Satellite Communication Systems Research Articles

A Multi-Branch DQN-Based Transponder Resource Allocation Approach for Satellite Communications

In light of the increasing scarcity of frequency spectrum resources for satellite communication systems based on the transparent transponder, fast and efficient satellite resource allocation algorithms have become key to improving the overall resource occupancy. In this paper, we propose a reinforcement learning-based Multi-Branch Deep Q-Network (MBDQN), which introduces TL-Branch and RP-Branch to extract features of satellite resource pool state and task state simultaneously, and Value-Branch to calculate the action-value function. On the one hand, MBDQN improves the average resource occupancy performance (AOP) through the selection of multiple actions, including task selection and resource priority actions. On the other hand, the trained MBDQN is more suitable for online deployment and significantly reduces the runtime overhead due to the fact that MBDQN does not need iteration in the test phase. Experiments on both non-zero waste and zero waste datasets demonstrate that our proposed method achieves superior performance compared to the greedy or heuristic methods on the generated task datasets.

High-performance hard-input LDPC decoding on multi-core devices for optical space links

LDPC codes are a family of error-correcting codes that are present in most space communication standards. Thanks to their large processing power and their parallelization capabilities, prevailing multicore devices facilitate real-time implementations of digital communication systems, which were previously implemented into dedicated hardware devices. Previous works were done over the last decade on the implementation of Gbps decoders on programmable devices. However, these works focus on the soft input LDPC decoding algorithms. But, hard-input LDPC decoders are also required to design and prototype for instance next optical-based satellite communication systems. These systems should provide high throughput (≥10 Gbps) and low latency (≤1ms) internet links. In this article, the first software-based implementation of a hard-input multi-Gbps LDPC decoder is detailed. Thanks to different parallelization strategies and deeply optimized SIMD codes, throughput up to 7.5 Gbps is achieved when 10 Gallager-E iterations are executed onto an INTEL Xeon device making possible the design of software base station systems providing throughputs of tens of Gbps for optical system evaluation or base station design.

Minkowski–Sierpinski Fractal Structure-Inspired 2 × 2 Antenna Array for Use in Next-Generation Wireless Systems

In this paper, the design, simulation, fabrication, and characterization study of a low-cost and directional hybrid four-element (2 × 2 configuration) Minkowski–Sierpinski fractal antenna array (MSFAA) for the high-efficiency IEEE 802.11ax WLANs (Wi-Fi 6E) and the sub-6 GHz 5G wireless system is presented. Each element of the array is separated by 0.7 λ0. The complete four-element fractal antenna array system includes designing the single-element Minkowski–Sierpinski fractal antenna using two different substrates for performance comparison and an equal-split Wilkinson power divider (WPD) to achieve power division and to form a feed network. The single-element antenna, four-element fractal antenna array, and WPDs are fabricated using a flame-resistant (FR4) glass epoxy substrate with a dielectric constant (εr) of 4.3 and thickness (h) of 1.66 mm. For performance comparison, a high-end Rogers thermoset microwave material (TMM4) substrate is also used, having εr = 4.5 and h = 1.524mm, respectively. The designed four-element fractal antenna array operates at the dual-band frequencies of 4.17 and 5.97 GHz, respectively. The various performance parameters of the antenna array, such as return loss, bandwidth, gain, and 2D and 3D radiation patterns, are analyzed using CST Microwave Studio. The fabricated four-element antenna array provides the bandwidth and gain characteristic of 85 MHz/4.19 dB and 182 MHz/9.61 dB at 4.17 and 5.97 GHz frequency bands, respectively. The proposed antenna array design gives an improvement in the bandwidth, gain, and radiation pattern in the boresight at both frequencies. In the IEEE 802.11 ax WLANs (Wi-Fi 6E) deployments and the upcoming 5G wireless and satellite communication systems, it is critical to have directional antenna arrays to focus the radiated power in any specific direction. Therefore, it is believed that the proposed dual-band four-element fractal antenna array with directional radiation patterns can be an ideal candidate for the high-efficiency IEEE 802.11ax WLANs (Wi-Fi 6E) and the upcoming 5G wireless and satellite communication systems.

Analysis of the effectiveness of methods for ensuring the reliability of a communication satellite transponder

Objectives . Since the launch of satellite communication systems in practical use, approaches towards enhancing their operational quality and durability have been developing in the direction of increased reliability of airborne transponders. This is mainly achieved by increasing redundancy and using components with a lower failure rate. In this regard, the creation of new technologies and new materials is a particularly promising direction. However, since durability testing of complex systems can take several years, the problem of ensuring an effective combination of redundancy methods and elements having a reduced failure rate remains challenging. The purpose of the work is to analyze the effectiveness of methods for ensuring the reliability of a communication satellite transponder based on a proposed methodology for determining the durability index using a mathematical model of the probability of failure-free operation. Methods . In order to describe the complex structure of a satellite communication system transponder, a logical- probabilistic method is used, in which the dependence of the system reliability indicators on the reliability indicators of the transponder elements is formulated as a logical function of operability. Mathematical models of system reliability are created on this basis including for redundant systems. Graphs and analytical methods are used to compare different systems. Results . The influence of various methods for ensuring the redundancy of transponder devices and the use of more reliable components on the reliability and durability indicators is considered. A gamma-percentage resource-based technique for determining the durability indicator based on the constructed mathematical models of the probability of failure-free operation is presented along with a comparative analysis of measures to increase the gamma-percentage resource of the transponder. Conclusions . The presented method for determining the durability index using a mathematical model of the probability of no-failure operation can be used to determine the time interval within which redundancy increases the probability of no-failure operation as compared with a decrease in the failure rate of elements. On this basis, the most effective combination of redundancy methods and approaches for reducing the failure rate of elements can be identified.

Design of a Dual-Input Dual-Output Power Amplifier With Flexible Power Allocation

While dual-output power amplifiers (PAs) have shown great potential in the area of radar, satellite, and wireless communication systems, the flexibility of the power allocation in the dual-output PAs should be improved without sacrificing efficiency and circuit complexity. This letter presents a dual-input dual-output (DIDO) PA to enable flexible power allocation based on a simple circuit topology. It is demonstrated that not only power transfer from one output port to the other, but also flexible power allocation between two output ports can be obtained by the proposed DIDO PA. Meanwhile, optimal drain efficiency (DE) can be maintained when different power is delivered to the two output ports of the DIDO PA by controlling the input conditions. As a proof of concept, a DIDO PA operating at 2.4 GHz is fabricated and measured in this letter. The fabricated DIDO PA could deliver a total output power of more than 44 dBm and the total power can be allocated between two output ports. The maximum DE of the DIDO PA ranges from 71.8% to 75.6% over the 360° input phase difference.

Satellite and Terrestrial Network Convergence on the Way Toward 6G

Compared with traditional satellite communication systems, the recent advancement by 5G non-terrestrial network (NTN) technology offers a disruptive solution by enhancing mobile cellular technology to support satellite communications. It allows satellite operators to leverage the mobile cellular ecosystem and its economies of scale to penetrate satellite communications from a niche market to mainstream consumer market. On the other hand, it also facilitates the integration between the networks operated by terrestrial and satellite operators via the common radio/core network technology and architecture. With the key enabler by multi-mode devices, which could flexibly switch between terrestrial and satellite networks, NTN technology can turn terrestrial and satellite operators from competitors toward partners (e.g., complement service coverage, traffic roaming, and service platform). It is generally believed that satellite and terrestrial network convergence will be a mega trend from 5G toward 6G. The following sections will further investigate the potential use cases and advantages.

RF Fingerprinting Identification Based on Spiking Neural Network for LEO–MIMO Systems

Low earth orbit (LEO) satellites promise to be a source of innovation in wireless communication and their physical layer security deserves attention. However, many physical layer security techniques are hampered by excessive power consumption and high latency when used for LEO satellites. This letter proposes an energy-efficiency radio frequency fingerprinting identification (RFFI) method for LEO satellite communication systems based on spiking neural networks (SNN). In addition, we investigate a channel-independent RFF feature transformation and data augmentation to enhance system robustness. Numerical results show that our proposed model can yield identification accuracy up to 95.26% at a signal-to-noise ratio (SNR) of 25dB on orthogonal frequency division multiplexing (OFDM) signals, and reduces power consumption by 63.3% compared to existing models of comparable accuracy on FPGA.

The Impact of Job Insecurity on Intrinsic Motivation, Anxiety, Depression, and Job Performance of Information Technology Company Employees in Indonesia

This study aims to explore the influence job insecurity to intrinsic motivation, anxiety, and depression to job performance of information technology company employees at the operator level in Indonesia. Research conducted in 2022 is designed using the purposive sampling method involving 130 IT company employees in the satellite communication system operating sector in Greater Jakarta with a working period of more than 2 years. This quantitative research uses the Structural Equation Model (SEM) method and data were analyzed with Lisrel software. Some of the findings in this study show that intrinsic motivation positive effect on job performance, job insecurity no negative effect on intrinsic motivation and job performance. Vice versa, job insecurity has positive effect on anxiety and depression. Anxiety no negative effect on intrinsic motivation, however depression negative effect on intrinsic motivation. The managerial implications of this research are important for companies to do to suppress or reduce job insecurity what employees feel is that companies need to reduce uncertainty regarding SOPs and goals to be achieved, companies need to create a supportive work climate, focus on developing employee capabilities, and provide clarity regarding the rights employees will get for their duties in the company.

HERAS: A Modular Matlab Tool Using Physical Optics for the Analysis of Reflector Antennas.

HERAS is a tool developed in Matlab for the analysis of reflector antennas using physical optics (PO) theory. Its graphical user interface (GUI) and source code are freely available for educational and research purposes. It has the necessity of being a flexible tool to provide adaptability to system engineering requirements and can also be of interest to antenna engineers working on the design of reflector antennas. Due to the increasing demand of broadband services, satellite communications systems are becoming highly complex in order to meet connectivity requirements. To fully exploit the benefits of these systems, multidimensional optimisations are crucial, which call for an efficient estimation of the coverage characteristics. Reflector-based solutions are one of the preferred architectures for very high-throughput satellite (VHTS) systems. A detailed description of HERAS is presented in this paper which has been validated with available commercial software packages. In addition, some examples are described in which the tool has been used for the efficient estimation of VHTS systems performance.

Analysis of Vsat Gyro performance based on the power level of the antenna receiver on the Pelni ship

The satellite communication system that is used for ship communication in Indonesian waters is expected to transmit real time data at any time under any conditions. However, currently, the Vsat Gyrsoscope antenna that is installed on the Pelni ship still uses the Ku band frequency. This frequency band is very susceptible to rain attenuation. Vsat Gyro will automatically search for satellites that cover it. Only when it is raining and the ship is moving towards the port, is there a decrease in the receiving power level. SNR and power and C/N will drop. Therefore, it is necessary to do an analysis to overcome this problem so that it is not disconnected during the transmission. This study conducted an analytical study to validate the analytical predictions of phasing the vsat power signal level on the pelni ship to maintain communication during sea operations, which are included in TKT 3 (three). The tools used in the measurement are vsat modem, PRTG application, laptop, RJ 45 cable, and Spectrum Analyzer. By optimizing the calculation of the margin link budget, the calculation of Qos and the parameters vsat Eb/No, C/N and SNR when adjusted to the operating conditions of the ship with high rain intensity so that communication can continue to run even when the worst conditions can be maintained properly.Â

Highly compact UWB-BPF with a wide notch-band using a rectangular ring structure and two Y-shaped open stub resonators

A miniaturized ultra-wideband bandpass filter (UWB-BPF) with a high rejection notched band is proposed in this article. It is composed of a rectangular ring with two grounded vias, a microstrip line with two open radial stubs, a pair of interdigital feedlines with two lumped capacitors and two open-loaded Y-shaped stub resonators (YSSR), as well as a defected ground structure (DGS). This filter was simulated and fabricated by using a practical printed circuit board (PCB) process with the substrate of FR4. The measurement results agree well with the simulation data. The measured 3-dB passbands cover 2.73–4.36 and 6.82–11.78 GHz, the in-band insertion loss is less than 1.13 dB except at the edges of the bands, and the return loss is better than 10 dB. It is found that the filter’s lower and upper transmission zeros occur at 0.8 and 13.95 GHz with the magnitudes of −87.2 and −45.6 dB, respectively. This makes the filter exhibit high selectivity with the steep skirt characteristics. It is also worth noting that the proposed filter possesses a wide 10-dB notch band ranging from 4.87 to 6.93 GHz with the highest rejection of 46.3 dB at 5.9 GHz. This feature can effectively and simultaneously inhibit the unwanted signals coming from the C-band 5G mobile communication, 5-GHz WiFi, WLAN, and 6-GHz satellite systems. Furthermore, the presented filter is highly compact with the dimensions of 13.2 mm × 11.8 mm and has a very wide upper stopband spanning from 13.4 to 28 GHz with rejection of 20 dB or higher.

Onboard Processing in Satellite Communications Using AI Accelerators

Satellite communication (SatCom) systems operations centers currently require high human intervention, which leads to increased operational expenditure (OPEX) and implicit latency in human action that causes degradation in the quality of service (QoS). Consequently, new SatCom systems leverage artificial intelligence and machine learning (AI/ML) to provide higher levels of autonomy and control. Onboard processing for advanced AI/ML algorithms, especially deep learning algorithms, requires an improvement of several magnitudes in computing power compared to what is available with legacy, radiation-tolerant, space-grade processors in space vehicles today. The next generation of onboard AI/ML space processors will likely include a diverse landscape of heterogeneous systems. This manuscript identifies the key requirements for onboard AI/ML processing, defines a reference architecture, evaluates different use case scenarios, and assesses the hardware landscape for current and next-generation space AI processors.

Applications and prospects of artificial intelligence in covert satellite communication: a review

Satellite communication has the characteristics of wide coverage and large communication capacity, and is not easily affected by land disasters. It is quite suitable as a supplement to terrestrial communication networks and has been widely used in education, navigation, emergency relief, military, etc. However, due to the openness of the channel of satellite communication systems, satellite communication signals are easily eavesdropped on by eavesdroppers. This greatly threatens the privacy and security of countries and individuals. Covert satellite communication can effectively improve the covertness of satellite communication systems and greatly reduce the probability of detection by eavesdroppers. So, it has attracted more and more attention. In addition, with the development of artificial intelligence (AI), AI has been applied in many technics of covert satellite communication, which has achieved higher reliability and stronger concealment in covert satellite communication systems. The research status of key technics in covert satellite communication is discussed in this study, and the applications of AI in covert satellite communication are shown. Finally, future research directions of covert satellite communication are looked forward to. In the future, covert satellite communication technology will be an indispensable part of satellite communication systems.

Ultra-High Capacity Optical Satellite Communication System Using PDM-256-QAM and Optical Angular Momentum Beams.

Twisted light beams such as optical angular momentum (OAM) with numerous possible orthogonal states have drawn the prodigious contemplation of researchers. OAM multiplexing is a futuristic multi-access technique that has not been scrutinized for optical satellite communication (OSC) systems thus far, and it opens up a new window for ultra-high-capacity systems. This paper presents the 4.8 Tbps (5 wavelengths × 3 OAM beams × 320 Gbps) ultra-high capacity OSC system by incorporating polarization division multiplexed (PDM) 256-Quadrature amplitude modulation (256-QAM) and OAM beams. To realize OAM multiplexing, Laguerre Gaussian (LG) transverse mode profiles such as LG00, LG140, and LG400 were used in the proposed study. The effects of the receiver's digital signal processing (DSP) module were also investigated, and performance improvement was observed using DSP for its potential to compensate for the effects of dispersion, phase errors, and nonlinear effects using the blind phase search (BPS), Viterbi phase estimation (VPE), and the constant modulus algorithm (CMA). The results revealed that the proposed OAM-OSC system successfully covered the 22,000 km OSC link distance and, out of three OAM beams, fundamental mode LG00 offered excellent performance. Further, a detailed comparison of the proposed system and reported state-of-the-art schemes was performed.

Very Compact Waveguide Orthomode Transducer in the K-Band for Broadband Communication Satellite Array Antennas

A very compact waveguide orthomode transducer (OMT) is described in this paper. The design is characterized with a twofold rotationally symmetric cross-section in the probing area, adapted from a side-coupling OMT design, simultaneously enabling low port-to-port coupling and high cross-polarization discrimination (XPD) over a fractional bandwidth of about 15-20%. Compared to previously reported compact waveguide OMTs, the proposed design is simpler, thus facilitating its manufacture at millimeter-wave frequencies. The concept is demonstrated with a design in the K-band for a broadband communication satellite downlink over the frequency band of 17.3-20.2 GHz. For test purposes, transitions to standard waveguide WR42 are included, and the OMT is assembled with a conical horn antenna. The measured reflection and coupling coefficients are below -19.5 dB and -22.9 dB, respectively, over the nominal bandwidth, and they are in good agreement with the simulation's results. The on-axis XPD, measured in an anechoic chamber, is better than 30 dB over the nominal bandwidth, which is also in line with simulations. The proposed waveguide OMT may be designed to fit in a lattice below one wavelength at the highest operating frequency, which is desirable for dual-polarized closely spaced array antennas in low and medium Earth orbit communication satellite systems. The simple mechanical design of the proposed OMT makes it particularly appealing for additive manufacturing techniques, as demonstrated with a variant of the design having folded single-mode waveguides, which preserves the RF properties of the original design.

Ku-band analog photonic down-conversion link with coherent I/Q image rejection and digital linearization.

Analog photonic down-conversion links have been widely used in radar, electronic warfare, and satellite communication systems. Aiming at the optimization demands of the link performance, we demonstrate and experimentally verify a Ku-band photonic down-conversion link based on coherent in-phase/quadrature (I/Q) image rejection and digital nonlinear compensation. The image-rejection ratio at 17.5 GHz is measured to be 47 dB. After digital processing, the image intermodulation distortions (MMD) and the intermodulation distortions (IMD3) are suppressed by 18.1 dB and 10.9 dB, respectively. The corresponding spurious-free dynamic range (SFDR) reaches 108.83 dB·Hz2/3.

An Adaptive Routing Algorithm for Inter-Satellite Networks Based on the Combination of Multipath Transmission and Q-Learning

In a satellite network, the inter-satellite link can facilitate the information transmission and exchange between satellites, and the packet routing of the inter-satellite link is the key development direction of satellite communication systems. Aiming at the complex topology and dynamic change in LEO satellite networks, the traditional single shortest path algorithm can no longer meet the optimal path requirement. Therefore, this paper proposes a multi-path routing algorithm based on an improved breadth-first search. First, according to the inter-satellite network topology information, the improved breadth-first search algorithm is used to obtain all the front hop node information of the destination node. Second, all the shortest paths are obtained by backtracking the path through the front hop node. Finally, according to the inter-satellite network, the bandwidth capacity of the traffic and nodes determines the optimal path from multiple shortest paths. However, due to the high dynamics of low-orbit satellite networks, the topology changes rapidly, and the global topology of the network is often not available. At this time, in order to enhance the adaptability of the algorithm, this paper proposes an inter-satellite network dynamic routing algorithm based on reinforcement learning. Verified by simulation experiments, the proposed algorithm can improve the throughput of the inter-satellite network, reduce the time delay, and the packet loss rate.

Performance Evaluation of SSK Modulation Over Shadowed-Rician Land Mobile Satellite Links

We investigate the performance of satellite communication systems acquiring the space shift keying (SSK) modulation technique over shadowed-rician (SR) land mobile satellite (LMS) link. Specifically, we discuss the analytical performance of the considered system over independent and identically distributed SR fading channels in terms of symbol error rate (SER), diversity order, and average capacity. The SER of the considered set-up is derived by utilizing moment generating function (MGF) expression over the SR fading LMS communication links. The analytical diversity order of the scheme is derived by using SER expression. We consider the effect of elevation angles on the SER performance, diversity order, and channel capacity of the considered SSK-assisted satellite communication system. As observed from simulation and analytical results, the performance of the considered set-up can be raised by improving elevation angles. Further, a closed-form expression of the average capacity of the SSK assisted satellite communication system is also derived. It is shown through simulation and analysis that the fading conditions and elevation angle does not affect the diversity order of the system, but it adversely acts on the SER performance and average capacity of the system.

АНАЛИТИЧЕСКОЕ ИССЛЕДОВАНИЕ ВЛИЯНИЯ ИОНОСФЕРЫ НА ЭНЕРГЕТИЧЕСКИЕ СООТНОШЕНИЯ В СПУТНИКОВЫХ СИСТЕМАХ СВЯЗИ МЕТОДАМИ ФИЗИЧЕСКОЙ КИНЕТИКИ ПЛАЗМЫ

In civil aviation, an urgent and important task is to provide air traffic participants with uninterrupted radio communication. Satellite communication is a global mobile network covering the entire surface of the Earth, including polar regions, which provides a two-way data and voice communication exchange. An analysis of the principles of functioning of satellite communication systems (SCS) showed that the determination of energy characteristics is of great importance. Energy characteristics in satellite communication channels and the level of interference determine SCS operational capabilities and quality indicators. One of the critical factors that determine the effectiveness of the SCS functioning is the conditions for the propagation and absorption of radio waves, including ionospheric phenomena, which are not yet fully understood, and this determines the research relevance. This article is devoted to theoretical studies of the ionospheric plasma by the methods of physical kinetics to increase the energy potential of the radio links of a satellite communication system.

Physical Layer Security in Interference Limited Land Mobile Satellite Communication Systems: Safeguarding Data Transmission

This paper focuses on evaluating the secrecy performance of a downlink land mobile satellite (LMS) system. The system faces the challenge of providing secure communication between a satellite and a legitimate user while an eavesdropper is present on the ground. Additionally, co-channel interference signals at the user's destination are considered. To address these issues, the study proposes a novel approach that utilizes Shadowed-Rician fading channels for satellite links and Nakagami-m fading for interfering terrestrial links. The main objective is to enhance the physical layer security of Interference-Limited Land Mobile Satellite Communication Systems. The approach incorporates advanced signal processing, beamforming, and artificial noise techniques to effectively manage interference. Encryption, authentication mechanisms, and intelligent power control strategies are implemented to protect transmitted data and optimize signal strength while reducing the risk of interception by potential eavesdroppers. Through comprehensive simulations, the proposed approach is thoroughly evaluated, demonstrating its effectiveness in achieving improved secrecy performance and increased resilience against security threats. The findings highlight the potential for its application in secure satellite communication systems operating in interference-constrained environments.