Earth Station Research Articles

Methodology for estimating reception efficiency of mutually correlated or in- phase signals at diversity transmission

The article describes and theoretically substantiates the potential technical capabilities of spatially separated earth stations (ES). When several ESs emit in-phase or mutually pairwise correlated signals in the direction of one received antenna of the object, the total level of the sum of emissions at its output (at the input of the receiving path) may be several times higher than the sum of the powers of these signals. In this regard, the article investigates the influence of the phase difference of the transmitted signals on the value of their total average power at the input of the receiving path. In the case of addition of common-mode signals, a formula is used to calculate in which the power of harmonic radiation is proportional to the square of the sum of the amplitude of the common-mode signals. This paradox is also valid for pairwise cross-correlated signals. The presented technique for evaluatingтthe effectivenessтallows one to establish not only the dependence of the energy ratios on the nonтenergy parameter, but also to determine the number of low-power ESs required to ensureтthe required signal level at the input of the receiving device. The use of the presented technique makes it possible to evaluate the efficiency of receiving a combined high-power signal for a differentтnumber of emitters that form in-phase or pairwise mutual correlation of signals at the receiving point.

Performance Analysis of Inter-satellite Optical Wireless Communication (IsOWC) System with Multiple Transmitters/Receivers

The satellite communications networks have certainly been innovated recently by Inter-satellite optical wireless communication (IsOWC) networks. The prerequisite for next generation mobile satellite communication is superior multimedia facility for consumers at anytime and anywhere. The proposed optical communication system is designed and analysed to improve data transmission quality over the distance between two geostationary (GEO) satellites greater than 36000 km. This trend is to achieve high speed transmission with minimizing the presence possibility of free space loss in transmission that can occur in satellite communication via the longest range. Numerous transceivers IsOWC is a hopeful way to deal with be utilized related to different earth stations as a system utilized between the geosynchronous satellites. The wireless transmission creates the opportunity at high optical power without free space loss. The results of the simulated system showed that with 32 transmitters/receivers IsOWC, the Q-factor values of 36.526, 12.176 and 4.015 are obtained at 38000 km range at laser power of (19, 14 and 9) dBm, respectively. The proposed system is operated at 19 dBm optical power and different values of aperture size and the best values of Q-factor and BER are 41 and 10−250, respectively, for highest diameter value of 20 cm. The operation of the system with various values of bit rate is verified as well. It is seen that the best system performance is at 0.032 Gb/s bit rate and will be of lower as the bit rate increases until it roughly fixes at 32 Gb/s. This research offers the treatment for the transmission problem for ultra-speed application in mobile satellite systems.

The novel design concept for the tensioning system of an inflatable planar membrane reflector

The membrane structures are the potential solution for near term spacecraft systems due to its significant advantages such as lightweight, higher folding and packaging efficiency, ease of deployment, and low on-board volume requirement. For the membrane structures, maintaining the uniform state of stress conditions with a minimum mass penalty of a tensioning system is the most challenging task for space industries. The inflatable planar membrane reflector is attached to the satellite body, used for bidirectional communication between the satellite and earth stations. The aim of the study is to develop the methodology for designing the tensioning system for a planar membrane reflector antenna. The work presents a novel average diagonal stress distribution relation for rectangular membrane reflector. The loading analysis of membrane reflector and tensioning chord is carried out numerically and experimentally to achieve the design goals of the antenna structure. The outcome of the loading analysis is compared and found to be consistent with the method available in the literature. The inflatable torus diameter is calculated based on the tensioning force required at anchor points.

Low-Complexity Algorithm for Radio Astronomy Observation Data Transport in an Integrated NGSO Satellite Communication and Radio Astronomy System

An integrated non-geostationary orbit (NGSO) satellite communication and radio astronomy system (SCRAS), was recently proposed in [1] as a new coexistence paradigm. In SCRAS, the transportation of the radio astronomical observation (RAO) data from the space to the ground stations is an important problem, for which [1] proposed a linear programming optimization based algorithm. However, the computational complexity of this algorithm is quite high which is exacerbated by the need to re-compute the algorithm frequently due to the time-varying characteristics of the observing satellites, the Earth stations, and the RAO region. In this paper, to address this high complexity issue, we develop a low-complexity RAO data transport algorithm. In addition to the static resource constraint scenario considered in the existing work, we introduce a dynamic resource constraint scenario to exploit the knowledge of the satellite communication system (SCS) traffic statistics. We also present a modified version of the algorithm in [1] for the dynamic resource constraint scenario. In addition to the number of inter-satellite link (ISL) hops as the RAO data transport cost metric, we also evaluate the metric of the sum of the squared ISL hop distances which reflects the transmission energy cost. Furthermore, computational complexity analysis and data transport costs of the algorithms are presented. Our results show that the proposed algorithm yields several orders of computational complexity saving over the existing method while incurring a modest increase in the data transport cost. Our proposed dynamic resource constraint scenario provides plausible reduction of the RAO data transport cost.

Max Completion Time Optimization for Internet of Things in LEO Satellite-Terrestrial Integrated Networks

In this article, we investigate max completion time optimization for Internet of Things (IoT) in LEO satellite-terrestrial integrated networks (STINs), in which IoT devices use non-orthogonal multiple access (NOMA) scheme to transmit data to central earth stations (CESs), and orthogonal multiple access (OMA) scheme is used for data transmission from CESs to LEO satellite. We decouple this problem into two subproblems: 1) max completion time optimization in terrestrial networks and 2) max completion time optimization among satellite beams. Different from the existing works about NOMA data transmission in terrestrial networks, we propose a cooperative NOMA scheme, and derive the closed expressions of the optimal cooperative data and the optimal transmit power of IoT devices. Based on the closed-form expressions, a joint subcarrier assignment and cooperative NOMA pairing (JSACNP) approach is proposed to minimize the max completion time in terrestrial networks by utilizing matching theory. Then, to minimize the max completion time among satellite beams, the optimal linear receiver expression is derived with fixed transmit power. Convex optimization is utilized to solve transmit power optimization, we propose an algorithm to solve it by CVX tool. An iterative algorithm is proposed for improved performance. Finally, numerical results are provided to evaluate our proposed algorithms, compared with some other proposed approaches or algorithms.

Estimating the noise immunity of spacecraft on-board repeaters and satellite earth stations under the influence of intentional interference

Civil, special and dual-use satellite communication systems are used everywhere in space, land, aviation and maritime means of transmitting information to remote subscribers. At the same time, during operation of these systems, one of the main issues is ensuring the required level of noise immunity of communication channels when operating in a complex electromagnetic environment, in conditions of both unintentional and intentional interference. This article proposes a technique for estimating the noise immunity of spacecraft on-board repeaters and satellite earth stations under the influence of intentional interference based on the application of the suppression coordinate law, which takes into account the probabilities of suppressing a useful communication signal depending on the coordinates of interference points by frequency, time, radiation power. The results of calculations and graphical dependencies based on results of mathematical simulation of impact efficiency on onboard repeaters of spacecraft and terrestrial stations of satellite communication of noise barrier by frequency of interference in modes of repeater functioning both with direct transfer of signal spectrum by frequency and with its processing on board are presented. At any stage of design of communication systems in the composition of various complexes of aviation, sea, land, space bases, it is possible to obtain estimates of their noise immunity, or vice versa, when designing electronic warfare, to obtain estimates of suppression of satellite communication systems according to the probability criterion.

A simulation experiment on the GM estimation for Comet 133P/Elst-Pizarro

In China’s asteroid mission to be launched around 2025, (7968) 133P/Elst-Pizarro (hereafter 133P) will be the second target, after a visit to asteroid (469219) Kamo’oalewa. This paper describes a simulation of precise orbit determination for the spacecraft around comet 133P, as well as estimation of its gravitational parameter (GM) value and the solar radiation pressure coefficient Cr for the spacecraft. Different cometocentric distances of 200, 150 and 100 km orbits are considered, as well as two tracking modes: exclusive two-way range-rate mode (Earth station to spacecraft) and combinations of two-way range-rate and local spacecraft onboard ranging to the comet. Compared to exclusive two-way range-rate, the introduction of local ranging observables improves the final GM uncertainties by up to one order of magnitude. An ephemeris error in the orbit of 133P is also considered, and we show that, to obtain a reliable estimate of the GM for 133P, this error cannot exceed a one km range.

A Novel Approach for Pivot-based Sensor Fusion of Small Satellites

Precise and agile pointing performance based on the fusion or combination of its on-board sensor inputs such as gyroscope and star-tracker are critical in spacecraft platform. This is very critical in keeping the accuracy of the satellite platform orientation when performing task requests from the earth control station. However, the processing speed greatly depends on the satellite attitude. Attitude representation by Pivot parameters (or Pivot vectors) has been used in applications dealing with flying objects. We are going to extend these methods to small satellites. This paper proposes a method of Pivot-based attitude sensor modeling and filtering for small satellites. We will adopt an Extended Kalman Filter (EKF) and fuzzy-tuning EKF for attitude estimation. Both quaternion and Pivot-based simulation are performed based on an operating satellite and the results are compared in terms of their geometrical interpretation and performance. The satellite model that we used was derived from VNREDSat-1 (the 1st Vietnam Natural Resources, Environment and Disaster-monitoring small satellite). Our results indicate that Pivot vectors demonstrate to be an appropriate model for satellite attitude representation and computation.

Stand for measuring the directional characteristics of antennas of satellite communication systems

The development of network based on satellite communication systems is a promising solution for providing telecommunications services in the Arctic. Therefore, the task of developing and creating earth stations for advanced satellite communication systems that have characteristics significantly higher than their world counterparts is actual. Characteristics of such stations depend on antenna’s systems characteristics that determine the energy characteristics of the communication channel. The aim of this work is a stand developing for measuring directional characteristics of antennas of satellite communication systems based on the spherical scanner (TS8991). Spiral scanning is an alternative measurement method aimed at reducing measurement time with saving necessary accuracy. As a result of this work, the spiral scanning algorithm based on the near-field scanner Rohde & Schwarz TS8991 was implemented. Moreover, the stand for monitoring and configuring the parameters of satellite earth station antennas was built. Block diagram of this stand is presented in article. An antenna with 1,2 m diameter of reflector was tested on the developed stand. The measurement results showed deviations of the measured values from the calculated values, which related by design disadvantages of the antenna. The stand using time was 35 minutes for measurements and conversions to the far field, for an antenna with 1,2 m diameter of reflector.

Space Diversity Mitigation Effects on Ionospheric Amplitude Scintillation With Basis on the Analysis of C/NOFS Planar Langmuir Probe Data

AbstractThe present contribution applies a modified version of a well‐known weak‐scatter scintillation model to the propagation paths between an Earth station and two geostationary satellites, as they are affected by drifting ionospheric irregularities detected by the planar Langmuir probe onboard the Communications/Navigation Outage Forecasting System (C/NOFS) satellite. This study considers one year of data from a limited altitude range, two longitude sectors and frequencies to analyze the mitigation effects from the angular distance between the geostationary satellites on the space diversity gain, considering the statistical distributions of the amplitude scintillation index S4. The results indicate that the space diversity gain increases with the angular distance between geostationary satellites. However, once the angular distance between the geostationary satellites reaches a certain limit (approximately 20°), the space diversity gain no longer increases. Additionally, these gains are high at the L1 frequency and less impressive at an Ultra High Frequency (UHF). It is shown that these observations are consistent with the South American and Indian‐Asian equatorial and low‐latitude ionospheric environments, also characterized through the same data and the scintillation formulation.

Adjacent channel compatibility between IMT and ubiquitous FSS Earth Stations in the 3.4–3.8 GHz frequency band

This study has investigated the mitigations necessary for successful compatibility between International Mobile Telecommunications (IMT) services and Fixed Satellite Service (FSS) Earth Stations operating in adjacent frequency bands. We consider a problem where IMT services operate in the 3.4–3.6 GHz frequency band and FSS Earth Stations operate in the adjacent 3.6–3.8 GHz band (both bands are within the frequency range designated C-band). The results presented in this paper are applicable to other boundaries between IMT and FSS operating in C-band. This is an adjacent band compatibility problem, hence the mitigation considered is based on frequency separation. We firstly perform a co-frequency interference analysis and then determine the Net Filter Discrimination available for a range of possible frequency separations including Guard Bands. These calculations rest on some assumptions regarding the IMT transmitter and FSS receiver spectrum masks. We present some results which show that an 18 MHz Guard Band is sufficient to mitigate interference. This analysis is based on the median aggregate interference-to-noise ratio $$\Sigma I/N$$ delivered by our co-frequency analysis, using a − 10 dB threshold and covering all of the spectrum mask combinations considered in the study.

Optimasi Waktu Akuisisi Data Satelit Noaa18 Menggunakan Jaringan Syaraf Tiruan Backpropagation

Earth stations are built to monitor the presence of satellites starting from satellite data, monitoring satellites, and carry out orders and corrections if needed. On the earth station there is a satellite data receiving antenna, the more elevation angle of the current satellite data receiver antenna can affect the time duration of the satellite data. The purpose of this research is to apply the Artificial Neural Network (ANN) method to design a time optimization system for satellite data at the LAPAN Pekayon earth station, East Jakarta. The data used as input is the elevation angle. The benefit of this research is expected to make it easier for operators and technicians to measure the time optimization of satellite data at earth stations. The best training results with learning rate = 0.2, error = 0.0001, max. epoch = 100000, neuron hidden layer = 15. The MSE value obtained is 0.0001 reaching the goal at epoch 68810. Regret the training / training reverse sequence reaches 0.99878. The best test result is to use learning speed 0.2 hidden layer neurons 15 comparison of training data = 54 and test data = 18. The accurate result is exactly the same as the specified error, namely 0.0001. The difference in the average target duration is 3 seconds compared to the ANN target. Artificial Neural Network (ANN) with the back propagation method of training function gradient descent (traingd), was successfully used to an optimization system for satellite data acquisition time at earth stations.

Impact of 5G New Radio Downlink Signal on Fixed-Satellite Service Earth Station

Impact of 5G New Radio Downlink Signal on Fixed-Satellite Service Earth Station

Development of a device for monitoring and tuning radio-technical parameters of a satellite communications Earth station

The article describes the existing methods for studying the characteristics of the antennas that are used in satellite earth stations. A variant of the device based on a spherical scanner is proposed. The spherical scanner uses the method of measuring the field in the near field. It has been established that for high efficiency and reduction of measurement time, it is necessary to use the spiral scanning method. The composition and block diagram of the device is presented. Recommendations on the use of software for processing measurement results are given.

Анализ способов наведения антенн земных станций спутниковой связи

The antenna guidance of earth stations of satellite communication consists in such its spatial orientation in azimuth and angle of location, at which the antenna›s directional pattern would coincide with the direction to the repeater located on an artificial satellite of the Earth. The article analyzes the methods, as well as their features, of pointing the antennas of terrestrial satellite communication stations. Suggestions are made for future experimental studies.

Оценка методов перераспределения радиоресурса ретранслятора в системах спутниковой связи

For allocating the radio resource of the repeater earth stations are different multiple access techniques (MDVR, MDCR, MDCR). The article presents a theoretical assessment of methods for redistributing the radio resource of a repeater in satellite communication systems. The performed analysis makes it possible to organize and conduct an empirical or mathematical experiment at a qualitative level to identify certain patterns.

Теоретический анализ возникновения помех в системах спутниковой связи при использовании многостанционного доступа с кодовым разделением каналов

Abstract. To ensure the most effective use of the limited radio resource of the repeater, various methods of multistation access of earth stations to the repeater are developed and applied, based on one or another method of channel separation. The article presents a theoretical analysis of the occurrence of mutual and combination interference in satellite communication systems when using multi -station access with code separation of channels. Recommendations for further experimental studies are proposed.

Design and analysis of angular stable antipodal F‐type frequency selective surface with multi‐band characteristics

This article presents frequency selective surface (FSS) with multi-band characteristics that features tri band band-stop and dual-band passband filter. The proposed FSS unit cell comprises the F-type resonance elements disposed of antipodal (diametrically opposed to) one to another on both layer and a square loop surrounding all resonators on the top layer of the dielectric substrate. The structure is specifically designed to filter out some extensively used broadband communication signals, such as, WiMAX and WLAN while enabling C-band satellite communication in the earth station and provides three stopbands operating at 2.4, 5.2, and 5.9 GHz besides two passbands of 4.1 and 5.5 GHz. Although this structure has a multi-band structure, it exhibits high stable performance for oblique incidence ranging from 0° to 60° for both transverse electric (TE) and transverse magnetic (TM) polarizations. Considering the resonant frequency deviation (RFD) at the incidence waves with different angles of arrivals, it was found that RFD at 60° is less than 0.6% on average and very low when compared with existing studies about multi-band FSS. The detailed equivalent-circuit model (ECM) is employed to predict and analyze the transmission characteristic of the proposed structure, and a good agreement between the simulated and measured transmission coefficients is obtained.

Enhancing Satellite Clock Bias Prediction Accuracy in the Case of Jumps with an Improved Grey Model

High accuracy and reliable predictions of the bias of in-orbit atomic clocks are crucial to the application of satellites, while their clocks cannot transfer time information with the earth stations. It brings forward a new short-term, mid-long-term, and long-term prediction approach with the grey predicting model (GM(1, 1)) improved by the least absolute deviations (GM(1, 1)-LAD) when there are abnormal cases (larger fluctuations, jumps, and/or singular points) in SCBs. Firstly, it introduces the basic GM(1, 1) models. As the parameters of the conventional GM(1, 1) model determined by the least squares method (LSM) is not the best in these cases, leading to magnify the fitting errors at the abnormal points, the least absolute deviations (LAD) is used to optimize the conventional GM(1, 1) model. Since the objective function is a nondifferentiable characteristic, some function transformation is inducted. Then, the linear programming and the simplex method are used to solve it. Moreover, to validate the prediction performances of the improved model, six prediction experiments are performed. Compared with those of the conventional GM(1, 1) model and autoregressive moving average (ARMA) model, results indicate that (1) the improved model is more adaptable to SCBs predictions of the abnormal cases; (2) the root mean square (RMS) improvement for the improved model are 5.7%∼81.7% and 6.6%∼88.3%, respectively; (3) the maximum improvement of the pseudorange errors (PE) and mean absolute errors (MAE) for the improved model could reach up to 88.30%, 89.70%, and 87.20%, 85.30%, respectively. These results suggest that our improved method can enhance the prediction accuracy and PE for these abnormal cases in SCBs significantly and effectively and deliver a valuable insight for satellite navigation.

Electromagnetic Radiation Safety: Russian National and International Regulatory Frameworks for Radiofrequency Electromagnetic Fields

Summary. Introduction: Today, the growing human exposure to radiofrequency electromagnetic fields is of serious concern to the population and the international scientific community. Sources of radiofrequency electromagnetic fields in residential areas include mobile radio base stations, signal repeaters, wireless broadband access points, TV and radio transmitters, satellite earth stations, radar and radio relay stations. Launching of 5G mobile networks will further complicate the electromagnetic situation in inhabited areas, especially in megacities where the size of exposed population is the largest. In the system of measures contributing to protection of the population from adverse health effects of electromagnetic fields, standards (regulations and other documents establishing electromagnetic fields permissible levels) play a significant role and lay the foundation for organizational and technical measures of protection. High importance of standards in ensuring electromagnetic safety served as the basis for our study. The objective of the study was to perform a comparative analysis of radiofrequency electromagnetic fields standards for inhabited areas and approaches to setting electromagnetic fields exposure levels adopted by different countries and international organizations. Methods: We reviewed of some aspects of biological effects of radiofrequency electromagnetic fields, regulations setting electromagnetic fields exposure limits in different countries and recommended by ICNIRP, and approaches to establishing those limits. Conclusions: We found a significant discrepancy in radiofrequency electromagnetic fields limits adopted in different countries, the legal status and scope of regulatory documents. Differences in the methodology for the development, adoption and approval of electromagnetic fields standard accompanied by differences in their legal status prevent uniform EMF standard setting.