Satellite Communication Systems Research Articles

Computer model of the transponder for the analysis of phase distortions of the signal

The article discusses issues related to the development of a computer model of an on-board relay complex with linear signal retransmission for the analysis of phase distortion of the signal. It is very important to know the phase distortion (foray) when determining the coordinates of the radio source by the phase method using a virtual antenna array in satellite communication systems. The literature review given in the article showed that it was not possible to conduct these studies on existing computer models. Based on the classical version of the block diagram of the on-board relay complex, a computer model was developed in the MATLAB R 2016b (Simulink) environment. The model includes a receiving device, an input and output multiplexer and power amplifiers. Mathematical models of Saleh and Gorbanni amplifiers implemented on traveling wave lamps and solid-state amplifiers, respectively, were taken as nonlinear amplifiers. Multiplexers are implemented in the form of bandpass filters connected in parallel. The hybrid divider and ferrite circulators were not included in the model. In the model, it is possible to investigate the dependence of the phase distortion of the signal on the characteristics of the structural blocks of the on-board relay complex. The computer model also provides for the possibility of studying the effect of noise on phase distortion.

Design of satellite mobile synchronization system based on OFDM code

In the 5G era, satellite communication has been widely applied in more scenarios. Orthogonal Frequency Division Multiplexing (OFDM) has been adopted to the 3GPP standard and is the primary sync encoding method for satellite communication. However, the OFDM-based system is extremely susceptible to carrier frequency offset (CFO), and Doppler shift make a major impact on the CFO. Therefore, the traditional methods of synchronization based on OFDM cannot meet the requirement of satellite communication with large frequency offset and delay. There are many studies focus on improving the methods of CFO estimation and compensation to adapt the technologies of synchronization based on OFDM to the satellite communication system. In this paper, ZC based and matrix-vector multiplication method, multi-symbol merging method and preamble and PSS symbols based and filter frequency locked loop-based method of synchronization of OFDM-based satellite communication will be introduced. The accuracy and complexity of these methods both meet the requirement of 5G satellite communication system. Future researchers may focus on reducing complexity and expanding application scenarios.

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.

Base station location generation algorithm for satellite‐terrestrial co‐existence studies

SummaryThe enormous growth of mobile broadband traffic is a catalyst for expanding terrestrial communication systems and their integration with satellite communication systems. This results in sharing frequencies allocated to satellite communication systems with terrestrial systems. As this can lead to interference between the incumbent and the upcoming service, coexistence studies are conducted. In the case of sharing satellite uplink frequencies with terrestrial communication systems, interference from base stations (BSs) is dominant. While there are methods to estimate the number of BSs that may be deployed, it is unclear where the BSs will be located. The BS locations play a pivotal role in interference calculation, as the values of link budget parameters are highly dependent on the longitude and latitude of interfering transmitters. This article presents an intelligent method which balances network capacity and coverage for simulating base stations (BSs) in coexistence studies. A realistic BS distribution is generated using weighted K‐means clustering (WKMC) algorithm and incorporating population density along with Haversine distance. The paper provides a case study of co‐frequency, co‐coverage interference in the satellite uplink in the C‐band to demonstrate the impact of BS distribution on the results of coexistence studies. This paper will find applications in upcoming frequency sharing and coexistence studies and the design of integrated satellite‐terrestrial communication networks.

Interference Analysis of NGSO Constellation to GEO Satellite Communication System Based on Spatio–Temporal Slices

The co-frequency interference (CFI) of the non-geostationary orbit (NGSO) constellation to the geostationary earth orbit (GEO) satellite internet of things (IoT) system is an nonnegligible problem. In this paper, based on the calculation method of the NGSO constellation satellite distribution state period, we propose a global characteristic method to analyze the CFI of the NGSO constellation to the GEO satellite IoT system by spatio-temporal slices. In order to analyze and evaluate the global characteristic and overall situation of interference, the temporal and spatial cut set of interference is established by fragmenting time and gridding space. The correctness of the proposed NGSO constellation satellite distribution state period is verified by taking the OneWeb constellation’s interference to the SINOSAT-5 satellite communication system as the simulation scenario. Furthermore, the global interference characteristic of the OneWeb constellation to the SINOSAT-5 satellite communication system is analyzed with the method mentioned above in the range of 80∘ 140∘E and 0∘ 50∘N. The results show that the analysis method can reflect the overall situation of the CFI of the NGSO constellation to the GEO satellite IoT system.

Design of reconfigurable multiplier-less filter structure based on IFIR for digital channelizer

The flexibility in frequency allocation is essential for high throughput satellites (HTS). The digital channelizer based transponder system has a crucial role in enhancing the performance of HTS. In this work, the design and implementation of a low computational complexity digital channelizer for HTS is proposed. The proposed reconfigurable filter structure for digital channelizer is to generate non-uniform and sharp transition width FIR filters for transponder of the satellite systems. The multipliers and group delay needed in the digital channelizer that employ the proposed structure are reduced when compared to FRM and traditional IFIR based digital channelizer. An example is used to illustrate the effectiveness of the proposed design. Results reveal that the proposed structure has a lower multiplier complexity than existing techniques. The proposed structure once implemented effectively, the power dissipation and hardware complexity are reduced. With the help of CSD, MOABC, and SIDC-CSE optimization, the filters used in this structure are made multiplier-less. Hence this structure is adaptable for the digital channelizer in the transponder of the satellite communication systems.

MSEC-D based energy consumption optimization strategy in satellite communication systems

In this paper, we consider a satellite communication system that consists of a source low earth orbit (SLEO) satellite, several relay low earth orbit (RLEO) satellites, and a destination ground station (GS). Under the assumption that the data can be split into different sizes of data flow while transmitted through the system in different time slots, a joint route selection and time-slot allocation problem are formulated. Considering the constraints on the availability of transmission links, conservation of data flow, and system resources, an optimization problem that minimizes the total system energy consumption is formulated. As the original optimization problem is NP-hard, which cannot be solved conveniently, we transform the problem to the maximum transmission rate route selection subproblem and energy-efficient resource allocation subproblem. To solve these subproblems, we propose two algorithms, namely the multi-time-expanding graph-based maximum transmission rate route selection (MTEG-R) algorithm and the minimum system energy consumption - Dijkstra (MSEC-D) algorithm. The proposed algorithms enable the determination of routes selection and time slots allocation for data transmission. Simulation results demonstrate the effectiveness of the proposed scheme.

Голографическая фотонная система фазовой синхронизации в спутниковом радиоканале

A necessary condition for the qualitative solution of telecommunication, infocommunication and navigation tasks in satellite communication systems is the presence of a high-precision synchronization system in satellite radio channels. It is indicated that the operation of the data exchange synchronization system in satellite radio channels is adversely affected by a number of external factors, such as, for example, the presence of the Doppler effect, errors in determining the relative speeds and directions of movement of artificial Earth satellites (ISS), the presence of a delay time of the transmitted signal due to significant distances between the nodes of the satellite communication network. The main disadvantages of modern synchronization systems used in satellite radio channels are given, and it is concluded that there is a relatively high probability of synchronism failure. It is indicated that the primary type of synchronization in a satellite radio channel is phase synchronization, the errors of which affect all subsequent types of synchronization (clock, frame and cycle). Analysis of the technical characteristics of modern phase synchronization systems in satellite radio channels allowed us to conclude that it is urgent to search for a new approach to the construction of these systems, which provides an increase in the speed and accuracy of their works. A possible way to solve this problem is the use of holographic photonics elements based on holographic sensing elements in measuring equipment that ensures the functioning and synchronization of satellite radio channels. The article solves the problem of constructing a holographic photonic phase synchronization system in a satellite radio channel. A technical solution is proposed to increase the speed, sensitivity and accuracy of the phase synchronization system by using a volumetric reflective Fourier hologram in the design of this system. A variant of the block diagram of the holographic photonic phase synchronization system is developed and the operation of this scheme is described. The constructive construction of optical elements of the developed block diagram in the form of electro-optical modulators and deflector optical systems is proposed. The individual features of the construction of these structural elements are indicated. The functional purpose of a volumetric reflective Fourier hologram in the design of a holographic photonic phase synchronization system is formulated. The regularities of changes in the parameters of optical fields in the holographic photonic elements of the phase synchronization system of a satellite radio channel are investigated. Concrete numerical examples demonstrate the possibility of providing high sensitivity and accuracy of a holographic photonic phase synchronization system.

Performance analysis of the packet-based PNT service in NGSO broadband satellite communication systems

Performance analysis of the packet-based PNT service in NGSO broadband satellite communication systems

Reconfigurable Digital Satellite-Borne Base Station Design and Virtual Function Fast Migration Algorithm.

A breakthrough in the technology for virtualizing satellite-borne networks and computing and storage resources can significantly increase the processing capacity and resource utilization efficiency of satellite-borne base stations in response to the development trend in multi-star and multi-system converged satellite internet iterative systems. The protocol processing function of traditional satellite communication systems is generally placed in the ground station system for processing, with poor flexibility and low efficiency. As a result, a reconfigurable digital satellite-borne base station architecture design is suggested, allowing for separation of the hardware and software of the satellite-borne base station and flexible programming and dynamic loading of the satellite-borne base station's functions by software. Meanwhile, a fast adaptive migration algorithm based on multi-dimensional environment awareness is proposed on top of the reconfigurable digital base station, and migration precomputation and real-time computation are added in order to realize rapid deployment of the digital base station system network. Simulation results demonstrate the effectiveness of the proposed algorithm in enhancing system stability and decreasing real-time calculation costs associated with system network migration under conditions of high dynamic changes for each network element in a star-loaded environment. In conclusion, a digital satellite-borne base station system that effectively addresses the issues of low flexibility and high dynamic changes of nodes in the resource-constrained satellite environment can be created by combining the adaptive migration algorithm and the reconfigurable digitized satellite-borne base station architecture.

A dual-band dual-polarized low-side-lobe transmitarray using independent amplitude and phase controllable elements

In this paper, a novel transmitarray (TA) element with independent control capability of amplitude and phase under dual-band dual-polarized operation is proposed. By changing the physical size of the TA element, the phase variation of the element can cover 360° at two bands. Moreover, the phase change of the frequency band is less than 30° when the phase of the other band is changed. Meanwhile, a higher maximal transmission amplitude can be maintained when varying the phase. Amplitude modulation is achieved by rotating the TA element. Utilizing the proposed TA element, a dual-band dual-linear polarization (LP) TA with low side lobe level (SLL) operating at 12.5 GHz and 14.25 GHz is designed. The SLL can be decreased by amplitude modulation of the elements. The measured peak gains of the proposed TA are 25.96 dBi and 25.89 dBi at 12.5 GHz and 14.25 GHz. In addition, the measured SLLs of the yoz/xoz planes are −22.4 dB/−22.4 dB and −22.5dB/−22.3 dB at 12.5 GHz and 14.25 GHz, respectively. The proposed TA shows good SLL performances and great application potential in satellite communication systems.

A gap Waveguide-Fed Dual-Circularly polarized antenna array for K-band applicaions

This article presents a 64-element dual-circularly polarized antenna array oriented by gap waveguide technology for K-Band applications. The proposed design is a 4 × 4 sub-array, each consisting of 2 × 2 patch antennas stimulated by a cavity through a cross-shaped slot. A gap waveguide-based feed layer is utilized to feed the cavity in two directions with a 90° phase difference. The main advantage of using gap waveguide technology is the capability to remove the need for electrical contact within the structure layers. Based on the obtained results, the proposed antenna array occupies a size of 11 × 11 × 1.4 cm3 and operates within the frequency range of 20.11 to 22.36 GHz. The array has an impedance bandwidth (IBW) of 10.6%, axial ratio bandwidth (ARBW) of 8.2%, and a maximum gain of 20 dBi at 21.25 GHz. Overall, the proposed antenna array can be used for satellite communication systems operating in the K-band.

Belief reliability index determination method based on group decision‐making

AbstractFor newly developing systems, the determination of the reliability index is an important task in the system demonstration process that determines both the system design goal and the verification requirement. However, due to the insufficient data at the beginning of the system life cycle, the problem of epistemic uncertainty cannot be ignored. Researchers have proposed several belief reliability metrics and analysis methods to quantify the epistemic uncertainty of a system, but to the best knowledge of the authors, no relevant studies have been performed on system reliability index determination. In this paper, we propose a belief reliability index determination method based on group decision‐making. Using a similar system‐based reliability index determination method, this method comprehensively considers the demands of users and the capabilities of contractors. In addition, the Delphi method and Hadamard multiplication convex combination are combined to effectively solve the epistemic uncertainty quantification problem. The Delphi method is used to find the conflicts caused by multi‐expert scoring, and the Hadamard multiplication convex combination can integrate the scoring matrix of all experts, which makes the results more reasonable. Finally, a Low‐Earth‐orbit (LEO) satellite communication system is used to verify the effectiveness of our belief reliability index determination method.

Ka-band flat panel circularly polarized antenna array for LEO satellite communication systems

In this paper, a high gain circularly-polarized antenna array with a flat panel structure for low Earth orbit (LEO) satellite communication systems is proposed. This new CP structure can efficiently achieve high directivity and can easily be integrated with beamforming ICs (BFIC) when designing an antenna module, resulting in a good candidate for Ka-band satellite communications. Furthermore, the proposed FPAA can easily be extended to a larger scale array from a base unit in a 2 × 2 sub-array structure. Each sub-array is configured by four high-gain planar segmented antenna (PSA) elements with a sequentially rotating arrangement, where a single 4-channel BFIC can drive CP radiation. Unlike previously reported PSA elements that have limited CP performance, the proposed PSA-CP configuration adopts additional conductors and ground-via structures to further improve the CP gain, axial-ratio (AR), and cross-polarization (XPD) characteristics. To verify the performance of the proposed PSA-CP, a 2 × 2 left-hand circular polarization (LHCP) sub-array was fabricated at 28 GHz and tested with a BFIC. The measured 10-dB impedance and 3-dB AR bandwidths of the proposed 2 × 2 array were 13.92% and 12.5%, respectively. In addition, the measured peak gain was 15.2 dBic at 28.5 GHz with an XPD level of less than 15 dB.

NOMA Assisted Semi-Grant-Free Transmission Scheme in Satellite Systems

This paper investigates the uplink semi-grant-free (SGF) transmission in satellite communication systems. Specifically, based on the available statistical channel state information, we first propose a non-orthogonal multiple access assisted SGF scheme, which enables many multi-antenna mobile terminals and one earth station to access the satellite network within the same resource block. Then, by assuming that the satellite channels undergo shadow-Rician distribution, we derive the closed-form throughput expression of the considered system, where the effect of imperfect successive interference cancelation is taken into account. Finally, simulation results validate the effectiveness of the theoretical analysis and the superiority of our proposed scheme. Besides, the influence of typical parameters on the system performance is also revealed.

High-Gain Dual-Band Aperture-Shared CP Patch Antenna With Wide AR Beamwidth for Satellite Navigation System

This paper presents a compact dual-band, high-gain, light-weight, circularly polarized (CP) microstrip patch antenna with wide axial ratio (AR) beamwidth for multiple satellite communication, positioning and navigation systems The antenna consists of a main dual-frequency coplanar metal frame radiator, a circular metal capacity-loaded radiator, and some coaxial feeding probes. Due to the use of air dielectric, the maximum right-hand circularly polarized gain of the antenna is up to 6.2 dBic in the lower bands and 6.3 dBic in the upper bands. By utilization of dual-frequency coplanar patch and metal capacity-loaded technology, the dimensions of the aperture-shared CP antenna are only 0.38 λ × 0.38 λ × 0.04 λ. To increase the 3-dB AR beamwidth, a novel vertically grounded shorting sheet is introduced. The 3-dB AR beamwidth ranges from −120° to 100° at 1.227 GHz and from −90° to 95° at 1.575 GHz. As a result, the proposed antenna is an excellent candidate for high gain, wide AR beamwidth and compact air dielectric antenna.

Legal Issues Pertaining to High Altitude Platform Station Implementation in Indonesia as an Archipelagic State

Information is a necessity for the interests of government, the economy, social culture, as well as defense and security in the era of industrial revolution 4.0. Since 1976, the Indonesian government has been working on developing a satellite communication system starting with the Palapa A1 Satellite, followed by its subsequent generations. However, this system has limitations, particularly in providing coverage to rural areas in Indonesia. To address this issue, the government has started the procurement of the Wahana Dirgantara Super or High-Altitude Platform Station (HAPS) in Indonesia. HAPS are stations positioned at altitudes of 20 to 50 km above the Earth's surface. Given Indonesia's geographical location, HAPS is seen as the most suitable solution as it utilizes non-ground terrestrial technology to improve information and communication technology coverage in rural areas. However, the location on which the HAPS is positioned might trigger new issues, particularly with regard to state sovereignty and disruption of flight traffic. The operation of HAPS also needs further consideration so that the protection of personal data in Indonesia will not be disrupted. This article employs normative juridical research as a methodology. The research collected and analyzed primary sources in the form of law, regulation, and policy at the national and regional levels, as well as secondary sources that are available in textbooks, journal articles, and website content. This article aims to explain the development of HAPS regulations based on international law and national law and to examine the legal issues related to the procurement of HAPS in Indonesia . At the end, this article suggests that it is necessary to regulate HAPS in Indonesia with reference to aviation safety, security, and liability issues as well as maintaining state sovereignty and ensuring personal data protection.

Impact Assessment of the Chirp Signal Frequency Change Rate on the Energy Secrecy and Noise Immunity

The article deals with the issues of noise immunity and energy secrecy of chirp signals. The purpose of the article is to study the rate of chirp signal frequency change and its influence on signal parameters, such as the envelope and spectrum of the signal, the degree of its energy secrecy and noise immunity. A study was made of the chirp signal frequency change rate influence on the amplitude spectrum of the transmitted signal. The study showed that an increase in the chirp signal frequency change rate leads to an increase in the slope control of the sawtooth voltage. In this case, the width of the amplitude spectrum changes in direct proportion to the change in the frequency band. Based on the results, the assumption was made about the positive effect of increasing the slope of the control signal on noise immunity and energy secrecy. The effect of the chirp signal frequency change rate on the degree of energy secrecy is studied by means of the author's method to estimate the energy of the transmitted symbol. The simulation results showed that the rate of change in the frequency of the chirp signal does not lead to a change in energy and does not affect the degree of energy secrecy. A study was made of the chirp signal frequency change rate influence on the noise immunity of the transmitted signal. It was proposed to investigate a real high-frequency chirp signal using the weighting method on a set of matched filters. The method made it possible to investigate the noise immunity of chirp signals with different parameters and compare the obtained data with the noise immunity of the GMSK signal of the Gonets-M satellite communication system. As a result, some regularities were found that allow us to evaluate the effect of the rate of change in the frequency of the chirp signal on its noise immunity. Comparison of GMSK and chirp signals made it possible to verify the effect of introducing chirp signals into satellite communication systems. As a result of the study, conclusions were drawn about the influence of the choice of chirp signal frequency change rate on noise immunity and energy secrecy.

Compact Wideband Groove Gap Waveguide Bandpass Filters Manufactured with 3D Printing and CNC Milling Techniques.

This paper presents for the first time a compact wideband bandpass filter in groove gap waveguide (GGW) technology. The structure is obtained by including metallic pins along the central part of the GGW bottom plate according to an n-order Chebyshev stepped impedance synthesis method. The bandpass response is achieved by combining the high-pass characteristic of the GGW and the low-pass behavior of the metallic pins, which act as impedance inverters. This simple structure together with the rigorous design technique allows for a reduction in the manufacturing complexity for the realization of high-performance filters. These capabilities are verified by designing a fifth-order GGW Chebyshev bandpass filter with a bandwidth BW = 3.7 GHz and return loss RL = 20 dB in the frequency range of the WR-75 standard, and by implementing it using computer numerical control (CNC) machining and three-dimensional (3D) printing techniques. Three prototypes have been manufactured: one using a computer numerical control (CNC) milling machine and two others by means of a stereolithography-based 3D printer and a photopolymer resin. One of the two resin-based prototypes has been metallized from a silver vacuum thermal evaporation deposition technique, while for the other a spray coating system has been used. The three prototypes have shown a good agreement between the measured and simulated S-parameters, with insertion losses better than IL = 1.2 dB. Reduced size and high-performance frequency responses with respect to other GGW bandpass filters were obtained. These wideband GGW filter prototypes could have a great potential for future emerging satellite communications systems.

МЕТОД РАЗЛИЧЕНИЯ КООРДИНАТНО-ИНФОРМАТИВНЫХ ПАРАМЕТРОВ АДДИТИВНЫХ КОМПОНЕНТНЫХ СИГНАЛОВ С СОВМЕЩЕНИЕМ НЕСУЩИХ ЧАСТОТ НА ОСНОВЕ СВЕРТКИ СПЕКТРА

The article presents a method for distinguishing the coordinate-informative parameters of additive component signals with the combination of carrier frequencies based on spectrum convolution in the geolocation of subscriber terminals of illegitimate users of the satellite repeater resource. A qualitative assessment of the probabilistic characteristics of the developed method was made, on the basis of which the boundary conditions for the applicability of this method were determined. The results obtained on the basis of simulation modeling can be used for geolocation of subscriber terminals of illegitimate users in satellite communication systems with the reuse of the frequency resource of the repeater satellite using the technology of combining carrier frequencies.