Search

Copyright of Scientia Iranica. Transaction D, Computer Science & Engineering & Electrical Engineering is the property of Scientia Iranica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The emerging demand for high-data-rate wireless communication systems and high-resolution radars, particularly in the millimeter-wave (mm-wave) spectrum, has captured significant attention within both the industrial and academic landscape. Recognized as the fundamental building block for satellite receivers, the low noise amplifier (LNA) plays a pivotal role in meeting these growing requirements. In Today's world a continuously increasing number of connected devices and resource-intensive digital content load to an incessant data being generated, transformed, and facilitated. In this paper, authors summarize the different technologies and techniques employed to design various LNAs with enhanced bandwidth, higher gain, low noise figure (NF), minimal power consumption, and less chip area. [ABSTRACT FROM AUTHOR]

The use of satellites to cover remote areas is a promising approach for increasing communication availability and reliability. The satellite resources, however, can be quite costly, and developing ways to optimize their usage is of great interest. Optimizing spectral efficiency while keeping the transmission error rate above a certain threshold represents one of the crucial aspects of resource optimization. This paper provides a novel strategy for adaptive coding and modulation (ACM) employment in land mobile satellite networks. The proposed solution incorporates machine learning techniques to predict channel state information and subsequently increase the overall spectral efficiency of the network. The Digital Video Broadcasting Satellite Second Generation (DVB-S2X) satellite protocol is considered as the use case, and by using the developed channel simulator, this paper performs an evaluation of the proposed machine learning solutions for channels with various characteristics, with a total of 90 different observed channels. The results show that a convolutional neural network with a modified loss function consistently achieves an improvement (over 100% in some scenarios) of spectral efficiency compared to the state-of-the-art ACM implementation while keeping the transmission error rate under 0.01 for single channel evaluation. When observing two channels, an improvement of more than 300% compared to the outdated information spectral efficiency was obtained in multiple scenarios, showing the effectiveness of the proposed approach and allowing optimization of the handover strategy in satellite networks that allow user-centric handover executions. [ABSTRACT FROM AUTHOR]

Summary: The mobile satellite communication (MSC) system represents a crucial means of communication, facilitating connections between mobile users and network control centres through satellites. Given the wireless nature of satellite communication, ensuring communication security is paramount for maintaining accountability. Key exchange and authentication (KEA) mechanisms are commonly employed to secure data transmitted over insecure or open channels. Developing a lattice‐based KEA protocol for MSC systems is imperative to achieve both quantum security and efficient communication. In this direction, Yadav et al. devised ring learning with an error‐based KEA technique to ensure a quantum‐safe environment. Their scheme is quantum‐safe and satisfies desirable security attributes but has low efficiency in computation. Moreover, we have identified that their scheme is susceptible to denial of service attack and session key established at user and NCC ends is different. To overcome the flaws of Yadav et al., we propose a lattice‐based KEA protocol for the MSC system to improve computation efficiency, and get resistance against key mismatch attack. The security analysis of the proposed scheme is presented in the random oracle model. Comparative study is also presented to observe advantages in computation efficiency. [ABSTRACT FROM AUTHOR]

The 5G new era implements standalone satellite communications that support wireless networking systems for future mobile communications by locating multiple satellites in low Earth orbit to provide global coverage of the entire Earth's surface. In this research, a newly found model of a satellite onboard transmitter using a uniform circular array multiple‐input multiple‐output antenna was designed to operate at a carrier frequency of 12 GHz and derived theoretical equations compared to the real‐time scenario. The integration of spread spectrum with multiple‐input multiple‐output antenna provides an advantage for higher capacity. It has a higher percentage of gain amplification on improving the transmission of electromagnetic power to meet the bandwidth requirement of center operating frequency, and this can transmit over a bandwidth of 1.28 GHz. The proposed satellite onboard transmitter model design aims to minimize the components, increase the speed of operations for higher bandwidth, and transmit large amounts of information to a large group of users. The transmitter can operate for the speed of 1.28 Gbps using pseudo‐random code, direct‐sequence spread spectrum, quadrature phase shift keying modulation, bandwidth separated in bands for 64 symbols using 128 Chebyshev‐type bandpass filter for transmission using 128‐element uniform circular array multiple‐input multiple‐output antenna. The satellite transmitter antenna produces a maximum gain of 14.526 dBi, and a maximum directivity of 17.986 dBi, and the efficiency at 12 GHz is 45.1% for the radiated power at 0.93 mW. This satellite transmitter will interconnect 5G wireless networks for the application of mobile communications complement terrestrial‐dependent networks. Key Points: Satellite onboard transmitter design at 12 GHz to integrate 5G wireless networking systemsImplementations of spread spectrum wave propagation using multiple‐input multiple‐output uniformly circular arrays antenna design techniqueMathematical derivation of equations for array factors uses 128 elements of arrays for the propagation of 64 symbols [ABSTRACT FROM AUTHOR]

In order to further improve the accurate detection signal, reduce interference between signals, this paper designs a new type of signal detection algorithm for satellite communication systems, using stochastic resonance technology improve the signal-to-noise ratio of the input signal, the signal by using energy detection, double threshold, accurate judgment. The first step in the conventional energy of double threshold detection, the second step into the energy detection method based on stochastic resonance detection process. The experimental results show that this algorithm under the condition of low SNR signals effectively detect, promoted the whole satellite communication system performance. [ABSTRACT FROM AUTHOR]

This article presents an 8×8 Multiple-Input Multiple-Output (MIMO) antenna system that operates in two frequency bands: 3.4–3.8 GHz and 10.5–14.0 GHz. The core element of this antenna system is a rectangular patch with a line slot. To assess the diversity performance of this MIMO antenna, various parameters like S-Parameters, Envelope Correlation Coefficient (ECC), Mean Effective Gain (MEG), Channel Capacity Loss (CCL), Total Active Reflection Coefficient (TARC), and Channel Capacity (CC) were used. The study demonstrates a strong alignment between measurement and simulation results. The article thoroughly analyzes the simulated and measured performances of the lower band (LB) (3.4–3.8 GHz) and upper band (UB) (10.5–14.0 GHz). In the LB, the measured values for parameters such as reflection coefficient, mutual coupling coefficient, TARC, total efficiency, ECC, MEGi-MEGj, CCL, and CC all surpass or equal specific benchmarks. Specifically, these values are better than −6 dB, 10 dB, −11 dB, 56%, 0.15, 0.83 dB, 0.275 bps/Hz, and 38 bps/Hz, respectively. For the UB, the values are also quite favorable, exceeding or closely matching key criteria: −6 dB, 10 dB, −5 dB, 40%, 0.2, 1.6 dB, 0.55 bps/Hz, and 33.6 bps/Hz. These findings suggest that the intended MIMO antenna meets the necessary conditions for both the LB and UB regions. As a result, it appears to be a promising choice for applications in 5G mobile networks and satellite communications, including Direct Broadcast Satellite (DBS) and Fixed Satellite Services (FSS). [ABSTRACT FROM AUTHOR]

Summary: The mobile satellite communication (MSC) system is a vital communication method in which mobile users and network control centers connect via satellites. Since the satellite's communication is wireless, communication security is a critical factor to ensure accountable communication. Key exchange and authentication (KEA) mechanism is widely used to achieve data security for data transmitted in an insecure or open channel. Different authentication systems are suggested in the last many years to establish safe communication, whereas most existing security protocols are based on factorization or discrete logarithm. However, these systems are no longer reliable by Shor's algorithm as any discrete logarithm and factorization can be resolved in polynomial time on quantum computers. Thus, developing a quantum secure KEA protocol for MSC systems is necessary. In this direction, recently a ring learning with an error‐based KEA technique is proposed to ensure a quantum‐safe environment. This scheme is quantum‐safe and satisfies desirable security attributes but has low efficiency in computation and communication. Moreover, establishing a secure session requires six communications among involved entities. As a result, replay attack detection at an early stage is not possible for the central authority (server), which could delay the server response, and the adversary gets the advantage of drawing a denial of service scenario for authorized entities. We propose a lattice‐based KEA protocol for the MSC system to improve computation, communication efficiency, and early‐stage replay attack detection. The security analysis of the proposed scheme is presented in the random oracle model. Calculation of performance is also presented to observe advantages in computation and communication overhead. [ABSTRACT FROM AUTHOR]

A shared‐aperture 2‐bit coding metasurface for simultaneously and independently manipulating space wave and surface wave is proposed in this paper. When the proposed coding metasurface is expected to modulate space wave, the unit cells can control the reflection phase. The reflected wave becomes various according to the specific coding sequence. When the proposed coding metasurface acts as spoof surface plasmon polaritons (SSPP) transmission line, the unit cells can modulate the surface impedance. With periodic modulation to the surface impedance, electromagnetic wave can be radiated into free space and the radiation beam scans as frequency changes. Space wave modulator works at 22.5 GHz, while the surface wave modulator works during the frequency range of 6.5–11.4 GHz. The total scanning angle of the radiated beam of surface wave modulator covers from −54° to 52°, with an average gain of 10.64 dBi. Simultaneous manipulation of both space wave and surface wave by a single metasurface makes the proposed device promising in the new radar and satellite communication systems with compact requirement. [ABSTRACT FROM AUTHOR]

Modern stealth application systems require integrated meta-devices to operate effectively and have gained significant attention recently. This research paper proposes a 1-bit coding metasurface (CM) design. The fundamental component of the proposed CM is integrated to convert linearly polarized incoming electromagnetic waves into their orthogonal counterpart within frequency bands of 12.37–13.03 GHz and 18.96–32.37 GHz, achieving a polarization conversion ratio exceeding 99%. Furthermore, it enables linear-to-circular polarization conversion from 11.80 to 12.29, 13.17 to 18.44, and 33.33 to 40.35 GHz. A second element is produced by rotating a fundamental component by 90°, introducing a phase difference of π (pi) between them. Both elements are arranged in an array using a random aperiodic coding sequence to create a 1-bit CM for reducing the radar cross-section (RCS). The planar structure achieved over 10 dB RCS reduction for polarized waves in the frequency bands of 13.1–13.8 GHz and 20.4–30.9 GHz. A prototype was fabricated and tested, with the experimental results showing a good agreement with the simulated outcomes. The proposed design holds potential applications in radar systems, reflector antennas, stealth technologies, and satellite communication. [ABSTRACT FROM AUTHOR]

In this paper, a wideband Vivaldi phased array with double band-notched performance for radio astronomy is proposed. To address the issues of radio frequency interference from 5 G mobile communication (4.8–5 GHz) and C-band satellite communication (5.9–6.5 GHz) in radio astronomy system, the hairpin ring resonator (HRR), defected ground structure and λ/2 shorted-circuit stub are utilized together to realize the double notched bands with different bandwidth. The resonate mechanism of the proposed HRR is widely investigated, which exhibits independent and controllable resonances. Meanwhile, λ/2 shorted-circuited stub is adopted for the band notched performance. As the current on the stub is induced along the shorted via to the ground, without participating in radiation, thus the notched frequency is not affected by the scan angle. With these novel and dedicated design, the proposed phased array performs double band-notched performance with high skirt selectivity and deep suppression, within the notched band the maximum rejection level is better than 22.7 dB. This is the first work to implement double notched bands in phased array to the authors' best knowledge. Finally, a prototype composed of 8 × 9 elements is fabricated and measured. The measurements agree well with the simulated ones. [ABSTRACT FROM AUTHOR]

Recently, the low earth orbit (LEO) mega-constellation faces serious time-varying interferences due to spectrum sharing, dense deployment, and high mobility. Therefore, it is important to study the interference avoidance techniques for the dense LEO satellite system. In this paper, the interference situational aware beam pointing optimization technique is proposed. Firstly, the angle of departure (AoD) and angle of arrival (AoA) of the interfering links are obtained to represent the time-varying interference. Then, the interference avoidance problem for dense LEO satellite systems is modeled as a non-convex optimization problem, and a particle swarm optimization (PSO) based method is proposed to obtain the optimal beam pointing of the user terminal (UT). Simulations show that the relative error of the mean signal-to-interference plus noise ratio (SINR) obtained by the proposed method is 0.51 %, so the co-channel interference can be effectively mitigated for the dense LEO satellite communication system. [ABSTRACT FROM AUTHOR]

This letter presents a Ka‐band low‐cost microstrip line phase shifter based on liquid crystal (LC) technology. Furthermore, a sum‐difference beamforming antenna array based on the LC phase shifter is designed. The phase shifter is composed of two coaxial connectors, a metal base, an intermediate dielectric layer, a gradient metal sheet and a top glass layer. The simulated results show that a nearly 360° phase shift coverage can be achieved with the effective permittivity of LC varying from 2.5 to 3.5. The sum‐difference beam antenna array is composed of a circulator, a sum‐difference network, a one‐to‐eight power‐division network, eight liquid crystal phase shifters, and a serious fed antenna array. The simulation results show that the antenna array can achieve sum‐difference beam scanning range of ±30°. A prototype of LC phase shifter is fabricated and tested. The results show that the designed LC phase shifter can achieve a 360° phase coverage by applying a direct current (DC) voltage ranging from 0 to 12 V. Compared to traditional phase shifters, the proposed design offers a simple structure at a lower cost. When applied in the design of a sum‐difference beam antenna array, it can reduce the producing cost and enable integrated design. [ABSTRACT FROM AUTHOR]

In this paper, a dual-band asymmetric transmission metasurface for linearly polarized wave is designed, analyzed, and verified experimentally for operation in S- and C-bands. The metasurface is established by a bi-anisotropy structure with three metallic layers separated by dielectric spacers. Symmetric rectangular split-ring resonators are adopted in the top and bottom metallic layers while modified metal strip with stepped widths is utilized in the middle. Both asymmetric transmission capability and operation bandwidth are remarkably improved. According to simulation, the design yields an asymmetric transmission parameter above 0.8 within two operation bands: 2.53–2.56 and 3.80–4.71 GHz, fractional bandwidths of 1.18% and 21.39% can be deduced, respectively. The oblique incidence property is further analyzed, which demonstrates robustness response to incidence up to 50°. Two operation bands, 2.53–2.56 and 3.87–4.78 GHz, are also validated through measurement. The corresponding bandwidths 1.18% and 21.04% show tiny discrepancy related to simulated results, which validate the reliability of the design. Comparisons with other recent published results show that this structure provides relative low profile, wider operation band with high asymmetric transmission efficiency. The proposed metasurface could be applied for electromagnetic interference suppression and polarization control for modern radar and satellite communication systems and can be scaled to operate for higher frequencies with considerable bandwidth and efficiency. [ABSTRACT FROM AUTHOR]

This paper proposes a design of a 38 GHz Low Noise Amplifier (LNA) that uses a three-stage common source inductive degeneration topology with a gain of 27 dB and noise figure of 1.78 dB using 0.1 µm GaAs pHEMT as an active device. The novelty of the design is the usage of inductive load in series with the resistor instead of resistive load, resulting in higher gain performance. A recent pp1010 active device of WIN foundry was explored for this LNA design at the Q band. The high transition frequency offered by this technology succeeded in obtaining competitive results with a minimum number of cells. The designed LNA obtained the lowest noise compared to other recently published LNA designs at the Q band. The total power consumption of this design is 57 mW. [ABSTRACT FROM AUTHOR]

Copyright of Space-Integrated-Ground Information Networks is the property of Beijing Xintong Media Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The paper proposes a antenna design that can serve as a comprehensive solution for covering 4G/5G cellular bands 850-1000 MHz, 1900 MHz, 2100-2700 MHz, 3300-4900 MHz, Global Navigation Satellite System (GNSS-L1) Band 1.56 GHz{1.61 GHz, V2X 5.850-5.925 GHz band which are appropriate for the use in automobile applications. The proposed antenna is designed with respective polarization for cellular and GNSS applications, where the cellular antenna is linearly polarized, and the GNSS antenna is circularly polarized by chamfering the square patch. FR4 substrate material is used to construct the Long Term Evolution/4G (LTE) antenna. The optimization of the antennas ensures minimal coupling between them. The cellular antenna is designed using a hexagonal base with a modified ground plane to achieve the required cellular bands using a monopole (fractal design). The GNSS antenna is implemented on a PVC (Poly Vinyl Chloride) substrate. The measured results of S11 parameter show that the proposed design covers all the required 4G/5G bands with minimum S11 of -10 dB and a radiation pattern in the theta 60-90° range for cellular antenna, while the GNSS antenna has a zenith radiation pattern with axial ratio of < 3 dB for theta angles in the 0-30° range and a mutual coupling of -15 dB. The fabricated antenna was measured to validate the simulated results of re ection coefficient. All things considered, the suggested design is perfect for automobile applications to satisfy both satellite and mobile communication needs. [ABSTRACT FROM AUTHOR]

Microstrip antenna technology has gained significant momentum in recent times, finding widespread applications in mobile and satellite communications. These antennas offer advantages such as cost-effectiveness, low profile, and easy fabrication. However, one of the limitations of microstrip antennas is their limited bandwidth utilization. To address this drawback, a proposed methodology has been introduced to enhance the bandwidth utilization factor and overcome this limitation. The proposed method involves the design of a microstrip rectangular patch antenna using co-planar parasitic rod elements and substrate integrating feeding line technique. This approach aims to improve various aspects of the antenna's performance, including bandwidth enhancement, front-to-back ratio improvement, loss reduction, increased quality factor, and higher power handling capability. Through the proposed method, the bandwidth ratio is significantly increased from 4 to 18%, demonstrating superior results compared to existing approaches. The simulation and 3D plot results were obtained using Ansoft HFSS (High-Frequency Structure Simulator) software, confirming the effectiveness of the proposed methodology in achieving efficient bandwidth utilization and overall antenna performance improvements. [ABSTRACT FROM AUTHOR]

Thanks to its capability of providing seamless massive access and extended coverage, satellite communication has been envisioned as a promising complementary part of the future 6G network. Due to the large satellite-to-ground propagation loss, noise mitigation is one of the most important considerations for implementing key interface technologies on boarding a satellite, e.g., random access (RA). This paper aims at developing an effective preamble detection method with noise suppression for 5G-ntegrated satellite RA systems. Specifically, according to the satellite ephemeris and user equipment location, we first perform the pre-compensation of timing and frequency offset before preamble transmission to determine all the possible correlation peak positions in advance. By leveraging the advantage of the wavelet transform in signal-to-noise separation, we further design a novel detection framework based on wavelet denoising, which can efficiently reconstruct preamble signature from the noisy power delay profile. Simulation results validate the feasibility of the proposed method, and show that our method can achieve a notably improved detection performance under extremely low signal-to-noise ratio conditions, in comparison with the conventional one. [ABSTRACT FROM AUTHOR]

This work developed a modified U‐Net model (a convolutional network architecture) to predict global Total Electron Content (TEC) maps. The input includes the current global TEC map, the current F10.7, the time history of the Interplanetary Magnetic Field Bz and SYM‐H in the previous 4 days, the Hour of Day, and the Day of Year. The output is the global TEC map several hours or several days ahead. The modified U‐Net was trained and validated on a brand new TEC database, the VISTA (Video Imputation with SoftImpute, Temporal smoothing and Auxiliary data) TEC database. The VISTA TEC maps can reveal important large‐scale TEC structures and preserve mesoscale structures simultaneously. Taking advantage of the new neural network and the new database, our model achieves an root of the mean squared error from 1.2 TECU to 2.4 TECU as the prediction horizon increases from 1 hr to 7 days. In addition, the model could reveal multiscale structures in the predicted TEC maps. Plain Language Summary: The ionospheric Total Electron Content (TEC) is the total number of electrons present along a path between a radio transmitter and a receiver. An accurate prediction of global ionospheric TEC is important for Global Navigation Satellite System positioning, navigation, and timing services, high‐frequency radio communications, and other satellite communications. In this work, a new convolutional neural network was developed to forecast global TEC maps. Our new model not only has promising performance compared with state‐of‐the‐art TEC prediction models but also includes multiscale structures. Our model can greatly mitigate the impacts of ionospheric space weather on our technological society. Key Points: A modified U‐Net model was developed to forecast global Total Electron Content (TEC) mapsThe new model was trained and validated with the Video Imputation with SoftImpute, Temporal smoothing and Auxiliary data TEC databaseThe new model can reproduce multi‐scale TEC structures [ABSTRACT FROM AUTHOR]

Summary: A hexagonal shaped circularly polarized (CP) wideband slot antenna using multiple stubs has been proposed and investigated. A hexagonal slot is created in the ground plane with tapered sections improving the impedance matching. Two radiators are incorporated in the structure, which is responsible for generating orthogonal degenerate modes; hence, CP radiation is achieved for the proposed antenna. For enhancing the gain of antenna, one radiator is directly connected to feed line and another one embedded in the ground plane. An inverted L‐shaped arm is inserted in the slot to enhance and tune the circular polarized behavior. The presented radiator have input reflection coefficient ranges from 5.67 to 8.50 GHz (39.97%) and axial ratio bandwidth (ARBW) of 5.60–8.50 GHz (41.13%). The proposed antenna provides overlapping bandwidths of 5.67–8.50 GHz (39.97%) having average gains of 5.25 dBi within the entire frequency bands. The presented antenna is exceptionally good for the application of mobile and satellite communications. [ABSTRACT FROM AUTHOR]

With the rapid growth of social economy, the requirements for resource utilization are becoming higher and higher. How to effectively solve the problem of energy shortage has become a hot topic. However, there are still many deficiencies in the current resource scheduling algorithm. For example, for different types of satellites with different needs and requirements, their performance indicators are different, and in the satellite communication system, the interaction between multiple nodes needs to be considered. Therefore, this paper studies the artificial intelligence algorithm, and proposes an improved particle complementary scheduling strategy for a single user in view of the shortcomings of the existing particle swarm optimization (PSO) algorithm. On this basis, this paper applies this method to evaluate the system performance and verify its effectiveness. The verification results show that the utilization efficiency of the satellite communication system resource scheduling algorithm is above 93%. [ABSTRACT FROM AUTHOR]

Summary: To address the problem that Ka‐band satellite communication signal transmission is easily affected by rainfall and terminal environment, combining the characteristics of high‐speed movement of LEO satellites and the wave propagation characteristics of satellite‐ground links, this paper establishes a Markov synthesis model of four‐state satellite channels based on Ka‐band that integrates rainfall attenuation and terminal shadow attenuation, and a scheme for adaptive coding and modulation selection based on the DVB‐S2 standard is proposed. Based on this, a rainfall fading probability density function (PDF) based on the satellite elevation angle variation is derived, and a more efficient and streamlined set of modulation and coding(MODCOD) is obtained through simulations and calculations. The simulation results show that the proposed scheme not only effectively solves the problem of severe fading of the transmission signal due to rainfall, ground movement environment and satellite mobility but also significantly reduces the system complexity of the original DVB‐S2 standard scheme with little loss of efficiency. [ABSTRACT FROM AUTHOR]

The paper presents a novel miniaturized (1.2 λ0 × 0.5 λ0 × 0.026 λ0) frequency reconfigurable travelling wave antenna (TWA) operating at 8–12 GHz band. The antenna uses PIN diodes arranged in a novel configuration to produce frequency reconfigurability and operates at single frequency bands of 8.5, 9, 9.35, 9.9, 10.45 and 11 GHz with an average bandwidth of 1 GHz based on different switch configurations. The proposed antenna demonstrates an efficiency>80% for the operating frequency in different stations while maintaining a stable average gain of 8.5 dBi. The antenna's compact nature and high gain make it suitable for several applications within modern satellite communication devices and radar systems. The proposed antenna is designed and tested for its conformality using CST Microwave-Studio. The proposed design is further verified with a fabricated prototype measured in an anechoic chamber, agreeing well with the simulated results. [ABSTRACT FROM AUTHOR]

This publication proposes a fabricated multiple input multiple output (MIMO) antenna geometry of multiple dipole arrays and its numerical findings through simulations. The role that antenna resonators have in antenna performance is explored. The antenna's characteristics have been studied, such as its return loss, peak gain, bandwidth, polar plot, and electric field distribution. The proposed antennas described in the study can produce three to seven resonance bands, making them suitable for multiband, wideband, and short-band settings. With the radiator placed in a mirror image, a gain of ~ 27 dBi is seen in the design. This layout is successful at achieving a bandwidth of 0.98 GHz. The maximum bandwidth of 7.44 GHz was achieved in antenna design when the antenna was inverted and mounted vertically. We measure a peak gain of ~ 4.1 dBi for this antenna configuration. In addition, the suggested antenna may provide a multi-beam antenna radiation pattern, capable of producing both a narrow beam of 10° and a wide beam of 250°. The proposed antenna has numerous potential uses; the study's findings can be applied to various wireless networking and telecommunications technologies, including Zigbee, WiFi, WiMAX, satellite, and 5G. [ABSTRACT FROM AUTHOR]

With the rapid growth of data traffic, low earth orbit (LEO) satellite communication networks have gradually ushered in a new trend of development due to its advantages of low latency, wide coverage, and high capacity. However, as a result of the limited on-board resources and rapidly changing traffic demand, it is increasingly urgent to design an efficient resource-allocation scheme to satisfy the traffic demand. In this paper, we propose two resource allocation algorithms in the multi-satellite system based on beam-hopping technology. In the offline case, it is assumed that the channel gains in all time-slots are known in advance, and we propose a heuristic algorithm to allocate time and frequency resources, and a successive convex approximation (SCA) algorithm to allocate power resources. In the online case, it is assumed that only the instant channel gains information is known; therefore, we apply the dynamic programming (DP) algorithm to maximize the system throughput. The simulation results prove that the proposed resource-allocation algorithms based on beam-hopping technology have better performance than the traditional average allocation method, and the online algorithm has acceptable performance loss compared with the offline algorithm. [ABSTRACT FROM AUTHOR]

This paper proposes a hexagonal meander-shaped wideband electronically reconfigurable transmitarray (HMRTA) at Ku band for satellite communications and radar applications. The proposed transmitarray offers high gain, low profile, and wideband characteristics with beam-scanning and beam-forming features. The cascaded structure is a low-profile and compact transmitarray. The transmitter (Tx) layer has an angular hexagonal patch with a meandered shape and resonating parasitic patches to enhance the bandwidth. The receiver (Rx) layer comprises a two-part hexagonal receiver patch and a dual ring impedance-matching receiver layer. The current reversal phenomena have executed the 180° phase shift by integrating two diodes in opposite directions. The measured results of a unit cell achieve a minimum insertion loss of 0.86 dB and 0.92 dB for state I and state II. The maximum insertion loss is 2.58 dB from 14.12 GHz to 18.02 GHz and is about 24.83% at 16.5 GHz. The full-wave simulations of a 20 × 20 space-fed reconfigurable transmitarray were performed. Good radiation patterns at all scanning angles of two principal planes are achieved, and the cross-polarization level remains less than −20 dB. The simulated 3 dB gain fluctuation bandwidth of the array is 15.85~18.35 GHz, and the wideband characteristics are verified. The simulation results show that the array can perform beam scanning ±60° in the elevation (y-z) plane and obtain the beam-scanning characteristics for ±60° in the Azimuth (x-z) plane. [ABSTRACT FROM AUTHOR]

Simple Summary: Animal monitoring through electronic methods requires a continuous Internet connection to guarantee timely human intervention. Internet access depends on the coverage of the communications network, which does not always exist in agricultural and rural environments, as is the case on the slopes of the Douro River. This work documents the optimization process of a monitoring and alarm generation system and its integration with a satellite communications system to guarantee alarm messages are sent in places without Internet access coverage. The results functionally demonstrated the viability of the solution for the timely delivery of alarms with an acceptable expected operating cost. The application of IoT-based methods to support pastoralism allows the smart optimization of livestock operations and improves the efficiency of the activity. The use of autonomous animal control mechanisms frees the shepherd to carry out other tasks. However, human intervention is still needed in cases such as system failure, the bad or unpredicted behavior of the animals, or even in cases of danger, the welfare of the animal. This study documents the enhancement of an alarm generation system, initially developed within the scope of the SheepIT project, to monitor animal behavior and equipment, which warns the human operator of the occurrence of undesirable events that require intervention. Special attention was given to the use of case scenarios in places without Internet access, such as rural areas. Therefore, the system was integrated with a satellite interface, as a way of guaranteeing the timely delivery of the alarm messages. To ensure an acceptable operating cost, the system was further optimized in terms of message encoding, considering the cost of this type of communication. This study assessed the overall performance of the system, evaluated its scalability, and compared the efficiency gains from the optimization, as well as the performance of the satellite link. [ABSTRACT FROM AUTHOR]

Cognitive satellite communication (SatCom) is rapidly emerging as a promising technology to overcome the scarcity of the exclusive licensed band model in order to fulfill the increasing demand for high data rate services. The paper addresses power allocation methods for multi-operator multi-beam uplink satellite communication systems co-existing with a Ka-band terrestrial network, using cognitive radio paradigm. Such a scenario is especially challenging because of (i) the coexisting multiple SatCom operators over the cognitive band need to coordinate the use of their resources under limited inter-operator information exchange, and (ii) nonlinear onboard high power amplifier (HPA) which leads to nonlinear interference between users and beams. In order to tackle the first challenge, we propose distributed power allocation algorithms including the standard Alternate Direction Multiplier Method (ADMM); Regarding the HPA nonlinear impairment, we propose nonlinear-aware power allocation based on Signomial Programming. The proposed solutions outperform state-of-the-art in both cases. [ABSTRACT FROM AUTHOR]

The fifth‐generation (5G) technology is seen to be a solution for developing countries to improve their quality of services in terms of transportation, education, health, agriculture, and other fields, thereby holding the promises of economic transformation by improving productivity and the quality of life. The paper considers some of the challenges that face operators, investors, and providers when planning to introduce 5G technology to developing countries. The main focus of this paper is the 5G transport network, in particular, the backhaul network. The 5G transport network architectural options and scenarios are discussed based on several standards and previous studies, the problems of existing infrastructures of developing countries are investigated, and new proposed technologies that may help to address those challenges are considered. [ABSTRACT FROM AUTHOR]

Copyright of Space-Integrated-Ground Information Networks is the property of Beijing Xintong Media Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the continuous development of mobile communication and satellite navigation technologies, the positioning requirements of 5G smart communication base stations are becoming higher and higher. With the opening of GNSS raw observation data, research on the positioning of a 5G smart communication base station has become a research hotspot in the surveying and mapping disciplines. In this paper, based on the GNSS observation data of the 5G smart communication base station, the quality of the original GNSS observation data of the 5G smart communication base station is studied and analyzed. A method based on Doppler smoothing pseudorange solves the problem that the original pseudorange observation values of the 5G smart communication base station are noisy and prone to multipath errors due to the limitations of the base station chips and processes, which makes the traditional data processing methods unable to meet the demand for higher accuracy positioning. This method uses Doppler observations to smooth the pseudorange and determines the Doppler smoothing strategy and closure values to improve the data quality. The experimental data show that Doppler smoothing pseudorange can improve data quality and positioning accuracy by 67.9% in the E direction, 64.8% in the N direction, and 65.5% in the U direction. The future world will develop in the direction of intelligence, and the wireless network 5G technology used to support the construction of this intelligent system will become the core driver for the development of a leading intelligent society. 5G network signals have higher reliability and lower latency and can meet the specific needs of smart manufacturing, autonomous driving, and other industrial applications. This new base station product can meet the construction needs of future 5G base stations, adapt to the future intensive, miniaturized, intelligent station construction mode, and realize safe and fast station construction, providing the necessary hardware support for 5G network coverage. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

How to extend the HARQ technique to made it suitabled for LEO satellite communication network was explored. First the traditional HARQ technology was expounded. Based on this, the HARQ scheme based on low density parity check code (LDPC) and the HARQ scheme based on message group check code (BCC) were studied respectively, the performance of the schemes was analyzed through simulation. Finally, suitable feedback schemes were analyzed for the retransmission units in the HARQ retransmission mechanism, which provided some reference for the research of HARQ technology in LEO satellite communication networks. [ABSTRACT FROM AUTHOR]

Because of the difference between satellite-ground link and ground propagation loss characteristics, the spectrum efficiency index of satellite communication system is far lower than that of terrestrial cellular system in the same period. It is of utility to improve spectral efficiency by realizing efficient space division multiplexing with multi-beam antennas. The adaptive beamforming and doppler frequency off set compensation scheme in the LEO multi-beam atellite communication scenario was studied. Firstly, a low-complexity hybrid beamforming scheme was designed. Then, aim at the doppler frequency shifts were different between beams due to their pitch angles, a doppler frequency off set pre-compensation scheme for multi-beam systems was proposed. Finally, the effectiveness of the algorithm was verified by MATLAB simulation analysis. [ABSTRACT FROM AUTHOR]

Reflectarrays (RAs) have been attracting considerable interest in recent years due to their appealing features, in particular, the possibility of realizing pencil-beam radiation patterns, as in the phased arrays, but without the necessity of incorporating the feeding networks. These characteristics make them attractive solutions, among others, for satellite communications or mobile radar antennas. Notwithstanding, available microstrip implementations are inherently narrow-band and heavily affected by conductor and surface wave losses. RAs based on grounded dielectric layers offer improved performance and flexibility in terms of shaping the phase reflection response. In either case, a large number of variables (induced by the need for independent adjustment of individual unit cell geometries) and the necessity of handling several requirements make the design process of reflectarrays a challenging endeavor. In particular, RA optimization is extremely expensive when conducted at the level of electromagnetic (EM) simulation models, otherwise necessary to ensure reliability. A practical solution is a surrogate-assisted design with the metamodels constructed for the RA unit elements. Unfortunately, conventional modeling methods require large numbers of training data samples to render accurate surrogates, which turns detrimental to the optimization process efficiency. This work proposes an alternative approach with the unit element representations constructed using deep learning with automated adjustment of the model architecture. As a result, design-ready surrogates can be constructed using only a few hundred samples, and the total RA optimization cost is reduced to only a handful of equivalent EM analyses of the entire array. Our approach is validated using an RA incorporating 3-D pyramidal-shaped elements and favorably compared to benchmark techniques. Experimental verification of the obtained design is discussed as well. [ABSTRACT FROM AUTHOR]

In this paper, we propose a compact and highly isolated four-port ultra-wideband MIMO antenna. The antenna elements achieve broadband characteristics by etching a metamaterial structure on the radiating patch and stepping the coplanar waveguide feed. The test results show that the unit antenna can operate from 1.8 GHz to 16.38 GHz with an absolute bandwidth of 14.58 GHz and a relative bandwidth of 160.4% with good radiation properties and gain. After that, a compact four-cell ultra-wideband MIMO antenna is designed by using polarization diversity technology with an overall size of 51.2 mm × 51.2 mm × 1.524 mm. The MIMO antenna can operate from 1 GHz to 17 GHz with an absolute bandwidth of 16 GHz and a relative bandwidth of 177.78%. To reduce the coupling between cells, four angled slits are etched on the common ground to improve the isolation of the MIMO antennas to 27.8 dB. The performance parameters of the proposed MIMO antennas are further validated through simulation analysis and measurements. Moreover, the diversity properties of MIMO antennas are analyzed in detail, demonstrating the applicability of the proposed antennas in UWB communication systems, which can also be used for satellite mobile communications and satellite fixed communication services. [ABSTRACT FROM AUTHOR]

A miniaturized Circularly Polarized Microstrip Patch Antenna with fractal Defected Ground Structure (DGS) is proposed. For the purpose of realizing Circularly Polarized radiation, two square notches and an asymmetric length of two rectangular slots that are perpendicular to one another are printed on square and hexagonal shaped patches, respectively. The antenna size is decreased and circular polarization is achieved by employing koch snowflake-shaped Defected Ground Structure. The proposed antenna is appropriate for use in India with mobile satellite communications. The suggested antennas resonate at 1.5GHz. Axial Ratio, VSWR, Radiation Efficiency, FBR (Front to Back Ratio), and Area of Patch are the metrics used to evaluate the antenna performance to that of the existing antenna. It is observed that the proposed structures are better in many aspects mentioned above. The antennas are simulated using HFSS v.2017.2 software. [ABSTRACT FROM AUTHOR]

In the global maritime industry, ineffective and ambiguous communication often is a main or contributing cause of shipping accidents. Nevertheless, because of the limited availability of authentic data, quantitative studies in maritime communication are rare. In addition, previous studies seem to have used the Standard Marine Communication Phrases as the prescriptive maritime communication standard, thus overlooking the superordinate role of the Manual for Use by the Maritime Mobile and Maritime Mobile-Satellite Services published by the International Telecommunication Union. Therefore, this paper uses a specialised spoken corpus of authentic routine ship-shore communication to quantify the rate of compliance of authentic routine ship-shore communication with the standard protocol of communication for ships and shore services as the key communication agents in the provision of navigational safety and efficiency. The findings show that authentic routine ship-shore communication still significantly deviates from the standard protocol of communication. In addition, the rate of compliance varies across the analysed elements and between the two communication agents examined in this study. Finally, the results indicate the need for harmonisation between the documents that define the standard protocol of communication. - The study is based on a specialised spoken corpus of authentic routine ship-shore communication. - Routine ship-shore communication still significantly deviates from the standard protocol of communication. - Shore services are not more observant of the standard protocol of communication than ships. - The efficiency and clarity of routine ship-shore communication largely relies on the predictability of communication topics. - Harmonisation is necessary between the documents that define the standard protocol of communication. [ABSTRACT FROM AUTHOR]