and sustainable sanitization procedures of ambulances.

Geoclimatic characterization and latitudinal dependence of rain heights over Nigeria

Attenuation due to rain remains the most severe threat to terrestrial and satellite communication links in the tropics. Rain height is a precipitation parameter that plays important role in the determination of rain-induced attenuation. In this paper, a statistical study was carried out to establish the relationship between rain height and earth station latitude using rain heights derived from Zero Degree Isotherm Height (ZDIH) data retrieved from Global Precipitation Measurement (GPM). A strong positive correlation of 0.83 propelled the attempt to model equations for the estimation of rain height based on latitude. The research recommends a polynomial function of order 3 which has the best coefficient of determination (0.8). The annual mean values of rain heights were also computed and recommended for each of the four geo-climatic zones in Nigeria.

Real-Time Air-to-Ground Data Communication Technology of Aeroengine Health Management System with Adaptive Rate in the Whole Airspace

To overcome the problem of data transmission of the aeroengine health management system, a multilink communication system combining ultrahigh-frequency communication link, 4G cellular mobile communication link, and BeiDou satellite communication link was proposed. This system can realize the functions such as data receiving and sending, data encryption, and resuming transfer from the break point based on multiple links. When the flight altitude is not high, the communication distance is short, so the UHF digital transmission radio communication link is adopted, which is highly efficient and stable. When the communication distance is long, the 4G cellular mobile communication link can ensure both the communication distance and the communication rate. In the area where 4G signal cannot be covered in extreme terrain environment, BeiDou satellite communication link is used for data transmission. Besides, in order to ensure the communication rate of the link, a multilink adaptive switching technology was also developed. The test verified that the system can perform adaptive switching among multiple links, realize air-ground data communication in the whole airspace, and achieve a good communication rate, which has significative value of engineering application.